Quote:
Originally Posted by Electronica1
Ok, I will take you up on that. How does your shooter mechanism work? Your robot was moving so fast I could not really get a good view of it.
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Yeah, one of our points in the video is to kind of hide the robot internals to an extent, but I'm happy to explain a mechanism to you. At one point we used two of the legal van door motors and two Banebot 775 geared on Versa Planetary Gearboxes at 100:1. They drive sprockets that are connected to the camshaft at about a 1:2 gear ratio (I cannot remember the exact numbers here). The cams were machined out of 1/4" aluminum and slide onto a Vex Pro hex shaft that runs across the entire mechanism working as the camshaft. I have attached some images that depict the original shape of the cams as well as the mechanism as a whole on the practice robot. Of course, it being a practice robot, we have removed one set of our 3D printed spacers to shorten them down because they added a bit too much unnecessary stress to the mechanism as a whole but this is not an issue on the competition robot (which was built much better). The reason I said the original design of the cams earlier in the post was because we added one slight notch on each side that allowed the catapult to rest slightly when cocked to lessen the stress on the van door motors. We actually learned that it was possible to remove those two motors entirely (the 775s were doing all the work anyway) and the small notches prevent any possibility of back-driving. If you have any other questions relating to the details of the mechanism, feel free to ask; I'd be happy to answer them.
Quote:
Originally Posted by Andrew Lawrence
Beautiful machine. Your swerve seems a bit faster than usual - what speeds are you running it at?
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It's not really all that faster, actually. The only change that was made was to switch a 12 tooth sprocket out for a 16 tooth so they could fit on a 1/2" hex shaft. The gearing farther down the line was changed to compensate (gearing was changed from 9.5:1 to about 9.3:1. The only real differences lie outside the drive train itself. This year's robot was designed to have an extremely low center of gravity (about 4" off the ground) which adds to an overall better drive base. Last year's robot was designed to have a 40 lb climber stowed away underneath, which when removed meant the robot was very tippy and had poor driving performance. Our 2014 robot also has improved programming for the steering modules (finding shortcuts for rotation of the wheels to prevent full 180 degree turns unless they are necessary, etc) and the parts were machined and assembled with a much higher standard in quality than in previous years. We really tried to put emphasis on building a finished product rather than what should be a complete prototype robot (we are currently fixing what would normally be our competition robot but is now our practice bot because we built two for this purpose). Our competition robot is built with an entire robot of experience behind us, so naturally it performs much better than even we expected of it!
P.S. To answer, we run at about 12-13 FPS in reality [geared for about 16 fps, but stress is a real thing].
Thanks for the questions, I hope I answered them fully! Please do not hesitate to ask any other questions about our robot, as we would be glad to answer them. I am more keen on answering mechanical questions and I'm sure Jefferson will be on top of any questions regarding the robot's programming time permitting.
-John Taylor Novak
23-02-2014, 02:55
Innovative ideas as always!
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