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tmei1201mb
02-08-2011, 04:59 PM
i was thinking today and is there a way to change the RPM on the minibot.

DonRotolo
02-08-2011, 11:28 PM
Sure. Use Gears maybe?

tmei1201mb
02-09-2011, 04:35 PM
yes we are using gear we are using small on the motor and big on the wheel but is there a dirfence(sorry of spelling) in the gear ratio

Jared Russell
02-09-2011, 04:48 PM
Yep - you can use gears or chain to change the RPM of the minibot motors.

(Anyone else appreciate the irony?)

Mark McLeod
02-09-2011, 04:53 PM
It shouldn't be vexing...

Bob Steele
02-09-2011, 06:19 PM
You can change the RPM of the motor in a variety of ways. If you are using a controller (NXT) you can vary th speed of the motor that way.

If you are speaking of changing the angular speed of the motor (RPM sort of..) you really can't if you are just wiring it up with switches to connect directly to the battery within the rules of this game.

You can, however, through a gear box or a chain and sprocket or a rubber band and pulley or something else... change the resultant angular speed of the wheel or wheels.

If you want to predict the speed change look at the ratio of the number of teeth of the sprocket or gear or the size of the pulley and compare that to the gear/sprocket/pulley that is connected to the wheel.

If you have a 1" pulley on the motor and a 3" pulley on the wheel ... the wheel will run at 1/3 the speed of the motor. (It would be the same for a 12 tooth gear and a 36 tooth gear)

If you want a particular angular speed you will need to know the original angular speed of the motor and build a gearbox that attains the angular speed of the wheel you want to turn.

If you want to know how this translates to speed up the pole (linear speed) it is abit more complex but in a short simple way, you could multiply the angular speed (in RPM if you wish) by the circumference of the wheel and you will get linear speed.

For example.. you have a final angular "speed" of 2 Pi radians/second ... or 60 RPM... you would multiply that by the circumference of the wheel (say 6" for instance) to get a linear speed of 30 feet per minute.. or .5 feet per second.

If you want to climb the pole in 10 seconds and the pole is 10 feet of climb that would take you 20 seconds... (so obviously you would want a higher angular speed)

Of course, it isn't really quite this simple... because you have other forces involved (gravity, friction, electrical resistance..etc...) but you get the general idea.

Happy engineering!!