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Closed Loop of 3/8" Chain

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DAVIDSTECKER

Mechanical
Mar 23, 2005
525
US
I've sort of stumbled into a new market for one of our stock product lines.
I'm using our small capstan by removing the smooth rope barrel and replacing it with a chain pocket wheel for 3/8" chain.
The end users do not have a lot of details regarding the chain they've been using but the samples they have supplied have lead me to Grade 100 even though it's not being used for lifting.
I have not been able to find a connecting link that will fit inside the pockets and have equal working load, so I'm left with the concept of cutting a link in half and re-welding it to form a continuous loop.
Looking at ASTM A973 material requirements, would I be in the Ball Park to say that Grade 100 is similar to 8630 even though ASTM caps the Carbon at .35%?
I would first like to ask if anyone knows of a connecting link that is equal to the strength and size of a 3/8" Grade 100 chain link.
My machine should deliver at least 6,000# of pull.
If my assumption of 8630 is correct, can any one recommend a welding procedure and filler metal?
I my assumption is wrong, please enlighten me as to what it really is.

2022-01-06_09.10.18_jrxvsm.jpg
 
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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik
 
You've got to buy name brand of you want certified for lifting ratings. Crosby sells a 3/8 inch connecting link with a WLL but it's only 2800 lbs. However, if you're not using it for lifting you can usually increase that rating. Lifting is 5:1 or higher safety factor but pulling usually only specifies a 3:1.

Wildcats for chain don't usually engage the chain so closely. They're usually cast and have lots of draft in the chain pockets which makes lots of room for variances in the chain. These are messy, clunky machines.

If you're forming a loop why are you not using roller chain?
 
WLL of the CM Herc-Alloy is 8,800# with 4:1 design factor.
As mentioned early, this is NOT a lifting application.
Tug: We actually manufacture anchor windlass' for stud link chain ranging from 3/4" to 3", and most of our Wildcats are cast.
One of our latest projects is the Coast Guard OPC.
I have "inherited" this design that has been apparently been used by the manufactured home building industry for many years.
I got involved because a lot of the old equipment is wearing out and the original suppliers are now gone.
My capstan looks like the old stuff so they've come to me for replacements.
I was able to get connected to the machine shop that has been suppling replacement Pocket Wheels for years but they just copied a casting that was brought to them.
The company I'm currently working with has 40 plants, so changing out the chain design is not something they want to do right now.
Best regards, David

 
Out of the box, and I have no idea if it's feasible, however for welding chain links like this, I'd be inclined to see if there exists any flash butt welding installations tailored to chain links.
Manual welding will not give you the quality you require, and most likely a way to big heat affected zone. FBW will very much limit the size of the HAZ, and probably not require PWHT. However, I've seen (and worked with) FBW installations of much larger steel sizes (think train and crane rails), I don't know if those exists for these sizes.
 
kingnero, in house here I wouldn't think twice about welding on the chain.
I have one guy that regularly TIG repairs one of the 60,000 PSI tubes on our waterjet, and at the other end of the spectrum we do weld joints 18" thick that require 2 months to complete, all the time keeping the material at 300F min. and then PWHT at 1,100F.
In the marine world, I'd use a Kenter link for Stud Link chain.
 
"one guy that regularly TIG repairs one of the 60,000 PSI tubes on our waterjet..."

Hmmm, (for once) not trying to be a jerk, but it sounds like the weld repair ain't really a repair.
Such is the case when living with poor designs sometimes. High quality Masterful welds will fail on a badly designed part.
Or also of course if the welding is not real well done due to skill or circumstances.
Pretty welds are not necessarily well done.

My old copy of ASTM A952 "Forged Grade 80 and Grade 100 Steel Lifting Components and Welded Attachment Links" 1says stuff like this -
- "Welding shall not be used to repair forged components."
- "7.6 Heat Treatment—After forging or welding is completed, each load bearing component shall be heat treated before
applying the proof test. Heat treatment shall include quenching and tempering as defined in Definitions E 44."

All the internet chain suppliers I checked so far boldly proclaim their Class 100 chain is quenched and tempered.

If you really need all Class 100 chain's properties, an as-welded link will not suffice.
 
Tmoose, We have to repair the tube because of erosion caused by the flow of the water.
We run the crap out of that machine.
Most companies would have to buy a new tube.
Fortunately we have a Metallurgist on staff, he was out at one of the foundries we use when I made my post.
I wanted to pose my question here to see if someone else has any experience with a situation like this before.
Thanks to everyone.
Best regards, David
 
DAVIDSTECKER, interesting thread. Can you reveal how the manufactured housing industry makes use of this capstan & chain loop arrangement?

Regards,

Mike


The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
I found this video that shows the chain on the floor.
About 3:52 you can see the chain moving and pulling "Pallets" that the modules are assembled on.
I haven't watched the whole video yet but I plan to.
I'm learning as I go too, We are mainly in the Marine industry but we get a lot of inquiries out of Left field.

 
David, thx. I watched about half. Looks like both product and process are well designed.

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
SntMan, As I mentioned earlier, this sort of of found us so I'm still learning about this system and industry.
Some of the things that I assumed were going on, where somewhat confirmed in the video so I learned a little more myself.
 
MintJulep, thank you for the link, It lists the same ratings I've found earlier.
Now that I've seen more of the operation, I totally agree that it's not much of a load if it's one Pallet.
What I don't know is how many pallets would be hooked on at any given time.
I do know that the machine is capable of delivering over 6,000# at full running speed.
The electric motors we use can generate 200-300% torque, making the potential pull 12-18,000#.
I'd rather not produce flying serape metal in the plant if I can help it.
Best regards, David


 
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