Why is swerve so slow?

[AdamHeard]

List of reasons swerve is "slower" than a traditional skid steer. Reasons may not be valid for all swerve variants.

-Likely has more stages of power transmission, and if using bevel gears has more inefficient power transmission. A good skid-steer is typically 2-3 stages of decent spur gears. A swerve could be 3-4 stages easy. Motor in module variants are an exception. This changes a drive efficiency from a possibly 90% to maybe around 70% (made up numbers!)

-For the same reasons as above, there is likely more rotating mass (inertia) in the drive to accelerate, this could easily be a few percentage points slowdown.

-Steering error. The odds of all your modules pointing perfect is low, there are likely appreciable losses due to friction here.

-Steering time. It takes time to steer the modules to where they want to go, and teams have different methods for dealing with this. Some assume it's instantaneous as they gear it fast, but this leads to a lot of the above error on the way there, which wastes battery and heats the motors more. Some teams turn power down until wheels are pointing where they want to go, and this also obviously adds a delay as the drive must wait before it starts really going.

-Weight Transfer. Depending on the exact gearing, CG, overall robot geometry, tread, etc... it's possible that during initial acceleration enough weight is transferred such that half your wheels are now breaking traction. Even if this happened for .1-.2 s it would appreciably slow you down. This is only valid for independently powered modules.

-Driving style/Control Scheme. Except for 16, most famous swerves have been driven by point to point drivers. As Tom pointed out top drivers on skid steer are forced to learn to carry their momentum to be quick. Many swerves don't do this. If we swerve again, we will spend time looking at this.

There are more reasons, and if I think of them I'll edit and add them.

None of the above are huge, but a few small things could easily add up to make something seem/feel a bit slower. Maybe if I get a good block of time I'll model the above and see if I can point out a difference.