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Pin wear from period loading needs a permanent solution

Pin wear from period loading needs a permanent solution

Pin wear from period loading needs a permanent solution

(OP)
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.

RE: Pin wear from period loading needs a permanent solution

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

RE: Pin wear from period loading needs a permanent solution

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.

RE: Pin wear from period loading needs a permanent solution

(OP)
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?

RE: Pin wear from period loading needs a permanent solution

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/

RE: Pin wear from period loading needs a permanent solution

(OP)
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.

RE: Pin wear from period loading needs a permanent solution

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

Ted

RE: Pin wear from period loading needs a permanent solution

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

RE: Pin wear from period loading needs a permanent solution

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 ?

RE: Pin wear from period loading needs a permanent solution

(OP)
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?

RE: Pin wear from period loading needs a permanent solution

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

RE: Pin wear from period loading needs a permanent solution

(OP)
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.

RE: Pin wear from period loading needs a permanent solution

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 ?

RE: Pin wear from period loading needs a permanent solution

(OP)
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?

RE: Pin wear from period loading needs a permanent solution

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

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

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/

RE: Pin wear from period loading needs a permanent solution

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.

RE: Pin wear from period loading needs a permanent solution

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

RE: Pin wear from period loading needs a permanent solution

Imposter666:
You really ought to communicate with your coworker “Hungy_kid.” This same question has been asked and answered at Structural thread (thread507-477921: The pin anchoring down the chain sees a lot of wear. What design change can be done to prevent wear?), 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.

RE: Pin wear from period loading needs a permanent solution

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

RE: Pin wear from period loading needs a permanent solution

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.

RE: Pin wear from period loading needs a permanent solution

I don't mean to repeat myself but everybody is ignoring the elephant in the room. Every single link in the chain is subject to the same wear. Chain is a terrible choice for this type of high cycle loading. I don't know why chain is required here but there is a reason fittings aren't available off the shelf to handle this type of cycling. Wire rope, on the other hand, has many options for fittings to fit on a pin.

I suspect OP is having a short life because they're not using the same pin that is listed in their spec. If the chain isn't wearing, a pin of similar material should last as long as the chain. With that said, chains used for lifting REQUIRE regular length measurements to determine wear so whatever you do to fix the pin isn't going to fix the rest of the system.

If you must use chain, I suggest using a roller chain as the bushings are built in.

RE: Pin wear from period loading needs a permanent solution

Inposter666,

I would condider changing the design completely unless there is a need for intermediate machined plate with pins.

Instead I would replace the inner machined plate with shackle with pin for connection to upper linkage and bow side to chain using a bit large safety factor. But on the shackle pin side connection you need to keep the Herzian stresses less than 1.8 x yield strength (even I would use lover than that, perhaps 1.2 x yield strength or just yield strength) since the pin is under small rotations.

RE: Pin wear from period loading needs a permanent solution

Quote (Immposter666)


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.

The plating they use is very thin. I would try .005" of hard chrome (assuming that will fit in your holes).

The replies seem to be split between using a softer material and letting it wear in and conform or using a harder material. As someone pointed out, the chain links themselves aren't wearing (or are they?). Does anyone know what they are made of? I don't think they have plating - just a strong, heat treated (for strength and hardness) steel I'd guess. I believe the contact pattern for the links would be a point which should have quite a bit for contact stress.

RE: Pin wear from period loading needs a permanent solution

It appears that sliding at the contact surface is creating wear problem.If budget permits you can design a special attachment connected to end chain link which will have a ball or roller bearing fixed by pin and bushings etc. This will prevent wear due to sliding.

Engineers, think what we have done to the environment !https://www.linkedin.com/in/goutam-das-59743b30/

RE: Pin wear from period loading needs a permanent solution

"I believe the contact pattern for the links would be a point which should have quite a bit for contact stress."

In high strength lifting chains the ID of the links is very close to the diameter of the steel rod that the links are made from. With deflection under load there will be two lines of contact between each link rather than a point contact.

RE: Pin wear from period loading needs a permanent solution

One of the memorable posts I've read on ET had to do with a cotton thread manufacturing engineer that was having issues with stainless steel guides getting cut by cotton thread. So, doesn't much matter what the relative difference in hardness is, enough abrasion will allow the softest materials to cut much harder materials, much like the water cutting river beds through granite canyons.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Pin wear from period loading needs a permanent solution

(OP)
dhengr, it was my account. I new to this platform, didn't know where I am supposed to receive the notifications at. Anyways, I decided to create a new account with my personal email and provide what was asked of me under this new thread.

RE: Pin wear from period loading needs a permanent solution

(OP)
Guys, the design was done much before my time in the plant. I am trying to come up with something cheap that will solve the problem permanently at best or will require maybe yearly inspections at the pin instead of yearly inspections. Anyways, I looked at case I suggested: simply upgrading the pin to 12mm of same kind from Misumi. For my analysis, I choose a contact width of 1mm for both current and new model.




RE: Pin wear from period loading needs a permanent solution

(OP)
goutam_freelance:
Thanks for pointing out the sliding wear. The old pin used to be able to spin in the clevis freely. It also made minimal contact with chain. I am going to suggest to machine the bore diameter of the clevis to something tighter. So I am hoping that chain would only pull from one side of the pin. I am thinking that there will be certain plastic deformation as the chain makes a very little groove for itself. But it will stop at one point.

