[archiver]

Posted by Dodd Stacy at 1/22/2001 11:55 PM EST


Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.


In Reply to: Re: Ball Rollers
Posted by David Bryer on 1/22/2001 8:07 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.

: : tnx,
: : Justin Stiltner
: : Team #388
: : Epsilon
: : Grundy Va,

Take a look at the rear chain tensioning assembly on a bicycle derailleur (sp?). The chain runs zig zag around three "sprockets," if you call the little plastic wheels sprockets, too. Compare the direction of rotation of the middle sprocket in the chain tensioner with the rotation of the large sprocket up front, with the pedals on it (I don't remember the right name) - they are opposite.

You can adapt that concept to counter rotate your roller pair, using one continuous chain loop and 4 sprockets, 3 of them at one end with the center 1 of the 3 attached to the roller. Mount the other 2 so that the chain has a decent wrap angle around the roller sprocket and so that you can also use them to tension the chain.

(We also found that you can run the chain in a figure 8 like a belt if you make a sheet metal separator/guard where the chain crosses itself in the middle, run the chain pretty slack, and ignore the nasty sound it makes. And replace the sheet metal before it wears through. It's not your 100,000 mile design, but then that's not the game we're playing.)


Dodd