I’ve said it before and I’ll say it again: I was very pleased with Cannon’s second-place performance at Motorama. Still, its three fights against the eventual champion, Low Blow, highlighted some severe design flaws:
Exposed wheels. This is probably the single biggest flaw a robot can have.
The ball bearings pushing against the sides on big hits expand the beater holes.
There was no firewall; parts could be ejected from inside the robot into the blade.
Slow drive motors. 22.2:1s would have been a much better choice.
The scale was hardly Cannon’s friend, so figuring out how to add more material to the robot without adding any weight will be a challenge in and of itself. However, the first (and easiest) place to look is the wheel hubs. Cannon used aluminum “Dave’s Hubs” to hold its wheels on. Much lighter alternatives exist, such as the FingerTech Robotics Lite Hubs. Switching to the Lite Hubs will save over half an ounce off the next version of Cannon. That is more than enough to get started.
The next place I will look for weight will be the back of the robot. The old back weighed about 0.6oz and was made of 3/32″-thick garolite. Although stiff, garolite is about twice as dense as UHMW and is very brittle. The next Cannon will use a piece of (likely 1/16″-thick) UHMW that wraps around the back and protects the wheels. Kitbot creator Pete Smith gave me some UHMW bending tips at Motorama that should mean the clearance between the wheels and the UHMW is better on Cannon than it is on Coercion. Actually, I’m not sure Coercion actually has any clearance!
I put together a quick sketch of my thoughts for the next version of Cannon:
I am not a very talented artist.
The new firewall will be bolted to the side rails, which will help to make the entire robot stiffer. I will make a groove in the sides so that the pieces fit together relatively snugly.
I also sketched the side rails (remarkably well). I think I might apply to art school if the whole top-ten school in the world thing doesn’t work out.
Note that the pockets are bigger and I have added holes for the firewall. Also note that the hole that will hold in the weapon bearing has been enlarged. This will allow me to put in a custom bushing, which will increase the surface area inside the hole and keep it from enlarging.
The next step will be to design the firewall and do more weight calculations. I’ll then need to order parts. Unfortunately (well…fortunately), I will be in Washington, D.C. from March 9th to the 16th, which isn’t conducive to robot design work, and over the next week, I’ll be busy getting ahead on schoolwork to get ready for my week off: not much will get done. Still, it feels good to finally put some of the ideas I have come up with on my blog.
Keep checking back–Bot Blast registration is up on the Builders’ Database. I’ll be taking Cannon, lolcat, maybe Coercion, and maybe Amatol if one of my friends wants to drive it.
As usual, fighting started way after the already relaxed beginning time of 1:00PM, though I don’t remember exactly when. I got through all my safeties with minimal problems; the only issue I had across all three robots was that Cannon was a smidgen overweight. I fixed that by enlarging its connector hole and liberally grinding the underside of its top with a Dremel tool. I also removed some screws. The 0.3oz literally fell off!
My first fight of the day was with Cannon, against Toni Fowlie’s antweight brick bot, Malicious Mule. I was relatively unsure of how Cannon would perform, but I was glad its first fight would be against a robot with no angled sides and no active weapon. I spun up and hit the Mule gingerly a few times. When I saw Cannon could survive its own weapon, I started hitting harder. What I found astounded me: I had truly built a cannon. I was able to send Malicious Mule flying all over the arena. Needless to say, I was stoked. I also won by knockout.
After the battle, I noticed two problems that I know I will need to fix in future Cannons:
The UHMW sides are not strong enough to withstand Cannon’s hits. The ball bearings that support Cannon’s beater got pushed down. In the future, I will enlarge this hole, put something larger and stiffer in it as a bearing support (likely a small 7075 bushing), then mount the ball bearing inside of that.
The battery and electronics like to flop around, and there is no front firewall–the only thing between LiPoly and titanium eggbeater at 13,000rpm was a few pieces of duct tape. I will need to fashion a firewall.
Mercifully, lolcat’s first fight was against a similarly unweaponed bot: my buddy Sean McKeown’s brick, Gyroscope. Gyroscope was put together at the last minute; it weighed in at a relatively anorexic 100g or so. Lolcat had no trouble throwing it skyward. It was another victory for my trusty beaters.
After I fought Sean’s fairyweight, my next opponent was Joey’s undercutter antweight, Swamp Woman 2. As I own a robot with exposed wheels, the prospects of fighting an undercutter scared me. I also had no idea how strong my weapon was–would it be able to hold up? I spun up at the beginning of the match and decided to keep the beater pointed at the other robot. The strategy worked: a big hit sent Swamp Woman reeling back and the next one was lucky–it removed a wheel. Cannon won by tap out.
