The shaft can be used for a flywheel, but if you want to shorten it, that's ok but it's hard so make sure you have something to use on it. A Dremel type tool with appropriate cutting disc should do it.

 

Technique matters to avoid any risk of damaging the motor - and yourself.
Eye protection!
Secure motor body and clamp motor shaft so that it cannot turn during cutting.
Run cutting disc at maximum rated speed, make the cut quickly to avoid heat build up.
If heat sinking can be neatly arranged on the shaft near the cut point then do so - a little water where the heat sink contacts the shaft is effective.
Eye protection!

This may seem a little OTT, and for the larger motors where the bearing is a good size one can be a little more casual in all matters except eye protection. But it is so often with smaller motors going into models with restricted space, that leads to a need to remove the redundant shaft; and these are more readily damaged if the cutting is protracted and generates a lot of heat.

 

Excellent, and just what I needed to know.Thanks very much.I am building a caley class 104 from caley coaches ltd and shortening the motor driveshaft should make all the difference esp when I need to find room for a decoder, preferably stay alive, as well.

Donald.

 

It's very important to make sure that the adjacent motor bearing is well protected during cutting so that ferrous particles are not drawn into it by the motor's magnetic field. Masking tape or plasticene will work for this. I learned that lesson the hard way, many years ago on a very expensive piece of aircraft equipment. Also, be careful not to apply too much radial force to the motor while you are cutting. If you use a saw, it's better to hold the shaft in a vice and support the motor body with the free hand.

andrew

 

Thanks Andrew,I didn't know that. Another question .......Does anyone know if there is any reason for not using a tsc KAT 12 decoder with a mashima 10 or 16 series motor ? Do some decoders lack the punch to run some motors?
Thanks.