Well i broke it this time

[johara1]

turn the pin to fit the tube....Jim

 

[ponytug]

I have imagined that the fiddly bit to the repair is welding the outer tube so that the interior of the outer tube is smooth and allows the inner pin to move freely with no high spots. Monster drill?

All the best,

Peter

 

[MossRoad]

I have imagined that the fiddly bit to the repair is welding the outer tube so that the interior of the outer tube is smooth and allows the inner pin to move freely with no high spots. Monster drill?

All the best,

Peter

Yeah. My guess is if you clean it up and make a tight fit to the rollover arms, and maybe not bevel the end of the tube too much, it’s not going to burn through and grab the pin. Of course, that depends on how thick the tube is, how big the hole in the rollover arms is, how much heat you weld with, etc. as you know.

I have a reamer somewhere that fits the inside diameter of the caster wheel tubes. I think it’s 1” or slightly larger. They were throwing things out at my old employer and I acquired it many years ago. It’s about a foot long and would reach the center of that tube from either end.

From what I’ve been reading, one of the main problems with these simple bearings is that the wearable material is not replaceable like ball/needle bearings or bushings. And a welded in pin doesn’t help much either. I wonder if they pinned the pin instead of welding it would work? There’s not much rotational force on that pin. It’s just sitting there for the rollover arm tube to roll on. I wonder what the forces the tube puts on the pin are?

Anyhow, it’s a low speed movement. Even if there was a high spot in there pressing against the tube, it’s probably not going to gouge the pin to the point of breaking, and once a path is worn into it, it won’t get any deeper.

That’s my sloppy engineering opinion.

I’d like to hear others’ opinions on it.

 

[ponytug]

Yeah. My guess is if you clean it up and make a tight fit to the rollover arms, and maybe not bevel the end of the tube too much, it’s not going to burn through and grab the pin. Of course, that depends on how thick the tube is, how big the hole in the rollover arms is, how much heat you weld with, etc. as you know.

I have a reamer somewhere that fits the inside diameter of the caster wheel tubes. I think it’s 1” or slightly larger. They were throwing things out at my old employer and I acquired it many years ago. It’s about a foot long and would reach the center of that tube from either end.

From what I’ve been reading, one of the main problems with these simple bearings is that the wearable material is not replaceable like ball/needle bearings or bushings. And a welded in pin doesn’t help much either. I wonder if they pinned the pin instead of welding it would work? There’s not much rotational force on that pin. It’s just sitting there for the rollover arm tube to roll on. I wonder what the forces the tube puts on the pin are?

Anyhow, it’s a low speed movement. Even if there was a high spot in there pressing against the tube, it’s probably not going to gouge the pin to the point of breaking, and once a path is worn into it, it won’t get any deeper.

That’s my sloppy engineering opinion.

I’d like to hear others’ opinions on it.

I was taught that the rule was "drill, bore, ream" in terms of dimensional accuracy. Reamers are so high precision, that I wouldn't want to chance one without drilling and boring it to size. Given the low precision of the bearing, I would stop after drilling.

If you leave a high spot inside the pivot, and it cause wear on the pin, the down sides that I see is that it will a) generate metal shavings that create further wear, and b) the high point will wear a Brooke in the pin, setting it up for fracture/failure.

I am fascinated with the trade offs that PT makes on their engineering. In larger machines, these roll surfaces are generally replaceable pins, but much shorter. The PT solution gives you a broad loader arm with three welded cross braces, for a very rigid frame, at the expense of this particular failure which involves gouging out the end welds, repairing or replacing the pin and pivot and resending the ends. (if you are curious about what can be done with air arc gouging, there is a nice video at

, and

)

So, to answer your question @MossRoad, I think that the PT solution gives you added strength and rigidity compared to pinning it. One could certainly add brackets on the other tubes to add back strength, but that would probably be at the cost of visibility.

The one thing that I do wish for is a gasket around the ends of pivot to retain the grease and recirculate it between the pin and the pivot. (No, I don't have any bright ideas on how to do that.)

All the best,

Peter

 

[MossRoad]

…

So, to answer your question @MossRoad, I think that the PT solution gives you added strength and rigidity compared to pinning it. One could certainly add brackets on the other tubes to add back strength, but that would probably be at the cost of visibility.

The one thing that I do wish for is a gasket around the ends of pivot to retain the grease and recirculate it between the pin and the pivot. (No, I don't have any bright ideas on how to do that.)

All the best,

Peter

Yes, I hadn’t thought about the fact that since the pin is welded on both ends it adds rigidity to the center of the FEL assembly. Pins would allow some slop. But a round bushing on the outside of the FEL arms drilled for a roll pin or bolt/nut pin would make it rigid. Or a ring and a taper lock on the rollover pin.

But yes, that would require more complex engineering, when ‘good enough’ works pretty well.

And yes, a gasket would be nice, or maybe a boot of some sort. But, just pump in the grease every 8 hours and you’re good to go.

 

[johara1]

First off it is a stupid set up, the highest force is in the middle and it is supported on the outside edge. The pivot arm would need bored out and replace the other tube with a heaver walled one hand weld it on to the pivot arm turn a shaft to fit but first drill and tap for a zerk fitting in the middle. Now insert the shaft though till it is protruding from both outside edges of both arms. Now weld both sides.... Jim

 

[ponytug]

First off it is a stupid set up, the highest force is in the middle and it is supported on the outside edge. The pivot arm would need bored out and replace the other tube with a heaver walled one hand weld it on to the pivot arm turn a shaft to fit but first drill and tap for a zerk fitting in the middle. Now insert the shaft though till it is protruding from both outside edges of both arms. Now weld both sides.... Jim

+1 on adding the zerk in the middle! I also agree that upgrading to thicker wall tubing or solid high strength rod ought to be considered.

All the best,

Peter

 

[MossRoad]

Has anyone asked PT if the new arms are beefier?

 

[johara1]

I guess I think on trying to improve it. Plus from my point of view is coming from me having a Lathe, milling machine and meg welder..... Jim

 

[Tchamp]

Well what i am doing is i removed the old pin and removed the center pivoting arm assy. The pin in my assembly is 1.234 thick. I purchased 2 foot of 1.5 in roll stock used to make rolling pins on heavy equipment from my local metal fab. Shop. Brought it and the pivot assy to a machine shop, they are going to turn the pin down to fit the pivot assy and then they will install roll pin into pivot assy to align the broken side, align back to original position and weld back together. The roll pin stock was $35.00 the machining and welding $100. Which entails machining the pin, welding pivot arm and welding pin back in place on machine, i think it is very reasonable. I could buy pivot assy. from PT for 165.00 Plus shipping, so it would be around 200 ish im guessing, so i think i am coming out ahead going this route. Plus i am doing good for the environment, im recycling lol.