CDG, THE ORIGINAL
Hello All,
Some of you may be familiar with my beetleweight CDG and as I haven’t made any changes to it in a while I think it is a good time to go over how it became a working (ish) robot that has survived being beaten up in multiple events at this point.
There are many many good build logs and guides on this Forum and the BBB website as a while but this will start as a great example of what NOT to do.
The Concept:
The idea for CDG originally came from watching NHRL and seeing SMEEEEEE with it’s detachable horizontal spinner (to get the NHRL weight bonus). As shown in this fight. https://www.youtube.com/watch?v=R96ZgEGef-4
The idea was simply what if the spinner was on the front not the back so that the forks and spinner would work at the same time.
I originally made CDG in a video game under the name Coup De Grâce and it looked a lot more like Smeee with an undercutter in the middle than the first version of the beetle did.
The first beetle event I attended was BBB brawl 2022 as part of a pit crew for one of the Lboro Uni bots called Disorder which was built by Max who was the Chair of the society at the time. For Brawl 2023 I decided to build my own beetle. Originally I was going to build a lifter for the event but as a CAD exercise also designed the original version of CDG with all the very little experience I had with bots on a whole and especially spinners. I had used spinners in video games and had built an antweight lifter/flipper at this point but didn’t understand at all how to mount a spinner and it really showed.
I wanted to make it an undercutter but had no idea how to make it both low AND not needlessly complicated to build so instead I made it a flat midcutter.
Regardless at a society social we were discussing the brawl event and what the plans were and when I showed both the lifter and CDG I was encouraged to build CDG. Unsurprisingly it was simply because it was weird looking and cool not the sensible thing to do.
The design and flaws
The CAD was polished up and missing features added but most of it remained the same. it drove using BBB 22mm gearmotors and an Overlander 3530 1100Kv for the spinner. All of this was running off of a 4S 850mah LiPo battery.
Once the CAD was done it was very clear what most of the issues would be before I had even used it. I had ordered the weapon once I had decided on the size needed for components and got this ordered in a waterjet group order (Thanks Sion). My rushing to get this ordered caused 2 issues. 1 was that I had turned the bolt holes on the weapon into construction lines by accident so when I got my weapon it had no bolt holes and I had to spend money to get them machined.
The other was the weapon supports. I had realised that the 3mm hardox I wanted to get them made from would be too heavy. The solution was to make them 2mm. I then promptly learnt that 2mm hardox is almost non-existent. This meant that I had an issue as I couldn’t go for a lighter material as it would need to be thicker and I hadn’t designed the clearance for more than 3mm thickness so the wedges would no longer be on the floor. At 2mm no material I found would be strong enough so there were only 2 options. Either I would have to spend alot more on 3mm Ti supports or buy some 2mm mild steel to use and hope that I didn’t fight a vertical spinner.
I just sent it and chose the latter to save some money. I just accepted that if I fought a vertical I might have had to bend the supports back into shape.
The final MAJOR issues
If anyone has a memory good enough to remember Brawl 2022 then they will remember that CDG was missing a weapon and was instead a hugging wedge. There were 2 causes of this:
- I had limited time in the Uni workshop and hadn’t had time to machine the custom weapon axle that i had designed. I could have solved this easily by drilling the holes out and slapping in a shoulder bolt.
- The machining of the holes in the weapon took time and postage took time. This meant that while I had left a month for the weapon to be machined and make its way to me when the big day of the event rolled around the weapon was still in transit. The weapon arrived the next Friday.
THE EVENT
When I showed up to BBB Brawl 2023 the bot weighed half the weight limit and was weapon-less so I had very low expectations.
On top of that I was in the first fight and had been rushing around trying to fix a solder on the power light so hadn’t had time to fully prepare (maybe forshadowing 
)
Fight 1: VS Muhammad Al-Bee AND James and Dan’s robot
This fight was going well. Muhammad Al-Bee had got themselves stuck under the arena wall immediately and CDG was so wide it was easy to stop the spin up of the horizontal and control them.
That was until my wheel fell off. Yep in my rush to the first fight I hadn’t had time to locktite the grub screws on the wheels and it had cost me a fight immediately. Never mind, Onwards and upwards.
Fight 2: Vs Spins and Needles
This fight I was against a team mate in Spins and Needles by Peter (Another Lboro student). The hole in the middle of my bot was almost big enough to enclose the inner ring of the opponent. IIRC I won this fight as when I was hit one of the bearings on Spins and Needles Jammed and caused the weapon ESC to burn out. This meant that the weapon-less bot beat the bot that is surrounded by weapon on the damage/weapon effectiveness category.
Fight 3: Vs Chain Bastard
One of my favourite fights. It was a very close controlling fight in spite of the lack of mass of CDG causing it traction issues. I had great fun and I don’t think there was anyone I would rather have lost to.
FOOTBALL
While I was working on a new version of CDG there was a football event at Robonerd 2023. I was working on some brushless drive conversions for the new version after being given the idea by Sion and tried them out at this event.
Bot changes:
For the football I flipped the central printed piece upside down to make sure the ball couldn’t get under me and I added some brushless rotalink conversions using 1900Kv Brotherhobby 1507s.
I was teamed up with James and his bot Nitrite. We did pretty well as a team with 7 or 8 goals in the event 4 of which were me and I had a great time.
This was the last time I used this bot for anything other than demonstration purposes so concludes the how NOT to make a beetle part of this build log. There are other issues that occurred with the 2nd version but less so meaning I won’t be going over them unless they lost me a fight.