A little disappointed with Kubota

[chim]

What might happen if a washer (thin enough to be deformed) were used with a conical-shaped nut? It seems an automotive style nut may make a washer fill in the wallowed-out area.

 

[crazyal]

For clarity let's examin this.

Hub centric means the hole in the center of the wheel fits tightly over a raised shoulder on the axle. Is this how yours is designed?

Yes. I think you can see it in the first picture I posted.

 

[ovrszd]

Yes. I think you can see it in the first picture I posted.

You said in your first post that the center hole in the dish was too large for the axle hub. Is this true or not?

 

[radios1]

You keep saying that the nuts didn't loosen up, and I believe you. But I don't think that the nut loosening or not is the problem here. And it doesn't look like the diameter of the hole is either.

From a mechanical engineering point of view, conical nuts and tight-fitting wheel stud holes are nice, but those features are backups. In this type of joint, It should be the simple clamping pressure from the nut that does the work of keeping the wheel tight enough to the axle face so that it doesn't move.

From what you say, it simply looks like the clamping pressure is insufficient to keep the wheel from moving. And that is such a simple calculation that I can't believe that Kubota got it wrong. Al, when I look at that picture you posted of the stud, lock washer, and nut stack back at the beginning of this thread it just looks wrong to me. I seriously doubt that is a stock setup. Have you checked against an exploded parts diagram? It would be downright weird and unique if any joint like that was originally designed with a lock washer carrying the compressive force between the nut and wheel face.

So to me it seems like the nut and washer stack were assembled wrong when the tractor was new. Maybe by the dealer, or the tire shop, or some other place. At the least there should be a large hard flat washer between the wheel face and the nut.

rScotty

I say a wheel nut, which converts the rotational force to a stretching force because of the beveled wheel nut, is better than relying on nuts being tight enough to stop movement. beveled wheel nuts have been used on cars maybe from the beginning. and even used on funny cars with 2000 HP..

 

[RickB]

I say a wheel nut, which converts the rotational force to a stretching force because of the beveled wheel nut, is better than relying on nuts being tight enough to stop movement. beveled wheel nuts have been used on cars maybe from the beginning. and even used on funny cars with 2000 HP..

There are few instances on tractors where chamfered wheels and wheel hardware are metric. The vast majority of metric dimension off road wheel equipment is hub piloted and use dimensionally common hardware. Too much paint on wheels at the hub mounting surface can be problematic.

 

[Oldoak]

Too much paint on wheels at the hub mounting surface can be problematic.

You may have hit upon the cause of the slippage there. Just guessing. Most all the suggestions here are a work around fix in the aftermath, not the original cause.

It would seam to me if it was a Kubota engineering and design problem, there would be more numerous complaints about the same wheel slippage and hole elongation problem. :confused3:

 

[SPYDERLK]

You may have hit upon the cause of the slippage there. Just guessing. Most all the suggestions here are a work around fix in the aftermath, not the original cause.

It would seam to me if it was a Kubota engineering and design problem, there would be more numerous complaints about the same wheel slippage and hole elongation problem. :confused3:

Note that OP said they were never loose - he checked them at spec periodically. Paint relaxation would have caused looseness. ... Seems to me 160 ft-lb just isnt enough. Those bolts are capable of roughly double that.

 

[RickB]

Note that OP said they were never loose - he checked them at spec periodically. Paint relaxation would have caused looseness. ... Seems to me 160 ft-lb just isnt enough. Those bolts are capable of roughly double that.

Pictorial evidence proves those wheels were loose. If they moved, they were loose. If they were tight, the paint wouldn’t be marred, the wheel wouldn’t be cracked and the holes wouldn’t be elongated. That can’t be changed by repeatedly saying the bolts were never loose.

 

[radios1]

You may have hit upon the cause of the slippage there. Just guessing. Most all the suggestions here are a work around fix in the aftermath, not the original cause.

It would seam to me if it was a Kubota engineering and design problem, there would be more numerous complaints about the same wheel slippage and hole elongation problem. :confused3:

the engineering and design problem was the original cause. maybe Kubota, at least on his model tractor, went out of normal design using this setup, and now, the mistake is showing up.. how many other tractor manufacturers are relying on flat nuts to give enough friction to prevent slippage?. I think the rest use tapered nuts like used on cars and trucks!..

 

[Oldoak]

Note that OP said they were never loose - he checked them at spec periodically. Paint relaxation would have caused looseness. ... Seems to me 160 ft-lb just isnt enough. Those bolts are capable of roughly double that.

Apparently you missed this sentence in crazyal's original post:

I made the mistake of going a little past the torque for the bolts and broke one of the studs (which is why I'm posting this).

That being said, those studs certainly could not tolerate anything even close to double 160 ft-lb or 320 ft-lbs.