Stevens's Marine Screw Engine Recreated

[Sanjay F]

Mine is a round peg in a square hole!  and mine does have the rocking motion you described, I did wonder what caused that

[PaulR]

  Must be lateral forces with nowhere to go ending up causing rotation (or something like that!).

[Jasonb]

Nothing I can see with the naked eye. I'll video it tomorrow but compared to Sanjay's there are very small gaps (approx 0.1mm) between crank disc and the screw head to the Scotchyoke so it can't wobble even if it wanted to.

[Jasonb]

Not much play to be seen

<a href="https://www.youtube.com/watch?v=cWJWjgOQFTE" target="_blank">http://www.youtube.com/watch?v=cWJWjgOQFTE</a>

[PaulR]

Ah, I see you've got a bearing surface on the crank pink under the yoke and the screw above which is why you're wobble-free