Nightmare Repairs At Competition

[Lil' Lavery]

At least that pizza was free...

[Rich Kressly]

Originally Posted by Lil' Lavery

At least that pizza was free...

You're your father's son, aren't you

[Chris Hibner]

This story has given me nightmares ever since it happened.

It was 2002 on Einstein, the last year at Disney. I was the field coach for 308 (The Monsters) back then and our alliance of 180 (SPAM) and 311 from Islip, NY made it out of our division after some rough matches.

Back in those days the matches were 2 vs 2, but the alliances had 3 robots. You had to play all three robots in each round in order to advance. The typical strategy was to have one robot be your anchor and the other two robots would swap. Our robot was the anchor of our alliance as we had the ability to quickly grab two of the goal and then lift them up to transfer the weight of each goal (at 180 lb each, if I remember correctly) to our robot. We could basically drive wherever we wanted once we had the goals lifted. We had a third arm to grab the last goal which would basically ensure us the win.

We were able to win the first round on Einstein in two straight matches agains a great alliance of 118 (Robonauts), 233 (Pink), and I want to say 144 (Who?), but I'm not sure about the third. It was on to the final round for the world championship!

The finals were set once 71 (The Beatty Beast), 173 (RAGE), and 66 (the Penguins back in those days) advanced in two straight in their semi-final. It was going to be epic. Team 71 seemed to be unbeatable, be we thought that we could lift the goals high enough to lift their robot's file cards off the ground (one last trick up our sleeve that we haven't shown yet). I couldn't wait.

Then, the nightmare occurred.

One gear in the gearbox on the left side of our drive train started to shift so there was only about 50% of the face-width engaged, and we didn't see it. The match started and we raced to the center of the field to meet 71 at the goals. A big collision occurred, and every tooth from the gear box in that reduction stage sheared off. We were useless as the left side of our drivetrain could transfer no torque. Needless to say, we lost that match.

In match two, SPAM and 311 went in while our pit crew tried to see if we could make a fix. In the 2nd match, SPAM and 71 had an even bigger collision at the center goal causing 71's goal grappler to break. SPAM and 311 were able to manipulate the goals with enough authority to win match 2.

One match for all the marbles...

Our pit crew couldn't replace the gear in time. However, since the gear had shifted to having 50% of the facewidth engaged, only 50% of each tooth sheared off (we were using aluminum gears to save weight). The pit crew pounded the shaft over so that the remaining teeth were engaged. The drivetrain ran, but I knew it wouldn't stand up to another collision with 71. When it came time to pick who was going to play and 311 (our alliance captain) asked if we could go, I told him that 311 and 180 won the last match, they should try it again.

Then, the 2nd nightmare occurred: 71 took themself out of the match, leaving 66 and 173 to play. 66 had plenty of torque, but they were a single speed robot. We had a high gear (about 10 ft/s to race to the goals), and an ultra low gear (about 1.5 ft/s for push once we got the goals lifted). I KNEW we could be 66 to the goals, get them lifted, and the match would be over. I ran to 311 and told them we could go against 66, but it was too late. The referees said that we had already submitted our two robots to the match.

Needless to say, 173/71/66 won the match and I've never came that close to being on a world championship team.

I tried to convince myself that "maybe the half-sheard gearbox wouldn't have even been able to drive." When we finally got the robot home, we just had to set it on the field and see what might have been. The robot raced to the goals, lifted them, shifted to low, and was able to push them into another robot with no problem. Oh what might have been. I've been haunted by that ever since.

I have pictures of that gearbox that were taken immediately after that first match ended. I'll have to see if I can find them.

Edit: I found the pics. Here's one of them:

[Lil' Lavery]

Originally Posted by Rich Kressly

You're your father's son, aren't you

Well, yes. I challenge you to find someone who isn't their fathers' son.

But I still remember being pleased we gave out enough of those fliers for Ed's to give us a free pizza. Then Chuck went and devoured it before I got any...

[Rich Kressly]

Originally Posted by Lil' Lavery

Well, yes. I challenge you to find someone who isn't their fathers' son.

A daughter? I digress...
this is a GREAT thread, and I LOVE Hibner's story.

