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HOWTO disassemble a brushless outrunner motor

Shortly after the ER16/11 Collet-Chucks for PicoCNC spindle arrived, the brushless outrunner motors for this project followed suit. After closer inspection, both motors appear to be as equal as their datasheets suggested so the first prototype will be assembled with the brandless 50EUR C5045 890KV brushless outrunner (the red/black one on the right).

In order to progress picoCNC - A modular fabrication robot we have to replace the original shaft with the new collet. But how do you take it apart without special tools? The following 7-step HOWTO will guide you through the simple dis-assembly process:

There seem to be several ways to separate the parts of brushless motors:

  • Use special tools to safely remove the bell and shaft
  • Press the shaft out with a bench vise
  • Use a hot-air gun and a hammer
  • Use only a hammer

In this case, no special tools were available, neither was a bench vise. The hot-air gun method was postponed (and not necessary after all) due to the fact, that neodymium magnets demagnetize at a certain temperature. The magnets used in these brushless outrunners should be able to withstand a temperature of 100°C, since this temperature might occur in normal operation but, you never know.

However, for this HOWTO, you will only need a hammer. And some hacker creativitiy.

Step 1: Preparations

  • Remove the shaft retainer/circlip and the brass ring from the shaft with pliers.
  • Use some of the accessories of the motor to get a stable handle
  • Find something stable to elevate the motor to make room for the bell

Step 2: Go find a tool

  • Look for something that is far less dense than steel but still stable enough to transfer the energy from your hammer into the shaft, preferrably without the tendency to splinter. Wood is generally a good choice.
  • Place it above the shaft and hold it down with one hand.

Step 3: Push the shaft

  • Use your hammer with the other hand and give it one or more gentle taps until the bell drops to the bottom
  • If the bell doesn't move, tap it a bit harder until it does :)

Step 4: Remove the bell

Never underestimate the force of these magnets. At this point and again, when you re-assemble the motor, the bell might easily snap back into its original position by itself if you let it slide too far up again. So please, take special care when executing the next step, because it will hurt, if a part of your skin is getting wedged in between the bell and the base, when they slam home.

  • Hold the base steady in one hand and gently remove the bell and the shaft in a downward direction with your other hand

Step 5: Have a break and enjoy your work

If you feel up for it again, go to the next step to finally remove the shaft from the bell.

Step 6: Remove the bell screw

  • Use a hex bit to remove the screw

Step 7: Go find a tool

  • In this case you need something that is smaller in diameter than the shaft but basically has the same requirements as step 2: Less dense than steel, can transfer energy without braking/splintering. The only thing available here, were a pair of re-usable! wooden chopsticks, which worked very well
  • Place the food end of the chopstick at the center of the shaft and gently tap on the top with the hammer until the shaft is driven out.

Finally

Well, who knew, that chopsticks can be used to dis-assemble a brushless outrunnner motor? And please, be so kind and let others know how and if it worked for you. Leave a comment, share your experience.

Personal Mission-Log Addendum

I would have loved to make a video for this HOWTO since it makes things much more easy to grasp and leaves less room for interpretation. However, shooting and editing takes considerably more time and resources, which I don't have at the moment, due to my full-time job. I really would like to get back to the state where Apollo-NG is my full-time job, but that can only happen if the Odyssey and Aquarius are finally on the road, fulfilling their mission. If you'd like to see more content and videos, please consider helping the cause.

Mission-Log entry created by chrono on 2012/07/17 21:40 UTC

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