I was thinking more about this today and made a grave realization that these two Q&A Forum answers just painted FIRST into a corner that will make nearly all appendages illegal.
Quote:
Game - The Game » Robot Actions » G21
Q. Our question is similar to FRC1540. We want to put surgical tubing "whips" on a roller located at the frame perimeter. When this rotates the whips will extend beyond the frame perimeter. Is each "whip" its own apendage or is the assembly considered one appendage? FRC3219 2012-02-01
A. If multiple items exit the Frame Perimeter and are not contiguous outside the Frame Perimeter, they are considered multiple appendages.
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Quote:
Game - The Game » Robot Actions » G21
Q. To prevent differing interpretations of G21 and the following Q&As on appendages could you address the legality of a appendage BRIEFLY crossing the frame perimeter in multiple places during deployment? For example, a "H" shaped appendage might cross in two places as it quickly folds out. FRC1540 2012-01-30
A. Any time the appendage is outside the Frame Perimeter, it must be a contiguous piece.
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What this means: if you follow these two Q&A rulings strictly, all wheels, gears, sprockets, rollers, or any other type of rotary motion device (with an axis of rotation parallel to the frame perimeter) on an appendage are now illegal.
Why?
There will always be a portion of the wheel, gear, or sprocket that is dis-contiguous from the rest of the appendage for the small duration of time between which the edge of the wheel, gear, sprocket, roller, etc breaks the plane of the frame perimeter and when the shaft breaks the plane.
Photos are worth a thousand words:
Image 1: What common sense would define as a contiguous appendage. In this case, it's a simple wheelie bar that extends straight outwards. The grey part is the robot base, the black side is the frame perimeter. The light red, blue, and green parts are an appendage that comes straight out. This appendage is entirely inside the frame perimeter and is legal.
Image 2: The appendage has started to break the frame perimeter and extend outward! This is a section view of the CAD assembly, looking outward from the frame perimeter. So far, so good. The appendage is contiguous.
Image 3:
The appendage has continued to expand out, but it's now illegal! The portion of the wheel that has broken the plane of the frame perimeter is now dis-contiguous (outside of the frame perimeter) from the rest of the appendage!
Image 4: The appendage continued to expand outwards, and the axle of the wheel finally broke the plane of the frame perimeter! The wheel is now 100% contiguous with the appendage outside the frame perimeter again and is legal once again.
As these images very clearly show, unless the FRC GDC intended to ban all wheels, gears, sprockets, or rollers with a axle/shaft parallel with the frame perimeter, there must be an exemption of the contiguous mandate for appendages in the act of deploying.
There is a very simple solution solution to this fix this problem:
only require the appendage to be contiguous outside the frame perimeter when it contacts or reacts with some element on the playing field.