Smart Pie 4 ball bearing repair

[Pramot]

Hi,
I have used Smart Pie 4 for 2.5 years, 43,000 km. to deliver organic veg & fruit juice in Thailand.
last year It was in flooded road, all part of motor was in the water but It still work.
It works perfectly with no maintenance at all, that's my fault.
Until yesterday, the hub is stuck because of broken ball bearing, attached photo is after I removed broken tiny metal pieces.
Could you give me advice if I can fix it and how?

Thanks,
Pramot

[Bikemad]

Hi Pramot andto the forum.

Before you start, apply some penetrating oil around the bearing and mating flanges and let it soak for a while to make the bearing and/or cover removal easier.

To replace the bearing, you will need to remove the side cover in the picture (if it's not already removed) by removing the 8 Allen bolts around the outside which are holding it onto the hub/motor ring section.

I strongly recommend that you redistribute the balls evenly around the bearing before applying any force, and you will then hopefully be able to pull/drift the bearing off along with the cover, if the inner race is not badly corroded onto the stator.
If you don't redistribute the balls evenly around the bearing, the bearing is likely to separate completely, allowing the outer part to come away with the cover, which would make it much more difficult to remove the inner race from the stator and the outer race from the cover on their own.

I suspect the cover will be tight to separate from the hub assembly as the two components will probably be stuck together with corrosion.
You may need to use a knife blade or thin bladed chisel between the two components in order to carefully prise them apart.

You should be able to drift the bearing and side cover off the stator from the opposite side using a piece of hard wooden dowel or an aluminium or brass drift to minimise damage to the cover:



Tap all around the bearing (not just in one spot) to ensure it comes off evenly without tilting sideways and jamming into the stator.

Once the cover and bearing has been removed, you should be able to drift the bearing out of the cover by drifting against the inner race of the bearing from the outer side:



The drift should be perpendicular to the side of the bearing, not at an acute angle as it appears to be in the above image. 

If you have an old paint tin to rest the cover onto, you should be able to drift the bearing out more easily.
If it is really tight, you might want to warm up the cover in an oven to allow it to expand, which should allow the bearing to drift out more easily.

According to this post, the big bearing should be a 6812-2RS (60mm inside diameter, 78mm outside diameter and 10mm wide), and the small bearing should be a 6202-2RS (15mm inside diameter, 35mm outside diameter and 11mm wide)
But I suggest that you measure your bearings to confirm these sizes are correct before purchasing new ones.

Please let us know how it goes.

Alan
 

[Pramot]

Thank you very much Alan for your quick and highly detailed reply. I will try.
Before I decided to buy Smart Pie 4, I saw this forum, I thought I would need help from here someday

[Pramot]

I successfully repaired it finally.
After I replaced new bearing, then I tested the motor, the wheel can't spin when pushing throttle and hard to spin by hand, much resistance.
https://youtu.be/zbL8XV7fcys
I checked and found that all three hall sensors were broken. I thought that metal pieces from broken bearing might cause this.
I checked three phase wires, all shorted together because many stator plates bent and stator plate edges crashed copper coils. I bent it back to normal.
After three hall sensor replacement, Smart Pie works great again.
Thanks Alan. I can't repair without your help.

[Bikemad]

I'm puzzled as to why the Hall Sensors all failed, but I'm pleased that you have been able to fix everything and get your bike back in action again.



Well done!

Alan