After Swamp Woman, my next match was against Demise with lolcat. This fight, although it was my first loss of the tournament, started out very well. I delivered solid hits and managed to keep my beater pointed at Demise’s enormous, 50g spinning disc. Unfortunately, Demise eventually caught a wheel guard, breaking it and destroying the gearbox it was meant to protect. I was not able to hit Demise much more after that, and I lost by judges’ decision. What I learned in this fight:
Lolcat wasn’t quite driving straight, and this was a big flaw. I need to make sure everything is either trimmed or aligned well enough that the ‘bot will drive in a line. This may require new side rails.
ABS wheel guards are terrible. I will replace the terrible ABS wheel guards with good, 1/16″ UHMW ones.
The beater assembly is surprisingly strong. It went blade-to-blade against Demise with very little trouble.
Before Cannon fought again, lolcat had to take on another challenger: Tenacious Tinkerbell, a smaller version Malicious Mule. The whole tiny rematch thing was extremely cute. Lolcat’s driving woes continued; I was not able to deliver as many hits as I should have been. Still, I stayed on the offensive the whole time and managed to win the judges over enough to get the victory.
Cannon’s next match was against the reigning antweight champion, Low Blow. This was easily my favorite match from Motorama. I hope the Cannon-Low Blow rivalry continues into the future. We wound up fighting three times during the course of the tournament (which you’ll read about later) and every match was wildly entertaining because it showcased each bot’s strengths so much. Low Blow is clearly built very well and is able to deliver big hits. Cannon is apparently built very well, too, despite the duct tape that holds in its juicy electronic guts. Cannon also tends to act like a bouncy ball around undercutters, and based on this fight, is able to send robots into the ceiling. Woo-hoo! After trading big hits, Cannon finally caused Low Blow’s blade to strike its own body, leading to a tap out.
With that fight taken care of, Cannon was guaranteed third place. The next fight was lolcat vs. Keres, a very nice-looking undercutter bot built by a person who gave me some invaluable advice about Coercion and Cannon’s weapons, Mike Jeffries. Mike recorded every single fight at Motorama, and I am featuring his videos in this event report. Click here to see the rest of the videos on his YouTube page.
Unfortunately for Mike (and fortunately for my cheezburger-loving, miniature eggbeater), Keres had taken a huge amount of damage from Demise, which wound up going undefeated and winning the tournament. Keres’ weapon wasn’t functioning, so all I had to do was hit, hit and hit again. I did the best I could with my shaky drive train. It was enough to get a nod from the judges. Lolcat finished 3-1 and took second.
In the third-place match, Cannon fought Algos. This was a tough one for me: Cannon’s drivetrain was far more decrepit than I thought it was after the match against Low Blow and as such, my robot was extremely slow. Adding insult to injury was Cannon’s seeming inability to bite on Algos. I did get lucky and manage to take out one of Algos’ drive wheels. The result was a nail-bitingly close judges’ decision after I did my best to stay aggressive (though I think I lost on that front) and was able to dish out more damage.
The next two fights were antweight finals matches against Low Blow. I’ll be upfront about it: I lost both. Reflecting back upon the experience, I wouldn’t say it was because I choked so much as that Low Blow was probably the better robot, even though I had already beaten it. It was also driven far more cautiously; I usually stay aggressive but my aggression did not pay off for me.
In the first match, I managed to keep things close, but the hits favored Low Blow and I eventually lost a wheel. In the second, Cannon was in rough shape and I wound up tapping out after my power connector got unplugged. It was a heartbreaking end to a good run, but with a few changes (read: what I outlined above and 1/16″ UHMW wheel guards), I’ll be ready to fight Low Blow. If I’m not super aggressive, maybe I’ll come away with the victory next time.
Saturday morning arrived, and my uncle and I decided to go out to eat. We visited the Colonial Park diner in Harrisburg, which turned out to offer delicious food (as with every year past, I ordered the #7 meal, which is eggs and hash–robot builders need protein!). We headed over to the Farm Show Complex way too early, as we had done the previous day; my uncle is a very early riser.
After far too much waiting, Coercion’s first fight was against a bot from Georgia Tech called Parallelogreg. Parallelogreg was a parallelogram-style wedge bot. From the looks of it, it was put together very well: titanium sides and very sturdy wedges. I was worried–I didn’t want my expensive spinner to not be able to break it. Luckily, when the fight started, Parallelogreg flipped against the arena wall after a failed box rush attempt.
