Dom's Decalodon Design Diary of Doom

Hello! I’m Dom, my robot’s called Decalodon, and this is a Design Diary!

I fancy having a wee go at one of these threads and go all product design student on it - I think talking about my design inspirations/intent, feedback from testing, concept sketchy stuff etc is as equally fun as discussing the tech and engineering. This might end up being a bit of a messy/boring design thought dump (Hence the Doom)! But if writing stuff continues to be fun, then I will keep updating! :stuck_out_tongue_winking_eye:

(Awesome photo by Stuart Camp!)

So! Context! This is Decalodon! I super love the grungy design language old of school Robot Wars - especially the evil house robots, which captured the imagination of fans and new audiences. So I wanted to attempt a design that was characterful and reminiscent of this vibe.

The weapon was chosen to be a grabbing arm, 'cos I thought the claws on Bash and Killalot looked mean as heck. I wanted the robot to be nimble and animated (Bots like Razer and Warhead are still iconic designs as they almost seem alive), so lots of floppy forks and a designated shrimech was implemented into the design. Whilst most of the bot is made with HDPE plastic - I wanted the jaws, fork tips and other key parts to be shiny aluminium for a more aggressive look.

(Video showing off how animated Warhead is - I dream to build robots as cool as this!)

(These guys need no introduction - but consider this a soft “mood board”)

For my design, I also wanted to keep the centre of gravity as low as possible considering the shape of the robot, and to achieve high manoeuvrability and drive torque - so it’s running two 2S packs (for a 4S equivalent), with four BBB 22mm motors on teeny weeny foam wheels and very low (but chonky) outer armour panels.

I experimented with a servo for the first time, to operate my shrimech. And for the jaws, this puny little linac from ebay, which was small and light enough to fit into the bot.

I don’t think the build phase itself is that interesting, except that fabricating these jaws was a bit of a nightmare - cut with a jigsaw from ali box section, I spent a very sweaty day in the shed and went through several failed attempts until I ended up with these. I also cut a slot so that when the jaw is hit from underneath by verts it flops back and reduces the shock sent to the linac assembly, but when it’s time to clamp and the linac engages, it stays rigid. Or at least that was the design intent - more on that later.
(Also wee shout out to the legends at University of Strathclyde DMEM for waterjet cutting the HDPE chassis :stuck_out_tongue_winking_eye:!)

For once my robot was finished on time - ready for the BBB Brawl in February (just barely - Sorry, Joe!) ! The confusing name Decalodon was hastily made up on the night of the deadline (Sorry, commentary team!) - if it were translated it could mean “Ten Tooth”. Wasn’t fond of it at first, but I reckon it’s starting to stick!

How did Decalodon perform? Did I accidentally drive into the pit multiple times as I do every event? And what about that jaw design, I hear you ask? Tune in next time for Decalodon’s exciting adventures at the BBB Brawl.


As a university entrant (woohoo Strath!) I was entered into the student bracket of the BBB February Brawl. I’d quickly like to thank all the lovely people who gave nice words about Decalodon’s design! :blush: Whilst I have a while to go before reaching the lofty heights of Chris Reynold’s house robots and the Razer team, it really makes all the effort worth it to know that people enjoyed watching Decalodon in the arena. And super thanks to the wonderful BBBBois for hosting the brilliant event.

Decalodon won 1 fight, lost the second round to a judge’s decision, and then lost a final whiteboard match by driving into the pit (Oops!). Rather than go deep into each battle I’ll do an overall recap of the good, the bad, and improvements for the next iteration.

The Good :star_struck:

• The drive was very nippy and easy to control. The low centre of mass made Decalodon very planted to the ground despite it’s tall stature. Decent torque & grip to push around the opponents, partly thanks to the copydex coating on the wheels.
• Decalodon took a bit of a beating from Scott’s Hammersaw, Attitude Adjuster, but it kept driving along fine. Despite the significant amount of weight saving gaps in the bulkheads, structural damage was pretty minimal. The tall stance of the robot and the low mounting of electronics meant there was a lot of “nothing” to go through before the juicy stuff was hit.
• The aluminium jaws and forks were excellent at deflecting blows and tangling up weapons. The floppy jaw design was really effective at absorbing energy, and was a pretty good visual for demonstrating control to the judges.
• Servos are actually really useful! I don’t know how I’ve managed to be in the robot building space for so long without using any, but I’m definitely a servo fan now! Especially with the ratcheting engaged on my transmitter, accurately positioning the self righter was an absolute breeze.

The Bad :hot_face:

• The ebay linac was absolutely pathetic – slow, expensive and underpowered. I was never expecting it to crush anything, but it was hoping for a better performance than that! Definitely to be avoided!
• Decalodon couldn’t really do all that much to the opposing robots – grabbing is cool and all, but without a decent wedge to lift opponents’ wheels off the ground, it was hard to control opponents while they were sat in the jaws.
• Battery removal and charging procedure was a complete faff. Much more complicated and fiddly than it needed to be, especially with two 2s LiPos to charge each fight.
• The self-righter linkage was a bit pants for the entire event and exploded when hit by Attitude Adjuster. Ruben of Panthor nicely donated some elastic bungee stuff which somewhat helped the srimech return to its rest position after usage.

Decalodon Chomping

Improvements for version 2 :thinking:

• Bin the linac!
• Design a reliable way of lifting other robots off the ground so that they are easier to push
• An actual paint job – I ran out of time for any graphics work on Decalodon
• Refine the floppy jaw setup further.
• Put more focus onto wire routing and battery placement – perhaps save some weight for 3D printed internal guides and spacers.
• Improve the srimech geometry and linkage
• A new name that is easier to pronounce?


So with that said! Now the fun part begins and I can start working on version 2! I’m aiming to have Decalodon 2 completed by early next year. (or something else if I get bored of grabby things and change my mind)


I love the look of Decalodon - we were pitted next to you in Feb and I can confirm it looks just as good in real life! What I find really nice about it is that you’ve got this really organic look even though it’s almost entirely straight edges. Hope you find a decent linac for the grabber. :slight_smile:

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You’ve absolutely nailed the look - very Growler!

I really enjoyed that first fight with you, and you definitely earned the judges decision. I really wasn’t prepared for how hard AntiThesis would be to control.

Finding good linacs at beetle size is a nightmare I’m afraid. They’re all either too small or far too large. Those little ones are powered by n20s! I had to build my own, inspired by Unconscious 514, and it still weighs something like 350g. Outputs as much force as you could possibly want in a beetle though.
If you’re just trying to grab a large servo is much easier.