I heard from many girls that size doesn't matter !! LOL

DaveC a écrit :
Oh, smarter-than-I people,

http://imgur.com/WPEoOu1

The 2 belt-drive capstan flywheels in an auto-reverse cassette mechanism are
different sizes. (Motor drive pulley will be in the small loop end of the
belt in illustration above.)

How does that result in the same tape speed in both directions?

Confused...

On Sun, 13 Mar 2016 15:34:07 -0000, MJC
wrote:

In article ,
says...

I can't think of a single method of 'reproducing sound' that doesn't
involve mechanical means.

Sound is a mechanical phenomenon. Humans use flapping meat.

I can imagine a method that used heat to move the air, perhaps with a
plasma to make it fast. (Like a modulated lightning flash.) But I cannot
be bothered to construct a search to find out if it has been done
successfully...

See Thermoachoustic Technology.

www.lanl.gov/thermoacoustics/Pubs/

RL

On 13/03/2016 16:22, Don Bruder wrote:
In article ,
MJC wrote:

In article ,
says...

I can't think of a single method of 'reproducing sound' that doesn't
involve mechanical means.

Sound is a mechanical phenomenon. Humans use flapping meat.

I can imagine a method that used heat to move the air, perhaps with a
plasma to make it fast. (Like a modulated lightning flash.) But I cannot
be bothered to construct a search to find out if it has been done
successfully...

Mike.

I recall a conversation from years ago with a *VERY* old theater
projectionist, who spoke of what he called "flame speakers". Don't know
if it was an artifact of his (at the time) 80+ year old mind going, or
reality, but what he described made sense to me on several levels,
though I've never bothered to try chasing it down. Apparently, back in
the early days of talkies, one method of sound production involved a gas
nozzle (unsure if he meant gasoline, or something like propane/LP gas)
"tuned" to produce a blue flame (he was very clear on that point - lots
of the conversation came back to how he had to tinker with the flame at
each showing, otherwise the sound wasn't good) several feet tall in a
combustion chamber, into which was shoved a set of tungsten electrodes.
The 'trodes were driven at high voltages by any of several amplification
methods (frequently varying by theater, if the old guy's tale was to be
believed) to charge the plasma of the flame, which apparently caused it
to "dance", driving a diaphragm like that of a speaker. Supposedly,
amazingly high volumes with very good fidelity could be achieved.

Like I say, I've never actually gone to the effort of tracking it down,
and I have no idea if it was a failing mind's invention, or reality,
but... shrug Seems to me like it COULD work.


Wasn't there some scheme to generate sound for large area advertising by
using aurora? presumably someone realised polar bears don't buy much stuff.

In article ,
says...

"I can imagine a method that used heat to move the air, perhaps with a
plasma to make it fast. "

The singing arc.

However it depends on how you want to be about this. If someone want no moving parts that is fine and the singing arc works for that.

But your eardrum still moves as well as the linage from it to the cochlea.

Plus the fact that the air itself moves.

That recalls some old saw about whether anything is real if not
observed. I think sound has been reproduced even if no-one hears.

As to moving air counting as a "part"... In space no-one can hear
spurious arguments!

Mike.

On 14/03/2016 02:34, MJC wrote:
In article ,
says...

I can't think of a single method of 'reproducing sound' that doesn't
involve mechanical means.

Sound is a mechanical phenomenon. Humans use flapping meat.

I can imagine a method that used heat to move the air, perhaps with a
plasma to make it fast. (Like a modulated lightning flash.) But I cannot
be bothered to construct a search to find out if it has been done
successfully...

Mike.


http://www.roger-russell.com/ionovac...c.htm#ionofane
http://www.ebay.com/itm/171837115818

On Saturday, March 12, 2016 at 11:16:48 AM UTC-5, DaveC wrote:
wrote:

The capstan is a passive device. The motor pulley diameter via the *pinch
roller* determines the tape speed. The capstan wheel can be any size at all.

By my mind that is backward: the pinch roller is passive (not being driven).
The capstan shaft (~2mm diam) is driven by capstan flywheel/belt/motor
pulley.

No?

Thanks.

