Our 250lb combat robots Blacksmith and Minotaur are competitors on ABC's Battlebots. On Sunday, the nailbiting video of our fight made it to the frontpage of reddit. AUA about what it takes to build and drive combat robots.

Al Kindle, captain of Team Half Fast Astronaut:

We have been competing in combat robotics for 20 years. I am an Electro-Mechanical Technician at Spex Sampleprep. Blacksmith is based on hammer bot designs we have competed with in the 30lb class. This was our first Heavyweight bot, as became evident when the hammer head decided it wanted off the team...

Marco, captain of RioBotz:

Ph.D from MIT, professor of Mechanical Engineering at the PUC-Rio university in Rio de Janeiro, Brazil. Head of the RioBotz team since its creation in 2003, building combat robots in all weight categories. RioBotz has won more than 50 medals and 50 trophies in international and Brazilian competitions, but never competed at BattleBots. RioBotz stands for Rio de Janeiro battlebots, this shows how much we've dreamed about this moment since 2003.

Proof: http://imgur.com/vZRCVqd

P.S. BattleBots will not be airing this week, due to a presidential townhall. Tune in next week on ABC - Thursday, 7/21 at 8/7c.

Thank you all, this was a wonderful AMA!

Comments: 273 • Responses: 40  • Date: 

mole5537 karma

How much kinetic energy does Minotaur have in it's drum?

MinotaurRiobotz64 karma

The drum has 73lb, with a radius of up to 3.4 inches, and a very thick wall of up to about 1.5 inches. And it spins at about 10,000RPM (12,000RPM is theoretical). I had to get the moment of inertia from the CAD file, it turns out that at full speed the weapon has about 55kJ of energy.

lewisb4222 karma

(for Marco) Being from the US, I've been curious what the response in Brazil has been now that they have a team on BattleBots. Are the local channels carrying the show and if so, how are the ratings?

MinotaurRiobotz42 karma

Things are crazy here! A lot of the views from the viral video came from Brazil. Several mainstream Brazilian internet pages featured the news about us on their cover. Our facebook account had about 1,000 likes a day. Our robotic community here knew we were competing there, but after the viral video it seems like everyone knows!

hofstaders_law18 karma

Hi Blacksmith! How is the hammer attached to the shaft? What broke when it came off? How will you be making it stronger for next season?

Hi Minotaur! How do you handle the shock load of landing a big hit with that drum spinner?

MinotaurRiobotz29 karma

We use multiple roller bearing to take the hits, they are all located inside the drum. We do not want to dampen the hit, otherwise it would not be effective, so all the force path from the drum tooth to the ground is very rigid. All our internal components need to be shock mounted, otherwise they break apart only from their inertia!

teamtiki16 karma

Daniel / Marco: who was the tougher match, Blacksmith? or Super Fluffy Pink Bunny From The Land Of Candy and RainBows?

Al: um.... Metal! \m/

Great Job to both of you in that match. Tough bots and they put on a great show!

MinotaurRiobotz14 karma

Both are very tough bots and survived a lot of punishment for a long time. But I would say Blacksmith, because it not only survived but also had a working active weapon almost the entire match.

HardcoreRay12 karma

Great showing from both of you! Hopefully we get the chance to do it all again next year!

Marco - how has the viral response to the video been in Brazil? Just wondering if we have a ton more international viewers now :)

Al - Any changes for the hammer drive for next time? You had a good amount of power in it, but it seemed rather thermally inefficient - you know with all the fire and stuff.

MinotaurRiobotz14 karma

The viral response was extremely high here. Most of our new page likes were from Brazil, even though we had likes from all over the world. India and the US come right after (we have a huge fan base in India!). We've had international visibility since we started competing in the US in 2006, but now it is much higher.

Matthew08411 karma

What type of motors and gearboxes does Minotaur use for the weapon and drive system?

MinotaurRiobotz10 karma

The drive system uses custom-made 12:1 gearboxes, attached to long Ampflow motors, which are very reliable. The weapon system uses two large Scorpion brushless motors, their largest model, with a total of 4 V-belts to power the drum. Using two weapon motors gives us a lot of power and also redundancy in case one fails.

DasQBert10 karma

Hey y'all! My question is for both Al and Marco: How long did it take y'all to create the machines from start to finish and where did the inspiration for them come from?

