Frank Erskine wrote:
On Sat, 3 Dec 2005 14:23:58 -0500, "Daniel J. Stern"
wrote:

On Sat, 3 Dec 2005, David Lee wrote:

AFAIK US supply is normally +/- 120V

Yes.

with 240V available across both "phases" used for cookers etc.

Yes.

I believe that US codes allow for double kitchen sockets to be wired
with +120 and -120V so that 240V appliances can be plugged in using a
special connector that uses both outlets.

Interesting. If that's true, I've never ever seen such an installation
before. Stoves, ovens, clothes dryers and other such 240v appliances
generally have their own dedicated high-voltage outlet completely
different in configuration to the regular 120v outlets.

I'd always imagined a typical USAian domestic supply to be a sort of
two phase 117 + 117V feed, rather like a 234V centre-tapped supply;
most appliances using 117V, with the option of "high-power" stuff
utilising the 234V.

The US National Electrical Code (NEC) now requires cookers and other
230V high-power appliances to have a single 4-pin socket, plug and 4-way
cable: the two 115V phases, neutral and protective ground. In most
appliances the main load is connected directly phase-to-phase, and
neutral is only used as a return for low-current 115V auxiliaries (fan
motors, oven lights etc). If neutral isn't needed, I believe a
three-wire cable can be used (the two phases and ground) but still a
4-pin connector.

There are bound to be permitted exceptions in older installations, but
that's my understanding of the requirements for a clean new
installation.

Protective grounding (earthing) is pretty much the same as over here.
The ground wiring should be bonded to neutral only at the service
entrance, and modern installations have what they call a "Ground Fault
Interrupter" which (AIUI) is usually an RCD.

However, there are still a lot of the older three-pin connectors and
appliances that don't have the separate protective ground. The fourth
wire became required when it finally dawned on them that the neutral
could break, allowing the appliance frame to float live.

Because the distinction between neutral and earth/ground is a relatively
late arrival in the USA, many older installations don't comply and there
is still a lot of very basic misunderstanding about it.



--
Ian White

On Sun, 4 Dec 2005 06:39:04 -0000, "David Lee"
wrote:

Victor Roberts wrote...
I'm not sure he meant that the same outlet would have
120-volt sockets plus one or more 240-volt sockets. Just
that we have a 240-volt socket that is different, obviously,
than the 120-volt socket.

What I recall seeing was a reference that stated that "the code" recommended
that duplex outlets in a kitchen should be wired with the two socket on
different "phases" and that there was a "special" plug that contacted both
sockets to give a 240V supply for such things as kettles and toasters. I
have never managed to find this again or any other reference to it.

I have never seen such a plug and I find it hard to believe
that the National Electrical Code would not recommend this,
and may even prohibit two lines from different phases being
in the same box that is used for 120-volt outlets. However,
I have not checked the NEC on this matter so I'm just
guessing here.

However
I have seen an adapter advertised that you plug into two separate 120V
outlets using two power cords. When you have plugged it into two different
"phases" a lamp illuminates to indicate that 240V is available.

We have very few portable 240-volt appliances, and those
that we have are really not portable and usually use high
current even at 240 volts so they would not be usable on
dual 120-volt circuits. Appliances that run on 240 volts in
the typical US house include water heaters, whole-house air
conditioners, electric stoves (which can be purchased as
cooktops and ovens) electric clothes dryers and some water
pumps used for wells. I have never used electric heat, but I
suspect that the baseboard heaters are also 240-volt. Of
these, all are typically hard-wired except the electric
dryer. I believe it is possible to find 240-volt "portable"
room air conditioners, but they would need their own
dedicated high current 240-volt outlet. I also believe that
some new high power microwave ovens are designed for 240
volts, but I also believe these are the built-in style
designed for mounting over the counter or stove, so they
would be hard wired.

The cord you mention would have little use with appliances I
have seen in the US, though it might be of value to someone
who purchased an appliance in Europe or some other area that
uses 240 volts and wanted to use it at their home in the US.
I would not expect such use to be condoned by the NEC.

However since I am British my experience of US wiring is necessarily limited
to brief visits.

And so with my experience with your system.

Cheers,

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

Victor Roberts wrote...
I have never seen such a plug and I find it hard to believe
that the National Electrical Code would not recommend this,
and may even prohibit two lines from different phases being
in the same box that is used for 120-volt outlets. However,
I have not checked the NEC on this matter so I'm just
guessing here.

A bit more Googling suggests that the recommendation of split-wired duplex
kitchen outlets may be Canadian rather than USA - but I still can't find the
mention of using these to get 240V that I'm sure I've seen before!

I must say that when I was in the US I was rather alarmed at the way that a
"high speed" kettle plug seemed to get hotter than the kettle itself and the
kettle still took ages to boil! In the UK, with our 240V supply, we can get
3kW kettles that really are fast and their cords and plugs stay perfectly
cool.

David

On Sun, 4 Dec 2005, David Lee wrote:

What I recall seeing was a reference that stated that "the code"
recommended that duplex outlets in a kitchen should be wired with the
two socket on different "phases" and that there was a "special" plug
that contacted both sockets to give a 240V supply for such things as
kettles and toasters.

No, our kettles, toasters and all other countertop appliances run on 120.

I've never ever seen the setup you describe. Doesn't mean it doesn't
exist, I've just never seen it anywhere in North America.

On Sun, 4 Dec 2005, David Lee wrote:

A bit more Googling suggests that the recommendation of split-wired duplex
kitchen outlets may be Canadian rather than USA

Don't believe so, no.

(I'm in Canada)


I must say that when I was in the US I was rather alarmed at the way
that a "high speed" kettle plug seemed to get hotter than the kettle
itself and the kettle still took ages to boil! In the UK, with our 240V
supply, we can get 3kW kettles that really are fast and their cords and
plugs stay perfectly cool.

One of the disadvantages of 120v mains...

On Sun, 4 Dec 2005 17:57:54 -0500,it is alleged that "Daniel J. Stern"
spake thusly in uk.d-i-y:

On Sun, 4 Dec 2005, David Lee wrote:

A bit more Googling suggests that the recommendation of split-wired duplex
kitchen outlets may be Canadian rather than USA

Don't believe so, no.

(I'm in Canada)

Don't have a copy of the current CEC to check, but the receptacles on
the kitchen circuits at the house I stayed in in Ontario were split
wired on a 240v 15A circuit, I questioned it with the electrician and
he said "That's one of the differences from the US, they use 20A 120v
circuits, we use multiwire 120/240v".

This of course can change from year to year with each reissue of the
code, and even by local jurisdiction.


I must say that when I was in the US I was rather alarmed at the way
that a "high speed" kettle plug seemed to get hotter than the kettle
itself and the kettle still took ages to boil! In the UK, with our 240V
supply, we can get 3kW kettles that really are fast and their cords and
plugs stay perfectly cool.

One of the disadvantages of 120v mains...


--
Whenever people say "we mustn't be sentimental", you can take it
they are about to do something cruel. And if they add, "we must
be realistic", they mean they are going to make money out of it.
- Brigid Brophy

Simon Waldman wrote:

Sawney Beane wrote:

There goes my theory. The next step is to increase my household
voltage so I can try out some British lamps. What voltge will I need?

Depends on how bright you want them to be :-)

European supply is nominally 230V nowadays. I believe that some US homes
have 220V available (am I right?), in which case this should light
British lamps quite happily, if not quite at full brightness.

FWIW, you will probably find things slightly dimmer for the same
wattage. One of the disadvantages of our higher mains voltage is that
incandescant lamps are a little less efficient.

I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

In America, standard 75 and 100W bulbs, which run about 750 hours,
are more efficient than 60 and 40W bulbs, which run about 1000
hours. I once used a bridge rectifier and a capacitor to run a 15W
bulb at approximately 140 VDC. It was a pleasant light.

For flashlights (torches) 5v seems to work better than 2.5. I
think it's because the resistance at the various connections makes
less difference at the higher voltage. I wonder if there's an
ideal voltage for a flashlight.

On Mon, 5 Dec 2005, Sawney Beane wrote:

FWIW, you will probably find things slightly dimmer for the same
wattage. One of the disadvantages of our higher mains voltage is that
incandescant lamps are a little less efficient.

I'll have to think about the math. If filaments were made of the same
wire, they would have to be four times longer in Europe for the same
wattage, but then they would run much cooler. I guess European
filaments are longer and thinner. How does that require a less
energy-efficient design?

Longer/thinner wire in similarly-sized overall package generally means
coiled-coil rather than single-coil filaments. CC filaments of any given
length generally have lower overall surface luminance.

In article ,
Sawney Beane writes:
I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

There aren't enough variables in the equation. The longer
thinner wire has more surface area, and therefore both
radiates more energy and convects more into the gas fill,
meaning it won't get as hot so less of the energy output
is as visible light. The coiled-coil design helps to conteract
this by giving the filament an effective length and diameter of
the outside of the coiled-coil for the purposes of radiation
and convection, but it's not as effective as using an
optimally sized filament in the first place (which turns
out to be something like 55V for 100W lamp).

For flashlights (torches) 5v seems to work better than 2.5. I
think it's because the resistance at the various connections makes
less difference at the higher voltage. I wonder if there's an
ideal voltage for a flashlight.

With very low voltage lamps with short filaments, loss
from each end of the filament by conduction to the lead-in
wires can be a significant factor too.

