Velcro tread

[timytamy]

I was thinking about hi-traction treads, and was thinking, how about (hook) Velcro? Roughtop top treads are a very mild form of Velcro (they certainly pick up fluff), and the strong shear strength and (relatively) low peel strength would make them work on wheels (albeit probably very inefficiently) and have amazing traction. I understand no-one is the GDC and can't comment on 2015 rules, but for this discussion let's consider the 2014 manual.

A brief search found two relevant rules:

Originally Posted by [R6]

Traction devices may not have surface features such as metal, sandpaper, hard plastic studs, cleats, or similar attachments. Traction devices include all parts of the ROBOT that are designed to transmit any propulsive and/or braking forces between the ROBOT and FIELD carpet.

Originally Posted by [G10]

The following actions are prohibited with regards to interaction with FIELD elements (items A-D exclude BALLS):
A. grabbing,
B. grasping
C. grappling
D. attaching to,
E. damaging,
F. becoming entangled

[R6] doesn't explicitly ban Velcro, but It could still be rulled illegal as a "similar attachment"

[G10] is more interesting. I think you could possibly get around the "damaging" part if you chose your strength of Velcro wisely, but "attaching to" is not as clear cut. Potentially you could argue that it's just a stronger tread, or use something like cheaper velcro or dual-lock that has a different (and maybe slightly weaker) adheasion method. But I'm doubtful if you could confidently get an inspector/referee to allow it.

My team certainly won't be using Velcro, the 2014 rules isn't clear cut enough and it's doubtful that the 2015 ones will be. However I was hoping to start a discussion as to alternative treads and what benefits/properties affect performance, ie is there anything other than CoF that you look for in a tread?

[T^2]

I doubt Velcro would make a good tread even if it were legal, for 3 reasons:

1. Its durability and stickiness decrease drastically with use.

2. It would generate a ridiculous amount of rolling resistance.

3. It might make turning a lot more difficult (not sure about this one).

[Jay O'Donnell]

We actually have two drop down traction wheels on our robot that are treaded with Velcro (we ran mecanum until offseason so we had them for pushing). We had no problems all year with inspectors based on the rules you provided. I wouldn't say they were better than any other tread when it came to driving, but once we had them down on the floor it was pretty hard to move us.

[EricH]

I'm going to comment here based on past history. I think some folks will find this interesting.

Prior to 2003, traction was "anything goes". Metal treads, metal studs, you name it. In 2002, with a high-traction pushing war, many teams had some form of metal cleats on their drivetrain or lock-down devices. The most famous? 71, with their file-card drivetrain. But after every event, the carpet was just about trashed. (Especially where 71 had been driving if they'd hit resistance.)

Fast forward to 2003. That year, a rule came into effect that no (traction system) metal could contact the carpet. It's evolved a bit, and in 2014 showed up as R6 and G10 together.

Here is the intent of the rule(s): Do NOT damage the carpet by robot design or by gameplay if you can avoid it. Metal (and the other items listed) can be very damaging to carpet.


Now, Jay, the inspector would certainly pass you. There's no part of that rule (R6) specifically prohibiting hook-side Velcro. That's a correct ruling. The referees probably should not have under G10D. And that's because Velcro doth most definitely attach to cloth/looped stuff/other items of that nature (including carpet). It's Velcro. That's what it does. The field is held down by industrial-strength Velcro--if you've ever been around for field setup or teardown, the fields come with HDPE sheets for moving items around on the carpet without getting the Velcro to attach (or for sliding in to get the Velcro detached!). And it's always fun getting the side rails down, something on the order of "OK, everybody pull!" with a large group standing next to the rail.



If any team were to use Velcro on their wheels to increase traction, I would have the following recommendation: Q&A as soon as you decide to do that. Then... if it's a definite "no", take the Velcro off. If it's a definite "yes", bring a copy of the Q&A with you just in case somebody says something. If it's a "We cannot comment" or similar, print it out, grab the LRI and Head Referee and a spot on the practice field as soon as possible on Thursday, and ask them, demonstrating the use of said wheels on carpet. That way, you know early, and they're aware in case someone else complains later that it's illegal (and they can say "We already checked, they're OK, we'll pass that concern on for next year").

[Joe Ross]

Originally Posted by EricH

It's evolved a bit, and in 2014 showed up as R6 and G10 together.

To the point about evolution, prior to 2011, Velcro was specifically mentioned as not being allowable. Since someone specifically removed it, in the absence of other input (such as Q/A) and field damage, it should be allowable.

[Jon Stratis]

Originally Posted by EricH

Now, Jay, the inspector would certainly pass you.

