Why doesn't it ride?

Why doesn't this work? The motor turns when i unhook the wheel, if the wheel is on the ground, it doesn't ride/spin. http://imgur.com/oFJpax0,CWJOxV1#1 (2 images)

The torque requirement placed upon the motor when in the running (loaded) position is greater than the torque supply capability of the motor or the supply source.

Try measuring the voltage across the motor terminals when free running and when loaded. If it falls when loaded then the source is incapable of supplying the demand; if it remains fairly constant then the motor is incapable of meeting the demand.

And if you don't have a test meter then go out and buy the cheapest you can find - you will find it extremely useful in solving similar problems. A test meter should be part of everyone's hobby kit.

Picking a motor and/or gearing system is all about torque and speed - find out the ratings of a motor before buying it, calculate or measure your torque requirement (its simple mechanics) if you want to avoid guesswork. Don't forget friction!

What are you using to supply power to the motor. Tom

I do not see a gear box in the image. To get any useful torque out of a simple DC motor you must have a gear reduction from 50 to 300x.