How long should my chainwheel last?

[Deleted member 4366]

Nice theory, but the only reason the chain-wheel has a burr on it is because it hasn't been properly hardened, or they used the wrong grade material. I've never seen burrs on one before. They normally just wear away.

 

[flecc]

The torque sensor has an important role in what you are saying James. Ideally if the rider exactly balances the motor force, the only wear the chainwheel would suffer is the radial pressure in the teeth valleys. However, that matching is impossible due to the torque sensor action.

First the rider applies pressure to the torque sensor on each downstroke which will produce the normal pattern of bike chainwheel wear. The motor then responds to the torque sensor signal and this can change the wear pattern to neutral or the opposite direction, depending on the ratio of rider to motor drive force. Inevitably the high power mode is likely to accentuate the opposite from the normal rider only wear pattern. These assumptions are based upon a meaningful lag between rider input and motor response, and given the range of normal cadences I think there will be sufficient pedal arc lag and also motor run-on after the torque sensor signal reduces to produce the differences I mention.

 

[Deleted member 4366]

Have you ever seen burrs like that on a chain-wheel, Flecc?

 

[flecc]

Have you ever seen burrs like that on a chain-wheel, Flecc?

No, and I agree that the chainwheel wasn't hardened enough, indeed I posted as such on danfoto's earlier thread on this problem, link here.

 

[JamesC]

Does that mean that you would expect much less chainwheel wear on a Panasonic crank drive used at 1:1 assist, compared with other other types of bicycle ?

I have seen lightweight alloy chainrings that I would not recommend for an Agattu / ProConnect.

As has been mentioned earlier, an alloy chainring lasted fine on my Torq 1 with its front wheel hub drive.

James

 

[flecc]

I would expect less on the Panasonic system James, and that was borne out in practice on my Giant Lafree Twist on which I rode well over 6000 miles before selling it to another member who used it for a couple of years before selling it on again.

The transmission was all original when I sold it and the chainwheel was in excellent condition, and I doubt it had further attention before it's second selling on. Crucially of course the Lafree did not have a high power mode, only Normal, 1 to 1 power ratio and the 0.5 to 1 Eco mode which I never used. I did frequently ride on the flat with the power off since it was very free running and only 22 kilos.

 

[JamesC]

If you had done the same type of work with an unpowered bike like the Giant Lafree, at what type of mileage would you have expected to replace the chainwheel ?

 

[danfoto]

Well, the chainwheels and motor sprockets have just arrived, and they are indeed 2mm thick.

I won't be able to do anything about fitting them until nearer the weekend, but I have to say that IMO the new chainwheel is a singularly unimpressive item. Sure it's a clever bit of metal-bashing, what with the splined collar on it and all, but I do wish I had access to a hardness-tester nowadays. I'm always deeply suspicious of any power-train part which is chromed as much as this one is.

BTW, notwithstanding 50 Cycles saying the wear on mine is par for the course, I still reckon that if this chainwheel is in fact heat-treated, it isn't heat-treated properly for the application. Every worn chainwheel or sprocket I've seen in the last 50 years or so has been just that - worn. I've never seen deformation/burring like this, and if that's what this chainwheel is supposed to do, I'd love it for somebody to explain why!

I'll report back ASAP ...

 

[Deleted member 4366]

It's probably a result of deliberate cost-cutting rather than an omission in production, or they were trying to solve one problem, but created another. It would be nice to know how other Agattus of the same age are getting on. It's a shame because Kalkhoff had a reputation for dependable German engineering, but that looks worse than the cheapest Chinese ones. Soon we'll be seeing how well Woosh CD chainwheels last, then we'll know which bike to buy.

 

[flecc]

Of course this chainwheel is a Panasonic product, made in either Japan or China and the power unit just fitted in Germany. Panasonic seem to regard the chainwheel as part of the unit since even boxed replacement units I've seen come with the chainwheel and motor sprocket prefitted.

Some Agattus now coming with the German Impulse motor unit will confuse the situation further if the power unit isn't specified when reporting problems on these models.
.

 

[flecc]

If you had done the same type of work with an unpowered bike like the Giant Lafree, at what type of mileage would you have expected to replace the chainwheel ?

I can't say James, for some decades now of low cost bikes I've never kept bikes long enough to reach end of chainwheel life, though I've replaced the rest of the transmission at times. Of course that alone speaks of good chainwheel lives, having compatibility with a new chain.

 

[JamesC]

Danfoto

I have probably missed a post in one of your other threads, but please would you confirm whether your chainwheel is 41 teeth or 35 teeth.

As I mentioned earlier, with the 41 I know that you have the option to go for the wider tooth (3mm) Panasonic chainwheel which is normally associated with the 1/8" chain.

The 35 was first seen on the derailleur 9/10/11 speed bikes and for those it had to have narrow teeth.

If your Agattu is using the 35 and a wide tooth version is unavailable (as I suspect), then it might be worth considering an alteration to the sprockets to use the 41.


Can anyone remind me what the advantage of the 35 chainwheel was for a utility, trailer pulling, Agattu with Nexus 8 speed hub gear ? Did the motor change at this time ?

James

 

[flecc]

Can anyone remind me what the advantage of the 35 chainwheel was for a utility, trailer pulling, Agattu with Nexus 8 speed hub gear ? Did the motor change at this time ?

