Non-Rover Wheel caster

[FRC2036]

<R06> explicitly states that traction may only be provided by Rover Wheels, but we are planning to use COTS casters for balancing stability since they will not provide traction.

Can you confirm that this is legal? If not, what exactly prohibits this?

[FRC2929]

http://forums.usfirst.org/showthread.php?t=10943 posted 1-9-09 answered the question "Besides the low friction wheels can any other part of the robot contact the crater floor?" with the statement "Other parts of the Robot may contact the floor, as long as the part does not provide any traction for the Robot."

http://forums.usfirst.org/showthread.php?t=11098 posted 1-11-09 and http://forums.usfirst.org/showthread.php?t=11201 posted 1-12-09 both deal with casters that are use for sensing movement (which requires some amount of traction). The official ruling was "Any portion of the ROBOT (other than ROVER WHEELS) in contact with the surface of the CRATER that provides tractive/braking forces in any direction will be considered a violation of Rule <R06>. If a high-friction wheel is being used to drive an encoder, it must be both free-rolling and freely-swiveling to avoid a violation." and "Acceptable sensors will gather information, but not affect the tractive performance of the ROBOT. They will produce only resistive traction, be direction independent, and be invariant during the entire MATCH. The TEAM must be prepared to provide test data verifying that the maximum sensor traction is not more than 5% of the maximum traction of the ROBOT (acceptable validation methods would include test data logging total drawbar pull both with and without the sensor in place).

Based on those original rulings, our design concept (and implementation) has been to have ROVER WHEELS on the left and right sides but centered front-to-back. In addition we have free-rolling and freely-swiveling casters (along with being low-friction material) placed toward the front and rear of the robot. The ROVER WHEELS are mounted slightly lower than the casters to guarantee that the ROVER WHEELS are always in contact with the CRATER - this will provide a slight "tipping" action depending on weight distribution, contact with other robots, etc. However, with the weight properly balanced, the vast majority of weight would be on the ROVER WHEELS and very little would be on either the front or rear casters (and therefore would "not provide any traction for the Robot.")

But the official response http://forums.usfirst.org/showthread.php?t=11255 posted 1-18-09 appears to rule that casters for the purpose of balance are illegal, regardless of the amount of traction/drag that they might have.

So my specific question is: Will a design that utilizes casters that are free-rolling and freely-swiveling, and also for the purpose of balance, be allowed (either with or without the supporting test documentation)?

Thanks,
Team 2929

[GDC]

Thanks for the thoughtfully posed question. The intent of the ROVER WHEELS-only rules and their interpretations has been to make sure that all ROBOTs have equal opportunity for traction without giving the robot inspectors an impossible job. We have tried to be consistent with regard to ROVER WHEEL-only traction rules while ruling favorably on questions related to sensors being used to measure ROBOT's movement.

COTS casters used as you describe are a violation of <R06>. You have many options for accomplishing what you desire using ROVER WHEELS.