Finally: replace just the bent shaft, not the entire motor

If you're like me and crash a lot (I'm a terrible pilot), bent motor shafts are a weekly curse. There's no good way to straighten them, so I have to replace the entire motor. That's expensive, and requires a lot of soldering of wires and remounting motors. So good news: now you can just replace the bent part, leaving the rest of the motor soldered and in place! 3DR now sells just the outside enclosure and shaft of the common 3DR 850 motors. They're half the price of the full motor and will save you many minutes of soldering and reassembly time.

(Why not just sell the shaft? Because they're really tightly placed in the enclosures and need special tools to replace).

I've asked them to also see if they can source the aluminum collets that the props fit on. They're soft and also tend to bend and they're hard to find on their own. Stay tuned...

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Comment by Justin Stiltner on August 16, 2012 at 11:40pm

If you cut the shaft down shorter with a dremel tool and let the bottom of the collet touch the purple part of the motor the shaft is much harder to bend.

Comment by Rick F on August 17, 2012 at 2:53am

I was also breaking and bending a lot of motor shafts when I first starting flying my quad.  I ended up buying about a meter of 4mm ground and polished tool steel shafting (amazon).  I used a dremel tool to cut the shafts to length and mill a few flat spots on the shafts for the set screws.  I needed to reduce the diameter a very small amount to get them to fit the motors.  This is done by chucking the shaft into a drill and polishing the shaft using 320 grit emery paper.  You need to be carefull not to take off too much but at the price, about $0.50 per shaft a few mistakes don't cost much.

Comment by Christiaan van Vollenstee on August 17, 2012 at 3:00am

Hello, is there a how to guide on how to replace it safely.

Comment by Mike Thorlin on August 17, 2012 at 6:41am
I bent the shaft of a Detrum 810kV motor on my quad. I had decided to replace the motor but then, just for kicks, pulled the motor apart and attempted to straighten the shaft. I removed the shaft (tough to do, but i was able to push it out with a steel pindriver), then spent 30 mins with a hammer peening the shaft while rolling it on top of a flat surface on my rather large bench vise. Surprisingly, I was able to straighten the shaft to a point that there was no discernable wobble. The quad flew great the next day. No guarantees, but it's possible...
Comment by kolin on August 17, 2012 at 8:27am

I replace shafts with help of big bench drill. First I fit anything smaller than shaft itself (nail without head) into spindle. Then I put rotor bell onto drill's flat table surface while shaft is in middle hole. Then I push shaft out of rotor by turning lever. Then I put new shaft  into spindle ant push it to the bell.

Problem is when you bent shaft, you damage bearings and may also bent bell itself.

I'm starting to thing about geared drive. You will not damage motor or it's bearing on crash... But the noise and efficiency drop...

Comment by Wayne Dancer on August 17, 2012 at 11:33am

I do this to my GWS brushless motors all the time.  The replacement shaft comes with the hex key you need to replace them.  I have a large Thunder Power brushless I am having a hard time finding a replacement shaft and I will need to get a snap ring pliers to replace it once I find one.

3D Robotics
Comment by Alan Sanchez on August 17, 2012 at 12:09pm

@cvanvollenstee  its really easy to replace these. You just push the black clip off with something flat. I use a knife to push on both of the legs at the same time but really anything flat will work. Once the clip is off just remove the old housing and replace with a new one and put the clip back on.

Comment by Andras Schaffer on August 17, 2012 at 1:45pm
But if you crash and bend the shaft, it's almost sure that you have to replace the bearings too.
If somebody bending shafts weekly, then why not buy an arbor press for 30 bucks and replacement shafts for .99 per piece....

Comment by Rory Paul on August 17, 2012 at 1:48pm

The best way to get motor shafts out and back in s using a "arbor press" and a steel punch. You can get these at Harbor Freight for about $40. There is a definite method to centering and seating a shaft. You need to make sure that you use machine oil and rotate the motor housing on a rubber pad as you press down or you can scrape the casing and the shaft will never be straight. You can also use the press to extract and push back in bearings.


Comment by Jack Crossfire on August 17, 2012 at 1:59pm

Engineers with BSEE degrees, flight software, electronics design: free

Motor shaft: $50,000


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