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RE: Beams for gantry

To: "Shop Talk" <shop-talk@autox.team.net>
Subject: RE: Beams for gantry
From: "Conrad" <conrad@conrad.uk.net>
Date: Wed, 28 Aug 2002 17:01:09 +0100
Thanks again for you input Jon.

> deflection. This is just a quesstimate, but an I-beam of 
> sufficient stiffness might be 6 inches deep. That is why I 

Hmmm. I cant really accommodate that - might just about squeeze 5
inches, but I really don't want to rework the roof.

I only have a budget for steel, none for custom fabs or 'getting people
in' so I'm after best guess and perhaps seat of the pants type help. I
will have to take responsibility for something collapsing of course, and
I generally work such that there is a backup if something breaks (the
big crack in the king post on my JCB has taught me this). This is fast
becoming a complicated looking task but it would seem silly to give up
because of that. I'm pretty sure if I bung enough steel up there I
should be able to make it pretty strong.

Options I appear to have for increasing strength but not height are:

1. doubling up on the beam across the front
2. using a much bigger beam on its side (say a 7"x4")
3. welding/bolting 2 4"x2" lengths of channel back to back giving a
4"x4" beam
4. adding more roof support beams (spreading the load on the gantry).
Cold get expensive on trolleys.

This all adds weight, but the side supports for the beam are very
strong, double width concrete blocks. I like the sound of option 3,
which would give a very low profile beam, with a thick vertical section.
Would that appear to be on the right track? Could I then do the same
with the roof supports, using 3"x2" channel? That would give me a 4"
increase in headroom, just about perfect.

Conrad

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