Extension lift mechanics

[ChrisH]

Originally Posted by Vash

Okay I guess I overdid it. From past experience members of our team insist on never trusting gravity.

Gravity is generally pretty reliable, but in this application you need to ensure that it is able to do it's thing. The key thing is to make sure that the sliding sections cannot tilt sideways enough to lock up. Gravity can only pull so hard, if it takes too much force to clear the jam then you will be stuck in the up position. If you want the belt and suspenders approach then you ensure that you pull down as well.

Our lifts have always been powered both ways. Keeping the lift from jamming up was one reason. But another is that gravity is not always pointing the same direction relative to the robot.

If, for example, your robot should fall over sidways with its lift extended then gravity is now pulling 90 degrees from the direction you originally intended. Your robot is now blocking a large part of the field, a situation which may not be desireable. If you power the lift down, then you can probably retract it and clear the field. It would also be easier for another robot to help you back up on your wheels. But if you are relying on gravity to lower the lift, then it is already as low as it will go.