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We decided quite early on to release the full model of Bombshell once the season had finished airing.

The full CAD model can be downloaded at:
http://www.chaoscorps.org/blog/wp-content/uploads/other/BombshellV1CAD.zip

A few notes on each major system

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Drive Pods

We were happy with the drive system performance, however the heavy gear modification required to stay within weight combined with the modifications needed for the outer plate (the CAD model of the A28-150 we had was 0.06″ shorter than the real motors so we had to pocket the rear plate so everything would fit together properly) and the slot-on end caps (which warped a bit during welding) made assembly of the drive pods a bit of a pain. We’re working on an updated design for Bombshell v2 that will address the issues found during the Bombshell v1 build.

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Center Pod

Overall this pod worked quite well, though based on the damage received we can save some weight in this portion of the bot. We’ll also be looking at tweaking some of the wire paths to minimize the chances of flames reaching our electronics section again.

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Axe Pod

We were seeing enough losses in the worm gear stage that we suspect it was robbing the axe of a decent amount of power. We’re looking at a new geartrain setup that should result in a significant power boost.

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Horizontal Spinner Pod

We were quite happy with this weapon, our main focus for future upgrades will be on fine tuning the weight balance, making a more robust leadscrew mechanism (we had the gearbox on the DeWut pop out of gear due to shock getting through the system) and having a few bars cut for specific purposes.

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Lifter Pod

The frictional losses from the worm stage kept us from using this weapon during season 2. We’ll be doing some major powertrain upgrades for Bombshell v2 to get rid of the friction losses and up the overall power.

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Vertical Disk Pod

Performance of this pod was good enough that we don’t have that much that needs to be changed. We are looking at moving to single piece disks and having a few disk types that are suited to particular opposing weapons. Beyond that, there will be a bit of fine tuning and general cleanup of the things that were rushed during the final stages of the build.

If you’ve not seen our fight with Red Devil and you don’t want to be spoiled you should stop reading before the Post-Fight Analysis section.

Pre-Fight Activities

With Red Devil as our opponent we had two weapon systems we thought would be well suited to the match, either our lifter or the vertical disk module. In the case of the lifter we had performance concerns due to the friction losses in the geartrain, so we opted to focus on preparing the disk. The two major tasks ahead of us were replacing some structural parts from the drive pod that Cobalt damaged and fine tuning the feeder wedge for the vertical disk. One odd quirk of our drive pod mounting is that the shock mounts allow the entire center pod to lean toward the center of gravity, which meant that the feeder wedge functioned like a hinged wedge while being very securely attached to the chassis. By slowly grinding away at the wedge we were able to tune the portion of the weight dragging on the ground, letting us keep a ground scraping wedge while keeping a high percentage of the weight of the bot on the wheels.

As usual, we waited until it was time to head over to the arena to reveal which weapon we were going with, though  I doubt which weapon we used would have had much influence on the configuration Red Devil went with.

Strategy

We watched the fight between Red Devil and Witch Doctor and knew that we wanted to minimize the chances of the same happening to us. We were less at risk due to the battery positioning, but anything can happen in the box. This meant our first goal was to reduce Red Devils mobility, so we’d be going after the tracks. If battering the tracks wasn’t enough, the next target would be the tube at the back that links the three major sections of Red Devil together.

Post-Fight Analysis

That was not quite how we wanted things to go. We did manage to get the win and prove that with the existing judging criteria it is possible to win if your weapon fails early, but it’s certainly not easy.

So, what happened? An early design decision turned out to be a poor one. We’d opted for battery connectors where the wires were soldered into place, and due to the power pulled by the weapon one of the solder joints reflowed and the wire detached due to the on hit Red Devils track pod. Once that happened we had to make the best of the situation and use the wedge and now non-spinning disk as a battering ram. We run two parallel sets of batteries in Bombshells drive system and at some point during the fight one of those also detached. This meant we were trying to pull ~600 amps from a single 8s 5ah battery pack for an unknown duration of the fight, and that pack finally had a connection reflow right as the clock ran out, which narrowly avoided us being counted out. Those final two packs were no longer safe to use leaving us with a bit less than a full set of spare batteries and a lot of connectors to rework.

We didn’t have nearly enough connectors to swap to a new type before the next fight so we set to resoldering all of the connections and stress relieving all of the joints to reduce the chances of a wire detaching in our next fight.

As with the last post, this one will cover the results of our fight. If you haven’t seen Bombshell Vs. Cobalt yet you can view it in full here:

Pre-Fight Activities

While we may have lost the fight with Complete Control the damage was quickly repaired. This allowed us to move on to preparing our Adjustable Height Horizontal Spinner Module for action. The big task with this configuration was to get it driving as well as possible on the BattleBox floor. The unusual weapon layout meant that the center of gravity was actually forward of our front wheels, which as you may expect resulted in a rather difficult to drive bot. We spent a good bit of time fine tuning our outriggers with an angle grinder to minimize the chances of us getting in a spot where our rear wheels and the outriggers were keeping the front wheels off the ground. We also kept up preparation/fine tuning activities with our other weapons to keep the Cobalt team guessing as to exactly what they’d be fighting.

