For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

DougC wrote:
For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns
on a 3/4" axle and is supported on three spiders at the center and
ends, so that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I
can construct a "fan box" to use a separate fan to circulate the air
if need be. I really just need the heater circuit and elements... The
fan motor may not be able to withstand 150F so it will be separated
from the hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room
heaters' but they are way overbuilt and too expensive for my meager
budget. There must be something cheap and available that I can abuse
reasonably-safely to do this. I'd prefer lowering the operating
temperature of a device built for higher temps, than raising the
temperature of something meant for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm"
setting for the food seems to usually start at 150F. I have a
multimeter with some thermal probes so I can test temps fairly
decently and I know a bit about electronics but don't know if there's
any easy way to recalibrate the heat to a lower temp.
Can you use this type of heating element
http://uk.rs-online.com/web/search/s...ct&R=200122 9
.. They are readily available and inexpensive and come in a variety of
lengths and wattages. The one I posted is 4.5' long but is just an
example. You would probably want a temperature controller or energy
controller to set the temperature. The element itself is also insulated
and enclosed in a metal sheath which can be grounded for safety.

"David Billington" wrote in message
...
DougC wrote:
For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal, about
five inches in diameter and .049" thick aluminum wall. It turns on a 3/4"
axle and is supported on three spiders at the center and ends, so that
air can flow through.

The whole machine is always indoors, in ~70F room-temperature conditions.
For other reasons it can't be used in drastically colder temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.
Can you use this type of heating element
http://uk.rs-online.com/web/search/s...ct&R=200122 9 .
They are readily available and inexpensive and come in a variety of
lengths and wattages. The one I posted is 4.5' long but is just an
example. You would probably want a temperature controller or energy
controller to set the temperature. The element itself is also insulated
and enclosed in a metal sheath which can be grounded for safety.


Leading on from Davids suggestion - those elements look like the ones in
laundry clothes dryers. Maybe for a quick test get hold of a cheap clothes
dryer and duct the exhaust into your roller. They usually have a warm & hot
setting (guess 1kw & 2kw elements) and can often be got for free on verge
throw out days.

On Fri, 01 Jul 2011 07:39:48 -0500, DougC
wrote:

For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

A duct heater would be ideal, though it's probably a budget killer
unless you can find a used one.
http://www.tutco.com/convection_heat..._heat_pack.php

One cheapskate approach is a couple electric range elements stacked in
a length of stovepipe.

--
Ned Simmons

DougC wrote:
For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

How will the material you are using this roller on respond to
temperature variations? With that length and being aluminum the
temperature at one end will be considerably higher than the other if you
heat it from one end.
I would suggest two solutions. One which is the most common would be to
seal the roller on each end with the hollow area filled with something
like anti-freeze and replace the carrier axle with a hollow tube (1 1/2"
or so) and then pump heated coolant through the tubing to heat the
surface evenly, you would also have a lot better control.

The second way would be to build a strip heater and position it below
the roller (out of the way of whatever passes on the roller) Cap the
ends of the roller so airflow doesn't cool it unevenly. A single 8'
element out of a commercial drying/baking oven would do the job. The
heater would heat the surface of the roller which would start to cool as
soon as it left the heater but that is easy to compensate for. You could
use a simple IR thermometer measuring the surface for temperature control.

--
Steve W.

A couple of important parameters:
-how closely does the temperature have to be regulated? The 120 - 150
is the range, I assume, that you want to be able to set it in, not the
allowable swing. Or not?

- is this for commercial/industrial use? I.e., needed for extended,
trouble-free, use. Or for occasional home use?

The electric stove-top element Ned mentioned is around the right
wattage, IIRC. Also compact.

For cheap, not-too-accurate, regulation I would probably go with an
op-amp based circuit. Thermistor as a sensor, drive a MOSFET that
controls a relay that switches the AC power to the heater. Google "op
amp thermistor thermostat".

My intuition is that 150F is not that hot for a fan. But convection
ovens use fans that circulate 500F air.

HTH,
Bob

On 07/01/2011 08:49 AM, Paul Hovnanian P.E. wrote:
DougC wrote:

For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Aim a hair-dryer down one end of the tube.

It took _six replies_ before someone figured out a mapping between "UL
Listed thingie that delivers 1000W at 150F and has a fan" and "hair
dryer". Good for you, Paul!

If one hair dryer doesn't do it, try two. Or three. Or whatever. Get
them from Goodwill if you're on that much of a budget.