I wouldn't be so certain of that. As an LRI, i would have serious reservations about velcro on the drive train, and what it could do to the carpet. As you pointed out in your excellent history/background around the rule, the intent is to avoid damaging the carpet, and I would strongly suspect that velcro in a drive train could cause some significant damage to the carpet over the course of the day. Just think of situations like a pushing match... will the velcro let go and allow the wheels to free spin on the carpet, or would the motors stall? Does the answer depend on the number of CIMs in the drive train, and high vs low gear? How would scrub from the wheels when the robot turns affect the carpet?

Personally, if a robot showed up with velcro on the wheels, I would probably grab the FTA and head ref and get their opinions - they're the ones who would have to deal with the consequences should the velcro cause issues on the field. I don't think the ruling on this is as obvious or certain as you may think. Definitely one for the Q&A if you're thinking of using it!

[EricH]

Originally Posted by Jon Stratis

I wouldn't be so certain of that. As an LRI, i would have serious reservations about velcro on the drive train, and what it could do to the carpet. [...]
Personally, if a robot showed up with velcro on the wheels, I would probably grab the FTA and head ref and get their opinions - they're the ones who would have to deal with the consequences should the velcro cause issues on the field. I don't think the ruling on this is as obvious or certain as you may think. Definitely one for the Q&A if you're thinking of using it!

Under the rules, as written, you'd probably have to come up with a rule other than R6 to stop them. Knowing the intent, you'd probably have some chance, but if a team really got picky on you, you'd probably be getting some input from Al just to keep the team happy. (I'd guess that Al agrees with you on not allowing them.)

Which is why I suggested the team grabbing the LRI and Head Ref (forgot about FTA) and some practice carpet if Q&A gave an unclear answer. If the Head Ref points out that the robot is going to be disabled every single match unless something changes (G10), the LRI's take suddenly becomes even more valuable. Conversely, if the team is able to prove that they meet all the rules, everybody is on the same page about it from the get-go, and no further discussion needs to happen (unless they start damaging the field).

[Michael Hill]

Originally Posted by EricH

Under the rules, as written, you'd probably have to come up with a rule other than R6 to stop them. Knowing the intent, you'd probably have some chance, but if a team really got picky on you, you'd probably be getting some input from Al just to keep the team happy. (I'd guess that Al agrees with you on not allowing them.)

Which is why I suggested the team grabbing the LRI and Head Ref (forgot about FTA) and some practice carpet if Q&A gave an unclear answer. If the Head Ref points out that the robot is going to be disabled every single match unless something changes (G10), the LRI's take suddenly becomes even more valuable. Conversely, if the team is able to prove that they meet all the rules, everybody is on the same page about it from the get-go, and no further discussion needs to happen (unless they start damaging the field).

Is the burden of proof on inspectors to find a rule to disqualify or on the teams to prove they are compliant? Historically, it's been the former.

[cgmv123]

Originally Posted by Michael Hill

Is the burden of proof on inspectors to find a rule to disqualify or on the teams to prove they are compliant? Historically, it's been the former.

Everything I've heard has said it's always been the latter.

[EricH]

Originally Posted by Michael Hill

Is the burden of proof on inspectors to find a rule to disqualify or on the teams to prove they are compliant? Historically, it's been the former.

Correct. However, in this case, the suggestion to have the officials check (given that Q&A does not give a clear answer) is so that the LRI (who right now does not have a clear rule to disqualify that he can enforce) and the Head Referee (who does have a rule that can be enforced) can be on the same page with a particular implementation. It also allows for a more reasonable discussion than if the Head Referee simply disables the team in their first match and sends them back to inspection--by the team coming to the LRI and Head Referee and saying "We have a Q&A ruling on this design that is vague, and the rules are vague, can we get a check on this?", the team makes it clear that they want to work with the event staff to be able to compete, and the LRI and the Head Referee are on the same page going forwards.

Now, there are some items where a team does have the burden of proof that they are legal, should an inspector challenge them on it. Namely, electric solenoid actuators (for power rating), servos (same), and pneumatic components (pressure rating, compressor specs, and the like). If an inspector challenges, you need to have the documentation, or be able to produce it before your next official match, or the inspector may assume the device is illegal and require it to be disabled. But the inspector does need to say something... (or you could just show him the item and the paperwork).

[Jon Stratis]

Originally Posted by EricH

... the LRI (who right now does not have a clear rule to disqualify that he can enforce) ...

Eric, I'm curious what you consider "enforceable" in the rules. If the LRI rules that velcro is a "similar attachment" as metal, sandpaper, hard plastic studs or cleats, then why isn't it enforceable by the LRI? I will point out section 5.5.2 of the Tournament section of the rule book:

At each event, the Lead ROBOT Inspector (LRI) has final authority on the legality of any COMPONENT, MECHANISM, or ROBOT. Inspectors may re-Inspect ROBOTS to ensure compliance with the rules.

