Thread: Ball Rollers
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Unread 23-06-2002, 23:26
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#0047 (ChiefDelphi)
  
Join Date: May 2001
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Re: Ball Rollers
Posted by Dave Lavery at 1/22/2001 3:01 PM EST


Engineer on team #116, Epsilon Delta, from Herndon High School and NASA Headquarters.


In Reply to: Ball Rollers
Posted by Justin Stiltner on 1/22/2001 1:33 PM EST:



: Would any team that has used ball rollers (counter-rotateing shafts that pull balls into a bucket, basket, ect.) in the past share how they got the rollers to spin in oppsite directions without using 2 motors?? we dont want to use gears if we can get away with it. Also what motors did you use? Any other advice is welcome.


Justin -

One of the most common, and straightforward, ways to do this is to put a pulley on each shaft, then run a belt between the pulleys - but the trick is to put the belt in a "figure-8" configuration, not just a simple loop. Then apply power to one of the shafts, and voila! The Delrin or fiberglass pulleys in the SPI catalog work great for this (part #U-PNG-xxx or U-IPD-xx), along with the green round Polycord belting (part #U-PRB-x).

Another idea that we used successfully last year was to just have one row of rollers to pick up the balls. As the rollers spun, they would push the balls against a smooth backplane. There was enough friction between the ball and the backplane (and the ball and the roller), that it would roll across the backplane as torque was induced by the roller. The ball would then be "passed" from one roller to the next, transporting it to the end of the line. The system worked very well (in fact, it was the only part of the robot that DIDN'T break during the entire season of regional and national competitions).

In both our attempts at doing this, we have used the Fisher-Price motors. But we modified the gear box so we were tapping the torque on the second output gear (with a new extended shaft, etc.) rather than the gear drive train output. This gave us enough speed on the rollers to really move the balls along (and since we were not compressing the balls very much, output torque on the rollers was not a big issue for us).

But last year we were only fooling with small balls, and didn't hvae to worry about the big ones. So, your milage may vary....

-dave lavery
Team 116


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