rear bevel box

[swooshdave]

 

[docc]

Yes sir, I've been studying that exploded view, and what photos I can find. Curiously, the Workshop Manual does not provide any detail on the deeper bearing or the seal behind it.

 

It appears bearing #26 is pressed into the crown and bearing #36 is pressed into the housing cover. When assembled, those two bearings carry the crown between the housing cover and the axle as I described above?

[swooshdave]

Perhaps Shiloh can loose assemble the parts with the axle and take some pics? So few of us have been inside one of these things.

 

I suspect that once assembled there's not as much sideways torque on the crown as one would assume and everything just spins.

[luhbo]

Sorry if I ask a bit silly, but which bearing is missing now? Number 12 or number 26? A missing 26 would mean hard life for 27, a missing 12 would be not so much a problem because you still have 30, 31 and 26.

 

Again, is 12 really missing or just unnecessary weight and money?

 

For Docc: 36 is inside the crown, on the axle, 26 is inside the cover 23. That means, the crown is running on 36 and the rear wheel, the housing is running on 26 and 12. 30/31 is needed only for the suspension movement. That's why it's always rusty and that's why it's enough if you keep the rust away from it. It doesn't really move.

[bbolesaz]

I would appear that bearing 26 and 36 are somewhat redundant. Bearing 12, 30 and 26 bear the case to the axle. 26 and 36 bear the crown gear to the axle and case.

 

I think the issue is that the case DOES move relative to the axle, it does that when the suspension goes up and down and case pivots relative to the arm.

[GuzziMoto]

 

Ok, then how would it work? We have the rear wheel sitting on two bearings, we have the crown wheel sitting with one side on a bearing, the other side being centered on the driving cog, and we have the housing sitting with one side on the rusty needle cage, the other side being held by the shaft seal. I can imagine that this might work quite well even. Maybe better so as with the big needle bearing installed. Would it be software, I'd say it's a feature, not a bug.

So, I'm having trouble understanding what the three transverse bearings are doing.

 

The right side (deeper one/ the one found missing in this case) is pressed into the rear drive housing and its inner sits on the axle? (Neither of those things actually spin . . . )

 

And the other bearings (on the wheel side)? They are pressed onto/into the crown wheel (ring gear)? The larger (outer) allows the crown to spin in the housing cover and the smaller (inner) allows the gear to spin on the axle?

 

Yes, I agree. I don't see what the "missing bearing" would actually do. No offense was meant putting that in quotes, just not sure that bearing is actually doing anything. A bearing is (sorry to state the obvious) needed when you have two parts that move in relation to each other in a circular fashion. The housing clearly doesn't spin, and the axle doesn't spin. Where is the motion? I don't see how there is relative circular motion between the two. Maybe I am missing something, maybe there is relative circular motion between the housing and the axle. But I don't see it.

Perhaps everyone else's rear housing has this bearing and yours doesn't. Or maybe you aren't alone, maybe the bearing is not really required. It seems hard to imagine that the bearing is required but yours was able to go as far as it did without catastrophic failure.

 

But I am not looking at one in front of me, I could be totally wrong.

[docc]

Sorry if I ask a bit silly, but which bearing is missing now? Number 12 or number 26?

 

My understanding is that shiloh found #12 missing.

I would appear that bearing 26 and 36 are somewhat redundant. Bearing 12, 30 and 26 bear the case to the axle. 26 and 36 bear the crown gear to the axle and case.

 

I think the issue is that the case DOES move relative to the axle, it does that when the suspension goes up and down and case pivots relative to the arm.

#30 is the "rusty needle cage" that luhbo refers to. It is on the outside of the housing next to the swingarm on the right. It does not spin, but rotates slightly with suspension moment and helps locate the housing on the axle.

 

Perhaps the nefarious Bearing #12 is what performs this function primarily and the needle cage less so?

 

In that event, if Bearing #12 has been missing, I would perform a close inspection of the "needle cage" #30. It may have been doing all of that work solo. It looks "fine" in the posted photo, but there is a "sleeve" #31 to inspect as well.

[luhbo]

edited my post above. It's hard to keep track with such fast moving threads.