--
Andrew Gabriel

I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

My understanding is that standard incandescent lightbulbs are most efficient
at around 100V, so US bulbs should work better than European ones. There's
basically a most efficient thickness of the filament. A 230V filament is too
thin.

Christian.

On Mon, 05 Dec 2005 23:23:49 -0500, Sawney Beane
wrote:

Simon Waldman wrote:

Sawney Beane wrote:

There goes my theory. The next step is to increase my household
voltage so I can try out some British lamps. What voltge will I need?

Depends on how bright you want them to be :-)

European supply is nominally 230V nowadays. I believe that some US homes
have 220V available (am I right?), in which case this should light
British lamps quite happily, if not quite at full brightness.

FWIW, you will probably find things slightly dimmer for the same
wattage. One of the disadvantages of our higher mains voltage is that
incandescant lamps are a little less efficient.

I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

Since we can always trade off life against efficacy we must
compare lamp efficacy for two designs at the same rated
life.

For the same wire diameter, a thinner wire must be operated
at lower temperature to achieve the same life. Lower
temperature leads to lower efficacy.

In America, standard 75 and 100W bulbs, which run about 750 hours,
are more efficient than 60 and 40W bulbs, which run about 1000
hours.

The higher efficacy comes from both the shorter life (750
hours vs. 1000 hours) and the fact that a 100-watt lamp can
use thicker wire then a 60-watt or 40-watt lamp with the
same rated life.

I once used a bridge rectifier and a capacitor to run a 15W
bulb at approximately 140 VDC. It was a pleasant light.

For flashlights (torches) 5v seems to work better than 2.5. I
think it's because the resistance at the various connections makes
less difference at the higher voltage. I wonder if there's an
ideal voltage for a flashlight.

You also need to consider end losses from the filament to
the support wire. Without end losses there would be no
"optimum" voltage for any lamp. The largest wire would
always be the best under these idealized conditions because
it could be operated at the highest efficacy. However, with
you balance end losses from the filament to the supports
against evaporation of the filament, you find an optimum
wire size and hence an optimum voltage for any power. The
optimum voltage is a function of power and rated life and
increases as the power increases.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

"Victor Roberts" wrote in message
...
On Mon, 05 Dec 2005 23:23:49 -0500, Sawney Beane
wrote:

Simon Waldman wrote:

Sawney Beane wrote:

There goes my theory. The next step is to increase my household
voltage so I can try out some British lamps. What voltge will I need?

Depends on how bright you want them to be :-)

European supply is nominally 230V nowadays. I believe that some US homes
have 220V available (am I right?), in which case this should light
British lamps quite happily, if not quite at full brightness.

FWIW, you will probably find things slightly dimmer for the same
wattage. One of the disadvantages of our higher mains voltage is that
incandescant lamps are a little less efficient.

I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

Since we can always trade off life against efficacy we must
compare lamp efficacy for two designs at the same rated
life.

For the same wire diameter, a thinner wire must be operated
at lower temperature to achieve the same life. Lower
temperature leads to lower efficacy.

In America, standard 75 and 100W bulbs, which run about 750 hours,
are more efficient than 60 and 40W bulbs, which run about 1000
hours.

The higher efficacy comes from both the shorter life (750
hours vs. 1000 hours) and the fact that a 100-watt lamp can
use thicker wire then a 60-watt or 40-watt lamp with the
same rated life.

I once used a bridge rectifier and a capacitor to run a 15W
bulb at approximately 140 VDC. It was a pleasant light.

For flashlights (torches) 5v seems to work better than 2.5. I
think it's because the resistance at the various connections makes
less difference at the higher voltage. I wonder if there's an
ideal voltage for a flashlight.

You also need to consider end losses from the filament to
the support wire. Without end losses there would be no
"optimum" voltage for any lamp. The largest wire would
always be the best under these idealized conditions because
it could be operated at the highest efficacy. However, with
you balance end losses from the filament to the supports
against evaporation of the filament, you find an optimum
wire size and hence an optimum voltage for any power. The
optimum voltage is a function of power and rated life and
increases as the power increases.

--
Vic Roberts
http://www.RobertsResearchInc.com

One incandescent lamp optimization model that the GE lamp engineers used
some years ago kept pointing to 50 volts or so as the best for consumer
household lamps in the 40-150 watt range. The model took into account end
losses, filament supports, gas mixture wire diameter, lumen output required,
life, etc. as I recall.

Terry McGowan

TKM wrote:

"Victor Roberts" wrote in message
...
On Mon, 05 Dec 2005 23:23:49 -0500, Sawney Beane
wrote:

Simon Waldman wrote:

Sawney Beane wrote:

There goes my theory. The next step is to increase my household
voltage so I can try out some British lamps. What voltge will I need?

Depends on how bright you want them to be :-)

European supply is nominally 230V nowadays. I believe that some US homes
have 220V available (am I right?), in which case this should light
British lamps quite happily, if not quite at full brightness.

FWIW, you will probably find things slightly dimmer for the same
wattage. One of the disadvantages of our higher mains voltage is that
incandescant lamps are a little less efficient.

I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

Since we can always trade off life against efficacy we must
compare lamp efficacy for two designs at the same rated
life.

For the same wire diameter, a thinner wire must be operated
at lower temperature to achieve the same life. Lower
temperature leads to lower efficacy.

In America, standard 75 and 100W bulbs, which run about 750 hours,
are more efficient than 60 and 40W bulbs, which run about 1000
hours.

The higher efficacy comes from both the shorter life (750
hours vs. 1000 hours) and the fact that a 100-watt lamp can
use thicker wire then a 60-watt or 40-watt lamp with the
same rated life.

I once used a bridge rectifier and a capacitor to run a 15W
bulb at approximately 140 VDC. It was a pleasant light.

For flashlights (torches) 5v seems to work better than 2.5. I
think it's because the resistance at the various connections makes
less difference at the higher voltage. I wonder if there's an
ideal voltage for a flashlight.

You also need to consider end losses from the filament to
the support wire. Without end losses there would be no
"optimum" voltage for any lamp. The largest wire would
always be the best under these idealized conditions because
it could be operated at the highest efficacy. However, with
you balance end losses from the filament to the supports
against evaporation of the filament, you find an optimum
wire size and hence an optimum voltage for any power. The
optimum voltage is a function of power and rated life and
increases as the power increases.

--
Vic Roberts
http://www.RobertsResearchInc.com

One incandescent lamp optimization model that the GE lamp engineers used
some years ago kept pointing to 50 volts or so as the best for consumer
household lamps in the 40-150 watt range. The model took into account end
losses, filament supports, gas mixture wire diameter, lumen output required,
life, etc. as I recall.

Terry McGowan

I wonder how great the advantage is relative to 115 and 230. I
wonder if DC is better than AC. With modern semiconductors, would
it be worthwhile to build lamps to supply the ideal voltage for an
incandescent bulb of a certain wattage?

One popular type of desk lamp uses an automotive brake bulb and a
12V transformer. Is 12V better than 50 for a bulb of 20W or so?

European supply is nominally 230V nowadays. I believe that some US
homes
have 220V available (am I right?), in which case this should light
British lamps quite happily, if not quite at full brightness.

..
In my typical North American (35 year old Canadian) house we have 3
conductors coming in from the supply.
Two live (hot) wires and one neutral/zero voltage wire. The neutral is
grounded/earthed by the power supply company and also to our ground rod; it
is also bonded to our copper water supply pipe.

Between the two 'hot wires' there is nominally 230 volts. This used for
heavy appliances such as cooking stove, hot water cylinder (A typical 30 Imp
gal. insulated tank) and clothes dryer. The 230 circuits are distributed
through two pole circuit breakers; each major appliance on a dedicated
radial circuit. These circuits use wire that is gauged for the type of load.
For example our cooking stove is wired with #8 AWG .

Between each of the 'hot' wires and neutral there is nominally 115 volts.
This is distributed via single pole circuit breakers and radial circuits.
There are various 'rules' concerning the number out duplex outlets on each
'run' (radial circuit). e.g. every six feet of wall with maximum of ten
outlets on a run, or less where load is expected to be heavier. Our outlets
are wired with #12 AWG and 20 amp breakers. Lighting is wired with #14 AWG
and 15 amp breakers.

At one time lighting and outlets were not mixed on the same radial circuit.
In this jurisdiction (A Canadian province) mixing them now appears to be
approved. As an example I recently changed a circuit breaker at the main
panel (CU) from 20A to 15A because I knew that some wiring had been extended
and now included 14 AWG as well as the original 12 AWG.

The result is that we have 'plenty' of individual radial circuits which is
probably good in view that current is twice that at 230 volts!

Ring mains appear to be unknown and not used here.

So; yes 230 volts is available. BUT: both sides of it are alive to
neutral/earth and ground. This might require two pole switches to safely
disconnect 'both sides' or live 'legs' from supply. My 230 volt bench saw
motor has a two pole 'Off' switch for example. Most of my other 'power
tools' are 115 volt and plug in to conventional outlets.

I just measured the voltages at about 18.00 hrs local time and got the
following;
Leg a) to neutral 117.2 volts AC RMS.
Leg b) to neutral 121.1 volts AC RMS.
Leg a) to leg b) 234.6 volts AC RMS.

But it's varying slightly from moment to moment as the evening loads and
currently people switch on their Christmas lights.

