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Electric Conversions
› Motor shaft failures - please share your details
01-24-2010 04:04 PM  8 years agoPost 1


Richmond, VA, USA

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Hi guys,

I posted this on another forum as well in an attempt to get as much info as possible, so forgive me if you've seen it before and thanks if you've already replied.

I know the topic of shaft failures in TR700 conversions (and others) has been brought up before, and I also know that the gold standard remedy for the problem is a shaft support such as the one KDE has.

I have a particular application in this VPUS E3 that will not allow top shaft support. I'm asking this question here because T700 conversions and their owners offer the greatest knowledge base and data pool on this matter.

Thus, I have four questions:

1) Have you had a shaft failure on a model w/o shaft support?

2) What kind of motor was it?

3) Where on the motor shaft did the failure occur?

4) Approx. how many flights occurred before the shaft broke?

I would really appreciate you time in answering these questions. It'll help me a lot and hopefully others as well.

Thanks so much.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

01-28-2010 11:32 PM  8 years agoPost 2


Jakarta, Indonesia

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Dr Ben,
I have experienced the shaft failure on my E3. My answer to your queries as follows.

1. Yes, my model W/O shaft support.
2. Scorpion 4035-500 kV
3. Right at the place where the shaft reduce from 8mm to 6mm.
4. Mine broke only after 3 short hover (about 3 minutes).

Hope this helps.

INA 0083

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01-29-2010 01:30 AM  8 years agoPost 3

rrElite Veteran

Palm Beach, FL

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This is a simple issue.

Heavier heli = more pressure against the gears
More gear pressure = more pressure on shaft and bearing
Either the shaft breaks or you toast the motor.

Another issue typically with the conversion is there isnt much warning on pinion height. The higher the pinion the more torque against the shaft with the bearing as a pivot point.

If your not using a support you will be after you break the motor shaft which will happen...its just when.

BTW, no I have not broken a main shaft.


Xera Motors
Thunder Power

01-29-2010 08:03 AM  8 years agoPost 4


Dubai, UAE

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Trex700's layout alows to have much shorter arm of gears side force (shorter pinion) than hirobo layout does.
So imo trex owners experience is not so relevant.


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Electric Conversions
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