It may be as simple as this (although a hair dryer fan might have problems
providing adequate flow with the back pressure.

You say you can use 120 to 150 F, but given this range, does the temperature
have to be uniform (within what limits) along the length of the roller?

That's an important consideration -- it'll be easy to end up with a warm
end and a cold end. You may need to do something a bit perverted, like
an inner somewhat insulating tube (PVC pipe that can stand hot water
would maybe do) with holes drilled at whatever intervals makes things
work. Put hot air into the inner tube, and drill your holes to keep the
temperature distribution of the outer tube constant.


Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

Its easy to construct a fan that will tolerate much higher temps. Just make
the impeller and housing out of whatever will tolerate the temps and
connect the motor using a suitably long shaft to keep it in a cooler
region. You can have the shaft pass through a heat shield (sheet metal with
a hole for the shaft) to protect the motor against radiated heat and draw
the incoming (cool) air over the shaft and through the motor to keep it
cool.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 07/01/2011 05:39 AM, DougC wrote:
For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

UL listed. 1000W. 150F. Blow Dryer. It includes a fan as a bonus.

Why do you want UL listed? If you're selling product, blocking the
output of a blow dryer with something like a long, restrictive tube is
going to shoot your UL listing all to hell.

Do you need temperature regulation, or can you just fiddle a "heat"
knob? Getting the temperature regulated well isn't going to be easy --
you have to sense it, you have to control it, and what do you do if one
end of the tube is cool and the other hot?

Thermistors and op-amps have been suggested, and that's not a bad way to
go. Depending on what you're comfortable with, a Parallax board and
some code would work well, too. There's also snap-action thermostats
available -- you could use one to control a relay to the heater coil.

Any temperature regulation scheme is going to require you to rip into
your hypothetical UL listed hair dryers to separate heating elements
from fans. This will shoot your UL listing all to hell in a different way.

News Flash: Food dryer. Fan, heating element, designed for restricted
airflow, available at garage sales, and, as a special bonus, it includes
a thermostat. After you rip it up and rearrange all the pieces you will
have shot your -- well, anyway, it's an idea.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Fri, 01 Jul 2011 07:39:48 -0500, DougC
wrote:

For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

Why not run a heating element down the center of a hollow roller? Or
put a series of elements in an enclosure snuggly above the roller that
directs heat At the aluminum roller and heats it up? It shouldnt be
hard to do.


--
Maxim 12: A soft answer turneth away wrath.
Once wrath is looking the other way, shoot it in the head.

On Fri, 01 Jul 2011 13:54:51 +0100, David Billington
wrote:

DougC wrote:
For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns
on a 3/4" axle and is supported on three spiders at the center and
ends, so that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I
can construct a "fan box" to use a separate fan to circulate the air
if need be. I really just need the heater circuit and elements... The
fan motor may not be able to withstand 150F so it will be separated
from the hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room
heaters' but they are way overbuilt and too expensive for my meager
budget. There must be something cheap and available that I can abuse
reasonably-safely to do this. I'd prefer lowering the operating
temperature of a device built for higher temps, than raising the
temperature of something meant for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm"
setting for the food seems to usually start at 150F. I have a
multimeter with some thermal probes so I can test temps fairly
decently and I know a bit about electronics but don't know if there's
any easy way to recalibrate the heat to a lower temp.
Can you use this type of heating element
http://uk.rs-online.com/web/search/s...ct&R=200122 9
. They are readily available and inexpensive and come in a variety of
lengths and wattages. The one I posted is 4.5' long but is just an
example. You would probably want a temperature controller or energy
controller to set the temperature. The element itself is also insulated
and enclosed in a metal sheath which can be grounded for safety.


Hell..Ive got a couple bushel baskets full of similar heating
elements..though most a only a couple feet long.


--
Maxim 12: A soft answer turneth away wrath.
Once wrath is looking the other way, shoot it in the head.

On 07/01/2011 11:15 AM, Gunner Asch wrote:
On Fri, 01 Jul 2011 07:39:48 -0500,
wrote:

For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

Why not run a heating element down the center of a hollow roller? Or
put a series of elements in an enclosure snuggly above the roller that
directs heat At the aluminum roller and heats it up? It shouldnt be
hard to do.

The first solution would require slip rings -- but those are as close as
your nearest car alternator. The second is a bit indirect -- but it
sounds like it'd work great, particularly if you could keep the roller
painted black.

