pic: Crab Module

[Clem1640]

I've just posted as a picture drawings of our 2010 pivot design. As Foster points out, these pivots have been through 6 competitions, 4 extended demonstrations and a lot of practice driving. The design has held up to abuse extremely well. Our 2010 robot was our team's first pivot bot. Being pushed or rammed sideways is no problem.

We began this design process last summer, so if you are looking to be able to use this next year, your timing is right. We started with a VEX-scale prototype (mounting a cRIO) on which we did motion-control and software development. Then went on to documenting the driving math. Finally we started designing pivots using Inventor. We went though 6 major and more minor revisions before we were ready to build.

I'd recommend that the transfer axle (flanged ball) bearings press in from the inside of the assembly, not the outside. As shown, they are likely to come out (in fact be pushed out on the gear side).

We used thrust bearings to take the axial loadings developed by the miter gears. Each of our miter gears is backed by a thrust bearing.

This allowed the use of roller bearings for the coaxial drive shaft. Since the roller bearings have a smaller OD than ball bearing races, we were able to keep the pivot tube 1" OD.

We also used a thrust bearing to bear the load of the robot on the pivot's top.

Hope this helps.