Teams may use any commercially available fastener on their Robot. Examples include (but are not limited to) screws, nuts, washers, rivets, hinges, pins, rod ends, threaded rods, hose clamps, bushings, spacers, or standoffs. a. To be considered a legal “fastener” in the context of this rule, the primary function of the part must be to join or fasten together two otherwise legal parts. For example, a pre-fabricated non-VEX wheel (which would be illegal under VUR5) would not be considered a “fastener,” even though it may also technically serve the purpose of bridging the connection between tread and a shaft.
In the vast majority of applications, bushings allow components to spin freely on shafts. Since bushings are explicitly allowed, it stands to reason that 2 parts are considered "fastened" if they are constrained together along many axes, even if they are not totally locked together. For example, a bushing might be used to fasten a gear to a shaft. The gear can spin relative to the shaft about the pitch axis, but it cannot spin about the roll or yaw axes, or translate along any axis. As such, it is fastened to the shaft. Is this a correct interpretation of the rule?
If so, we have 4 follow-up questions:
1.) Some potential fasteners allow relative rotation about one axes, just like bushings, but are not explicitly listed in VUR7. Bearings are the most obvious example. Are COTS bearings and other similar components legal if they are used as fasteners?
2.) Some potential fasteners allow relative rotation about multiple axes. For example, a ball and socket hinge prevents fastened components from relative translation along x, y, and z, but it allows relative pitch, yaw, and roll. Are COTS ball and socket hinges and similar components legal if they are used as fasteners?
3.) Some potential fasteners allow relative translational rather than relative rotation. For example, a COTS linear slider might be used to fasten a claw to the robot's chassis. The slider allows relative translation along x, but it prevents relative translation along y and z, and it prevents relative pitch, yaw, and roll. Are COTS sliders and similar components legal if they are used as fasteners?
4.) Some potential fasteners allow relative translational and rotational movement at the same time. For example, this linear bearing could be used to fasten a claw to a linear rail. The linear bearing would allow for relative translation along the y axis and relative rotation about the pitch axis, but would prevent relative x and z translation, and roll and yaw rotation. Are COTS linear bearings and similar components legal if they are used as fasteners?
Thank you for your time!