Every fiber of my being wanted to free him. I remembered thinking about how the culture of combat robotics had changed from gentlemanly competitiveness–think French and Indian War–to something a little more competitive, and how I resented that change. At the same time, we don’t stand in a field and volley fire one round at a time anymore; one must stay with the times. Despite the crowd’s pleas (and those of my conscience), what stuck out in my mind was a conversation I had with my father shortly before I left for Motorama. He made me swear I wouldn’t free anyone off the wall.
Promise kept. Sorry, Greg.
Coercion’s next challenger was another Georgia Tech robot (which was a little awkward after the wall affair). It was called The Hammer, and featured a horizontal disc. It looked pretty nasty, it spun fast, and it spun in the opposite direction of my blade. That assured a massive hit. I was able to get to know The Hammer’s builder, Dan Hammer, a little, and learn a bit about life at Georgia Tech. He seemed to be fond of it.
When the fight started, Coercion got up to speed, but The Hammer didn’t. I drove straight into the Hammer’s front, which seemed to kill it, but then I came back for more: I removed both of its wheel guards, and after my miraculously lucky hits were over, my opponent was motionless. The Hammer got counted out. Coercion, which had won a total of three fights before Motorama 2013 (1-2 at Moto 2012 and 2-2 at Bot Blast 2012), was 2-0.
Unfortunately, it looked like Coercion’s luck had finally run out. I was set to fight Shame Spiral, runner-up at Motorama 2012 and infamous spinner killer. The entire outside of Shame Spiral is hardened steel, and I knew it would be a tough nut (haha… Team Slammers joke) for Coercion’s blade to crack. The fight began as I expected. Coercion’s blade got up to speed, and it took Shame Spiral’s hits well. Unfortunately, there wasn’t much in the way of damage until one big hit removed half of Shame Spiral’s wedge. A few hits later, I maimed the other half of the wedge. I had to turn off the blade for a little while to allow my weapon controller, weapon motor, and belt to cool off, but after the blade got back up to speed, Shame Spiral stopped moving. Coercion got the win by knockout.
That took care of Coercion’s Saturday fighting. All it had to do on Sunday was beat Dr. Super Brain to get a guaranteed third-place. I was amazed.
As I mentioned before, Coercion started off the day with a match against Dr. Super Brain. I actually fought Super Brain last year and lost the match; I was concerned about a repeat. I decided I would attack its back and hope for some maiming hits, though Super Brain’s titanium construction made me wonder I could break it.
The fight started and Dr. Super Brain…didn’t. A bad battery had failed, so Super Brain got counted out. Coercion won its second match of the event by being able to move at the start of the fight. Who says a good robot doesn’t need luck!? In my case, my luck helped me to 4-0 and the promise of third place.
With third place locked up, the competition started getting even fiercer. Coercion’s next fight was against Mondo Bizarro, a Weta kit that I was sure would provide an awesome match. It did, though the awesome match turned out to be Coercion’s first loss of the competition on a close judges’ decision. The reason for the loss? Coercion’s weapon stopped turning. It didn’t stop because the belt got clipped but because one of the pins attaching Coercion’s weapon motor to its speed controller got so hot that it unsoldered itself. Whoops. After doing a number on my pulley, the fight ended, for a little while, anyway.
Now in the losers’ bracket (technically my first trip there during the entire competition–Cannon’s first loss was in the finals and lolcat competed in a round robin), Coercion had to take on Grande Tambor. In another unbelievably lucky break, Grande Tambor was more Grande than Tambor: its drum wasn’t functioning. I was fighting a pushybot that had a big hunk of aluminum on its front. In another weapon controller-meltingly long battle (the reason for the shutdown in the middle), Coercion got enough hits to pick up a judges’ decision. It was on to the finals again!
When I opened up Coercion to charge its battery, a frightening surprise awaited me: the weapon controller had gotten so hot that the capacitors attached to it had melted off. I didn’t want to use one of the cheap, old, Chinese spares I had brought (the connectors were not the right size and I figured if the 40A E-Flite had died, the spares stood no chance), so Sean loaned me a 60A ESC. I didn’t realize it at the time, but it required a 3S battery. I had to jam in a 3S battery along with the bigger controller: it was a recipe for disaster. In fact, it caused disaster: on the first big hit of the match, Mondo Bizarro removed one of Coercion’s wheels and the weapon refused to spin up. After a little more prodding, the weapon motor started spewing smoke. Fearing for my LiPoly, Sean’s controller, and my robot, I tapped out after a very short match. I was disappointed again, but I had gone 5-2 with Coercion and picked up my third silver medal of the competition. Things could have been far worse.
