pic: 20's IRI Carnage

[KrazyCarl92]

Some more back story on this failure:

During build season we decided to use a single speed gearbox in our drive train because of our lack of experience as a group with shifting gearboxes along with our desire to keep on schedule. Given that our strategy was floor loading to pick up discs scattered around the field, we did not deem high speeds necessary anyway. The 11 fps gearing with direct drive from the kit of parts gearboxes to 6 in. wheels was a nice sweet spot for a single speed that would allow us to still traverse the field when needed, but give us decent acceleration and not trash our CIMs. To make this happen, we "West Coasted" the tough boxes from the kit and ran 1/2" hex 7075 aluminum shafts in our 6WD. We used the 6 in. wheels from the kit because they performed well in 2012 and we wanted enough clearance for the frisbees on the carpet. This robot was the most reliable one we have ever built. For example, in Connecticut we had 4 total minutes of repairs all weekend.

Fast forward to after champs. We were applying for IRI, and in hopes that we would get in we started planning improvements for our robot as a good summer project and a way to really push the envelope with our design. These added features included a hockey stick/window motor blocker, an 1114 inspired pneumatic shot deflector for shooting from the back of the pyramid, and a 2-speed transmission from West Coast Products. We realized that the strategy of Ultimate Ascent had evolved, and especially at IRI it would require all teams to be proficient at cycling if they hoped to be effective in eliminations. Our limiting factors as a team were our speed to traverse the field when cycling and the sub-optimal drop on the floor loading. We couldn't deal with the sub-optimal loading problem easily (4 sec. on average versus 1-2 sec. for most good cyclers at IRI), so we decided that speeding up our drive train while still protecting our motors and maintaining pushing ability would be important.

After getting all of these improvements finally installed with time before IRI, we started programming and drive practice. We got about 30 hours of solid drive practice in. By the end of drive practice, we were rather consistently hitting 5 cycles, sometimes 6, on an open field with our 3 disc auto from the back of the pyramid, along with cleaning up missed shots and scoring those with our end game hang. We also had a 4 disc center line auto that returned to our side of the field from the center line before anyone in the world got there in the first place...I really wanted to see that one in elims!

So then at IRI, we have our first match in Quals 6. We are with 2056 and 2826, and against 67, 359, and 3641. We knew we could not leave HOT entirely open for FCS, so we decided we would "puppy guard" the loading station. We would have our blocker up on them when they went to full court shoot, but in between pick up the deflected shots and alliance member misses and/or score our discs we had collected. As a result of this strategy we found ourselves in a pushing match with 359. Our robot was up on end at one point and then slammed down, presumably breaking one of our KoP wheels. The wheel ripped in half. Then our dog from our shifter shattered into 3 pieces, perhaps because the gearbox was subject to abnormal conditions in low gear due to the broken wheel.

After the match, we quickly realized the dog was missing and started asking around for assistance. Luckily Team 868 had a spare dog for this shifter and gave it to us, along with helping us find the necessary tools for the job. When installing this dog, the aluminum threads for the 4-40 bolt hole stripped out using the non-torquey end of an allen wrench. We tried an 1/8th" roll pin, but the hole for the pin was drilled too large for it to grab. This spare dog subsequently shattered because of the oversize hole. At this point we began trying to lock our gearboxes into one of our gears in hopes of working Friday afternoon. More replacement dogs were nowhere to be found because the WCP dogs go on a 5/8" hex shaft, unlike the 1/2" AM ones. None of our jobs worked, so Friday evening the decision was made to go back to our original single speed gearboxes that worked all season. We got back working Saturday morning and were finally able to put up 70, 67, and 49 points in our 3 matches.

Looking at the wheels after the competition, we can clearly see bubbles in the plastic in the places where they broke. I spoke with Andy Baker at the competition and he did say that AndyMark will be looking to improve the wheels next season. This was not the first time this season the wheels have cracked, but it is the first time they ripped in half like this.

The WCP gearbox was actually a success. After 30 hours of drive practice, the gears held up great and our drivers love the fast, smooth ride. The shifting did bring an added layer of complexity to the failure which meant a very serious failure, but the dog only failed when it was subject to conditions it is not designed for. The prevailing theory is that rather than being traction limited, the gearbox was now limited by the stall torque of the motors in low gear. At least until the dog broke. This is roughly 3 times the torque that the dog is intended or expected to handle.

Thank you to Team 868, especially Charles, for your assistance in trying to get us back up and working. Even though we didn't pull it off for the 2-speeds like we had hoped, it was really awesome to have competitors like yourselves helping us out even though we had a match against each other shortly after. THAT was gracious professionalism. Also thanks to 11, 71, 195, 1310, and 1625 as well as Chris Picone and Nick Lawrence for lending us tools and brainpower for the attempted repairs throughout the weekend. And thanks to 16 and 27 for being understanding pit neighbors when our stuff undoubtedly spilled into your space during the turmoil that was the Friday of IRI 2013 for Team 20. Additional thanks to all of the great teams and volunteers who provided the most inspirational product on that field. We were hoping to really help raise the level of competition, but we came away with a great experience nonetheless.

It was disappointing to finally earn our way to an event that my teammates and I have been dreaming of competing in for years, only to lose more than half of our competition within the first minute. It felt like we never got the chance to show the world what we had worked so hard on. Even more embarrassing was being the team to show up to IRI that didn't move. I really didn't get the chance to enjoy IRI this time around until the eliminations started (which were spectacular, by the way!) because of the stress surrounding the robot failure. It was encouraging to finally see our robot working well Saturday morning, and we got quite a few figh hives. You can bet we will be working hard in the next 9 months to earn our way back next year and hopefully actually compete in 2014.