Special Lifting Sling

[Nige]

I need to have a non-standard sling manufactured. What's the opinion of the lifting experts as to how feasible this idea is.

I have a lift where a knuckle-boom crane is used to pick the transmission out of a vehicle. The lift is 7000 pounds and access is very difficult, there is no direct pick from overhead, hence the knuckle-boom. The sling attaches to 3 points, two on the front and one on the rear. We hook a 2-leg sling to the front and a come-along to the rear. The biggest problem at the minute is trying to get all the lifting gear to fit on the crane hook for lack of space. To make things even more complicated the transmission won't come straight out, it only has about 6" of forward movement until it hits the chassis. So after moving it forward a hair, as it is slowly raised with the crane the come-along has to be lowered so that it ends up angled a bit like a spaceship so that it can be lifted right up & out.

Now my idea of the sling was something like the illustration below. The 2-leg chain would attach the the front end and a 3T come-along would be hooked to the ring on the rear. SWL of the complete sling would be somewhere around 10,000 pounds to suit whatever standard chain size was closest.

Does anyone have any comments on this idea..?

 

[old-iron-habit]

Any decent rigging supply should be able to make what you want in short order. We had many sets of specialty slings made pretty much as you describe. Normally we had the two fixed lengths made of cable and the third attachment point, as you show would be hoist chain. By using cable they would make them in 30 minutes or so while we waited. The ring to put on the hook was a stock item.

 

[crane operator]

I think it will work fine, I like making short rigging chains with D-rings and adding grab hooks or a master link, so you can change lengths as needed, so its not single application only.

They make special rings and grab hooks now, that are great for adjusting. The lift all one, you would have a chain for each side, plus you could put your come-along to the middle one on a short chain. Put the hooks on with hammerlinks so you can remove and reinstall them and you could get in some tight places. I kind of like the lift all rig, better than the grab IQ system, because it separates them up a little. In your crowded area the grab IQ can end up being kind of a cluster of chains.

I have two 12' chains just like the one on the left in the lower picture, so I can have a 4 leg 12' sling with only two rings on the hook, but I imagine on a transmission, you'll want a pretty short rig.

 

[crane operator]

You can also get this kind of chain link connector, so your shortener is right in line in the same chain.

Another picture of a lift all master link: With this, you could actually fold over a short section of your extra "middle" chain, and slide them in the center slot, making a 6" loop to hang your come along from.

 

[Cmark]

Don't know if it helps in your particular situation, but where you've got limited headroom, in the past I've removed the hook from the crane and attached the rigging directly to the clevis on the end of the boom. Of course you lose the ability to swivel the rigging so you have to be mindful of where you position the crane but it will gain you about an extra foot of headroom.

 

[lumberjack]

You could use a large shackle as a master link to resolve the three slings to the one point on the crane. I had a Crosby 1.5" shackle for my knuckle boom, pulling across the legs, it was still good for my cranes practical capacity. I used it like an openable master link.

 

[Nige]

Thanks to all for the suggestions.
The leg length of the chains is probably going to be no more than 3ft max, I haven't actually measured what we're using now yet.
My problem is not being creative with lifting gear myself (we've all been there, right?) but preventing other people with less experience becoming creative without fully considering the implications of what they are doing. The last thing I want is someone getting injured on my watch as a result of "uninformed creativity" with lifting gear. So my basic idea was have this sling made up and then connecting the rigging becomes effectively a mistake-proof 3-stage process. I can justify the cost of having a special sling made for this one job.
I hate to use the expression idiot-proof, because in my experience every time you try to make something idiot-proof evolution simply develops an improved class of idiot.

1. Hang sling on crane hook.
2. Hang come-along on empty ring of sling
3. Connect all three hooks to the corresponding lifting eyes on the transmission (no shackles required, the eyes are big enough).

........ and Bob's your father's brother.

 

[crane operator]

Sorry for all the adjustable advice, I try to make things universal, but I see now where you're coming from.

If you want to make it so they can't get creative, make it with cables instead of chains. If you have chains, they will try to shorten it or lengthen it with bolts, wire, who knows what. Rigging shop can make whatever you need with a master link and cable to hooks on the other end.

http://www.uscargocontrol.com/Lifting-Slings/5-8-2-Leg-Wire-Rope-Slings-Domestic

1/2" cables would be be pushing your weight limit if they are short on angle, but 5/8" should do it:

• 60° = 6.8 Tons
• 45° = 5.5 Tons
• 30° = 3.9 Tons
• Manufactured with Crosby® Hardware
• Call 800-404-7068 for more options

Have them make you one like this, with 2 legs and add a second forged oblong link on the master. I prefer Crosby, or CM (columbus mckinnon). CM lately has been offering both US and foreign components (china), so watch what your getting before you order.

 

[Tradesman]

Crane ops post made me think of these two charts that are on a poster that my rigging supplier gave. I took a picture of them and keep them in my favourites on my phone along with a copy of my load charts I reference them quit often.
And I would suggest getting your rigging supplier to make something like your picture then it will be as you say somewhat idiot proof and will be tagged with all appropriate data