Motorama 2013, my tenth trip to the Farm Show Complex, showcased how far I have come as a robot builder. My first robots were fashioned out of cardboard and hot glue; the ones that competed today were painstakingly CADded and CNC-machined. I bleed a little more when I build robots today than I used to, I sometimes get sweaty, but I do cry less (there’s no crying in robot fighting!). My three silver medals were the best result I have ever had at a robot competition. My robots’ combined record was 12-5, which is probably a new record for me for single wins at a competition and winning percentage. To be honest, I don’t mind not winning that much, although it would have been nice. What is really important was the journey: I learned a huge wealth of information about my robots’ strengths and flaws.
The best part about all this is that in robotic combat, there is really never anywhere to go but up. I have what seems like a tremendously good design in Cannon, lolcat remained reliable, and Coercion has finally become somewhat destructive. I was incredibly lucky this year at Motorama–lucky in the sense that I got some favorable draws and unorthodox wins as well as in the sense that I was able to compete at all. My uncle, Mike Filion, proved himself to be a valuable member of Team Slammers: I look forward to his help in future events.
This event report wouldn’t be complete without a heartfelt thank-you to my parents for supporting me through over ten years of very costly, highly emotional robotic endeavors. They introduced me to technology. They helped me find my passion in engineering and computers. They’re the reason why I do well in school. They’re the reason why I adore math and science. They’re the reason I’m the way I am, and I am ineffably grateful for how they’ve molded me. Without their amazing guidance and the lessons they have taught me, there would be no Cannon; there would be no lolcat; there would be no Coercion; there would be no Sharpened.
This concludes my 2659-word monstrosity of an event report. I probably won’t compete again until Bot Blast this summer, but I will post about my design changes as they’re made. I’ll also write more about programming again–I’m working on an independent study project in which I am creating an iPad app. Fun stuff!
In brief, Coercion wound up beating Dr. Super Brain (its battery died), then fighting and losing to Mondo Bizarro in a close judges’ decision. Its next match was against Grande Tambor, which it beat thanks to Grande Tambor’s drum not functioning properly. In the finals, it fought Mondo Bizarro again, but its blade never got to speed; the weapon motor smoked, I lost a wheel, and I finally tapped out. Second place isn’t bad at all!
I will put up a full event report when I get the chance–I’ll most likely write it this weekend.
I would like to thank NERC for all the hard work to making Moto 2013 as great as it was! I would also like to thank my parents for their continued support and my uncle, Mike Filion, for coming along as my pit crew. It wouldn’t have been possible without you!
I will post more once I get some sleep: those concrete floors and six-plus hours of robot fighting really take it out of you! That said, I am pleased as punch. Lolcat went 3-1 and took second place (it beat my friend Sean McKeown’s fairyweight, a disabled Keres, and Toni Fowlie’s fairyweight box and lost to the eventual winner). Cannon also took second, going 4-2 (it beat Toni’s ant box, Swamp Woman 2, Low Blow, and Algos then lost to Low Blow twice in the finals).
Both robots performed well, but both are in such a state that they should probably be rebuilt. It was worth all the effort I put into building them, though.
Here is a fight:
Note that we have several official videographers this year: I’ll be able to link all my fights to the full event report. Also note that my hotel Internet is terrible, so I will post these incremental reports when I get the chance.
As I did before Bot Blast, I am going to provide you with a quick summary of what’s new at Motorama and what you should expect once the results are in next Sunday.
The fleet I’m bringing to Motorama 2013.
First, a quick note: my dad will not be going to Motorama this year. He has been ill. Instead, my uncle, Mike Filion, will accompany me. He will take over as my interim pit crew, engineering assistant, and copilot. He is an engineer with the Navy–I’m sure he will be an invaluable resource as I compete against almost 100 other robots. Actually, the competition is against Murphy.
Cannon is now complete.
It was not complete before.
It can fight.
It could not fight before.
Cannon was awesome in testing. I am concerned about the ball bearings digging into the UHMW side rails on big hits, but other than that and the exposed wheels, Cannon doesn’t seem to have any problems. I expect at least three wins against a very strong antweight field. A lucky draw of fights will yield far more wins than that. Let’s just hope Cannon avoids the undercutters.
Upgraded motors from 50:1 Sanyos to 30:1 MP Polulu gearmotors. This provides more speed.
Software changes to increase drive speed.
Battery recharged from Bot Blast.
Lolcat seems like it could do well, as it always runs the risk of doing. However, just about every fairyweight that is registered for Motorama is a horizontal spinner, and historically, lolcat has had heinously bad reception at Moto. If the radio works alright, lolcat ought to get a few wins and may even place. Without radio reception, the kitty won’t be getting its cheezburger anytime soon.
New, 11oz-ish, hardened S7 tool steel blade. This blade won’t bend, is lighter, and has a very high MOI.
