Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Did some figuring on this...

I have an old heater from a B30. The heating wire itself is good, but the aluminum terminals have rotted off. The electrical info, from the nameplate reads:

110 volts, 375 watts.

If I = P/V, then the current = 375/110 = 3.41A

If R = V/I, then the resistance = 32.3 ohms (The ACTUAL resistance measures 28.5 ohms, for whatever that's worth)

The number of turns is approx. 34, at 2.5"/turn, which gives a heater ribbon length of 85"

85" = 7.08 ft., 32.3 ohms would require a wire resistance of approx. 4.6 ohms/ft.

I measure the wire ribbon size at .004 thick X .031" wide.

This source has wire available in 5.15 ohms/ft, .0035" thick, and 1/32" wide, which would work:

https://jacobs-online.biz/nichrome_ribbon_wire.htm

It's the first size listed, with various lengths available.

Paula

You’re on the right track! I got my nichrome ribbon from wireoptim.com. I use two sizes, 0.8mmx0.1mm and 0.5mmx0.1mm, 4.15 ohms/ft and 6.57 ohms/ft respectively.
I also use mica insulation sheet that is as close to the thickness of the original mica as I could find. It’s much easier to work with compared to regular mica. I cut it on a regular paper cutter and it seems to hold up well to the heat so far. I bought what I have on eBay.
I try to re-use the aluminum lugs when I can, but I have also made new ones from aluminum and copper.
These heaters are fairly simple to make, but you have to get the resistance right and also make sure you can get the right number of windings on the substrate.
Here’s a calculator I like to use.
 https://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.html
I’ve attached a few pics of the dispenser I made for the ribbon. It works well, but has to be clamped down to the work surface.