MinotaurRiobotz22 karma

We have been building drum-style robots since 2006. Before that we had 2 horizontal spinners and 2 "overhead thwackbots". I fell in love with drums because they can make the robot so compact, they can self-right, and they can not only cause damage but launch the opponent. Minotaur's design started in 2009 with our heavyweight (220lb) Touro Maximus, and it has evolved ever since. For BattleBots, we had very little time to create an entire robot, so we decided to improve the design of our 220lb bot. We tried to make its structure round like our other Touros, but it became too heavy in the CAD designs. We used the extra 30lb to redesign and reinforce parts of the structure. We've worked from about January until late April, I guess this was the window of most new robots from season 2. Minotaur was entirely built from scratch, but with a design that has been refined by us over the years.

HallwayHomicide9 karma

To Team Riobotz: With their bot (Poison Arrow) being so similar to yours, how much interaction have you had with CaustiCreations? Also, I know you have a higher spin speed and drum weight than them. How does your MOI compare to theirs? How is the weight distributed within your drum?

MinotaurRiobotz11 karma

We try to have our weapons with about 1/3 of the weight of the robot. This is a lot. Minotaur has a 73lb drum and 250lb, not quite 1/3, but still very deadly. We know the builders from Poison Arrow, they have built a very strong lightweight (60lb) combat robot, so we respect them a lot. When it comes to weapon-to-weapon hits between drums or vertical spinners, the tip speed is very important. I don't know their MOI to compare, but Minotaur's is very high. And we can go to 10,000RPM if needed, this is not a usual speed for a heavyweight.

Sgt_Cutlass9 karma

Question for each of the teams Minotaur: Minotaur seems smaller than the other robots, what are the dimensions of it? And what differences are there between it and Touro Maximus? Blacksmith: What exactly blew up at the end? Also where did the idea for a flame throwing hammer come from?

MinotaurRiobotz11 karma

Minotaur is roughly 2 feet by 2 feet, and 8 inches high. Pretty small for a 250lb bot. Touro Maximus' chassis was machined from 4.5"-thick aluminum plates, which required attaching skids and wedgelet mounts using pins and screws, weak points. Minotaur was CNC-machined from 8"-thick plates, which allowed us to make each side wall as a single piece. The wedgelets and attachments are mounted differently. The drum is heavier, 73lb instead of 65lb. The single-tooth single-piece self-balanced profile of the new drum was calculated and optimized using genetic algorithms (GA), to maximize the "bite" on the opponent while guaranteeing a perfect balancing. We had used GA before in a discrete version to generate an optimized polygonal drum profile, we called it the Snail drum, which Touro Maximus had used. This time we combined a continuous GA approach with other structural shape optimization techniques to get a smooth curved profile. In addition, Minotaur has thicker aluminum top and bottom covers, with titanium and tempered steel reinforcements against arena saws and... hammers!

smegmaless8 karma

My 4 year old loves you guys. So do my wife, my other son, and I. I don't have a question, I just want to tell you that We find you guys, that do this stuff, fascinating. It's a pleasure to watch you and that show. It's even more of a pleasure to watch my 4 year old go funking bonkers when there is a good battle. Good luck in your next battle.

How log have you been doing this?

MinotaurRiobotz3 karma

I have been competing since 2003. We started at the Brazilian nationals of that year, there were only middleweights (120lb category). Since then we have built combat robots in all weight classes.

smegmaless7 karma

Do you have any advice for people that want to play around with robotics, but don't necessarily want to become competitors? For instance, what if I wanted to build a little battle bot with my son, where would we start?

MinotaurRiobotz18 karma

I would start with robotics kits, there are plenty around. Most of them require very little mechanical background. If you want to go further and build combat robots, the RioBotz tutorial is a good place to start. It has a hard copy at cost price (non-profit), but it is also free at the RioBotz website. It teaches all aspects of building combat robots.

drakhaien7 karma

Any chance you guys could build a big warbot to also challenge the American MegaBot or Japan's Kuratas Mecha?