RE: Pin wear from period loading needs a permanent solution

a bigger pin will definitely help. whether it fixes the problem is open for debate ... wear is a difficult thing to solve with FEA.

It'd also help to have something to distribute the load over the pin ... like a machined piece that fits inside the chain link and makes a neat fit on the pin.

Is there no option for the chain ?

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

RE: Pin wear from period loading needs a permanent solution

I think the usual approach must be for the chain maker welding a fitting onto the chain prior to heat treatment. However the wear between the links is still going to happen so simply meeting the same diameter and material should match the rest of the chain.

I spent a bit of time looking and I expected catalogs from chain makers would have some, but the most frequent was just a shackle with a straight pin or a split part that captures the outer shoulder of a link.

RE: Pin wear from period loading needs a permanent solution

(OP)
rb1957 and 3DDave:
As I mentioned, I will make the bore diameters with little tighter fit so the pin doesn't spin. I actually want the pin to deform a bit and increase its contact area. Also the pin and the chains are purchased parts. We usually refrain from modifying purchased parts. I could design something, but I am trying to get away with a simpler and cheaper option. Our maintenance crew is inspecting this pin monthly. If I could reduce the inspection cycle to let's say yearly, it would be a big improvement.

RE: Pin wear from period loading needs a permanent solution

cheap solutions generally yield the minimum results. if you're happy with that then "fill y'r boots".

I don't know how you'll inspect a tight fitting (possibly deformed, and I understand what you mean ... interference fit) bolt.

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

RE: Pin wear from period loading needs a permanent solution

There's also a factor which just occured to me which didn't before...

If you get enough deformation in the pin contact area, the displaced material may make it very difficult/impossible to remove the pin. Might want to think about that.

RE: Pin wear from period loading needs a permanent solution

Look into https://www.stulzsicklessteel.com/creusabro/creusa...
Better known as Hadfield Manganese or AR plate.
It is machinable as long as you do right, it work hardens but I believe you can anneal it if you need.
It gets harder than probably anything you've ever dealt with but it is also tough.
Used for rail road switch gear, crushers and mills.

RE: Pin wear from period loading needs a permanent solution

Imposter - rather than you modifying it, it's having the chain maker who has the facility to both make the modification and proof-load the finished product.

RE: Pin wear from period loading needs a permanent solution

Are you always using the same chain and the same pin, or is it a set of different chains?

It seems to me that the pin in the photo has the profile that you probably want in your pin to begin with

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Pin wear from period loading needs a permanent solution

That's why I find this post odd. This arrangement is very standard for lifting equipment. OP's pin does not match the part number provided so I believe the wrong pin is being used and that is the source of the problem.

RE: Pin wear from period loading needs a permanent solution

Frequent inspection is necessary,
If this is part of a hoist sling,

29CFR1910.184(d) (OSHA General Industry) Slings - Inspections.
Each day before being used, the sling and all fastenings and attachments shall be inspected for damage or defects by a competent person designated by the employer. Additional inspections shall be performed during sling use, where service conditions warrant. Damaged or defective slings shall be immediately removed from service.

You can reduce - but not eliminate the wear by using case hardened alloy chains and fittings.
Lubrication will help, but needs to be applied daily, and does can be counterproductive if conditions are dusty. (Dust + Grease = lapping compound).
This recommendation is based on experience with scrap handling electromagnets.

Fred

RE: Pin wear from period loading needs a permanent solution

if the pins are centers less ground then thick engineering plate be applied then regrind. soft internal parent material, with hard chrome will last many cycles.
minimum thickness of plate needs to be .005 inch minimum. chrome is harder than carburized surface and is use for shaft bearing diameters as a repair,

RE: Pin wear from period loading needs a permanent solution

If you go to the Misumi catalog page OP "claims" the pin is from, there is a hard chrome option available so this should be an easy solution. However, OP "claims" to be using a certain pin part number but the part number indicates black oxide coating and OP's pin clearly is not black oxide coated. Because of this, we have no idea what pin OP is using. Before making any changes to the design, we first need to verify the properties of the pin.

RE: Pin wear from period loading needs a permanent solution

(OP)
TugboatEng:
Our maintenance group has tried both pins. They both failed in the similar fashion.

RE: Pin wear from period loading needs a permanent solution

A lot of good suggestions, especially about a sleeve in last chain link.
Does the chain go completely slack during the load cycle? If yes, then position changes between pin and chain link might be changed (several ways) to reduce friction.

If the load is applied or released quickly during the 850 cycles/day, then the dynamic load may be much higher than the design static load. Consider reducing loading rate or damping dynamic load.

Walt

RE: Pin wear from period loading needs a permanent solution

(OP)
Yeah, the thing is these are off the shelf purchased parts that are stored as spares by our maintenance group. I don't want to modify a purchased part.

RE: Pin wear from period loading needs a permanent solution

(OP)
DAVIDSTECKER:
I appreciate you taking your time to sketch that!

RE: Pin wear from period loading needs a permanent solution

Quote (Yeah, the thing is these are off the shelf purchased parts that are stored as spares by our maintenance group. I don't want to modify a purchased part.)


If you can't make anything to solve your problem, you need to buy your way out... and there's severable viable solutions on that path above.

RE: Pin wear from period loading needs a permanent solution

Imposter666,
Your welcome, I hope it leads to a solution for you.
Peerless Chain has a group for custom fittings incase you need an outside source.
Best regards, David

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