# Rick's request is my command - Poppin video



## mklotz (Apr 17, 2008)

In another thread, Rick had asked to see a video of my version of Senft's Poppin engine.

Some remarks...

The engine has aerospace-quality precision ball bearings that were rejects from gyroscopes used in fighter aircraft inertial guidance systems. They're a bit delicate for this application but so far they've held up very well.

The cylinder is aluminum with a steel facing plate where the flame is applied. This is important because, since steel is a poor conductor, it doesn't "suck" all the heat out of the hot gas before it gets inside the cylinder. OTOH, once inside and the valve shut, the aluminum quickly sucks the heat up, creating the partial vacuum that actually powers the engine. (Well, technically, it's the atmosphere pushing against the low back pressure of the partial vacuum that powers the engine.)

If you build this engine, expect to spend a bit of time fussing with the valve. My valve is a piece of thin shim stock and it needs to be formed and placed "just so" to get the engine operating. Once fixed, though, it's a reliable runner.

Preheat the cylinder with the alcohol lamp prior to attempting a run. It doesn't like a cold cylinder.

I learn something new every time I run this engine. Today I learned that it's a good idea to dry ALL the alcohol off your thumb before lighting the alcohol flame.  Ouch, that smarts. Ah well, they don't call me a Klotz for nothing. (Please note that remark is not license for any of you to call me such.  )

[ame]http://www.youtube.com/watch?v=eCssHXWVYm0[/ame]


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## rake60 (Apr 17, 2008)

I love that engine!
Thanks for the video Marv!
Of all the flame lickers I've ever built that one is the easiest to start.

As for the alcohol on your thumb...
I was demonstrating mine on a lunch break at work.
After a quick refill of the burner it was ready to fire up.
There were about 8 coworkers present when I set the better part
of my right hand ablaze.
I causally blew out the flame and did my best to pretend it didn't
hurt like hell! 
	

	
	
		
		

		
			





Rick


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## BobWarfield (Apr 17, 2008)

That is a very pleasing little engine. Love the sound.

Cheers,

BW


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## cfellows (Apr 18, 2008)

Marv, tell me again what kind of fuel you use?

I have a poppin I built that I just can't get running. I tried it on denatured alcohol the other night, without success. Next day the piston was stuck. I finally got it free and discovered rust inside the cast iron cylinder. I'm guessing the denatured alcohol had too high a percentage of water?

Chuck


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## gilessim (Apr 18, 2008)

Grat stuff Marv as always!

Chuck, try to get hold of some of the alcohol used by french polishers, as that needs to be at least 99% for it to evaporate quickly enough, thats what I use with my flame licker (saying that mine's still not running properly either! but I think it's the flame position, Boggie says that pretty critical)

Giles


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## cfellows (Apr 18, 2008)

Is 99% Isopropyl the same thing?

Chuck


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## mklotz (Apr 18, 2008)

Chuck,

I use the ordinary alcohol sold in big box stores for diluting shellac and such - nothing special. I suspect it's methylated ethanol or straight methyl.

My Poppin has an aluminum cylinder and a stainless piston so rust has never been a problem. On mine the flame has to be quite close (e.g., flame edge 1/16 to 1/8" from inlet port) in order to run.

The biggest problem I had getting mine to run was with the valve seating properly. Although the vacuum created by the retreating piston helps to draw it against the valve plate, it needs to be adjusted so it's very flat against the valve plate and can seat properly. I had to go to thinner shim stock for the valve before it would seat properly. Once I did that it ran fine and has been doing so for twenty years.

Be sure to preheat the cylinder (use the alcohol lamp) before trying to run yours. If you start from a cold cylinder, it will eventually warm up from the ingested gas, but your patience may wane before that happens. A cold cylinder will "quench" the gas too quickly and the vacuum will dissipate before the valve can close.

Perhaps another thing to try is a weaker spring on the valve mechanism. If the spring is too strong, it may be producing too much drag on the cam mechanism.

Good luck on getting yours to run. When I got mine operating, I watched it, mesmerized, for hours. It's such an elemental and obvious engine - you can SEE the heat being converted into mechanical motion. Even my (then young) daughters loved it but kids love anything that involves fire.


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## rake60 (Apr 18, 2008)

Marv I keep watch your video and it's making me want to do a new build of that
engine. I made my cylinder and piston both of cast. It starts very easily without
preheating the cylinder, but I have to use a very light spring or it won't run at all.
Using the light spring makes it run much faster than yours.
It's more like this:
[ame]http://www.youtube.com/watch?v=TjEcWoxITSE[/ame]
I do like to see models running slower!

I believe that's called: _"Back to the drawing board..."_ :-\

Rick


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