Building Tip: Working with Gears

Gears are essential part of robots and machines. I've seen many brilliant NXT projects that don't work well because of the gears. When we're working with gears, we need to ask us: what do I need, torque or speed?. If you're making a race car you need speed, but if you're making a heavy truck that can transport a lot of heavy stuff you need torque. We can achieve that playing with the sizes of the gears. If you conect a big gear with a small one, every time that the big gear rotates 360° the small will rotate a lot more, so it will be spinning faster (but will less torque). Look this:

The wheel is spinning much faster than the motor, but with less torque

The contrary case:

The wheel is spinning with less speed than the motor, but with more torque

Remember the heavy truck? Well this super slow truck should look like this inside:

Super slow and lot of torque

What if you need torque and speed? Well, you need a transmission box, like in a real car. When you are in first gear you have a lot of torque, in the second one you have more speed but less torque and so on... A transmission box changes the position of the gears to transmit with speed or torque.
Hey! I know that you wanna build a transmission box right now! Here are some great examples of transmissions box built with Lego Mindstorms.