[Tristan Lall]

In the past, the rule has been unspecific with regard to the precise design of allowable fastening methods. In the past, after some internal discussion, the inspectors have been instructed that since the illustration in the rule depicts mating threaded fasteners, and offers this as an example, threaded fasteners are (almost) universally allowable. As I recall, the discussion also covered the idea that standard nuts and washers could be reasonably considered as fasteners (which are included in the bumper weight), but that extra items like custom washers or brackets were to be regarded as parts of the robot. (That's a broad summary of a nuanced discussion; it is not an official ruling, nor an endorsement of any particular fastening method!)

Designs using clevis pins are sometimes seen, and were sometimes allowed (particularly in 2006), depending on the implementation details. However, in both this year's iteration of the rule (2008 <R08>), and last year's (2007 <R37>), it specifies a "bolt-and-fastener" method of attachment, which would seem to render a standard clevis pin illegal, but might arguably allow a clevis pin made from a bolt. (I don't know the details of 1138's clevis system, but I'd advise them to pay particular attention to this point for 2008, just to be safe.)

The written part of the rule also doesn't specify any required positions or orientations of the fasteners. As a result, the diagram (which depicts a bolt and a T-nut in the centre of the plywood) could be interpreted either as one possible configuration, or alternatively, as the only legal configuration. For the most part, this has been interpreted as the former by the officials (allowing more creativity and cutting the teams some slack). Under that interpretation, some teams have therefore installed bumpers with multiple rows of fasteners, fasteners inserted nonperpendicularly in the plywood, and fasteners inserted into holes drilled into the edges of the plywood. All of these things seem to be legal permutations.

There are also varying interpretations of whether you can design the bumper so that the fabric needs to be removed in order to unfasten the bumper. I would consider this to be antithetical to the statement (in the diagram) that bumpers be quickly removable. I've seen it both passed and failed at inspection—and sometimes passed once, then failed at the next event.

I believe that there was also a past Q&A response (likely in 2006, if my memory serves me correctly) specifying that it was not permissible to pierce the fabric of the bumper in order to install fasteners (even if the hole was patched, or reinforced). This is an issue when a team installs a regular hex nut on the inside of the bumper, and wants to tighten it with a nut driver or socket wrench. I'd avoid this design, in case a similar ruling is delivered this year.

Whatever you do, do not use zip-ties, hook and loop fasteners, or tape to secure your bumpers. Those will be rejected at inspection.

Note however, that with this rule in particular, you need to ask in the Q&A forum before proceeding. The official responses there will dictate how officials will interpret the ambiguity in the bumper rule for the 2008 season.