electric vehicle for science olympiad

science_geek

i am building an electric vehicle for a science olympiad meet, the only thing it has to do is travel between 5 and 10 meters in an estimated time that cannot exceed 45 seconds, which is a problem for me, i planned on using parallax's continuous rotation servos, they work great for anything less then about 8 meters, the meet i had last year i used them and i ended up exceeding 45 seconds over a 9.5 meter distance, i was wondering if there was anyway to crank up the speed on the servos to about 1.5 - 2 times faster than usual speed, if its not possible is there another brand of servo i could modify for continuous rotation that i could get for cheapish

Duffer

Larger diameter wheels.

Duffer

Philldapill

Duffer is right. Larger diameter wheels, gearing the servos up, or anything that increases the tangential velocity of the wheel itself.

FlyingFishFinger

Make the wheels as big as possible such that at that size of wheel, you have just enough torque to move your platform. If that's not enough, I think you might need faster motors.
Also, I've found from robotics competitions that you can increase the pulse width on servos a little over the spec value, resulting in faster rotations.

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You've got to play the game.
You can't win.
You can't break even, except on a very cold day.
It doesn't get that cold.
~Laws of Thermodynamics~

science_geek

thanks, i figured the bigger wheels, but i never thought of making a second "external" gearbox, ill have to try that,

PS: i flew my rc helicopter for the first time today and i didnt crash, can you say nerve racking

SRLM

You can make the servo turn faster by using a higher voltage, but at the cost of a shorter life (for the servo).

Lawson

On many newer servos the driver for the motor is a separate chip. In this case it's possible to "liberate" the power pin of the motor drive chip and connect it to an independent external power supply of higher voltage. I've seen this done a couple of times on BattleBot forums. (aka long lifetime wasn't a design requirement :P )

Marty

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Lunch cures all problems! have you had lunch?

Cole Logan

I know you said that you want to stay with the servos but one thing that I have found that works really good is electric drill motors. There fast and torque. and the useally have a chuck buit on them so its easy to add your wheel to it.

Beau Schwabe

science_geek,

Check out my reply to this thread....
http://forums.parallax.com/showthread.php?p=525689

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.