Is hot-melt adhesive legal in VEX U?

Not sure if hot melt adhesive is legal in competitions (VEX U).

Its probably stated in the manual.

Okay… maybe that’s a bit of snippy answer, but if you’re engaged in post-secondary studies some degree of “look it up your darn self” is to be expected.

Open the manual in acrobat, hit “CTRL-F” and enter “Glue”. You’ll find R7g says yes, for one particular application. Then look what else you’re allowed to use… like R16f. Then check appendix E, the VEXU rule modifications to see if there are any exceptions in there.

I could tell you the answer, but you’ll learn more by looking it up.

Thanks a lot! I’ll check the manual next time.

Its actually not in any of the game manuals (appendix E included), but the official ruling was stated on RobotEvents (which is considered “…as official and binding as the written Game Manual itself.”)

Wait… WHAT???

Thank you for the link… but the Q&A is, quite simply WRONG.

Stay with me here… just like a ref can make a bad call, so can the Q&A. It’s a technical failing, not a moral one, and it can be fixed.

To quote the Q&A page, “Note 1: The Q&A system is for rules clarifications only.” There are specific rules banning welding and gluing and there is NOTHING in VUR3, or anywhere else that overrides those rules. Eliminating or over-riding a rule is not “clarifying” the rule. The rule is quite clear on welding and gluing.

The correct procedure, should VEX/RECF have written a rule differently than how they wish they had written it is to make an announcement and change the rule in the rule book… in this case adding a clause to VUR3 stating that “Welding, Gluing and other fabrication methods are allowed in VEXU”. Saying “We will keep this distinction in mind when revising VEX U rules in the future to be more clear.” simply reinforces the fact that in this year’s manual it is still banned.

Personally, I can let it slide… I’m not involved in the tech inspection of VEXU teams… but it is a sloppy answer that fails to follow established protocols. The GDC can change the rulebook… but not through Q&A. They actually have to change the rule book.

On a related note, however, it also shows that neither the person who asked the question, nor the person who responded to it fully understands (or failed to communicate) the processes involved. You don’t, for instance, use either steel or aluminum as a “filler material” when brazing… and you don’t need a filler material when welding. The “unlimited amount of steel and aluminum” is completely unrelated to how the materials are being joined.

I suppose one creative interpretation in relation to hot glue would be that hot glue is a “non-shattering plastic” and you’re simply fabricating a part that fits very tightly to two other parts. Given that gluing IS explicitly banned, however, my response as an inspector would be to say, “fine, separate the parts, then reassemble them to show me that there is no chemical or molecular level adhesion at the surface.”

The precedence of the manual over Q&A may seem like a small point, but it is actually very significant… I hope VEX/RECF addresses this contradiction quickly. I’d hate to see something similar show up at a high school event where I’m inspecting. To be very clear, “Welding is allowed” is NOT a ‘correct and official’ interpretation of “welding is not allowed”. That makes no sense. Perhaps, in future, VEXU needs an entirely separate manual, rather than simply an appendix.


@dtengineering While Appendix E is somewhat ‘loose’ this year due to the new rules, I think if the Q&A states its legal, then inspectors at worlds will most likely abide by it.

The official answer was a “clarification” of the term “fabrication”, as fabrication techniques should cover joining techniques like welding, brazing, and gluing.


Again, this is a ‘clarification’ of the term ‘fabrication’, not overriding , but yes, it should definitely be stated under

Pretty sure last time I used a MAPP gas torch to braze aluminum, I used an aluminum-silicon alloy rod as “filler material”. And while some welding processes do not require a filler, others do, such as stick welding which uses steel as a filler and electrode.

Again, the Q&A has as much authority as the manuals, and the GDC maintains both. Neither are contradictory, the Q&A simply clarified the term “fabrication”.
I honestly hope that any high school and middle school teams who read that clarification realized that does not exist in their game manuals.

If you still think the “clarification” is wrong, then you can try posting on the official Q&A.

I think a welded robot won’t be the most extreme thing we’ll see this year. I’m tempted to ask the lab next door if they have some scrap carbon fiber.

Yeah, it would be pretty difficult to say that a team that followed the Q&A didn’t “follow the rules”… and my general inspection rule is that in the event of any potential misunderstanding that the benefit should be given to the team… as I say, the GDC can change the rules during the season, but the place to do it is in the rulebook, not by contradicting the rule book in Q&A.

I will, however, grant you that my definition of brazing may be a bit restrictive… I tend to use it specifically for a high-temperature soldering process involving copper based alloys… which, apparently, are still explicitly banned as no amount of brass or bronze is allowed on the robot.

Unless there is a Q&A defining brass to be steel and bronze to be aluminum, of course! :slight_smile:

As an FRC veteran, I’m actually rather delighted that they’re going to let the “big kids” play with real tools… I actually wish they had a bit more freedom of fabrication in the junior divisions. The ban on 3D printed parts has long since lost any rational justification now that you can purchase a 3D printer for less than a V5 (and that’s WITH the trade in allowance!)

I’m not going to follow up with an additional Q&A because VEXU is of little relevance to me… however I’ll definitely be taking up matters if the GDC starts getting sloppy with the high school rules. They’ve done an excellent job over the past decade-and-a-bit of following protocol and keeping the Q&A to interpretations and clarifications… in this case “clarifying” fabrication to include procedures specifically banned elsewhere is not a clarification, but a rule change… which is perfectly okay, but should be noted as such and included in an updated Appendix E.

So to be clear… I think the ruling itself is great, but building a cohesive set of rules is a challenging process and a set of protocols have been established on the correct way to do it. Oh… and if they’re going to include brazing, they need to allow brass on the robot as it is a legitimate brazing material, or else they need to be more specific about what types of brazing are allowed.

I’ve had a great time examining and interpreting robot rules for about 15 years now… and appreciate the challenge in ‘getting it right’. GDC does a great job, but deserves a bit of a poke for this one… and they shouldn’t wait for next year to set the rules straight. They should do it right, and do it now.


Agreed 100%. Also agree with your earlier post that this QA response is more than a bit strange.