How can we drive on this new floor?

[waialua359]

All this talk about effectively driving in these low-friction conditions. I would instead think of how the other parts in your kit can help you score DESPITE the poor driving controllability conditions.
Two things off the bat I saw in the kit and my concrete memory of team 25 in 2006. The lazy susan turet (or equivalent) and the camera.

[Dracco1993]

Yes, we thought about staying on the carpet but we decided it would be a bad idea because like he said, you would be an easy target and you will only be able to have at most 1/2 of your robot on the carpet.


P.S. How do you guy get thebluealliance name thing on there?

[Zyck_titan]

Mray

We thought of this, but our team decided not to do it Because;
A.) too much fabrication (time money etc)
B.) too much tuning to get it right (time)

But basically Thrust downward, with it you could dynamically control weight throughout the match, getting advantages of heavier btos and lighter bots, whenever you needed it.

[Andrew Bates]

What if your robot had two drive trains? One in the forward direction and one in perpendicular to the forward direction. You lifted one drive train to use the other. Kinda like the trucks that are made to drive on the road and railroad tracks.

[dmlawrence]

In theory, one could construct giant omniwheels using each Rover Wheel as one of the horizontal rollers...

<R06>
...The ROVER WHEELS must be used in a “normal” orientation (i.e. with the tread of the wheel in contact with the ground, with the axis of rotation parallel to the ground and penetrating the wheel hub)...

Originally posted by Branden Ghena

I think...R06 might disallow that, along with the general logistics of building giant omniwheels.

I believe R06 would only apply to the wheels being "used" - that is, the ones touching the ground. The configuration would then be legal, since the wheels not satisfying R06 would not be in use.

Such an omniwheel would have nearly triple the traction of a single Rover Wheel.

[Greg Marra]

Originally Posted by corpralchee

What if your robot had two drive trains? One in the forward direction and one in perpendicular to the forward direction. You lifted one drive train to use the other. Kinda like the trucks that are made to drive on the road and railroad tracks.

This is something that Buzz (FRC175) has done to great success in the past. Look up some old video - it's pretty spectacular.

Not an expert on this but I think you should be limited to using 4 wheels. If not
then you could use 8 - 16 whatever - a wheels arms race.

If everyone has to work with four wheels the mental arms race has to be where the competition goes.

I think with the mass of the trailer behind you - best movement strategy is based more on sailing/sledding/bumper cars then driving on carpet.

[sdcantrell56]

Originally Posted by Dr.Bot

Not an expert on this but I think you should be limited to using 4 wheels. If not
then you could use 8 - 16 whatever - a wheels arms race.

Adding more wheels does not increase traction. The maximum force you can apply to the floor is determined by the coefficient of friction and the normal force. Surface area has no influence.

[kirtar]

Originally Posted by Dr.Bot

Not an expert on this but I think you should be limited to using 4 wheels. If not
then you could use 8 - 16 whatever - a wheels arms race.

If everyone has to work with four wheels the mental arms race has to be where the competition goes.

I think with the mass of the trailer behind you - best movement strategy is based more on sailing/sledding/bumper cars then driving on carpet.

Adding more wheels would probably make little difference in driving, and would probably actually make it harder to turn (if you use skid turning, and with that many wheels, you probably will). Also, in theory adding wheels won't really help since as long as you're using the same wheels (you will be), you're just spreading out your normal force while still having the same coefficient of friction (.06).

[nexgendedhed]

I am not a physics expert either, but do have one thing that might be useful.
People are using the terms traction and friction almost interchangeably, which may lead to misconceptions. Friction (F=uN) is a fairly simplistic empirical model that does not depend on surface area. Traction, on the other hand, actually does depend on surface area. Using a larger surface area while leaving other factors constants results in increased traction. For evidence, think of rubbing two small pieces of sandpaper together versus two larger pieces, or wide drag racing tires.

I can't find a whole lot of information on traction, however, so if anyone knows more and would like to correct me, I would appreciate it.

[sxysweed]

I stopped reading the thread at page, two it's nearing bed time for me. But I found the solution for those having a hard time TURNING IN PLACE with Skid Steer. Turning in place in difficult enough, but remember the TRAILOR. Not only do you have to pull the wheels sideways, but you have to pull the skid sideways. Trick for the drivers would be to drive forward and then turn. Initiate a drift and then use that to slide. The turns would be wider, but more controlled. It would take practice though.

Example of what I mean:
http://www.youtube.com/watch?v=P5aWAW2hea4

But another proble I see happening is a few teams that have no practice or experience driving with no traction will go straight forward and before even attempting to stop, they will try to stop and either lock of the wheels or put them in reverse. You will stop like this at some point, but I find it likely that the robot will veer off to one side. These are things I've experienced in trying to drift RWD RC cars with PVC Tires. It's different with Skid Steer, but the lack of traction idea is similar.

Originally Posted by sdcantrell56

Adding more wheels does not increase traction. The maximum force you can apply to the floor is determined by the coefficient of friction and the normal force. Surface area has no influence.

Are you sure?
I'm more involved in 1:1 cars and racing, and the general idea is that wider tire = more traction. Same reasoning behind the Bugatti Veyron's 16" wide rear tires.

But to me it would seem that having two/three wheels directly next to each other would make turning more difficult, as the mu is greater sideways than forward. And this is from my observed experience in the FLL....

Another thing I noticed today is that the Rover Wheels aren't true. What I mean by this is that they're completely uneven all the way around. Try rolling one forward, it will fall over to one side real quick. I'm sure mounting them normally and giving them a good once over on a good surface (concrete?) will level it out nice, and prove more surface area. But acording to the guy in quotes, this would be useless?

-----------

Me and my AP Physics teacher had brief discussion on using fans or duct fans (I would prefer the later for a few other reasons) to aid in propulsion. You could possibly add another 10N for acceleration, but you also forget you can possibly use this to steer the robot. Mount a few small duct fans here and there that generate say 3N each, and you can help correct a drift or even slow down in a straight line....

[=Martin=Taylor=]

We got a 4 wheeler running on the game floor today with the wheels.

Seemed to be controlable enough. We could turn it when it weighed 30 lbs. and when it weighed 120~160 lbs. it turned even better.

We'll have to see how it goes with the trailer.

[JagWire]

Originally Posted by Hachiban VIII

We got a 4 wheeler running on the game floor today with the wheels.

Seemed to be controlable enough. We could turn it when it weighed 30 lbs. and when it weighed 120~160 lbs. it turned even better.

We'll have to see how it goes with the trailer.

that's cool to hear. how is it set up? tank-drive?

[RoboGeek99]

Ok weve spent all of our meeting today discussing the "best" type of drivetrain...we narrowed it down to a tank style and a car steering with back-wheel drive...any thoughts?

Ive read the thread and i really cant see much discussion on the drive trains but rather on increassing friction...my advice embrace the challenge instead of trying to move around it

PS-Wat is the aprox weight of the trailer rules dont specify?

[samir13k]

I replaced the wheels on a 30-40ish lb kitbot today that was previously made with the new kitbot wheels, and tried it out on the "regolith" surface, and so far....its not looking so well. The bot can be kicked around and will slide sideways really easily. Of course, there are many different factors going into play, especially the low mass.