Fire Eaters

[Stan]

This is for all the frustrated builders of fire eater engines. In the Duclos design, and I expect some others, The flame is a critical and hard to determine item. Any change from the original burner design may not run. If you have a good running Duclos fire eater and make small changes in flame position, you get major change in speed. Big changes in flame position and the engine stops.

When you have completed the build, spin the flywheel (it should spin easily) and if everything is right, you get an audible pop. If the timing is incorrect or the valve is not sealing, you don't get the pop. Small timing changes can be made on the valve rod where it connects to the slide valve.

If the engine pops reliably, concentrate on the burner and flame. Even the length of exposed wick makes a difference. When you have everything right, this is an engine that will start every time with one spin and needs no warmup.

As a BTDT, I threw away my doorknob burner because all the alcohol evaporated out of it when sitting on the shelf. I made a new leak proof burner with O ring seals and spent the next several weeks trying to get the engine to run again. The length of the wick tube turned out to be the critical dimension.

 

[Mcgyver]

Stan, good info, i have one ready to go that works well on sterno but needs a proper fuel tank....being looking for an appropriate doorknob for ages and am not spending what a nice new brass one costs....so with your post i am abandoning the door knob idea

any construction notes you can share...is it made from solid or did you roll it? the O ring we see, that's just to preserve fuel? is the length of the spout adjustable? can you share some dimensions?

sorry for the 100 questions

 

[Stan]

Sometimes my scrap gets recycled several times. I thought I had a bargain when I bought a length of 2" 660 bronze at the scrap metal yard. I made a hot end for a stirling out of it with less than stellar success. The reason it was at the scrapyard was that it had a hard spot in. The outside machined not too bad but boring the ID was impossible.

New hot end made out of brass and chunk of bronze went back in the scrap box.

I dug it out to make the alky burner. The bottom is recessed and soft soldered in. The filler is a separate piece also soft soldered and the filler plug has an O ring.
The wick fitting was mostly made with a file to fit the tank. The wick tube was originally almost twice as long but got cut down in stages to get a satisfactory speed.
A few quick dimensions. Tank OD is 1.6". Height of tank is 2.1". Filler plug is 3/4" UNF
Outlet fitting is threaded 7/16" UNF and the wick tube is 1/4" ID

I have found that on this engine and the same design in 1/2 scale that the flame has to be below and behind the valve.