Nonsensical Q and A Answers

Oh boy.

The GDC sure did some ruling and I’m not quite sure where to start as there are a whole lot of G3 violations on the GDC’s part.

First we have the spacer Q and A: Use of Nylon/Other commercially available spacers for HS Shafts : Robot Events

This Q and A ruled that you can’t use spacers with an interior diameter that doesn’t match one of vex’s approved screw sizes. There is very little reason to do this, but I guess the GDC felt the need to have spacergate after screwgate. It is perfectly legal to machine your own spacers with different interior diameters, but vex wants your money, and only want you buying their official spacers.

Second, the roller Q and A: G16 - Grappling onto Field Elements : Robot Events

This ruling states that having a mechanism around the roller may or may not be illegal. The GDC isn’t sure and neither do you now. Have fun designing your potentially illegal bot. Oh, and that sketch provided? It might be illegal or illegal.

Third, the blow dart Q and A: Using Pneumatic Components with Non Pneumatic Components : Robot Events

A team was asking about launching screws with pressurized air. To their credit, the GDC gave an easy to interpret (albeit lacking logic) response. This was ruled illegal due to “rapid, uncontrolled depressurization”. However, there is no way to prove that every mechanism will meet these criteria. A team may be launching projectiles at only 10 PSI instead of 100, thus not having a rapid expansion. And thankfully, science can be used to predict airflow, thus leading to controlled depressurization. It is possible for a team to create an expansion mechanism without either of these traits, but the GDC decides to make those illegal as well. It is also worth noting, that many teams are creating string launchers without the use of pneumatics and will continue to do so. I get that this was partially done for safety reasons, but I don’t think that it was inherently more dangerous than other methods.

Fourth, the vertical ceiling Q and A: Q and A 1185 and SG5 follow up : Robot Events

This one was my question.I n order to avoid getting the standard “blanket statement” response, I gave 2 very specific scenarios. What did I get? “Your specific questions are extremely context-sensitive, and we cannot provide blanket answers that will accommodate all possible situations.” The GDC could have at least ruled on the 2 highly specific scenarios.

Fifth, the pneumatic valve Q and A: Modifying Pneumatics Clarification : Robot Events

This Q and A asked if you could use a bike pump fitting to fill up your tank in between matches and still have it attached. The Q and A acknowledges that the part is non legal, but it could count as a non functional decoration. The GDC responds by saying it is not a legal part. This was already clearly established. Would anyone on the GDC mind answering if competition illegal parts are competition illegal?

Best for last. Possibly the stupidest response of them all, the no tank Q and A: Pneumatics without tanks : Robot Events

Some teams have found a way to use pneumatics without a tank. This involved charging the cylinder and solenoid as usually, and then detaching the tank from the system. My team did this to forgo the use of tanks entirely on the robot. The Q and A asked if this was legal. The GDC responded “Teams may not use other elements for the purposes of storing or generating air pressure. Using cylinders or additional pneumatic tubing solely for additional storage is in Violation of the spirit of this rule.” The pneumatic parts used are other elements. They are not used for the sole purpose of storing air, and the whole point of doing this is to get less air storage. The quoted rule does not at all apply.

Furthermore, many teams in my org were planning on doing this as our org only has 4 tanks for 6 teams. We can’t buy more tanks as they are out of stock, and this would allow these teams to still use pneumatics without a tank. But now the GDC is actively making it harder for teams to have a level playing field. This is contrary to the RECF mission statement and highly hypocritical as the GDC banned aluminum screws for the sole purpose of creating a more level playing field.

I hope @VEX_GDC , @Grant_Cox , @Jon_Jack will see this and consider changing some (especially the last one) of there ruling. These Q and A’s have only muddled the rules, stifled creativity, and created a more uneven playing field. At the very least, I would hope the GDC would give an explanation for some of their rulings.


Have to say I love the term “spacergate”

Edited to add:

I followed the spacer link back to the screw decision and I saw this in the addendum by Grant “scuf paddles for your controller”. Oh right, there are “some” things you can 3D print.


This is very true, their answers to the qna were pretty odd and like they don’t even answer the questions correctly, but hey, they are the gdc (the going nowhere disorderly council).


In the discord I have been vocal on some of these views and I feel I can give a Head referees views on these points.

The first question I do not really have a opinion on this, I think there is a line to be drawn on legal spacers and I feel the GDC may have erred on the side of sticking to the manual so I will not argue that point.

