Our team the TIGERTRONS just did this our first time in the year 2003
In the past we found it very difficult or impossible to turn our robot in high gear with 4 wheel drive. This past years game we decided we needed to become very maneuverable so we had to change something...
So We created a pair of casters that were directly mouted to our stationary front axle. We then used a Globe Motor that was mounted to our frame. The Globe Motor also had a lead screw directly attached to the shaft.
The Globe then pivoted the castors on the stationary shaft. We also used a pair of limit switches to control the movement of the mechanism so that us drivers would not destroy it.
The only drawback was that is was rather slow. It took like 3-5 seconds to shift from 2 wheel drive to 4 wheel drive. Our front shaft also bent during one competition due to falling from verticle to horizontal on our castors that were down. We later fixed the problem by installing a solid 1/2 inch shaft instead of a hollow 1/2 inch shaft.
For pictures and more information please visit:
http://www.tahsroboticsteam.org/pictures.htm
http://www.tahsroboticsteam.org/robot2003.htm
I can try to get more detailed pictures of the mechanism if you want
just send me a pm or email at
rigdonbrad@hotmail.com