2-Speed vs 1-Speed drivetrain

[BJC]

Originally Posted by DampRobot

The correct answer is "nothing, really", but the real answer is that it is because of the way people like to gear single speed drivetrains. In my mind, having a low traction limited gear "lets" you gear your top gear really fast, like 16+ fps. If you're doing a single speed drivetrain, you're likely going to gear less aggressively, as you likely don't want to be stuck playing defense with a robot geared at 19 fps. Some teams like to gear their single speeds in the 12 fps range, which do accelerate faster than the 18+ fps two speed teams.

Of course, a lot of it depends on how you like your drivetrains, here on the West Coast most good teams just gear in the 16+ fps range no matter if they're single speed or shifter. And a lot of butterflyesque drives (33, 2K14 drive in a day for example) are geared in the 18 fps range so they can do the reduction to their wheels in only one ratio.

33 is geared 12:72 - about 14fps real.

When you people talk about drivetrain speeds would you all mind mentioning if you are talking theoretical or after efficiency losses(and at what efficiency)? IE: In my experience a robot's geared for 16fps theoretical is around 14.5fps real.

In general, I don't understand gearing above 15fps real with a full weight robot. The optimal time to distance numbers get over a half field away and the robot gets slower overall. Of course, if the robot is lighter than 120lbs teams can get away with a higher gearing while maintaining a similar acceleration. This is the real trick to getting around the field faster.

Cheers, Bryan

[themccannman]

They don't.

Assuming they're under identical conditions acceleration rate is dictated by gear ratio. Lower gear ratio = faster acceleration, higher gear ratio = slower acceleration. A single speed drivetrain does accelerate faster, a lower gearing does.