(op)

THE *MOTOR PULLEY* DIAMETER..... Not the pinch roller.

Peter Wieck
Melrose Park, PA

On 14/03/2016 17:27, legg wrote:
On Mon, 14 Mar 2016 07:04:19 -0700 (PDT), "
wrote:

On Saturday, March 12, 2016 at 11:16:48 AM UTC-5, DaveC wrote:
wrote:

The capstan is a passive device. The motor pulley diameter via the *pinch
roller* determines the tape speed. The capstan wheel can be any size at all.

By my mind that is backward: the pinch roller is passive (not being driven).
The capstan shaft (~2mm diam) is driven by capstan flywheel/belt/motor
pulley.

No?

Thanks.

(op)

THE *MOTOR PULLEY* DIAMETER..... Not the pinch roller.

Peter Wieck
Melrose Park, PA

Question was re flywheel diameter differences. Motor pulley drives
both. Same belt on two different dia flywheels, yet obtains same
spindle rotation at their separate pinch rollers.

Identical belt speed should drive a smaller dia flywheel faster. Motor
speed does not account for this physical difference, as it is uniform
for both functions.

Supposition is that the difference in flywheel dia is related to belt
thickness, as one flywheel is inside, and other is outside the drive
belt loop.

RL


That would be lead to a much closer pair of pulley diameters.
But then although you have a free range of pulley sizes, as cast and
machined, the sintered metal bearings come in only discrete sizes of * x
0.1mm , so you have to increase/decrease the pulley diameter ratio to
then be compatible to 2 available bearing diameters and hence spindle
diameters.
That is the reason i'd go for

On Mon, 14 Mar 2016 07:04:19 -0700 (PDT), "
wrote:

On Saturday, March 12, 2016 at 11:16:48 AM UTC-5, DaveC wrote:
wrote:

The capstan is a passive device. The motor pulley diameter via the *pinch
roller* determines the tape speed. The capstan wheel can be any size at all.

By my mind that is backward: the pinch roller is passive (not being driven).
The capstan shaft (~2mm diam) is driven by capstan flywheel/belt/motor
pulley.

No?

Thanks.

(op)

THE *MOTOR PULLEY* DIAMETER..... Not the pinch roller.

Peter Wieck
Melrose Park, PA

Question was re flywheel diameter differences. Motor pulley drives
both. Same belt on two different dia flywheels, yet obtains same
spindle rotation at their separate pinch rollers.

Identical belt speed should drive a smaller dia flywheel faster. Motor
speed does not account for this physical difference, as it is uniform
for both functions.

Supposition is that the difference in flywheel dia is related to belt
thickness, as one flywheel is inside, and other is outside the drive
belt loop.

RL

On 14 Mar 2016, N_Cook wrote
(in article ):

That would be lead to a much closer pair of pulley diameters.
But then although you have a free range of pulley sizes, as cast and
machined, the sintered metal bearings come in only discrete sizes of * x
0.1mm , so you have to increase/decrease the pulley diameter ratio to
then be compatible to 2 available bearing diameters and hence spindle
diameters.
That is the reason i'd go for

I (op) have accepted the theory that difference is to avoid additive
resonance of the capstan shafts in bronze(?)--not ball--bearings. Difference
flywheel sizes plus different capstan shaftssizes (2mm and 2.1mm) results in
same tape speed (in opposite directions--this is an auto-reverse mechanism)
and different resonances.

On Monday, March 14, 2016 at 12:28:26 PM UTC-4, legg wrote:

Question was re flywheel diameter differences. Motor pulley drives
both. Same belt on two different dia flywheels, yet obtains same
spindle rotation at their separate pinch rollers.

Identical belt speed should drive a smaller dia flywheel faster. Motor
speed does not account for this physical difference, as it is uniform
for both functions.

Supposition is that the difference in flywheel dia is related to belt
thickness, as one flywheel is inside, and other is outside the drive
belt loop.

Um... A flywheel is a momentum device attached to a system to provide smoothing. Many (very much most) DC motors are pulse driven. The flywheel removes these pulses. Tape speed is determined by the capstan motor pulley diameter. FULL STOP.

