The June 28th VRC game manual update modified the text of R11 to add the following restriction:
b. Shoulder screws cannot have a shoulder length over 0.20” and a diameter over 0.176”
Shoulder screws sold by Robosource.net are very commonly used in this community, and according to the product pages have an outer diameter of 0.180”. This means that the GDC has chosen to make these screws illegal by 4 thousandths of an inch. It has been confirmed by a GDC member that this change was intentional.
@Grant_Cox I think the community would really appreciate an explanation for why it was deemed necessary to add this rule which makes robosource’s popular screw illegal by such a small margin.
Secondly, as an inspector, how am I supposed to verify that a team is not using a screw which is 0.004” out of spec? Can you explain how this will not cause undue additional burden to inspectors and referees across VRC?
The explanation is in the red box “The intent of the rule is to allow Teams to purchase their own commodity hardware without introducing additional functionality not found in standard VEX equipment.”. They simply took the measurements of the available VEX shoulder screw and wrote it explicitly in the rule.
I have a number of VEX shoulder screws and I can’t get a single one to measure at 0.176” or less. If VEX isn’t capable of making their own screws hit the 0.176” spec then I don’t understand why/how they want us inspectors and referees to try to enforce it down to the thousandth of an inch on 3rd party screws.
I wonder if VEX will provide us official calibrated calipers for measuring of shoulder screws. After all, we wouldn’t want teams cheating and using a screw that’s a thousandth of an inch too big. And I certainly wouldn’t trust my harbor freight calipers for so vital a task…
(Read everything above at like 110% sarcasm)
We had just bought a pack of 1000 assorted shoulder screws from Robosource after seeing other teams use them last season. And now this is codified in the game manual. It would be nice if the GDC implements a grace period or publishes a roadmap of upcoming illegal parts list. Similar to how some software companies publish a list of enhancements in their product roadmap, This will save teams a lot of aggravation.
But will it make a noticeable difference in ease of sticking through a hole depending on whether the OD is 0.176" or 0.177", especially since the ID* of the hole is 0.182"? And we don’t want anybody using any shoulder screws 0.001" too large; that would be an unfair advantage!
I think a reasonable argument can be made that this is the whole point of the requirement. They want to allow a reasonably close fit (0.006" slop is about equivalent to the thickness of 2 sheets of paper). They also want to prohibit any sort of interference fit (the screw should slip freely in, and NOT be a ‘press-fit’ or tighter). If the screw under consideration fits in the hole with about the same amount of ‘play’ as a VEX shoulder screw, the shoulder is basically equivalent.
I would argue the shoulder diameter is NOT what makes the RoboSource shoulder screws distinguishable from the VEX shoulder screws. The biggest difference is the length of thread protruding PAST the shoulder. The VEX shoulder screw looks to have barely enough length for a nut (maybe a nylock), while some of the RoboSource screws have well over an inch of thread extending…