Tank Treads

[MachineSMMC]

I am looking for some opinions on the rule <R08>

<R08> ROBOT wheels, tracks, and other parts intended to provide traction on the FIELD 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.

So, is it legal to use a timing belt with the teeth gripping the carpet? I think this is legal because the teeth are not attachments.

Thoughts?

[karatekid]

I think it depends on how sharp your teeth are and what they are made of. Rubber "teeth", like on tank treads, should be fine. However, if you were to put in sharpened studs, they would consider that illegal. Hope this helps.

[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.

[Al Skierkiewicz]

Originally Posted by devodl

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

All of the answers below are general responses. More specific responses would require actual part numbers or pictures.

In general, metal tracks that have rubber treads might be allowed if the metal has no possibility of ever contacting the carpet or exuding lubricant that would stain or otherwise damage the carpet. This might also include wire reinforced tracks where the wires either begin exposed or through wear break out of the belt and contact the floor. Inspectors are not the only officials that have input on this.

Hard plastic is just that. Something that when you feel it you think "That's really hard, I bet it is going to rip some carpet!" This comes from teams adding plastic studs to track or wheels to give extra grip in past competitions.

Other attachments is anything that gives extra grip to the original material, be it aluminum cleats, nylon screws, abrasives, sand, file cards, wire brushes, etc.

[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"?