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We need wheel radius to give You torque estimate
How big is the maze? It sounds to me as if you could solve this with way less than 6 kg even for a pretty big maze (say, two-foot distance between walls.)I think any of the Pololu 25D or 37D gear motors would work fine. Typically with mid-to-lower gear ratios to get some speed -- between 1:20 and 1:50.Also, you'll want to look into getting motors (or wheels) with encoders, to make sure you can tell when you're driving straight!If you have one motor per side driving, you don't need a chain to drive both wheels. That just adds complexity. Unless the maze has hazards like oil slicks or ice patches or whatever...
if not chain, how do u suggest i drive both wheels with a single motor..?
Quoteif not chain, how do u suggest i drive both wheels with a single motor..?You said you'd use two motors. I suggest driving the left rear wheel with one motor, and the right rear wheel with the other motor, and leaving the front wheels un-driven. If you can add servo-based steering, you'll be better at turning, but you can probably do without it.Or just put in four motors. Motors are cheaper than transmissions and linkages these days... Look at, for example, the Wild Thumper series for design ideas.
its around 3.5 - 4 cm...
Right, there are two options:1) Use four wheels like a model car. Either steer the wheels in front, or drive each wheel individually and do "tank steering." The Wild Thumper does the latter -- check it out here: http://www.pololu.com/catalog/product/1565That, in turn, uses these kinds of motors: http://www.pololu.com/catalog/product/22742) Use two big wheels, and two smaller wheels that are just "limp" and ideally pivot. Casters, balls, cart wheels, whatever you want to call them. Turning the big wheels different directions will pivot the robot in place. With only two motors, this is the easiest to implement.3) You probably want motors with built-in encoders, so you can tell whether one wheel is going faster than the other and compensate, to go straight.4) You don't need the full weight * radius amount of torque, as long as you don't want to accelerate wildly (and can make soft start/stop part of your control.) Wheels turn very easily, at least if they are narrow and hard.If you haven't gotten any motors yet, those motors are a fine recommendation for 6V-8V systems. If you are doing a 12V-16V system, try these instead: http://www.pololu.com/catalog/product/1444You will need some motor controllers to drive them, too. And a microcontroller to tell the motor controllers what to do. Feel free to ask again if you don't know where to go from here!
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Mechanics and Construction