A little disappointed with Kubota

[Coyote machine]

So it seems, from the last number of posts, what I posed earlier might in fact be the answer to why the hole elongation occurred, and why this tractor belonging to the OP has this not unique issue. Reiterating what I posed earlier. Whoever installed the wheel/time combo on this single Kubota tractor might not have tightened the wheel to the axle(s) correctly, or tight enough, or followed standard practice of tightening in a sequence rather than one then next in a circle, etc.
And, followed, possibly by no re-torque soon enough after sale to correct and properly secure the wheels to the axle hubs, could have resulted in the end result being established with loose nuts or studs and thus elongation.
Kubota's design of captive lock, no flat may work IF applied as intended, and proper and timely re-torquing following as required for 99% of these tractors, but add human error and some are bound to end up as the OP's has. No blame intended here, merely a plausible explanation as to how this tractor ended up with this problem.

 

[RickB]

You would expect those elongated holes to just cause the wheel to slip again?

Absolutely.

 

[Oldoak]

After 156 posts no one is yet quite sure what the problem was (and no one knows whether it will return.)

You got it! :thumbsup:

All speculation and opinions. Pictures don't quite hack it and can be deceiving. The O.P. is the only person closest to the facts.

 

[aczlan]

So it seems, from the last number of posts, what I posed earlier might in fact be the answer to why the hole elongation occurred, and why this tractor belonging to the OP has this not unique issue. Reiterating what I posed earlier. Whoever installed the wheel/time combo on this single Kubota tractor might not have tightened the wheel to the axle(s) correctly, or tight enough, or followed standard practice of tightening in a sequence rather than one then next in a circle, etc.
And, followed, possibly by no re-torque soon enough after sale to correct and properly secure the wheels to the axle hubs, could have resulted in the end result being established with loose nuts or studs and thus elongation.
Kubota's design of captive lock, no flat may work IF applied as intended, and proper and timely re-torquing following as required for 99% of these tractors, but add human error and some are bound to end up as the OP's has. No blame intended here, merely a plausible explanation as to how this tractor ended up with this problem.

If you have a flat washer and a bolt/nut, they will do the same thing if they are not properly tightened and re-tightened.
The lockwasher and bolt/nut system on the rear wheels of our L3830 and B7500 have been fine for 10+ years and over 1700 hours between the two tractors.
L3830 with ~660 hours:

B7500 with ~1100 hours:

Both have been off, both were reinstalled with a impact wrench, neither has moved at all.

Aaron Z

 

[LD1]

I don't understand why this keeps being labeled as a Kubota problem. Lots of other tractor brands do it the same way. These wheel/tire combos come from Titan, and many brands use them. I'm not trying to defend Kubota here, but seems like this is more of a generic issue and I don't think orange paint has anything to do with it, pro or con.

I dont know why people keep insisting that the dealer or assembler messed up. Or thinking that the OP changed the washers to lock washers:mur:

 

[rScotty]

I dont know why people keep insisting that the dealer or assembler messed up. Or thinking that the OP changed the washers to lock washers:mur:

I don't see the problem here. It doesn't matter who did what, and nobody said that lock washers are a guaranteed screw up. It's just there are always better ways to do most anything, and hardened flatwashers allow nuts to put more clamping pressre to the joint and to maintain that clamping pressure more reliably than lock washers. Everyone knows that; there's no debate there. It's also true that flat washers cost a lot more than lock washers. So if lockwashers are installed exactly right and nothing ever changes then they could do the job and they cost a lot less than hardened and ground flat washers. So what??

Are flat washers preferable? Well....that's one of those strength vs dollars debates and everyone has a different idea of where you draw the line there. Most of us would insist on using hardened flat washers for holding a high pressure boiler together, but we wouldn't want to be using those expensive type of fittings for bolting trim panels to a door. Wheels are somewhere in between.
For myself, I think that the wheel to hub joint is where I want the manufacturer to insist on spending money for the best hardware - no matter who ends up putting the wheels on the tractor. But that's just my opinion, some manufacturers will agree and others are going to come to a different decision on cost vs benefit. There's still no problem, any owner who wants to upgrade can simply change it for themselves.

All the technical guys agree that for maintaining a constant clampling force. Again, there isn't any debate. This ain't rocket science.
Hardened flat washers used where the importance of clamping force outweighs cost, and soft flat washers used other places - often with a lock washer.
rScotty

 

[LD1]

rScotty....the problem is that SEVERAL times in this thread, SEVERAL people have tried to say that either kubota, the dealer, or the assembler messed up and used the WRONG parts. So ONE LAST TIME.....KUBOTA USES LOCK WASHERS.

