Hi guys

I want to start experimenting with motors and gears. (Small scale.
Maybe half tbe size of my old RC car motor or smaller) Unfortunately I
live on a small island :-) and I think I may find it difficult to get
the parts.

I understand that I need a motor with a pinion gear and then other
gears. Unfortunately it seems like my favourite webmarts don't stock
these together:
www.radionics.ie
www.maplin.co.uk

They almost always have motors WITHOUT pinion. And they don't seem to
stock pinions on their own. This results in a few questions...

Where can I buy pinions? How do I know it will fit on my motor? I
remember from my RC days that the pinion had a little screw to fix it
to the axle. Is that what I should look for? Or should I just get a
pinion that fits very tight on the axle of the motor?

Why on so many technical diagrams don't they show you the diameter of
the hole through the gear? I can only guess that it's a thrid of the
hub but I would have thought that that would be an important property
to document.

I did notice that when searching for gears these webistes show
something that looks like a motor with a gearbox added to it but even
then it didn't have a pinion.

I must be missing something. Please enlighten me, and for a bonus
point, I'll be VERY grateful is someone can show me these parts on the
websites I mentioned.

Thanks!