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

Thanks for the nice comments, guys!

I'm happy with how this turned out, but there's no question that it could use a bit more heat. I was thinking about making a new aluminum heater plug to accommodate a third cartridge heater, but then it occurred to me that I could simply modify the existing plug to accommodate four heaters. My feeling is that the heaters need to be evenly spaced to provide uniform heat transfer to the boiler.

I drilled and reamed four new holes in the original plug as laid out below:

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The two original holes at the 3:00 and 9:00 o'clock positions would not be used. The wiring of the additional heaters proved to be the most challenging part of the job, given the limited space available. Here's how the finished installation looks before installing the bottom cover:

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With the four heaters wired in, the resistance now reads 23 ohms. At 120 volts, the heaters draw a total of 5.22 amps, and supply 626 watts of power. This is probably substantially more than the original heater put out, but I suspect that it's inaccurate to compare the heat supplied, per watt, for different types of heaters. While the cartridge heater is rated at 150 watts, I don't think that the full amount is transferred to the boiler. Not like a red hot nichrome element up-close-and-personal, only separated from the boiler sheath by a thin layer of mica.

At any rate, I proceeded to conduct a running test. I wanted to see what it was capable of, so I didn't hold back on the volts (it was connected to a variac.) I'm afraid it overwhelmed the poor windmill, eventually spewing water across the bench:



Looks like I need to make one of those little Baker fans.    Around 90 volts would probably make for a more dignified steaming. I also need to try some heavier springs on the throttle and whistle valves. They seem to be leaking like sieves.

Anyway, thanks again for the kind words!