Modifying a pedelec disc

[thomas russell]

Hi,
I'm currently fitting an 8fun kit to an old but little used mountain bike.
the pedelec disc is small - about 60mm diameter and 3 mm thick so it fits easily if I remove the granny ring as some have suggested. unfortunately I'm 69 and I live at the top of a two mile hill and dread having to peadal up that if the battery runs out so I'd like to keep the granny ring if I can.

I have no idea what's inside the pedelec disc but suspect its just a support for five magnets. Would it be ok to deremel out some recesses to clear the bolt flanges of the ring, as in the attached picture, so that it would sit neatly inside the granny ring.

Would that work?

Thanks

Thomas

 

[jackhandy]

EVENING Thomas,

I fitted mine on the left-hand side - It fitted better there than on the chainring side.
Y
You just need to check the pas works when you rotate the pedals forwards before you tighten up the crank: if not, turn the magnet ring over & check again.

 

[thomas russell]

Hi Jackhandy,

Thanks for that.
I had read that some had done that but i'l be parking at the local station with lots of bikes together and felt that, if the disc was out of the way, it would be less prone to damage.

Regards

Thomas

 

[peerjay56]

Thomas,

I did exactly as you propose when fitting an alien ocean kit to my wifes bike, but not before busting the disc on my first attempt at fitting it, because I 'assumed' it would fit without modification. 6 months on and all is still working well. Jim kindly sent me a replacement disc!

Phil

Hi,
I'm currently fitting an 8fun kit to an old but little used mountain bike.
the pedelec disc is small - about 60mm diameter and 3 mm thick so it fits easily if I remove the granny ring as some have suggested. unfortunately I'm 69 and I live at the top of a two mile hill and dread having to peadal up that if the battery runs out so I'd like to keep the granny ring if I can.

I have no idea what's inside the pedelec disc but suspect its just a support for five magnets. Would it be ok to deremel out some recesses to clear the bolt flanges of the ring, as in the attached picture, so that it would sit neatly inside the granny ring.

Would that work?

Thanks

Thomas

 

[flecc]

The disc is indeed just a support for the magnets and can be modified.

 

[peerjay56]

Managed to find this photo of my modification. Not only did I modify the stator disc, I also trimmed the granny crank disc. I even cleaned up more of the rust from the crank - a sign of how little the bike was being used before the modification (nothing to do with the maintenance regime, Honest!)


Phil

 

[thomas russell]

Hi,

Thanks for all the useful posts. I think my question is answered.

This forum is great

Regards

Tom

 

[rpurchon]

you could even glue the magnets in the chainring bolts.and alter the bracket or glue and cable tie the sensor in a siutable place.
test before glueing though,might work pedaling backwards.if so just turn the magnets around.
if you take the magnets out of the disk mark them with a felt pen so you keep all the polaritys the same.
ie all south or north.
richard

 

[thomas russell]

you could even glue the magnets in the chainring bolts.and alter the bracket or glue and cable tie the sensor in a siutable place.
test before glueing though,might work pedaling backwards.if so just turn the magnets around.
if you take the magnets out of the disk mark them with a felt pen so you keep all the polaritys the same.
ie all south or north.
richard

Hi
That's a good idea. I think modifying the disc should work ok but thanks for the tip. I'll mark the magnets on one side before drilling and cutting so if one falls out I can replace it in the correct orientation.

Thanks,

Tom

 

[thomas russell]

Hi,

I'm now thinking of another kit, this one has a 12 magnet disk and corresponding sensor.

Would it be possible to replace it with a 5 magnet disc and its sensor as this is easier to modify to fit my bike? or would I need a different control box?

Sorry if this is a stupid question but I dont really know how they work

thanks,
Tom

 

[Deleted member 4366]

The sensor is a hall-effect sensor. When a North facing magnet passes it in the right direction, it switches on, and a South facing magnet switches it off. Some magnet disks have the magnets in the direction of motion,so the sensor gets a N and a S as each magnet passes, and some face in the axial direction, so you need two magnets to switch on and off. The controller only sees the on/off pulses, and it counts them in a fixed time to see if you're pedalling. It'll probably work with either, but you might need to pedal a bit longer before the power kicks in. I know somebody before changed from a ten magnet ring to a five magnet one, and it worked OK.

Not all controllers are the same. There's some that look for an analogue signal on the PAS input, so you need an analogue sensor. The only sure way to knoow is to tell us which one you want to buy, or try it.