The toy you are originally starting from comes with some method to control the motor, often through a foot pedal switch that activates the motor directly or through a relay. The motor is either on or off. Besides optional “fast” and “slow” modes, there is no way to vary the speed of the motor on the original toy. Except for the switch or relay failing, this setup is generally pretty reliable for the tiny stock motors.

Assuming you are going to replace the motor with something more powerful, and (optionally) would like more granular control over the motor's speed, you will need to find a suitable motor controller to match your chosen motor. Depending on your setup, the motor controller can be a significant part of your budget.

There are generally two types of motor controllers, which must match your type of motor:

• Brushless
• Brushed

http://en.wikipedia.org/wiki/Electronic_speed_control Wikipedia has more information on the topic of speed controls.

…and your options for obtaining your speed control are:

• New - lower power controllers can be had for cheap; high powered get very expensive very fast
• Used - Often a good choice for higher power controllers, if you can find a deal
• Build-your-own - Can be very inexpensive, but obviously much more expensive.

If you are using a forklift motor, it may have come with a controller. You could always use that.

Alex from Sector67 designed the Paragon for Fauxrarri, and at some point, will be selling them, but no one knows when.

Phantom Power Racing developed their own controller using an FPGA thingy, and it's impressed a few people. No details are available yet.

You can try using a electric scooter controller. They are usually from China. They usually break.

• Paragon from Sector67
• TNC Scooters