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Originally Posted by Billfred
I beg to differ. (snip) A little ground clearance never hurt anybody.
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I'll go farther and say a little ground clearance is essential. If you don't have any then you don't go anywhere. The question is not so much "how low can you go" but "how high is too high?"
I have done studies on the arm/base/object relationship. It seems that if you keep your combined weight of arm and object close to 25% of your total system weight (including object) and your base CG is within 1 ft of the ground then you will have a very hard time tipping. But once you pass the 25% threshold staying upright gets a lot harder.
The relative weights of the base, arm and object are more important than the absolute number. So if you have "extra" weight you want to make sure that anything you add goes into the base, to increase its fraction of the total weight.
Your base CG is probably lower than the top of your wheels and hence lower than 1 ft. There is no reason to work hard to get it lower than it is. There are plenty of reasons to leave it where it is.
First of all, the carpet is only as flat as the arena floor. Sometimes the floor is really flat, other times it is not. It would not surprise me to see bumps of 1/4" in a floor. If you should build your robot with only 1/8" ground clearance, then you would have a problem.
Second, there is always the possibility that your robot might get bumped so that one or more wheels get pushed into a goal. If you have really low ground clearance, then you could wind up high centered on the goal. With a couple of inches of clearance, this ceases to be an issue.
It is often easier to have your wheel axles go into your frame than to have the frame hanging from them.
There are probably other reasons I can't think of right now. Extra Ground Clearance only becomes a problem when there is too much. How much is too much? only you can decide