Slope of ramp

[sanddrag]

Getting up the ramp easily is certainly not something every robot can do. If you have 4 wheels, you'll need some center clearance. If you have six wheels, you may not. 30 degrees is steep too, so tipping over is concerned. You may want a long robot so you won't tip over, however it will be more difficult to turn.

For approach and departure angles, you can make your wheels the frontmost and backmost thing on your robot so there is no frame to hit the ramp before the wheels do. However you may start riding up on the balls.

It is all about tradeoffs.