Wisper 905SE City (2009) pedelec sensor - "bug" or "feature"?

[Alex728]

Over the past week or so i had noticed an intermittent power delivery on pedelec mode when I was in "stop start" type of traffic. it had gone mostly unnoticed because I tend to use the throttle more (whilst still pedalling) but started to get particularly bad in the last few days.

On closer inspection, I noticed the pedelec sensor disk (with the magnets) wasn't always going round, particularly on backpedalling or if you pedalled for a revolutions, then stopped and started again (as you would normally do in traffic).

At first I thought this was how the bike worked out what direction you were going in, but other threads on here point out its done by putting the magnets in with unequal spacing. but it does appear that some sort of cam/slipping clutch type thing is present on the sensor disk - as when it wasn't turning if you turned the pedals round eventually something would engage and turn the sensor disk.

As I don't have the tools to pull the crank and inspect the disk I couldn't see exactly what was there, and there was no evidence of anything being dislodged or damaged. Whist I did have the cranks inspected by a mechanic this issue was happening previously (but masked by me using the throttle) and as far as I can tell he only tightened the crank bolts and did not remove the cranks (and is a well respected mechanic who has worked on e-bikes before)...

So I wondered if there was excessive friction between the other side of the pedelec sensor disk and it was rubbing against the securing collar of bottom bracket and then stopping moving until the cam came round again, and sprayed a small amount of light lubricant there - enough to free the disk but not so much as to get into the bottom bracket. Now the sensor disk spins freely - I think this is also the first time the bike got exposed to rain/colder weather so maybe some water/dirt got in somewhere?

I wonder if the slipping is a deliberate "feature" - so that if something gets stuck in there or the bike dumps its chain and it ends up fouling the sensor disk the entire pedelec sensor won't get trashed (such as being sheared off the crank axle)?

Would be interested to know what Wisper have to say, but in the meantime maybe this info might be of use to other owners who get odd issues like this in pedelec mode...

 

[Alex728]

Update : the pedelec function has worked fine today - clearly something "jammed up the works" earlier on.

Hopefully it will now stay working (if kept clean) as pulling the cranks is going to be a bit of extra work but I am curious as to whether anyone has experienced this issue?

on the Powacycle Salisbury it looks like a different approach has been taken with one part of pedelec disk (with the magnets) being physically fixed onto the chain ring and this being enclosed by the rear part of the assembly...

 

[Alex728]

Any comment from Wisper on whether this is actually an issue or a feature? It briefly re-occurred yesterday but seems to be combated by keeping the pedelec disk clean and lubricated and checking it moves correctly..

I've seen other reports on this forum of issues with the sensor on earlier models - these were apparently solved by adjusting the distance between the disk and then sensor, but the method of doing this hinted at a different mounting arrangement to what is on a 2009 model. Has the design of this sensor changed?

Due to the ability to use the throttle as a workaround and the intermittent nature I'd class it as an annoyance rather than a major/dangerous fault, but would hope to get it sorted eventually...

 

[Norman]

Pedelec sensor

Sorry to hear you are having this problem.

The pedelec sensor depends on a good fit between the disc containing the magnets and the bottom bracket (pedal) axle. This is achieved by a series of small teeth moulded into the centre of the disc that grips the axle.

This arrangement allows for the disc to be slid sideways towards the sensor during installation or maintenance until a gap of about 1 mm is achieved between the tip of the fixed sensor and the disc. The fixed sensor should not touch the disc and no lubrication should be applied.

A periodic check is recommended to make sure this gap is maintained through a full 360 degree turn of the crank as the sensor bracket can be accidentally bent during use or mud etc can accumulate which can impact on the proper operation of the sensor.

If your disc is spinning independently on the axle we will need to provide you with a replacement disc. Fitting would be best left to the dealer you purchased this bike from. I can provide further advice on fitting if you email me on the address below.

regards

Norman

Norman Hopkinson

Wisper Service
wisper.service@wisperbikes.com
See the whole range @
wisperbikes.com

.

 

[Alex728]

an update : Norman sent me a new pedelec sensor (just days after reporting the issue) - the plastic teeth on the old one had got slightly bent in one direction hence the ratchet effect.

All is working fine now..

On a lighter note. the new disk came with a small label marked 工作面.

For some reason it reminded me of those messages that randomly get sent to dudes in martial arts movies to the sound of a large gong (although this was a tiny label so I expect it the correct sound should be a small bicycle bell)

Somewhat intrigued by its content it I saved the label so to input the three characters to my portable "Chinglish" translator (a present my mum brought back from Malaysia last year) - but all it meant was just "working surface" (i.e which way round the sensor should be). Sensible enough (as the embossed arrows might not as noticeable in the production environment) but I have to admit I was a bit disappointed as it took me ages to input the last character, it taught me a lot of respect for those who read and write Chinese daily....