That is, if they would accept to fight a non-seated bot (I support both robot and mecha developments)

MinotaurRiobotz5 karma

This is an awesome initiative, the ultimate combat robot. Some RioBotz veterans are considering following this path. Having wife and 2 kids and a steady professor job, for me it would be tougher to leave Brazil to work on them abroad, it requires full dedication. And building them entirely in Brazil would be an economic challenge. But I would definitely love to interact, directly or indirectly.

millenialsarestupid6 karma


MinotaurRiobotz5 karma

Get inexpensive robotics kits, they will give some beginner skills on mechanical assembly, motors, batteries. Once you have some practice, you will be able to build your own robots from inexpensive parts. Attending events is also a great way to learn. Kids usually fall in love with it after attending their first competition, even if just to watch.

alwaysbechomping6 karma

What a match - congratulations to both of you and your teams!

For both Al and Marco - what are some engineering/design/fabrication aspects of your bots that you're proud of, but that have been glossed over in the making of the show? Particular mechanisms you think are awesome, or systems that took a lot of tinkering to get just right?

For Marco - do you send your drum out to get balanced? If so, where, and what is that like in terms of cost, turnaround time, how surprised the shop is by your request, etc.?

MinotaurRiobotz10 karma

We are proud of making very small and compact robots, and with very few parts. This makes them easy to maintain between matches, and increases the strength of the structure, without weak links. Many people think that small is worse, but it can be better, more maneuverable, stronger. The drum is self-balanced by design, so when it comes from the CNC machine there is little work to do on it. But between matches some chunks of metal can be removed from the drum, and we then balance it manually. We slightly turn the drum by hand, without any belts on, and see if it tends to stop spinning at the same position. We then remove a little bit of material from that heavier section using a grinder and repeat. It is a painful process, but we have a lot of experience with it and it works great. Several shops in Brazil are already used to RioBotz and our crazy parts!

redmoon35806 karma

What sets Minotaur apart from other drum bots? What would you say is the most interesting or nuanced part of it's design?

MinotaurRiobotz14 karma

Minotaur can combine being offensive and defensive. Since it is very compact but with the same weight as its opponents, its structure can have very thick walls. It also has a lot of kinetic energy in its weapon. So much that it can be difficult to drive due to the gyroscopic effect. When we need to go for the knockout, we spin it up. But what I like the most about it is how easily it can self-right with the gyro effect (and dance as well).

kurisu78855 karma

Besides the fight we saw you in what is the worst amount of damage either of you has had to repair?

MinotaurRiobotz9 karma

Perhaps the middleweight match Touro vs The Mortician, in 2006. We won that match, but it was a Pyrrhic victory. That was the very first version of Touro, and back then we used too many small screws on our structure, and a huge number of them sheared. It took us seven intense hours to get Touro ready again. Since then, we have been using fewer but much larger screws in our designs, and countersunk whenever possible.

johnnycruise8995 karma

Hello Al and Marco! As everyone else has been saying, great work on your robots!

What kind of strategies have each of you used in designing for repairability and multiple matches (other than having lots of spare parts)? I have heard that over time Tombstone and Bronco each have their frames skew and warp due to the loads involved in their weapons impacting opponents/firing pneumatics

MinotaurRiobotz5 karma

Besides having spare parts, we use very few parts in our structure, so it is relatively quick to maintain. Assuming the gearboxes (or spares) are assembled and the electronics is already soldered, we can assemble the entire robot from scratch in about 40 minutes, ready to enter the arena. This is very important in competitions where you have about that time to service the robot between matches. We have spares for our side and back walls, so if they get seriously bent it is a matter of replacing them. The advantage of using screws over welds is you can change spare parts more easily. But on the other hand welded robots can be very strong.

celo7535 karma

Hey! Thanks for doing this AMA! As a Brazilian, I'm loving to see my country kick robot ass on TV!

To Marco: I'm very interested in the use of a genetic algorithm to determine the shape of the tooth. What made you think that that would be the best choice, rather than a more conventional design? I thought genetic algorithms weren't advanced enough yet to generate better results than what you could achieve with a "normal" tooth? Also, qual sua cachaça favorita?

To Al: Have you ever though about using a more focused torch on Blacksmith, like Complete Control's flame? Blacksmith's fire looked like it was mostly for scoring points with the judges, I wonder if you could get an enemy pinned, it would actually be effective.