Changed weapon gear reduction from 3:2 to 2:1. The blade spins up faster and running the weapon does not make the weapon motor as hot as it used to.
New, higher KV weapon motor. This motor spins faster and harder than the old one. It is rated at about 400W peak, as opposed to the old, 200W peak motor.
The weapon should now spin at about 6,000RPM, which is slightly faster than the theoretical maximum speed at Bot Blast. However, this blade gets up to speed much faster and seems to hit very hard.
1/8″, custom-bent UHMW wheel guards that won’t shatter have replaced the old wheel guards. The first set, which shattered, was made of ABS. The second, smaller set, which shattered, was made of Lexan. These are thicker and tougher.
The beetles at Motorama look awesome. I don’t mean that lightly. I am very scared of what Coercion will be up against. That said, Coercion has a ton of reach and will hit extremely hard–at least on the first few hits. I would be upset if Coercion gets less than two wins at Motorama. As always, a top-three finish is possible, but highly unlikely.
As the saying goes, months to build, minutes to break. I hope the breaking is at a minimum this year. I will post nightly updates while I am in Harrisburg.
I’ve run into quite a few problems with Cannon since I last posted, but I have also made a lot of progress. I’ll get you up-to-date:
Cannon’s beater (along with Coercion’s new blade) arrived
I realized that Cannon was about an ounce overweight. It had to go on a serious crash-diet.
The weapon shaft material has been changed from S7 to titanium. I ordered some Ti, cut it, and tried to thread it. Unfortunately, I had a rethreading die instead of a threading die: although it worked with unhardened S7, grade 5 Ti was a different story. I managed to make enough threads to put on lock nuts, and a good die will be arriving soon.
I reduced the weapon reduction from 3:2 to 1:1 by making a new weapon pulley.
I wired everything up.
I made some pockets in the back to reduce weight.
Cannon spun up.
All the weight-saving measures have brought Cannon down to weight without forcing me to resort to using the notoriously brittle FingerTech Lite Hubs instead of the good Dave’s Aluminum Hubs I had planned on using. I will have everything put together by the end of the weekend; I will only have to make a few spare parts and thread the ends of the weapon shaft a little more before Motorama (I only have one weekend left!). My next priority will be Coercion, which ought to be manageable enough.
Here’s a video of Cannon spinning up:
This thing is going to be a lot of fun at Motorama! I have always wanted an antweight beater ‘bot.
I’ll admit it — I am way behind of where I normally am robot-wise at this time of year. At this time last year, I was spending the better part of my weekends toiling over the mill trying to get Coercion done and troubleshooted. This year, much of the time I would have spent building robots has been dedicated to visiting my dad in the hospital over an hour away, as he has been very sick. Still, Motorama is about a month away and it will not wait for me. It’s time to get some robots built.
I have already designed Cannon and Coercion’s new blade (with some slight changes from the original post). Cannon’s blade and Coercion’s blade will be fabricated by Team Whyachi, since I am not overwhelmingly comfortable machining neither titanium nor S7. I don’t consider our mill’s CNC reliable enough to machine a hundred dollars worth of material at once. Besides, the S7 blade needs to be heat-treated to avoid another Bot Blast debacle (the blade bending 30 degrees).
Here’s what will need to happen over the course of the next month:
I will need to receive Coercion’s blade and Cannon’s beater from TW.
I will need to CNC mill Cannon’s body.
I will need to create some blade hubs on the lathe.
I will need to fashion and harden an S7 weapon shaft for Cannon.
Lots of testing.
Ordering a few new parts.
Overall, it should be manageable. There are a few three-day weekends coming up that I can completely dedicate to “botting it,” and there is still a month until Motorama. The race is on. Let’s hope it ends in a trophy…
The good news is that I converted all my SLDPRT drawings for Cannon’s sides into DXFs, then created GCode from the DXFs today.
I use GMail to transfer the files between my dad’s PC (which has the GCode generation software) and the mill-driving PC. I use Mach3 to drive the CNC.
Continuing my alliterating-c tradition of robot names is Cannon, an antweight version of Lolcat. On paper (and in CAD), Cannon looks like it’s going to be a lot of fun.
Very rough, yes, but it still lets me visualize everything and make sure the parts fit.
Here are the specs I have planned out:
Weapon motor: Turnigy Aerodrive SK3 2826-1240. It is rated at 150W and will provide more than enough weapon power. The old “Beloved Shardy” undercutter I built simply did not have a powerful enough weapon motor, and this one will be sure to suffice!