 

edit again: a missing 12 would not be much of a problem for 30/31. It's sitting on a long lever and it sees not much movement.

 

next edit: get rid of 12, there's no need for it.

[swooshdave]

Well, in 20 years when I have to get into the rear drive I hope I remember all of this. 

[luhbo]

I'd be glad when in 20 years I'd still remember this forum at all

[coreytrevor]

I'll throw my  in to confuse things further.

I don't think 30/31 can do any supporting of the crownwheel. They just interface between the axle and gearcase, basically holding up the swingarm side of the gearcase and letting it rotate a bit on the axle with suspension movement.

 

36 is the only other apparent support for the wheel side of the gearcase to the axle. It just happens to be mounted in the crownwheel but will still carry the weight of the wheel side of the case. Otherwise the weight of the wheel side of the case would just be resting on the drive spline.

 

12 and 26 are the crownwheel bearings, supporting it to the gearcase housing and cover.

 

It seems that if 12 were missing, then 36 would have to stand in for it and take a lot of the load of the crownwheel torque. Without 36, there's no support for the case end of the crownwheel. 30 and 31 are fully outboard of the crownwheel.

 

Of course I'm not looking at one in person so who knows if I'm making any sense.

[luhbo]

Ok then, different approach: Imagine the crownwheel being welded firmly to the rear wheel. This unit would need only two bearings to the axle, namely the one at the brake disk and one on the other side, this being the number 36 from the schematics above and also shown in one of the pictures previously posted (inside the crown).

Next we add the housing, put it over this combo. To support it and to allow the crown-rear wheel combo spin freely in it we need another two bearings, these being on the spinning rear wheel side number 26, on the opposite, non spinning side that's number 30/31. This would be sufficient.

Now when we add a third bearing (12) this system becomes over-constrained. To get it working you have to keep rather tight co-axiality tolerances for the inner and outer bearing seats. To complicate things further you have to make sure that the cover goes into the housing with as little play as possible, also just a matter of costs.

Obviously it's not a really big disadvantage for the factory if they just forget the number 12 from time to time. We don't know what happened, could have been no bearings available, could have been a batch of poorly made housings or crown wheels, could have been a tired Luigi just as well.

[shiloh]

Ok, from an engineering view point, look only at the crown gear assembly, you have a mounting plate that attaches it to the housing so it does not move. The crown is made up of basically 4 components, the gear #29, rotational ball bearing  open cage #26 allows the crown to rotate and transfer that motion to the wheel. Outer support  bearing #36{(sealed ball race same as a typical wheel bearing),(is also outside of the outer seal not in contact with gear oil)} and lastly the inner support needle bearing #12.

#`s 12 and 36 are longitudinal supports, helps in eliminating wobble, only #36 is in contact with the axle and it spins at speed with the crown, #12 supports the biggish tube thinggy on the inward side of the crown(crown shaft I suppose), that bearing is pressed into the housing, the crown shaft inserts into it.

The crown shaft is hollow and the axle goes through it, the 2 seals at either end contains the gear oil, you can also view bearings #30/31 and #36 as alignment/pivot points for the axle.

So why did my rear end not wobble to pieces, I believe that #36 and #30/31 made up for it some what, but probably for not much longer as they  are on their way out, if either of those two had failed/collapsed, the rear end would have exploded, maybe, or at the very least seized and transfered that energy else where, parish the thought.

 

As mention earlier, I will post re-assembly photos, to show how every thing fits together and works.

 

Heres a simple analogy of the crown assembly, play with one of those spinny tops that has a caged central wheel and a shaft running through it, spin the top and support each end of the shaft on the horizontal, it will spin true, remove one end support  and you`ll see it will wobble into an unstable condition, simple right, everyones played with a top before.

As luhbo stated above, all this is supported with in close tolerances and very confined spaces, this too could add to the over all stability without bearing #12.

 

[docc]

Ok, fascinating.

 

#12 is really "needle" or actually balls?

 

(" . . . the inner support needle bearing #12.")

[shiloh]

Ok, fascinating.

 

#12 is really "needle" or actually balls?

 

(" . . . the inner support needle bearing #12.")

Yes, needle, exposed to the gear oil, so always lubed, same as #26 exposed and always lubed