# How much weight can a 4 motor HS drive carry?

What’s the maximum amount of weight I can get away with on a 4 motor HS drive on 4 inch wheels without the drive burning out or wrecking motors?

It depends how you drive and what you carry, and of course the type of drive. X-drive will burn out on anything more than 10 pounds, I would guesstimate. I had a 4 motor HS drop center drive last season and it was a 15-pound robot. We didn’t really have much of an issue with burning out, even when turning with objects, but it was fairly close.

18.45 pounds of robot and game object.

(4 motors) x (14.76 in.lbs)
------------------------------------- = 18.45 pounds
(2 in wheel radius) x (1.6 gear ratio)

*in perfect conditions

No. This is a calculation that works really well. Your starstruck robot was 15 pounds and could dump around eight stars, which is 4 pounds more, around 19 pounds. The reason is the drive doesnt lift all 19 pounds. It just moves it with no change in potential energy, so no actual work. So this calculation actually produces good results for real robots in non-perfect conditions.

Right, but friction will always play a part… Hopefully as small as possible.

Friction is accounted for. Test out this formula with some ratios you have used in the past. It is produces reasonable results.

Okay, so the formula assumes minimal friction then, probably what you or I would have. Just a reminder to all new teams to make sure to cut down on friction as much as possible. As I told our new members, make sure the wheels spin for at least 10 or so seconds freely when you put them on.

Part of it will also depend on the weight distribution. A very front heavy robot will put extra strain on the front wheels unless you chain the drive motors together. But yes, 18 lbs is reasonable.