My Output Shaft Snapped.

[Rashid510]

Based on my motor-replacement experience in my non-Alta bike, if this happened to me I'd change out the entire motor if feasible (I was surprised at the difference fresh magnets made!) and/or send the old one out to Accu Electric or similar for shaft/bearing/seal etc. replacement - remagnetizing - rebalancing if needed.

Unlike a Zero, removing the motor isnt persay needed. And doesnt need rebalancing (Fukuta took care of that.. )

 

[bearorso]

So 'they' - whoever designed the shaft etc, perhaps Not Alta - put an O'ring groove into a shaft, instead of into the collar, as the vast majority of MC makers do with relation to the countershaft sealing.

For a bike with, generally, such intelligent design, this ranks as base foolishness. This sort of thing Will happen to other Altas. If , what I think is a collar, is used, it might be a good idea to do a group buy of a re-engineered 'countershaft', with a collar to take a seal. It doesn't have to be an Oring, quite a few designs have low profile seals.

 

[TCMB371]

So 'they' - whoever designed the shaft etc, perhaps Not Alta - put an O'ring groove into a shaft, instead of into the collar, as the vast majority of MC makers do with relation to the countershaft sealing.

For a bike with, generally, such intelligent design, this ranks as base foolishness. This sort of thing Will happen to other Altas. If , what I think is a collar, is used, it might be a good idea to do a group buy of a re-engineered 'countershaft', with a collar to take a seal. It doesn't have to be an Oring, quite a few designs have low profile seals.

There's an oring on the inward side of the collar as well. So there's 2 points of sealing in that area; the shaft oring and the collar oring.

 

[snydes]

TCMB rides his bike harder than the average owner, and this is the first instance of this we’ve been made aware of. Group buys of re-engineered shafts would be unrealistic. If this were a common failure then perhaps. It would be more practical to do as Mark911 proposed on existing new shafts to lessen the likelihood of a crack from propagating.

 

[#76]

Bryan*, was you running the 14t still when this happened?.

 

[TCMB371]

Brian, was you running the 14t still when this happened?.

Yes

 

[bearorso]

TCMB rides his bike harder than the average owner, and this is the first instance of this we’ve been made aware of. Group buys of re-engineered shafts would be unrealistic. If this were a common failure then perhaps. It would be more practical to do as Mark911 proposed on existing new shafts to lessen the likelihood of a crack from propagating.

I suggested a group buy, as this is where Alta owners congregate.

If I owned one - I had intended to get an Alta, but they closed up just as I was going to order one - after seeing this, I'd be having a new shaft made myself. It's a quite simple shaft, compared to other main and countershafts I've had made for problematic gearboxes I've dealt with over the decades. So even as a 'one off', it would not be particularly expensive. Perhaps $400 AUD, at the most, with a re-done collar to take another sealing solution. As a 'group buy' for even a small quantity, the cost would be much less.

As to machining the original groove to have radii -well you'd be further reducing the diameter at a Major stress point, and, more than likely, having to re-harden the shaft , If that were possible.

It's a dreadful design that Will probably rear it's head on more bikes - it's not perhaps of Alta's doing, but it's still dreadful. But, I guess some here will just get their backs up with what I've said, not being able to take a legitimate engineering criticism. It's a damned shame they went belly up, and I am anxiously awaiting the release of other manufacturers E bikes, of the same 'type' - eg, Full Enduro / MX spec, not glorified MTBs, nor "halfway between a Trials Bike and Enduro Bike" that the KTM 'E' Freeride is, to me. I've ridden that quite a few times when I've been in Europe, it's good for what it is, but I want an E Bike as I have described earlier. Like the Alta's were.

 

[TCMB371]

Here's the footage when it happened.... for the record.

 

[bearorso]

You are a Very Lucky man, in your bad luck.

 

[Mark911]

This is the simple mod I'd do. A very small ball end Dremel tool/stone and a lathe (or something to spin the shift while cutting/grinding) followed by some polishing. Not reducing the shaft diameter, just getting rid of the sharp shoulder (stress riser). No heat treatment necessary. If that fails then yes, a redesigned shaft would be required.

 

[C5tor]

Here's the footage when it happened.... for the record.

On the plus side, you sure found a way to get rid of that annoying “whirring” sound the bike makes. Sure was quiet at the end. Except for the swearing part.

 

[Warren]

Here's the footage when it happened.... for the record.

 

[Fourth_Floor]

Man that freaks me out!! Thank God that happened where it did and not up the face of a big jump. How concerned should us other Alta owners be that this failure is destined to happen to our bikes? I'm hitting fmx ramps on mine so this freaks me out a bit.

 

[VINSANITY]

Maybe someone with 180 hours on there bike (same hours where TCMB371 shaft failed) can swap out a new shaft and then we can get the shaft sectioned to look for signs of failure.

 

[bearorso]

This is the simple mod I'd do. A very small ball end Dremel tool/stone and a lathe (or something to spin the shift while cutting/grinding) followed by some polishing. Not reducing the shaft diameter, just getting rid of the sharp shoulder (stress riser). No heat treatment necessary. If that fails then yes, a redesigned shaft would be required.
View attachment 7548

Well, that 'solution' would guarantee failure.

 

[leeo45]

Bryan, I suspect this may already be in your plans, but if not it would be great if you could do a pictorial and write-up of the shaft swap out once the new part arrives. I hope it's something I never need to deal with, however if I do, a guide would certainly be a great help.

I know it would be extra work for you so not a big deal if it slows down your bike resurrection. Rashid's pictures and McM-C links earlier in thread are already a very good start on understanding the process.

 

[TCMB371]

Yeah i may do a little write-up. I'm thinking of taking this opportunity to do a complete rebuild of the bike with all new bearings, seals, and gaskets. Luckily i purchased a few sets of spare gaskets before Alta closed shop.

FYI, the procedure is in the Owners Manual. Its a pretty lengthy process.

 

[TCMB371]

New hard parts arrived. Just waiting on various orings from McMaster Carr.

 

[Mark911]

Well, that 'solution' would guarantee failure.

Well, just based on a quick analysis using ANSYS, putting a radius as I showed reduces local stress by about 20%. Using the fatigue tool in ANSYS the same mod increases the safety factor of the entire shaft by about the same. I'm not saying these are absolute numbers as I don't have the exact material modeled or know the exact loading/cycle profile. I also had to increase the corner radius from my initial SWAG (scientific wild ass guess). However, it's a good indicator of the general direction and magnitude of the mod. So please let me know what I'm missing, I'm always looking to learn.

 

[enjoythesilenc]

Can you look at your ride logs and tell how fast your rear wheel is spinning when you land a huge jump? Say your ground speed is 30mph and the wheel is going 70mph when you touch down. instantaneous deceleration?

I wonder if a ktm cush drive hub would help a shaft to survive, flatten the curve, so to speak.

KTM PowerParts Cush Drive Rubber Dampers

www.motosport.com