Balancing Engines

[Ken I]

sum the effects of all the separate elements. This will give total force applied to the crankpin expressed through the center of rotation.

Done that - you will still come to the same results expressed above.

Entropy45's method is going to produce the best overall ballance for a single cylinder engine.

Best is not fully ballanced - which is simply impossible on a single cylinder. Yeah I know nothing is ever fully ballanced but a single cylinder is the worst case.

A friend of mine who raced bikes - once got the bright idea to reassemble a two stroke twin so that both cylinders were up at the same time (this crank assembly permitted this error) - he called it a "twingle" - he was hoping to reproduce the torque of a single thumper - it didn't work and the vibrations gave you double vision.

Ken

 

[GreenTwin]

I stumbled across a reference to this post somewhere while reading threads on this forum.
Now I can't find the post I was reading.
LOL, I am certainly losing my mind.
I had totally forgotten about this thread.

This was started many years ago in a former life.
It was not so interesting what I posted here, but what others added into the mix, which really gave me some good ideas on how to balance an engine using Solidworks, and not using calcuations.

Time is erasing my memory slowly but surely..
This one is rather hazy in my memory.

I will have to re-read this thread, since I am still building engines, and still need to balance them (more so as I get into IC work).

Edit:
I recall finding a Yamaha 650 twin in a lake one time, and I recovered it and rebuilt it.
I was rather surprised to see that both cylinders moved up and down together (if my memory is correct).
Makes sense if you think about it, since you can fire cylinder the cylinders 180 degrees from each other using this configuration.
It did vibrate a lot when it ran.
Great bike but I much prefer the Yamaha 500 single, such as the TT offroad engine, or the street version of that, which I forget the name.
The Yamaha single had a perfectly flat torque curve (I have a printout), and it runs like a hairy gorilla, ie: you better be hanging on very tightly when you open the throttle, regardless of what gear you are in.
Someone interviewed the engineer in Japan that designed the TT500 engine, and he said it was a very difficult design, but he finally got it optimized in the end. He said there was no good way to balance it, and so they mounted the footpegs and other items in rubber.
You could literally plow fields with a TT engine. It is a beast.
.