I could really use some help here... I realize I made a few mistakes.

1. I got a 2.8:1 gearbox for my Graupner Speed 600 motor. The instructions say that the distance from the front motor casing to the top of the pinion needs to be 12mm. This means cutting the shaft. Any advice on how/what to cut that shaft with?

2. The pinion I received with the gearbox was a 'press fit' pinion. I tried installing in on the shaft with a small rubber hammer. Long story short.. after a lot of 'tapping' I ended up pushing the back of the motor out of the casing. I managed to re-assemble the motor but I worry that I have somehow damaged it now. Any thoughts on this?

3. HOW does one get a pinion on to the shaft? Is there a special tool to buy?

Thanks for the help!

1. I got a 2.8:1 gearbox for my Graupner Speed 600 motor. The instructions say that the distance from the front motor casing to the top of the pinion needs to be 12mm. This means cutting the shaft. Any advice on how/what to cut that shaft with?

Dremel. Otherwise, a hacksaw and file will do in a pinch.

2. The pinion I received with the gearbox was a 'press fit' pinion. I tried installing in on the shaft with a small rubber hammer. Long story short.. after a lot of 'tapping' I ended up pushing the back of the motor out of the casing. I managed to re-assemble the motor but I worry that I have somehow damaged it now. Any thoughts on this?

Support the back end of the motor shaft and tap it on with a brass hammer. If you have access to a drill press, you could use that in place of a bearing press again supporting the back end of the shaft. I doubt you've done much, if any, damage. Check for any fore and aft movement in the armature and correct it if there is.

3. HOW does one get a pinion on to the shaft? Is there a special tool to buy?

See answer in #2.

Hope this helps!

mw

Thanks Mark! I will try your suggestions!

1. I got a 2.8:1 gearbox for my Graupner Speed 600 motor. The instructions say that the distance from the front motor casing to the top of the pinion needs to be 12mm. This means cutting the shaft. Any advice on how/what to cut that shaft with?

A Dremel tool. If you live in the USA, you can buy a cheap Dremel knockoff in WalMart for $20. You will also need a cutoff wheel and mandrel. A hacksaw will work in a pinch.

2. The pinion I received with the gearbox was a 'press fit' pinion. I tried installing in on the shaft with a small rubber hammer. Long story short.. after a lot of 'tapping' I ended up pushing the back of the motor out of the casing. I managed to re-assemble the motor but I worry that I have somehow damaged it now. Any thoughts on this?

Your problem is that you weren't supporting the shaft of the motor when you started tapping on it with a hammer. The motor case is not designed to handle such stress.

3. HOW does one get a pinion on to the shaft? Is there a special tool to buy?

Here's how I do it:
1. Put the pinion gear down on a block of wood.
2. Line up the motor shaft with the hole in the pinion gear.
3. Using a nail set (or any suitable steel punch/pin) and a small hammer, tap on the short nub of shaft that extends from the rear of the motor, and drive the motor shaft into the pinion.

If you have to cut the shaft, you should sand or file a small chamfer on it so that it will center properly -- makes it a lot easier to press fit the pinion.

Joe