Quote:
Originally posted by GregT
Surface area has very little to do with pushing power (it has NOTHING to do with friction), the only real way to get a holding advantage is to add more force on your wheels, lift the goals or somehting else. I was talking to a team at the canadian regional and I asked them what they would do to increase their pushing power, their answer was "we would use more motors" 
There are ways to max traction but if you really want an advantage you have to get more then 130 pounds pushing down.
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I'm writing this out, mostly, to try to get things straight in my head. Because, honestly, I don't entirely understand all of this.
Here's how surface area plays into things, in my mind. . . I could be off, or flat out wrong, or just somehow miscommunicating my ideas or whatever, but I'll try.
Friction, as everyone seems to know, is calculated by multiplying the coefficient of friction with the normal force of the floor on the robot. . . and, as such, by increasing the force (i.e., increasing your mass by lifting a goal) you increase the force of friction at the contact point with the floor.
Now, your drivetrain needs to overcome that additional friction to make the robot accelerate. Again, a natural delineation as a result of the increased friction.
The available torque of the motors is finite. By increasing the minimum amount of torque required to accelerate your robot, you're limiting your ability to accelerate at a greater rate, than, say, a similar robot without the additional friction.
Now, when it comes to wheel slip, the increased friction seems like it should be beneficial. You've made the force of friction greater, and thus it's harder to overcome . . .leading to a higher threshold (of sorts) before wheels slip. . .
Our design, though, doesn't rely on the added friction. Physically, in a tangible, lie-down-and-see-it sort of way, our belt material interacts with the loops of the carpeting. In this way, they are entangled (but not in a way that's damaging
So, this is how we harness the available torque in our drivetrain. Rather than make friction hard to overcome, we reduce slippage. While a wheel has a very small contact area, our belts are 194 in. sq. So, should one part slip, and lose it's grip on the carpet, the remaining part of that area has a good shot at reengaging that grip. Additionally, since we aren't overcoming extra friction, it stands to reason that we have a greater availability of torque (??) and can accelerate faster. . . That doesn't sound right, somehow, and probably isn't.
To me, it's just a slightly different method of achieving a similar end result. On a flat floor, I'd imagine, our design wouldn't be as effective.
But, that's how I see it, I think. Like I said, I don't quite understand it myself, and if someone with a degree (preferably in engineering or physics!!) wants to step in and make sense out of this for me, I'd love it. . .
In the end, though, I know what we did works. Whether our belting is excessive or not is debatable, though.