OH. BTW it's an o.head service from the pole mounted distribution
transformer two spans ( about 15 feet) ) from the house. the transformer
feeds sevaerl houses Our 'service entrance' is rated at 200 amps. The meter
is mounted outside on end of house for easy access by meter reader. Normally
read monthly although occasionally estimated if bad weather. Monthly
billing. Service is excellent, technical repair is fast and obliging despite
our severe weather conditions. Power co. billing system works well. Easy
toll free contact to discuss and make changes/corrections. Cost recently
went up but on average total monthly bill divided by kilowatt hours = about
ten cents Canadian. That's roughly 4.1 pence per unit. There are no
'cheaper' late night rates AFIK, cost is same during whole 24 hours. The
power company has installed a few remote reading meters as a trial and in a
few instances where the meter location is very inconvenient or enclosed.

Any interest to the OP above?

"Sawney Beane" wrote in message
...
TKM wrote:

"Victor Roberts" wrote in message
...
On Mon, 05 Dec 2005 23:23:49 -0500, Sawney Beane
wrote:

Simon Waldman wrote:

Sawney Beane wrote:

There goes my theory. The next step is to increase my household
voltage so I can try out some British lamps. What voltge will I
need?

Depends on how bright you want them to be :-)

European supply is nominally 230V nowadays. I believe that some US
homes
have 220V available (am I right?), in which case this should light
British lamps quite happily, if not quite at full brightness.

FWIW, you will probably find things slightly dimmer for the same
wattage. One of the disadvantages of our higher mains voltage is that
incandescant lamps are a little less efficient.

I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

Since we can always trade off life against efficacy we must
compare lamp efficacy for two designs at the same rated
life.

For the same wire diameter, a thinner wire must be operated
at lower temperature to achieve the same life. Lower
temperature leads to lower efficacy.

In America, standard 75 and 100W bulbs, which run about 750 hours,
are more efficient than 60 and 40W bulbs, which run about 1000
hours.

The higher efficacy comes from both the shorter life (750
hours vs. 1000 hours) and the fact that a 100-watt lamp can
use thicker wire then a 60-watt or 40-watt lamp with the
same rated life.

I once used a bridge rectifier and a capacitor to run a 15W
bulb at approximately 140 VDC. It was a pleasant light.

For flashlights (torches) 5v seems to work better than 2.5. I
think it's because the resistance at the various connections makes
less difference at the higher voltage. I wonder if there's an
ideal voltage for a flashlight.

You also need to consider end losses from the filament to
the support wire. Without end losses there would be no
"optimum" voltage for any lamp. The largest wire would
always be the best under these idealized conditions because
it could be operated at the highest efficacy. However, with
you balance end losses from the filament to the supports
against evaporation of the filament, you find an optimum
wire size and hence an optimum voltage for any power. The
optimum voltage is a function of power and rated life and
increases as the power increases.

--
Vic Roberts
http://www.RobertsResearchInc.com

One incandescent lamp optimization model that the GE lamp engineers used
some years ago kept pointing to 50 volts or so as the best for consumer
household lamps in the 40-150 watt range. The model took into account
end
losses, filament supports, gas mixture wire diameter, lumen output
required,
life, etc. as I recall.

Terry McGowan

I wonder how great the advantage is relative to 115 and 230. I
wonder if DC is better than AC. With modern semiconductors, would
it be worthwhile to build lamps to supply the ideal voltage for an
incandescent bulb of a certain wattage?

One popular type of desk lamp uses an automotive brake bulb and a
12V transformer. Is 12V better than 50 for a bulb of 20W or so?

A-line lamps are fairly well optimized given the requirements to operate on
the 120 or 240 volt supplies since designers have had about 100 years now
to work on them. After the basic material properties are known and
accounted for, then manufacturing details begin to be the important
determinants of performance. How uniform is the filament? How should the
coil be mounted to minimize shock/vibration? What sort of seal should be
used? How pure must the gas fill be? Etc.

I doubt that it would be worth developing a comprehensive "optimized lamp
design" at a non-standard voltage and then use electronics to obtain that
voltage from the line since the performance of lamps now is probably within
a few percent of optimum anyway and there are losses in transformation.
Traditionally, AC has been thought superior to DC operation of incandescent
lamps because so-called filament "notching" can occurr on dc plus if there
is any moisture present in the base/seal area, metal can electrolytically
move from one line to another and cause seal or line failure.

We are close to the point where we'll likely see major attempts to reduce
the use of incandescent lamps too. California has made such a move; but I
doubt GLS lamps will disappear anytime soon.

Terry McGowan

On Fri, 9 Dec 2005 18:18:46 -0330, "Terry"
wrote:


I just measured the voltages at about 18.00 hrs local time and got the
following;
Leg a) to neutral 117.2 volts AC RMS.
Leg b) to neutral 121.1 volts AC RMS.
Leg a) to leg b) 234.6 volts AC RMS.

But it's varying slightly from moment to moment as the evening loads and
currently people switch on their Christmas lights.

It's interesting that a-to-b does not equal the sum of
a-to-neutral plus b-to-neutral. This must be due to the
variations with time and the fact that all three
measurements were not made at the same time.

BTW - the difference between a-to-neutral and b-to-neutral
may indicate a weak neutral. A few weeks ago the neutral
connection at my home (in the US) broke at the pole and my
system was balanced only by the backup neutral connection to
the water line. One side was about 100 volts while the other
was 140. I called the power company and they immediately
disconnected the house and fixed the neutral.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

On Fri, 09 Dec 2005 15:03:06 -0500, Sawney Beane
wrote:

TKM wrote:

"Victor Roberts" wrote in message
...
On Mon, 05 Dec 2005 23:23:49 -0500, Sawney Beane
wrote:

Simon Waldman wrote:

Sawney Beane wrote:

There goes my theory. The next step is to increase my household
voltage so I can try out some British lamps. What voltge will I need?

Depends on how bright you want them to be :-)

European supply is nominally 230V nowadays. I believe that some US homes
have 220V available (am I right?), in which case this should light
British lamps quite happily, if not quite at full brightness.

FWIW, you will probably find things slightly dimmer for the same
wattage. One of the disadvantages of our higher mains voltage is that
incandescant lamps are a little less efficient.

I'll have to think about the math. If filaments were made of the
same wire, they would have to be four times longer in Europe for
the same wattage, but then they would run much cooler. I guess
European filaments are longer and thinner. How does that require a
less energy-efficient design?

Since we can always trade off life against efficacy we must
compare lamp efficacy for two designs at the same rated
life.

For the same wire diameter, a thinner wire must be operated
at lower temperature to achieve the same life. Lower
temperature leads to lower efficacy.

In America, standard 75 and 100W bulbs, which run about 750 hours,
are more efficient than 60 and 40W bulbs, which run about 1000
hours.

The higher efficacy comes from both the shorter life (750
hours vs. 1000 hours) and the fact that a 100-watt lamp can
use thicker wire then a 60-watt or 40-watt lamp with the
same rated life.

I once used a bridge rectifier and a capacitor to run a 15W
bulb at approximately 140 VDC. It was a pleasant light.

For flashlights (torches) 5v seems to work better than 2.5. I
think it's because the resistance at the various connections makes
less difference at the higher voltage. I wonder if there's an
ideal voltage for a flashlight.

You also need to consider end losses from the filament to
the support wire. Without end losses there would be no
"optimum" voltage for any lamp. The largest wire would
always be the best under these idealized conditions because
it could be operated at the highest efficacy. However, with
you balance end losses from the filament to the supports
against evaporation of the filament, you find an optimum
wire size and hence an optimum voltage for any power. The
optimum voltage is a function of power and rated life and
increases as the power increases.

--
Vic Roberts
http://www.RobertsResearchInc.com

One incandescent lamp optimization model that the GE lamp engineers used
some years ago kept pointing to 50 volts or so as the best for consumer
household lamps in the 40-150 watt range. The model took into account end
losses, filament supports, gas mixture wire diameter, lumen output required,
life, etc. as I recall.

Terry McGowan

I wonder how great the advantage is relative to 115 and 230. I
wonder if DC is better than AC. With modern semiconductors, would
it be worthwhile to build lamps to supply the ideal voltage for an
incandescent bulb of a certain wattage?

I don't have the data for an optimum voltage 100-watt lamp,
but you can see the effect by comparing 120-volt against
230-volt incandescent lamps. A typical 100-watt, 120-volt,
750-hour, frosted incandescent lamp has an efficacy of 17.1
lm/W while a 100-watt, 240-volt 1000-hour, frosted
incandescent lamp has an efficacy of 13.3 lm/W. (I can't
find 120-volt and 240-volt 100-watt lamps with the same
life.) Adjusting the efficacy of the 750-hour lamp for
1000-hour life reduces its efficacy to 16.4 lm/W, which is
still 23% better than the 240-volt lamp of the same life.

Also, I see a 100-watt, 34-volt 1000-hour frosted lamp
listed with an efficacy of 21.6 lm/W, while a 100-watt,
12-volt, 1000-hour frosted lamp is listed with an efficacy
of 17.5 lm/W.

One popular type of desk lamp uses an automotive brake bulb and a
12V transformer. Is 12V better than 50 for a bulb of 20W or so?

I'm not sure. Looking again at 1000-hour lamps, a 12-volt
25-watt lamp is slightly less efficient than a 34-volt
25-watt lamp with the same life. (I don't have data in 20
watt lamps.) Reducing the power reduces the optimum voltage,
but the efficacy at 50 volts may be above the peak for a
20-watt lamp.

