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.