Saturday, September 29, 2018

Icewave 2018 Recap Part 2 - The First Match

Warning: This post contains spoilers! If you have not watched our match with Vanquish, you should come back later and read this after watching! 

Getting Settled In

The BattleBots 2018 season was filmed over 2 weeks in April of 2018 in Los Angeles.  We arrived early in the morning after driving most of the night and began to set up our pit area.  We were pitted right next to Mohawk, Minotaur, Hypershock, and Blacksmith.

Being familiar with the same robot for 3 seasons paid off and we passed safety quickly.  

Waiting outside at the Test Box for functional safety inspection.

We moved on to taking pictures.  Here you can see how the TV crew gets some of those amazing intro shots in the tunnel. 

 The bot and team photos were taken by longtime BB photographer Dan Longmire.  

First Matchup:  Vanquish

Going into this match, we weren't sure what to expect.  Vanquish is a relatively new bot built by Jack Tweedy from the UK.  We felt pretty prepared and comfortable with Icewave, but Vanquish does have a thick steel wedge on the front, which historically has been very bad for us.

Our only real preparation for this match was to make sure our wedge was adjusted to scrape the floor.  

Walking one building over, we make our way to the arena with Icewave.  It is always very surreal getting lined up to fight backstage because the lights, sound, and audience are turned up to eleven.  We make our way into the arena, the referees prepare to start the match, but we learn that Vanquish is having technical difficulties and the match needs to be postponed.  We're instructed to keep Icewave close by the arena, so we park it near the bleachers and just hang out for a while.

Eventually Jack gets Vanquish running, but his weapon is having trouble.  We talked to Jack to ensure him he can have as much time as he needs to get everything working.  Eventually I was told by the backstage crew that our match was on, and Jack was ready to fight.  Our match gets started, and we get a couple decent hits on Vanquish, who seems to be holding up just fine.  Then we run into a snag...

(Photo credit:  Jon Bennett, Tony Woodward, Dan Longmire)

Well that's embarrassing

One thing competitors know about, but most TV viewers don't see, is what happens when two robots get stuck together during a match.  You can see in the last photo where we rode up on Vanquish's wedge and we became high centered.  With Icewave on top of Vanquish, Jack was also having trouble moving, so the fight was at a standstill.  The two bots were stuck together, so the match was paused per the rules (Rule 7.4.7 here).  Thanks to clever editing, we didn't get to see this bit of shenanigans on TV, but a lot happened here.  With the match paused, the co-creator of BattleBots, Trey, enters the arena to separate the stuck robots.  Before doing so, he asks me if I can remotely kill Icewave's engine for safety purposes.  Naturally, I agree, knowing we can restart the engine after the doors are locked again.

The bots get separated, the box is locked, and they signal for me to restart Icewave's engine.  I push the button on the radio, but don't hear anything.  Normally it would restart immediately.  I knew something had gone wrong.  They unlock the arena for me to go inspect what is happening.  Immediately, I look under the engine and notice the chain that connects our starter to the engine is completely gone.  We find it lying over near the wall of the arena.  I explain the situation to the Trey, and he says I can’t fix the chain because that would be unfair to Jack (since it was probably knocked off while we fought), and would take too much time, but if I can start the motor another way he’ll allow it. This type of situation isn't exactly planned in the tournament rules and procedures.  They ask how much time I need to fix it, but that would be too long to hold up the film crew. I suggest a last ditch effort: We can try to restart the engine manually with a cordless drill.

I race back to our pit area to pick up the necessary bits and pieces to make this happen.  I've never started Icewave's engine with our DeWalt drill before, but I know it's not easy.  The engine has a lot of compression, even with the relief valve we use, and the drill might struggle.  On my sprint back to the arena, I see Will Bales and ask to borrow his drill as a backup.

I imagine this conversation with Greg went something like "Come on dude, you're killing us."

HyperDrill saves the day

Back at the arena, with the weapon safety lock in place, I try to operate the drill with one hand while operating the throttle with the other hand.  This proves to be difficult, and the drill seems to be too slow.  The engine will pop once or twice, but not stay running.  Trey offers to operate the drill while I operate the throttle to give the engine just enough gas to start.  Eventually the DeWalt drill starts smoking and we're ready to give up.  I suggest using the Hypershock drill as one last move.  Trey grabs the drill, pulls the trigger, and the engine starts immediately!

