Nightmare Repairs At Competition

FIRST General Forum
1

So I just got back from the WPI Regional and I’ve got a story to tell. As I was preparing this thread, I saw 237’s awesome transmission repair and knew there had to be a ton more of these kinds of clever, dirty repairs in FIRST. So I thought I’d wrap our little story into a general thread so that the whole CD community can hear about different teams’ ingenuity under pressure.

http://i.imgur.com/2DOQvTg.jpg

So in our last qualifying match, after we had secured the number 1 seed, we went to hang for 10 and then suddenly our arm snapped all the way back. We had sheared a 20 tooth pinion on the arm. We swapped for our spare so we’d be ready for the first quarterfinal, and what do you know, it happens again. Perhaps we should have decided not to hang, but since the gear lasted through a regional and a half we thought we were safe…

At this point, panic starts to set in. We were out of 20 tooth gears, so a lot of the team thought we were done. Out of utter desperation, a few students and I dig through the pits trying to find ANYTHING that works. We ask any team we can find if they even used Vex gears. No dice. We dig through our own supply just trying to find anything that can work.

One of our mechanical students finds the 19 tooth, 3/8 Hex drivetrain gears, hands them to me, and asks if they will work. We have to try. I sprint the gears down to the machine shop for secondary operations while I tell another student to let the drive team and repair crew know that a spare is on the way. I run it down the street to the machine shop (it’s in another building) and then ask if they can broach it. They say yes, if they can get a hex broach. I ask them to bore it out to 1/2" while I go find one.

Scrambling through the pits, I explain to the students the situation and they quickly find our hex broach. Since I’m out of shape, it’s their turn to sprint to the machine shop with a part while I go explain more about the repair to the pit crew. I vaguely remember a member of the repair crew looking at me like I was crazy, but it was our only shot.

The gear makes it to the field with one match to spare and… it’s too thick. They hand it to me and I sprint right back to the machine shop, asking them to take 1/8" off the gear. Fortunately, the 8th alliance called a timeout for an unrelated reason, which was just enough time for me to run back with the gear and for our wonderful pit crew to get it back onto the robot. We decide to line up for the 2 point goal, because frankly we have no idea what will happen to our robot in autonomous mode, and we all cross our fingers and hope this modification does the trick.

It does. We scored in autonomous that match, and while we were done trying to hang, our teleop performance looked completely unaffected. Just one change in code and we had our 3/3 top goal autonomous working every single match after this one. If we hadn’t stopped hanging at this point, it would have looked like nothing had ever happened. This is one of my team’s (and my own!) proudest moments in robotics. We didn’t give up, we scrambled and improvised under pressure and it totally paid off.

So there’s our story. How about yours?

2

I’d say 1592 and 801’s beats everybody’s story for all time.

3

I can’t recall the year or the team and while not technically a repair I do remember a teams robot was shipped somewhere else for nationals and they had to build a new one from scratch

4

+1 to this.

My favorite emergency repair story is from 2009. We had an intake roller made from polycarb tube. It worked perfectly through two reginals, championships, and IRI, but during practice matches at GRITS (offseason competition) we collided with another robot and broke the roller in half. We hadn’t brought much in the way of tools or parts, so we thought we were done.

I and another student made a dash to a local hardware store and had no luck finding anything that could be substituted. Then the student found a piece of chrome sink drain that was a tight fit inside the polycarb tube. The hardware store was kind enough to cut off a piece of the drain tube, we also bought some super glue. Back at the venue, we covered the drain tube with super glue, and pressed both broken parts over the tube. We were back in business and ended up winning the competition.

5

In 2011 the gear on our arm sheared a few teeth. The one type of gear we needed, nobody else had. So instead of taking it off, we improvised. If we wanted to raise our arm, I would go from full forward to full reverse, and the inertia would move the arm up, the lost teeth would be skipped, and the teeth from the driving gear would catch with the unsheared teeth on the arm and raise the arm up. While we weren’t an effective scoring robot in Logomotion, we were able to get our arm up. The nightmarish part was for me having to go full-power forwards to full-power backwards with a top-heavy robot without tipping. I got it down after a while, but we spent a lot of time on the practice field working on me not tipping the robot over (which ultimately I did anyways).

6

Found it http://www.chiefdelphi.com/forums/showthread.php?t=27919&highlight=1396

7

This.

I won’t try to top the 1592/801 story but 1902 had a crazy repair moment at Atlanta in 2007. Before our final match on Galileo one of our BaneBot motors we used to power our arm released the magic smoke. (First time we had a problem with it all season.) We called the time out a raced to replace it. The problem was we had mounted an aluminum box around the motor that refused to come off, making the exchange a challenge.
With the clock ticking, and the field reset crew calling our robot to the field, one of our college mentors got out his hammer, stepped on to the robot cart, and began to persuade the casing and motor off as we were carting the robot to the field.
Luckily we were able to get everything fixed just in time for the match. We won the match, won the division, and got a trip to Einstein.
Still one of my favorite memories from my days as a student.

8

In 2011, our head programmer decided to build a new electronics board as a part of our 30lbs withholding allowance. It was a wonderfully compact design, and we were excited to put it on the robot at conpetition. However, he forgot to account for a pneumatic cylinder that was placed smack in the middle of where he planned to put the new board, so we spent our entire first day in Toronto fractically building a new one, and much of the next day trying to make everything work the way it did before we bagged the robot. We went on to win the regional with 1114 and 1503.