It took a good deal of time to get the outriggers set up right, and even then we were not thrilled with how the weight balance was. Luckily the AHHS Module was not our heaviest weapon so we had some weight margin to add ballast to the rear of the bot. Adding ballast consisted of melting a lead hammer into the back corner of our wheel guards and running a bolt through both to help retain the solidified lead lump. (Special thanks to Rob Masek from the Lucky team for the hammer “loan”)

With that detail sorted we were ready to fight.

Strategy

There wasn’t any doubt which weapon we were going with for this fight. The AHHS Module was designed as a non-wedge means of combating powerful horizontal spinners. The height adjustment allows us to target fragile components at a range of heights during a fight, effectively functioning as a 42″ scalpel.

Our goal in this fight was simple: Get the bar lined up with Cobalts weapon chain and break it.

Post-Fight Analysis

After seeing the Cobalt team having a strategy session with another team prior to the fight I knew there was a decent chance they’d have an approach that was a bit more complex than run straight at us with their weapon bar. Once the fight started, my suspicions were confirmed. Instead of leading with the bar they were backing into our bar, trying to either stop it or destabilize us to the point where they could whip around and take a huge chunk out of our armor. Overall, a pretty solid strategy that easily could have worked out well for them.

What I don’t think either team expected was that Bombshells bar would skip up their wedge and drop down onto their top armor pulling massive chunks out of their wheels. As soon as I realized what was happening the plan shifted from going for the chain to trying to keep chunking their wheels. This continued for a bit until Cobalt stopped. Part way through the count they started moving again and one of the last hits finished off most of the screws holding their top armor on which made it possible for us to bury the bar deep into their chassis, hitting the shaft on their brand new weapon motor.

We didn’t make it out of the fight unscathed, as we had to replace a drive motor, the outer frame rail for a wheel pod, a few wheels, and our wheel guard due to damage taken during the fight. Luckily the design of the bot allowed these parts to be swapped fairly quickly and once again we were able to turn things around for the next fight without cutting it terrible close.

 

Up next, we take on Red Devil, a bot which took out its last opponent by cutting directly into one of their batteries and flipping it over.

If you’re taking the time to read this then you’re likely interested in competing at BattleBots. If the Season 2 application process is anything to go by, you’ll be competing with hundreds of teams for a spot on the bracket, and it absolutely is a competition. You’ve got to convince BattleBots and ABC that your team and your bot should be on the show instead of potentially hundreds of other applicants. It’s not an easy thing to do. With that in mind, here are a few of our suggestions for how to put yourself in the best position for Season 3.

 

Design Something Cool

BattleBots is both a competition and a TV show. A dense metal box with a powerful spinning weapon may be a good way to win a fight, but you may be one of 50 teams submitting what is essentially the same design. Find some way to make your entry stand out. Play with geometry, try some interesting or unexpected components, add some color. The selection committee is going to be reviewing hundreds of designs so you want to have something in the design that will make sure it sticks in their minds.

 

Build a Proof of Concept For Risky Systems

Coming up with a wild concept for weapon operation or robot locomotion is great, but if it’s really something that’s uncommon or outright unseen in combat build some sort of proof of concept for your application. The people on the selection committee don’t know you and don’t know what you are or aren’t capable of, so show them. “Yeah, it’s cool, but will it work?” is only slightly better than not making an impression at all when it comes to your design.

 

Have a Cohesive Style

Whether it’s the look of the bot fitting the style of the team, or the look of the bot driving some team styling it can only help to have the look of the bot and team align. This doesn’t mean you need to dress up as 50’s sci-fi robots because you’re applying with a bot that’s covered in riveted, unpainted metal, it means that you should spend a bit of time thinking on how you can make the team look like they belong with the robot when it comes time for team photos. Jeans and a t-shirt can work, but putting some effort into a cohesive bot-team combination makes an impression.

 

The Competition Doesn’t Start When You Get to the Arena

We took an approach to Season 2 that viewed the BattleBots competition as three major rounds. The first was the application process, where you’re showing that you’ve got the design skills and team that can both pull off the build and manage some level of stage presence at the event. The second is the build season, where you’re proving that you’re capable of delivering on the promises you made in round one. The event itself is round three, where it all comes together and if you managed to make it through the second round with what you promised, you now get the chance to put it in the box and put it to the test.

 

Start Planning and Designing Now

If you’ve got an idea there’s no time like the present to do the planning and design work. The earlier you start on this side of things the earlier you’ll find any issues and earlier you’ll be able to resolve them. This isn’t the time to start buying parts or building unless you’re planning to build the bot no matter whether or not your application is accepted, but everything that goes into the bot prior to buying parts or cutting metal can be done now and will save you time during the build season.