--
Vic Roberts
http://www.RobertsResearchInc.com
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On Fri, 09 Dec 2005 22:53:49 GMT, "TKM"
wrote:

I wonder how great the advantage is relative to 115 and 230. I
wonder if DC is better than AC. With modern semiconductors, would
it be worthwhile to build lamps to supply the ideal voltage for an
incandescent bulb of a certain wattage?

One popular type of desk lamp uses an automotive brake bulb and a
12V transformer. Is 12V better than 50 for a bulb of 20W or so?

A-line lamps are fairly well optimized given the requirements to operate on
the 120 or 240 volt supplies since designers have had about 100 years now
to work on them. After the basic material properties are known and
accounted for, then manufacturing details begin to be the important
determinants of performance. How uniform is the filament? How should the
coil be mounted to minimize shock/vibration? What sort of seal should be
used? How pure must the gas fill be? Etc.

I doubt that it would be worth developing a comprehensive "optimized lamp
design" at a non-standard voltage and then use electronics to obtain that
voltage from the line since the performance of lamps now is probably within
a few percent of optimum anyway and there are losses in transformation.

I agree with your statement in the first paragraph - if we
are constrained to operate to 120 or 240 volts. However I
disagree with your later statement that lamp performance is
within a few percent of optimum - if we are allowed to
change the operating voltage. I do, however, agree that it
would not be worth if from an economic point of view to
develop a disposable voltage converter for incandescent
lamps.

Someone did try to put a diode in the base of each lamp to
reduce the RMS voltage from 120 volts to 84.9 volts. This
does increase efficacy at low cost, and if half the diodes
are inserted one way, while the other half are inserted with
opposite polarity, there should be no net effect on the
power grid or metering. However, this option opens the door
for crafty people to select lamps with all the same polarity
and hence get part of their power for free, so this idea was
dropped, I believe under pressure from the power companies.

Traditionally, AC has been thought superior to DC operation of incandescent
lamps because so-called filament "notching" can occurr on dc plus if there
is any moisture present in the base/seal area, metal can electrolytically
move from one line to another and cause seal or line failure.

So, life with AC is better than with DC, but the switch from
one to the other does not effect efficacy. In fact, the RMS
voltage of an AC waveform is defined as the DC voltage that
gives the same heating power - and we all know that
incandescent lamps are just heaters that happen to generate
a bit of light.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

In article , Sawney Beane wrote:

SNIP lots of previously quoted stuff as to design voltage for maximizing
luminous efficacy of incandescent lamps)

I wonder how great the advantage is relative to 115 and 230.

120 may or may not be not much worse than the 50 mentioned above, but
my experience of hearing lumen figures mentioned before tells me that
design voltage of 230 results in notably less luminous efficacy than
design voltage of 120 for incandescent lamps in the 60-100 watt range.

I wonder if DC is better than AC.

No. And with medium to high wattages, to the very slight extent any
difference can be found, DC is worse. As best as I understand, some tiny
percentage of the small trace of tungsten vapor in an incandescent lamp
gets ionized by the small amount of UV present, forming a few positive
tungsten ions, and those get attracted towards the negative end of the
filament and away from the positive end, to an extent that results in the
positive end of the filament suffering from tungsten evaporation slightly
more than the negative end.
Even the slightest unevenness in filament evaporation reinforces itself
once things progress to the point of even a minor unevenness of
temperature along the filament.

With modern semiconductors, would it be worthwhile to build lamps to
supply the ideal voltage for an incandescent bulb of a certain wattage?

I have seen nightlights/accent-lights under the GE brand using low
voltage incandescent lamps and some sort of electronics to deliver low RMS
voltage from 120V AC line voltage. Best as I can remember, these consume
1.5 watts and produce more than half as much light as 4 watt 120V
incandescents.

One popular type of desk lamp uses an automotive brake bulb and a
12V transformer. Is 12V better than 50 for a bulb of 20W or so?

Yes - for wattages in the 10-40 watt range, the design that maximizes
luminous efficacy of a given wattage and life expectancy has the filament
singly coiled, voltage around 10-14 volts, and the bulb being gas-filled.

If you add a restriction of the filament being singly coiled, then the
optimum design voltage is only in the 20's when the wattage is a couple
hundred watts and closer to 14 than to 28 at 100 watts - based on how I
saw data in a miniature/automotive lamp catalog.

As for how much difference this makes: A desk light with a 93 lamp/"bulb"
(design voltage 12.8 volts) with losses in its transformer consumes only a
little less power than a 120V incandescent of the same light output and
life expectancy.

A 93 at 12.8 volts consumes about 13.3 watts, is designed to last 700
hours on average and typically produces 188 lumens. Add losses from the
transformer and I guesstimate 16 watts, maybe 17.
A 120V 15 watt 2000-2500 hour lamp produces 110-126 lumens. If
producing 125 lumens and lasting 2000 hours, then when overvoltaged to
last 700 hours it would consume about or slightly over 17 watts and
produce maybe 165-170 lumens.

To me, this indicates that there is not a whole lot to gain from changing
the voltage from 120V to improve luminous efficacy of incandescent lamps
in the 15 to 100-plus watt range. And at lower wattages, there is less to
save in electricity costs.

Keep in mind also how much a 4-pack of A19 lamps costs at Lowes - not
much more than one automotive lamp retail anywhere as far as I know. May
as well accept 16.7-17.5 lumens/watt (at 100 watts) or 14.1-14.8 lumens/w
(at 60 watts) if using incandescent powered by 120V line voltage.

- Don Klipstein )

Victor Roberts wrote:

I agree with your statement in the first paragraph - if we
are constrained to operate to 120 or 240 volts. However I
disagree with your later statement that lamp performance is
within a few percent of optimum - if we are allowed to
change the operating voltage. I do, however, agree that it
would not be worth if from an economic point of view to
develop a disposable voltage converter for incandescent
lamps.

Someone did try to put a diode in the base of each lamp to
reduce the RMS voltage from 120 volts to 84.9 volts. This
does increase efficacy at low cost, and if half the diodes
are inserted one way, while the other half are inserted with
opposite polarity, there should be no net effect on the
power grid or metering. However, this option opens the door
for crafty people to select lamps with all the same polarity
and hence get part of their power for free, so this idea was
dropped, I believe under pressure from the power companies.

Traditionally, AC has been thought superior to DC operation of incandescent
lamps because so-called filament "notching" can occurr on dc plus if there
is any moisture present in the base/seal area, metal can electrolytically
move from one line to another and cause seal or line failure.

So, life with AC is better than with DC, but the switch from
one to the other does not effect efficacy. In fact, the RMS
voltage of an AC waveform is defined as the DC voltage that
gives the same heating power - and we all know that
incandescent lamps are just heaters that happen to generate
a bit of light.

Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

I found no flicker from sunshine and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Could that be true? It indicates that the filament temperature of
a bulb run on 60 Hz AC heats and cools significantly 120 times a
second. With DC, wouldn't filament temperature stay constant?
Wouldn't less peak voltage be required for a given amount of light?

If there is significant flicker and temperatue change with AC,
wouldn't it be worse with a half-wave rectifier?

On Tue, 13 Dec 2005 19:20:58 -0500, Sawney Beane
wrote:

Victor Roberts wrote:

I agree with your statement in the first paragraph - if we
are constrained to operate to 120 or 240 volts. However I
disagree with your later statement that lamp performance is
within a few percent of optimum - if we are allowed to
change the operating voltage. I do, however, agree that it
would not be worth if from an economic point of view to
develop a disposable voltage converter for incandescent
lamps.

Someone did try to put a diode in the base of each lamp to
reduce the RMS voltage from 120 volts to 84.9 volts. This
does increase efficacy at low cost, and if half the diodes
are inserted one way, while the other half are inserted with
opposite polarity, there should be no net effect on the
power grid or metering. However, this option opens the door
for crafty people to select lamps with all the same polarity
and hence get part of their power for free, so this idea was
dropped, I believe under pressure from the power companies.

Traditionally, AC has been thought superior to DC operation of incandescent
lamps because so-called filament "notching" can occurr on dc plus if there
is any moisture present in the base/seal area, metal can electrolytically
move from one line to another and cause seal or line failure.

So, life with AC is better than with DC, but the switch from
one to the other does not effect efficacy. In fact, the RMS
voltage of an AC waveform is defined as the DC voltage that
gives the same heating power - and we all know that
incandescent lamps are just heaters that happen to generate
a bit of light.

Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

I found no flicker from sunshine

You probably didn't wait long enough :-) The sun is known to
be a variable star. Data clearly shows reduction in output
near 1550 and another near 1700. Plus, there is the 11-year
sunspot cycle that has minor influence on the output of the
sun.

and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Could that be true? It indicates that the filament temperature of
a bulb run on 60 Hz AC heats and cools significantly 120 times a
second. With DC, wouldn't filament temperature stay constant?
Wouldn't less peak voltage be required for a given amount of light?

While typical incandescent lamps used in the US are
considered to be flicker-free there is obviously some
variation to the visible light output. Lower mass filaments
will obviously have more flicker than higher mass filaments,
so the amount of flicker depends upon the lamp power, the
operating voltage and the operating frequency plus other
factors.

A 100-watt 120-volt lamp will have less flicker than a
100-watt 240-volt lamp operating at the same frequency. A
40-watt 240-volt lamp will have more flicker, and if run on
50 Hz instead of 60 Hz it will have even more. I believe
that early hydroelectric power systems in the US, such as
Niagara Falls, generated power at 25 Hz and there was
significant visible flicker from (probably low power)
incandescent lamps used at the time.