I am in shock.  The match is back on.  Just a few seconds later, we land the hit on Vanquish that has been replayed 100 times.  Vanquish is split in half.  Jack immediately gives me the signal that he's done, and I know the match is over.  Jack screamed STOP after that first big hit. The show editing made it seem like I might have been angling to go in again for another hit, but I was not.  The only thing I do actually feel bad about is ending the match so quickly after Jack had waited patiently during the whole restart craziness.

One of these cuts is probably the one that tore Vanquish's wedge completely off, taking half the bot with it.


Our first order of business was to figure out what happened to our starter chain.  Here you can see the bottom of our engine plate when it is separated from the base of Icewave.  The chain is near the bottom of the photo.  It becomes clear that our weapon blade is flexing enough upon hard impacts that it starts hitting things it isn't supposed to, like this chain.

Fortunately we have some time to work on a solution because our next fight is not for another day or two.  We know we can't prevent the blade from flexing, and we can't add more clearance without affecting a lot of other parts.  We decide the best course of action is to design a metal "ramp" part that will prevent the blade from hitting anything important even if it flexes.  Over the next couple of hours, we design the part up in Solidworks at our pit table.  We are fortunate enough to have Jason from Tormach with two great machines in the pits ready to make parts for all builders.  After waiting our turn, Jason cranks out our part with ease and we are ready for our next fight!  Or so we thought...

First sign of engine troubles

We continue combing over the robot to find any other issues that we may have not noticed at first.  Then we discover something bad.  Our engine crankcase has a hairline crack near some of its mounting points.

To provide some back story:  Our engine is from a Partner/Husqvarna K1250 saw and was never meant to have an electric starter.  It is a very lightweight engine because it is carried around by construction workers.  The crank case is made from cast Magnesium for strength and weight.  We have spent a stupid amount of time retrofitting this engine with our own custom electric starter system.  When we first built this version of Icewave back in 2015, we used to mount our engine using rubber shock-absorbing mounts.  The starter mechanism was not shock mounted, but designed to accept a certain amount of movement.  This turned out to be too much movement, and after much prototyping and testing, in 2016 we opted to just rigidly mount the engine to the robot through some plastic blocks instead of rubber.  We fought our two matches in 2016 with no problems.

After our Vanquish fight, seeing the hairline crack forming in our engine housing, it became clear that this was our new major problem that needed to be dealt with very quickly.  Fortunately we brought a spare engine.  Unfortunately, there was not enough time before the event to assemble the spare engine with all of its accessories, so we had to begin that process.  Simultaneously we also located and ordered a new engine crankcase from an Ebay vendor in Florida.  Finally, as a last resort, we also began fixing up the cracked engine:  Sand off the paint, drill a hole near the end of the crack to prevent it from spreading further, and epoxy the crank case back together so it can be curing for a while.

Doing our best to repair the cracked housing as a backup plan

The spare engine is red, which means it was made after Husqvarna acquired Partner.

Post-match interview in our pit area

That's all for this post.  In the next post, we get ready for our fight with Yeti!  Continue reading here.

Icewave 2018 Recap Part 1 - Preparing for the Season

Now that the BattleBots 2018 season is coming to a close, I thought it would be useful to recap the season from our perspective. If you have not seen up to Episode 19 yet, there will be some spoilers after this post. Since we haven't gone into much detail about each fight as they aired, I'll go back to the beginning here, since even some of our earlier season wins left us with a lot of work behind the scenes. Overall we are very satisfied with Icewave's performance this season, and we're excited for the next one!

What happened in 2016?
The 2016 season was very disappointing for Team Icewave.  We won our first match against SubZero, and then lost unceremoniously to Nightmare due to radio problems.  Neither match made it to TV, but at least you can watch them on the BattleBots YouTube channel:

Losing in a way that felt beyond our control was not something we could let happen again.  Most teams recommended ditching our Spektrum radio for an FrSky radio, so we did.  But that didn't seem like enough.  Other teams use multiple receivers to control various parts of their bot with one transmitter.  That didn't seem ideal either, since the transmitter is still a single failure point, and losing half your functionality is still pretty bad.  It was then I decided I wanted two completely independent radio systems, and I should be able to decide remotely which one to use.

