From: no@no.no
Bob La Londe wrote:
> I would love to have a nice telescoping heavy gantry crane, but I don't
> need one often enough to pay the price for one as heavy as I would like.
> I do have a metal building with a large I-beam across the center. The
> building is 60' outside dimension, but the unsupported beam (bolted
> together in the middle at the peak with large flanges) is about 55 feet
> eyeballing the dimensions. Maybe less. The incline is about 4 degrees.
> I'm playing with the idea of putting a beam clamp on the I-Beam and
> putting a chain fall on it about 8 feet from the support column on
> that end. With a 16' eve height a 15' chain fall should allow for
> laying the hook on the floor. [...snip...] Bridgeport Series 1 CNC
> mill on a trailer in the shop right now. Depending on where I look
> it weighs between 2000 and 3000 pounds. [...snip...]
> My thought is the beam is certainly heavy enough if it was a short span
> like a gantry crane, but being a 55 ft span I might be playing with fire
> if I were to try a heavy lift near the middle. I am hoping near the end
> more of the load will be vertical on the support column. [...snip...]
> It would be a single (more or less) short duration load so that I
> could lift the mill, roll the trailer out from under, and lower the
> mill onto a heavy pallet, so it can be positioned with a pallet jack
> and eventually set on the floor with my cherry picker (engine
> crane). The last part is how I moved, positioned, and set the South
> Bend mill (which is over 3500 pounds). The cherry picker won't go
> high enough to lift the mill off the trailer.
> I don't know how dumb my idea is, but I'm probably going to go for
> it. The load time would be measured in a couple minutes, but my
> thought is something like this is either going to be strong
> enough. Or it isn't. [...snip...]
You might run a test, lifting say 800#, 1600#, etc while measuring
mid-ceiling deflection, eg with a Bosch laser measure, then
extrapolate to "safe" maximum weight. Of course, if the deflection is
too small to measure (eg <5mm) then probably no worries. Or if it's
several inches, lifting via the ceiling beam would be a no go.*
It's the in-between deflection cases that would be harder to decide...
Whether you can reasonably extrapolate also depends on how the support
column at the wall is braced. Given the 16' eve height, Euler
buckling could occur without warning if the column's not braced both
ways when you exceed critical load. Also see***.
* If ceiling beam lift is no go, you might end up using dual rows of
stacked cribbing, eg crib a platform beside the trailer up to trailer
height, move palleted mill onto platform, and use pallet jack to
alternately take out layers of cribbing.**
** Say pallet jack has 3" min and 8" max to top of forks; and suppose
24" of cribbing between floor and mill's pallet; and 16" of cribbing
between top of forks and pallet. Raise jack a little, remove 4" of
cribbing, lower jack 5", remove 4" of cribbing on jack, raise jack 5",
etc. Ends with forks under the pallet, not in the pallet.
*** If the wall's well-braced you could put your beam clamp nearer the
wall instead of 8' out, and have a winch line across the shop to hold
the chain fall hook out from the wall. [However, if the clamp were
right at the wall I think resultant forces would be about 90% on the
chain fall and 45% on the winch line, which sounds like a high enough
sideways force on the wall to raise the possibility of some exciting
video footage. ... In the grocery store a couple of weeks ago, I
heard one guy say, "How's it going, Bill?", and Bill replies, "Going
great, just great! But it's early enough the whole day could still go
sideways."]
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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