MinotaurRiobotz4 karma

We have used not only genetic algorithms, but also other more traditional structural optimization techniques. Both can give good results. Our objective is to penalize any unbalancing, and to maximize the "bite" the drum has on the opponent. The RioBotz tutorial has an entire section devoted to the issue of tooth design and tooth bite, but we don't go deep enough there to enter the more advanced part using GA. BTW, cachaça Germana is a good one!

personizzle4 karma

For Marco:

-Your team is far and away the most successful university-driven team I know of in combat robotics. Here in the states, the viewpoint towards the sport from academia is often outright hostile. Any tips on developing a culture which appreciates and supports these kinds of programs?

-Any chance of us seeing a detailed build report for Minotaur or Touro Maximus along the lines of those for Touro and others in the Riobotz combat tutorial? The resources you've already made available have been tremendously helpful, but it would be amazing to be able to study and learn from the design of what's the gold standard for the Heavyweight class, and all the new technologies such as brushless weaponry they feature.

-Why did you move away from the "snail drum" towards a symmetrical design for Minotaur?

For Al:

-I was pleasantly surprised at how "low tech" a lot of Blacksmith's construction is, in an era of the sport where monumental CNC machined builds like Minotaur and others seem almost a requirement to get anywhere. Any tips on maintaining a competitive edge while sticking to welded box frames and other techniques that seem to be going by the wayside?

-Blacksmith was incredibly well driven! How much time did you have to practice with the bot, and what kinds of trials did you put it through to prepare for Battlebots.

For both:

-What kinds of improvements are you planning for next year?

MinotaurRiobotz8 karma

Thanks! We had a hard time convincing sponsors to support us in the beginning, and a lot of people had prejudice because we were developing a destructive machine in a violent sport. You must keep trying to get support no matter what other people say. Eventually they will see that you are preparing these students to build much more robust robots for the industry, and they eventually change their opinion. But it is a tough job to show people that robot combat is all about construction, not destruction. You spend months building and learning. And a 3-minute destruction will make you learn too - and it is fun, attracting students. They have so much fun and adrenaline that they do not notice they are learning. I'm tricking them into studying! I have been wanting to write a new version of the tutorial, including these new build reports, for a long time, but I've been way too busy teaching classes, advising, developing robotic projects, doing research, writing papers, and competing. Too much work. But it is on my to-do list. Anyway, before that happens, I am glad to answer any questions about their designs. The snail drum still is a spare drum for us. But our new optimized designs with genetic algorithms have similar performance, and they can hit on both sides. We do not reverse our drum because it would burn the electronics during the match, we self-right Minotaur, but it is good to have a symmetrical drum so you can flip it over between matches to use a better sharp edge of the other side of the single tooth.

ResettisReplicas4 karma

What's the robot fighting scene like in Brazil? Does anyone outside of Team Riobotz stand a chance?

MinotaurRiobotz16 karma

It is extremely competitive here in Brazil. Brazilians have already swept combat categories in the US. Darwinism has worked so well here, most bots are very well built and very destructive. I'd like to think we helped that, from 2004 to 2009 we had won almost every Brazilian championship in every weight category. Since then, it has been much much tougher to win here. They learned from their losses. And the RioBotz tutorial also helped, it was first released in 2006, and then in English in 2009. Now we have too many strong vertical spinners and also many many wedges. Other Brazilian teams would definitely stand a chance. But the main challenge is building your very first heavyweight, it is a very hard learning process, trickier than middleweights, and very expensive. No other Brazilian teams have built a heavyweight yet. We have been working on our heavyweight drum designs since 2009. This gives an advantage, since you win or lose from the details.

Bigfoot254 karma

How much programming goes into your robots and what language do you use?

MinotaurRiobotz6 karma

Most of the challenge in combat robots is in mechanics/pneumatics/etc and electronics. Since they are radio-controlled, there is not too much programming needed, unless you want to develop your own speed controllers.

secretCajun4 karma

Question for Marco, what sort of electrical components are behind Minotaur?

