SmartPie cooling fan housing disintegrates!

[Wombat]

Has anybody else experienced this...

Pic shows all that remains of my SmartPie cooling fan / disk brake mount.

After only 20-30km use the rear disk brake mount come cooling fins block spat the dummy big time when brakes were applied (to slow, not stop) while not traveling very fast at all.

On a busy road these are all the bits I could find. Note the brake disk mount screws were still tight with the ring normally enclosed in the fan housing still intact... just all else of the "cast" aluminum fan housing shattered and went woy woy.

Fortunately out of the bad was a good thing; the brake disk remained hooked in the brake caliper and didn't flap around causing all sorts of additional grief.

Also note all the five fan housing bolts (bottom of pic) holding the fan housing to the motor remained in place too.

PS D**n just had a careful look at the disk rotor and it's stuffed with a twist in it too... brand new$$$$

[Bikemad]

Ouch, that's definitely not a pretty sight, it's just as well it was the rear brake and not the front!

I can see two possible reasons for this particular failure:

1) A flaw or defect in the alloy casting
 or
2) An inherent structural weakness in the design

There must be thousands of Smart Pies in use and this is the first failure of this component that I have come across, so I would say the failure was most likely the result of a poor casting rather than a weak design.

Wombat, can give a rough estimate of what the combined weight of rider, bike, battery and luggage etc. was likely to have been at the time of failure? Also, were you slowing down on the flat or going down a steep hill?

Was your rear disc brake very fierce and prone to locking up the wheel?

Alan
 

[Wombat]

A heavy "mountain" bike but not uncommon (ie built like proverbial brick sh*t-house).

Me (109kg/240.3lb).
Bike mit motor (21.4kg/47.18lb).
Battery (4.6kg/10.14lb)
All up (135kg/297.6lb)... revised "last edit"

Disk brakes el cheapo manual actuators, NOT hydraulic.

Original rear brake without electrics couldn't ever alone cause skid stop.
New brake disk ($AUD49) noticeably less efficient.
So have never been able to lockup rear wheel.

New brake disk with GM REGEN braking very good requiring little handle pressure. Had regen set to about 75% I think.

Have never needed to overuse rear brake as it is only ever used to support primary braking at front with drag.

Not traveling fast and no need to actually stop, incident happened on slight DEcline slowing to prepare to turn right (we drive on left hand) in to an Aldi store (to buy cheap bike bloody repair stand would you believe!). At least stand worked a treat when removing disk etc.