How to Change the Drive Shaft on Your Quadcopter RC Motor

This instructable is how to change the supplied drive shaft on a 3DRobotics supplied 850Kv motor to a new shorter one and a new prop adapter. The procedure is fairly simple if you have the right mechanic tools. They are easily sourced from your local hardware or automotive supply store and are not expensive.

(This same Instructable can be used to change the drive shaft of any radio control outrunner motor used in model rc planes)

What you will need

1. New replacement motor shafts

What tools you will need. (excluding screwdriver or other tools to take the motor off it's mount)

1. A 1/4" pin punch (or a punch larger than the diameter of the shaft)
2. A 1/8" pin punch
3. 16oz Hammer
4. An old 4"x2" piece of wood
5. Small right angled needle nose pliers (or equivalent)
6. Blue (medium hold) thread locker.
7. 1.5mm Hex wrench
8. Drill
9. Drill bit that is slightly larger that the shaft diameter. (I used 5/32")

Step 1: Unscrew the motor from the Quadcopters arm/mount.
This should be an easy step and it's not documented here. Variations will depend on airframe.

Step 2: Remove the circlip that holds the motor shaft.
You can do this using the small needle nose pliers. Be careful as it's likely to ping off into the distance.

Step 3: Pull the motor housing from the motor.
This can actually be quite hard, do not to use the wires to pull it apart. I found one motor unwilling to let the housing go free, so i reattached the motor to the quad arm and then easily pulled it free.

Step 4: Loosen the grub screw with the 1.5mm hex wrench that adds extra hold on the shaft

Step 1: Replacing the Drive Shaft

Step 1: Drill a hole in the 4"x2" scrap wood.

Step 2: Place the motor with shaft in the hole.

Pro Tip: If your punches have paint on the ends, file it off or scrap it off against an old concrete wall/block. The paint is slippery. It's much better for the ball of the hammer to hit clean metal. This means it will make better contact and not slip off.

NOTE: Do not hit the motor shaft directly with the hammer. This can cause it to distort and weaken. You must use the punch.

Step 3: Take the 1/4" punch and gently but firmly tap the motor shaft to be flush with the housing.

Step 4: Take the 1/8" punch and gently but firmly knock the shaft out from the housing. After each hit reposition the punch to be centre on the drive shaft. Don't hit it repetitivly like hitting a nail, be precise as to not damage the wall of the hole in the motor housing. This type of fitting is known as a friction fit, so any damage to the inner wall of the hole will reduce the hold.

Ta da: the shaft should be free!

Step 2: Insert New Shaft

Time to insert the new shaft, rotate the motor housing 180 degrees the other way up (see pic)

NOTE: Make sure the recess for the circlip is  at the top, (see pic!)

Step 1: Place the new shaft in the motor housing with the recess at the top.
Place the oversize 1/4" punch on the shaft. Now for the next gew taps, just lightly does it. This will centre the shaft in the hole and not damage the housing.

Step 2:  Tap, using the punch, the shaft until it is flush with the outside of the housing.
If the shaft goes to far, invert the motor housing and tap lightly with the 1/4" punch to align it.

NOTE: Do not hit the motor shaft with hammer. This can cause it to distort and weaken. You must use a punch.

Step 3: Re-insert Motor Housing and Circlip

Now we have the new shaft in place

Step 1: tighten the grub screw after placing a drop of blue thread locker on it. (I would recommend blue threadlocker on all screws!)

Step 2: Place the motor housing on the motor

Step 3: Replace the circlip using the long nose pliers

Step 4: Remount Motor and Add New Prop Adapter

The final steps are 

Step 1: Remount motor on multi rotor frame (use threadlocker on screws)

Step 2: Mount new prop-adapter (again use threadlocker on screws)

Step 3: Attach props and have fun ;-)

I hope this instructable has been useful. This task is an easy one when you know how. Please leave comments I am more that happy to update it with real world experience on what went right (and hopefully nothing went wrong)