MinotaurRiobotz6 karma

Our drive system uses one large Roboteq controller, it is very reliable and controllable. The weapon uses MGM brushless speed controllers, they were the only ones that survived our large Scorpion motors with our abusive 1,600 amp currents (total) for a few seconds during spin up. Then the fuse became our batteries, so we switched to MaxAmps in 2015 and we had a killer configuration (literally!). We also use two separate circuits for drive and weapon, each with its own switch.

teamtiki4 karma

Who was your favorite Bot in Season 2? (besides your own) and Why?

MinotaurRiobotz9 karma

That depends on the criterion/feature I would be admiring. But probably Red Devil. It is so beautifully machined, and it has so many details. It follows the opposite path from our designs, with it having too many parts and us as few as possible, but they are so well designed and integrated that the robot is very functional too.

RenAndStimulants4 karma

Minotaur is such a boss bot!

Shoutout to blacksmith for kicking ass too!

My question is, if it was a no holds barred, underground bot fight, what is one lets say, banned or unrestricted, weapon you would add that you think could charge up the destructive power of your bots?

MinotaurRiobotz6 karma

Untethered projectiles and high explosives. But this would be too dangerous. And I think it is more fun to have contact between the robots, projectiles would change the dynamics of the match.

IAmTotallyNotSatan4 karma

I asked this to Al when he had his AMA on /r/battlebots, so this is for you, Marco. Would you rather fight 10 100-pound Tombstones or 1 1000-pound Ray Billings?

MinotaurRiobotz7 karma

Lol. At once? In general I'd rather fight 10 multibots than a single heavy one. But that would depend on 1000-pound-Ray's weapon.

TBone_Filthy_McNasty4 karma

What interesting applications has your work inspired or introduced, or are you in it solely for the sake of battling 'bots?

MinotaurRiobotz8 karma

In my university we have developed several inspection and welding mobile robots for the oil, nuclear and naval industry, both R/C and autonomous. These robots work in harsh environments and cannot fail, much like in robot combat. Many components and shock-proofing techniques we use in these robots we learned from robot combat, either from our mistakes or from knowledge shared in forums and during events.

RevRobots3 karma


Marco, I am a huge fan of your Riobotz Combat Tutorial, how long did it take you to do research etc.?

Al, How did you fit the flamethrower inside the hammer?


Revelation Robotics

MinotaurRiobotz4 karma

Thanks! I started to write it in 2004, to teach the students from the team how to perform basic motor and battery calculations for the drive and weapon systems. I kept expanding it with all info that I didn't want to get lost, as the turnover rate of the team is high with students graduating or getting internships. This would make it easier to teach the new students, they could read a primer before making costly mistakes at the lab. In mid-2006 I published online (for free) the Portuguese version, with 190 pages. I kept adding info to it and translating to English until the much expanded 2009 version was ready.

Lrothnar3 karma

When you guys are working, what are the choice snacks/nourishment?

MinotaurRiobotz4 karma

When we pull all-nighters, energy drinks. Too many of them. And pizza when we don't have time to take a break. But I do not recommend that!

bduddy3 karma

Many people seem to think the rules for Battlebots and other robot competitions are too restrictive. Is there anything you wanted to do but couldn't due to the rules?

MinotaurRiobotz2 karma

I think we can do most anything that can create a spectacular mechanical destruction. The restrictions are mainly with untethered projectiles or invisible damage like interference or electrical shocks. I don't see anything new that would really make a difference.

Never_up_vote3 karma

How did you get into battle bots? More specifically was there a specific moment you thought, hey I am going to build a robot to fight other robots with because it's awesome! And what is the first step you took?

Edit: autocorrect owned me.

MinotaurRiobotz6 karma

A group of six undergraduate students wanted to start a robot combat team in late 2002 at our PUC-Rio university, inspired by BattleBots videos. Since I came back from MIT in 2000, I started teaching robotics at PUC-Rio. So it was a perfect match. I liked very much the idea and advised the students, but not much hands on from me. I only got really hooked after our first competition, in 2003. Right after our loss (we got sixth place), I bought every single book about robot combat, read them all, and started making notes (which later helped me write our tutorial). I shared that knowledge with the students, and became myself a builder, not only a coordinator, working side by side with the students and leading by example. In 2004 we won the Brazilian nationals with our first horizontal bar spinner, Ciclone. I was more than hooked. There was no way back!

RenAndStimulants3 karma

My other question is what are your guys' thoughts on the Japan vs. America giant robot fight that is supposed to go down in the near future?

