pic: BeachBot Pseudo-Crab drive, partially assembled

Our 2009 drivetrain, partially assembled.

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Wow, so thats what it looks like.

If all else fails does it drive like a normal 6WD?

ooooohhhhhhhh, can’t wait to see it perform in a couple of days ;>

How much is the center wheel lowered? Related: how much does the front rock up and down?

How are you controlling it? (I’d probably use a standard arcade joystick and the x axis of a second joystick to set the angle to rotate the drive base)

Great job as always, cant wait to see how it handles on the crater with a trailer, I bet you could have the best “spin auto” in the game. Too bad I didnt get to see it in person at, guess I’ll have to wait for Champs!

you guys are going to win a ton of awards with that

Wow, so thats what it looks like.

If all else fails does it drive like a normal 6WD?

Yes. The turntable is powered by a BaneBot 545 motor in a 64:1 planetary gearbox, which is not easily back driven. If we do not power the 545 motor, the robot drives like a standard 6 wheel drive robot. We noticed that turning ability was somewhere in between a narrow and wide configuration, but closer the narrow configuration.

How much is the center wheel lowered? Related: how much does the front rock up and down?

How are you controlling it? (I’d probably use a standard arcade joystick and the x axis of a second joystick to set the angle to rotate the drive base)

The center wheel is lowered 1/16th of an inch.

We are controlling the drive with a steering wheel and one joystick. The steering wheel controls the powered turntable, and the joystick is in arcade mode, controlling the drive like a normal 6 wheel drive.

Here’s more info on how it works: http://www.chiefdelphi.com/forums/showpost.php?p=834995&postcount=15

We tried many different methods of controlling it, and what you described is what we ended up with, except using a steering wheel instead of a standard joystick. We also tried a joystick with a Z axis, and several methods of trying to keep the trailer stationary while turning the base, but never got those fully tweaked. If we ever turn into a defensive robot, we might bring one of those back, since it makes driving really easy, as long as you don’t have to keeep the front aligned.

We do have a spin auto mode, but didn’t have enough regolith to fully test it. It’s not that huge of an advantage though for a spin auto mode. We can make the robot spin around the trailer very easy, but that leaves the trailer in one place to get filled up. For actually moving the trailer, we’re not any better then a normal robot. We have other plans for auto, though, so I’m not sure we’ll ever use it.

Team 330,

This is an interesting design. I don’t want to be a rules miser or anything, but don’t you technically have a robot that is turreted and the bumpers move with respect to the drive base. We specifically ruled out doing something like this because the frame that the motors and gearboxes are connected to is technically your fixed drive base. The top structure is a turret that moving. Don’t get mne wrong, I love the design but how is this not considered a turret? Just becasue you put the bumpers on it? I hope that there is not an overzealous inspector that rules against this design. I wouldn’t, but I know some that would …

I’m just looking out for my friends in Southern California.


The earth doesn’t revolve around the sun; the sun revolves around Paul Copioli.

(In all seriousness, to my knowledge the rules don’t ever specify that the bumpers and trailer hitch must be stationary relative to any particular reference frame).

It shouldn’t matter: the rules say where the bumpers should be with respect to the entire robot (i.e. in the bumper zone, on the perimeter). What happens inside the robot, or where its drivetrain is located, doesn’t affect anything.

It’s popular to define the robot frame as “the thing that holds the wheels”, but the rules make no such definition. (A similar situation came into play last year, with 1519’s dual-configuration robot/two robots. It was ruled that because the main structure of the robot was being interchanged, that it was actually two robots…the trouble was, there was nothing in the rules to define the main structure.)

I can’t see an inspector ruling this out, in reality it is like any other crab drive, the wheels rotate and the base stays in a fixed location. The sole difference is that instead of a single wheel rotating 6 of them are.

Just my $.02

I would think that this is not dissimilar to any drive train that has independently steered wheels… so which wheel in our swerve is the robot? they all move independently and you could loosely say we have a turret design too…

I would think that the robot…for this game… could be defined as whatever attaches directly to the trailer…

I hope you guys do well… and we hope to see you in Atlanta again…


I think I understand where Paul is coming from; we had the idea at the beginning of build season to attach the bumpers and trailer hitch on a turntable so they could be moved relative to the rest of the robot, but threw it out because of rule R18.B:

It seemed obvious to us at the time that the design would not pass inspection… based on the logic we were using at the time, 330’s design is questionable, as is any robot with a swerve drive to some degree. It’s kind of a hazy subject that will be left open to the inspector’s interpretation.

I certainly hope there are no inspection issues though… it’s a cool design!

I am curious to find out why you would think that the Beachbot’s design does not comply with this rule?

“The trailer hitch is rigidly attached to a fixed location on the robot.”

In their design this is true…for it not to be true you would have to have a non-fixed location or a location that is changing on the robot.

Just because the wheels turn under the frame does not make this false…

If one were to define “fixed location” on the robot in the way it is apparently being discussed… you would have to have NO moving parts on the robot at all…

Relative motion is relative motion…

What is moving? One can only define that when one picks a frame (no pun intended) of reference. The Beachbots have chosen to use their outer frame as that frame. It is fixed… the wheels rotate below it…rigid attachment and fixed location… sounds ok to me…

I would be happy to argue this rule with an inspector…
(I am a physicist so frames of reference come naturally to me…)

The only rule that seems to apply is R6. Since the wheels can only be rotating in the direction 330 will be moving, no problem.

330 has proven once again why they are a perennial powerhouse: out of the box thinking, design, and something that advances FIRST.

Well done. Can’t wait to see this in Vegas.

We thought of the same thing. But also ruled it out due to the shadyness of the rule about the fixed bumper location.

“Fixed” relative to what? Since all the other parts of the trailer hitch constraints seem to revolve around the bumper perimeter, I would be inclined to say that the bumper perimeter would be the most logical point of reference. In the case of 330’s design, this is a fixed point.

As a side note, 230 had a similar design except that their outer frame is free spinning and the robot rotates inside of it. They were allowed to compete at Boston, and I would consider it legal for the same reason as stated above.

All things considered, this looks to be a great platform. Well done.

See you in Vegas!