It is about time that I clarify some technical issues concerning the Bafang PMGR motor.
The ring gear in the hub appears strong and made of steel. ...
The rotor gear (sun gear) looks fairly robust as well (also made of steel). ...
(Edit 6/30/08) The planetary gear set (3 nylon planet gears) does not stay stationary during freewheel. It rotates along with the ring gear during freewheel.
Applying throttle causes the gear set to cease rotating within the motor as torque is applied to the wheel. The gear-set-freewheel-assembly is anchored to the axle by a key pin.
Above is the freewheel with the gears removed. The gear-set-freewheel-assembly can spin freely in one direction around the freewheel bearing.
The planet gears spin and translate (the gears move their location during freewheel and are staionary under applied rotor torque) all within the body of the motor.
The planet gears also have sealed bearings. The planet gears are held in place by those little clips. ...
Golly! What's wrong with this gear (actually it kinda looks like a sun god now ... 1960's hippie style)? This is what happens to the gear if the torque exceeds the yield strength of the nylon gears.
See explanation of why it failed here ... viewtopic.php?f=2&t=4282&p=73746#p73578
Clearly the nylon gears are a very WEAK LINK in this motor design.
But I am not ready to throw the baby out with the bath water quite just yet!
So I plan on fabricating stronger planetary gears at my local gear fabricator shop (we have them here in NY).
Some other interesting tidbits ...
1) There is definitely a freewheel! The rotor only spins when applying torque. The planet gears are either spinng against or rotating with the ring gear.
The wheel freewheel spins with very little " resistance in the forward direction.
2) The motor will NOT run in reverse (it only freewheels in one direction).
3) Shorting the three phase wires completely brakes the motor in reverse direction only.
4) This is a VERY POWERFUL MOTOR! It has no problems at 72V and 30-amps.
The nylon gears will turn to "peanut butter" if you brake the wheel and accelerate the throttle at the same time. E BRAKES ARE ESSENTIAL!
SOLUTION: Simply add one steel gear (or maybe an alloy gear) to the planetary gear set. This is exactly what Keywin and I are planning to do.
BTW ... I am buying plenty of replacement nylon gears too (for sale of course) to all the good planetary folks just in case replacements are needed.
But I just can't wait to get my new MEGA SUPER GEARS fabricated and installed so I can SHRED UP the road with this tiny yet powerful motor!
On a final note ... Just so that we are all on the same page ... My Grubee black motor on my chopper ...
(see ... viewtopic.php?f=6&t=4160#p62316
... is still more powerful (faster) than the Bafang (same V and amps) regardless of the Bafang gear material.
But the Bafang PMGR is infinitely superior at slower speed with UNSTOPPABLE torque output.
PS I will have the rear Bafang motor soon ... and put to rest once and for all ... the issue of whether this motor will fit into a rear bicycle drop-out.
Just came in.