Frictional Discrepancies

[SWIM]

Originally Posted by writchie

Perhaps you have discovered what's behind the "fish" clue

The transverse/inline ratio is a very critical parameter. If it's no where near the 2.3 advertised, then many preliminary design decisions about drive configuration will be dead wrong. We will try to confirm your findings as soon as we can locate the actual surface material.

It is possible that the ratio changes significantly with normal forces closer to 1/4 of the nominal weight of the robot due to the way the materials deform under load. It could also be that the type of backing underneath the regolith is a factor. The wheels are very hard and provide a very small contact area. If the backing is carpet (rather than a very hard material), there could be a small depression that presents differently in transverse and longitudinal directions. Your numbers may reflect light loading, before such effects manifest themselves. Based on your data it does looks like we will need to confirm the Mu values under a range of loads.

Does anyone know whether the regolith is over carpet?

Good catch.

From how I interpreted the rules, the entire field is covered in carpet, and the regolith is placed over that.

[Ozeaden]

One thing that my team found out is that if u wear down the wheels, you get better traction. With having a rough tire, it will give more of a stick to the flooring material. We tried it on one of our past robots and it worked really good. Just run the wheels on asphalt and run it down a bit. Its not against the rules at all.

[comphappy]

Originally Posted by Ozeaden

One thing that my team found out is that if u wear down the wheels, you get better traction. With having a rough tire, it will give more of a stick to the flooring material. We tried it on one of our past robots and it worked really good. Just run the wheels on asphalt and run it down a bit. Its not against the rules at all.

Read <R06> and I think you will find you are very wrong, and are now out $100 in usable wheels. This is intentional damage, which is explicitly prohibited by that rule.

[SWIM]

Originally Posted by comphappy

Read <R06> and I think you will find you are very wrong, and are now out $100 in usable wheels. This is intentional damage, which is explicitly prohibited by that rule.

I'm sure they'll get away with it, unless they're worn down to the point where it's obvious they were doing something far beyond just driving the 'bot around. But really, getting grooves in the tread shouldn't change the coefficients of friction much at all, since the surfaces are so hard.

If they do try and cheat to get more traction out of their wheels, that's a pretty rotten thing to do, but I don't think other teams will have to be too concerned with them somehow getting considerably more traction with worn down tread.

[Al Skierkiewicz]

Roughing wheel surface by driving on abrasive surfaces is already under discussion in inspection circles. Read R06 very carefully and watch the Q&A and Team Updates for anything that pertains to wheels. Conjecture in these fori is a personal opinion, the GDC is the official, last and final word.

[IKE]

Originally Posted by Al Skierkiewicz

Roughing wheel surface by driving on abrasive surfaces is already under discussion in inspection circles. Read R06 very carefully and watch the Q&A and Team Updates for anything that pertains to wheels. Conjecture in these fori is a personal opinion, the GDC is the official, last and final word.

If you get word on Policing procedure, that would be great. I know we are planning on buying extra wheels. Having practised drivers I feel will be really impoartant, and doing a full floor will cost around $2K. We have a large open smooth tile floor (like most HS cafeterias), but I am worried about picking up a little grit while pracitising.

[Peter Matteson]

Originally Posted by Al Skierkiewicz

Roughing wheel surface by driving on abrasive surfaces is already under discussion in inspection circles. Read R06 very carefully and watch the Q&A and Team Updates for anything that pertains to wheels. Conjecture in these fori is a personal opinion, the GDC is the official, last and final word.

I'm interested in how this comes out because I believe many teams will practice on carpet, tile or concrete floors because they can't afford a full field. This will leave many teams with interesting wear on their wheels when they get to their first regional.

Al, I don't envy the job of yourself or the other head inspectors this year.

[Al Skierkiewicz]

Originally Posted by Peter Matteson

Al, I don't envy the job of yourself or the other head inspectors this year.

Thanks, tell me again why I am doing this? This is one of many decisions your inspectors go through each year and which the GDC must answer. If you think the GDC just comes up with the game think again. My job is simple compared to the work they go through every year. Remember this game is the end result of months of work, testing and planning, and picking game pieces. And all done in secrecy so we all find out on the same day. Manhatten project comes to mind.

[Racer26]

In all honesty, I don't really think that it's going to be that big of an issue. Some teams who are less well off than some of us will only have the kit wheels to use, they wont be able to afford more, and as such they will have been practising with them on all manner of flooring (as they cant afford regolith). The wheels WILL arrive at the competitions in all different states of wear, and IMO, it won't matter. The surface of these wheels is so hard that being worn down wont have a significant effect. (I'm not saying there wouldn't be a measurable difference, just that we have so little friction to begin with, the miniscule gain won't be that beneficial). Course, I could be wrong too... someone with more money than me could compare coefficients on a deliberately worn down wheel (burnouts on asphalt?) to a fresh out of the box wheel and empirically prove whether its significantly beneficial.

[comphappy]

Originally Posted by Ozeaden

Just run the wheels on asphalt and run it down a bit. Its not against the rules at all.

This is what I am talking about, that is not the same as practicing on the cafeteria floor. If asphalt is all you have then so be it, but dont use it intentionally as an advantage i.e. "run it down a bit". As it says in the manual, think about the spirit of the rules.