James

The only change I saw was the marked reduction on the rear sprocket size on the Nexus hub gear to maintain the assist speed limit at 15 mph. With the 41 tooth chainwheel and 9 tooth motor sprocket the original Agattu/Nexus used a 22 tooth rear sprocket, the Pro Connect a 23 tooth. With the 35 tooth chainwheel they used a 19 tooth rear sprocket. This made me suspicious that the change to the 35 tooth chainwheel had more to do with legality than anything else.

For example, changing the rear sprocket of a 41 tooth chainwheel/9 tooth motor sprocket Agattu to 16 teeth meant an increase in the assist speed limit to roughly 20 mph. However, with a 35 tooth chainwheel and smallest possible 16 tooth sprocket, that increase could only be to 17 mph, which happens to coincide with the 10% tolerance normally allowed on speed limits! (25 kph plus 10% = 27.5 kph or 17.2 mph)

I'm always suspicious of such coincidences.
.

 

[JamesC]

Of course this chainwheel is a Panasonic product, made in either Japan or China and the power unit just fitted in Germany. Panasonic seem to regard the chainwheel as part of the unit since even boxed replacement units I've seen come with the chainwheel and motor sprocket prefitted.

Some Agattus now coming with the German Impulse motor unit will confuse the situation further if the power unit isn't specified when reporting problems on these models.
.

Good work is going on in Germany on the common drive parts.

Wippermann Connex now make 9 T and 11 T motor sprockets in 2.20 mm width, which is best suited to 3/32", 7/8 speed derailleur chain (or the wider 1/8" chain). These are too thick for 9/10/11 speed chain.

Page down on this link.

The quality looks very good, but I have not yet fitted the sprocket to be able to give a personal report. I understand that chainwheels manufactured in Germany are expected quite soon.

James

 

[flecc]

I knew of the German replacement motor sprockets, but it's good to hear of the chainwheels as well. However, as remarked above, Panasonic practice has always been that the motor units are delivered complete with chainwheel and motor sprocket as integral parts, so unless that changes new models will start life with Panasonic transmission components.

 

[JamesC]

I knew of the German replacement motor sprockets, but it's good to hear of the chainwheels as well. However, as remarked above, Panasonic practice has always been that the motor units are delivered complete with chainwheel and motor sprocket as integral parts, so unless that changes new models will start life with Panasonic transmission components.

Understood, but it is good that a lot of discussion is ongoing as to where improvements can be made.

As far as I can tell, there have not been many issues with the Panasonic motors; there is good cover with respect to battery manufacture and specialist transmission parts. Good prospects for existing owners.

 

[flecc]

As far as I can tell, there have not been many issues with the Panasonic motors

Yes, they have very successfully dealt with the known issues that affected a few of the first series units, and the second series has been very reliable internally from early 2007 onwards. The problems seem to have been mainly external transmission ones, particularly with respect to the motor sprocket/idler area. They may eventually have second thoughts about having the separate motor sprocket, given that the chainwheel motor drive on all the competitors is so much more reliable.

 

[JamesC]

Certainly there will be developments in the future, but the present does not look too bad for existing owners of 5 year old bikes. Many of these will have Panasonic motors, and many will still scrub up very well.

Good to know that sufficient units have been sold to generate an after sales market across Europe, and good to know that lessons learnt over 10 or 20,000 miles can still be built into the service parts.

I have been very conscious that successful products like the Giant Lafree became difficult to service as time went by. Possibly the market was too small.

I am hopeful that the 26v Panasonic bikes are out there in sufficient numbers to justify a new lease of life with fresh batteries etc.

James

 

[JamesC]

The only change I saw was the marked reduction on the rear sprocket size on the Nexus hub gear to maintain the assist speed limit at 15 mph. With the 41 tooth chainwheel and 9 tooth motor sprocket the original Agattu/Nexus used a 22 tooth rear sprocket, the Pro Connect a 23 tooth. With the 35 tooth chainwheel they used a 19 tooth rear sprocket. This made me suspicious that the change to the 35 tooth chainwheel had more to do with legality than anything else.

For example, changing the rear sprocket of a 41 tooth chainwheel/9 tooth motor sprocket Agattu to 16 teeth meant an increase in the assist speed limit to roughly 20 mph. However, with a 35 tooth chainwheel and smallest possible 16 tooth sprocket, that increase could only be to 17 mph, which happens to coincide with the 10% tolerance normally allowed on speed limits! (25 kph plus 10% = 27.5 kph or 17.2 mph)

I'm always suspicious of such coincidences.
.

That is exactly my memory of the change, having nothing to do with any benefits to performance.

Personally, for good sprocket and chain life, I would far rather see 41/23 than 35/16 on the 8 speed Nexus. No point in torturing the chain round small sprockets unnecessarily.


We have not discussed the question of unnecessary chain width !

Danfoto has already said that the chainwheel is 2mm wide (waiting to hear how many teeth). I think that this will mean that his widest component in the transmission circuit is 2.25mm on the hub sprocket.

Personally, I would use 3/32" chain as a prettier engineering approach.

Does anyone think that using a wide, 1/8", chain on narrow sprockets contributes to rapid wear, or is it just a bit clunky ?

James

 

[danfoto]

James, chainwheel's 41T, with 12T motor sprocket.

I've also now got standard replacement chains for both our Agattus coming from 50 Cycles. The idea is that while these bikes are still under guarantee, if I fit kosher replacements bought from the importer, we don't lay ourselves open to any "oh dear, you've invalidated the guarantee" nonsense.

Once the new sprockets are fitted, though, we'll be swapping chains for cleaned and lubricated ones and wiping the sprockets clean every 500 miles, and believe me I shall be watching very closely indeed for a recurrence of the problem.