Tank Treads

[devodl]

"I'm a bit fuzzy on the whole good/bad thing here. "
In Section 8.3.1 under R08 it states:

ROBOT wheels, tracks, and other parts intended to provide traction on the carpet may be purchased or fabricated (“traction devices” include all parts of the ROBOT that are designed to transmit any propulsive and/or braking forces between the ROBOT and the FIELD). In no case will traction devices that damage the carpet or other playing surfaces be permitted. Traction devices shall not have surface features such as metal, sandpaper, hard plastic studs, cleats, or other attachments. Anchors (i.e. devices that are deployed/used to keep one’s ROBOT in one place and prevent if from being moved by another ROBOT) shall not use metal in contact with the carpet to “stay put.” Gaining traction by using adhesives or Velcro-like fastener material is not allowed.

I believe the whole intent of R08 is to prevent damage to the field which is good but the Rule seems ambiguous and general and as a result overly restrictive when it comes to materials and design of a track.
Specifically my questions are:

1. Can you use a metal track that has "treads" (not "studs" or cleats")?
2. What is "hard" plastic? Is "hard" quantified using the Durometer or Rockwell scales?
3. What is meant by "other attachments"?

A conservative interpretation could be that you couldn't use metal or "hard" plastic chain but a "hard" rubber chain (or timing belt) is okay.

More importantly if you "fabricate" a track using commercial components then what qualifies as an "attachment"?

[ewoodring]

Like what devodl said, the GDC is trying to keep the field from being torn up. What you can do, is test your treads on a piece of carpet. If they tear up your carpet, they probably aren't allowed.

[devodl]

Agreed, but I am trying to understand what IS allowed.

If I make a track with "hard" plastic "cleats" that are "attached" to a track then based on R08 they aren't allowed for 3 reasons.
Even if the tracks don't damage the field whatsoever.

Heck, wheels can burn a hole in the carpet more easily than a track but I don't see ambigous, generalized restrictions on wheels in the rules.

[Matt C]

Generally, the rule against "hard" items against the floor is to prevent a popular practice "back in the day" of screwing drywall screws into skyway wheels to get cheap "cleats" that increased traction. (The carpet really didn't like that). Heck, I remember teams with full metal tracks back before this rule existed.

It came about after 2k2 with the "file card" anchor robots (plus a plethora of other carpet threatening devices). Anyone that took part in that year's competitions knows what the carpets looked like afterwards.

I think it comes down to:

Are there "hard" parts of the tread that are in contact with the carpet? ("hard" meaning anything but rubber or smooth slider-type plastic)

If so, I'd expect to have it thoroughly examined by inspectors on Thrusday.

[devodl]

I understand the intent of the rule (don't damage the field) but as an engineer I have difficulty accepting the ambiguous definitions. If two robots get in a shoving match they could damage the rug but their design was approved if they used rubber wheels.
Sounds like the only answer for tracks is: It depends on the inspector.
- "cleat" vs tread
- "hard" vs soft
- "attached" vs fastened, bonded, affixed

I know time is short but is there a process to get an official ruling prior to the competition?

[MrForbes]

I have not seen carpet damaged by rubber treaded wheels, even when robots get in heavy pushing matches. Of course I have not inspected all fields after all matches, but it's generally not a problem.

The rule is kind of ambiguous about what you can put on the robot, but it's intent should be obvious--if whatever you put on the carpet can damage the carpet, it's not allowed.

[MrForbes]

Originally Posted by devodl

I know time is short but is there a process to get an official ruling prior to the competition?

Ask on the Q&A.

http://forums.usfirst.org/forumdisplay.php?f=23

your team representative who has access to FIRST TIMS will need to get the password for your team to do this.

Suggest you read the questions and answers to get a feel for how it works, before you ask your question.

[devodl]

Thank you all for your responses, advice and opinions. I really appreciate it.

[Matt C]

For reference, stuff like THIS would no longer be allowed.

You could post pictures of what you intend to use.

[Al Skierkiewicz]

Just so everyone knows...
There will be carpet damage this year as robots trying to drive over the hump get hung up and one wheel spins on the floor as a team tries to get back in the game. The friction will cause some damage. The object is to minimize this for the enjoyment of all.
Al

[copperhead47]

i feel like "hard" plastic is something that has a tendency to shatter or fracture under pressure rather than bend

[devodl]

Is PVC "hard"?
Trick question: Which plastic on this chart is "hard"?
http://www.ides.com/property_descrip...sion-chart.asp

Of course it's not just the hardness of the plastic but the shape of the tread/cleat as well. Pointy "soft" plastic could cause more damage to the carpet than rounded "hard" plastic.

I can get around the "hard" plastic restriction but I'm stumped by the <R08> restriction on "other attachments".

Question
If I fabricate a track (<R08>) by fastening rubber treads to a chain, are the tracks ruled illegal (i.e. violate <R08>) because they have "other attachments"?

[EricH]

I doubt it. I've seen that kind of track since this rule became one of the "standard" rules.

"Other attachments" may refer back to the days before this rule was implemented, when teams used metal cleats, file cards, Velcro, and pretty much anything else they could figure out how to use as a traction device as a traction device. The carpet was constantly getting destroyed--it's a brand-new carpet each regional these days, and often doesn't show too much damage, but if you get a really badly torn up one at the end of the event, that was Thursday or Friday damage back in those days. If you had a really light day, that is.

[devodl]

Eric,
After re-reading this rule and some of the history that brought it about I think you are right. IMHO the "other attachments" phrase was added so that someone wouldn't go out and purchase a track and then pop rivet nasty carpet rippers to the track.

We kept carpet happiness in mind as we fabricated our track.

Steve

[Al Skierkiewicz]

So you know (and to keep this in mind) some regional events take place in gyms on hardwood floors and others take place on soft rubber composite floors. This rule is to prevent damage to the subsurface as well as the carpet. As to rubber tracks attached to chains, the answer becomes a yes and no. Yes if rubber is the only material that contacts the carpet and is not so aggressive the it digs into the carpet fibers. No if the attachment uses fasteners that also contact the carpet and have the potential for damage. For any contrivance used to move the robot, your design should not be one that leaves (or has a potential to leave) a residue or lubricant on the carpet.