[gwatton]

Drive Trains can be broken down into the parts they include (excluding crab drive):

Motors: There are not too many choices for drive motors in FIRST. Most teams use 2-4 CIM motors for drive, depending on the weight available, and the power needed. Some teams will supplement with geared fisher-price motors. If you are going with a tank-drive style, two CIM motors per side is usually the way to go if you have the weight for it.

Gearboxes: FIRST supplied the AndyMark toughbox gearboxes in the kit this year. These will accept one or two motors stock, and are simple and easy to use. One thing that these don't provide that many teams desire is more than one speed. To achieve this, you can either go with a prebuilt shifting gearbox, such as those manufactured by AndyMark, or a custom design. AndyMark makes the supershifter model, which can be operated with servos or pneumatic pistons. This is a simple option, but somewhat expensive ($360 each plus pneumatics)Other options are available for single speed, such as planetary gearboxes from banebots or andymark, but they are used much less for drive systems.

Wheel type/arrangement: As mentioned above, the 6 wheel drive with a center wheel offset is the most common system. This has worked extremely well for us, and for many other teams as well. This system is usually paired with a set of traction wheels, either bought or custom machined. One type that has been gaining popularity are the Mecanum wheels. These wheels enable the robot to travel in directions other than forward and backward, through strategically reversing rotation direction. One downside to these is they usually provide diminished traction. Omni wheels are also being used frequently. This would be used on a robot to improve the ease of turning. Like Mecanum wheels, these also provide less traction.

Drivers: The final part of the drive train is the driver. The driver is not what it is all about, but a poor one can make bad use of a great robot. A great drive cannot make a robot good, but a bad driver can sure make a drive train terrible.

We (973) have been using the six wheel drive, center wheel offset design for 4 years now, and it has worked it greatly to our advantage. We custom machine wheels. We have experimented with both one and two speed gearboxes, finally using the AndyMark Supershifters, with pneumatic shifting. We use two CIM motors per side.

-Gabriel