9

Paging Rich Kressly, Chuck Glick, or Mike Williams. I’d want someone more involved with the actual repair to tell the story of how they fixed our claw in 2008 after it broke during the last qualification match before we had to be on the field for QF1-1 as the #8 alliance captain.

10

My junior year on the team, 2006 Aim High (edit), The robot we shipped in the crate was far from perfect. The hopper to hold the balls was non existed the shooter kind of worked part of the time, and the electronics were out in the open. When we got to the Pittsburgh Regional and opened the crate there was a ton to do. Going out for our first match, everything was held on by zip ties and velcro straps. After 2 matches of not making any shots we had a team meeting, a few robots that were only dumpers were really good, and we had a vote to rebuild the robot from a shooter to a dumper. It was decided to go for the dumper, so a group of us started striping the robot down to its frame. Another group started going through all the spare parts we brought. we had angle, aluminum plate, lexan, and a ton of rivets, so we got to work. With some help from some other teams we cut the aluminum in half forming 2 triangles, while another group used a heat gun to bend the lexan into a shape that would work. After riveting everything into place onto the frame, we went out for our last practice math after missing 3, The robot worked pretty good we could pick balls up and dump them into the one point goals, but when picking up a few balls would fly right out of the hopper, and also at the end of the match we were back heavy and tipped of the ramp. Back in the pit we had a bunch of those fold up hampers, so we took and riveted one to each side of the hopper, tested and it worked great. Next we had to figure out how to stop tipping, we looked around for a bit and finally picked what to do. In the pit we had 2 steelface heads, our team mascot, cut out of steel for decoration. We bolted it to the front of our robot, and went for final inspection, we passed at the last moment.
I know it is not a nightmare repair like other teams have had but it is one that I will always remember, and I feel for teams like 1592 and 801 because I know it is not fun rebuilding a robot in one day. below is a picture of before and after.

I also remember one year a teams robot crate was shipped upside down and they had to rebuild, can’t remember the team or year though.

11

The name of the 2006 game was Aim High. Ramp Riot is an off-season event held by team 341 each November.

12

I’m not sure if this was a nightmare repair, but it is a good story.

In 2010, as a mentor and coach for 816, I had the pleasure of watching our robot go up in smoke during autonomous mode in one of our qualification matches. Initially, the autonomous looked routine, the robot began to move forward slowly as it always did and then drifted to it’s right. Initially, it seemed like a routine ‘the robot is being dumb again’ moment… And then it started smoking.

I frantically hit the E-Stop and ran out of the box to the side of the field to see Pete K (FTA at the time) on the opposite side of the field with a fire extinguisher. I think I shouted something like ‘No, wait!’ to him, and once the match had been paused/canceled (or before by some accounts) I got on the field and opened the robot’s lid to air the smoke out and found no fire.

Thankfully, since the match had been stopped, we had to wait the minimum 6 minutes to reset the field. Everyone assumed that we would take the robot back to the pits to fix whatever was wrong with it, but we found the problem fairly quickly right there on the field. Turns out one of the PWM cables going to the right side of the drivetrain shorted out and burned up most of it’s insulation. Some time after we found this, our ‘pitmaster’ was standing on the side of the field asking what we needed to fix the robot, at which point I shouted ‘PWM Cables’ at him. Something like 2 minutes later he came back with a ball of PWM Cables and we rigged the robot up to run without ever leaving the field… And we won the match too. Good Times.

http://www.chiefdelphi.com/forums/attachment.php?attachmentid=8948&d=1270046943

13

I remember this, walking around the pits in Philly 2008 and seeing the arm split in half. If I recall, you guys got it completely replaced with the spare in time to have a fully functional robot in the first quarterfinals match. It was quite impressive.

14

I haven’t been able to get my chiefdelphi fix since Tuesday and I’m jonesing… can you spare me a link to this story?

15

http://www.theroboshow.net/

It’s the first story in Episode 2.

16

Thanks!

17

We didn’t hurdle in the first quarter-final match, as we weren’t confident in our repair yet. We did participate in the match, run laps, and lock an opposing track ball in the corner for as long as possible. We managed to get a bit of testing between QF1-1 and QF1-2, and were back in full force in the second quarterfinal. Not that it mattered much against the 103+272+834 combo. They summarily trounced us.

18

Curious, can you post the gearing spec on your arm? Every reduction + motor.

Then also the distance to CG of the robot from arm pivot, and the weight of the non-arm portions of the robot?

For random knowledge, the trick of dropping a tooth will work in a pinch on most gear setups, but you introduce a LOT of backlash and I wouldn’t recommend it for high speed systems w/ lots of loaded direction change.

19

This. One of the best finals in Philly I have seen, since 2008.

I remember MOE doing some last second repairs at Philly in 2010. Not sure If they were nightmare-ish repairs though.

Also, can we forget 75 at MAR and (I think) BE? The robot split in half, and they still fixed it.

20

Sure, I’d be happy to. We are well aware that we heavily exceeded a reasonable load on an aluminum pinion.

Input: CIM
Gear Reductions: TB3 Reductions (15:60, 14:50, 14:50) followed by two custom reductions (20:84 20:84). The pinion that failed was the final 20 tooth pinion. TB3 gears are steel as is the first 20T pinion, only the final 20T pinion was aluminum. No, that isn’t backwards.

The arm failed both times when attempting to hang. Hanging hooks are roughly 2 feet from the pivot point. Base weight is about 75 pounds. I would say the CG is probably six inches forward of the pivot point (yes, it’s far back).