Velcro tread

[nuclearnerd]

A question for those condemning velcro treads (from someone who's never used them): Are you sure velcro will damage the carpet? I am under the impression that velcro releases by uncoiling the plastic hooks not tearing the loops (if it tore the loops, it wouldn't be very reusable would it?) Even if the velcro tore away some of the loose fuzz, I can't imagine it would be much worse than the reams of carpet remnants we dug out of our (KOP-wheeled) bot this year!

MamaSpoldi - that's incredible! I don't understand how any thoughtful judge could rule that a rubber pad were any different than a stationary rubber wheel.

[Jon Stratis]

No, I'm not sure it would, but the concern is that it would. I had an old rain jacket with velcro straps that let you tighten the wrists, and over time the velcro really tore up the wrist part where there wasn't any loop side.

The point isn't whether it's legal or not... no one here can say definitively either way. It's questionable enough that a team could get different rulings at different events if they don't ask on the Q&A.

[EricH]

Originally Posted by Jon Stratis

No, I'm not sure it would, but the concern is that it would. I had an old rain jacket with velcro straps that let you tighten the wrists, and over time the velcro really tore up the wrist part where there wasn't any loop side.

Same here, jacket and all.

Sure, the loops won't necessarily give way right away (same for surrounding fabric. But it doesn't take long (say, a few years for a jacket)--call it a few hundred attach/detach cycles--for wear to show up, even under normal use like that. Now consider a robot with industrial-strength Velcro as its tread material. It's "attaching" for at least a few cycles a match, and if it's slipping in a pushing match, you're dealing with a very, very fast cycle--might hit several hundred in one spot in a couple of matches if you push in the same area. There goes the carpet. (For other similar items, see "HiGrip in powerful drivetrain slams wall in auto and keeps going". That automode ended with a hole clear through the carpet!)

[nuclearnerd]

Originally Posted by EricH

(For other similar items, see "HiGrip in powerful drivetrain slams wall in auto and keeps going". That automode ended with a hole clear through the carpet!)

OK, so then we are already explicitly allowing wheels that damage carpet. (they practically all do). I frankly can't imagine that "industrial strength velcro" will do any additional damage to "industrial strength carpet"

Perhaps I can suggest, any team wanting to experiment with velcro treads should do a controlled experiment. Find a way to measure carpet damage, and measure the difference between velcro and HiGrip (or other treads) under identical circumstances. Bring the results to competition to show the judges. Use the power of science!

[Al Skierkiewicz]

How about we look at this in a practical light. The velcro has a distinct adhesive property based on matching a particular type of "male" and "female" material. The strength of that adhesion is proportional to the mated area of the material. When mated with material other than that for which it is designed, bad things occur for both materials. Additionally, when it does produce friction with the floor, the force needed to pull it along the carpet is also very high. While everyone has admitted that the "male" velcro does pick up fluff, remember that it does not give up that fluff readily. At some point, (within minutes I suspect) the contaminant will have reached a point where the material is filled and all friction is lost.
In the case of wheels, the mated surface area is quite small, less than 1 in^2. in most cases. I would suspect that the coefficient of friction to be quite small.
What would determine carpet damage in my mind is watching the robot drive across the carpet. If it leaves a visible trail, I would say it is damaging the carpet. If it picks up a considerable amount of fluff in a short driving session (say one match), it is also damaging the carpet. In this case you will have a harder time with the FTA and Field Supervisor than with the LRI. They can prevent you from playing until you correct the problem.

[EricH]

Originally Posted by nuclearnerd

OK, so then we are already explicitly allowing wheels that damage carpet. (they practically all do). I frankly can't imagine that "industrial strength velcro" will do any additional damage to "industrial strength carpet"

The HiGrips in question were immediately removed from "damage-causing" condition. As I recall, they started by adjusting their automode, and maybe had some other tweaks. This would probably be a little more difficult with Velcro, partly because it would involve removal of the adhesive as well as the Velcro itself.


For the rest, see Al's post. I can see where damage would be coming from, having helped with field teardown (and thus the field anchor velcro) on more than one occasion.

[Michael Hill]

I'm confused, so have teams used it successfully? If so, and it didn't cause damage tithe field, why is this even an issue. Please stop speculating on whether damage will occur or not. Let teams try it, and if it causes damage, then it's a problem, but don't stifle innovation in the name of it potentially causing damage. It could work perfectly fine, but without testing, we won't know.

[EricH]

Originally Posted by Michael Hill

I'm confused, so have teams used it successfully? If so, and it didn't cause damage tithe field, why is this even an issue.