One reference I found

http://www.epri-peac.com/tutorials/brf36tut.html

gives the thermal time constant of a 120-volt incandescent
lamp with a "typical" but unspecified power as 28
milliseconds and the thermal time constant of a 230-volt
lamp of the same power as 19 milliseconds. However, this
data is not useful by itself. Total radiation varies as T^4
and visible radiation, which is just the short wavelength
end of the SPD, will vary even faster with filament
temperature, so thermal time constants are of little value
unless the temperature is used to calculate visible
radiation. Note that the data at the link above shows that
even at 20 Hz the flicker perception of the lamps they
tested was far lower than the flicker perception of
fluorescent lamps operated at the same frequency.

What was the operating voltage and power of the lamp you
tested?

If there is significant flicker and temperatue change with AC,
wouldn't it be worse with a half-wave rectifier?

Much worse. The idea was proposed for a 100-watt, 85-volt
lamp operating at 60 Hz, which would reduce flicker a bit,
but there may still be flicker problems.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
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site without written permission.

Victor Roberts wrote:

You probably didn't wait long enough :-) The sun is known to
be a variable star. Data clearly shows reduction in output
near 1550 and another near 1700. Plus, there is the 11-year
sunspot cycle that has minor influence on the output of the
sun.


Try telling that to the anthropogenic global warming zealots.

MBQ

On Tue, 13 Dec 2005 19:20:58 -0500, Sawney Beane
wrote:

Victor Roberts wrote:

I agree with your statement in the first paragraph - if we
are constrained to operate to 120 or 240 volts. However I
disagree with your later statement that lamp performance is
within a few percent of optimum - if we are allowed to
change the operating voltage. I do, however, agree that it
would not be worth if from an economic point of view to
develop a disposable voltage converter for incandescent
lamps.

Someone did try to put a diode in the base of each lamp to
reduce the RMS voltage from 120 volts to 84.9 volts. This
does increase efficacy at low cost, and if half the diodes
are inserted one way, while the other half are inserted with
opposite polarity, there should be no net effect on the
power grid or metering. However, this option opens the door
for crafty people to select lamps with all the same polarity
and hence get part of their power for free, so this idea was
dropped, I believe under pressure from the power companies.

Traditionally, AC has been thought superior to DC operation of incandescent
lamps because so-called filament "notching" can occurr on dc plus if there
is any moisture present in the base/seal area, metal can electrolytically
move from one line to another and cause seal or line failure.

So, life with AC is better than with DC, but the switch from
one to the other does not effect efficacy. In fact, the RMS
voltage of an AC waveform is defined as the DC voltage that
gives the same heating power - and we all know that
incandescent lamps are just heaters that happen to generate
a bit of light.

Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

I found no flicker from sunshine and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Could that be true? It indicates that the filament temperature of
a bulb run on 60 Hz AC heats and cools significantly 120 times a
second. With DC, wouldn't filament temperature stay constant?
Wouldn't less peak voltage be required for a given amount of light?

There is some very interesting flicker data in the IES
Handbook (2000) - where I should have looked in the first
place. This data supports the perception that typical
incandescent lamps used for general lighting at 120 volts
and 60 Hz do not produce noticeable flicker.

"Incandescent lamps operated below 25 Hz will produce
perceptible flicker and can create a stroboscopic effect.
Flicker will be less from an incandescent source if it has a
larger filament and is operated at a higher wattage and at a
higher supply frequency. Modern incandescent light sources
operated at 60 Hz do not produce noticeable flicker, nor a
stroboscopic effect, to the human eye. The flicker index of
several incandescent lamps operated at 25 Hz and 60 Hz is
shown in Figure 6-16. Consult Chapter 2, Measurement of
Light and Other Radiant Energy, for more information about
lamp flicker."

And here is their data: (To see the table correctly you will
have to use a fixed font instead of a variable font.

Watts Percent Flicker Flicker Index
60 Hz 25 Hz 60 Hz 25 Hz
6* 29 69 0.092 0.220
10* 17 40 0.054 0.127
25* 10 28 0.032 0.089
40+ 13 29 0.041 0.092
60# 8 19 0.025 0.060
100# 5 14 0.016 0.045
200+ 4 11 0.013 0.035
300+ 3 8 0.010 0.025
500+ 2 6 0.006 0.019
1000+ 1 4 0.003 0.013

* Vacuum
+ Coiled-coil filament
# Gas-filled


The symbols are a bit confusing since I believe that 60 watt
lamps and above have both coiled-coils and gas filling,
though the table does not show that. Also remember that the
data above is for 120-volt lamps.

Here is the official description of the Flicker Index from
the 2000 IESNA Lighting Handbook:

"The flicker index has been established as a reliable
relative measure of the cyclic variation in output of vari-
ous sources at a given power frequency. It takes into
account the waveform of the light output as well as its
amplitude. It is calculated by dividing the area above the
line of average light output by the total area under the
light output curve for a single curve. [The area below the
line of average light output] may be close to zero if light
output varies as periodic spikes.

The flicker index assumes values from 0 to 1.0, with 0 for
steady light output. Higher values indicate in increased
possibility of noticeable stroboscopic effect, as well as
lamp flicker."

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

Victor Roberts wrote...
You probably didn't wait long enough :-) The sun is known to
be a variable star. Data clearly shows reduction in output
near 1550 and another near 1700.

So what happens at half past three and five o'clock that's so special?

;-)

David

In article ,
Sawney Beane writes:

Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

You need to be much more precise here. I don't know the
characteristics of a CdS, but those of the human eye are
not useful here, as the limiting factor is the human brain.
A human eye will transmit flicker to the brain at well over
100Hz, but the human brain can't work that fast -- it's too
big. The upper range of flicker visible varies by person,
but is between 55Hz and 70Hz. A fly's brain can work much
faster, being much smaller, so a fly can see flicker at
much higher speeds (~1000Hz IIRC). It may be that our
ancestor's smaller brains were faster and matched to the
speed of human eyes many years ago, but this turned out to
be less of an evolutionary advantage than a bigger brain.

Incandescent lamps running on 50 or 60Hz will be flickering
at 100 or 120Hz respectively (if they are flickering at all),
which is well above the human perception level.

I found no flicker from sunshine and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Sounds a bit doubtful to me, but maybe not impossible.
Fluorescent lamp flicker is much more complex. The light from
a fluorescent lamp comes from multiple different sources, i.e.
several different phosphors generating different colours, and
the gas discharge itself generating some prominant lines.
The gas discharge is going to have quite a pronounced flicker,
switching on and off at twice the line frequency. For the
phosphors, they all tend to have different persistance, some
reds for example, having a persistance which will maintain
light output over the dark periods from the discharge. So if
the CdS cell is particularly sensitive to the light from those
red phosphors, it's going to see a lot less flicker than if it
is more sensitive to one of the gas discharge lines.

BTW, here's a nice experiment you can carry out to observe this
effect in a fluorescent lamp. Take a lamp firmly fixed to a
long cord (such as a car service/inspection lamp), and go out
into a large dark area (e.g. outside at night) where there are
no objects for many feet in any direction. Switch the lamp on,
and swing it round and round over your head on the end of the
cord. As it passes in front of you each time, you will see the
stroboscopic effect of the different colour components which
make up the white light, and in particular you will notice how
they are all out of phase with each other, with some of the
phosphor components having much longer persistance than others.
Obviously be careful here -- if you manage to hurl a car
inspection lamp through your neighbour's window, don't come
crying to me...

--
Andrew Gabriel

"Andrew Gabriel" wrote in message
...
[snip]

BTW, here's a nice experiment you can carry out to observe this
effect in a fluorescent lamp. Take a lamp firmly fixed to a
long cord (such as a car service/inspection lamp), and go out
into a large dark area (e.g. outside at night) where there are
no objects for many feet in any direction. Switch the lamp on,
and swing it round and round over your head on the end of the
cord. As it passes in front of you each time, you will see the
stroboscopic effect of the different colour components which
make up the white light, and in particular you will notice how
they are all out of phase with each other, with some of the
phosphor components having much longer persistance than others.
Obviously be careful here -- if you manage to hurl a car
inspection lamp through your neighbour's window, don't come
crying to me...

For crying out loud, Andrew! Couldn't you think of a simpler way than this?

Like, for example, reflect the light of the fluorescent off the convex side
of a large spoon and swing the spoon a little bit?

Your are giving the previous poster reasons to do some serious damage,
particularly if he tries it with a Chinese "CE certified" fluorescent chord
luminaire!

Never mind what the police will think if they see a guy in the dark swinging
a fluorescent tube:

"What are you doing there?"

"I'm trying to observe the stroboscopic effect..."

"The WHAT?!"

"You know, when the light goes on and off at 120 Hz, and the phosphors have
this persistence, see, and you can...by rotating FAST the lamp..."

"Arrest him. He is dangerous"...

--
Andrew Gabriel
--
Ioannis
http://ioannis.virtualcomposer2000.com/
Eventually, _everything_ is understandable

Victor Roberts wrote:
On Tue, 13 Dec 2005 19:20:58 -0500, Sawney Beane
wrote:


Victor Roberts wrote:

I agree with your statement in the first paragraph - if we
are constrained to operate to 120 or 240 volts. However I
disagree with your later statement that lamp performance is
within a few percent of optimum - if we are allowed to
change the operating voltage. I do, however, agree that it
would not be worth if from an economic point of view to
develop a disposable voltage converter for incandescent
lamps.

