Tractor broke in half again

[MossRoad]

Does a ball go inside that grooved tube?

 

[NoTrespassing]

Carl-

I'm no engineer, but it seemed to me that your old one broke right at the end of the weld. That could be caused by a lack of strength, brittleness from welding, or random. I'm betting it is one of the first two. Adding metal, and then a little post welding heat treatment should help.

Given where it broke last time, I would be tempted to get some E10018 welding rod and build up the perimeter starting at the triangular base, crossing the existing weld and going at least half way around the perimeter of the inset/attached tube. I would work up a couple of passes until you have added another 1/4" of material along the outside of the piece and over the existing welds, which will be (I'm guessing) probably be 3-4 passes. I would also try to add more material at the join to build up the web. (If you think of the perimeter of the part as a keyhole, I would be trying to make the keyhole into more of a triangle by adding material at the sides of the circle/triangle intersection.)

All the best,

Peter

What do you supposed the tolerance is on the bore diameter? Would doing that much welding on it cause a problem?

Kevin

 

[KWentling]

What do you supposed the tolerance is on the bore diameter? Would doing that much welding on it cause a problem?

Kevin

Welding on the tube is going to distort it and shrink it. The ball is called a "spherical plain bearing". It's a ball in an outer housing. It needs to be installed with not much more than a metal to metal fit or it will lock up and not swivel. Those bearings are available in all kinds of sizes, both inch and metric. Any bearing store can get them. If your going to use the new weldment, take a flapper wheel on right angle grinder and blend grind the weld where it ends on the tube. That will minimize the stress riser at that point. If there is room, a new weldment with the plate surrounding the tube would be a major improvement.

I've had a lot of experience with that type of bearing set up repairing heavy equipment. It's used a lot.

 

[CADplans]

I would be tempted to purchase those parts unwelded,
then, take them to a CAT service center, and have them weld the part.

Look at any big CAT machine, you will find a similar part welded.
CAT will run the weld two inches beyond the end of the spot where the parts touch.
They also use other techniques that insure there is no stress riser at the end of the weld.

In looking for an example of the right way,, I only found an example of the WRONG way,,,
right where the weld of the thumb that was added to the boom ended,, the backhoe boom broke.

The weld in the pic is an enormous stress riser.

The purchased assembly has an extreme stress riser right at where the weld ends.

Other than welding the original parts correctly,,,
beefing up that new assembly would depend on how much clearance there is to add more steel,,,

 

[prs]

I am no engineer, but I am good at destroying parts. In the early posts to this thread it is reported that the manufacturer was not willing to endorse beefing-up of this joint. Could it be that they are concerened that doing so will transfer the damage to other parts and that such other parts are not as readily sacrificed; that is harder to repair, or more costly to repair?

Also, would it be possible to add some structure to the frame halves to stop the articulation just before the limit of over stress? Suspension bumpers?

prs

 

[KWentling]

Also, would it be possible to add some structure to the frame halves to stop the articulation just before the limit of over stress? Suspension bumpers?

prs

That's an excellent idea. That would take the twisting load off that that weldment.

 

[Marks481]

In the early posts to this thread it is reported that the manufacturer was not willing to endorse beefing-up of this joint. Could it be that they are concerened that doing so will transfer the damage to other parts...

I don't think Power-Trac does any finite element stress modelling of their equipment. Their approach is to make everything out of thick plate steel, regardless of how much load it supports. These machines (in most places) are over-built.

Except the doggone drainage hole in the PT422 floorplate right next to the steering linkage.... and apparently Carl's entire tractor (since I think he has broken most of it at one time or another).

 

[prs]

I don't think Power-Trac does any finite element stress modelling of their equipment. Their approach is to make everything out of thick plate steel, regardless of how much load it supports. These machines (in most places) are over-built.

Except the doggone drainage hole in the PT422 floorplate right next to the steering linkage.... and apparently Carl's entire tractor (since I think he has broken most of it at one time or another).

Ya mean t' suggest he has a couple of broken anvils in his scrap pile?

prs

 

[woodlandfarms]

They do worry about overstressing the machine, but in my case they, in a way, offered a different linkage, but it would require me completely redoing all the steering and would require some thought process in the engineering.

My tractor does not break due to hydraulic stress or over rotation in turning. It breaks because of left to rigth stress. The tractor has two parts, the front and back, and with the wide tire base you can get up on 3 wheels pretty easy, wich then puts some torque on the center section.

I have a game plan, going to pursue it tomorrow. My hope is that I will have all the parts together by Wednesday and can drop it by my neighbor who is going to put it back together.

 

[woodlandfarms]

As for breakimg my PT. Lets see. When the center section broke the first time it took out a lot of the front section. but that has been all welded up. There was a bad weld in one of the steering arms and that ripped out a few years ago. Somewhat like a 422 failure but it was factor weld related. And finally there was a bad well on my oil tank. That I patchec myself. And I did not catch the tractor on fire....

Its a machine, it gets used, it was not in mint condition when I got it but Ken whom I bought it from did a fantastic job getting it in shape to begin with.