Hook block dimensions

[admgosn]

Hi, long time reader and first time poster:

I am designing a crane pick with tight overhead restraints. The contractor needs to lift some temporary shoring steel beneath the existing bridge superstructure. One of the critical dimensions is the minimum distance between the lifting point on the hook and the main sheave at the end of the boom, see attached sketch. Some crane manufacturers publish this dimension for various hook sizes, ex: Terex/Demag AC-40, however many do not seem to.

Does anyone know of a database where this information is available? My only other option at this point is to contact the crane suppliers directly, however the ones I have already spoken to seem to be reading the information I already have right back to me. Right now I am primarily interested in the Liebherr LTM series hydraulic cranes, particularly the LTM 1090.

Thanks!

 

[JStephen]

Most contractors aren't going to go buy a crane for a particular lift, they're going to use what they already own or what the rental company already owns, and they would be the ones to ask.

It looks to me like you could cope out the beam for additional clearance, or build up a composite member, or locate another beam lower down to accomplish the same thing, or use a longer beam. If the lift is light, you could possibly use a jib and/or smaller hook to additional clearance. Would one of those all-terrain forklifts on either side be able to handle it?

 

[dhengr]

Admgosn:
You say.... “Right now I am primarily interested in the Liebherr LTM series hydraulic cranes, particularly the LTM 1090.” I’d go right to Liebherr for that type of info. That is literally dependant upon the hook the put on a given machine, and other misc. hardware on the machine. Most machines have some sort of a stop device hanging below main sheave at the end of the boom so they can’t pull the hook up tight to the tip sheave. I’ve seen them disable that to pick up a few inches of lift. Any chance you could apply new lifting points, out off the ends of the web of the cross beam? That would move you out further under the bridge deck overhang and also pick up a foot or so in your critical dimension.

 

[dhengr]

Jstephen.... offers the cleanest, simplest solution, just add some more cribbing above the large cross beam, to lower it.

 

[admgosn]

Thanks for the input. I put in a call to the place the contractor will be renting from, I just wanted to make sure there weren't any well known documents I was missing, which it doesn't appear that there are.

I agree that increasing the timber height is the easiest solution. Pending the answer from the crane guy hopefully it will be feasible.

Adding length to the beam is something we looked at but dismissed as the rigging beam the contractor already has does not have sufficient strength for the added span. He also wants to keep the overall length down to decrease transportation costs. I ran the numbers on bolting an extension to the lifting beam and that was also proving to be a challenging solution.

 

[dhengr]

Admgosn:
I was thinking more in terms of just welding new padeyes to the ends of the beam web, essentially in the same plane as the web. That would move you out about a foot and down about the same amount, not lengthening the beam that much. But, without any dimensions or loads it’s tough to tell.