Weapon ESC: Thunderbird-18. It’s tried-and-true, and the weapon motor is rated at 16A continuous so a fire seems unlikely right now. Unlikely.
Battery: Turnigy Nano-tech 3S 460mAh LiPoly. I love the idea of three cells, and in theory, a 460mAh can supply about 14 amps for an entire two-minute fight (throwing out any drops/inefficiencies). I think I will have bigger problems than the battery if the robot requires 14A continuous for two minutes!
Drive ESCs: Fingertech tinyESC v2.1, the same kind used in Lolcat. I can’t say I’m wild about these controllers; I killed five or six of them before I learned that I’d discovered a hardware issue. They now seem to work okay, and I do have to say that Fingertech customer service is phenomenal!
Weapon: 3.0ish ounce 2.5-inch diameter titanium eggbeater spinning at about 9200rpm. It will be supported by ball bearings and connected to the weapon motor by a urethane belt with a gear ratio of 3:2. The weapon shaft will be hardened S7.
I already ordered some of the parts, and I was actually very impressed by how much higher-quality everything appears. Just look at the packaging.
Look at those beautiful graphics. It’s almost worth the huge premium over normal Turnigy products for the SK3…
Actually, just look at the motor and battery!
These motors are actually a little bigger than I expected but feel very solidly built.
Speaking of big, these batteries are HUGE for their capacity. Maybe I’m just used to dealing with Lolcat parts.
I do have some small quips with these parts.
Both the battery and motor are enormous. It’s a good thing I have minuscule drive ESCs because I may have a hard time getting everything to fit, and the body I designed for Cannon is fairly large.
The brushless magnets don’t feel very strong, though the motors feel very precise when you turn them. My feeling is that I am mistaken and when I actually wire the motor up, I’ll be in for a pleasant surprise.
The motor wires are small and flimsy.
The battery came with a JST connector on it. The battery is rated for 25C (11.5A) continuous, 40C (18.4A) burst. JST connectors are rated for 5A. That’s a waste of plastic.
Still, despite my minor complaints, I am happy with my purchase so far. I can’t wait to see that motor spin.
The motor isn’t the only part of Cannon I am excited about. I learned a lot about building eggbeaters well with Lolcat, and I believe most of it will apply in the antweight class as well. For one, protecting your belt is very important. Lolcat’s belt almost got sliced twice at Bot Blast, so I’ll try to get the side rails to cover up the pully. However, the bottom of the side rails is far more important. Tracked Terror kept getting underneath Lolcat and flipping it over. I worry that wedges could do the same with Cannon, but I have devised a fix of sorts.
Side view of the above image.
Notice that the sides are swept back. The beater extends way forward of the front of the supports. I am concerned about what effect this will have on stability. Since the beater, likely the heaviest individual part of the robot, will be centered in front of the support, the entire robot will act even more front-heavy. It could lead to some flipping over on hits; only time will tell. I am also concerned by how small the bottoms of the supports are, but they will be 3/8″-thick UHMW so antweight weapons shouldn’t be able to completely wreck them.
The only way we’ll see how this plays out is in the arena. I will continue to post progress updates on this blog as Cannon comes together.
Coercion’s blade needs a lot of work – I think the video of Ripto bending it 30 or so degrees proved that. The question is how to change it. I know Coercion is a good bot, but I have noticed some continual flaws. First of all, the blade is too heavy. It spins up too slowly and it takes way too much work to get up to speed (thanks to losses all over the place), so the weapon motor runs hot and pulls something in the 30A neighborhood. I thought I had more or less fixed the problem before Bot Blast, but running my robot on 7.4V made it far more sluggish than I anticipated and I still wasn’t getting ideal blade performance. The blade is also so heavy that it tends to flip over its nose, which provided a loss at Boy Blast. I have decided to apply some physics to make Coercion more hard-hitting and hopefully more efficient than ever.
Where omega (henceforth referred to as w) is angular velocity, E is kinetic energy, and I is moment of inertia.
Awesome, so based on that, we can do one of two things to increase the kinetic energy of the weapon:
Increase the angular velocity (how fast the weapon is spinning). This will be the more effective of the two methods because it is a squared term, so if we double the angular velocity, we quadruple the kinetic energy.
Increase the moment of inertia. MOI is the sum of the masses of the particles that make up an object multiplied by the radii from the center of rotation squared. In other words, the heavier something is, the greater its MOI, and the greater something’s diameter is, the greater its MOI.
So there we have it. To make Coercion’s blade work better, we make it heavier and spin it faster. Great physics lesson, Einstein. The problem here is that to make weight for better wheel guards, a better weapon motor, new batteries and the other improvements I have planned for Coercion, I need to make the blade lighter. Remember that MOI is also based on the distance the particles of an object are from its center of rotation. Thus, if I can concentrate the mass as far away from the center as possible, I can “cheat” (not really) a little bit: the blade will hit harder while not weighing in any more.
