pic: Traction test

[rees2001]

Originally Posted by Nuttyman54

...a single CIM could only input half the torque of two CIMs. Therefore, the single wheel accelerates better because it essentially has built in traction control, as it takes a lot more to put enough torque through the single wheel to slip it.

This sounds about right to me. Equate it to getting your car moving on a slick surface (ice). If you start in 1st gear you will most likely spin your wheels because the engine doesn't have to overcome much resistance to turn the wheels. Start in second gear and now your engine has to overcome the gearing before your wheels will spin. (This works great on a standard but not so easy to do with an automatic unless you have second gear start, my old '96 Grand Prix had it & it got me out of a few tricky spots.)

[XXShadowXX]

Originally Posted by Rosiebotboss

The robot on the right won every time. Why?

Static vs dynamic friction
Static inline 0.06
Dynamic inline 0.05

4 motors allows the wheel to reach top speed faster, then the two. The Cof, increases until it peaks at static, then approaches 0( or some value, that is less then static friction), as the wheel speed increases. Since the 4 motors reach top speed faster the can't exert their larger force, the 2 two can since they accelerate slower due to the lower torque.

Also, the force of fiction is Cof*P (pressure* Fiction) by having two wheels per side driven you decrease the pressure P (P=F/A, force/area), the force is the weight of robot, a large area will decrease your ability to move, by increasing the force of fiction. This also hurts the 4 motor design.

Thats two answers to your questions, heres the solution:
TCS, Traction Control System.

[Japper]

Are you using this year's acetal tread Rover wheels or some other variation?

It would be interesting to see the test results with this year's acetal tread Rover wheels on the FRP...

[Rosiebotboss]

Update:

We rebuilt the tandem wheeled robot to include a 1:3 gear ratio. So now both robots run at 300 rpm wheel speed. I didn't have my camera with me last night so I do not have any photos or video, but the single wheeled robot won the shoving match every time.

Conclusion: 4 wheel drive is the way we are going, maximizing stability and power to the ground.

[SuperBK]

Thanks for the update. We have a running discussing going here about whether having two wheels at each corner for a total of eight wheels is better than just a single wheel at each corner (total of 4). I say it doesn't help and that having a wheel at the center would do more good because it would take some of the weigth off of the corner wheels, which would help turn.

[Rosiebotboss]

Originally Posted by SuperBK

Thanks for the update. We have a running discussing going here about whether having two wheels at each corner for a total of eight wheels is better than just a single wheel at each corner (total of 4). I say it doesn't help and that having a wheel at the center would do more good because it would take some of the weigth off of the corner wheels, which would help turn.

There is a video posted on Youtube by the Nutrons, (Team 125 at Northeastern Univ) of them driving around their 2007 frame outfitted with the Rover wheels on a piece of FRP. Don't worry about unloading the corner wheels to facilitate turning!

[Japper]

I couldn't help to notice that none of the videos on Youtube that have rover wheels appeared not to be weighted down to simulate the typical 150 pound robot .. the actual weight factor may affect how these rover wheels perform on that surface...

Also, I wonder if the conditions of that field service will get better as one and one half days of robots drivinig on them during the competition...

Hopefully we will have our practice field ready for testing tonight...