A little disappointed with Kubota

[aczlan]

Yep, that's what I am familiar with. Though I thought 2 of the studs were bolts going inward.

That is how our L3830 is setup.

You are right in that illustration is bizarre. Maybe it is because that illustration is an artist's concept. So the drawing itself might be correct or maybe not.
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.
<snip>
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.
<snip>
My suspicion is that it is either a mistake or not stock.
rScotty

I disagree. That is exactly how the wheels on our L3830 are attached. 2 studs with flat nuts and lockwashers, the rest are "normal" fine thread bolts with lockwashers under them.
I can get pictures later on if needed.

Aaron Z

 

[SPYDERLK]

All the bolts say is "7" on them. If I had to guess they are not grade 10.9 (since there's no markings to indicate they are and the silver zinc color).

OK. Good.

I just went out and checked the L3450 (AGs) and the L2900 (Turfs). Both have the 6 bolt hubs using studs and the bolts with a 7 on the head just as you say. ... I pulled one of the bolts from the L2900. I found it to be 16MM with NON captive lockwasher. I removed the washer and replaced it with a Grade 8 flatwasher. I then reassembled dry to 200ftlb and then upped it to 250. No problems. Twice.​

I dont think the 7 is a class marking. -- The bolts are at least class 8.8 to take what I did.

BTW The dish showed damage from the tang of the lockwasher.​

 

[rScotty]

That is how our L3830 is setup.


I disagree. That is exactly how the wheels on our L3830 are attached. 2 studs with flat nuts and lockwashers, the rest are "normal" fine thread bolts with lockwashers under them.
I can get pictures later on if needed.

Aaron Z

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

 

[RickB]

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

The sample of intact wheel hardware rolling around the world indicates to me that this is something other than an engineering failure. It is either an assembly failure (improper wheel or hardware) or a maintenance failure (failure to follow retorquing requirements BEFORE hardware and wheel damage occurs).
Nobody wants t hear this, especially the OP. But I can’t be convinced otherwise based on 22 years at tractor dealership service and parts departments. The old design flaw complaint doesn’t fly.

 

[SPYDERLK]

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

I think the stresses of rocking back and forth on the studs is what caused cracking. Why it rocked at speced torque is the real question. Like I mentioned earlier I dont torque - just whack em down with an air impact. I probably go over 200ftlb. Maybe everybody does and only the ones that tighten only to spec are marginal and may have problems. Also those split washers are a threat that will dig in and eat metal alive if theres movement. This goes critical fast because the dish is then scarred promoting cracking.​

So - Too tight youre alright? Just right/spec and youre out on a limb potentially subsidizing the parts dept?

:confused3:​

 

[ovrszd]

Define loose? Yes they did (and are moving) which means they are not tight enough, or loose. The bolts are torqued down to their correct specifications and have never loosened up. These two are in conflict with each other and in a perfect world it would never happen. But it is. My best guess is (after reading some of the posts) is that the wheels might have too much power coat on them and it's causing the problem. It could be acting as a lubricating agent reducing the clamping force of the bolts. That's all I've got.

Yep. Sounds logical to me.

I'm not sure how buying longer studs is going to work. They are threaded from each end toward the middle? The stud is screwed tightly into the axle hub, then the nut/washer combination is torqued against the wheel. I've not heard confirmation that the studs were loosening in the axle hub? I suspect the problem is how well the nuts tighten on the wheel. Maybe I misunderstood?

Edit: I did misunderstand, sorry.

 

[ovrszd]

The sample of intact wheel hardware rolling around the world indicates to me that this is something other than an engineering failure. It is either an assembly failure (improper wheel or hardware) or a maintenance failure (failure to follow retorquing requirements BEFORE hardware and wheel damage occurs).
Nobody wants t hear this, especially the OP. But I can’t be convinced otherwise based on 22 years at tractor dealership service and parts departments. The old design flaw complaint doesn’t fly.

I agree.

 

[crazyal]

OK. Good.

I just went out and checked the L3450 (AGs) and the L2900 (Turfs). Both have the 6 bolt hubs using studs and the bolts with a 7 on the head just as you say. ... I pulled one of the bolts from the L2900. I found it to be 16MM with NON captive lockwasher. I removed the washer and replaced it with a Grade 8 flatwasher. I then reassembled dry to 200ftlb and then upped it to 250. No problems. Twice.​

I dont think the 7 is a class marking. -- The bolts are at least class 8.8 to take what I did.

BTW The dish showed damage from the tang of the lockwasher.​

I can't tell you how much torque I put on the nut to get the stud to break. I was using a normal breaker bar with a cheater pipe on it (something you can't do with a torque wrench). I think my torque wrench goes up to 250 ft/lbs but anything over 200 is pretty hard to get to because of it's length. It's possible the stud was damaged or that I achieved more than 300ft/lbs.

The sample of intact wheel hardware rolling around the world indicates to me that this is something other than an engineering failure. It is either an assembly failure (improper wheel or hardware) or a maintenance failure (failure to follow retorquing requirements BEFORE hardware and wheel damage occurs).
Nobody wants t hear this, especially the OP. But I can稚 be convinced otherwise based on 22 years at tractor dealership service and parts departments. The old design flaw complaint doesn稚 fly.

My original thought was that the holes for the bolts were made too large but now I'm leaning towards something like paint too thick. Were the 40 series tractors made in the US or Japan? If Japan do they ship with something like cosmoline to prevent rust? I wouldn't think that a little grease on the axle face not being removed before the dealer installed the wheels would be an issue.

What I can tell you is this. With over 35 years of mechanical experience on everything from cars to heavy equipment I have confidence that I know how to use a torque wrench. You don't rebuild hundreds of motors without correctly torquing down bolts. When I was a teenager all I had was a hand me down beam style torque wrench. I could even accept that my torque wrench is out of spec if I had removed the bolts and then reinstalled them by mistake to a lower valve and they loosened up. If I could find a way to blame myself I would gladly do it. Me being the root cause would ease my mind. Learn from my mistake and the problem is solved. However, and I'm not trying to convince you, each time I use the tractor in my mind I'm thinking about possibly loosing a wheel. As of now I don't have a root cause and replace and forget about it isn't the type of person I am.

The last thing I'm trying to do is convince anyone that I didn't make a mistake. **** I make mistakes all the time. Some funny, others costly. That's life. I'm just trying to find an answer because right now I'm just guessing. If other people went out and noticed their ag tires on their 40 series were doing the same thing then I would say design flaw (bolt holes too large) but because nobody else seams to have this problem I've pretty much ruled that out. With that in mind I'm leaning towards replacing the disk that's got the oblong holes in it vs repairing it.

 

[sixdogs]

The other wheel doesn't have the same problems so one would assume something went on with the bad wheel that did not go on with the good wheel?

 

[LD1]

Alot of armchair engineers and Monday morning quarterbacks.

Kubota has been doing this for along time. Hundreds of thousands of tractors without issue....but yup....let's blame it on a design flaw.

In the OP's case....I have no does what happened. Seems to be an isolated incident where something bizarre happened and I have no explanation.

But to blame the MFG, design, or how it was engineered....stupid is an understatement.