Welding a chain link

Thanks for that link. Very interesting site.

Spoken like a true gentleman, and I for one, appreciate a man who honestly makes and admits mistakes. Rare to see on these NG's. Thanks for your honesty.

Rich

Upon thinking of this at an odd moment ............

If a link fails, does it not distort somewhat from being bent out of shape? Now, to rebend it so you can weld it, and it passes through the sheaves of a hoist, doesn't that rebending further weaken it? So, even if one does achieve an acceptable repair on the link would not the other side of that link now become the weak point? And heating to weld also weakens it.

I'm just not a fan of using repaired chain on anything critical, like overhead lifting. And even using it for a drag chain can be dangerous, as when any chain parts, stuff usually goes flying. That said, I have used cold shuts, cold shuts welded shut, and chain ends welded on to buckets, chains welded together, and welded on to drags and tractors and lots of things. It's just when you really get pulling on things or lifting heavy things that I get nervous, as I have seen enough failures, and the PTSD kicks in.

I've done lots of marginal things regarding rigging, and most worked out fine. Just get to a position of safety and observe.

Steve

I do not see how it can be done any other way in this case. Any other method will not travel through the drive pulley.

"Bob La Londe" wrote: I do not see how it can be done any other way in this case. Any other

^^^^^^^^^^^^^^^^^^^^^ If the chainfall manufacturer buys the chain in spools, so he must open, close and weld the link. Or do you suppose they buy the chain with the required number of unfinished links?

Make surer your weld is smooth, so there are no stress raisers.

>

How does one prepare a root deep enough to get a good weld, then grind off enough to pass through the sheave without degrading the strength of previously described weld? And especially with TIG, how does one keep from getting contamination from the back of the piece getting welded? I know that chains can be welded. I also know that it weakens them a lot, too.

The best method I can think of is to replace the chain.

Steve

The ends are secured either to a dead man, or to a pin in the hook. At the manufacturer, chain is bent and resistance welded one link at a time, but then it has to go through the heat and quench sequence, so making one link to join two lengths of chain together would be problematic if it were attatched to a hoist.

I wonder if that type uses the resistance welding process, or some other. I guess if you had it in a flooded argon chamber (or some other shielding gas), you could get a passable weld on there.

Steve

I think you are missing the basic concept here. HE IS NOT WELDING THE LOAD CHAIN. He is welding the drive chain. A chain fall uses two different chains. One lifts, and one operates a gear reduction drive that moves the lift chain. I have lifted the front end of a truck with one without lifting my feet off the ground by pulling on the continuous loop drive chain.

For example:

Couldn't find one that showed the full length of the chain, but you can see it uses a heavy chain for the lifting chain and much lighter chain for the drive chain. A 2/0 twisted wire dog chain will hold a 150 pound dog lunging against the end of it (for a year anyway). (No I don't chain my dogs so don't go ballistic on me.) That's got to be close to 1000 pounds of sudden force. Much worse than steady force. The drive chain on a chain fall is much heavier than that and the most it will have is the force of a 250 to

300 pound man hanging from it if they are trying to exceed the capacity of the chain fall. If they are using the chain fall within its capacity it takes about 100 to maybe 150 pounds of steady vertical force to fully operate the mechanism. I'm not sure what you are expecting to break if somebody does a good job of welding the link.

Is it using TIG that bothers you? I do not know anything about TIG, but I would certainly have faith in a 1/4 chain link being welded and having the strength afterwards to hold 300 pounds if I used my little flux core wire feed. (yes I would chamfer the edges of the link faces where it comes together to make sure I got lots of penetration and material joining the ends.) I have welded chain links onto trailers to be used as tie down points before, and none of them have broken and none of the welds have broken. Some of them have been in service for 15 years, and I know that shifting loads can far exceed anything the drive chain on a chain fall will see. The box type tie downs on most manufactured trailers are just hot rolled mill steel. Much softer than a chain.

I suppose I might be tempted to heat it and oil quench it afterwards in this application, but I'm not 100% sure that would be the best answer. I might be more tempted to leave it "soft" so that I could see if it starts to distort over time. If it did I could just cut it out and do the next link. Quenching might cause it to crystalize and break suddenly (If it broke which I doubt). I do not know if quenching would be a good idea or not. For that I would defer to somebody else's expertise.

"Bob La Londe" wrote: I think you are missing the basic concept here. HE IS NOT WELDING THE LOAD

^^^^^^^^^^^^^^^^^^^^^ In an earlier post, Curt Welsh corrected me on a similar point, and now I have a chance to do the same to you. There are two types of chain falls: gear-driven and differential. From everything in the OP's posts, it is clear that he is working on a *differential* chain fall, which uses a single chain passing over pulleys of two different diameters to produce a large mechanical advantage. The load bearing chain also passes through the hands--dog chain won't do :-).

What diameter round rod was used to make the 3/8 links? How much ultimate load do you wish to lift? Does one, two or more runs of the chain support the load through a pulley or sheave?

+1 on that. The OP's "chain fall" hoist uses ONE CHAIN. It is a continuous loop, with no free end anchored to hook or hoist body. I've got a couple of them. Apparently they have fallen out of favor---I can't find a new one for sale.

Small picture and description of the differential chain fall operation here:

Perhaps because Chinese chain hoists are available from several low-buck suppliers.

Questionable source for lifting equipement. Are these parts certified and load rated to current standards? Have all load bearing components been inspected and NDT tested and certified as safe for use?

If this is a chain certified for lifting, then it will be better than simple mild steel and will almost certainly be high alloy and heat treated.

TIG would not be my process of choice for this job.

316 or other SS would not be my choice for filler material.

Maybe (probably?) not.

This is a pretty small load and well within the capability of almost any

3/8" chain especially with two load bearing parts, (but I would not want to drop it on my body). The problem will/may probably come WHEN (not if) you (or somebody else) tries to use this hoist to lift something closer to the normally expected capacity of this size of chain and hoist.

With respect, and IMHO, this really is another situation where, 'if you have to ask, then you can't.'

ALL lifting equipment should be certified. Is the chain you are proposing to use certified for lifting? Are you qualified to certify this repair/fabrication? Are you using a certified procedure? (The chain manufacturer may (but probably not) be prepared to supply an approved procedure.) Are you a certified welder? Do you have quality control to certify the work? You need to be able to answer yes to ALL these questions.

Be aware of your possible legal liability.

New equipment starts to look like a bargain. Good luck.

So I welded the link up. It looks nice. I do not do any overhead lifting. I think this will be okay. (One risk is my assumption that it is inconceivable at the present--utterly inconceivable--that I would ever get under any of the loads I would lift in my shop. Yeah it is inconceivable now but....)

As for the coating, it did come off with the toilet bowl cleaner. I assume that is muriatic acid based?

Thanks again for the information, cautions, and recommendations.

Best, David

I assume this is the "loop" chain on the pulley (gear drive/brake) side of the hoist.

A new C/M hoist will have an open link somewhere so you can spread the link and shorten the loop chain. You can't pull hard enough to open the link in use without the gear drive failing.

C/M used to also sell these chains and open links if you needed to make a longer "loop" chain.

Matt

replying to Leo Lichtman, Jim Vanderhoek wrote: