Senft "Poppin" engine

[Brian Rupnow]

Some of the flame eaters I seen on you-tube (Big Nick for example) have exhaust stacks on the cylinder. What's that about? Has anyone knowledge of why. Obviously it must help from blowing out the flame, but I would like some more information. Thank you in advance, Brian

 

[el gringo]

Some of the flame eaters I seen on you-tube (Big Nick for example) have exhaust stacks on the cylinder. What's that about? Has anyone knowledge of why. Obviously it must help from blowing out the flame, but I would like some more information. Thank you in advance, Brian

Cosmetic?

 

[Brian Rupnow]

No, not just cosmetic. They do help the engine run. I'm not certain yet how they work, but I'm getting replies on other forums saying the help the engine to run more stably.

 

[rlukens]

Some of the flame eaters I seen on you-tube (Big Nick for example) have exhaust stacks on the cylinder. What's that about? Has anyone knowledge of why. Obviously it must help from blowing out the flame, but I would like some more information. Thank you in advance, Brian

I'm interested in that too. I assume that the "vacuum" in the cylinder changes to pressure somewhere mid stroke. The exhaust port is basically a check valve that relieves that pressure when the intake valve is partially close. Makes sense to me.

 

[fcheslop]

It is a relief valve for the exhaust gasses instead of blowing the valve of the port
You can see it clearly on this Bengs video just a nitrile ball that shuts off on a seat like a clack valve.
You adjust the amount of lift on the ball to regulate speed.This system is used on a lot of flame gulpers including the lanz Bulldog
https://youtu.be/0G4OuBVb7NY

 

[Brian Rupnow]

Ohhh--I do like that!!!

 

[fcheslop]

I plan on building one with a 50mm bore once Iv finished other projects
well thats the plan
There is a lot of flamefesser designs knocking about mainly European
Here is a link to the build of the kit
http://www.bengs-modellbau.de/magazin/2988-baubericht-flammenfresser-jarne/
cheers

 

[el gringo]

"So, Ray--are you building one of these, and if so, what stage are you at?---Brian"
Did you receive the answer to your query?

__________________

 

[Brian Rupnow]

Yes Ray, I did. It looks as if you are pretty well finished. If anyone liked my sexy cylinder, here is the drawing of it.--Brian

 

[Brian Rupnow]

I got an answer on the poppet valve exhaust. There should never be positive pressure build up inside a flame eater engine. The Poppin gets away without an exhaust stack because if the piston moving towards top dead center causes any positive pressure, the .002" thick valve flexes enough to release this pressure. On larger flame eaters where the sliding valve is mechanically driven and does not flex, you need the exhaust valve which is indeed a poppet valve to release this pressure. This type of valve is basically a small ball setting in a cone. It will let pressure out, but seals automatically when the piston is creating suction to pull the flame into the engine. Some engines have a stack, although it is just for show. Other engines just have the exposed valve setting on top of the cylinder at the end opposite to the crankshaft.

 

[rlukens]

I plan on building one with a 50mm bore once Iv finished other projects
well thats the plan
There is a lot of flamefesser designs knocking about mainly European
Here is a link to the build of the kit
http://www.bengs-modellbau.de/magazin/2988-baubericht-flammenfresser-jarne/
cheers

That is a fantastic little engine. I know now whose design I'm going to follow.
I notice there was little attention given to reducing moving mass and I don't think I saw any bearings. Yet it took off with a twist.
Thanks for posting

Russ

 

[Brian Rupnow]

What a lovely little engine this is. The more it runs, the better it runs. I fire it up a couple of times a day when I'm setting at my computer and it makes me smile. No need for a battery or an air compressor. This engine is pure fun!!!