Rocky Mountain Altitude transfer cogs wearing.

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
Any other Rocky owners having issues with premature wear of the 12T transfer cog?
I'm on my second cog - the first worked loose at 1000km, the replacement 600km later. The face of the cog wears away where it is clamped by the lock ring, causing the cog to then wear on its internal spline and become loose. This makes a knocking noise which is felt through the cranks. The lock ring remains tight, but it's clamping ability is diminished as the cog face wears. These tiny single-speed type cogs are $99nzd each. Rip off much?
 

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
The cog on the right is the original after 1200km, and the left has done 600km but is worn past the lock nuts ability to hold it. There is a chamfer around the spline which has been made worse by the lock nut. Close inspection of the nut shows only 1mm of actual grip surface, as the steel washer sits within the cog chamfer.
The washer appears to do zilch.
20191110_120827.jpg
 

Zimmerframe

MUPPET
Subscriber
Jun 12, 2019
13,770
20,452
Brittany, France
If the cog is wearing where it's clamped by the lock ring, does the lock ring need changing at the same time as the cog ? If one is wearing, presumably the other is and then when you change the cog, there's more play, hence the second cog wearing faster ?

Which isn't a solution to the actual problem, but might explain the second one's faster demise.

$0.16 per km just for one part doesn't make for cheap riding !
 

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
If the cog is wearing where it's clamped by the lock ring, does the lock ring need changing at the same time as the cog ? If one is wearing, presumably the other is and then when you change the cog, there's more play, hence the second cog wearing faster ?

Which isn't a solution to the actual problem, but might explain the second one's faster demise.

$0.16 per km just for one part doesn't make for cheap riding !

After being shafted for the cog, I was understandably gun-shy to ask the price of a new nut. I've an HG Shimano 12T nut on its way. It's a beefier unit than the existing one, and I'll remove the washer before fitting.
I'd like to know the price of the cog elsewhere in the world...
 

Jeddz

New Member
Sep 8, 2019
9
12
Sydney
Hi. For what it’s worth try facebooks ‘Rocky Mountain Power Play Owners Club’ for great feedback and support. And a quick turn around for any questions you might have. I Have replaced the locking nut which is a shimano 12t cassette lock ring and it has resolved the issue I had with increased wear and noise coming from the motor drive sprocket. So far I’m up to 2200kms and still on my original sprocket without the wear indicated in your photos
 

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
After TIG brazing parts of the chamfer and facing it off in the lathe I'm back using the original cog-which has now covered 1400km in total. I'll do the same to the newer one so I have a spare. There's no good reason for the chamfer as it removes area critical for clamping by the nut.
I don't do fb @Jeddz, but thanks for the info ?
 

albertstancu

Member
Oct 22, 2020
15
2
Europe
Seems like my Altitude 2019 has the same problem, and it play is quite big. The splines are probably really worn because it has a considerable rotational play, and also lateral.

Please check my video. Any thoughts and recommandations ?


I also noticed another problem: The drive cog makes a clicking/knocking sound when manually rotated in drive (clockwise) direction. It's only in the very first moment of the spinning process, when the cog is basically engaged in rotation. It seems to be coming from inside the engine compartment, not from the lockring/cog splines problem. Any ideas ?

 

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
What's happening is the lock nut has worn and is no longer engaging the cog face. The problem you have now is, even if you replace the lock nut, the cog has worn a little too so the new nut won't last long. Being a welder, I used a material called Silicon Bronze (because it's a low temp braze), and welded a dot of it at each spline tooth point to fill the chamfer, and then faced the weld off flush in the lathe. This fixes the problem. I just fitted my 3rd transfer cog at 7000km. I get 3500km out of each one.
Don't worry about the play between the cog and the output drive spline, once the lock nut is torqued to 40Nm on a new cog there is no movement. The cog is made of chromoly steel, the output shaft hardened steel. The cog is softer and therefore designed to wear before the output shaft. If you lived closer I could repair it for you in ten minutes.
 

albertstancu

Member
Oct 22, 2020
15
2
Europe
Thanks. I will order a new cog and find another 12T lockring, as some recommended the Shimano HG one. One with larger contact surface with the cog.

Any idea about the second problem ? The clicking noise
 

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
Hard to say. To me the noise coincides with the cog movement on the spline. There is also a one-way clutch on the output shaft inside the casing, the noise maybe related to that. Personally I wouldn't be too concerned. Once you get a new cog and nut it will be fine until the next time the washer wears off and the cog works loose. Do you know anyone with welding skills and a small lathe by chance? This is the only way I've found to fix them. Throwing out a $100 cog after 1000 or less km and still mint teeth makes me unhappy for some reason... :D
 

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
How many k's have you ridden?
I've not been into the primary chain yet as mine is still running quiet. I would expect it is a standard engineering roller chain which should be available through a local engineering supply shop. Somewhere that sells end mills, drill bits, welding equipment, bearings etc etc. Remove your one and take it to such a business. Based on the price of the the transfer cog (here at least :D ), I'd hate to think what those two primary sprockets will be when they require replacement...
 