For the second question In terms of the roller question it is fair to state that if you have a mechanism designed to use the roller to hold your bot in place in a way that it could be seen as anchoring you will be in violation. I feel this ruling is a fair and gives leeway to the referees to ensure that mechanisms that are intentionally designed to hold in position are illegal while not outlawing entering under the roller.

For the third ruling I have made my view on this clear and I can account for numerous other head referees being against having screws launched from robots using pressurized air. In the case of the rapid uncontrolled depressurization definitely occurs amongst numerous teams mechanisms and while it is fair that it can be made controlled and predicted this is far beyond what many teams will do. As a counterpoint to your statement of “there is no way to prove that every mechanism will meet these criteria” we also have the point that to prove that it is not adds an extensive amount of time and/or cost to inspection at events. As referees many of us do not like string launchers for many reasons and these other expansion mechanisms you speak of have been Q&Aed and if deemed too dangerous will not be allowed on the field following S1. I can add more to this but this answer is already dragging on.

Being the one who asked the Q&A you followed up I feel as though my question was answered reasonably well despite not answering with a “blanket ruling”. I admit that the GDC could have given some more detail in your answer specifically with your scenario 2 which I would certainly rule as a warning and/or a dq for a match affecting offense if I deemed the angle change match affecting. I can only give my view directly on scenario one but I would deem it as the GDC stated “standard game play” and not issue a warning or dq.

I can see partially where the GDC come from in the pneumatic valve Q&A, my view on it is this comes from an inspection standpoint as it would mean nonstandard parts to look for however my opinion is that bike fittings should be legal. Here though I do not think its necessarily unfair but I wouldn’t call it nonsensical.

For the tankless pneumatic Q&A I think I will refrain from answering for now as I have not developed an informed conclusion to this on my own yet and feel I will not add anything to the discussion at this point.

I think overall while I’ve disagreed with many GDC decisions over the years calling all of these decisions nonsensical and illogical is not a fair response. A view of the game from a referees point of view gives a very different understanding of the logic of the GDC. Additionally I am a competitor in the VEXU competition and I competed from 2016-2020 in the high school competition so I am not completely disconnected to the competitor side.

Stock will always be a problem in any part of the competition and I feel arguing that rules should be different for loopholes to work because of lack of stock isn’t really a solution to that problem. If that were the case international teams would have a lot more sway on the rules e.g nz where we can be left waiting even up to years for parts to reach us. A possible solution you would probably dislike to even the playing field would be to go back to the old system where pneumatics were a trade off because it is unfair to expect teams to get pneumatics at all.

I think its important to try and consider all of these points and try to see things from other point of views. There are many groups the GDC has to cater for and while I would like more clear answers to some Q&As and I would like questions to be answered in a more timely manner I do have to say that these rulings aren’t completely illogical.

Apologies for rambling and if my points didnt provide any useful insight/perspective.



" Theoretically, there is probably a commercially available spacer with a legal inner diameter ID, that a Team could claim that they have purchased, bored out with a drill press, and used as their 2.5" long HS shaft spacer. Realistically, going to this length to avoid using the HS shaft spacers sold by VEX is similar to the points made regarding “hollow screws” in this Q&A."

I do this. Drilling bigger holes in spacers is really really easy, and is super useful.

The gist for this one is clamping on to the roller. Based of the Q&A answer my idea of a roller cage that just freey spins around the roller attached with string would be legal(MAYBE?) because it doesn’t clamp on and isn’t designed to anchor the robot to the feild(have string to attch and still drive around).

I don’t really mind this one that much. It kinda sucks for ppl who have or where making it, but I can absolutely see where the GDC is comming from this one. Our prototype launcher crosses the feild very easily and the accidental discharge with air pressure is innately dangerous .

This was one of the Q&A with specfic specific questions I wanted to know. I there there is major strategy and design impact based on the Q&A. I think desinging a bot that can score in high goal from across the feild. I also don’t think that a reff would be able to tell if driving over a barrier or using the barrier to shoot was match effecting.

Agree, they didn’t answer the question if haveing it as a non functional decoration attached to pneumatics ok.

The intent of this rule is to limit Robots to the air pressure stored in two reservoir tanks, as well as the normal working air pressure contained in their pneumatic cylinders and tubing on the Robot. Teams may not use other elements for the purposes of storing or generating air pressure. Using cylinders or additional pneumatic tubing solely for additional storage is in Violation of the spirit of this rule.