The OP hasn't chimed in yet on why he was asking for the UL listing
thing -- neither of those solution meets that criteria, but I'm not sure
you can get there from here anyway.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 7/1/2011 5:39 AM, DougC wrote:
For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

just run a calrad or two down the center, in series and control with an
SCR based temp controller

--
www.wbnoble.com

On 7/1/2011 2:30 PM, Tim Wescott wrote:
On 07/01/2011 11:15 AM, Gunner Asch wrote:
On Fri, 01 Jul 2011 07:39:48 -0500,
wrote:

For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Are there any cheap UL-listed devices around built for doing this? I can
construct a "fan box" to use a separate fan to circulate the air if need
be. I really just need the heater circuit and elements... The fan motor
may not be able to withstand 150F so it will be separated from the
hot-air loop, but that's not a problem.

I know that there are industrial-devices known as 'drying-room heaters'
but they are way overbuilt and too expensive for my meager budget. There
must be something cheap and available that I can abuse reasonably-safely
to do this. I'd prefer lowering the operating temperature of a device
built for higher temps, than raising the temperature of something meant
for lower temps....

I have looked at a bunch of toaster-ovens and the lowest "warm" setting
for the food seems to usually start at 150F. I have a multimeter with
some thermal probes so I can test temps fairly decently and I know a bit
about electronics but don't know if there's any easy way to recalibrate
the heat to a lower temp.

Why not run a heating element down the center of a hollow roller? Or
put a series of elements in an enclosure snuggly above the roller that
directs heat At the aluminum roller and heats it up? It shouldnt be
hard to do.

The first solution would require slip rings -- but those are as close as
your nearest car alternator. The second is a bit indirect -- but it
sounds like it'd work great, particularly if you could keep the roller
painted black.

The OP hasn't chimed in yet on why he was asking for the UL listing
thing -- neither of those solution meets that criteria, but I'm not sure
you can get there from here anyway.


The device is just for my own occasional home use, not for sale. It
won't be left unattended, but I want to be able to set a knob for a MAX
heat of 150F. I want it to reach that in 10-15 minutes, but I also want
to know that it won't go over that even if I do leave it for a hour or
three.

The tube needs to be heated pretty evenly from one end to the other. A
low heat and a high airflow rate would do that I'd think. Filling the
tube with any sort of moderating liquid is not practical.

The heating element down the center of the roller sounds interesting,
but I don't want to have to build a circuit to control the thing. I'd
prefer to modify something UL listed to run at a lower temperature, just
because the control circuit is that much less likely to burst into flames.

I'll probably look at a toaster oven first, if there's multiple elements
it may be possible to disconnect some of them usefully or maybe mess
with the temperature sensor.

"Paul Hovnanian P.E." wrote:

Tim Wescott wrote:

On 07/01/2011 08:49 AM, Paul Hovnanian P.E. wrote:
DougC wrote:

For a project I am working on, I need to heat a roller.

The roller in question is a tube about eight feet long, horizontal,
about five inches in diameter and .049" thick aluminum wall. It turns on
a 3/4" axle and is supported on three spiders at the center and ends, so
that air can flow through.

The whole machine is always indoors, in ~70F room-temperature
conditions. For other reasons it can't be used in drastically colder
temperatures.

I need to be able to heat this whole thing to maybe 120F to 150F,
automatically. That is, I want to set a temperature and forget it. The
wattage I am guessing might take 1000 watts, and it must be electric
(dry) heat--propane will not help, as it gives off water vapor.

Aim a hair-dryer down one end of the tube.

It took _six replies_ before someone figured out a mapping between "UL
Listed thingie that delivers 1000W at 150F and has a fan" and "hair
dryer". Good for you, Paul!

It was quite an intuitive leap considering that I have no other use for a
hair dryer.


Or hair? ;-)


--
It's easy to think outside the box, when you have a cutting torch.

On 7/1/2011 11:39 AM, Tim Wescott wrote:
On 07/01/2011 08:49 AM, Paul Hovnanian P.E. wrote:
....
Aim a hair-dryer down one end of the tube.

It took _six replies_ before someone figured out a mapping between "UL
Listed thingie that delivers 1000W at 150F and has a fan" and "hair
dryer". Good for you, Paul!

If one hair dryer doesn't do it, try two. Or three. Or whatever. Get
them from Goodwill if you're on that much of a budget.


