Oscillating Parasites

Hacking off the crankshaft webbing: how’ll that affect engine operation?
This video was on my mind while I was working on my previous post on the subject, but I ran out of steam, so I called it good and went to bed. But now I've had a day to think about it, and I've decided it needs to be here.

I've watched a few other Garage 54 videos. They are mostly pretty silly, but sometimes they have a kernel of real information. I suspect they are somewhere in Russia, the Lada is a Russian car and they seem to have an endless supply of them.

I'm surprised the engine ran as well as it did. Balancing the crank has been an item of religious devotion among car guys since forever, and here it looks like it is nonsense. Of course, you can't really tell what kind of vibration you are getting from the video, and we don't know how long the engine will last without the counterweights, but I have to give the guys credit for even attempting this.

I was thinking about the bit about "parallel twins with crankpins not at the traditional 360 degrees, but separated by 76 degrees". That would be optimum for one case, but each piston comes to a stop twice in every rotation. Each time it reaches the top or bottom of a stroke it stops, just instantaneously, but it stops. To minimize the transfer of momentum you would want to space the crank pins 90 degrees apart. It wouldn't be optimum for that one case, but it would apply equally to the four times pistons would stop. That should help smooth out the crankshaft's rate of rotation. It might make the idle a little lumpy, and who knows what would happen at speed. Someone should try it.

Then I thought a little more and I realized any engine with an even number of cylinders is going to have this same 'transfer of momentum' problem, so an odd number of cylinders might be a solution. There have been a number of three cylinder engines like the Kawasaki 500 two-stroke, Triumph motorcycles and Geo Metro cars. Audi even had a five cylinder engine. I wonder if anyone has ever bothered to measure the variation in crankshaft rotational speed as an engine completes a single cycle. Who am I kidding? Of course they have, it just hasn't found its way to my computer screen.