Someone did try to put a diode in the base of each lamp to
reduce the RMS voltage from 120 volts to 84.9 volts. This
does increase efficacy at low cost, and if half the diodes
are inserted one way, while the other half are inserted with
opposite polarity, there should be no net effect on the
power grid or metering. However, this option opens the door
for crafty people to select lamps with all the same polarity
and hence get part of their power for free, so this idea was
dropped, I believe under pressure from the power companies.


Traditionally, AC has been thought superior to DC operation of incandescent
lamps because so-called filament "notching" can occurr on dc plus if there
is any moisture present in the base/seal area, metal can electrolytically
move from one line to another and cause seal or line failure.

So, life with AC is better than with DC, but the switch from
one to the other does not effect efficacy. In fact, the RMS
voltage of an AC waveform is defined as the DC voltage that
gives the same heating power - and we all know that
incandescent lamps are just heaters that happen to generate
a bit of light.


Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

I found no flicker from sunshine


You probably didn't wait long enough :-) The sun is known to
be a variable star. Data clearly shows reduction in output
near 1550 and another near 1700. Plus, there is the 11-year
sunspot cycle that has minor influence on the output of the
sun.


and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Could that be true? It indicates that the filament temperature of
a bulb run on 60 Hz AC heats and cools significantly 120 times a
second. With DC, wouldn't filament temperature stay constant?
Wouldn't less peak voltage be required for a given amount of light?


While typical incandescent lamps used in the US are
considered to be flicker-free there is obviously some
variation to the visible light output. Lower mass filaments
will obviously have more flicker than higher mass filaments,
so the amount of flicker depends upon the lamp power, the
operating voltage and the operating frequency plus other
factors.

A 100-watt 120-volt lamp will have less flicker than a
100-watt 240-volt lamp operating at the same frequency. A
40-watt 240-volt lamp will have more flicker, and if run on
50 Hz instead of 60 Hz it will have even more. I believe
that early hydroelectric power systems in the US, such as
Niagara Falls, generated power at 25 Hz and there was
significant visible flicker from (probably low power)
incandescent lamps used at the time.

One reference I found

http://www.epri-peac.com/tutorials/brf36tut.html

gives the thermal time constant of a 120-volt incandescent
lamp with a "typical" but unspecified power as 28
milliseconds and the thermal time constant of a 230-volt
lamp of the same power as 19 milliseconds. However, this
data is not useful by itself. Total radiation varies as T^4
and visible radiation, which is just the short wavelength
end of the SPD, will vary even faster with filament
temperature, so thermal time constants are of little value
unless the temperature is used to calculate visible
radiation. Note that the data at the link above shows that
even at 20 Hz the flicker perception of the lamps they
tested was far lower than the flicker perception of
fluorescent lamps operated at the same frequency.

What was the operating voltage and power of the lamp you
tested?


If there is significant flicker and temperatue change with AC,
wouldn't it be worse with a half-wave rectifier?


Much worse. The idea was proposed for a 100-watt, 85-volt
lamp operating at 60 Hz, which would reduce flicker a bit,
but there may still be flicker problems.


Purely a comment, but the last time I half waved a 240V 100W light
bulb, the bulb exploded within about 5 minutes. I may have been just
unlucky, but my impression was that the filament vibrated badly and then
shorted, before the explosion.

Regards
Capitol

In article 1134601103.507857@athnrd02,
"Ioannis" wrote:

"Andrew Gabriel" wrote in message
...
[snip]

BTW, here's a nice experiment you can carry out to observe this
effect in a fluorescent lamp. Take a lamp firmly fixed to a
long cord (such as a car service/inspection lamp), and go out
into a large dark area (e.g. outside at night) where there are
no objects for many feet in any direction. Switch the lamp on,
and swing it round and round over your head on the end of the
cord. As it passes in front of you each time, you will see the
stroboscopic effect of the different colour components which
make up the white light, and in particular you will notice how
they are all out of phase with each other, with some of the
phosphor components having much longer persistance than others.
Obviously be careful here -- if you manage to hurl a car
inspection lamp through your neighbour's window, don't come
crying to me...

For crying out loud, Andrew! Couldn't you think of a simpler way than this?

Like, for example, reflect the light of the fluorescent off the convex side
of a large spoon and swing the spoon a little bit?

Your are giving the previous poster reasons to do some serious damage,
particularly if he tries it with a Chinese "CE certified" fluorescent chord
luminaire!

Never mind what the police will think if they see a guy in the dark swinging
a fluorescent tube:

"What are you doing there?"

"I'm trying to observe the stroboscopic effect..."

"The WHAT?!"

"You know, when the light goes on and off at 120 Hz, and the phosphors have
this persistence, see, and you can...by rotating FAST the lamp..."

"Arrest him. He is dangerous"...

--
Andrew Gabriel

Look at the lamp through the blades of a variable speed
fan also color crt's and other displays. Do this inside to
avoid trouble with the police.
--
jimmy mac
add another zero to the other zero for e-mail

Victor Roberts wrote:

On Tue, 13 Dec 2005 19:20:58 -0500, Sawney Beane
wrote:



Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.


and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Could that be true? It indicates that the filament temperature of
a bulb run on 60 Hz AC heats and cools significantly 120 times a
second. With DC, wouldn't filament temperature stay constant?
Wouldn't less peak voltage be required for a given amount of light?

While typical incandescent lamps used in the US are
considered to be flicker-free there is obviously some
variation to the visible light output. Lower mass filaments
will obviously have more flicker than higher mass filaments,
so the amount of flicker depends upon the lamp power, the
operating voltage and the operating frequency plus other
factors.

A 100-watt 120-volt lamp will have less flicker than a
100-watt 240-volt lamp operating at the same frequency. A
40-watt 240-volt lamp will have more flicker, and if run on
50 Hz instead of 60 Hz it will have even more. I believe
that early hydroelectric power systems in the US, such as
Niagara Falls, generated power at 25 Hz and there was
significant visible flicker from (probably low power)
incandescent lamps used at the time.

One reference I found

http://www.epri-peac.com/tutorials/brf36tut.html

gives the thermal time constant of a 120-volt incandescent
lamp with a "typical" but unspecified power as 28
milliseconds and the thermal time constant of a 230-volt
lamp of the same power as 19 milliseconds. However, this
data is not useful by itself. Total radiation varies as T^4
and visible radiation, which is just the short wavelength
end of the SPD, will vary even faster with filament
temperature, so thermal time constants are of little value
unless the temperature is used to calculate visible
radiation. Note that the data at the link above shows that
even at 20 Hz the flicker perception of the lamps they
tested was far lower than the flicker perception of
fluorescent lamps operated at the same frequency.

I don't think there was much voltage fluctuation except the 120 Hz
p-p frequency of 60 Hz AC.

The 28 ms tc for a 120V incandescent bulb is probably mostly for
the reddish end of the spectrum, where most of the energy is. My
measurement was mostly in the green-yellow area, where the CS
photocell and the human eye are most sensitive. That's a hotter
color, so I suppose the tc would be shorter.

I suppose most of the light from a fluorescent tube comes not
directly from the arc but from the phosphors, so the tc of the
phosphors must be important. Also, I think I measured four-tube
fixtures with milky-plastic diffusers. If a fixture has more than
one tube, I think the ballast is designed to reduce the time
between peaks from 8.3 ms (as with an incandescent bulb at 60 Hz
AC) to 4.2 ms.

What was the operating voltage and power of the lamp you
tested?

I checked several. All were 120 AC. The smallest was 15 W. I
found it made a much better reading light fed through a full-wave
rectifier with a filter capacitor. I don't know how much of the
improvement was from higher intensity, how much from whiter color,
and how much from reduced flicker.

Victor Roberts wrote:

On Tue, 13 Dec 2005 19:20:58 -0500, Sawney Beane
wrote:


Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

I found no flicker from sunshine and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Could that be true? It indicates that the filament temperature of
a bulb run on 60 Hz AC heats and cools significantly 120 times a
second. With DC, wouldn't filament temperature stay constant?
Wouldn't less peak voltage be required for a given amount of light?

There is some very interesting flicker data in the IES
Handbook (2000) - where I should have looked in the first
place. This data supports the perception that typical
incandescent lamps used for general lighting at 120 volts
and 60 Hz do not produce noticeable flicker.

"Incandescent lamps operated below 25 Hz will produce
perceptible flicker and can create a stroboscopic effect.
Flicker will be less from an incandescent source if it has a
larger filament and is operated at a higher wattage and at a
higher supply frequency. Modern incandescent light sources
operated at 60 Hz do not produce noticeable flicker, nor a
stroboscopic effect, to the human eye. The flicker index of
several incandescent lamps operated at 25 Hz and 60 Hz is
shown in Figure 6-16. Consult Chapter 2, Measurement of
Light and Other Radiant Energy, for more information about
lamp flicker."

And here is their data: (To see the table correctly you will
have to use a fixed font instead of a variable font.

Watts Percent Flicker Flicker Index
60 Hz 25 Hz 60 Hz 25 Hz
6* 29 69 0.092 0.220
10* 17 40 0.054 0.127
25* 10 28 0.032 0.089
40+ 13 29 0.041 0.092
60# 8 19 0.025 0.060
100# 5 14 0.016 0.045
200+ 4 11 0.013 0.035
300+ 3 8 0.010 0.025
500+ 2 6 0.006 0.019
1000+ 1 4 0.003 0.013

* Vacuum
+ Coiled-coil filament
# Gas-filled

The symbols are a bit confusing since I believe that 60 watt
lamps and above have both coiled-coils and gas filling,
though the table does not show that. Also remember that the
data above is for 120-volt lamps.

