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Unread 03-02-2010, 13:32
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Tristan Lall Tristan Lall is offline
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FRC #0188 (Woburn Robotics)
 
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Re: Fasteners extending outside the FRAME PERIMETER

Quote:
Originally Posted by Vikesrock View Post
That bolt defined the FRAME PERIMETER. If you had a 26"x36" frame with fasteners sticking out in the BUMPER ZONE 1/4" on each side right in the corners, your FRAME PERIMETER was a 26.5"x36.5" rectangle.

This meant the rest of your robot had to fit within a vertical projection of this 26.5"x36.5" rectangle per <R16>.
There's a little problem with that reasoning: although they don't go right ahead and say it, by giving the string example in the definition, it's clear that the definition of frame perimeter refers to the minimal convex polygon within the bumper zone. For many designs, that's different from the minimal bounding quadrilateral (which you're describing). (There are even a couple of possible—but unlikely—cases where this isn't the minimum quadrilateral either.)

Unfortunately, it's not exactly clear whether this is intended to be an imaginary string wrapped around the projection of all such points in a plane, or wrapped around the outermost subset of points that are coplanar within the bumper zone. (Imagine that on a rectangular robot, two opposite sides have bolts at 10.5 in from the ground, and the other two sides have bolts at 15.5 in from the ground; how do you wrap that string and still meet the definition? If we're talking string, then concavity in 3-D is the same as in 2-D—i.e. not allowed. How do you define "outermost"—is this with respect to a centroid? Which one, and how do you find it?)

In any case, if your outermost bolts within the bumper zone are near the corners of your rectangular robot, we can use your example as a rough approximation for the purposes of discussion.