That's not to say that the power goes to our heads, and every LRI I've talked with has the approach of working with the team to get them on the field... but if I point to something and say "that's not legal", that's all the rules say is needed. At that point, the issue is fixed to my satisfaction or the team doesn't compete. Personally, I always follow up any ruling with discussion, clear explanation, and build a consensus with the team on an appropriate fix that can be quickly implemented (and that's what I've seen all other LRI's I've worked with do). Decisions aren't arbitrary... but just because your opinion is different from my opinion doesn't mean I don't have the authority to make my opinion stick at an event I'm running.

In ALL cases of disagreement over robot legality, the burden of proof rests with the team. Not just some. Questionable situations are what the Q&A is for, and they are why I always make myself available to teams going to my competitions (any anyone on CD, of course) as much as possible - I'd rather they ask me to look at something before they bag the robot, than run into a problem after they get to the competition. Even if I can't give a clear-cut answer and have to direct them to the Q&A, I can often help them understand what rule(s) the issue really points to, and how best to word the question to get a good answer (one better than "see R15" or "we cannot comment on specific design").

At an event, the LRI will do everything possible to get the team to pass inspection, and that includes bringing the issue to others for opinions in order to get his mind changed. Whenever I find a problem with a team, the very first thing I ask myself is "how do we make this legal?"

[EricH]

Originally Posted by Jon Stratis

Eric, I'm curious what you consider "enforceable" in the rules. If the LRI rules that velcro is a "similar attachment" as metal, sandpaper, hard plastic studs or cleats, then why isn't it enforceable by the LRI? I will point out section 5.5.2 of the Tournament section of the rule book:

And that's the part that's going to get an awful lot of complaining. Metal and hard plastic are hard (and possibly sharp), sandpaper is abrasive. How is Velcro, which is a rather soft plastic, a similar attachment to metal or sandpaper? This is what the teams will contend, if they want to argue the ruling. Velcro is neither abrasive nor hard, and as Joe pointed out, was removed from the rules in question and thus, by someone with some knowledge of that fact, could be argued to be intentionally omitted from said rules and therefore legal. Given that, it's going to be very difficult to enforce without looking arbitrary--or pointing out that you're simply preventing the team from running afoul of G10, which usually isn't under the LRI's enforcement without the Head Ref sending a team there.

Hence getting the Head Ref involved early. (This will also serve notice to the Head Ref and FTA to watch that robot for field damage.)



Of course, there's the obvious result of this thread to consider--I'm guessing the GDC makes a note to include Velcro in the R6 equivalent next year, making the discussion moot.


(To some extent, I'm playing devil's advocate here. I agree that the LRI would generally be able to enforce it. Just looking for all the loopholes a team might possibly try to use to justify this use of Velcro, and ways to block them.)

[Brandon Zalinsky]

To clear up the facts about 1058's drop-down velcro drivetrain. (you can see it in this video at 1:23 and 1:43):

It is two piston-actuated, drop-down wheels driven off the same axle that drives the rear mecanum wheels. They pivot on swing arms and lift the rear mecanums off the ground. The wheels are 6" Andymark Plaction wheels treaded with commercial-grade (I don't know which product exactly) Velcro. We planned to have the drop-drive on for our first competition, the UNH District Event, but we only ended up bringing a whole bunch of pieces that never made it on the machine. It is an auxiliary drive, and by no means has to be on for the robot to drive well. At UNH, we talked to one of the inspectors about the legality of the wheels and showed him our Velcro-treaded wheels. He got a good laugh and said he was OK with putting it on if we had time at the competition. The same thing happened at Northeastern University District Event, with the same results. We then had the system on for the New England Championship event, and made it a point to show the inspectors that we had the Velcro-treaded wheels. They were ruled legal. The inspectors even called us back to re-measure our bumpers, as there was a question regarding to when the wheels were activated. When the robot tilted forward, the inspectors made sure that the front of the bumper did not dip below 2" from the floor. They passed without modification, and we continued competing.

I hope this cleared up any questions you may have had regarding 1058's use of Velcro in 2014.

[Roger]

I have no definitive opinion either way about using Velcro wheels for FRC, but as soon as I saw the question I was thinking of a game (with much lighter robots) that involved a carpeted floor curving up a wall that the robots would have to drive up and around.

[Andrew Schreiber]

Originally Posted by Jay O'Donnell

We actually have two drop down traction wheels on our robot that are treaded with Velcro (we ran mecanum until offseason so we had them for pushing). We had no problems all year with inspectors based on the rules you provided. I wouldn't say they were better than any other tread when it came to driving, but once we had them down on the floor it was pretty hard to move us.

From my memory, you added it at NEDCMP. Dana Henry, the LRI, did not notice them. I mentioned the wheels in passing to him at Blitz and he made it fairly clear that he would NOT have passed them. Nor would I were I to inspect that robot. (In fact, I recall questioning it at NEU when you guys mentioned you were planning it)