I'm aware of hair dryers, and heat guns.
The temperature control with using either is still an issue tho'.

I am hoping to successfully abuse something that already has its own
thermostat.

DougC wrote:
On 7/1/2011 11:39 AM, Tim Wescott wrote:
On 07/01/2011 08:49 AM, Paul Hovnanian P.E. wrote:
....
Aim a hair-dryer down one end of the tube.

It took _six replies_ before someone figured out a mapping between "UL
Listed thingie that delivers 1000W at 150F and has a fan" and "hair
dryer". Good for you, Paul!

If one hair dryer doesn't do it, try two. Or three. Or whatever. Get
them from Goodwill if you're on that much of a budget.


I'm aware of hair dryers, and heat guns.
The temperature control with using either is still an issue tho'.

I am hoping to successfully abuse something that already has its own
thermostat.

What RPM are we talking about, Doug?
If you say '6000' then you could spin your roller near some
NdFeb magnets and use the induced current in Joule heating
the aluminum. Sort of.

--Winston

On 7/1/2011 7:39 AM, DougC wrote:
For a project I am working on, I need to heat a roller.
......

A few people suggested putting a heating element directly inside the
tube, and the more I think about that, the easier overall it sounds. I
may not need to have the heater running while the roller is turning, if
it is pre-heated--so I can ignore that issue for now.

I see there's lots of easily-obtained pipe heating tape around (even in
local hardware stores) but it comes with a built-in thermostat that
doesn't turn on at all above freezing. But at least I could jump over
the thermostat, or obtain the heat tape itself from that.

The next problem is finding a cheap adjustable controller of some type.
McMaster-Carr sells a bunch for $150-$200+... I'll keep them in mind if
this is a great financial success, but that's a bit much for me to pay now.

Would the $20 Harbor Freight router speed controller work? The specs say
it is rated for 1800 watts, though I would get somewhat concerned
driving it over maybe 1200w:
http://www.harborfreight.com/router-...rol-43060.html

I already know that it doesn't work on AC-powered tool motors that
already have their own speed controllers built-in, so that smells like
an SCR to me.

/Plain/ heat tape (with no integral thermostat) can take any kind of
power (any kind of AC or DC) so how would the speed controller know the
electrical load of the heat tape wasn't a motor? Would the speed
controller depending on any sort of electrical feedback from the motor
to regulate the output?
,,,,
My experience from using the one I have with a couple power tools is
that it does not, though I haven't looked at it with a multimeter or an
oscilloscope. The tool motor does not hold a constant speed under load,
but slows down, as if the voltage supply is constant.

On 7/6/2011 5:26 AM, DougC wrote:

Would the $20 Harbor Freight router speed controller work? ....


Nevermind, a lot of people doing various things are using it for exactly
this purpose.

Looks like it's good to go up to 1500 w or so, and as long as it's not
left totally unattended (construction of the product is not REAL
impressive).

On Jul 4, 3:24*pm, DougC wrote:
...
I am hoping to successfully abuse something that already has its own
thermostat.

Maybe a drum heater?
http://www.northerntool.com/shop/too...m-tote-heaters
I don't know if they are flexible enough to roll up. Silicone oil pan
heaters should be.

Electric water heater thermostats are cheap, simple, have the right
temperature range and will handle ~5KW.

When I built production-line test stations we used cylindrical heating
elements and capillary thermostat sensors that fit into drilled
holes.

jsw

On 7/6/2011 10:21 PM, Michael A. Terrell wrote:

wrote:

On Wed, 06 Jul 2011 11:13:14 -0400, "Michael A. Terrell"
wrote:


DougC wrote:

On 7/1/2011 7:39 AM, DougC wrote:
For a project I am working on, I need to heat a roller.
......
You guys need to look at the fusing roller of a laser printer for
inspiration. I have not seen the original post, so don't know what
size roller you are looking at - but a halogen lemp in the center of a
metal roller is a fairly simple and efficient way to attack the
problem.


He still needs to control the temperature.



It will be a 2-3 weeks before I have the money to play with this, so I
have time to look around.

Right now it looks like I may try using the (1800w) Harbor Freight speed
controller to run ..... something. A automatic temperature control (or
at least an alarm) would be nice, but not necessary. Mainly I just want
a way to throttle the power. I'll get an IR thermometer to check the
temperature.

Eight or ten 200W halogen bulbs in series might work well enough, if the
filaments don't have breakage problems.

