Gallery, Projects and General > How do I??
Electric heater for hot air engine?
vtsteam:
I wonder if there's some kind of light bulb that might work. I remember some small halogen bulbs seemed to put out a whole lot of heat. Focused on the displacer cylinder from an inch away or so maybe?
vtsteam:
Don't know much about these:
https://www.amazon.com/Simple-Deluxe-Ceramic-Emitter-Reptile/dp/B0CWGCCQWV
It does say not to turn it on and off frequently.
How frequently? :scratch:
awemawson:
Nichrome wire as bought will be fairly easy to bend but once used will become very brittle. As a child my source of nichrome wire for experimentation was the heater bars from electric fires and unreeling an old ones was a challenge. I was once given a brand new one still in its cardboard tube and it was a joy to work with.
vtsteam:
Thanks Andrew. :beer:
I guess I need to have a ballpark idea of gauge needed.
I'd like to keep the voltage low on something I that I build for safety sake. 12 volts would be ideal, but that would require over ten amps (I believe -- not actually sure, but as a guess 120 watts might be minimum needed?). My variable DC power supply is a 10 amp supply, it does however go to 30V, so I guess I have the supply for it.
I'm not sure how nichrome wire compares with equivalent gauge stainless for resistance per unit length (when hot).
I did feel in my tests that I'd have liked even thicker ss wire, for fewer turns -- after all I only need to heat about an inch of length on the displacer cylinder. Lots of turns means closer spacing, which is harder to make.
I was thinking that I do have other stainless wire besides just the fishing leader. I have aircraft grade twist lock wire, and some other miscellaneous types. They probably all coil better as well. Might give samples of those a go. The power supply has both constant current and voltage modes, and the watt meter and IR temp probe makes it possible to test a short length and then extrapolate to longer.
Also, just for giggles I did send for those Herp warmer bulbs linked above. They are 2 for $9 for the 3" dia 150 watt versions, and I have a ceramic base incandescent light fixture.
vtsteam:
Tested a 24" (610 mm) coiled length of .032" (.8mm) aircraft safety wire T302/304 stainless steel, and it glowed dull orange in air in daylight at 10 amps and 16 volts. That's just above the 150 watt target figure. It's also easy to coil.
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