How can we drive on this new floor?

[thefro526]

Originally Posted by Zyck_titan

It seems to me that heavier Bots will do a lot better, and I'm sure everyone will be maxed out on weight, so the question is how do you add weight....without adding weight.... *Hint hint Nudge nudge*

That's an easy assumption to make.

But what about momentum? Changing directions with a heavier bot it's going be be a bit harder I think... Or maybe not, I'd like to get some input on this.

[Enigma's puzzle]

Sorry to break it too you all but tank drive is going to be a pain, Tank drive has an axis of rotation around the center of the robot. BUT you have a trailer, you are going to be dragging the trailer wheels side ways it will be a battle.

Also the trailer anytime that you backup you will jack knife almost immediately, then you will be unable to control your backwards motion, turning with the trailer.

[germanystudent]

Haha! i bet everyone in the north U.S. has a bit of an advantage with this above average snowfall. similar to snow and ice, you would want to start slow, and don't lock up your wheels... try pulsing them like in an anti lock break system, or just slowing down. weight to increase traction is also double sided, sure you can accelerate faster, but then again you take further to stop weather that be sliding or slowing down. It pays to drive in Idaho!

[mray1031]

Anyone thinking about workarounds to the traction problem?

If the total traction is a function of your friction, surface area, and weight, and friction is fixed- shouldn't we be looking at surface area and weight?

Surface area is easy- more wheels (I don't think there's a limit)

But weight? could be interesting. Any ideas?

[thefro526]

Originally Posted by Enigma's puzzle

Sorry to break it too you all but tank drive is going to be a pain, Tank drive has an axis of rotation around the center of the robot. BUT you have a trailer, you are going to be dragging the trailer wheels side ways it will be a battle.

Also the trailer anytime that you backup you will jack knife almost immediately, then you will be unable to control your backwards motion, turning with the trailer.

In theory though, you should be able to drag the trailer around because the wheels are the same non-grippy wheels that are on the robot. I'd also venture to guess that a trailer weighs substantially less than a robot, but then again I'm not entirely sure...

[mray1031]

oh man. people are posting fast i guess my last one was outdated...

since people are already thinking about pluses and minuses of weight anyone consider varying the "weight" of your robot?

[Enigma's puzzle]

To add wieght with without adding wieght you could always fill up your trailer

[dmlawrence]

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

[mray1031]

Yeah by adding to the trailer you gain mass - just not on your drive wheels. You'll gain momentum, just not traction. Plus you're giving the other team points.

[Enigma's puzzle]

Traction is detirmined by pounds per square inch, so more wheels is taking away from your traction on each one, so every non-drive wheel is a waste of potential traction theoretically.

All wheels have the same coefficient of friction so because of the wieght differential the trailer will move, but slowly

[Dracco1993]

I am a driver from the FRC team 1741. I like the idea of drifting to gain more control of the robots. My only concern is that with the trailer it will be very hard to turn quickly. Can you get enough speed to drift in the arena?

[Branden Ghena]

Originally Posted by dmlawrence

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

While a great idea...

Originally Posted by FRC 2009 Game Manual
<R06>
ROBOTs must use ROVER WHEELS (as supplied in the 2009 Kit Of Parts and/or their equivalent as provided by the supplying vendor) to provide traction between the ROBOT and the ARENA. Any number of ROVER WHEELS may be used. 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). No other forms of traction devices (wheels, tracks, legs, or other devices intended to provide traction) are permitted. The surface tread of the ROVER WHEELS may not be modified except through normal wear-and-tear. Specifically, the addition of cleats, studs, carved treads, alterations to the wheel profile, high-traction surface treatments, adhesive coatings, abrasive materials, and/or other attachments are prohibited. The intent of this rule is that the ROVER WHEELS be used in as close to their “out of the box” condition as possible, to provide the intended low-friction dynamic performance during the game

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

[darkpheonix]

In response to adding weight without adding weight, you could add fans to the bottom of the robot to draw in air from the bottom, just like those cars that can climb walls. Don't know how much it would increase the normal force though.

[Lesman]

There seems to be a lot of confusion going on about some physics, I think this should help:
ForceFriction = Mass*Gravity*CoefficientOfFriction
surface area is not a part of the calculation, as increased surface area means the normal force (force of the ground pushing up) is more spread out.
Force = Mass*Acceleration
thus
Mass*Gravity*CoefficientOfFriction = Mass*Acceleration
mass cancels
Gravity*CoefficientOfFriction = Acceleration
which shows that maximum acceleration is a function of nothing more than Gravity and the Coefficient of Friction, neither of which can be changed. Any team that powers all wheels in contact with the ground will have a top acceleration of .588 assuming no slippage (.06 cof) or .49 with slipping (.05 cof). The top speed assuming you drive straight across the regolith is approximately 2.2 meters per second, or about 5 miles per hour. The trip would take about 4.5 seconds.
By the way, where is everybody getting the coefficients of friction? How accurate are they? Doe anybody know the cof of the wheels on carpet?

[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.