The heat cable I don't think now is going to work well, on a cost/watt
basis... It doesn't put out much heat, only 5-10W per foot, unless you
buy the expensive industrial stuff--and that can still do 15-20. Either
way, it would take a whole bunch of it to reach even 500 watts.

I have not been able to locate any straight + long metal heating
elements online that are inexpensive; all the lower priced ones are for
stoves or dishwashers and are coiled up or curved. I'd need at least
two, around 3 feet long each. I don't know what would happen to the
curved ones if they were bent out straight.
,,,,
I could just try making my own heating elements out of some 1/8" music
wire, I suppose. They'd need to be electrically isolated inside the
tube, but that's not a major task.

There's flexible-wire clothes dryer heating elements very cheap and they
put out more than enough heat for this use, but I think (?) they are all
for 220V. I don't know what they'd do on 110V (half as much heat?) Part
info doesn't give the wattage output, but I'd guess it'd be at least 1K...

DougC wrote:
....
I have not been able to locate any straight + long metal heating
elements online that are inexpensive; all the lower priced ones are for
stoves or dishwashers and are coiled up or curved. I'd need at least
two, around 3 feet long each. I don't know what would happen to the
curved ones if they were bent out straight.
....

I have taken 12"+- rods from a toaster oven and easily bent them into
1-1/2" diameter loops. These looked exactly like full-size-oven
elements, so I would expect that the large elements are also bend-able.
Or straighten-able in your case.

Bob

Go to www.mcmaster.com and put 511 (to go to that page) or part number
4550T141 in the search box. This is an 8' long heating tape, 78 watts/foot,
624 watts total, for $69. Two in parallel would give you 1248 watts, about
your target power. Oh, if you run a 220V heater on 110V you get 1/4th the
power, not 1/2. Browse around for heaters; they have a great selection.
Page 508 has bendable rod heating elements like in a stove, they sell them
straight and you bend to shape.

-----
Regards,
Carl Ijames
"DougC" wrote in message ...

On 7/6/2011 10:21 PM, Michael A. Terrell wrote:

wrote:

On Wed, 06 Jul 2011 11:13:14 -0400, "Michael A. Terrell"
wrote:


DougC wrote:

On 7/1/2011 7:39 AM, DougC wrote:
For a project I am working on, I need to heat a roller.
......
You guys need to look at the fusing roller of a laser printer for
inspiration. I have not seen the original post, so don't know what
size roller you are looking at - but a halogen lemp in the center of a
metal roller is a fairly simple and efficient way to attack the
problem.


He still needs to control the temperature.



It will be a 2-3 weeks before I have the money to play with this, so I
have time to look around.

Right now it looks like I may try using the (1800w) Harbor Freight speed
controller to run ..... something. A automatic temperature control (or
at least an alarm) would be nice, but not necessary. Mainly I just want
a way to throttle the power. I'll get an IR thermometer to check the
temperature.

Eight or ten 200W halogen bulbs in series might work well enough, if the
filaments don't have breakage problems.

The heat cable I don't think now is going to work well, on a cost/watt
basis... It doesn't put out much heat, only 5-10W per foot, unless you
buy the expensive industrial stuff--and that can still do 15-20. Either
way, it would take a whole bunch of it to reach even 500 watts.

I have not been able to locate any straight + long metal heating
elements online that are inexpensive; all the lower priced ones are for
stoves or dishwashers and are coiled up or curved. I'd need at least
two, around 3 feet long each. I don't know what would happen to the
curved ones if they were bent out straight.
,,,,
I could just try making my own heating elements out of some 1/8" music
wire, I suppose. They'd need to be electrically isolated inside the
tube, but that's not a major task.

There's flexible-wire clothes dryer heating elements very cheap and they
put out more than enough heat for this use, but I think (?) they are all
for 220V. I don't know what they'd do on 110V (half as much heat?) Part
info doesn't give the wattage output, but I'd guess it'd be at least 1K...

Carl Ijames wrote:

Go to www.mcmaster.com and put 511 (to go to that page) or part number
4550T141 in the search box. This is an 8' long heating tape, 78 watts/foot,
624 watts total, for $69. Two in parallel would give you 1248 watts, about
your target power. Oh, if you run a 220V heater on 110V you get 1/4th the
power, not 1/2. Browse around for heaters; they have a great selection.
Page 508 has bendable rod heating elements like in a stove, they sell them
straight and you bend to shape.


