This is a theory I’ve had about x-drives:
When comparing two robots, one with an x-drive and another with a standard drive, that have the same effective gearing when moving forwards (for example, a 2.75 inch wheel x-drive against a 4-inch tank drive), the x-drive would strain the motors less in a competition setting because it gets twice the amount of turning torque in comparison to the tank drive.
I thought this might be plausible after seeing very fast x-drive ratios difficult to achieve with a standard tank drive (from team 7682) and from personal experience, where I’ve noticed that overburdened drives struggled the most with turning.
What does the vex community think about this? Are x-drives superior to tank drives?
Because the wheels are on a 45 degree angle, the robot will move square root 2 (~1.4) times faster than with the same wheels in a normal setup. This means that the motors will strain more. However, because it gives you more speed, you can then use smaller wheels or lower gearing to get the same overall speed.
I like the x drive because it gives you manoeuvrability with strafing, and is also resistant to being pushed in all directions. A tank drive with all omnis should have no problem turning, but can be pushed sideways, so some teams add a third set of traction wheels in the middle.
Look at the “Direct Drive Ratios/Speeds” document on this page to see a comparison of the speed of various drive setups with different wheels and gearing.
This is not a mathematical answer, but I had a tank drive last year, and I built an X-Drive this year. Last year, I had a lighter robot, and had to play carefully so I didn’t trip the PTCs in the motors. This year, I have tried to trip the PTCs with a titan lift, and it takes much longer than with a tank drive. I also enjoy that I can strafe and move diagonally with an X-drive.