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#3
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Re: Maximum Pushing Force
Quote:
Pushing force is limited by the amount of traction the robot gets with the carpet. This is based on friction ( Friction = mu * Normal). There are 2 ways to increase your traction: 1. Increase your coeff. of friction with the carpet. 2. Increase your normal force (by adding weight to the robot). In 2002: Team 60 Chose option 2. They lifted up the 2 goals, and greatly increased their pushing force. Team 71 chose option 1. They used file cards as their tractive material. Since file cards "dig in" to the carpet, they essentially have a coefficient of friction which approaches "infinite". Now... since 71 was geared low enough (The Beatty Shuffle...), their infinite coeff of friction allowed them to outpush almost anyone, without increasing their normal force! So yes... if you have a 130lb robot, with a 1.5 coeff. of friction, you don't need to gear the robot down anymore than that. (Unless you think you will "interlock" with the carpet, or wire-mesh, or whatever FIRST gives us this year). There are also many other considerations when you're "gearing down" (as Ken mentioned above). It is important that your robot can "slip" your wheels when it is pushing against an immovable object (a wall). Stalling your wheels, and motors is NOT good for the system, and can lead to damage, or popping of circuit breakers. How much current do you want the motors to draw while you are at "max load"? How fast do you want the robot to be able to move while still being able to push a set amount? Does the motor you're using for drive have enough power to accomplish both? Should you think about using a "combiner" to add on another motor? Do you need a shifter so you can accomplish both? The answers to all these questions can be found through simple calculations! *gasp*. If you need help with any of them, I recommend this thread: http://www.chiefdelphi.com/forums/sh...ad.php?t=22604 There are plenty of other good threads like it. Simply search the forums. Anything "Paul Copioli" says is drivetrain gold. Good Luck, and don't be afraid to ask for more help. There are plenty of mentors on here more than willing to answer questions for you. You may also email or AIM me for more help. Hope this helps, John [edit] This presentation might be helpful to you. http://www.teamfordfirst.org/_documents/Motor%20%20Drive%20Presentation%20(12-7-02).ppt [/edit] Last edited by JVN : 30-12-2003 at 14:47. |
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