My target weight of the blade was 11ish ounces, which is about a big reduction over the old blade. I had to make the inside as skinny as possible while making the outside part as wide as possible. I kept the same blade dimensions – 11.75″x1.50″x0.19″ – and I plan to have this blade waterjetted out of S7 and then hardened (I learned my lesson at Bot Blast!).
10.35oz, far lighter than the old, nearly-one-pound blade.
The plan is to spin this blade at 10,000rpm with a 3S LiPoly and a new weapon motor in the 1500-1900kv range (and a new, 2:1 weapon gear ratio). If I recall correctly, Coercion’s blade was spinning at about 7000rpm at Bot Blast, and according to the MOI differences I saw in Solidworks (the new one has about a 22% lower MOI than the old one), the new blade will actually store about 50% more energy. Not bad for saving three or four ounces, huh?
Having not competed since Motorama (and not competed in a Mall for five or so years), I was very excited to fight robots at the Columbia Mall in Bloomsburg, PA. We woke up around 7:30, had a terrible breakfast (why would you serve one egg by itself on a plate with an orange?) at Cracker Barrel, and were at the venue by 9:00ish. I was pleased to see that Bot Blast has a wooden floor because it would not interfere with Lolcat’s radio reception. Wooden floors are also a bit quieter and more forgiving.
This event report contains some fight videos, but only for the interesting ones. I have only included one Lolcat vs Tracked Terror fight and did not include any Amatol fights.
With the guys.
We got through safety inspections without much of a hitch. Coercion was a tiny bit overweight (as was Amatol) but apparently the scale was off by a bit so I didn’t have any issues. We sat around and waited for the event to start. Fights kicked off around noon, which is way earlier than they would at Motorama. We were all impressed.
The first fight of the day for us was with Coercion against Kyle’s fearsome vertical spinner, Ripto. I knew it would be a tough match for Coercion (especially in an eight-foot arena like the one at Bot Blast) but I never imagined it would be as tough as it was. We both spun up and Coercion went flying into the ceiling. The S7 blade (which I did not have hardened for some unthinkable reason) was bent about 30 degrees upward. I tried to push Ripto, hoping that the belt would come off the weapon, but it was no use. I quickly tapped out.
I do not have any images of the bent blade because I was so concerned about getting it fixed. I can tell you that it took some vice smooshing and beating with a hammer to get it back into shape. I did, however, get Coercion fixed.
The next first-round match was between Amatol and another wedge bot. After about thirty seconds of pushing, Amatol ended up stuck on the wall and was counted out. Amatol’s wedge wasn’t getting it done and I lost because of it. The next version will need a bent back. 0-2!
At this point, I was running seriously low on robo-mojo. It was Lolcat’s turn to fight a small undercutter called Baby Box. Undercutters have always scared me with Lolcat ever since Jeremy Campbell’s Rebound broke the eggbeater twice at Motorama 2011. I was hoping that it would not be able to cut my belt or worse, rip the eggbeater out of its supports. After accidentally hitting the blade a few times, I felt like my robot would hold up. I eventually removed the other robot’s weapon. Unfortunately, I did not remove either of Baby Box’s wheels (there seemed to be some foam padding helping there) and I was unable to cut Baby Box’s exposed battery connector. But still, I won the match on a judges’ decision.
With some of my mojo restored, I set my sights on my next antweight opponent, Mateo. I had to postpone my match because of connector issues (which would come back to haunt me), but when we finally got in the arena, the match was boring. We pushed each other around and Mateo wound up stuck on the arena, and after being left on the wall twice, I decided not to risk freeing it. I felt horrible but won by knockout.
With two wins under my belt, I started to calm down a little bit. I had been seriously worried at the beginning of the event, but I chalk it up to a combination of bad luck, poor foresight and great opponents. My next fight was another with Lolcat. This time, it was against Hedgehog, which was the fairyweight I thought had the best chance of breaking Lolcat coming into the event.
The fight began and we both spun up. Hedgehog tried to attack my wheels as I moved to attack its wheels, so our weapons ended up making contact. After seeing that my beater could stand up to Hedgehog’s large, direct-driven blade, I became a little more aggressive. My strategy worked – one hit sent Hedgehog a good foot or so into the air and the next sent us both flying. The second hit broke Hedgehog’s weapon motor in two and Lolcat won by tapout.
