proper woodscrew pilot hole size

[jim gossage]

Hi Jim
You can make good end stops by drilling cross holes and putting in bold. These would not need safety chains.

The center rail should not cause racking so if it moves well enough as is then it's good.

Racking will probably be worst with the load at one end of the bridge. A pole with a hook and a helper might ease the travel.

As to failure, you could load test it at 1000 pounds with the load at each corner of the range (while staying out from under). Then divide 1000 by whatever safety factor you choose and use that as your system capacity.

Thanks Tom. I unhooked the trolley on the center channel and racking was not better. I am leaning towards improving the racking by replacing the 3 bridge trolleys with 3 angle irons each with 2 trolleys in line with the ceiling channels. Any recommendation how far to space the trolleys along the angle iron to minimize racking? Seems like the farther apart the better for racking, but the downside will be loss of travel distance for the hoist. would 12" be enough?

[Tom Bender]

It's going to depend on the trolleys. How well do they travel when there is a side load on them? Industrial trolleys sometimes have side guide rollers and run on patented rails. The trolleys you are using are best used for a monorail crane. You have made an underhung bridge crane.

Also, they will handle differently when loaded.