Article for reference

MinotaurRiobotz4 karma

I really want to see that! This is the ultimate robot combat. Too bad the day only has 24 hours, otherwise I would add that combat category to our portfolio!

InTupacWeTrust1 karma

What first got you into building robots?

MinotaurRiobotz2 karma

Interest in robots: definitely sci fi movies. I watched Star Wars when I was a small kid and just wanted to build those robots. In school I loved physics and math. My BSc and MSc were in mechanical engineering, and I went to MIT to learn all about robotics. In late 2002, students told me about combat robots, and I got hooked after the first event I competed with them, in 2003.

MasterMarik1 karma

To both: Were you inspired by any of the past robots when you built yours? Also, where did your robot's name come from?

MinotaurRiobotz4 karma

Our first drum robot Touro (120lb), from 2006, was a mixture of several drum designs, such as Falcon, Tekka Maki, Angry Asp. We tried to get the best feature of each competitor, and then make our own unique design. Since then, we have been evolving our drumbot designs and trying other weight classes. Minotaur comes from Greek mythology. We wanted to keep our bull-related theme for drumbots, but we needed something beyond that. Not just a bull, but half man half bull. The Cretan Minotaur killed those who dared enter the Labyrinth. Our Minotaur does the same thing, but to those who dare enter the BattleBox!

Ravage1231 karma

What would be the best way to get involved in this sport? Any recommended skills/knowledge to have?

MinotaurRiobotz2 karma

Study and also get your hands dirty. Both theory and practice. There is a lot of knowledge on the internet (like our free tutorial). Attend an event, you will learn much faster with the interaction with other builders. Start building combat robots from lower weight categories, until you get the skills (and funding) for the heavier classes.

johndeer891 karma

What's the one robot that you want minotaur to fight?

MinotaurRiobotz4 karma

Tombstone. We admire highly destructive robots, no wonder we build them too.

JeNePasParleFrancais1 karma

Hi! What resources do you recommend for beginners hoping to get in to robotics? I'm a high school student who is very interested in robotics, but all of it honestly just seems so intimidating!

MinotaurRiobotz2 karma

Take a look at our RioBotz tutorial, it's free on our website. It is a good primer if you're into combat robots. Grant Imahara's Kickin' Bot is also wonderful: our first Brazilian championship in 2004 had a lot to do with that book, I learned a lot from it. For mobile robots in general, there are too many to name. Mobile Robots - Inspiration to Implementation (Jones, Flynn & Seiger) is a good one, very practical.

SpeedyEdie1 karma

Hello Al and Marco! How did you guys get into robotics/BattleBots? Was robotics a childhood hobby, or something you discovered in college?

MinotaurRiobotz2 karma

Sci fi movies like Star Wars embedded in me a desire to build robots, as far back as I can remember. When I was a kid I loved to disassemble my toys and try to reassemble them. At least try! So later I wanted to learn mechanical engineering and work with robots.

imawesome11241 karma

I got a question that applies to both builders:

That motor for Minotaur's weapon is ridiculous. It seems like it would be a real mindfuck to be fighting against a robot that sounds like a goddamn C-130 taxiing down a runway. Does it sound as intimidating in person as TV would make it seem?

Minotaur's my favorite actively fighting robot in the world by the way!

MinotaurRiobotz2 karma

Thanks! It is intimidating. Extremely loud. It is an adrenaline rush to be next to it. You can feel the vibration, feel the noise. No matter how much I trust the design and strength of Minotaur, it sometimes scares me. Especially knowing that my students are also working on it. Safety first.

InTupacWeTrust1 karma

Has Minotaur been your most successful robot?

MinotaurRiobotz5 karma

Technically, it is definitely the most advanced design we've created. We've always tried to build compact robots, but they were complicated in the early 2000's. As we got more experienced, we were able to make the robot simpler but more effective. As Einstein said, "Everything Should Be Made as Simple as Possible, But Not Simpler." Wise words. We simplify the design as much as possible, until it starts losing performance. Then we stop there. Not a bit simpler. From a media exposure point of view, Minotaur is definitely the most successful. For instance, the viral video made our facebook page double its number of page likes in a matter of days. What took us several years to get, now was there in a matter of days. It has been amazing.