How can we drive on this new floor?

[Lesman]

I think one thing that will be incredibly important is weight distribution, if you have more weight on one side your robot it going to be spinning in circles since that side will have more traction.

[Cyberphil]

Originally Posted by JagWire

I think they were referring to what is called "tank drive" which you can think of like driving a bulldozer, only without the tracks, just the wheels. The wheels on one side would operate together independently from the other side.

No. Sorry, but someone was talking about putting treads on their bot. Just clarifying that.

[Akash Rastogi]

Originally Posted by Cyberphil

No. Sorry, but someone was talking about putting treads on their bot. Just clarifying that.

Yeah I saw that somewhere...

People need to learn to use proper terms though please. There's listings on here about all different common terms used in FIRST and on CD, just search them people.

[JagWire]

Originally Posted by Cyberphil

No. Sorry, but someone was talking about putting treads on their bot. Just clarifying that.

ahh, I apologize, in my haste reading through the threads I must have mis-read something

In that, I would most definitely agree with you

Has anyone thought about creating a way to modify your center of gravity/weight distribution on the wheels, in order to aid in traction control? Would require a mass on board able to be moved in some direction or another. Might not be likely to have a light enough bot in most cases for it to be feasible. I wonder to what extent something like that would be able to help though? Hmm... possibilities...

[nathanww]

Our team was considering this, but then decided to go with automative-type traction control just on the basis of it being a proven technology

[Creator Mat]

a problem i have in general with all drive trains that allow u to turn suddenly like crab drive, swerve drive, and holonomic especally. with the all ready low traction of the feild a quick turn would send your robot flying down the feild out of control. then if you solved the traction problem your trailer would jack knife and take you out. also for the holonomic drive this drive in a high friction envrioment had no pushing power. so this year the holonomic drives biggest strength, its mobility, is gone. also the drive itself is made to have no pushing power and in my opion this year the robot with the most pushing power is king not the one with the most traction.

[pacoliketaco]

So today i went with my mom to buy a sheet of the flooring material. As has been stated before, it was $30 for a 4'x8'x.125" sheet, of a material that seemed extremely close to the look and feel of what people have already described. As soon as we got home, i took one of the new wheels and slid it on the flooring. At first, when we first opened the kit, i took a wheel and slid it on a table nearby, remarking at how there was no traction with the table surface. Well, compared to the actual flooring, that table would be much better. There is soooo little friction between the wheels and the flooring. i am actually quite scared by how little traction we are going to be working with. earlier someone was talking about these wheels being similar to those of previous years, in that they might deform a little to adjust to the uneven surface of the floor. That is not going to happen, as these wheels are very hard plastic, which will not be changing it's shape ever.

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?