Help figuring weight capacity for hoist frame

[6shooter]

As I'm building a new second floor structure in my barn, I'd like to put in frame work for an overhead hoist. The frame will be 2 steel I beams running parallel with my 2x10" floor joists and sitting with the joists on the support beams running perpendicular. Then I'll run another I beam section (hopefully on rollers so the hoist beam can travel the width of the bay) off the bottom of the 2 beam sections buried in the ceiling.

I've found what looks to be a pretty good deal on Craigslist; 1 section of 4" wide flange I beam 28' long, and another section of 3" wide flange I beam 14' long for $200 total. My design would be 2 12' sections of the 4" beam run the width of my shop bay, with the 3" section running the length of the shop off the bottom of the 4" sections. What specs on the steel do I need to figure out what my hoist capacity rating would be? I'd like to be able to safely put a 1000 lb hoist up there. Who's got the engineering skills here to figure this stuff out?

 

[Cobra5150]

Still missing some variables. What is the thickness and height of the I-beams?

 

[matt_i]

To get an actual answer you will at minimum have to consult the S- and W- shape I-beam tables and figure out exactly what you have. S- is a classic tall skinny section and W- is a wide flange. In other words is a 4" wide flange a W4 x 13 or an S4 x 7.7 or did you measure the flange itself as 4", which could be a s8 x 18.4...big differences here.

 

[6shooter]

I was able to find specs on the 4", it's 4x13#, the web thickness is .280" and the flange thickness is .345". Flange width and depth are both slightly over 4". For some reason, I can't find specs on the 3" I beam, still working on that.

 

[matt_i]

II think I understand but there's going to be a drop in the trolley hangers & connectors if the runway rails are above the 2x10s and the bridge beam is going to be underneath.

Not doing calcs yet, but 14' seems like a very long span for a 3" beam, even a 4" beam for that matter, if 1000# is expected as working capacity. To get full capacity across the entire bridge system you'd really need the same size members all around, because the load can be positioned all the way at one end with a runway rail supporting basically all of the load at its midspan.

 

[6shooter]

Thanks for the reply, Matt. The runway rails will sit on the same beams that the joists are on, so the bottom of the runway beams would be the same level as the bottom of the floor joists. If I make the other rail fixed instead of putting it on a trolley system, I could tie the 3" beam into each floor joist for the length of it. In which case, the 4" beams would just be "extra" insurance for making sure I can handle the weight. 1000 lbs isn't a necessity, 500 would do it. Mainly it's for lifting things out of the back of my truck, or removing truck beds and such.

 

[Cyberbear]

There are steel beam weight capacity charts on the Net, check them out.