Wheel Wear

[Andrew Y.]

ok so we are all going to test our bots. Some of us dont have the field surface and we may be practicing on our shop floor. soo heres my questions

how do yall think first will deal with worn wheels due to testing?

[CDH Jeff]

In the rules it says <R06>"The surface tread of the ROVER WHEELS may not be modified except
through normal wear-and-tear."

[Geshamakina]

The main question is...how are they going to be able to tell wether it was through "normal" wear-and-tear??? some bots may wear out their wheels more or not at all, and we all want any added friction. How are they going to be able to tell if it was done on purpose or not??? honesty is needed here.
:p

[Iceman1330]

I'll also direct you at <R06>

"The intent of this rule is that the ROVER WHEELS be used in as close to their “out of the box” condition as possible, to provide the intended low-friction dynamic performance during the game"

Anyone hoping to wear their wheels before the competition as an advantage for traction needs to give themselves an ethics check. FIRST rules, as we all know, are about intent, not lawyering.

In your case, it might be unavoidable wear and you might not have the budget to replace the wheels. However, if you know wheel wear is going to be an issue, pick up some more if you can to comply with the intent of the rule.

[Andrew Y.]

haha gotcha... man i need to change my train of thought. in FSAE racing, its allabout bending and pushing to rules to get MAX performance lol:yikes:


hmm, we only have our shop space to run. Now its not as rough as sidewalk concrete but its not the smoothest surface ever. And i know ALOT of teams that only have a parking lot to run...:ahh:

[Prontopwnage]

lolz you could wear your wheels down so its really rough and you would gain a bit of traction but not much...:eek:

But this really a techicality... so if you do this you can get skrewed over by the judges... and have to switch wheels, so... idk

[Hanna2325]

I'm sure what ever u guys are doing will be considered "normal" but if ur planning on some intense driving practices u probably could order more wheels just to be safe.

[Otaku]

If you guys want a good surface to test on, I suggest some clean tile flooring that is in most schools inside. We had a sample of off-brand regolith and compared it to our tile flooring and got similar numbers.

I see no reason why a school wouldn't have tile somewhere.

If it's an issue of "there's other people there", just wait until after they've left and then go use the room. Just make sure to leave it in the same condition you used it in -- wouldn't want to get in some trouble because you messed it all up. :yikes:

[JesseK]

If you are trying to wear your wheels for more traction at a competition: good luck! You will more than likely wear one more than the others, which means one of the wheels probably will not touch the surface. On top of that, it's fairly difficult on this field to keep all four wheels with the same amount of traction if you modify them. (A mu difference of 0.01 with these wheels is a +- 20% amount of traction...)

So, 'normal wear and tear' from your shop -- I wouldn't worry about too much. I'd imagine that the GDC expects that everyone will want to practice ahead of time and that not everyone has an ideal field to do so.

[Mike Wittman]

lolz you could wear your wheels down so its really rough and you would gain a bit of traction but not much...:eek:

But this really a techicality... so if you do this you can get skrewed over by the judges... and have to switch wheels, so... idk


I have to take issue with your "Skrewed over" comment. The judges and refs are there to uphold the rules not Skrew people over. As a matter of fact I find them to be very helpful to teams that don't satisfy the rules.

[Clayton Rogers]

If you guys want a good surface to test on, I suggest some clean tile flooring that is in most schools inside. We had a sample of off-brand regolith and compared it to our tile flooring and got similar numbers.

I see no reason why a school wouldn't have tile somewhere.

If it's an issue of "there's other people there", just wait until after they've left and then go use the room. Just make sure to leave it in the same condition you used it in -- wouldn't want to get in some trouble because you messed it all up. :yikes:

We tested on the school floors and got .25 co-efficient of friction and also tested on the actual surface and got .07. So we concluded that the school floor were several times stickier than the actual surface, but still very slippery and probably still good for practice. Also note that our school floors were not very clean and had some dust/dirt.

[Kyle Love]

This will more then likely come down to the head inspector (in many cases) at the regionals/Champs. "Normal wear" in my book, is light scratching of the tread area, that would resemble a razor slit. There should be very few side to side "slits" and a fairly constant diameter slit. These slits will be hard to be done without testing, because as some have found out, the slits tend to be spuratic and very inconsistent on the tread of the wheels. In a nutshell, I believe the only issues that inspectors will have, is with team who have altered their wheels, gracious professionalism will need to be used by teams to make sure that they do not alter their wheels to appear "more used" then normal.