The damage to Lolcat from this fight was actually a lot worse than it appeared. Lolcat’s weapon shaft was a little bit tweaked, the pulley had a big gash taken out of it, the right weapon bearing’s dust covers were broken off, and alarmingly, the weapon belt was nearly sliced in two! I made a new belt but chose to keep the shaft as it was since it did not appear to impact weapon performance. A quick spin up test confirmed that, and Lolcat was ready to go once again.
My next opponent was a beetleweight vertical spinner called Lezlee. Considering my blade had just been re-straightened, I was happy to just be fighting. I noticed that Lezlee had thin aluminum armor, and since Coercion appeared to be on its last legs at the time, I decided to just go all-out. I spun up and chaos ensued. I chewed away at the front of Lezlee (somehow while avoiding the blade), and one hard hit jarred its LiPoly free. Jeremy is smart enough to know a one-pound piece of spinning steel could do bad things to an explosive battery, so he called the match. Coercion won by knockout.
The next fight was Amatol vs Kyle’s Cutter, an antweight spinner. I was confident heading into the fight because Amatol was built to fight spinners, not wedges, so I was looking forward to testing my robot’s strength. Unfortunately, I box rushed Kyle’s Cutter, hit the wall, and one of the battery connections in the speed controller came loose. Amatol was dead in the water and I tapped out less than three seconds into the match. I thought some very non-PG words after that fight.
With Amatol out after two stupid, preventable losses (AGAIN!), it was Coercion’s turn to continue carrying the Team Slammers banner. It was matched up against Play ‘n Krazy, which was fighting as a lifter at Bot Blast but is usually a vertical spinner. I was looking for revenge for my three-second match, and I got it in the form of a nine-second one. Coercion spun up and delivered a hard hit to the front of Play ‘n Krazy. The hit removed a wedge panel, a wheel, a wheel guard and a receiver and Play ‘n Krazy tapped out.
Lolcat was up next in the fairyweight winners’ bracket semifinal against The Tracked Terror. This was the first of three straight matches between these two robots. The Tracked Terror beat Lolcat at Motorama, so I was out for revenge. We traded blows for two minutes but Lolcat won on judges’ decision. More on these matches later.
The next fight for us was Coercion vs Counter Shock. Counter Shock was a very well-built beetleweight drumbot, but the drum wasn’t working so all I had to do to win was to keep the weapon running and not get stuck on the wall. I only accomplished the weapon part. I spun up and hit Counter Shock hard, but unfortunately, the hit also flipped Coercion over. It was too tall to hit Counter Shock, and got pushed up against the wall. Counter Shock gave Coercion one final shove, and the wheels could not get traction. Coercion was counted out, leaving Lolcat as our only robot still in the tournament.
Despite being out, Coercion still had one trick left up its sleeve – the beetleweight rumble. Although it ran out of battery at the end, it was crowned co-champion of the rumble along with mantisweight Dead Metal (since there was no mantis rumble). I think it had something to do with the flying around everywhere thing (see the video) combined with my exuberant cheering at the end of the match.
Lolcat was in up next against The Tracked Terror in the first fairyweight final. This match did not go as well for Lolcat as the semifinal did. I kept getting flipped over and according to Jeremy, lost on aggression. The good hits were also 3-2 in favor of Tracked Terror. I was worried – I was very close to finally getting a win with Lolcat, but it was going to come down to an all-or-nothing final. I charged my batteries and decided that no matter what, I would keep chasing Tracked Terror. Lolcat uses 50:1 gearmotors instead of the 30:1 ones used by Tracked Terror, so it was at a major speed disadvantage.
Nearly two years of work came down to one final match. I wanted to win really badly. I stayed aggressive. I followed the game plan. Luckily for me, it all worked out. Lolcat won on a judges’ decision and was crowned fairyweight champion. Congratulations to Chris on building an awesome robot! Lolcat could barely scratch it.
So, with the event over, what did I take away?
Lolcat is too slow and 30:1 HP Pololu gearmotors instead of 50:1 Sanyo gearmotors would do it a lot of good.
Coercion’s blade is too heavy and needs to be hardened. At Motorama, I plan on using an 11-12oz blade spinning at closer to 10,000 RPM. I will keep the MOI as high as I can while designing it.
Amatol needs… improvements. It is very strong but keeps failing in dumb ways. I will make some adjustments to keep it from getting stuck on the wall and hopefully the robot lords will smile upon me at Motorama.
Due to SATs, we won’t be able to make it to Franklin Institute this year. Any changes we make won’t be tested for a very long time!
Another big thanks goes out to Jeremy Campbell for putting on a great show. We will definitely be back next year!
John Parsons' Blog About Robotics, Programming and the Search of Knowledge