# Hot Bulb Engine



## cfellows (Jun 2, 2010)

I have decided to start experimenting with building a model IC engine using hot bulb ignition with fuel injection, like those built by Find Hansen. 

http://www.craftsmanshipmuseum.com/Hansen.htm

Has anyone else had any experience (and success) with these type of engines?

Chuck


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## BenPeake (Jun 2, 2010)

Hi Chuck,

I've had zero experience with these engines, but I just want to encourage you to have a shot at them. I watched the videos of Find's engines and they are really beautiful to watch running. I particularly love how he manages to recreate the appearance of a full sized machine on such a small scale. Even the burner looks proportional! I'll pop a video down the bottom of this post for anyone who is interested (I've watched it 3 times now!). I'm actually in Denmark (in Copenhagen) at the moment, so I might try and make contact with Find and squeeze some info out of him. It might be tricky though as he lives on some island I've never heard of. It sounds as though he's put a lot of time into experimenting with the configuration of the hot bulb ignition as it would seem it is difficult or impossible to create an actual scale version of it which functions.

Good luck and keep us posted and I'll do the same if I find anything out.

Ben

[ame]http://www.youtube.com/watch?v=cTs4l-Qd-UY[/ame]


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## Rustkolector (Jun 2, 2010)

Chuck,
I too would encourage you to try it. After seeling Find Hansens work, I have been thinking seriously about it myself. I own a 1.5 hp hot bulb engine built in about 1903. It took me three years to restore, and I think I can close my eyes and still picture every part on that engine. The fuel system would not be a problem as it is very low pressure and uses a hot splatter plate to vaporize the fuel. The governor would be a bit tricky as the change in the fuel pump stroke from no load to full load is extremely small. Find Hansen has done some amazing work on his engines. His actually run better, and with less smoke than most of the real hot bulb engines. Please let us know when you start.

Jeff


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## cfellows (Feb 28, 2011)

I've been noodling around with the Hot Bulb engine project although my efforts have been elsewhere. Today I had some time and decided to fabricate a hot bulb and try it out on my Plumbing Parts Engine. I made it out of a 1/2" diameter piece of mystery steel. It is about 1 3/8" long, the hot part on the outside is 9/32" and the other end is turned and threaded to a metric thread 10mm - 1mm to replace the CM-6 spark plug. There is a 3/16" hole drilled most of the way through the inside.

I took out the spark plug and replaced it with my hot bulb and heated it cherry red with my Mapp gas torch. Everything else was the same, including the vapor fuel tank, coleman fuel, etc. I gave it a couple of spins and it started. It ran good and kept running as long as I kept the torch on the hot bulb. When I removed the torch, it would fire another half dozen times then quit. Unfortunately, one side affect is that the cylinder head and cylinder get very hot from heat conducted from the hot bulb. But, I'm encouraged by the results. I think the hot bulb wall needs to be much thinner, maybe .010" or .015" thick to make it easier to heat and to slow heat conductance into the cylinder head. And, I may next give Find Hansen's hot bulb design a try. But so far, haven't had to mess with injector pumps or injectors. Of course that will be required if I'm to switch to heavier fuels like turpentine or kerosene.

Chuck


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## Rustkolector (Feb 28, 2011)

Chuck,
I think you will find that most hot bulb engines use some form of insulation between the hot bulb and the rest of the head assembly. One real engines, this was usually done with some woven insulation like that used on wood stove doors and prevents significant loss of heat to the head as you were experiencing. Not sure what type of small insulating ring to suggest to you, but it is needed. 

Jeff


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## Chaffe (Mar 1, 2011)

Interesting experemantation chuck, i wonder if a raise in compression and a switch to a more "detonation prone" fuel would help? I think you should definatly continue with this work.


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## Maryak (Mar 1, 2011)

From memory it was asbestos string wrapped around the thread. Much like plumbers in those days used red lead and hemp instead of teflon tape.


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## Chaffe (Mar 1, 2011)

Maryak  said:
			
		

> From memory it was asbestos string wrapped around the thread. Much like plumbers in those days used red lead and hemp instead of teflon tape.


alternativly you could turn a step on the hot tube and seat it in a piece of turned ceramic in the head, and use a screw to exert force onto is end to seal it.


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## shred (Mar 1, 2011)

I might try what Jerry Howell recommended for Stirling hot-ends; stainless steel bulbs with long, thin walls. That plus a fiber gasket could reduce heat transference quite a bit. On the other hand, you need the bulb to stay hot from combustion to keep igniting the fuel without the external torch, so maybe you need to keep a little thermal mass there.


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