Loader arm welding to pin

[Nige]

Here's a few more snippets of information about the 939C in question.

 

[Nige]

I think that the reason for the lever assembly is installed "inside to out" with the flush face on the inside is probably the lack of clearance between the inside face of the lever assembly and the outside face of the hood of the tractor.

 

[Welder Dave]

I was thinking the same and the outside with the removeable plate has more clearance. Recessing the pin a bit just allows for a stronger weld.

 

[Nige]

Would a full 90-deg v-groove (45-deg on both plate and pin) not achieve the same objective.?
Are we agreed that a shrink or press-fit for the pin into the bore in the plate would be the best way to go, whatever design of weld was used.?

 

[Welder Dave]

A V groove on both the pin and plate would add strength but recessing the pin would add more strength in my opinion. A compromise might be to V both and recess the pin about 1/8-3/16". I don't think the pin would need to be a press fit because it's welded anyway. It should be a real close fit to keep the pin aligned though. As long as the hole on the other plate isn't wallowed out and is also a very close fit I think would work fine. The pin may be a tight fit to begin with. The outer plate just adds support and doesn't allow the arms to twist. That's part of why I think it's important to keep the pin greased. I think it's very similar to a cylinder pin and they normally just slide right in. They have bushing but I think take more of the load and have more movement. There wouldn't be a lot of force on the weld unless the pin was dry and seized in the bore. I think I'd put the 2 arms together spaced apart with all the pins aligned before tacking the pin(s) in just to insure everything lines up. I'd put 3 or 4 tacks on the pin. The last thing you'd want is to weld the pin up and it's off a few thou. and the assembly won't go together.

I found a pic. of a Case pin that shows the recess I was talking about. Click on the 2nd pic.

https://www.minnpar.com/product.asp?PartNbr=105752A1&StockNbr=QR6881820&ProductCode=550901

 

[Nige]

I found a pic. of a Case pin that shows the recess I was talking about. Click on the 2nd pic.

https://www.minnpar.com/product.asp?PartNbr=105752A1&StockNbr=QR6881820&ProductCode=550901

I get what you're saying, but IMO there's a difference between the function of the two piins. The type of pin in your photo is being pretty much entriely held against rotation by the weld on the flag (locking plate) with very little in the way of side to side forces being applied to it.

Also the plate to which the pin is being welded is not that thick. If the pin was left shy of the outside by even a 1/4" it would IMO increase the bending moment on the plate significantly.

The pin in that 939C Tilt Link has to be held against both rotational and significant side-to-side forces because of the loose plate #12 on the outdie of the assembly. That's why I suggested an interference fit of both pins into the lever. Also having an interference fit between the pin and the plate will IMO largely stop the pin from moving while it is being welded and help to maintain alignment.
For correct alignment it would be necessary to assemble everything with both the inside (fixed) and outside (loose) plates in position then weld the end of the pins to the plate. At each stage of the welding the outside plate could be checked to ensure that it was still free to move on the pins.

Here's another thought. Are both the inside and outside plates still true (straight in other words)..?

 

[Welder Dave]

Would be good to fit everything together and see how the pins fit. Maybe Cat designed the pin to be slightly recessed? If the pin was recessed a little (not as much as the Case pin) the weld would bring it out to the thickness of the plate anyway. The pin is already chamfered. If the pin is recessed is still a loose fit at the outside of the plate. I think with both arms connected (boxed) the plates are already extra thickness to resist bending. Whether the pin was flush with the edge or recessed with the weld going to the edge I don't think would make any significant difference as far as bending. With no side forces I'd bet 3/8" plates would handle the lifting force.

I tried to find a clear pic. online but can't tell for sure. It looks close to flush but could have a slight recess. I think the upper and lower pins are designed to hold the two arms tight so they can't spread apart. That's why it would be good to make sure the retainer on the loose plate will fit after the pin is welded. Adding a shim/washer is better than having it too short. If it was a 977 might be more critical. The original 931 clamped the pins on the plates on both sides instead of welding the pin on the inside plate. I might go out to my property this weekend and see what my 931B looks like. Interesting discussion. This loader will be better than new once we figure it out.

 

[Theweldor]

I would agree with Welder Dave as far as welding just the outside with 7018. Put a bit of a bevel on both the pin and the plate both on the outside. The hole in the plate should be a nice fit to the pin. I am not sure it needs to be a press fit but it should be snug for alignment purposes and to get all the support possible on the pin.

 

[ilovetracks]

Thanks a ton guys, really appreciate it. It will be a press fit and then weld, the other side is a hair loose so should slide on. The pin is annealed o1

 

[Nige]

Here's a question. Are you doing just one side or both.?
If you're only doing one side then I would suggest to use the Tilt Link on the other side as a pattern to get accurate centre-to-centre measurements for welding. If you don't do that there could be a risk of the linkage trying to twist in operation because one link is slightly different mechanically to the one on the other side.

 

[Welder Dave]

My thought was to assemble them with the outside plate and use some spacers (pipe, tubing, even wood blocks) so they are the same width as when installed on the machine. The cylinder pin could also be used for alignment. You could use a couple clamps to hold the mock up together for welding. The 3 pins should keep it in alignment. The pins being a press fit shouldn't move and having the whole thing clamped together should prevent any twisting. Just make sure to clamp them so they are flat and the same distance apart on all sides. Leave them clamped till the weld(s) cool enough to handle them with bare hands. Should be a fairly simple repair. A good weld is essential for it staying together.

 

[Welder Dave]

I finally went out to my property to pump water. I looked at the bucket arms on my 931B and the pins are clamped on each side. The retainer plates on all the bolt on cylinder pins are recessed some for welding. Not as much as the Case pin I showed but down about 1/8" and the weld just out a little past flush. The recess likely gives more surface area for the weld without having to bevel the plate. I wouldn't be surprised if the pin had a slight bevel as that would be easy when it was made.

 

[ilovetracks]

Thanks for all your thoughts, I really appreciate it. Welds seem decent. Not I have to decide if I want to hear and put in oil or just put them on unhardened

 

[Welder Dave]

I don't think they require hardening. I think if they did they would attached a different way so Cat wouldn't have to harden them after welding into the arm. Being they were a press fit the arm would take a lot of heat away from the pins.

 

[ilovetracks]

Yeah your probably right