Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Why do Jin's H&M engines jump around so much?

I've watched a heap of other home built Kerzel designs and they don't.

Unbalanced.
Lightweight materials.
No real base.
Size and measurements are easy to scale, not so gravity or torque or momentum.

It's quite a torque "kicker" & needs a lot bigger box & counter weight than would seem !

Even using a Solid Oak block of same dimensions will Not keep it from firing torque kicking about on my year old M90 ! ...Doubling the stock base length + flywheel end offset Iron weight gets you Started !!

Physics won’t be denied. Think of this or any engine as a rotating mass that twists, such that it tries to take the surrounding mass with it. As the speed of the rotation is rapidly altered, the directing of the twisting force momentarily reverses, and the mass tries to hop. If that mass has a long enough lever arm on a short enough base, it will try to twist instantaneously, before relaxing just as fast, and you get a hop. 

My M91 isn’t the slowest or most steady runner, but it no longer hops. The longer, lower, most importantly longer, and heavier base defeats the torque.

Are the bases crap pine ?
If then how about some of those dense aussie timbers that repel nails and screws

Dennis I have some ideas along those lines with some nice thick planks of Aussie Ironwood.

Still not sure 100% of the end design though.

I simply glued a couple of battens on to the sides of the wooden box. This allows you to easily clamp the engine to the bench you are running it on.