Peter Wieck
Melrose Park, PA

On Mon, 14 Mar 2016 11:41:28 -0700 (PDT), "
wrote:

On Monday, March 14, 2016 at 12:28:26 PM UTC-4, legg wrote:

Question was re flywheel diameter differences. Motor pulley drives
both. Same belt on two different dia flywheels, yet obtains same
spindle rotation at their separate pinch rollers.

Identical belt speed should drive a smaller dia flywheel faster. Motor
speed does not account for this physical difference, as it is uniform
for both functions.

Supposition is that the difference in flywheel dia is related to belt
thickness, as one flywheel is inside, and other is outside the drive
belt loop.

Um... A flywheel is a momentum device attached to a system to provide smoothing. Many (very much most) DC motors are pulse driven. The flywheel removes these pulses. Tape speed is determined by the capstan motor pulley diameter. FULL STOP.

In these machines a single motor with a pulley on its shaft, drives
the outer rims of the two differently sized flywheels, through a
single belt.

I've measured the spindles at the pinch rollers and they are a
different diameter, as was suggested by DaveC, so belt thickness isn't
responsible for compensation of the flywheel sizes - the spindles are
scaled with the flywheel diameter.

Never occurred to me to wonder about this, before, or to check it out.
Happy just to keep them going.

RL

N_Cook wrote:



Supposition is that the difference in flywheel dia is related to belt
thickness, as one flywheel is inside, and other is outside the drive
belt loop.

RL


That would be lead to a much closer pair of pulley diameters.


** The supposition is nonsense.

Where the drive belt is curved, the outside radius is greater - but both flywheels are on the INSIDE of curves.


..... Phil

to the op..



only one pinch roller is engaged at a time, depending upon which direction the tape is traveling?

so the two flywheels turn in opposite directions?

How do they get the second flywheel to spin in the opposite direction?

Maybe that has something to do with the need for a different size?

M

On Tuesday, March 15, 2016 at 9:29:42 AM UTC-4, wrote:

Maybe that has something to do with the need for a different size?

Mpfffff... Let's get down to it.

The most likely reason the two similar-function parts are of a different size is that the physical parameters of the entirety suggested/led to this decision. As neither have *one damned thing* to do with the actual tape speed, the reasons may be no more complex than that.

Peter Wieck
Melrose Park, PA

wrote:


so the two flywheels turn in opposite directions?

How do they get the second flywheel to spin in the opposite direction?


** Look at the diagram - the belt goes most of the way around the larger flywheel ( 153 ) but only a small part of the way around the smaller one ( 152).

IOW it fits where the "151" is shown, where the belt is curved the opposite way.


..... Phil

only one pinch roller is engaged at a time, depending upon which direction
the tape is traveling?

Yes
so the two flywheels turn in opposite directions?

Yes
How do they get the second flywheel to spin in the opposite direction?

look at the diagram (in the original post). The Belt goes around the 2
flywheels such that the belts are driven in opposite directions.
Maybe that has something to do with the need for a different size?

M

Flywheels are differentdiameters AND capstan spindles (pressed into the
center of the flywheels) are different diameters. The flywheel/spindle
diameters are calculated such that the resulting tape speed is the same for
both, only in opposite directions (one for Side A, one for Side B).

The reason for the differences, it seems, is to help avoid (or minimize)
resonant frequency set up by the spindles turning in their bearings.
Different diameters/speeds = lower resonance.

(op)

So let me get this straight. The consensus now is that it has nothing to do with the thickness of the belt but is to avoid resonance, Logically resulting in less wow and flutter I would assume.

Interesting. I remember the old Walkmans that had two flywheels going in opposite directions, not for autoreverse, but so that when the unit was moved, turned whatever, it would maintain the speed. But in that case of course the two flywheels were the same weight and diameter so the angular forces would cancel out.

Really, on the surface is seemed that the thickness of the belt was the reason for this but that has been eliminated. Would be nice to look at a few other models and see how they are put together. Ha, there is only one autoreverse deck on the property and it doesn't belong to me. That'll learn me to throw **** out.

wrote:

So let me get this straight. The consensus now is that it has nothing
to do with the thickness of the belt but is to avoid resonance,
Logically resulting in less wow and flutter I would assume.



