Quote:
Originally Posted by Tom Line
I'm looking forward to trying the ball shifters this off-season. We usually don't use shifting drivetrains because of weight, but that may change now. I would absolutely LOVE it if Vex can look into supplying a kit that allows fast reliable shifting without pneumatics. In fact, with a little innovation, it's not impossible for the same kit to work on the supershifters as well. I've seen a number of solutions. The most elegant I saw was a single window motor with spring loaded arms (Hot in 2012). The servos are simply not powerful enough to shift under load. I've seen very few teams use them for exactly that reason. We plan on putting the ball shifters on our robot for the off-season to test them out, and will probably look at a solution at that time (we don't have pneumatics on this year's bot). There was a fellow at MARC last year with a really nice sliding arm linkage made out of lexan that was along the same lines - just bolt on a window motor and go.
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Tom,
We were planning to adapt out window motor shifter setup for the VEX ball shifters, but unfortunately the new small robot dimensions did not allow for it to package between the CIMs. I'm sure if we had last years size requirements I would have been able to make it work.
Unfortunately, I don't remember the mentors name right now....but, the smaller window motor setup was designed by a mentor on 107. It was a very nice and compact design.
So far I have tried designs to use both (2) VEX 393 motor or the (2)AndyMark servo setups. We thought we were having issues with the 393 stalling out and frying our digital side car, so we switched to the AM servo setup. Unfortunately, with the amount of play in the ball shifter shaft I haven't been able to get a good push/pull lever arm designed that shifts effectively.
One thing I've been trying to figure out is how it seems the shaft needs 5/8" of an inch to fully engage high/low gear, but a 1/2" cylinder is used to shift it pneumatically. The pneumatic setup holds that shaft much more securely, so my guess is the play in the shaft is the reason we haven't been able to di it correctly.
We're still working on the design and have another one to try out...but have put shifter development on hold until all our other issues (climber) have been solved.