[Brian C]

Thanks for the memories Chris. If you need a refresher try this link:

http://www.thebluealliance.com/match/2002cmp_f1m1

[iambujo]

Storm Robotics Team, 2729 had to do a fair amount of repairs for faults during the 2013 competition season so far, all of which carry some good and simple lesson's learned I think so I'll share briefly. The issues are not nightmares like some of the others in the thread by any means. [This is turning out to be way longer than I intended, but hopefully serves a purpose to someone out there ]

First, nearly all the issues are related to the ruggedness (or lack of) on our electrical system. In the 5 years of Storm we haven't had issues like this. Luck be it, or possibly because we were defended on much more this year, we had several cRIO reboots, router reboots, etc.

At MAR Hatboro Horsham, at the end of the competition (last match) our cRIO 'died'. 24V was verified but no LEDs came on when the bot was powered on. We had to pull the cRIO, bag it and give up. We later found that a single copper strand of wire, about 1/4 inch long had fallen into one of the cRIO module DB9 slots and lodged itself between a few of the pins, shorting them and the overall cRIO boot (would love to know the pinout of that DB9 connection to see how that is even possible). This was under the black DB9 cap which was installed. Our best guess is that the strand was sitting in the cap when it was installed. The cap had been vacuumed out once and then found in the shop vac, so possibly the strand stuck in the cap from static charge, was installed with the strand in it, and then the strand fell out later and lodged in the pins. Or it was sabotage. But for GP's sake we are going with bad luck [I wonder why NI didn't put a female DB9 on the cRIO side anyway. When the pins break the cRIO is toast, which has happened on our earliest cRIO]

At the MAR Lenape regional we had a cRIO reboot early on which was traced in the pit later (after another luckily good match) to the 24V+ wire coming lose in the connector on the cRIO side. We tightened it best we could, hot glued it and continued on. Unfortunately later that day we had faults that looked similar, in another qual match and in the Finals Match 1. The Field folks said it was a router reboot.

After the competition we studied the DS logs and determined it to be a router reboot in both cases. Wiring seemed fine from the PDB through the regulator and to the bridge, but we noted to make it more rugged at MAR champs. After further log analysis we saw some deep voltage dips on the matches where the router rebooted. The best guess we came up with was bad connections on the batteries or bad batteries. The Good news - we keep battery logs during the competition to help ensure we use charged batteries and we can identify bad batteries. The Bad news - the log wasn't kept after the competition, it never made it back to the school. So we can't prove which batteries caused the issue, but we checked and had 4 batteries with loose wires at the terminals. We replaced with better suited hardware and had no router reboots or cRIO reboots at MAR champs.
[Note - we plan on posting the full log analysis on CD with screen shots when we have time to clean it up and will use them as a workshop later this year with electrical and software.]
- The moral to this one is - keep (long term) your battery logs to identify problem batteries, check your wires often doing a visual spot check between matches, and whenever you think you have made your wiring 'strong' enough during build season, do some more! Inevitably something will fail when 120 lb robots collide, but you can prevent a lot of it. We learned that the hard way this year.

At the MAR championship we seem to have fixed our HH and Lenape issues, but instead saw some new ones. In QF Match 2 we took a not too memorable hit from an opponent, 224 in this case. You can see Electra (Storm's robot name for 2013) roll away in a pitiful retreat, dead for the match. In the pit we found that the power pole between the PDB and the regulator unplugged. Surprising though as the hit was quite gentle compared to others survived this year.
-The moral to this one - even though power poles are strong - zip tie them or use the locking pins! A simple zip tie would have absolutely prevented that failure.

We had another failure at MAR champs, with only about 10 minutes to find and fix. After a match Electra had a bad "let the magic smoke out" smell. We ran through tests on every system and all were functioning without obvious issue. We continued to persistently search for a sign, and finally caught it when we saw a shiny corner (from melted plastic) on a Victor 884 that controls the drivetrain. We removed it and opened it up, and it turns out that the Victor FETs had self destructed horribly, but it was still functioning at a unit test in the pit. Interestingly the fan 12V wire looked like it had shorted to an FET. Not sure what happened first, the FET failures or the fan short (or maybe the short caused the failure).
- The moral to this one - Don't ignore your nose, I doubt a smell that bad can ever be a good sign. Study your robot until you find the source, nobody knows it better than you. Never be complacent or the failure will just pop up later.