If you run the 240 heater with a diode in series you'll get half
power, so two strips with two diodes and a couple center off switches
you could have four different temperatures. Shorting out one diode with
the temperature controller will minimize the current it has to handle,
and reduce temperature cycling in the heaters.


--
It's easy to think outside the box, when you have a cutting torch.

On 2011-07-07, DougC wrote:

[ ... ]

I have not been able to locate any straight + long metal heating
elements online that are inexpensive; all the lower priced ones are for
stoves or dishwashers and are coiled up or curved. I'd need at least
two, around 3 feet long each. I don't know what would happen to the
curved ones if they were bent out straight.
,,,,
I could just try making my own heating elements out of some 1/8" music
wire, I suppose. They'd need to be electrically isolated inside the
tube, but that's not a major task.

Hmm ... music wire is steel. It will rust rather quickly when
heated like that.

You want Nichrome, or some other heating element wire.

Or -- what is the overall length? There are quartz enclosed
heating elements at least four feet long, and probably longer. These
are usually mounted in reflectors hung from the ceiling and used for
radiant heat.

Make bearings and hollow spindles for the ends, along with a
gear to drive one end.

Assuming that you don't need the workpiece in contact with the
cylinder for over 270 degrees, you can put either an adapted IR
thermometer, or a pick-up roller to transfer heat from the cylinder into
the roller, and measure that temperature with a thermistor or a
thermocouple connected to a nice proportional controller like the ones
Omega makes. It will even automatically adjust to avoid overshoot in
the temperature. When it is first turned on, it will apply full power
until it gets somewhere near 2/3 of the set temperature, then turn the
heating element off for a little while and observe how far the
temperature shoots past that point. Using that information, as it
approaches the set point, it will start cycling the heater on and off
and keep doing so to maintain the temperature very near the set point.
As an example, I picked up a small heat treating oven without a
controller at a flea market a few years ago. I fitted it with an Omega
controller which I already had, and a Type-K thermocouple. If I set the
temperature for 1800 F it will adjust on the way up, and overshoot by
all of 1 degree F -- no more.

If the aluminum cylinder can be anodized black, you could even
radiantly heat it from the outside, in the remaining 90 degrees where
the workpiece does not conact the cylinder.

There's flexible-wire clothes dryer heating elements very cheap and they
put out more than enough heat for this use, but I think (?) they are all
for 220V. I don't know what they'd do on 110V (half as much heat?)

Roughly 1/4 the heat. That might still be all that you need.

Part
info doesn't give the wattage output, but I'd guess it'd be at least 1K...

Look at the current draw of the dryer -- most of that will be
the heating element. (Maybe 20% will be the motor.)

And if you want to run it on 120 VAC -- cut the element in half.

Lots of support points in any case, because as they heat, they
sag.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 7/7/2011 5:58 PM, Carl Ijames wrote:
...
Page 508 has bendable rod heating elements like in a stove, they sell them
straight and you bend to shape.

-----
Regards,
Carl Ijames

Aha! I see now.

He heh, it only shows them bent, so I thought they were /all/ bent. :|

I know that heating elements are normally nichrome, but the nichrome
ones can be heated until they're orange-hot. What I was doing wouldn't
likely ever be used at such temps, so that was why I thought that music
wire might work.

Two 3-footers should do it though, and $75 isn't too bad.

"DougC" wrote in message
...
On 7/7/2011 5:58 PM, Carl Ijames wrote:
...
Page 508 has bendable rod heating elements like in a stove, they sell
them
straight and you bend to shape.

-----
Regards,
Carl Ijames

Aha! I see now.

He heh, it only shows them bent, so I thought they were /all/ bent. :|

I know that heating elements are normally nichrome, but the nichrome ones
can be heated until they're orange-hot. What I was doing wouldn't likely
ever be used at such temps, so that was why I thought that music wire
might work.

Music wire, which is plain, high-carbon steel, rusts if you look at it
cross-eyed. Heat it, and it's worse.

I made a small 12V heater element out of 20 guage stainless wire. It takes a
surprising amount of wire to get much resistance, but stainless has a much
higher resistance per foot than other steel wire -- about four times as
great. It's also about half as resistant as nichrome. It will take some
heat, but not as much as nichrome.

Here are some other values to give you perspective:

http://physics.info/electric-resistance/ (about halfway down the page)

--
Ed Huntress


Two 3-footers should do it though, and $75 isn't too bad.