** The OP also posted his Q on sci.electronics.design and in my first reply there I pointed out the possible resonance issue as the reason for differing flywheel diameters.

A rubber belt and flywheel system has a resonant frequency - resulting from the springiness of the belt and the inertia of the wheel. I figured that where two flywheels are coupled by the same belt, it is better if their inertias are non identical so the resonant frequencies differ and so do not reinforce.



Really, on the surface is seemed that the thickness of the belt was
the reason for this but that has been eliminated.


** A really dopey idea based on a fallacy.


..... Phil

wrote:

Y'know, when I was in school they gave me this test. Turns out I was in the 99th percentile in mechanical reasoning.


Only two students in my school system got every question right on
that part of the aptitude tests. Myself, and a girl who like to work on
cars. I also got the top scores in math and science. I only got a 90 for
English. I took every math, science and shop class that they could fit
into my schedule, each year. Several years later I tested out of an
Electronics Engineering school while serving in the U.S. Army. I've
worked with very intelligent people who only finished high school, and
I've had the misfortune of working with those who can pass tests but who
are so @#$%^&* stupid that they set the shop on fire with a soldering
iron.

Michael Terrell wrote: " Only two students in my school system got every question right on
that part of the aptitude tests. Myself, and a girl who like to work on
cars. I also got the top scores in math and science. I only got a 90 for
English. I took every math, science and shop class that they could fit
into my schedule, each year. Several years later I tested out of an "


I envy people like you - seriously! It shows
how influences(chemical and otherwise) during
and after conception, and after birth and during
childhood - chemical and otherwise - can have
an effect on a child and later an adult.

"Only got a 90 for english"??? I was lucky to
get 90s in THAT - and 60s to 70s in all my other
subjects. Math? They had to make up a grade
just so I wouldn't have trouble later on getting
in to college. My single biggest regret in LIFE -
not being able to even read numbers, let alone
add, subtract, multiply, or do anything Greek
with them(!) And I trace it all back to some
activities my expectant folks were engaged in
back in the late '60s, and some choice names
my Dad coined me post-toddler-hood.

wrote:

Michael Terrell wrote: " Only two students in my school system got every question right on
that part of the aptitude tests. Myself, and a girl who like to work on
cars. I also got the top scores in math and science. I only got a 90 for
English. I took every math, science and shop class that they could fit
into my schedule, each year. Several years later I tested out of an "

I envy people like you - seriously! It shows
how influences(chemical and otherwise) during
and after conception, and after birth and during
childhood - chemical and otherwise - can have
an effect on a child and later an adult.

"Only got a 90 for english"??? I was lucky to
get 90s in THAT - and 60s to 70s in all my other
subjects. Math? They had to make up a grade
just so I wouldn't have trouble later on getting
in to college. My single biggest regret in LIFE -
not being able to even read numbers, let alone
add, subtract, multiply, or do anything Greek
with them(!) And I trace it all back to some
activities my expectant folks were engaged in
back in the late '60s, and some choice names
my Dad coined me post-toddler-hood.


I had health problems from an early age, so I spent a lot of time
reading and experimenting since I couldn't play in any sport. I was born
in the early '50s, when poorly trained doctors continued to prescribe
DES to pregnant women in the false belief that it prevented
miscarriages. It caused many health issues in the children, like my life
long problem with infections. The last one required a trip to the
hospital. I was also born with poor eyesight, and have worn glasses
since elementary school. I now have to sit about 12 inches from a 24"
monitor to see what I'm typing.

I taught Boolean Algebra to myself, to be able to write software to
track the C band birds. tHe program asked for your Latitude & Longitude,
then it printed out a two page report with the Azimuth and Elevation for
every bird you could see from your location. The program let you enter
your name, so the report stated, Prepared by:----- ---- to make people
think it came from an engineering service.

The Commodore 64 didn't have several functions I needed, so I had to
create them, as well. I always enjoyed a challenge, and often got what
others had given up on. That is why I have seen so many odd conditions
in equipment, in the last 55 years.

I was a Nerd, long before it was cool.