# 20 cc engine



## mungalhead (Jul 6, 2017)

Hi Folks
I am looking for plans / kits for a 20cc or greater 4 stroke engine this (I hope) would power a quarter scale Sopwith Pup. any ideas on where I might get plans or kit would be greatly appreciated.
Regards
Alan


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## WOB (Jul 6, 2017)

What about this? http://www.hemingwaykits.com/acatalog/Aero_Twin.html    Increase the bore to 1.0" and you have 22.5 cc.

WOB


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## mungalhead (Jul 6, 2017)

Thanks WOB
Is this modification all that would just be required ? 

Regards
Alan


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## deverett (Jul 6, 2017)

If you want a real scale model, you need a real scale engine.  So how about a 1/4 scale Clerget rotary?  Drawings are available, but not sure where, but http://www.modelenginenews.org/ed.2008.03.html#t3  would be a good place to start.
Mind you, the plane might be a bit tricky to fly with it!

Dave
The Emerald Isle


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## WOB (Jul 6, 2017)

There will likely be a need to slightly increase the combustion chamber volume to keep the compression ratio from going up excessively.  An increase in CR will increase power in a spark ignition(gasoline) engine.   For glow plug ignition( methanol), a CR of about 8:1 is needed to keep ignition timing in the desired zone.  Also, the cylinder liner OD might need to be increased slightly if the bore size is increased, but I have not seen the plans.  Obviously, the head gasket sealing surface will need to accommodate the new bore size. In principle, any small engine design can be scaled up or down as desired if proper attention is paid to the critical dimensions.

WOB


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## mungalhead (Jul 7, 2017)

Excellent chaps, many thanks,

I have dealt with Hemmingway before and found their kits excellent so will give serious consideration to Aero Twin


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