Here is the official description of the Flicker Index from
the 2000 IESNA Lighting Handbook:

"The flicker index has been established as a reliable
relative measure of the cyclic variation in output of vari-
ous sources at a given power frequency. It takes into
account the waveform of the light output as well as its
amplitude. It is calculated by dividing the area above the
line of average light output by the total area under the
light output curve for a single curve. [The area below the
line of average light output] may be close to zero if light
output varies as periodic spikes.

The flicker index assumes values from 0 to 1.0, with 0 for
steady light output. Higher values indicate in increased
possibility of noticeable stroboscopic effect, as well as
lamp flicker."

I think I see. Suppose you were in a gallery shining a light on a
stage and you spun a sort of airplane propeller in front of the
light so that it totally blocked the light through 10% of each
revolution. The average would be .9 and the flicker index 10/9.

Now suppose you spun a black disk in front the light with a hole on
each side of the center so that it let light through for 10% of
each revolution. The average would be .1 and the flicker index 10.

In each case, the light would alternate between 0 and 1. My
photocell would read the same "flicker" if its response were fast
enough, but the flicker index would be nine times higher for one
than the other.

Andrew Gabriel wrote:

In article ,
Sawney Beane writes:

Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

You need to be much more precise here. I don't know the
characteristics of a CdS, but those of the human eye are
not useful here, as the limiting factor is the human brain.

We can read better with a certain intensity of green light than the
same intensity of red light because we see green light better.
Because the CS cell reacts like the human eye in its relative
sensitivity to the various colors, it can show how much "working
light" is available. By "flicker" I meant a fluctuation in the
amount of working light, not a human perception of fluctuation.

A human eye will transmit flicker to the brain at well over
100Hz, but the human brain can't work that fast -- it's too
big. The upper range of flicker visible varies by person,
but is between 55Hz and 70Hz. A fly's brain can work much
faster, being much smaller, so a fly can see flicker at
much higher speeds (~1000Hz IIRC). It may be that our
ancestor's smaller brains were faster and matched to the
speed of human eyes many years ago, but this turned out to
be less of an evolutionary advantage than a bigger brain.

Is the ability to see flicker determined by brain size? For a
human hunter, it may be important to ignore the movement of foliage
in the wind and perceive the image of the deer behind the foliage,
evident through a hundred tiny, "flickering" holes. A fly, OTOH,
may have a millisecond to evade a predator in flight.

The cones, most dense at the center of vision, are used for
watching foliage for a deer, for example. The rods, more dense at
the periphery, seem more sensitive to flicker. Isn't it from the
corner of the eye that one is likely to notice the flicker of a
fluorescent tube? The human may have to respond fastest to danger
from the sides.


Incandescent lamps running on 50 or 60Hz will be flickering
at 100 or 120Hz respectively (if they are flickering at all),
which is well above the human perception level.



I found no flicker from sunshine and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Sounds a bit doubtful to me, but maybe not impossible.
Fluorescent lamp flicker is much more complex. The light from
a fluorescent lamp comes from multiple different sources, i.e.
several different phosphors generating different colours, and
the gas discharge itself generating some prominant lines.
The gas discharge is going to have quite a pronounced flicker,
switching on and off at twice the line frequency. For the
phosphors, they all tend to have different persistance, some
reds for example, having a persistance which will maintain
light output over the dark periods from the discharge. So if
the CdS cell is particularly sensitive to the light from those
red phosphors, it's going to see a lot less flicker than if it
is more sensitive to one of the gas discharge lines.

It's most sensitive to yellow-green. Cool white is strong in that color.


BTW, here's a nice experiment you can carry out to observe this
effect in a fluorescent lamp. Take a lamp firmly fixed to a
long cord (such as a car service/inspection lamp), and go out
into a large dark area (e.g. outside at night) where there are
no objects for many feet in any direction. Switch the lamp on,
and swing it round and round over your head on the end of the
cord. As it passes in front of you each time, you will see the
stroboscopic effect of the different colour components which
make up the white light, and in particular you will notice how
they are all out of phase with each other, with some of the
phosphor components having much longer persistance than others.
Obviously be careful here -- if you manage to hurl a car
inspection lamp through your neighbour's window, don't come
crying to me...

--
Andrew Gabriel

On Thu, 15 Dec 2005 04:12:52 -0500, Sawney Beane
wrote:

Victor Roberts wrote:

On Tue, 13 Dec 2005 19:20:58 -0500, Sawney Beane
wrote:


Years ago I used a cadmium sulfide photocell to check flicker.
IIRC, I put the photocell in series with a resistor, powered the
circuit with a flashlight cell, and monitored voltage across the
photocell. IIRC, the wavelength/response profile for the photocell
was similar to that of the human eye.

I found no flicker from sunshine and more flicker from an
incandescent lamp than from a fluorescent fixture with a magnetic ballast.

Could that be true? It indicates that the filament temperature of
a bulb run on 60 Hz AC heats and cools significantly 120 times a
second. With DC, wouldn't filament temperature stay constant?
Wouldn't less peak voltage be required for a given amount of light?

There is some very interesting flicker data in the IES
Handbook (2000) - where I should have looked in the first
place. This data supports the perception that typical
incandescent lamps used for general lighting at 120 volts
and 60 Hz do not produce noticeable flicker.

"Incandescent lamps operated below 25 Hz will produce
perceptible flicker and can create a stroboscopic effect.
Flicker will be less from an incandescent source if it has a
larger filament and is operated at a higher wattage and at a
higher supply frequency. Modern incandescent light sources
operated at 60 Hz do not produce noticeable flicker, nor a
stroboscopic effect, to the human eye. The flicker index of
several incandescent lamps operated at 25 Hz and 60 Hz is
shown in Figure 6-16. Consult Chapter 2, Measurement of
Light and Other Radiant Energy, for more information about
lamp flicker."

And here is their data: (To see the table correctly you will
have to use a fixed font instead of a variable font.

Watts Percent Flicker Flicker Index
60 Hz 25 Hz 60 Hz 25 Hz
6* 29 69 0.092 0.220
10* 17 40 0.054 0.127
25* 10 28 0.032 0.089
40+ 13 29 0.041 0.092
60# 8 19 0.025 0.060
100# 5 14 0.016 0.045
200+ 4 11 0.013 0.035
300+ 3 8 0.010 0.025
500+ 2 6 0.006 0.019
1000+ 1 4 0.003 0.013

* Vacuum
+ Coiled-coil filament
# Gas-filled

The symbols are a bit confusing since I believe that 60 watt
lamps and above have both coiled-coils and gas filling,
though the table does not show that. Also remember that the
data above is for 120-volt lamps.

Here is the official description of the Flicker Index from
the 2000 IESNA Lighting Handbook:

"The flicker index has been established as a reliable
relative measure of the cyclic variation in output of vari-
ous sources at a given power frequency. It takes into
account the waveform of the light output as well as its
amplitude. It is calculated by dividing the area above the
line of average light output by the total area under the
light output curve for a single curve. [The area below the
line of average light output] may be close to zero if light
output varies as periodic spikes.

The flicker index assumes values from 0 to 1.0, with 0 for
steady light output. Higher values indicate in increased
possibility of noticeable stroboscopic effect, as well as
lamp flicker."

I think I see. Suppose you were in a gallery shining a light on a
stage and you spun a sort of airplane propeller in front of the
light so that it totally blocked the light through 10% of each
revolution. The average would be .9 and the flicker index 10/9.

Now suppose you spun a black disk in front the light with a hole on
each side of the center so that it let light through for 10% of
each revolution. The average would be .1 and the flicker index 10.

In each case, the light would alternate between 0 and 1. My
photocell would read the same "flicker" if its response were fast
enough, but the flicker index would be nine times higher for one
than the other.

The IESNA Lighting Handbook does not define Percent Flicker,
only Flicker Index. We know that Flicker Index is based on
both the magnitude and shape of the light output with time,
so I'm going to assume (until corrected by those here who
know better) that Percent Flicker is based only on maximum
and minimum values of the light. If Percent Flicker varies
from 0 to 100% and depends upon the maximum and minimum
values, then it can be expressed as (Maximum Value - Minimum
Value)/Maximum Value. Using this definition both of your
examples have 100% Percent Flicker since they go completely
off.

Your use of the Flicker Index is upside down, since Flicker
Index varies from 0 to 1. It cannot be 1.1 or 10. Flicker
Index is a function of the shape of the light modulation
curve, which I don't know in detail for your examples. Since
you are using a slotted disk of some sort, I'm going to
assume that the light modulation waveform is rectangular and
looks like a pulse-width modulated waveform. See graph
below: Also - Do you realize you are probably violating
one of Color Kinetics many patents ? :-)


--------- ----------------- -----------
| | | |
| | | |
| | | |
--------- ---------

For the example where the light is blocked 10% of the time,
the average light value is 90% of the peak and the area of
the curve above the average is 10% of the total area under
the curve. The Flicker Factor is therefore 0.1.

For the example where the light is blocked 90% of the time,
the average light value is 10% of the peak and the area of
the curve above the average value is 90% of the total area
under the curve. The Flicker Index is therefore 0.9.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

Victor Roberts wrote:



The IESNA Lighting Handbook does not define Percent Flicker,
only Flicker Index. We know that Flicker Index is based on
both the magnitude and shape of the light output with time,
so I'm going to assume (until corrected by those here who
know better) that Percent Flicker is based only on maximum
and minimum values of the light. If Percent Flicker varies
from 0 to 100% and depends upon the maximum and minimum
values, then it can be expressed as (Maximum Value - Minimum
Value)/Maximum Value. Using this definition both of your
examples have 100% Percent Flicker since they go completely
off.

