Pin wear from period loading needs a permanent solution 1

[Imposter666]

There is a maintenance inspection at this pin once a month. it is usually changed out right away as failure would be catastrophic for the production. I have summarized all the details in the picture below. Increasing pin diameter would definitely help as the contact area would increase. However, I don't think this would solve the problem completely on its own. I didn't want to make radical changes to the design. But I am willing to if it will get rid of the problem completely. What countermeasures do you think can be done here.

 

[EdStainless]

You need a ring or collar on the bolt for the chain to bear on so that you don't have line contact.
It will be a two-piece part that has an groove in the OD to fit the chain link (like a saddle).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Compositepro]

There should be a sleeve/bushing between the pin an the chain link. The busing OD should be close the the chain link ID. The problem with the current design is that you have point contact between the pin and chain link with almost zero contact area. This results in very high bearing stress between two surfaces that are in sliding contact. With a sleeve, the sliding will occur between the pin and sleeve (large contact area that should be greased), and not between the pin and chain link.

 

[Imposter666]

Yeah, I understand the importance of increasing contact surface area, therefore my first solution was to upgrade the pin to a new one with 12mm diameter which is very close to ID of the chain. I thought about integrating a collar to the chain, but I don't know how. Are you suggesting to weld a collar inside the chain?

 

[goutam_freelance]

Bushing is a good idea. But It appears that there is some angular sliding at the contact. So it will help to apply grease periodically at bolt surface. Also hardening of bushing will help if chain link surface is harder.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[Imposter666]

I guess I need to upgrade the chain with one that has larger width in this case. Currently there is only 2mm gap between the pin and the chain. I get the sleeve idea, but how do I integrate that to my design? Also if I just put a sleeve over the pin and let the chain contact the sleeve, sleeve will experience a line contact loading in best case scenario, right? I don't know if sleeves are designed for that.

 

[hydtools]

Is there similar wear on the bolt linking the chain to the clevis at the other end of the chain?

Ted

 

[Imposter666]

Yes, they are same pins with different lengths. They experience the same loading conditions.

 

[rb1957]

what is the load between cycles ? What is the minimum load of the cycle ? If zero, is it possible to make it a small number, 100N ? The idea is to stop any impact /shock load.
If not, could you arrange a load fixture so that the chain is always in contact with the pin, and slack chain is moved away from the pin (to above the fixture) ?

is it possible to improve the load transfer into the chain ? Instead of a simple link could you have a lug and a neat fit to the bolt ?

could you make a sacrificial bushing (bronze ?) so that it'll "happily" deform without hazarding your loadpath (the pin) ?



another day in paradise, or is paradise one day closer ?

 

[Imposter666]

I am inclined to suggest to increase the bore diameters at both ends of clevis to 12mm tight fit and put in a clevis pin with 12mm. At least, I will increase the contact area from point loading to line loading. Also by making it tight fit, I want to make sure that the pin doesn't spin in the clevis. This way, I think, pin would have certain wear and get the shape of the chain. After certain point, wear would stop as little plastic deformation will increase the contact area between the chain and the pin. What do you think, folks?

 

[BrianE22]

Looks like Misumi offers the pins with a hard chrome plate. I'd give that a try.

 

[Imposter666]

They have actually tried that one, but it didn't show any improvement over the pin I listed up here. The plating is very thin and once it is pierced through it is basically same pin as this one here.

 

[rb1957]

I don't think you want a tight fit pin ... if you plan to remove it every month.

I think improving the loadpath between the pin and the link will help ... replace the last link with a "proper" lug and a clearance fit hole for the pin.
Adding a bushing around the pin will protect the pin from damage.

I think removing slack from the chain will help.


another day in paradise, or is paradise one day closer ?

 

[Imposter666]

I hope not to change the pin ever again. Do you know any off-the-shelf lug that would work for me? I thought of designing a lug, but how do you put in the chain link later on?

 

[SwinnyGG]

If it were me, I'd buy some of this:

https://www.mcmaster.com/tubing/id~10mm/od~12mm/material~steel/

And make bushings out of it. Eventually this material will yield and conform to the shape of the chain, and provide some load distribution on the surface of the pin.

Your alternative is to machine a custom part to terminate the chain into the pin connection.. which is probably better, but will cost a lot more than $7.

Alternatively- you could try and source a square-link chain equivalent in strength to what you're currently using. This would change the current point contact between the chain and pin to line contact. That's probably a cheap solution to try as well, as long as the chain isn't extremely long.

https://www.mcmaster.com/5478T4/

 

[TugboatEng]

The chain is seeing the same forces as the pin. Has wear on the chain been a problem? The chain and pin should wear out at the same rate.

Also, the pin in your picture does not match the part number. Do veryify the correct pin is being used. Your part number lists a reasonably hard pin but with black oxide costing. Your pin has a different coating.

 

[MacGyverS2000]

I don't think you can "never" replace it again... as long as two items are moving in relation to each other (i.e., rubbing), something is going to wear down (perhaps both!). Right now, the pin is the sacrificial/softer element...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[dhengr]

Imposter666:
You really ought to communicate with your coworker “Hungy_kid.” This same question has been asked and answered at Structural thread (thread507-477921), he didn’t bother to come back after several people had spent (wasted) their time answering his question, and try to help him. He didn’t bother to provide the engineering and dimensional info. we asked for, to further the discussion. Your thinking of a line loading is a slight improvement, but it won’t last either. The parts kinda have to be matched in material strength and hardness. I would look for some special end links which some sort of well shaped/designed pin bushing and link bearing piece can be fitted into.

 

[Compositepro]

Hint: consider the loading between every link in that chain, where you are not having a problem.

 

[CWB1]

I would scrap that clap-trap and either loop the chain over a small diameter chain wheel back onto itself or clamp it in a two-piece chain block. I can’t find an image of a chain block, but am attaching a nifty view of a chain wheel in case you’re unfamiliar. Chain blocks have similar geometry supporting the chain, but completely surrounding the chain and split/clamp/bolt down the middle.