If you've been following Bots FC, then you know we like overhead hammer robots, and you probably know about our affinity for unique drive methods. But maybe you just heard about us from Battlebots and decided to come take a look. So let's dive into Shatter! and what makes it unique, and what change's we've made vs our previous HW robots Blue and Mega Melvin. More after the break. Click here!
For those unfamiliar, we have a history of building HW hammer robots dating back to 2016 when we made the very first version of Mega Melvin. Made from mostly off the shelf components simply cut to size, this was effectively a test platform for some brushless motors we liked:
The motors worked well so we upgraded it for Robogames 2017:
We learned a lot at Robogames where we unfortunately lost our only two fights by knockout (ugh) before being banned from a grudge match due to fear of us damaging the floor...
After Robogames we actually ended up fighting two seasons on Chinese television with a slightly modified Mega Melvin, renamed and repainted to become "Blue". This robot, in two seasons of TV, went 7-1 and was the only undefeated robot on "This is Fighting Robots". TiFR was an online show viewed over 100 million times PER EPISODE on Youku! Insane.
What Changed & What Didn't?
You can read a lot about our experiences in China and buildings these robots on the rest of the blog. But let's talk about Shatter!
The overall strategy of the robot is much the same. It's an overhead hammer robot designed to fire a LOT in a single fight. We're talking 50 hammer swings a match. We've balanced the power of the hammer, the weight distribution, the shape, everything so that we can get as hard a swing as possible while being as stable as possible. We pair that with omni-directional drive so we can go sideways and literally "drive circles" around opponents, and lots of armor.
Shatter! however is a ground up rebuild of the robot using the learnings from China to inform the new design, so let's talk about what's the same and what's different vs our previous robots.
First off, with what probably is our defining feature if you've seen us fight, we kept the mecanum omni wheels. These are what allow us to drive sideways and we love them.
Mecanum wheels are a type of omni-directional drive, and they're a bit difficult to explain. But don't worry, we're working on an in-depth blog post for later in the season that dives into exactly how these things work! We'll even have a cool CGI animation!
The brushless motors and gearboxes that power the drive have been working great. Putting out about 10kw during a fight, they have plenty of power to move us around. Everything that made Blue move was carried over into the design of Shatter! We'd like to thank sponsor Banebots for helping out with our gearboxes this season.
Battery wise, we upgraded to maxamps thanks to a great discount we got. Sponsors are awesome! These shaved off several pounds of weight and a lot of space internally. Always a bonus!
We love the construction method we use, waterjet cutting, and we love titanium. So we teamed up with sponsors Meer Precision and TMS Titanium to use a LOT more custom cut titanium this year. We ordered over 300 lbs of the stuff!
Despite starting with over 300 lbs of titanium, once it was all cut we saved a LOT of weight vs our aluminum configuration. About 15 lbs or so. We even went ahead and waterjet some holes in our sprockets to shave off even more weight. You can never be too efficient with weight in this sport.
While we were recutting everything to be lighter, we also redesigned everything... slightly. The overall geometry was working great but we wanted to be able to more easily repair the robot in the pits. I'm not going to bore you with all the details now, but the entire frame was redesigned to come apart and go together more easily, and be more rigid when fully assembled. Everything slotted together like magic when we got it back from the shop.
On the inside, we never liked how it was all arranged in Blue. Everything was shock mounted and it held together just fine, but it was also all zip tied in place and it was a nightmare to replace anything. So for Shatter! we made some 3D printed internal dividers so that every piece of electronics slid into its own custom foam-lined container. It was glorious. Check out how nicely everything fits in this test video:
Now this wasn't anything crazy: it was just some PLA walls that we dropped into the chassis and lined with foam. We'll be going into some detail on these later as we really like this idea (I may or may not have stolen this idea from the Megabyte team...). Also, we still had a lot of zip ties. But way less than last time!
Our weapon system worked great in China, but we once again decided to make the hammer heavier. The hammer has gotten heavier at every event and Battlebots was of course no exception. We think this was a great use of some of the weight we saved with our other changes. We'll probably do a whole post on the hammer, but check out how pretty the new AR500 steel hammer is:
We still have 20kw of brushless power into the axe and the drive system is all the same as you can read about in the blog. This system has really proven itself over the last 3 years for us. It's durable, and you can fire it over 50 times a fight no problem. Check out this dramatic late night test fire:
One of the biggest issues with the hammer in China was damaging our own robot on the backswing. Originally the robot was designed so the hammer just hit the ground on the backswing. But sometimes the robot is flying through the air, or it's hopped up a little bit... and then instead of the floor you end up hitting the rear wedge. If you hit the rear wedge too hard then you end up bending the rear wedge and actually hitting the shaft for the hammer gear system which can jam the hammer. This was bad, so we ended up adding a nice spring loaded UHMW stop to the rear wedge.