Team(s) used it--but, we haven't heard from the FTA(s) involved, or the head refs, that it did or did not damage the field. Various LRIs have stated (Al in particular, pay attention when Al talks about legality on robots) that it would not be allowed through inspection due to the high risk of carpet damage. And, as it violates the rule against attaching to the field, the referees can shut it down regardless of whether it damages the field--it merely needs to attach to be in violation. (Velcro, as I'm sure you're aware, is very good at attaching. And detaching under sufficient force, but that's not under consideration here.)


Remember: It's not all that uncommon for something to slip past the officials and only be caught later, when another set of eyes looks at the problem. Should it be highly unusual? Yep. Is it? Not really.

[Michael Hill]

Originally Posted by EricH

Team(s) used it--but, we haven't heard from the FTA(s) involved, or the head refs, that it did or did not damage the field. Various LRIs have stated (Al in particular, pay attention when Al talks about legality on robots) that it would not be allowed through inspection due to the high risk of carpet damage. And, as it violates the rule against attaching to the field, the referees can shut it down regardless of whether it damages the field--it merely needs to attach to be in violation. (Velcro, as I'm sure you're aware, is very good at attaching. And detaching under sufficient force, but that's not under consideration here.)


Remember: It's not all that uncommon for something to slip past the officials and only be caught later, when another set of eyes looks at the problem. Should it be highly unusual? Yep. Is it? Not really.

My issue is that it would be disqualified by LRIs for being a "risk". That is purely their baseless judgement call. Let's see some actual evidence that it's a problem before shooting from the hip and killing it before it even has a chance.

[cgmv123]

Originally Posted by Michael Hill

My issue is that it would be disqualified by LRIs for being a "risk". That is purely their baseless judgement call.

It's their job to make those kinds of calls. Are they supposed to pass every mechanism that looks unsafe because it hasn't hurt anyone yet?

[Michael Hill]

Originally Posted by cgmv123

It's their job to make those kinds of calls. Are they supposed to pass every mechanism that looks unsafe because it hasn't hurt anyone yet?

This isn't an issue of safety though...it's a completely different thing.

[cgmv123]

Originally Posted by Michael Hill

This isn't an issue of safety though...it's a completely different thing.

Same concept applies. The LRI is the final arbitrator.

[Michael Hill]

Originally Posted by cgmv123

Same concept applies. The LRI is the final arbitrator.

This shouldn't be the LRI's call. It's the Head Ref's field, let him/her determine if the team is damaging it.

[EricH]

Originally Posted by Michael Hill

This isn't an issue of safety though...it's a completely different thing.

Just to run this to ridiculous...

Suppose two higher-CG robots are in a pushing match. Neither has Velcro tread--but in a previous match, a robot with Velcro tread got into a pushing match and shredded the carpet near that area--but, due to the nature of Velcro damage, it wasn't spotted and covered. Now, suppose that one robot is winning already... and then the other hits the slick area left by the Velcro-bot and loses traction. The pushing robot now takes a huge power advantage, slams the pushee right through the slick area and to the wall, inadvertently getting under their bumpers and sending them over the wall into the nearest volunteer who doesn't have a chance to get out of the way. Is it still not a safety issue?


Part of any competition environment has to be that the playing area has to be kept as consistent as possible (unless the inconsistencies are specifically noted in the rules, etc., or otherwise accounted for). If the field (generic) is constantly getting extra wear due to one player, all matches after that player are getting an inconsistent playing area unless the grounds crew got in.



And you still haven't answered this: Velcro attaches to the field, which is specifically disallowed in the game rules. The head ref just sent the robot back to the LRI to get that fixed (even with NO damage to the field whatsoever, as determined by the Field Supervisor, the FTA, and the Head Referee). Can the LRI send the robot back out with no changes? Yes. Can the head ref immediately disable the robot prior to the match? Yes, and he most likely will.

[Max Boord]

Originally Posted by EricH

Just to run this to ridiculous...

Suppose two higher-CG robots are in a pushing match. Neither has Velcro tread--but in a previous match, a robot with Velcro tread got into a pushing match and shredded the carpet near that area--but, due to the nature of Velcro damage, it wasn't spotted and covered. Now, suppose that one robot is winning already... and then the other hits the slick area left by the Velcro-bot and loses traction. The pushing robot now takes a huge power advantage, slams the pushee right through the slick area and to the wall, inadvertently getting under their bumpers and sending them over the wall into the nearest volunteer who doesn't have a chance to get out of the way. Is it still not a safety issue?

No but you may want to ban all types of wheels as this could happen just by having a robot with traction wheels and a robot with slick wheels getting into a pushing match.

Originally Posted by EricH

And you still haven't answered this: Velcro attaches to the field, which is specifically disallowed in the game rules.

How exactly do you get traction without attaching to the field carpet?