[Tom Line]

This is exactly why you need to play with your ratios and look at the time it takes to cover distances.

A top speed of 20 feet per second sounds great, but it will obviously take far too long to get to that speed 90% of the time. You'll be draining your battery because your motors will be working too hard. That's why shifting is needed to realistically attain that speed.

Of course, JVN made a very good point. We need far more information to quantify this for the OP.

Originally Posted by Levansic

What good is top speed, if the robot never achieves it?

I pose the question, because speed, traction, and acceleration are a balancing act, and too many people here throw around their theoretical peaks as facts. Thank you for being honest about your robot's actual performance.

Almost a decade ago, I was working on a collegiate team, making robot soccer players (kaliken from 294, also). These robots were small, but pretty fast. We had geared them with a 9:1 ratio, but never came close to hitting top speed on our field. We changed to a taller ratio (14:1), which should have dropped our top speed by about 35%. Instead, our acceleration greatly improved, as did our achieved top speed. Even better, our motors drew less current and ran cooler, which helped battery life in our 30 minute all-out matches. The drivetrain has to contend with the inertia of the robot, and this is missing from most back of envelope drive calcs.

Back in FIRST, I see too many rookie teams at competition, with low gear ratios, hoping for high speeds. Their robots barely move, and scrubbing in turns causes complete standstill. Many on this forum calculate theoretical speeds, and live with what they have committed themselves to. The best course, if possible, is to do your calculations, but make sure to test several ratios above and below. Pick the one that best suits your robot, and your team's strategy with the game.