More Wheels?

[LoveMe_HateMe]

Can you add a 5th moon wheel that would lower down and still be counted as one of the wheels to the bot and used as a break affect?

[Akash Rastogi]

You can add as many wheels as you want as long as you follow the rules regarding how wheels are placed.

Rule <R06>

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).

Enjoy.

[Cow Bell Solo]

And as long as it is the rover wheels, only the rover wheels can touch the floor surface this year.

[SWIM]

Although, if you expect physics to apply to your robot, you might as well lock up the wheels that already touch the ground, because dragging more locked wheels across the ground isn't going to do anything for you.

[lynca]

Originally Posted by LoveMe_HateMe

Can you add a 5th moon wheel that would lower down and still be counted as one of the wheels to the bot and used as a break affect?

In 2002, 624 made a robot with a 5th high traction wheel in the middle of the robot for pushing/shoving during the game. I don't have a picture of the robot but it was a beast. If anyone has a picture I would love to see that robot again!

I'm not sure that the 5th wheel will help you since you would be dividing your normal force by 5 wheels instead of 4 wheels.

A 5th wheel helps with traction when you have carpet but not with FRP !

[Tom I]

Originally Posted by lynca

I'm not sure that the 5th wheel will help you since you would be dividing your normal force by 5 wheels instead of 4 wheels.

Actually Im not sure if thats true... Yes you would be dividing the normal force by 5 and thus the force of friction remains the same, but friction is not the only thing that needs to be considered. Traction would increase due to more surface area, and thus it would stop quicker.

Yes a 5th wheel is legal, and yes it would probably help a little. I would recomend if this would only be for breaking, mount it perpendicular to the other wheels rather than parallel. The coefficient of friction is higher for the wheels sliding laterally than in line with the rotation, so you would get more friction and stop even quicker.

[Chris Fultz]

You don't really get any more traction with 5 vs. 4 wheels.

Surface area is not part of the equation.

From our friends at Wiki -

Maximizing multi-wheeled vehicle traction
It is important, due to broad application, to point out the specific case of multi-wheeled vehicles or vehicles with multiple contact patches between the tire and the road surface. Multiple wheels do not increase a vehicle's traction, because the friction force is independent of the contact area.[1] The friction force (Ff) is dependent upon the coefficinent of friction (COF) between the contact surfaces and the normal force (N = a force perpendicular to the contact surface).

Ff= N(COF)

A greater number of wheels will allow a vehicle to carry a larger load, thus increasing the resulting normal force. More traction is achived with a greater load because the potential frictional force has been increased.

The case of wheels sharing a given normal force is particularly important in vehicle design. Two identical tires sharing a common load achieve maximum stability when they share the load equally. Likewise, an unequally loaded pair of tires sharing a common load will not be able to achieve the same maximum stability.

[Jon Stratis]

Originally Posted by Chris Fultz

You don't really get any more traction with 5 vs. 4 wheels.

Surface area is not part of the equation.

From our friends at Wiki -

To emphasize this, it's important to note the differences between this year and previous years. In the past, the wheels were slightly squishy, as was the carpet. As you powered your wheels, the carpet and wheels were able to conform a little, and provide a larger surface area and more grip do to the deformation in the parts. More wheels, therefore, would provide an increase in traction.

This year, the Regolith material is firm and slightly bumpy, while the wheels are firm as well. What this means is that each wheel is going to approximate a point contact with the surface, with no deformation of parts. the conditions the GDC has provided us as closely match the ideal friction equation posted above - where number of wheels does not change the robots traction (assuming all wheels are driven).

[gamercards]

What about have six wheels but only have four driving wheels? Will that have better traction?

[Jeffy]

People will debate, and you won't get a straight answer most of the time. But, here is my take, more wheels doesn't matter (trust wikipedia).
This only applies if all the wheels are powered.

So, if you have two unpowered wheels, the weight on those wheels won't be providing extra traction to your drive train. So, as far as i know, power all the wheels that touch the floor.

my 2 cents

[Ozeaden]

you wouldnt be able to have that wheel be a break because you would have to change something in the wheel so that you make it a break. it is against the rules to alter the wheels in any way.

[DonRotolo]

The Q & A system has clarified the use of a sensor to detect motion, and it doesn't have to be a KoP wheel. See This.

I plan on dragging a (computer) mouse.

[Cow Bell Solo]

Originally Posted by Ozeaden

you wouldnt be able to have that wheel be a break because you would have to change something in the wheel so that you make it a break. it is against the rules to alter the wheels in any way.

No, you could just have it be rigid, or you could have the wheel turn in the oppisite direction. I don't see why you would need to alter the originality of the wheel.

[funstuff]

Originally Posted by lynca

In 2002, 624 made a robot with a 5th high traction wheel in the middle of the robot for pushing/shoving during the game. I don't have a picture of the robot but it was a beast. If anyone has a picture I would love to see that robot again!

I'm not sure that the 5th wheel will help you since you would be dividing your normal force by 5 wheels instead of 4 wheels.

A 5th wheel helps with traction when you have carpet but not with FRP !

http://cryptoniterobotics.org/images/2002.jpg

^ the 2002 robot, minus side panels and bumpers. And it was the most beastly robot FRC has seen. It pulled a small car (or so I've heard). Last that I have heard, it is still in (somewhat) working order.

For Andy's reminiscing pleasure: http://cryptoniterobotics.org/team/robots/

-Kat

[bigbeezy]

i meant to get a closer look at SPAM's robot (180) at Florida but I believe they have, in addition to their normal drive and a fan, a set of wheels possitioned perpendicular to the others and they would pneumatically lower the wheels. these were mainly for a semi-swerve affect, but i suppose could be used as a break. I'm sorry i dont have a better explaination i only saw it from the stands.