[vhcook]

Originally Posted by iambujo

-The moral to this one - even though power poles are strong - zip tie them or use the locking pins! A simple zip tie would have absolutely prevented that failure.

I prefer the BLOK-LOC clips for this.

[BrendanB]

During Week 6 at the Pine Tree Regional after two days of no hiccups with our autonomous 30 point climber our team struck horror in the quarterfinals.

During qf1.1 when our team went to climb at 30 seconds left in the game we lifted to level one just fine but our arm that lifts the hooks to the second bar stayed on bar one without rising to level two. Our team tested the system in our pit and it worked fine. We did however find a lose power connection to our climber and a questionable battery. Problem was assumed as a power issue.

During qf1.2 the same problem happened as the arm still wouldn't move from level one. We noticed our cable was unspooled meaning the arm should have been expanded but it was jammed on the bar. Back in the pits we noticed our pawls had come loose so when we hung the hooks became jammed on the bar due to the pawls being crooked. All caused by a collision in qf1.1.

Our team tightened everything down and ran to the practice field to test climbing. The arm worked fine but the winch was out of whack. As our team was getting qued for the semis we noticed our encoder had been knocked out of alignment and damaged. What ensued was the scariest 15 minutes of the weekend as both the competition and practice climber were taken apart to switch encoders. Thankfully one of the quarter finals went to 3 matches giving us some more time for surgery.

Once the new encoder was on we had no issues for the semis and finals!

[Mark McLeod]

Originally Posted by vhcook

I prefer the BLOK-LOC clips for this.

That's nice, I like that.
Thanks!

[iambujo]

Originally Posted by Mark McLeod

That's nice, I like that.
Thanks!

Agreed, I had not seen those before! Thanks for the info!

[C. De Vries]

We were going through inspection and had most everything checked off and then one of judges takes a closer look at our robot and says that we used a larger wire gauge. So our entire robot had to be rewired, putting all other work to halt while the electrical team scrambled to fix everything. Then of course there was the rapid swiss cheesing and filing of the corners. We ended up passing inspection moments before our first match (and here I will point out that we are a rookie team and we had the first match of the day) at exactly 120.0 pounds.

Also, please excuse my ignorance, but what happened to teams 1592 and 801?

[Alan Anderson]

Originally Posted by C. De Vries

We were going through inspection and had most everything checked off and then one of judges takes a closer look at our robot and says that we used a larger wire gauge.

I hope this is just a glitch in terminology, and not a description of an inspector requiring you to replace oversized wire with something smaller. The rules don't specify the required wire gauge for each branch circuit, just the minimum size of wire based on the breaker protecting it.

The confusion is that smaller size wire has a higher gauge number, and larger size wire has a lower gauge number. Saying "larger gauge" is mixing size and number descriptions.

[orangemoore]

Originally Posted by C. De Vries

We were going through inspection and had most everything checked off and then one of judges takes a closer look at our robot and says that we used a larger wire gauge. So our entire robot had to be rewired, putting all other work to halt while the electrical team scrambled to fix everything. Then of course there was the rapid swiss cheesing and filing of the corners. We ended up passing inspection moments before our first match (and here I will point out that we are a rookie team and we had the first match of the day) at exactly 120.0 pounds.

Also, please excuse my ignorance, but what happened to teams 1592 and 801?

This thread should help.
http://www.chiefdelphi.com/forums/sh...light=1592+801

[SRaymond]

at 2370, our tradition is to have the pit crew travel to the competition on wednesday for load in, the rest of the team arriving during practice day. We arrived at WPI for the 2012 game eager to see what our tank of a robot (affectionately named OverKill) could do on the field. Everything was going well right up until inspection time...
Our robot weighed 20 pounds over the limit. When the rest of the team (myself included) walked in around lunch, we came to see the robot not in the tank-like form we knew and loved with its 10 inch wheels for height over the mid-field bump, but rather came to see a machine that looked something akin to a truck with prius tires installed. We had to drop down to 6 inch wheels, and got so desperate to shed weight we ended up ditching one of the polycarb protection panels in favor of mesh netting. our robot played well, but it wasn't the same monster we dreamed of seeing on the field...