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Pete Berry26/07/2021 11:59:13
28 forum posts
7 photos

I have recently completed building a CENTAUR ENGINE. It starts and runs well but it does jump about quite a bit.Not sure if the balance would be improved if I used an aluminium piston instead of the cast iron one. I would be interested to hear how other people's engine perform?

kevin laxon26/07/2021 13:04:49
7 forum posts

A friend has made several hit & miss open crank barn engine's,we have found the one's that jump about as a rule of thumb don't have the couterweights on the inside of the flywheel rim 180° from the crank pin,some also have the flywheel lightened inline with the crank pin,I know of the centaur but have had no dealings with one,hopefully others will know more.

MichaelR26/07/2021 15:58:43
441 forum posts
83 photos

I built a Centaur and fitted a aluminium piston but not for the purpose of reducing rough running but for my own liking, I don't think a cast iron piston will contribute to rough running.

Video of my engine running just sitting on a non slip mat. engine now has a new owner.

Edited By MichaelR on 26/07/2021 16:01:56

Pete Berry26/07/2021 19:16:50
28 forum posts
7 photos

Thanks Kevin I will give it a try.

Pete Berry26/07/2021 19:22:33
28 forum posts
7 photos

Hi Michael your engine certainly runs smoother than mine , I have some ballist in the base but I still have to hold in down. I think I will try an ally piston.

br26/07/2021 19:24:37
697 forum posts
3 photos


Thanks for posting , Looks superb.


Pete Berry30/07/2021 10:46:21
28 forum posts
7 photos

Problem solved. I balanced the crankshaft as per E Westbury,s instructions in his book "Model petrol engines" I had to increase the size of the balance weight which now have a radius of 3 inches. The engine now runs much smoother without jumping around. smiley

MichaelR30/07/2021 11:08:58
441 forum posts
83 photos

Pleased to hear you have solved your engine problem and with not a great deal of extra work.


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