 

You don’t have to do any of the above, but from what we’ve seen keeping the above in mind while preparing your entry will put you in a better than average position when it comes to applying for Season 3. Best of luck and we hope to see you in the BattleBox.
Don’t forget, applications for Season 3 are already open at http://registration.battlebots.com/ so if you’re serious about entering, go there and start filling out your application.

What a fight. For those that haven’t seen it yet, I’d suggest coming back to this post later as I’ll be talking about the results near the end of this post. Before that though I’m now able to discuss the activities leading up to our match with Complete Control and the approach we took to the fight.

Pre-Fight Activities

We found out about our qualifying round match Sunday night, and with the fight not being scheduled until Tuesday at the earliest we had a lot of time to prepare. The thing is, so did Complete Control, which happened to be our pit neighbor. The Complete Control team was curious to know which weapon we were going to select for our fight, but we couldn’t just tell them. We spent most of Monday swapping weapons, testing, fine tuning, and swapping weapons again while we watched them work on counters for each new weapon we’d put in the bot.

Things continued like this for the better part of the day and around dinner time one member of the Chaos Corps went out on a small shopping trip. When they returned the supplies were hastily staged in our bots shipping crate and work continued. A bit later in the evening Julie made her way to the crate and wrapped the cardboard box you saw us bring into the box. Once the Complete Control team had all left their pit and we’d wrapped for the evening the gift wrapped box made its way to a prominent position in our pit.

Tuesday came around and while we continued with our weapon testing and tuning we couldn’t help but notice frequent glances at the gift wrapped package in our pit. Eventually we got to the point where we had to pick which weapon we were taking to the box. With that, we loaded up along side Complete Control and made our way toward the arena, box in hand. Our initial plan was to load in with the box and pull it at the last moment, handing it to Derek as we assumed based on last years “situation” that loading into the arena with a mystery box would not be well received. We were then told that, so long as there was absolutely nothing in the box we would be able to leave it on for the fight. I don’t recall the exact words, but the general impression was that if we had hidden a net in there we’d be in a world of trouble. With that, the box was thoroughly inspected, the combined bot weight was checked, and we prepared to roll into the arena as the final fight on Tuesday. Quite suddenly there was a hissing noise and an unexpected smell. Complete Control had just hooked up their flame system but something was clearly not right as propane was venting all over the place. Complete Control was pushed outside to let it finish venting somewhere less enclosed and due to the amount of flammable gas in the air the fight was postponed until Wednesday morning. We briefly contemplated swapping weapons again but decided against it as we’d had our fun.

Strategy

The qualifying rounds are a bit odd. With two ways to make it to the next round it gives the opportunity to gamble a bit on strategy, which is exactly what we did. With four weapons to choose from and three being reasonably suitable to fight Complete Control we had plenty of options.

1: The Vertical Disk

2: The Lifter with Short Fuse

3: The Axe with Short Fuse

We also had the overall tournament structure to consider. There were a lot of nasty spinning weapons in the bracket this year, so in the fight with Complete Control we wanted to position the loser for the wildcard, as that would potentially mean one less vicious spinning weapon in play. With all of that in mind, I thought back to a small scale version of essentially the same fight and what I still consider to be one of the most exciting fights I’ve had, Nyx Vs. Uberclocker at Motorama in 2015. ( https://www.youtube.com/watch?v=pKcxtoiEbRg )

What you may notice in that fight is that Uberclocker does not, in fact, have a propane flamethrower.

Still, the axe seemed like a good choice to meet our goals.

• Capable of winning the fight
• Likely to put on a very good show
• The loser would likely leave in good condition for the wildcard selections

It didn’t hurt that the axe also allowed us to run Short Fuse and it seemed like a waste to build the thing and not use it.

Post-Fight Analysis

If it wasn’t obvious by the title of this part, I’ll be discussing the results of the fight starting on the next line. If you haven’t seen it yet and don’t want spoilers now would be a good time to stop reading.

The match didn’t quite go as we had hoped, but overall I think it was a pretty entertaining fight. We put a few holes in Complete Control, Short Fuse didn’t explode, and when it all was over Bombshell was still in great shape. In total the damage consisted of two melted PWM wires, a charred receiver, and some slightly melted wheels. The repairs took about 15 minutes once we were back in our pit. The smoke and “oil” you saw in the fight were from the urethane axe bumper on the front of Bombshell which started dripping and overall made a terrible, goopy mess all over the top of Complete Control. The axe did manage to get in a couple of good shots and put a few holes in their armor, but even with two shots into the center cavity on Complete Control we didn’t find anything quite vital enough to tip the fight in our favor.

That leaves one question: Did we do enough to get a wildcard slot? I can’t tell you yet, so you’ll just have to tune in next week to find out.

They looked so pristine before the action began. How do they look now? Watch BattleBots starting Thursday June 23rd at 8:00PM on ABC to find out. Be sure to catch the preview episode Tuesday May 10th at 10:00PM on ABC as well for some rumble action.