Brakes

[Al Skierkiewicz]

As has been explained to me (thanks Raul! and I hope I am stating this right) adding wheels does nothing to increase the friction between the robot and the floor. As the surface of the floor and the wheels are both extremely hard and flat, they approach ideal surfaces. Theoretically, if the weight of the robot remains constant, the amount of friction applied between the robot and the floor would be the same with one wheel, four wheels or a flat plate as large as the robot.
As to using the Brake mode on the speed controllers, this works best when their is some amount of friction between the floor and wheels. The braking action is then a function of the rotational speed of a motor. The greater the speed, the more current flows into the controller and a greater back EMF is produced at the motor. At low speeds there is very little current and hence very little back EMF. I am prediciting that in this game, supreme control over wheel rotation, moving and braking, will prove to be the single greatest factor to stable driving.

[Andrew Y.]

I agree that surface area has nothing to do with friction. Now, yes the lateral friction is higher...by almost a tenth if im not mistaken.

Personal opinion...not worth the time or space. again PERSONAL opinion .........great now some teams gonna do it and show me up at comp

[EricH]

Originally Posted by Al Skierkiewicz

As has been explained to me (thanks Raul! and I hope I am stating this right) adding wheels does nothing to increase the friction between the robot and the floor. As the surface of the floor and the wheels are both extremely hard and flat, they approach ideal surfaces. Theoretically, if the weight of the robot remains constant, the amount of friction applied between the robot and the floor would be the same with one wheel, four wheels or a flat plate as large as the robot.

Would the above hold true if the coefficient of friction suddenly increased? i.e., locking the wheels so that they are 90* to the direction of motion, then lowering them and raising them as needed?

It wouldn't apply for wheels locking while traveling straight ahead, but maybe for that transverse friction...

[James Tonthat]

According to our tests, inline and transverse friction is either exactly the same or very slightly different (say less than 5%). Whatever it is, it definitely isn't double transverse than it is inline.

[Vikesrock]

Originally Posted by jtkellertx

According to our tests, inline and transverse friction is either exactly the same or very slightly different (say less than 5%). Whatever it is, it definitely isn't double transverse than it is inline.

Was this test loaded or unloaded?

[Al Skierkiewicz]

Eric,
The published coefficients were .1 for inline and .12 for transverse as I remember. So there is a little difference when the tires are 90 degrees to the direction of travel. So if a team were to design the assembly to drop for braking and was able to raise the inline assy so that the number of tires remained the same, the robot would have slightly better stopping. This comes at the sacrifice of steering though as the transverse wheels are not moving and contribute nothing to the steering stability.