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dpb

wrote:
DT wrote:

says...

I am building an engine hoist framework, to hang a chainfall. ...
... The crossboard, ... will be 10' long. ...

A 4x4 will definitely not be strong enough.

Depends on the span, no? If M = WL/8 = 100L and S = M/1000
and 3.5 = sqart(6S/3.5), L = 71" max, approximately.

Yes.

But OP said 10-ft span which would be stretching it by quite a bunch...

I'm w/ the suggestion on looking at alternatives including biting the
bullet and buying a decent-sized beam--amongst other things, would allow
the hoist to be tracked, always a useful enhancement.

If use lumber, would suggest 2-3 2x8 or -10s minimum, but that's simply
a "feels about right" sizing, I didn't even estimate a stress number...

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