Robosource shoulder screws now illegal

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 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?


theyll never know if they dont see it ehhehehehehh
but seriously why make this change? and how would they know? i feel like this would cause delay in competition if inspectors actually care to check.


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.


nope, fixed now. Kevin does a little trolling…

1 Like

Just to confirm:

Measured about a dozen, 10 were within allowable size, others due to tolerance but they’re probably fine - vex tolerances are much worse than this.


Yup. Bought several packs of axles. Every single one was bent in every single pack.


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 was hopeful that the GDC wouldn’t screw up this year’s rules as much as last year’s.
I just lost most of this hope.
Maybe the new Student Advisory Board will help with this?


I am sure there is uncertainty listed in the tech specs sheet?
And if we take into account of the uncertainty involved, most likely it should still be legal?

Edit: I couldnt find any tech specs listing the uncertainty for the VEX shoulder screws though


Maybe obvious question; is that a VEX or a Robosource screw?

Robosource. Vex doesn’t sell color coded screws or shoulder screws in that nice of a size.

1 Like

In soccer terms, this is literally VEX scoring own goals. lol…


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)


Probably, although they’ll be 200 dollars and mandatory for inspectors to use at competitions.


And out of stock the entire season?


:roll_eyes: stop giving valid criticism rules lawyering alec, you know its been a tough week for the gdc up in their ivory tower, they had to log on to the forum and make an entire post.


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.


I suspect there is a much easier gage they can use. VEX metal has holes 0.182" square.

If a shoulder screw doesn’t fit readily in a non-enlarged hole it is too big…


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!

* Wrong terminology for a square, I know.


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…

1 Like