Dual Radio Solution

Unable to find what I needed, I decided to make my own PCB (printed circuit board).  This board would go inline between two radio receivers.  It would allow for two independently-powered radio systems, and either system would power the board's logic.  One receiver could lose signal or power completely and the other would still function.  The system would default to using the primary (new FrSky) radio, but on command, would switch to receiving commands from the secondary (old Spektrum) radio.  The command would be triggered by two switches on the radio, which send specifically-chosen PWM values to the custom PCB to signal a switch-over while avoiding false positives.

Board design in Altium, ordered from OSHPark, and bringing it up from a bare PCB

Adding this board to our system also required some debugging, at which point we were able to see the exact signals being sent from the radio receiver to our speed controllers.  We figured this could also help us debug our interference problem from last season, if it still existed.  We started up the engine, and we immediately saw the symptoms:  the radio values were all over the charts.  This alone was not enough to cause the speed controllers to shut down, but it was very telling.

Eliminating the Interference

We began the process of elimination, replacing one part after another on the engine, starting with the likely culprits.  The engine has a spinning flywheel with embedded magnets which pass by a coil, called a magneto, to produce a quick spike of high voltage in the spark plug that is precisely timed to ignite the fuel in the engine.  Replacing the spark plug was an easy test, but didn't solve the problem.  Next we replaced the magneto and the problem disappears!  We inspect the old magneto closely and realize what happened.

An example photo of a similar magneto

The magneto is made of laminated sheets of metal.  In our first 2016 fight against Subzero, a small brass part rattled loose from inside the engine cover, spun around inside the engine flywheel, and eventually ripped the spark plug wire out of the magneto.  This little brass part also happened to hit the magneto laminations, but we didn't notice it at the time.  The laminations separated ever so slightly, which we can only assume turned them into little transmitting antennae for electromagnetic interference.  So the damage we took in the SubZero fight actually caused us to lose the Nightmare fight.  Amazing.

Getting Organized

We all recognized that a lot of last-minute, frantic work in 2016 put us in a bad position throughout the event.  Things like electrical wire routing and logistics at the event never get enough attention.  Inside our engine housing was a complete disaster of electrical components for the engine crammed in alongside poorly-routed wires and gas lines.  I set out to clean up this mess for 2018 with a custom electronics housing.  This would be machined out of a single block of plastic, and contain each electrical component in its own compartment with foam for shock mounting.  I designed everything in Solidworks before a single part was made.  This was crucial because this assembly had to fit around all of the existing components!  Here's what it ended up looking like:

More Spare Parts

This season we were told in advance that the fight format would be different.  Each bot would get at least 4 fights in the preseason before the tournament of 16.  To me, this changed the way I prepared significantly.  Previously, a catastrophic failure meant a loss, which meant elimination from the tournament.  Suddenly I realized I needed as many spares as possible for this year.  Over the previous two seasons, we had amassed quite a few spare off-the-shelf parts, but never really had the time to invest in fabricating spares of the custom things.  The night before driving to LA, I pulled an all-nighter to make as many spare parts as possible.  Since a lot of the parts were made on our CNC mill, I was able to make quite a few parts very quickly.  We also received our spare engine cover and wedge parts from our sponsor, Big Blue Saw, so it was time to weld them up!

Main weapon sprocket machined from 8"x8"x1.25" 6061 Aluminum block

Engine mounting plate machined from 3/8" 7075 Aluminum plate

Gearbox for engine starter machined from 6061 Aluminum flat bar

Laying out and welding a spare front wedge

Machining spare lower frame rails out of 6061 Aluminum flat bar

Packing Up

With as many spares as possible, it was time to pack the van and make the 6 hour drive to Los Angeles for the taping!  In my next post, we'll get to the event and start talking about our first fights!  Click here for Part 2!