"Ned Simmons" wrote in message
...
On Wed, 18 Mar 2009 08:57:36 -0500, Tim Wescott
wrote:

On Wed, 18 Mar 2009 11:57:21 +0000, _ wrote:

One of the projects involves both re-doing the garage and lifting a ford
4-cyl motor out of a car. There's a fellow selling an I-beam locally,
13 feet long, 8 inches deep, 4 inches wide (no web thickness specified).
This would span the garage nicely - could I rely on it to not bend if I
hook up a hoist to the centre and lift that motor? Supported on the
ends only...

There are engineering tables for that sort of thing. I don't know where
the right place to look is, but that's all been reduced to "look it up
and run a couple of numbers".

The tables are in the AISC Steel Construction Manual, but first you
need to know which table or chart to use and how to apply it
appropriately. There's lots of jargon and abbreviations in the data
that the user needs to interpret and then determine whether any of it
is relevant to the case at hand.

For example, the charts and tables assume a factor of safety for
structural applications which is much lower than the practice for
overhead lifting.


As Lloyd pointed out, mount that sucker so it absolutely positively
cannot turn on it's side or fall off of it's supports.

That's a good start. g

--
Ned Simmons

Ned: Baumeister and Marks Standard Handbook for Mechanical Engineer that I
have just about ground into unreadable by repeated usage, and I'm not a
mechanical engineer, has a table 2 on page 5-32 that shows a simply
supported beam which means the ends are only restricted vertically and not
welded into a vertical column max deflection is:


f =
(W* (5* L^3))/(384* E*I) W= weight applied to center of beam
in pounds

L= length in
inches

E= 29* 10^6 if
it is steel

I = the moment
of inertia of the I beam section. Note the way to calculate this is found
on page 5-38 of the same book. The drawing is a bit messy but the I factor
does depend on the web thickness. It is a no brainer if you have the picture
from page 5-38 and all the dimensions from the I- beam