I would think that the “normal working air pressure” would allow you to fill the tubes to the normal working air pressure. I think the rulling contradicts the rule they quoted. You aren’t useing the tubing for “soley for additional storage” you are useing the working air pressure of the system to keep the cylilder extended or retracted.


This would still be considered anchoring even if the main robot can drive away if your cage is attached to the roller. If I were to grab a pole I can still move around within the extent of my arm while it is still considered grabbing.


There was no ruling on spacers. The response was purely quotation of the rule in the manual. The question did not need to be asked.

Depending on whether it may damage the field or be considered by the head to be anchored to the field. Again, a direct quote from the manual. The diagram implies something that a head ref would probably have no problem with – but it would need in-person scrutiny.

I am a wee bit surprised by the blanket ruling - as you mention the GDC goes straight to “rapid, uncontrolled” when there could be safer methods. I would guess they got there assuming (logically) the intent of such a mechanism in this game would be a long launch, which would require rapid depressurization. Potentially unsafe, they nipped it in the bud.

Clever idea, but the response is again not a ruling but a logical quotation of the manual. You should be able to swap tanks between teams in a pinch. The scarcity of parts is a real pain.


not really, no.

the rule in question explicitly states it is illegal to use pneumatic components “solely for the sake of additional air storage”. The gdc points towards this line when saying that forgoing air reserviors is illegal. But the pneumatic cylinders in question are not solely being used for air storage, they have a function, usually actuating a single use mechanism.

Besides, in a pneumatic system that does involve the use of tanks, pneumatic cylinders will exist on the robot in a pre-pressurized state as well. They aren’t illegal because they aren’t solely for air storage.

So really, this q&a response is in direct contradiction to the rule referenced.


The tubing between the solenoid and the cylinder has two purposes – storage of pressurized air and transfer of that air. So, yes, “solely” is the word in question. Does doing two things negate the rule?

If you are correct, a team could use 100 meters of tubing to store air and not have a reservoir. Is that reasonable?

You are relying on your proposed system being a deficit to justify the exemption. Keeping the definition of the pneumatic system tight is an effort to prevent exploitation.

using additional tubing than is reasonable (100 meters) is clearly “solely” for the purpose of extra air storage.

but since the cylinders exist as part of a functional mechanism, and all tubing/solenoids are clearly part of the operating function of the cylinders, I don’t see how a case can be reasonably made that this is “solely” being used to store additional air.


Ok, the tubing in the defined vex pneumatic system has two purposes - storage and transfer. When the reservoir is removed, what is the primary purpose of the tubing? Its not transfer, because there is no supply of air that is in motion. So the primary use is storage (even if it is a tiny amount.) The tubing in the situation you describe does not transfer any air - it releases the air stored in it. So, in the situation you describe the tubing in fact has one purpose, air storage, which is prohibited by rule.

the primary purpose of the tubing is to create a channel between the cylinder and the solenoid, allowing the solenoid to release the air at the desired moment?

and again, if tubing which is doing nothing but containing air at any moment can be considered “solely” for the purpose of air storage, than every length of tubing on every bot, reservoirs or not, would be in violation of this, simply for existing with air stored inside while not in current use.


It really does feel to me like, in an effort to prevent teams doing anything that feels like a “loophole,” they just try to make things illegal that shouldn’t be. To further beat a dead horse about the pneumatics issue, let’s go through the rule, point by point

It starts out with a limit on the number of tanks and air pressure.

Pneumatics are limited. Teams may use a maximum of two (2) legal VEX pneumatic air reservoirs on a Robot. Pneumatic devices may be charged to a maximum of 100 psi.

The rule seems to be trying to limit the capability of the pneumatic system, in much the same way they limit the capability of the motor system by limiting the number of motors.

Conveniently, they then explicitly state that the intent of the rule is

to limit Robots to the air pressure stored in two reservoir tanks, as well as the normal working air pressure contained in their pneumatic cylinders and tubing on the Robot

So, again, the goal is to cap the maximum capability of the pneumatics system to the two tanks, while acknowledging that there’s going to be a bit extra because of tubing/cylinders. To prevent the obvious loophole of using a bunch of excess tubing, they further spell out

Teams may not use other elements for the purposes of storing or generating air pressure.

