Babróg V2
In 2020 I designed my third and, by far my most successful, beetleweight Babróg, a scaled down version of my featherweight Barróg Doom. Despite numerous updates to the components within the bot to improve reliability (the wheel hubs being redesigned twice, the servo hacked for continuous rotation, milled HDPE components), the actual design has remained relatively static since I initially competed way back at BBB Beetle Champs 2021, with basically none of the internal components changing. Last year’s champs however left me with a lot to think about regarding what needs to be improved going into the future, and while I did attend BBB Brawl 2024, it was only in a commentator role, while I worked on the first proper redesign for Babróg!
The old Babróg design I ran from 2021 to 2023. You can find that build diary on my FB page (Team Barróg) or over on the FRA forums: Babróg - Beetleweight Lifter Build Diary
The mostly completed CAD done in Fusion 360. Learning the new workflow could be painful at times, but I am very glad I persevered.
Going into designing the CAD (my first fully done in Fusion 360 after being finally unshackled from Solidworks), I had three main goals for improvements coming from my previous experiences:
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A more powerful lifter motor to replace the Robostar servo (as well as the large dual UBEC), capable of lifting greater loads far quicker, and without any fear of slipping mid-lift.
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A design that would, at the very least, be far less vulnerable to getting caught in positions where it could not self-right. This came down to having a lifter that could reach further backwards, as well as wheels that could grip the floor even if the robot was not completely flat on the ground.
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A link system that would instead mount to the main bulkheads of the robot as opposed to the top panel, which would make assembly and disassembly far less finicky.
For the lifter motor I could have gone for something more state-of-the-art used in some of the best current lifters, such as the SHV800 servo used in Luchador, or the Strangbox used in Grab Crab. However, these both came with an additional cost investment as well as minor reliability risks, and since I already had two 37mm 80RPM Pololu motors from running Schnake, I decided to use them as they had plenty of power as well as having a fantastic track record in BW robot combat. These motors however presented two significant technical challenges, that would shape the packaging of the entire build:
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They are big.
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They are heavy.
I also wanted to move my rear wheels back further out of the rear of my robot, which would mean going past the 5mm backplate as well as the rolled parts of my side panels. While I was somewhat tempted to upgrade my drive to something more powerful such as Repeat Maxes or Ranglebox Mars’, I had finally gotten the 1806/Robostars running 49mm custom cast wheels to a point where their reliability was perfect for my needs, and any upgrade would have required more internal space as well as being heavier, two things which were at an absolute premium in this design.
The new 37mm motor installed, alongside the smaller and lighter 380mAh 4S battery, down from Babróg V1’s 500mAh.
Since the original Babróg with the motors in the rear already had its wheels as far back as they could go, the only way I could push the wheels back was to move the motors to the front wheel, so that the driven wheels could have their drive axle positioned far enough back to stick out of the back. This also gave me more space to play with concerning the lifter motor, with one caveat; no matter what I did, the 37mm motor would need to stick out of the bulkheads somewhere due to its size, and with the robot already being shorter at the rear, it would push into either the wheels or the drive belts somewhere. My solution to this was to make the belts longer, and place tensioners at either side to create a U-shape, allowing the motor to fit in the newly formed gap. Technically I only needed to do this on one side, but for tensioning and driving consistency I decided to mirror this design, which would also in theory create a greater area of contact between the pulleys and the belt, reducing the risk of slipping further!
The new drive design, reusing the old wheels and with very simple tensioners consisting of 3D printed rollers and a small amount of Vaseline.
The wheels hanging out of the new design. This keeps some of the roller protection design, but also provides a major boost in mobility.
With the distance between the lifting motor and the lifter axle being even shorter than before, belts were no longer possible or necessary to reduce and transfer the necessary torque, so I decided to upgrade to gears instead. With some advice from Jack of Luchador and The Chilli Daddy. renown, I was able to design some double helical gears with an overall reduction of 11:16, and while I had a batch printed in some PLA-ST on my recently acquired Prusa Mk4, I was able to get a friend to print a batch in Onyx, which would stand up to basically anything the lifter could throw at them, as well as several type of weaponry. Outside of the redesigned lifter gear, I basically lifted the entire rest of the lifter assembly wholesale from the original Babróg, with the exception of properly milled antler grabbing arms (now with nails hammered into them for extra grip), and replacing the main 8mm steel lifter rod with a titanium shaft, a surprisingly cheap upgrade that saved a whopping 12g, which is more of a statement to how much weight I was chasing nearing the end of this build.
The new lifter design, as well as the new position for the motors.
Some of the changes I had to make between bulkhead iterations, which gives some perspective as to how much I was chasing every gram I could manage.
The jig I used to hammer nails into the grabbing arms, which were then trimmed to length using wire cutters.
For the front of the robot, things remained conceptually similar, but with small optimizations. The fork mounts were totally remade on the CNC mill, and the hardox forks were redesigned to be lighter while maintaining the same functionality. While the front panels were basically unchanged and interchangeable with Babróg V1 (plus a tiny bit of additional weight saving), the baseplate and side panels were redesigned to not stick out as far forward before, to prevent scenarios where they would warp the front of the bot following a hit, as happened in my matches against Ultra-Violence and Digestive. I was also finally able to experiment with TPU for the first time, which allowed me to print a thick TPU wedge I could use against horizontals in place of the titanium wedge. This wasn’t quite as durable as the titanium wedge, but it was wider, scraped the ground better, and was easy to replace provided I made enough spares.
The new TPU config, coming in at around the same weight as the old titanium config.
A pretty good comparison between the positions of key internal components between the two bots. From the outside you’d never know how different they were internally.
Fitting the same fuse/link hybrid into the robot proved rather tricky with the space provided with the new design. With the back of the bot lower down and the wheels now at the same level as the link, I barely had enough space to squeeze the link in near the top of the bulkhead, still relatively far away from any nasty hits (and also with a brand new TPU link door). As for the rest of the electronics, I needed to buy a new smaller 380mAh battery to barely fit underneath the motor, and what can only be described as a shelving unit was designed to fit the drive ESCs as well as the new lifter ESC, with a small BEC just floating around on top. Getting all of the wiring to fit was somehow even more of a challenge than with the original Babróg (with a special shout out to the lifter motor wires and the transmitter), but eventually all of the components were fitted, and to my absolute relief, it all worked!
All of the electronics packed in to the robot, somehow in an even more compact state than before.
The new TPU link door at the back, just barely able to fit.
And so this is the condition Babróg V2 was declared good to go. The initial tests of the bot proved promising, being easily able to lift the weight of a beetle and more with a good amount of speed, and this combined with the increased range and grippy spikes should make suplexes easier than ever to achieve. The drive meanwhile controlled just like before, and should keep everything that made the original drive so effective at controlling opponents. Barely making it into the weight limit with all of its different configs, it was ready to start competing at events again, and hopefully make the step up the original bot never managed, even if I was already aware that there was likely a long road of iteration ahead of this new Babróg as well!
The new Babróg, ready to compete in Robot Rebellion 2024!