[JesseK]

Mike is right, the judges will do everything in their power to help you get approved and out on the playing floor, that's why I love them.

I completely agree. They know that you've put 6 weeks of blood, sweat, and <sometimes> tears into the thing...so not being able to play at all is definitely not what they want. Between all of the available resources, you will somehow find a compromise and be able to play so long as you agree to their terms...which are always in my experience within what the GDC puts out.

1885's own example:
In Atlanta '08, on Friday a ref (who was also an inspector on Thursday) noticed an angle connection on our radio modem serial port. We put our controller 1.5" from the rear of the robot. No big deal we thought, since we could put an angle on the radio modem connector and connect the radio while staying within the dimensions. Little did we notice that the connections themselves were not allowed to be modified in ANY way, which the ref pointed out to us with the rulebook. We made it through 2 regional competition inspections and Atlanta inspections without a single word to us, so our plea to the head ref in Atlanta was for us to keep the angle connector on. His compromise in return was that we were not allowed to dispute a match in which our robot stopped responding due to communication issues, as was his interpretation of the intent of the rule. We were allowed to compete if we agreed, which we did. Believe me, we're triple checking our compliance with the specifics this year!

[907eyci]

well for testing we had a good idea of a hockey areana.. but we are kinda in Canada so they ant soo hard to find up here.

[CraigHickman]

I have a serious problem with some of the logic presented in this thread. A true FIRST student would hear that the wheels gain traction as they wear, and rather than thinking pushing the rules to the max, they'd see that this REALLY means. Folks, design your robots to allow easy swapping of wheels. If FIRST sets a max amount of wear, you don't want to have to take your entire robot apart to change out a few wheels.

[nuggetsyl]

We have not tested our wheels out yet on the Robot but i really, really hope the wheels do not wear down as quick as people say they do. First is expensive enough with out have to have a ref demand you change your wheels out every regional.

[DonRotolo]

Our experience so far is that little bits of dirt and crud do cause some minor wear of the wheels. This is made worse by the fact that they spin so easily from excessive acceleration. The marks made tend to be along the length of the tread and not the width, but by no means would I say that they wear 'a lot' - just some visible scuffing.

In our tests on the terrazzo floor (in the hallways), waxed vinyl tile floor (in the cafeteria) and a piece of "official" pebbled regolith, the regular floors are almost twice as grippy. We pulled on a 4-wheel test platform weighing about 30 pounds with locked wheels with a spring scale. We found a small (under 20%) difference between sideways pulls and longwise pulls, so those transverse CoF numbers did not pan out for us. Also, the difference between static friction and sliding friction is measurable at about 20% (sliding being less, of course).

The custodial staff was not amused by the scuffs in the school floors the wheels left. We promised to not do it again, and they forgave us.:)

[Sunshine]

First time we tested the wheels on a robot and the correct flooring we saw wheel marks left on the FRP. Pretty hard to avoid this when you are doing real testing. Granted, I was trying to show students how easy it was to push robot around when the wheels are spinning. (We could even smell the plastic on wheels at one point)

I guess my suggestion (from the above experience), use caution; do not do extensive testing and learn from others or get extra wheels.

I'm glad we got our 10 wheels prior to them running out. :ahh:

[keenanmolner]

So, if the inspectors at the regional deem the scrapes on the wheels beyond the normal wear and tear expected, and they want us to change our wheels, will we be responsible for providing the replacements or will they have wheels to give us?

For example, if we think the wheels have gone through normal wear and tear, it is logical that we would not have a full set to replace the robot with. But if an inspector says that they are too damaged, what do they want us to do?

FIRST has not said a point to which the wheels will still be usable, so what should our team expect?

[Mr. Freeman]

This might clarify things a bit.

http://forums.usfirst.org/showthread.php?t=11108

Inspectors will examine wheels for treads that have the potential for increased traction on the field or damage the field surface.

The list of items that will be available to teams at events has not yet been released.

[Andrew Y.]

I have a serious problem with some of the logic presented in this thread. A true FIRST student would hear that the wheels gain traction as they wear, and rather than thinking pushing the rules to the max, they'd see that this REALLY means. Folks, design your robots to allow easy swapping of wheels. If FIRST sets a max amount of wear, you don't want to have to take your entire robot apart to change out a few wheels.


in no way am i saying i will tell my students to push the rules, nor do i intend to wear the wheels down. I dont see anyone on this thread saying "im gonna wear the wheels down" Part of how i was taught was to know everything thats gonna happen and be prepared for it. I just wanted to get others feels on if i should get some extra wheels, and how it may be handeled.

