How I build my Model Engines

[rdean]

If I changed the O ring the engine would run good for a while. The next day I would have problems starting it. I gave up.

I use Viton o-rings almost exclusively on my engines that have a larger width of 0.103. I then cut the piston groove at 0.113 wide to give it someplace to squish into. If the o-ring is trapped in the groove it will wear quickly and fail when the engine cools off. The surface finish of the liner is important but from what you have said that is not your problem.

Yet another thread I should have never opened lest I add another project to my already too long list of wanna-do's. A model gas engine looks like fun.

It is fun Rex and a learning experience just start with the right attitude and don't try to make everything perfect.

Ray

 

[Chris Hamel]

I have just used generic o-rings. (Like the kind you get when you buy an assortment kit at Harbor Freight) Most of my engines I was able to run a brake cylinder hone through. This gave me a good enough finish that o-rings have held up fine. When I cut the groove in the piston I take it real slow. A lot of trial and error. When I get close I might only take off .002 before test fitting.

 

[rdean]

Thanks Chris everyone has their own preferences good job.

Ray

 

[rogerl]

Ray inspired me to get my hit miss engine out and see if I could get it to run again. I changed the piston ring and the engine has good compression. I charged up my 12 volt battery last night getting it ready to go. I was poking on the internet and found a guy talking about the small hit miss engines. He said to use Coleman fuel or white gas because it works better for lower compression engines.
Coming home from work I stopped and bought some white gas to give it a chance. I put some white gas in the fuel tank and gave the flywheel a spin and the engine started. It took me a little while to get the carb set but the engine ran better than it ever had. I am thrilled. Now I am inspired to build another engine. What it will be I do not know. I need to think a little.
Thank you again Ray for all of your shared wisdom and your inspiration.

Roger L

 

[Chris Hamel]

Happy for your success

 

[rdean]

Roger be careful this hobby can be habit forming and all consuming as I can attest.
There are few things better than hearing and seeing an inanimate thing you have yourself made come to life. Happy yours has turned out so well.
I also use Colman fuel mainly because it doesn't have all the additives in it and it smells better too.
Thank you for the kind words.
Ray

 

[rwm]

I once used Coleman fuel to start a bonfire. Once....

That stuff is volatile. The fireball looked like a low yield nuc going off.

 

[Just for fun]

Thanks for all the info Ray! I never would have guessed O- rings were used for piston rings.

 

[David2011]

Roger be careful this hobby can be habit forming and all consuming as I can attest.
There are few things better than hearing and seeing an inanimate thing you have yourself made come to life. Happy yours has turned out so well.
I also use Colman fuel mainly because it doesn't have all the additives in it and it smells better too.
Thank you for the kind words.
Ray

The first R/C airplane to fly across the Atlantic Ocean, the Aerosonde “Laima” used Coleman fuel. You’re in good company.