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Author Topic: 3 wheel vs. 4 wheel, 2 motors vs. 3 motors,  (Read 3150 times)

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Offline gkiverm123Topic starter

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3 wheel vs. 4 wheel, 2 motors vs. 3 motors,
« on: November 17, 2014, 04:58:38 PM »
Hello all,

1) I'm just getting started with robotics and am building a sumo bot. I plan to use a differential steering system. Now I'm unsure whether to use an arrangement with 3 wheel or 4 wheels. I found this link http://www.robotshop.com/blog/en/what-wheels-should-my-robot-use-3654 very helpful, but it doesn't really explain which one would be better for speed or torque, etc. 

2) The other thing I was thinking was, if I do go with 3 wheels, would it make sense to have the third upper wheel (that doesn't have a pair) also motorized? So, basically, each wheel would be connected to a motor. The two backs ones would be used for steering and forward/backward movement. The upper wheel would only help in moving forward/backward.

Thank you!

Offline Schlayer

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Re: 3 wheel vs. 4 wheel, 2 motors vs. 3 motors,
« Reply #1 on: December 02, 2014, 11:59:34 AM »
For a first robot, I would recommend you definitely use differential drive and not go for 4 wheels. A sumo bot will need its powered wheels to be centered under as much of the robot's mass as possible for maximum traction; you might actually only want two wheels! You also would't want to add a third motor in any case, as the benefit would be minimal compared with the added complexity in your code for moving the robot. I have worked on a sumo robot project which ended up using two motors, one wheel each, and the front was just a super-sharp wedge that got underneath enemy robots and scooped them up so they lost traction. (That was radio controlled though.) If you need anything else, let me know.

Offline jimujan

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Re: 3 wheel vs. 4 wheel, 2 motors vs. 3 motors,
« Reply #2 on: December 18, 2014, 06:53:14 AM »
Hi . I think this article will be useful for you  - instructables.com/id/How-to-Make-a-Sumo-Bot-Science-Olympiad-2011-Rule .

Offline Schlayer

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Re: 3 wheel vs. 4 wheel, 2 motors vs. 3 motors,
« Reply #3 on: December 19, 2014, 06:48:24 AM »
Hi . I think this article will be useful for you  - instructables.com/id/How-to-Make-a-Sumo-Bot-Science-Olympiad-2011-Rule .
Interestingly enough, the sumo robot I helped to build was for this same exact competition! Ours did considerably better than the one that article was written about (1st place at the PA state competition), but it does seem to provide some helpful tips on getting started with an RC sumobot and proves a very through overview of the hardware required sans micro controller to build a truly autonomous robot.

Offline CJAlbertson

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Re: 3 wheel vs. 4 wheel, 2 motors vs. 3 motors,
« Reply #4 on: December 29, 2014, 06:48:28 PM »

A review of the basic physics will tell you that you do NOT want any weight at all on an un-powered wheel.  Other things being equal, the total horizontal force the robot can apply depends on the weight on the powered wheels.
Chris A. in So. Cal.

 


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