[EricH]

Part of how i was taught was to know everything thats gonna happen and be prepared for it. I just wanted to get others feels on if i should get some extra wheels, and how it may be handeled.If you aren't sure your wheels will pass, get extras. If you don't need them, another team (who isn't on CD or reading the Q&A or manual) will.

[Wayne C.]

I was just looking at that forum post where the "potential for increased traction" will be assessed by the referees. I am not happy with that answer

Here's why-
1. there has been an epidemic of inconsistency in inspections among the regionals and the championships. Since the inspectors/referees are volunteers, often inconsistently trained and always subjective, what is easily allowed in one region may be rejected at another

2. any scratching on the wheels offers a "potential for increased traction" .

3. no recourse is clearly stated for the team who has wheels that are rejected. Are the expected to rip the bot apart on the spot and put on new wheels? Where do these wheels come from? Are the teams expected to put out hundreds of dollars in changeout wheels that they may not be required to use?

We have been driving a nice robot base since last weekend. We prepared a waxed school hallway by sweeping and dry mopping the floor before the robot ever hit it. To the best of my knowledge this is the type of substitute the GDC was proposing if a team didn't have an official practice surface.

Now, after 3 hours of driving around we are noticing scratches and scores from dirt picked up by the wheels. I am sure similar scratches will also happen from metal flakes and such shed by the robot in any situation. Shoes track enough grit to be an issue, especially when we have snow days and salt is all over the place.

So I ask- What is considered NORMAL WEAR? An answer of "the refs will decide" isn't satisfactory.

How about the experts developing a technique for refinishing scratched wheels so they can be used if they experience this "normal wear"? If this traction is such an issue that is the only way I can see that assures that all robots hit the field in the same condition.


WC :cool: :cool:

[JVN]

Some more food for thought:
I originally thought "no big deal, this won't affect us because we have a large chunk of glassliner." However I was surprised to find out that the wheels wear a noticeable and significant amount even if they spend their entire life on the "regolith".

We've got wheels that have never been driven on anything but a regulation surface, and I'm worried an inspector would dub them "illegal".

Since these wheels were made of delrin I foolishly assumed we would NOT need to replace them. ("Durr... how much could they wear down!? This year we don't need to worry about changing treads!") Maybe we need to tweak our drive a little bit to allow for easier swaps...:rolleyes:

-John

[Joe Ross]

We've been running our wheels on concrete and they have accumulated a significant amount of dust and grit. However, when we cleaned them with a wet paper towel, they feel as good as new.

[Andy L]

Just from my experience, wiping them down with a rag or paper towel before and after every use keeps them pretty clean

[Wetzel]

We have been running our test chassis on some sheet plastic that we think is similar to the official stuff. I'll take a close look today, and see how well the wipe test works, but our wheels have been getting a scuzzy look, kind of like what your mouse will accumulate. No idea if that helps or hurts traction, but it sure is gross!

We have about 10 hours of drive time on those wheels now, hopefully we won't have to go through more than one set before ship. :ahh:

Wetzel

[Joe Ross]

Update 5 includes a reference to Restoring Damaged Wheels (http://www.usfirst.org/uploadedFiles/Restore%20Damaged%20Wheels.pdf) which says that you can clean the wheels with scotchbrite or light sandpaper until your fingernail no longer catches on ridges or burrs.

[meastman]

Update 5 includes a reference to Restoring Damaged Wheels (http://www.usfirst.org/uploadedFiles/Restore%20Damaged%20Wheels.pdf) which says that you can clean the wheels with scotchbrite or light sandpaper until your fingernail no longer catches on ridges or burrs.

Thanks for this info. This will be helpful come competition.

[Wetzel]

Our wheels look just like the normal wear and tear picture in the restoring damaged wheels document. A damp napkin went a long way towards restoring it.

Wetzel

[Wayne C.]

Update 5 includes a reference to Restoring Damaged Wheels (http://www.usfirst.org/uploadedFiles/Restore%20Damaged%20Wheels.pdf) which says that you can clean the wheels with scotchbrite or light sandpaper until your fingernail no longer catches on ridges or burrs.

yaaaay !!!! Hallelujia and amen....

Thanks

WC