I also do model engineering and have built both steam and internal combustion model engines, so have done a fair amount of research in these areas.
Theoretically, the V configuration as in this engine should produce some pumping action in the crankcase. The big issue here is scavenging. The leading cylinder would be over scavenged while the other would be starved. This engine with the 90 degree V might run but it is doubtful if the second cylinder would have enough fresh mixture to fire.
Now if the V were smaller and in the range of 30 to 45 degrees, this configuration might have a better chance of performing since the pumping action would be greater. In order to balance up the scavenging one could use a single bypass cylinder for the leading one and a double bypass cylinder for the trailing one. Of course this engine would have to run in only one direction.
This is an interesting idea and I might just make one to satisfy my curiosity.
Orv.
Hi Orv,
I agree with what you are saying, a common crankpin twin cylinder two stroke set at 0 degrees (or cylinders parallel) is the best primary pump configuration and when set at 180 degrees it simply doesn't work since one pistons motion cancels out the other (one rises as the other falls).
So logically any angle that approaches 180 simply gets worse as the cancellation effect becomes more prominent.
But what gets me here is two things -
1/. The common crank pin length and the massive primary volume that it lives in, please see the supplied pic and visualise where the back plate must finish at inside the lower case. That lower primary volume must be huge when expressed as a ratio against the secondary or swept volume.
2/. Also when the lead piston starts on its compression stroke the primary volume is supposed to be lowering its pressure in preparation for the intake but the following piston is still descending mid stroke and negating part of that ...... and since its a reed valve engine there is no getting around the pressure demands.
Give it a crack, I am curious too to see if you can get a runner out of this configuration.