Questions on a Roubo bench

[John Sanford]

Please don't use bicycle chain. It is not strong enough.

Jim, I find myself skeptical of this concern. Having been part of 400lbs cranking uphill at 15mph on a bicycle, the amount of force that a quality bicycle chain can transfer is substantial. Furthermore, the conditions that most bicycle chains experience are far harsher than they'll ever see in a bench being used. Perhaps you have the force calculations or busted chains to support your concern.

[Jim Ritter]

John here are a couple of pics of my real life tests. Somewhat subjetiive because I didn't have a scale on the handle but these are as I would use the vise. When I read as above where some want the longer Tommy bar to be able to lean into it I can only wonder at the forces generated. This is what I measured.
At the top of the jaw.



Twelve inches down from the screw.





Eighteen inches down from the screw. In this case just above the parallel beam in my vise.



Roller chain specs can be found on line, anyone can look them up. Will bicycle chain work, yes but there is very little safety margin. You don't have to buy parts from me, I just don't want anyone to get hurt if a chain breaks.
Jim

[Jim Koepke]

This may be where the misunderstanding started with my post:

another option of using a bicycle type chain

If my nomenclature was a bit better I would have said Roller chain or motorcycle chain.

Jim, thanks for showing the actual psi forces involved. This may save a few people from building something with less wood strength than is necessary.

jtk