This backstop worked great in practice. Let's hope it stands up to 50 hits during battle! The other benefit is that the hammer no longer dragged along the ground during a fight.
Lastly we made new hammer arms to better match the aesthetic of Shatter! Speaking of the looks...
Shatter! looks a lot different from Blue and that's mainly due to the ablative plastic armor panels we've added all around the robot. Armor is the name of the name of the game when you need to take on the massive spinners at Battlebots. We'll be doing more posts about this later as our armor strategy was a huge differentiator between Shatter! and the other robots at Battlebots this year.
Due to slightly different weight classes between US/China and all the weight we shaved off the bot due to design changes we had almost 30 lbs of free weight. Other than a few pounds in the hammer, all that weight went to armor.
I was always a bit worried with Blue that a big spinner could tear it apart. We had a 1/2" thick titanium plow up front, but only 1" aluminum on the sides which could not take a hit. We didn't want to have that worry about the armor on Shatter! So we did something completely weird.
Ablative armor is a strategy a bit different than normal. Most people use hard steel or titanium, and angle it so that big spinning weapons bounce and deflect off, unable to damage the robot. Ablative armor is the opposite: it's soft and meant to be torn away by an opponent's weapon. But why would we want soft tearable armor?
Well, to start, soft is a relative word. This stuff is still very hard, and is in fact more wear resistant than hardened steel. It takes a lot of energy to tear into it. We use UHMW PE, or ultra high molecular weight poly ethylene, plastic. The stuff is almost impossible to break, instead it just bends. It's the same material Huge's wheels are made from. Our thought was if a spinner can't get a good bite then it can't flip us, it can't toss us: the armor will just slow them down.
We tested this out at a lower weightclass, with a 45 lbs shuffling featherweight named "Knock Off White".
At Motorama this robot went 2-2 and was overall pretty great. Its downfall was poorly mounted drive motors, but the armor was awesome and took on some brutal spinners. Everything you see in white in the photo is UHMW. We only ever had to replace a few shuffler feet, the front wedge held up great.
So we made 4 full sets of the stuff for the HW anyway in case it got torn up.
Here are a few of the pieces for Shatter!, before they are wrapped in our mirror vinyl, machined from solid UHMW. One set of ablative armor weighs 30 lbs!
We've shaped it very carefully, which we'll detail out in the future, but a lot of people ask about the triangles. We carefully thought about horizontal spinners, vertical spinners, drums, etc, but even still it could have been a lot simpler. Well, we made it look like triangles because we thought it would look cool on video (spoiler alert: it did :-)
Just in case the ablative armor strategy didn't work, we put 1/2" grade 5 titanium behind all of it. So on the front and sides we have 3" of UHMW PE and 1/2" of titanium. I think it's safe to say we were the most well armored robot going into Battlebots this season. Tune in to see if that strategy pays off!
We don't push well. That's just a fact of the matter with mecanum wheels. We can drive sideways but we lose pushing force. Even still it's nice not to always have people get under you. Blue and Mega Melvin had 1/2" ground clearance all around. This was great and allowed us to never get high centered on the notoriously uneven floors of a robot combat arena, but it was bad because EVERYONE got under us.
So for this season we wanted some ground scraping wedgelets up front. With how many ground scraping vertical spinner robots there were, it felt like a necessity. You can see them below in this early assembly photo, before the ablative armor was added and before everything was painted.
We didn't have a lot of weight to spare for these. They're made of 1/2" grade 5 titanium and are mounted on 0.75" hardened steel shafts. When we run these, we actually have to run a slightly thinner, 0.4" titanium plow instead of the 0.5" titanium plow. So it's a slight tradeoff. Do they work? They worked great in the test box!
That's basically Shatter! for you. We will be posting a lot during the season with technical details, fight breakdowns, behind the scenes info and more, so keep watching this space.
Battlebots was a dream come true for us, and we cannot wait to live it all over again on TV.
Check us out Fridays at 8pm all summer long on the Discovery channel! Check www.battlebots.com for more info!
Dont' forget to follow us on Instagram and Twitter where we post a lot more often with more bite sized content. We use the blog for longer-form information.
Lastly, I just wanted to thank our biggest sponsor, my employer frog design, for helping us with the rest of the costs.