You can continue to debate the lock washer vs flat.....and whats better. Im not touching that argument with a 10ft pole. Nor do I care to speculate what caused this issue.

But to continue to proclaim that someone used the wrong hardware.....beyond asinine And to jump to the assumption that engineering or design issue is the cause....based on ONE issue from ONE manufacture....when there are literally several manufactures and millions of tractors that have this SAME SETUP.

This sounds like a dealer problem. If you bought this new then someone didnt bother to torque the wheel nuts when they assembled your machine at the dealership.

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.

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

Scotty I agree. Certainly raises the question (if this was bought 'new') then why was someone dorking with the wheels? No idea how long ago the purchase was but I'd sure put some pressure on the dealer to explain this one.

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.

that design looks flawed bolts are too close to hub to get large thick flat washers under. New hubs will have same problem, only solution is making you own washers, to increase the clamping area.

as has been stated a couple of times, the lug nuts are supposed to be conical, like car and truck nuts, somebody rigged this for failure, maybe they were just too lazy to get the proper nuts, and used flat nuts, thinking it'll work.. who knows what the original owner was thinking before the OP bought this..

But there is absolutely no doubt that split washers are never used where bolt clamping pressure is critical. Since a split washer can expand radially when compressed or anytime that the load changes, there is no way that an engineer can count on using bolt torque to design an appropriate clamping force. That is why hardened flat washers are used.

If you put a lock washer into the stack, you cannot rely on bolt torque to give you clamping pressure or bolt stress because the split washer can expand radially. That's why lock washers are not used where clamping pressure has to be accurate. And if bolt torque isn't a reliable and repeatable measure of clamping then where are you??

There is something amiss with the way that Al's Kubota's wheels are clamped to the axle hub. I don't know what it is and have no idea how it got that way. In my opinion, I think he needs to contact a Kubota technical rep for his area and let them tell him what is wrong.

But any and every engineer is going to tell you that the way it is shown in the original photo is not the normal way to use bolt clamping forces.

My suspicion is that it is either a mistake or not stock.
rScotty

That's the trouble with engineering mistakes. They don't always fail, but they do tend to perpetuate themselves.
Al's bolts failed; others didn't... or haven't.
rScotty

What's been said several times ... ~ "there never should have been lock-washers on wheels." Those are better suited to clamping soft materials (wood, etc), or when application torque is well shy of a bolt's maximum capacity and no side-loading is to be expected.

Doesn't this go back to what the dealer or distributor did wrong, by assembling with lock vs flat washers? btw, I might go as high as 220 ft/lb when tightening these, but I'd be quite surprised to find that 160 ft/lb wouldn't do with proper parts installed.

I'd do the post-install re-torque (re-check) on these more than once, esp if holes might be burred-up much. :2cents:.

1) someone other than the factory mounted the wheels on the tractor. Whoever that was MIGHT have been better advised to use large flat washers.

 

[boomer1025]

Al get a 3/4" reamer, not a drill bit. Leave the 2 studs torqued tight to hold the wheel in place on the disk. Remove the 4 bolts and ream the holes out. Install 4 flange head fine thread grade 8 bolts and flange lock nuts. You should be able to pick these up at any International truck dealer, Fastenal store, local hardware store or a truck stop service center or buy them online. Make sure you torque them to specs and recheck them several times after several hours.

 

[s219]

rScotty....the problem is that SEVERAL times in this thread, SEVERAL people have tried to say that either kubota, the dealer, or the assembler messed up and used the WRONG parts. So ONE LAST TIME.....KUBOTA USES LOCK WASHERS.

You can continue to debate the lock washer vs flat.....and whats better. Im not touching that argument with a 10ft pole. Nor do I care to speculate what caused this issue.

But to continue to proclaim that someone used the wrong hardware.....beyond asinine And to jump to the assumption that engineering or design issue is the cause....based on ONE issue from ONE manufacture....when there are literally several manufactures and millions of tractors that have this SAME SETUP.

YES YES YES, I wish folks would realize this.

 

[TheMadOne]

YES YES YES, I wish folks would realize this.

First rule of design. Even if 80 million perfectly functional examples of the design exists, people will armchair that the one problem child is because of an inherent design flaw. Every time.

Every.

Flipping.

Time!