Re: The Game Floor
 

From looking at the rules and the video we think its the "Glasliner FRP"
but the bumpy or "rippled" kind.
In 10.2.4.1 the rules say "The wheels supplied in the 2009 KOP are very different from previous years’ kit wheels. The tread material is Celcon M90, and has the following coefficients of friction on white, rippled fiberglass plastic sheet" then states the coefficents.

haven't found a dealer forsure yet but there are places in the states that sell it. dont no about prices yet. any one no where to buy?

Re: The Game Floor
 

we know** its "Glasliner FRP".

Re: The Game Floor
 

The floor material is a thin laminate pretty much exactly like the one you find on the walls of communal showers or in the kitchen or bathroom of a taco bell, the slightly bumpy white plastic stuff on the walls.

We found this stuff at our local Lowes (nice when your building materials are 1/2 mile from your shop) for about $28 per 4x8' sheet if I remember correctly.

-q

Re: The Game Floor
 

Classic model for friction does not depend on surface area.

maximum friction force F is given by the equation:

F=u*N

where u is the coefficient of friction between the two objects and N is the normal force between them.

in our case the net force that the floor is applying to the robot (the normal force) is the weight of the robot.

so:
F=u*W in our case.

so as you can classic friction does not depend on surface area.

if you were to model each wheel individually you would get a lower normal force (roughly the weight of the robot divided by the number of wheels) on each wheel so that N=W/n (W=total weight, n=number of wheels.)

so the force from each wheel would be F'=u*W/N

and we have n wheels so we get a total force of: F=F'*n=n*u*w/n=u*W

magic! :)

classic theory of friction breaks down in a lot of cases (for example spikes on a carpet), but should be very close to the reality in this year's game.

-Leav

Re: The Game Floor
 

Also....will adding a lot of weight really help you stop and move easier. I mean yes you will get more force from friction but what about F=ma. You will need more force to slow yourself down as well so having more weight wouldn't really do you as much good would it???

Re: The Game Floor
 

According to the classical model, your acceleration will not depend on the weight of the robot.

a = F/m = umg/m = ug.

However, extra mass will aid you in collisions.

Re: The Game Floor
 

Don't forget that extra mass will also help you drag the trailer around. I would suggest that if your robot comes in underweight you'll do well to ballast it up to 120 pounds so that the ratio of weight on the undriven (trailer) to driven (robot) wheels is minimized.

Jason

Re: The Game Floor
 

Under normal circumstances, the "surface area" is irrelvant to traction. Friction is proportional to the
normal force (that is the force perpendicular to the surface, usually the weight supported by the wheel.
You can calculate friction from the dimensionless coefficient of friction multiplied by the Normal force on the
wheel. Do remember that forces (including friction) are vectors.

As in past years, a driven wheel cannot impose greater torque than that which occurs just before the wheel
breaks traction. The ability of a drive train to supply more torque than this is not very useful, although
it looks like the there is an 18 inch carpet border which will yield quite different characteristics and some
serious pushing may still be possible around the edges.

The main difference this year is that with a coeeficient of friction of approximately 0.06 rather than the
typical 1.0 - 1.2 or so, the peak torques on the FRP will be about 1/6th of those of past years.

Having 4 driven wheels will increase your pushing force (and acceleration) because all wheels will be able
to push (before any of them start of to slip). As in past years, 6 wheel drives will still be useful because
with a raised center wheel, you will always have two wheels slightly off the floor (or with very low normal
force) and the effective wheelbase will then be about half that of a 4 wheel drive without the center wheels.
This may be quite important with the required wheels. Note that (assuming the supplied information is correct)
the transverse coefficient of friction of the wheel/FRP interface is more than twice that of the inline
coefficient. Do not assume that it will be easier to skid steer on this surface. It may actually be much
harder. You will have to do the physics and the math and it might be best to get some input from your engineering
mentors on this.

I think that some of the interesting challenges of this year's game comes from deciding which "rules of
thumb" to throw away and which ones to keep.

Re: The Game Floor
 

Our team is known for being overweight (lots of 8020 == heavy), I doubt hitting 120 lbs will be a problem :)

To writchie: Thanks! That makes alot of sense but I suppose it doesn't change anything. It looks like FIRST wants to make sure that this will be a slippery game with luck involved.

Re: The Game Floor
 

Speaking of the trailer, does anyone have any feedback on how easy it is to whip the trailer transversely? If the bot strafes sideways, how willingly does the trailer follow?

Also, here's a site with some sample pricing - hopefully you can find it cheaper locally:

http://www.frpshop.com/liner-panels-c-3_4.html

Maybe we'll get blue and pretend it's a water game....

Re: The Game Floor
 

We were told by another team that Home depot carries it for $13.00 a sheet. I hope this is true instead of that $28.00. It is really thin material used on bathroom walls so I don't see why it would be $28.00. We are planning on going tomorrow and buying 5 or 6 sheets.

Re: The Game Floor
 

Can I have a definition of incline friction vs transverse friction, please. I thought I was paying attention pre-season, apperentally not.

Re: The Game Floor
 

Inline friction is along the direction of the wheel's rotation (rolling friction), transverse friction is along the axis of rotation (sliding friction).

Re: The Game Floor
 

Like the real world, luck is always an element. I suspect, however, that luck
will be more involved with miraculous "shots" in the last 20 seconds by human
players. Changing the physics of the game, IMHO, makes it more a matter of
engineering than luck. As always, expect to see some amazing bots.

Re: The Game Floor
 

Chances are the one at H.D. is a thinner version with different surface which is why its less expensive.

Edit: The $28 4X8 panels are the .090 thickness, the $13 is most likely the .063 panels which are much thinner and more flexable.

-Mike AA