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Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
I took my primary chain off to inspect it after your post @albertstancu. Mine is also worn, in fact I'd suggest replacement at 5000km (mine's done 7000km). The chain appears to be a #25 roller chain - 0.25" pitch and 0.125" roller width with a 0.130" dia roller. 52 links incl the master link, 13 inches long. These chains are readily available and low cost.
 
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albertstancu

Member
Oct 22, 2020
15
2
Europe
Don't worry about the play between the cog and the output drive spline, once the lock nut is torqued to 40Nm on a new cog there is no movement. The cog is made of chromoly steel, the output shaft hardened steel. The cog is softer and therefore designed to wear before the output shaft. If you lived closer I could repair it for you in ten minutes.
Guess what. Got a new cog, a new lockring, and seems like the output shaft channels are actually worn. The cog splines dug (ate) in the output shaft channels and enlarged them for more than 1mm. What are my options here ?

The new lockring seems to have a smaller thread area so it pushes against the cog much better, eliminating any play (at least by hand). The problem with with the old lockring was because the thread area was a little bit bigger and when fully tighethened against the freehub, it was not putting enough pressure on the cog because of the tolerances. The new lockring eliminates this problem but my outout shaft channels are worn.

5fc28d4a-cfcd-4c48-bd40-cec23cf51470.jpeg


53ce0cc6-7b03-4a91-a4b8-724c6d9dc37c.jpeg


c1afb432-34ad-4c77-81ec-0925731c5018.jpeg
 

FSEngineer

New Member
Jul 14, 2020
64
40
Kent
wow, nothing to add here except that really is crap and they have clearly made the output shaft from a metal which isn't strong enough for the job they're asking it to do. The phrase "not fit for purpose" springs to mind.
 

Nico

New Member
Aug 5, 2021
3
0
Grenoble
Hello Albert, I have the same problem, even with a new drive cog I have a clearance between the drive cog and the outpout shaft channels, same as in your videoin your last post, can I ask how did you solve this ? Did you have to change the outpout shaft ? If so, did you do it yourself ? Best
 
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Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
Hello Albert, I have the same problem, even with a new drive cog I have a clearance between the drive cog and the output shaft channels, same as in your video in your last post, can I ask how did you solve this ? Did you have to change the output shaft ? If so, did you do it yourself ? Best
Hi Nico.
How much play is there? From new there's a small amount of fore and aft movement between the cog and drive spline. Once the lock nut is tight at 40Nm there should be none. If your spline is as worn as Albert's, you'll need to have it replaced as he did.
This problem seems to happen if wear occurs between the locking nut and cog. You can hear it as each time the motor engages and disengages as there will be a clicking noise that will become more obvious the more the spline wears.
Since I had my motor replaced, the problem has dissipated. The supplied lock nut is of a better quality than the original.
Good luck,
Rik.
 

Nico

New Member
Aug 5, 2021
3
0
Grenoble
Thank you for your response Rik, yes my spines of the output shaft are almost as worn as Albert's so I think ii has to be replace too, Best
 

albertstancu

Member
Oct 22, 2020
15
2
Europe
Hello Albert, I have the same problem, even with a new drive cog I have a clearance between the drive cog and the outpout shaft channels, same as in your videoin your last post, can I ask how did you solve this ? Did you have to change the outpout shaft ? If so, did you do it yourself ? Best

I haven't replaced the output shaft. I've changed only the lockring with the new one, which unlike the old one does really press against the drive cog, keeping it perfectly tight on the output shaft splines. Already 1500 km since then and never had a problem, no play, no wear, no movement, nothing. Basically, the lockring does all the magic, even with the worn output shaft splines.
 

Nico

New Member
Aug 5, 2021
3
0
Grenoble
Hello Albert, thank you for the info, good to know, so I will try like you with a new lockring. Best
 
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Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
I started using a Shimano CS 12T lock ring which was much beefier that the original. The new motor was supplied with a Sunrace lock ring which is also pretty beefy. I've had no problems with either. In any case, just keep an ear out for that clicking noise that will indicate there's an issue.
 

yorel

New Member
Jun 10, 2022
2
1
christchurch NZ
I haven't replaced the output shaft. I've changed only the lockring with the new one, which unlike the old one does really press against the drive cog, keeping it perfectly tight on the output shaft splines. Already 1500 km since then and never had a problem, no play, no wear, no movement, nothing. Basically, the lockring does all the magic, even with the worn output shaft splines.

Hi Albert, I know it has been a while since you made this post but I have the same issue. Can. I ask you which lockring you purchased?

Thanks
Julien
 

Flatslide

E*POWAH Master
Jul 14, 2019
265
250
Dunedin NZ
Hi Albert, I know it has been a while since you made this post but I have the same issue. Can. I ask you which lockring you purchased?

Thanks
Julien
Hi bud.
This is the same lockring my new motor was supplied with LOCKRING CASSETTE 12T 8/9SP SUN RACE.
If you can find a 12T Shimano lockring (for an 8-9 spd), these are good too. I've ridden over 5000km on that motor now, still using the original lockring, although it's nearly due to change.
Good luck.
 

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