Hi Jim - starting topic's own thread...

"Jim Wilkins" writes:

"Richard Smith" wrote in message ...

"Jim Wilkins" writes:

"Richard Smith" wrote in message
...
...


...

The samples in your tester are similar to my centrally spliced gantry
hoist track problem. I'm trying to determine where to best locate
splice plate bolts so their holes minimally weaken the four 4" x 5.4
channels that comprise the track. Maybe along the web's neutral axis,
if the web has sufficient bearing strength or I weld on
reinforcements?

Another possibility is welding loose-pin hinge leaves under the lower
flanges to take the tension.
https://en.wikipedia.org/wiki/Knuckle_joint_(mechanical)

I'd like to help you with this, if I can.
Sorry - been preoccupied getting the "testing" thing going

I'll see if can find past articles where you describe the issue.
Do you have a webpage you post pictures and articles to - like I do?
So I can see what you mean?

Regards,
Rich Smith
--------------------------------

So far what I have is four 8' sections of 4" x 5.4 lbs/ft channel
iron, which are former pallet rack shelf supports, and a Harbor
Freight gantry hoist trolley to run on them when bolted back-to-back
like an I beam.
https://www.harborfreight.com/1-ton-...ley-97392.html

I built a lighter version from four 8' sections of 3" channel, with
two hung back-to-back from the front and rear roof beams of a storage
shed and two more making a temporary track extension out over the path
past the shed, where I set up the sawmill and load logs and beams
to/from a narrow trailer. The moving overhead hoist is very useful to
move logs onto the sawmill bed and adjust the partly sawn cants, by
suspending them in a loop of nylon rope hung on a pulley so I can
easily turn and level them. The rolling bandsaw mill head needs nearly
8' of clearance between the shed and the track's outer end support
post

That part works quite well for 8' oak logs and 6" square beams for
shed columns. I have to set up the overhead extension track by my self
and one channel's weight is near the max that I can maneuver with one
hand while inserting bolts with the other. Safe handling and a
shortage of covered storage space are why I don't use a single 16'
beam (~240 lbs) for the track.

The problem is 12' logs for roof beams, which could overload the 3"
channel and won't fit the 10' deep shed. I have another shed 19' long
by 4' wide that can hold 12' beams if I hang a crosswise travelling
hoist from its roof to move them in. It contains some already, which I
moved by an unsatisfactory temporary arrangement of the 3" extension
channels. I'd like to run the 4" channels out 8' over the sawmill to a
braced post beyond it and in through the shed plus 4' out the far side
to another post, for lifting logs off the trailer. In that case the
track will be centrally supported from above at the joint between its
8' sections, no problem.

The extreme case is joining the four sections to make one 16' gantry
track hung from tripods at the ends, perhaps to load a bulky appliance
onto a truck. I may never need it but I'd like to find a center splice
joint design that doesn't exclude or conflict with the central
mounting from the shed roof beam. Hopefully one design will work for
both centrally and end supported cases. That knuckle joint under the
tension flanges looks good because I could raise the ground-assembled
track by it and then lift and level the two outer ends separately, and
it won't transfer sag on one side into lift on the other, and shift a
shed column off its footing. I don't quite know how to design one to
weld onto the channel flanges, for instance how much to taper the
leaves to distribute the elongation and weld shear stress.

Specifically I'd like to know if bolts in tapped holes in the upper
flange can be considered part of the compression area and the accepted
way to reinforce the holes for splicing plate bolts through the
channel web. Does the reinforcement need to be diamond shaped to avoid
vertical welds?

Since I'm not on the clock I can customize bolts on the lathe and
hand-fit them with minimal clearance. They are all Grade 8, fine
thread, 150KSI.

Hi Jim

Can you sketch?
That is always helpful. I do that even when it seems we all agree, as
it can be amazing how a sketch reveals that the impressions are not
the same.

I'm thinking - maybe weld some brackets on top of the channel with the
bolted flange faces facing.
I'd normally wish there could also be a flange underneath - but the
close-fitting "standard" carriage would collide with it, so not
possible.

That said: if I understand correctly (big "if") - the loading may be
"cantilever beam" - tension on top, compression underneath.
Extending out of the shed?
Suspended - near the door?
In which case flange on top, nothing needed underneath as compresses
together would be bril.

Load analysis of the section - as channels tend to twist under load,
and is singular, I wouldn't dare use Euler-Bernoulli beam calculation
as works for symmetrical beams.

Sorry verbal description is hard to "see".

Rich S