Supershifters and Mechanum wheels

[Tom Ore]

We now have 7 regional wins on mecanum wheels so count me in the "likes them" column.

[J_Miles]

Perhaps I'm simply biased, but as a driver I loved driving a robot with mecanum wheels. Our 2011 robot was built on a mecanum drive and won the 2011 Ann Arbor District competition, the 2011 Troy district competition, as well as two local off-season competitions in Michigan. It was definitely a machine to be reckoned with in spite of what many would consider to be a poor choice of drive train.

With that said, there are a few advantages to mecanum drives, but I think they're quite context-based. 2011 seemed to be an excellent year (if there is such a thing) to use the system because of: A) The totally flat field, B) Sizable protected scoring zones C) A shallow protected zone (making the ability to strafe quite useful). For this reason an omnidirectional drivetrain seemed the way to go, but we chose a mecanum drive for its relative simplicity and our previous experience with it, and our year was spectacular because we were able to put lots of effort into our end-effector and other mechanisms besides the drive, and to build a solid mecanum drive there isn't a lot of fancy programming necessary besides speed control.

Mecanums have the advantage of being able to immediately change from forward & backward motion to sideways motion without having to worry about the wheels turning. Driving on mecanums also means that shifting transmissions are sort of irrelevant (as you aren't going to get much pushing power from mecanums and, as such, shouldn't need a significant boost in torque), and because the rollers allow for low-resistance turning.

Surely there are sacrifices made when designing a mecanum drive for a robot, but I still argue that they are a solid option if you want a simple omnidirectional drivetrain and are willing to live with the consequences.

Also, as an aside, the "drunk drive" (as we called it) that comes with mecanums significantly changes the driving experience, and I personally found it a lot more fun than driving the standard tank drive we used in 2012.

[Ether]

Originally Posted by J_Miles

I loved driving a robot with mecanum wheels.

What was your driver interface? e.g. something this this:

forward/reverse Joystick1 Y axis

strafe left/right Joystick1 X axis

rotate CW/CCW Joystick2 X axis

... or something else?

[sdcantrell56]

Just to add to this conversation...unless it is a particularly special case (2011 our first pick at north Carolina had them) , any team with mecanum wheels is automatically off our pick list. In fact the only thing our pit scouts do is create a list of all mecanum robots.

[jbsmithtx]

Originally Posted by sdcantrell56

Just to add to this conversation...unless it is a particularly special case (2011 our first pick at north Carolina had them) , any team with mecanum wheels is automatically off our pick list. In fact the only thing our pit scouts do is create a list of all mecanum robots.

Why? What is so bad about them?
The only disadvantage I have seen with them is that they are relatively slow strafing versus a swerve.

Our interface was with one joystick (easier and less confusing) with the top two left and right buttons for rotation. We simply put a constant that we were comfortable with.

And they are a simple easy option for relatively new teams for omindirectional movement. Swerve requires a lot of resources, and frankly with a few sacrifices, mecanum is right up there with them...

[MichaelBick]

Originally Posted by jbsmithtx

Why? What is so bad about them?
The only disadvantage I have seen with them is that they are relatively slow strafing versus a swerve.

Our interface was with one joystick (easier and less confusing) with the top two left and right buttons for rotation. We simply put a constant that we were comfortable with.

And they are a simple easy option for relatively new teams for omindirectional movement. Swerve requires a lot of resources, and frankly with a few sacrifices, mecanum is right up there with them...

For one, you never want them playing defense. That immediately removes them from being a 2nd pick. To make them viable as a 1st pick, they need to score a lot. Most teams do not run mecanum. That leaves a very select few left who are viable picks. Add in the fact that in elims there is more defense, a team that can get through defense is usually the preferable pick.

[sdcantrell56]

Originally Posted by jbsmithtx

Why? What is so bad about them?
The only disadvantage I have seen with them is that they are relatively slow strafing versus a swerve.

Our interface was with one joystick (easier and less confusing) with the top two left and right buttons for rotation. We simply put a constant that we were comfortable with.

And they are a simple easy option for relatively new teams for omindirectional movement. Swerve requires a lot of resources, and frankly with a few sacrifices, mecanum is right up there with them...

The strafing speed is one issue. The bigger issue for me is they are worthless against good defense and also cannot provide solid defense either. I have seen too many strong offensive robots be shut down this year in particular as soon as defense is played on them.

Another huge issue I have is that the majority of teams do not program them to be able to take advantage of the few benefits which makes them even less beneficial. Way too many teams drive mecanum robots like a traditional skid-steer robot and only strafe occasionally or never at all. In my opinion, mecanum wheels are a compromise of all things and don't excel at anything.