Critical calculations can take many forms when working with a model where a miscalculation might only cause an embarrassment, rather than a career-ending catastrophe. In-depth calculations, modeling, empirical data, scaling, gut-feel intuition. All are good, and with model building, for me, I just want to feel relatively confident with the choices I make. The type of "proof" that would stand the scrutiny of a design review team isn't necessary for me. In retirement, I am finished with that level of stress, ha ha.

My design is based very loosely on the iconic GM Detroit Diesel 2 stroke, particularly the 71 series. It lasted for 60 years in everything from the single cylinder 1-71 to a V16-71. Dirty emissions finally killed it, but the design stood the test of time and engines could go a million miles, with some TLC along the way.

Simply scaling the engine, 4.25" bore x 5.00" stroke, with a piston pin of 1.50" diameter, here is a very simplified approach.

Using a 1/4 scale, piston dia = 1.062" and piston area = .88 sq in vs 14.2 sqin in the original, for a factor of 1/16, so the force in pounds on the piston is 1/16 of the full size engine. but going with a simple 1/4 scale of the piston pin, to .375"dia, taking into account the moment of inertial and the length and deflection, the deflection would be still be 1/4(?) the original, but the force is only 1/16, so scaling the pin should be fine. But the various bearing areas will be 1/16 of the original, too, so the bearing loads in force per area, will be similar to the original. So the bearings will need to be as robust as the originals. But also, going with a pin larger than 3/8" dia would reduce the area loading on the bearings.

Given that the swept cylinder volume will be 1/64 of the original, is it a reasonable assumption to estimate total power as 1/64 of an original 1-71 diesel?

I know these are just kitchen-table napkin calculations, but honestly, if I am not comfortable with these, I assume that something is not right.

Just a lazy approach, I guess, but digging too deep, for me, starts to take some of the fun out of the project. I prefer making chips at the machine, LOL. But we are all different.

Lloyd