Pinion trouble

[LesD]

I’ve got a car where the pinion is spinning on the motor shaft.

I can buy a new motor with a pinion already on or can I just replace the pinion?

I note Scalextric sell black or white pinions, are they different? If so presumably by the number of teeth? The black is shown as 11 teeth. No specifications for white.

But can I use a pinion off another motor? Or are they once only push fit?

[Andy P.]

Hi LesD.

On standard Hornby Scalextric cars the number of teeth only vary if the motor various. If you have the rounder "can" motor also known as 13D or Mabuchi then the number of teeth will be same regardless of color. If the motor is the thinner version used in motorcycles and the Ford GTE then it might be different.

Inspect the existing pinion carefully. If it is cracked then it should be replaced. If it is not cracked it is likely that simply the tolerances are unfortunate i.e. you got a pinion with too big a hole and a shaft that is too small. For the latter a dab of superglue should work. Before doing that please read on though:

There are special pinion removing tools available. They are used heavily in model railroading and RC (radio controlled) spaces so finding them used is not difficult. You can remove and replace a pinion using a standard vice though. You have to be very careful and there is a chance the pinion sets at an angle and will not work well.

To remover a pinion in a vice place the motor in the vice and using a two thin rods (chopsticks are actually perfect) slowly and gently pry the pinion off by levering it off from the motor side. I used to rotate the rod 90° every millimeter or so.

When it is off clean the shaft with isopropyl alcohol and put a few drops in the hole of the pinion. Let it dry thoroughly. 

Some put the motor in the freezer to make the shaft shrink but I never bothered. 😄 

Putting the pinion back on has to go fairly quickly. I actually have tweezers that I can set the level of grip (i.e. I can put something in them and it holds it without my applying pressure with my fingers).  I place the pinion in the tweezers and then use rubber bands to hold the motor in the vice. I put a small dab of superglue on the end of the shaft, place the pinion as level as possible and slowly close the vice on the pinion. I release the tweezers and then push the pinion home using the vice.

It can be a bit fiddly and it a lot easier if someone else holds the motor in the vice. Rubber bands and maybe magnets can be used...

Good luck!

Let the superglue dry and see if it has helped...

[LesD]

Thanks Andy, a very comprehensive and detailed reply. 
I’ve tried the superglue route first and at first try it may have worked. 
I found that the pinion only started to slip after a bit of running.