G28 Clarification - Air Powered Shooter

My team is discussing strategies for shooting fuel at a high rate. A google search for “Wiffle ball shooter” produces some videos of leaf-blower powered shooter, and we thought this would be a good solution (powered by a legal motor/in a legal fashion) However, there are a couple sticking points. The first, G28:

A strict reading of the rule would say that this strategy is illegal if the flowing air affects our launched fuel after it leaves the robot volume, as fast-moving air may tend to do. A less strict interpretation (possibly the intention) is that this rule would only affect FUEL units that are either uncontrolled or controlled by the opposing alliance.

The second sticking point is whether using air in this fashion is legal at all. A cursory search of the rules does not explicitly disallow this (as in whether a fan is a pneumatic device :p)

Thanks for your input. Please let me know if I missed anything in the rules that pertains to this question. We also intend to ask Q&A for clarification/intent when it opens.

Q&A this for sure, but where is the ambiguity? It says don’t use air to direct fuel outside of the robot. That is as straightforward as it gets. You are directing fuel, outside of the robot, using air. This isn’t a “strict reading of the rules”, it’s what the rule means. Can’t possibly be legal.

Unless you can figure a way to stop the air from the blower to stop at your frame perimeter while allowing the ball to pass through, I’d say it’s not legal.

Definitely a Q&A though.

Because the rule allowed for using air on fuel in your bot’s volume rather than ban air moving fuel entirely, it is reasonable to assume that the GDC had a reason to make this distinction. I can think of three reasons to use air to move fuel inside your volume

  1. A system similar to a drive-up bank tube, to move fuel through a path in your robot, presumably to your shooter.
  2. To agitate fuel in hopper to help it find its way to the shooter intake (like a lottery ball machine)
  3. To actually shoot the fuel. If this was their intent, they didn’t consider the final residual effect of air on the fuel after it left the volume, but perhaps that was an oversight.

Hoping they address this in the first update, rather than have to wait for the A to a Q.

Actually, I disagree, at least on the intent of this rule. I think this is trying to prohibit teams from creating anti-aircraft air cannons to shoot opponents’ fuel off-target.
Assuming that you aren’t sustaining a stream of pressurized air as the ball continues out of the robot, I think it’s very reasonable to think that this rule allows a ball to be shot from within the volume of the robot using pressurized air.


that would be impossible to inspect. what if they are running the shooter with no fuel? does a stream of air come out of the volume of the robot? if yes, then it violates the rule as written. At best, they get an LRI watching that they never play defense during every match.

Oh great, now when we drive our robot across the field and create a pressure differential in the surrounding air we’ll be penalized. :frowning:

If this was the intent of the rule, why would it say “direct or redirect”, and not just “redirect”?

I don’t mean to make this more black and white than it is, but it’s not a very ambiguous rule to me. People have an idea in their head what they think the rule is supposed to be for, and then they decide that something else explicitly prohibited by the rule actually isn’t, because it doesn’t match that notion.

The rule says you can’t direct (or redirect) balls outside of your robot with air. Can you provide an explanation as to how that isn’t what an air cannon is doing?

I would agree that the two primary reasons for the rule are:

  1. Prevent changing the coarse of fuel shot by your opponent via air.
    2a) Prevent a leaf blowing strategy to gather all the fuel on the floor to your own end of the field.
    2b) Similarly, blowing the 50 fuel coming out of the hopper that you aren’t catching in your bot to your end of the field.

The question is whether their intent was/will be to prohibit air powered shooters.

good point. That’s not “forced air” to a reasonably astute observer, but a fan is. what’s the threshold for forced air, and will i need an anemometer in the inspection station?

I think that is the key word. If you think that an air cannon, designed to launch balls, inside of it’s robot’s volume violates that then I will direct all of our speed controller fans towards your robot in spite.

My reading of the rule stands with many others. If you want to levitate whiffle balls inside the volume of your robot, go for it. You may not, however levitate whiffle balls outside of your volume. I think air cannons will be legal.

Enjoy. https://www.youtube.com/watch?v=9QBk1c5hfhE
I believe the cuts on the ball in the video are different than the FRC game pieces, but somebody should give this a shot - just for fun… or to win.

Point of interest - This has nothing at all to do with inspection. This is a Game rule (hence the G prefix), and is monitored by the refs, not the inspectors. From a practical perspective, your robot could be a giant fan (provided it’s safe, per R07) and it would pass inspection. But as soon as you turned on the fan to create a small tornado on the field to suck up balls, I imagine the ref’s would flag you.

All that said, I think it’s clear that the defensive used of forced air is illegal from that rule. As for a shooting mechanism… I won’t even pretend to know how it will be ruled. The penalty is pretty rough for it, though, so I wouldn’t want to take a chance on it without first getting an iron-clad Q&A response. And as the Q&A doesn’t open up for another 2 days, that’s too late for me to spend time or energy on pursuing such a design when I have other options that can be prototyped right now for shooting balls.

I agree that this certainly is what the rule was intended for. They didn’t want a repeat of some of the 2013 defense bots that just had a box fan sitting on a drivetrain, especially considering how much of a detriment that form of defense would be to the game overall.

However, just because that’s the intention doesn’t mean that’s what the rule actually says. An air cannon shooter is entirely illegal under this rule, whether that was the intention or not. Maybe FIRST just really, really hates air-based shooters (can’t blame them, honestly.)

continuing with your point of interest. Inspection is the determination that a presented design does not break any rules. We are inspecting that the robot meets all the R rules, and is not likely to break any G rules by design (G04 is the simplest example of one that we look for specifically on the inspection checklist). My point was that if it used for a shooting mechanism, but the shooter had no fuel, would forced air be leaving the volume of the robot? If so, it’s illegal. Overextension limited by software is usually fine, but we still notify the head ref that a robot is capable of breaking a rule on the field, and should be watched. That’s the best case i can think of for an air shooter. Legal for shooting, but not legal for defense, and the ref will be notified to keep an eye out.

Does anyone want to try to formulate the question so when the Q&A goes live there doesn’t need to be 3 non-answers citing “The GDC does not rule on design” ?

Does G28 preclude the use of air to affect the movement of FUEL that is inside the volume of the ROBOT?
When will air currents from a robot draw a G28 penalty?

Can already answer the first version. G28 does not preclude that use.

I’m having a hard time coming up with good wording, but something to the effect of using air to power the fuels motion offensively, but not defensively.

It could be clarified nicely if they have G28 not apply inside your own launchpad. This allows air shooters but not air defense.

Building off your second question (but still no easy answer), Where is the threshold between incidental air movement versus forced air movement.

I wonder if you were to design an air powered shooter with the end of the barrel working with a principle similar to a silencer… the air pressure would disperse well before the end of the barrel.

If you were to set fuel at the end of the “barrel”, there wouldn’t be enough air pressure to move it, or one could even demonstrate with paper there is no air current at the end of the barrel. Then you can demonstrate to the head referee that there is no air flowing outside of your robot, so G28 would not apply.

Look at the past checklists again. We do not inspect for game rules, nothing on the inspection checklist has a G number next to it. We won’t inspect for G04 this year, either. We will, however, inspect for R03. R03 is the Robot rules equivalent for G04. Many times in the past there has been this “doubling up” on the rules between robot and game rules for precisely this reason.

That’s quite an engineering challenge, but if you were to accomplish and demonstrate that, it would pass inspection as far as i can tell from the known rules.