Bridge Crane build

[rwm]

Awesome! Definitely project of the day/week/month!

Couple of questions/thoughts. How did you decide on the turn buckle corner braces? I would probably have gone with steel angle placed a ta greater distance from the corners. Is there any possibility of the perimeter "racking" from a swinging load? It would be really cool if you could add a motor to move the beam truck back and forth!

 

[rabler]

Fantastic! That was a successful deflection test for sure!

I also have a crane scale (2200lbs) which we have tested at 100 500 and 1000 lbs. For an offshore cheapie (1/8 the price for a calibrated, made-in-the-G7 scale) it is within 3% of the 'actual weights' as we know them.

I use mine several times every year, 3 times already in 2024.

I like how you managed to get the great coverage you did. Mine will be short of the sides of my shop by about 7 feet on one side, and 6 feet on the other.

Nice job!

That scale I used is also an import. I didn't calibrate it, hopefully that won't come back to bite me. Suppose I could still do something along those lines. The coverage was critical. One end of the reach is a large U of benches (with cutouts where the crane legs go through). I wanted to be able to hoist things onto the bench to work on heavier items. For example, 4 jaw chuck for the big lathe is over 300 lbs, and the 16" rotary table is in the same ballpark. Sure there are other ways to get heavy things up other than a crane or using your back (ouch) ...

 

[rabler]

Couple of questions/thoughts. How did you decide on the turn buckle corner braces? I would probably have gone with steel angle placed a ta greater distance from the corners. Is there any possibility of the perimeter "racking" from a swinging load? It would be really cool if you could add a motor to move the beam truck back and forth!

I thought about using some 2"x1/2" flats with holes drilled in either end. I used the turn buckle braces because I could use those to square up the top by adjusting the relative tension. The turnbuckles also allowed all of the free play to be adjusted out. My design includes a couple of extra bolt eyes like used for the turnbuckles that are intended as possible mounting points for a long shop-made turnbuckle to stiffen the entire structure, but after getting everything together I don't feel that's necessary. As far as racking/swinging load, the dimension parallel to the rails (perpendicular to the bridge) is better braced due to more turnbuckles supporting that dimension given 4 posts under each rail. With a free rolling trolley along the bridge, a load can't really transmit force parallel to the bridge beam to cause deflection in that direction.

I thought about a cable system to motorize the trolley. But it is more complexity that, at least at this point, I don't think is worthwhile. The trolley rolls pretty easily and is relatively light. The bridge is a lot of mass so rolling it manually from the bottom of the hoist chain creates some less predictable behavior due to momentum, so after simple testing that I decided that wasn't reasonable.

 

[rwm]

Excellent analysis! Thanks!