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#1
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Are six wheels better than four?
well... the title was mainly b/c i could not think of anything better... but i wanted to know if people had done experiments to prove weather or not having more wheels creates more traction. form what our team has found, it seems to come out in a wash, but i wanted to see what other people thought. any help would be appreciated
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#2
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Re: Are six wheels better than four?
In theory, more wheels will not give you more traction.
More wheels will give you the ability to redistribute your weight to change the the robot's handling on the surface. So sometimes more wheels will give you better handling and other times more wheels will give you a handicap. |
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#3
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Re: Are six wheels better than four?
The interaction of the wheels on the floor is $@#$@#$@#$@# close to two ideal surfaces.
Therefore, surface area in no way will increase traction. the coefficient of friction is said to be .05/.06 for static, therefore all robots that are 150 lbs can only push with 7.5/9 lbs of force, regardless of the number of wheels. |
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#4
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Re: Are six wheels better than four?
Quote:
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#5
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Re: Are six wheels better than four?
Quote:
Now, the wheels slipping provide less traction then not slipping, you won't increase the maximum traction by solving that issue, but you'll reduce the time you have minimized traction. This would probably solve the same issue, as if you are trying to push another robot and have traction control to keep your wheels from slipping, and they don't, you can push ~20% harder. |
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#6
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Re: Are six wheels better than four?
Six wheels are better than four, if the middle wheel is some type of idler wheel used to provide feedback in the programming portion, to attempt to create some sort of traction control system.
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#7
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Re: Are six wheels better than four?
Unpowered idlers of any type are a horrible waste of normal force.
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#8
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Re: Are six wheels better than four?
To me it seems that the most power you can create is when your on the verge of doing a burn out. Its a very very fine line.
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#9
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Re: Are six wheels better than four?
Keep in mind that most of the discussions concerning friction and traction assume a flat surface contact. The FRP material is going over carpet. If the FRP was placed on a hard surface like concrete or a gym floor the 2 D assumptions would be valid. Because of the carpet the FRP may be deformed changing the contact area. This puts the physics into a 3 D problem. Does this change things? Do fewer wheels cause more defection and better performance or does the deflection make it worse? Is the deflection enough to have a significant effect? I don't know the answers. Not sure about the math either, but it needs to be looked at. This is a case where one needs to consider the assumptions of a math model to determine if the model is valid for the problem.
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#10
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Re: Are six wheels better than four?
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True that. Anything that touches the ground spreads should be powered... IMO |
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#11
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Re: Are six wheels better than four?
We are actually going to use one idler wheel. As long as the benefits outweigh the inefficiency created, why not?
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#12
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Re: Are six wheels better than four?
We've had a lot of debate about this on my team, and this seems like an appropriate thread to ask for clarification:
What sort of difference, exactly, is there between adding extra driven wheels versus adding extra undriven to our robot, and why? I've seen snatches of conversation on the issue, but nothing really substantial enough for me to draw a conclusion from. |
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#13
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Re: Are six wheels better than four?
Quote:
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#14
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Re: Are six wheels better than four?
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EDIT: For those wondering, "mu" is the coefficient of friction (I imply it's static in this case), which is basically a measure of how difficult it is to move two materials against each other, with larger numbers (usually around 1) being more difficult than smaller ones. As you can imagine, the mu's in this game a very low, between .15 and .05, depending on who you ask. Also, the reason spinning wheels generates a frictional force in the first place basically goes back to Newton's third law, the old action-reaction one. Quote:
Last edited by Siri : 06-01-2009 at 21:49. Reason: newbie question: is it better to double post or edit to add? |
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#15
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Re: Are six wheels better than four?
Extra undriven wheels take weight off of your driven wheels. In short, you get less traction to your motors. Also, it will create some drag. More driven wheels would be great if you ever get up to the point that you are using the full power of the usual two powered wheels. However, you probably will never get to that point on such a surface. To be honest, I don't see much of an advantage of an unpowered wheel. They are going to slow you down. Even with the data they could collect, it would still slow you down too much. As far as extra powered wheels, it is just a waste of your weight because you will never need that much power on this game given the surface and the size of the field.
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