Swerve Drive: Pros and Cons?

A robot that is spectacularly manoeuvrable and cannot score well will still be sent to play defense if it gets picked.

This reminds me of something that I wanted to bring up. I’ve had a few people tell me that swerve is inherently bad for defense. Even including one team who’s robot was swerve drive.

I’m not sure why this would be. Perhaps it is because swerve drives are often geared pretty aggressively such that they don’t have the highest pushing power, but there is no fundamental reason why swerves would be any worse at defense than a typical drive train. In fact the ability to move any direction without needing to reorient can be an advantage while playing defense.

1 Like

For reasons that I won’t get into, we went to one of our off-season events with nothing more than a swerve drivebase (with some extra ballast added) and therefore could only play defense. It proved to be an excellent defense configuration. The nimbleness of the drivebase in terms of being able to drive in any direction at any time allowed us to easily get between scoring robots and the scoring locations and then stay between them as they tried to get around us. And I can tell you that we were very successful at pushing back on teams that tried to push through us. And many times we were able to knock scoring elements (hatches or cargo) out of other robots through “aggressive” bumper to bumper contact.

We were geared for speed (6:1 to 4" wheels from NEOs), but were still able to push around other robots. There were several times where we pushed other robots sideways where their drive wheels were skidding sideways on the carpet and really had no issue with power to push them. it may have been all that pushing power we put in the power cube that was bolted to our frame…

3 Likes

That may have been our team that said we couldn’t play defense with a swerve drive. We were really pleasantly surprised how well playing defense with swerve worked.

We switched to 2910s swerve this year and we really loved it. It gave us some flexibility in design since we could put mechanisms on all 4 sides of the robot. We had some fantastic software kids that made the switch easier.

Watch the lower left display at 6:32 and 6:55 to see how playing defense against a swerve can be problematic.

JMH

2 Likes

I don’t doubt that a well driven swerve robot can be very effective at defense. It appears that most teams wanting to use swerve are wanting to improve their scoring ability. Only directing extra resources to a drive base will not improve lackluster scoring mechanisms.

Your speed also contributes to your effectiveness in defense. If I recall my physics classes correctly, kinetic energy = (M * V^2)/2. It is the jolt your robot imparts that causes your opponents to lose their game pieces. A robot that only pushes would not have the same effect.

You remember your physics correctly. Perfectly elastic collisions will conserve energy (imparted from one robot to the other). However, FRC collisions are generally closer to inelastic collisions which conserve momentum rather than conserving energy. Momentum is M*V. V is still a big player. So is M. I guess the 60 lbs of CIM motors that we put in the power cube to get the robot weight up to 125 lbs helped a bit, eh?

1 Like

A friend’s robot weighed only around 70 pounds without bumpers and battery. It had 4 775’ per side and was extremely fast. Occasionally, between scoring cycles, they would play defense and give an opponent a single, sledgehammer hit. Often, those single hits would cause the opponent to lose their game piece like you were able to. They would then go back to cycling game pieces.

WELLLLL if you want to make this argument… Take 1323, for example. They used a COTS (or soon to be?) drive and implemented a much simpler (compared to turret) swerve and got farther than 254 at Houston Champs. 1323’s focus on making sure they could evade defense rather than just being able to drive forward and backward was arguably a better strategy than the rather short-term approach 254 took that got them to einstein finals. :smile:

11 Likes