Suitable motor?

A Dremel! It all depends on what you are trying to do! If you can give us something to play with then maybe we can suggest something else! Is it for rapid positioning? Does it need a feedback loop? Is it for a flail? Is it a secret that you are not allowed to tell?

I have a question for you! How do I change a tyre?

N0, I take it back to the shop!

Give us some more info!

Do you mean motor gearbox assembly or just a bare DC motor?
Is this a low power application? What load are you moving?

Do you want one offs or are you going to use a lot of 'em.

Look at Rotalink the make a nice range of cheapish low power motor gearbox assemblies

Del

Trident engineering do a good range of small motors & gearheads (some of their own, as well as being distributors for Portescap etc.).

As others have said - depends what you want - is it for a robot car crusher or a robot fly?

Most Robotic application that I have seen used steppers or servo type motors with or without encoders. These motors are for low torque high speed application and will require a dedicated controller.

If you are looking for a hobby source, you can recycle old cordless drills using the 12V batteries. Just ask around and you should find some. People usually discard them when the battery is too old because it is cheaper to buy a new one than to replace the battery. These drills come with a gearbox and usually have two speeds.

Where is krishna_phelu?

I would use a round one, versus a square one...