Slow Speed Engine Design

[Rustkolector]

In the design of a 4 stroke, throttle governed, SI, 1” bore, multi cylinder model engine, what specific design features should be incorporated to enable nice steady slow speed (300-400 RPM) model operation? This might be wishful thinking on a 1” bore x 1.125" stroke engine, but I would like to think that it can be done. Friction reduction measures, flywheel selection, fuel mixer design, compression ratio, cam profile, valve timing, ignition timing, and fuel type all come to mind. How to prioritize them, and quantify them is where I need advice. I would like to use available dual 5.5”-6” CI spoked flywheels. Other component material selection is open. Any experience, thoughts, or ideas would be greatly appreciated.
Jeff

 

[Kermit]

I think the best way would be to increase the stroke length. All the other methods you mention just sound to me like they make the power stroke "wimpy" to slow down the motor.

Is the 1 inch by 1 and 1/2 inch design set in stone?

(Edit: Sorry for the pointless reply, I should read the question better, eh?)

 

[Rustkolector]

The stroke is 1.125", and possibly 1.188". The engine is intended to be a slow speed running engine modeled after early 1920's stationary designs similar to the 3 cylinder Fairbanks Morse engine kit by Pacific Model Design.
Jeff

 

[Foozer]

The stroke is 1.125", and possibly 1.188". The engine is intended to be a slow speed running engine modeled after early 1920's stationary designs similar to the 3 cylinder Fairbanks Morse engine kit by Pacific Model Design.
Jeff

The old slant 6 had a bore stroke ratio of 0.82. You could idle em down to near zero. A 0.975 bore with the 1.188 stroke matches up with that old low RPM stump puller.

 

[Jadecy]

Thinking about the basic physics you would need as much inertia as possible and a strong enough power stroke to give the mass enough energy to spin. Getting as much flywheel as possible into a small package is the trick. You may think about butane or propane as a fuel. Most small gasoline engines run too rich. This is easier to control with a gas than it is with a liquid fuel.