Your use of the Flicker Index is upside down, since Flicker
Index varies from 0 to 1. It cannot be 1.1 or 10. Flicker
Index is a function of the shape of the light modulation
curve, which I don't know in detail for your examples. Since
you are using a slotted disk of some sort, I'm going to
assume that the light modulation waveform is rectangular and
looks like a pulse-width modulated waveform. See graph
below: Also - Do you realize you are probably violating
one of Color Kinetics many patents ? :-)

Uh-oh, I must have stayed up too late. Well, I'll remember it
better now than if I'd gotten it right the first time.

Ioannis wrote:


Your are giving the previous poster reasons to do some serious damage,
particularly if he tries it with a Chinese "CE certified" fluorescent chord
luminaire!

Never mind what the police will think if they see a guy in the dark swinging
a fluorescent tube:

"What are you doing there?"

"I'm trying to observe the stroboscopic effect..."

"The WHAT?!"

"You know, when the light goes on and off at 120 Hz, and the phosphors have
this persistence, see, and you can...by rotating FAST the lamp..."

"Arrest him. He is dangerous"...


"Car Talk" is a syndicated radio show in which the Tappet Brothers,
Click and Clack, answer questions about automotive mechanics. Each
week they read a brain teaser. One week they gave the number of
inches between railroad rails in America and asked how that had
become the standard gage.

There are different parts of a rail to measure from, so I took a
steel tape to measure the track alongside the municipal parking
lot. While I was there, the crossing arms came down and traffic
backed up and no train came.

I went home, thought it over, and returned to check my
measurements. A railroad truck turned in, raced across the parking
lot, and screeched to a stop. A mean-looking railroad man jumped
out and demanded to know what I thought I was doing. I nervously
began my explanation, "Well, Click and Clack said..." Uh-oh, I'd
really put my foot in my mouth! I realized most people had never
heard of Click and Clack.

The following week, the Tappet Brothers announced the answer: early
railroaders had decided that their cars should have the same
wheelbase as Roman chariots. What a myth! I almost went to the
funny farm for a brain teaser that was beneath contempt.

On Fri, 16 Dec 2005, Sawney Beane wrote:

"Car Talk" is a syndicated radio show in which the Tappet Brothers,
Click and Clack, answer questions about automotive mechanics.

No, it's an NPR radio show in which those two buffoons give reliably
incorrect car advice in between drunken-bum guffaws at their own dumb
jokes.

"Daniel J. Stern" wrote in message
n.umich.edu...
On Fri, 16 Dec 2005, Sawney Beane wrote:

"Car Talk" is a syndicated radio show in which the Tappet Brothers,
Click and Clack, answer questions about automotive mechanics.

No, it's an NPR radio show in which those two buffoons give reliably
incorrect car advice in between drunken-bum guffaws at their own dumb
jokes.

Well, they did one good thing at least.

I met my a woman via their web site who later became my wife -- some seven
years ago now . When we decided to get married they sent some neat (well,
typically odd) gifts for our wedding.

Terry McGowan

"Sawney Beane" wrote in message
...
Ioannis wrote:


Your are giving the previous poster reasons to do some serious damage,
particularly if he tries it with a Chinese "CE certified" fluorescent
chord
luminaire!

Never mind what the police will think if they see a guy in the dark
swinging
a fluorescent tube:

"What are you doing there?"

"I'm trying to observe the stroboscopic effect..."

"The WHAT?!"

"You know, when the light goes on and off at 120 Hz, and the phosphors
have
this persistence, see, and you can...by rotating FAST the lamp..."

"Arrest him. He is dangerous"...


"Car Talk" is a syndicated radio show in which the Tappet Brothers,
Click and Clack, answer questions about automotive mechanics. Each
week they read a brain teaser. One week they gave the number of
inches between railroad rails in America and asked how that had
become the standard gage.

There are different parts of a rail to measure from, so I took a
steel tape to measure the track alongside the municipal parking
lot. While I was there, the crossing arms came down and traffic
backed up and no train came.

I went home, thought it over, and returned to check my
measurements. A railroad truck turned in, raced across the parking
lot, and screeched to a stop. A mean-looking railroad man jumped
out and demanded to know what I thought I was doing. I nervously
began my explanation, "Well, Click and Clack said..." Uh-oh, I'd
really put my foot in my mouth! I realized most people had never
heard of Click and Clack.

The following week, the Tappet Brothers announced the answer: early
railroaders had decided that their cars should have the same
wheelbase as Roman chariots. What a myth! I almost went to the
funny farm for a brain teaser that was beneath contempt.

Well, you've probably figured out that your steel tape completed a circuit
between the two rails within a "block" (an electrically isolated stretch of
rails that controls a set of signals). The circuit is powered by batteries,
but I've forgotten the battery voltage. However, it's not enough to cause
electrocution should you straddle the rails with bare feet. If you look at
the rail joints, you will see a braided wire fastened to each side so the
circuit is continuous and reliable. The system has been used for many years
and is standard in the U.S. Today, there's probably a line to a computer
somewhere that indicates which blocks are active (indicating the presence of
a train or a fault. Maybe that's what brought the railroad truck and its
hostile occupant to check you out.

Terry McGowan

On Sat, 17 Dec 2005 02:23:17 GMT, "TKM"
wrote:

I met my a woman via their web site who later became my wife -- some seven
years ago now . When we decided to get married they sent some neat (well,
typically odd) gifts for our wedding.

Terry McGowan

It's quite amazing what you can learn from newsgroups about
people you think you know :-) Congratulations!

Vic
--
Vic Roberts
Replace xxx with vdr in e-mail address.

"Daniel J. Stern" wrote:

On Fri, 16 Dec 2005, Sawney Beane wrote:

"Car Talk" is a syndicated radio show in which the Tappet Brothers,
Click and Clack, answer questions about automotive mechanics.

No, it's an NPR radio show in which those two buffoons give reliably
incorrect car advice in between drunken-bum guffaws at their own dumb
jokes.

I have not found their advice or their brain teasers to be reliably
incorrect. That's why they've taken me in so many times.

Our RR gage came from the width of Roman chariots? (I wrongly
called the width the wheelbase.) The evidence for the myth is that
ruts in the Roman pavement coming out of a stone quarry are as far
apart as modern rails. Saying that was the width of chariots is
like saying jeeps and humvees have the same width as each other and
as eighteen-wheelers.

Maybe each of the early railroad builders used a different Roman
chariot as his gage, and that's why there were so many widths.
They may have been relatives of Click and Clack.

The outside measurement of modern rails is very close to five feet.
I think the original specificaton, in the days of wooden rails,
was for wheels five feet apart at the outside. Wheels and rails
evolved, but new wheels had to fit old rails and new rails had to
fit old wheels. I think that evolution is why the outside
measurement is slightly different from five feet nowadays.

TKM wrote:

"Sawney Beane" wrote in message
...


There are different parts of a rail to measure from, so I took a
steel tape to measure the track alongside the municipal parking
lot. While I was there, the crossing arms came down and traffic
backed up and no train came.

I went home, thought it over, and returned to check my
measurements. A railroad truck turned in, raced across the parking
lot, and screeched to a stop. A mean-looking railroad man jumped
out and demanded to know what I thought I was doing. I nervously
began my explanation, "Well, Click and Clack said..." Uh-oh, I'd
really put my foot in my mouth! I realized most people had never
heard of Click and Clack.

The following week, the Tappet Brothers announced the answer: early
railroaders had decided that their cars should have the same
wheelbase as Roman chariots. What a myth! I almost went to the
funny farm for a brain teaser that was beneath contempt.

Well, you've probably figured out that your steel tape completed a circuit
between the two rails within a "block" (an electrically isolated stretch of
rails that controls a set of signals). The circuit is powered by batteries,
but I've forgotten the battery voltage. However, it's not enough to cause
electrocution should you straddle the rails with bare feet. If you look at
the rail joints, you will see a braided wire fastened to each side so the
circuit is continuous and reliable. The system has been used for many years
and is standard in the U.S. Today, there's probably a line to a computer
somewhere that indicates which blocks are active (indicating the presence of
a train or a fault. Maybe that's what brought the railroad truck and its
hostile occupant to check you out.

Terry McGowan

I was a little self-conscious measuring the rails because I figured
it was trespassing, technically. So when the truck raced up I was
embarrassed and startled that I'd drawn such a response. The
driver hadn't shaved and reminded me of the guard who clubbed Cool
Hand Luke into the grave-sized hole.

When he asked if my tape was steel, I caught on. I had read
somewhere about the signal voltage in rails. That made it worse
because now I couldn't honestly claim ignorance. If anything could
have made the situation more embarrassing, it was to realize I had
started explaining about my invisible friends, Click and Clack, who
had told me to do it.

The crossing a few yards from where I measured is notorious because
the gates often come down when there is no train. If they stay
down, the railroad may take 45 minutes to respond. I wonder why
they can't master the technology.

There's also a squashed head near where I measured. I think that's
what it's called. It starts when an engineer spins his wheels,
which overheats and gouges the rail. Then the damaged area becomes
a sort of pothole. When steel wheels hit it, the racket is
unpleasant half a mile away. It shortens the life of the wheels,
but the railroad doesn't bother to replace the rail.