Perfect, don’t use elements other than the actuators necessary for the actual… actuation… to either store excess air, or regenerate air pressure by hooking it up to a motor or something to repressurize. You gotta stay under the cap they set out

Using cylinders or additional pneumatic tubing solely for additional storage is in Violation of the spirit of this rule.

So if I have a cylinder not doing anything, or I have pneumatic tubing that’s obviously just being used to get storage in addition to the cap, that’s no bueno. This all makes sense.

By the letter of the rule, and by the stated intent of the rule, as long as the tubing is the minimum required to connect a cylinder to a solenoid

  • You have not violated the main text of the rule
  • You have not violated the stated intent of the rule to limit the robots to the air pressure stored in two reservoir tanks and the normal working air pressure, since… you only have the normal working air pressure
  • You do not have extra other components used for the purpose of storing or generating air pressure, these components are being used as actuators only
  • While cylinders and pneumatic tubing makes up the entirety of the air pressure in the system, it is not solely being used for that

Now, I personally think that pneumatics without a tank should be illegal. You want to use pneumatics without even any kind of motor penalty? OK, the tradeoff is you have to fit that stupid unwieldy tank on your robot somewhere. But just because I personally think it should be illegal, doesn’t mean I think the rules actually make it illegal, because… they don’t.


Shooting screws across the field isnt safe…
But launching chunks of metal at higher speeds is?


Exactly, it’s perfectly alright if the gdc wants to mandate the use of pneumatic tanks with the system. Regardless of whether or not people like it, at the end of the day they are the ones who make the rules.

I think the problem arises when the gdc references a rule in a decision like this, which does not match what the gdc is saying it does. It seems to me that they are stretching their desired interpretation of this rule far beyond the text of the rule itself, to the point where the answer they’ve given here directly contradicts the rule they reference. This is problematic because even the most clearly worded of rules is subject to have its “intended interpretation” changed by q&a answers in ways not predictable by reading the rules. I think it would be much preferable if the gdc would either change the wording of a rule, or create a new rule in situations like these, where they want to make something illegal, which isn’t actually illegal based on the rules.


I agree that the rule was clear -

c. Any commercially available nut, washer, standoff, and / or non-threaded spacer up to 2.5” (63.5mm) long which fits these screws.

If I am size S, does size M or L shirt fit me? I would argue yes albeit it would be kind of loose or baggy. Does anyone think that it is not acceptable to wear loose shirts? No.
The point is that spacers with larger ID fit #8 screws, albeit loosely. Also, with so many other tougher issues not addressed by GDC and left to Head Ref to rule, what is the need to be anal about this spacer? What happens to common sense - if it is used as spacer, then it is a spacer? Or if the shoulder screw fits in a standard vex metal hole, then it is legal? I don’t get why GDC is preaching the use of common sense and leaving so many tougher rulings to head refs, but they would come up with this anal restriction. Wait, I get it, because this one is easy. Always leave the harder jobs to others. :ok_hand:

@VEX_GDC Please stop playing word games. All you need to say is spacers with ID larger than certain inch is illegal. Just so you know if you even try to do a bit of research, the spacers marketed as #8 come in multiple ID. Some tighter, some looser.


This feels ironic because the GDC strongly dislikes when the community partakes in rule “lawyering” when it comes to robot rules, but at this point, with the way they are using the quoted rules, it seems that they are now the ones lawyering their own rules…?


to add to this, this ruling would be constraining spacer IDs to these sizes only:

#4 (0.11")
#6 (0.13")
#8 (0.15")
M3 (0.118")
M3.5 (0.138")
M4 (0.157")

This is just silly, and impossible to enforce. No inspector could be expected to use calipers to measure the inner diameter of every spacer on a robot. Absolutely nothing is preventing a team from purchasing spacers with alternative inner diameters, such as 1/8", and the vast majority of teams doing so wouldn’t even know this is apparently illegal.

It’s also unfortunate that this explicitly prohibits teams from buying spacers to fit HS shafts, even though vex themselves sells such spacers. Similar to the whole deal with third party nylon screws being illegal while vex actually sells nylon screws.


Double click on the word “fits” in chrome and you get

You are making fit synonymous with accommodate.

I love how going to McMaster selecting #8 screw size doesn’t even come up with this size

It really is silly, would they list each ID that is possible for each size? there is no way to check, and you can still drill to make it bigger SO IT DOES’T MATTER.