[archiver]

Posted by Ted Jones at 1/19/2001 11:50 AM EST


Engineer on team #486, Positronic Panthers, from Strath Haven High School and Drexel University / Boeing Company.


In Reply to: Repost YOUR DRILL GEAR RATIO ....... HERE.......
Posted by Anton Abaya on 1/18/2001 8:37 PM EST:



I smell a white paper on this...

We are a second-year team, and last year we learned the hard way about the need to gear down the drill motors. It was mainly due to a lack of time and experience that we had direct drive. Very fast bot, but very hard to control.

Our approach this year has been to start out with a desired maximum speed. We've settled on about 4.5 ft/sec, or 3 mph, a brisk walk. A little more than 10 sec to run the length of the field, to put it in perspective.

We're looking at about an 8:1 gear ratio, using the high speed setting on the drill motors, and 8 (really 9 inch) dia wheel chair wheels.

What you need to calculate is the tangential speed of the wheel at you desired maximum speed. Find the RPM then of the wheels' driveshaft, this is a function of wheel diameter. Then consider the maximum RPM of you motor. Your required gear ratio between the motor shaft and the wheel then is the motors maximum RPM divided by the desired wheel maximum RPM. So, lets say you've got the drill motor gearbox set to high, so 1000 RPM is the max speed. The desired maximum RPM of your drive wheel is 250 RPM. 1000/250 is 4:1, so your gears , chain sprockets, or pulleys would need to be 4:1. You can comapre the number of teeth, or diameter, either one will work.

There's a lot of basic calculations to be done here, and dimensional analysis will save your hide! DA refers to keeping units in your equations. If the units work out in the end, your answer is most likely correct.

A big concern now is with a torquey drive system, you can over load the 60 A circuit breaker pretty easily. We're planning on 20 or 25 A auto resetting CBs on each drill motor, so we don't hit the big one and get stuck out there during the match.

Hope this helps,
Ted


: I'm really just curious as to what teams normally use.
: Do you have the drills on :

: 1. high or low gear?
: 2. what gear ratio?
: 3. do you use the clutch?
: 4. how fast did you go from end to end of the playing field?
: 5. how fast do you go in mph?
: 6. can you still push/pull heavy bots?
: 7. was your circuit breaker stable?
: 8. did you strip your motors?
: 9. whats your favorite drill brand? (for fun...)

: thanks guys... i hope people post cuz i know it'll come in handy for the many teams deciding their drive train as we speak...

: -anton
: "the ninny with a power tool"