July 4th VCR Meet — Event Report
I was invited out to Las Vegas to a lowkey practice event to test my robots alongside the friendly people at Vegas Combat Robotics.
There were a total of 16 robots between 6 builders. I brought Sandstorm, Smokescreen, and Mirage to fight.
The whole deal was a relaxed grudge match format. Call someone out and fight them. Easy.
Mirage
I rebuilt Mirage again after getting my CNC router up and running.
Fight 1 — Vs Short Track 1
This was Mirage V3’s first flight. Short Track was a good opponent for Mirage since we were both vertical spinners of some sort. I don’t have any specific plans for fighting vertical spinners with Mirage, so I wanted to see which configurations worked.
In this first fight, I ran with the floor scraping wedgelets. These things are hilariously underbuilt so I made a bunch of them.
In this fight, as would be the case in further fights against Short Track, Mirage did more tanking than it did any actual damage. Most every collision resulted in Short Track biting into the floor and flinging itself away.
The fight was won after Mirage flipped Short Track into a position it could not recover from.
Fight 2— Vs Short Track 2
Same opponent, similar story. It did get a little spicy towards the end when I was flipped upside down. Mirage doesn’t drive all that well when inverted.
This time, the fight ended when Short Track went in for a hit and chaotically flipped itself into a KO.
Fight 3— Vs Short Track 3
In our third fight together, I ran the TPU wedge attachment just to see how it would do against a sharp weapon. I also went into the fight knowing that my weapon was having issues, more on this in a bit.
It was back and forth, and not in the exciting way. One robot would get a good hit or position and get itself stuck into a worse position. Repeat until the timer ran down.
Final Thoughts/Damage Report on Mirage V3
I’m thrilled with how well the new TPU/Garolite/Polycarbonate frame held up to hits from another vertical spinner. The redesign was a quick one and I’m happy with how well it stood up.
I did have a couple of issues.
On the weapon side, the new PLA hub eventually succumbed to heat creep warpage due to use and the Vegas heat. The hub houses a modified brushless rotor and a bushing. There’s about a 10 thou tolerance on bushing and magnet ring concentricity until the entire drum starts binding up. This builds up when the stator tends to heat up to over 50 deg C, dangerously close to the glass transition temperature of PLA.
I’m investigating solutions to this problem that keep the overall concept and contruction without relying on PLA.
Aside from the drum issues, Mirage performed pretty well structurally. The TPU wedge held up well too. The above picture is after I unpacked at home. It’s all cosmetic damage on the exterior.
Smokescreen
I didn’t really change Smokescreen after revealing it. I spent a lot of time on making the design work a little more reliably by switching the drive power over to timing belts and balancing the weapon. I soon learned that Smokescreen looks way better than it performs.
The drive was horribly underpowered, weapon had some reliability issues, and there were other drivetrain issues I wouldn’t find until I ran the wedge attachment.
Fight 1 — Vs Plague Rat
I’ve been anticipating the Smokescreen vs Plague Rat fight since way back in March. I really wanted to see what would happen if I faced another vertical spinner, and Plague Rat is an absolutely massive vertical spinner.
Pre-fight, one of Plague Rat’s weapon spacers shattered, causing a major balance issue. We agreed to continue to fight regardless.
It starts off with Smokescreen’s anemic drivetrain limping across the 6ft box over to a chaotically vibrating Plague Rat. After a quick blow due to my bad positioning,I was able to get around to his side and underneath him using my magnetized wedgelets. The fight was over soon after. I hit him twice before ejecting his battery.
Fight 2— Vs Purple Nurple
Purple Nurple is a powerful horizontal spinner with proven maneuverability over Smokescreen. Knowing this, I went for the TPU wedge attachment and a more cautious strategy.
To open the fight, I backed myself into the starting corner to give Purple Nurple 2 options to hit me — Try to bite my wedge head on, or hit the steel walls on either side of me.
The wedge happily face tanked every hit that connected. Once I noticed that, I decided to spend more time trying to cause damage by deflecting hits and throwing Purple Nurple off balance.
It was a fairly boring fight due to my defensive strategy and Smokescreen’s embarrassment of a drivetrain. At home, I had some issues with the wedge scraping the ground. I did as much as I could to fix that, but I didn’t account for the gouges in the arena floor.
I eventually won due to Purple Nurple’s weapon self destructing.
Fight 3— Vs Spoops
I switched back to the magnetic wedgelet attachment for this fight, despite facing a horizontal undercutter. I didn’t want to cripple the drivetrain further with the wedge.
Additionally, I found that one of the drive gearboxes started binding up again. After replacing this, I was ready to fight again.
Because of the drivetrain’s low power, I wasn’t able to get any sort of decent bite on Spoops. We paused to let Spoops flip over, and soon after that I clipped their disk and the fight was over.
Final Thoughts/Damage Report on Smokescreen
I’m happy that there were no catastrophic issues with Smokescreen like I’ve had with other new robots. I was initially very happy with the aesthetics of the robot. After a few months of testing, I came to hate a lot of the design choices I made for the robot. I’ll be redesigning it for the future.
As for damage, Smokescreen didn’t really see anything that warranted any major replacements.
Sandstorm
I rebuilt Sandstorm entirely for this event. You can read more about it in a previous post.
I was pretty happy with how complete the robot was going in. I didn’t have any major issues like the previous versions of sandstorm had.
Fight 1 — Vs Off Track
In this first fight against Off Track, I went with the long pivoting fork configuration to counter his similar setup.
In this fight, I found a fun issue with the geometry of the robot’s frame where I’m super vulnerable to T-bones. Coupled with my rapidly deteriorating traction due to debris and the fight became more of a who can land a real hit first.
After exchanging blows a couple of times, I went in for another hit when I got caught on one of the wall seams. I called for an unstick when Off Track found that he had already lost a drivetrain side and we ended the fight there.
Fight 2— Vs Meddler
This was another good fight to test V4. Meddler is a very robust wedge bot with a pretty good record of tanking lots of hits from other vertical spinners.
I ran with the short fork configuration since I saw that there were a couple of gouges in his wedge that i could probably take advantage of.
The fight started off with Meddler exploiting my T-bone vulnerability. The new plastic scrapers they added made it very difficult for my fork to get underneath. Another issue they exposed was Sandstorm’s painfully slow drivetrain.
I was able to get a couple of good hits in until my weapon pulley shattered on the final impact. I didn’t recover the wreckage, but using the above video, I’m assuming that it broke along a stress riser I added while trying to combat another issue. I think the screws holding the pulley to the hub backed out, as they tended to do in testing. This caused some slop which amplified shock loading on weapon startup and on impact, essentially wherever there was a differential in the motor speed and the weapon speed.
The fight continued to the full 3 minutes and lost the decision.
Fight 3— Off Track
Because of the failed weapon pulley from the previous fight, I ended up swapping in my entire disk assembly to replace the bar. Replacing the pulley itself wouldn’t have saved much more time than just a full swap.
I went into this with the same strategy I used in Smokescreen vs Purple Nurple. Back into the corner and limit the number of options for impact.
The real fight started slightly out of frame when I tried to spin my weapon up to full speed. Upon collision, Sandstorm turned a bit and ended up gyroing upside down. Within seconds, my weapon motor shaft sheared itself and disabled my weapon for the entirety of the fight.
I tried to salvage the fight with control, but it was futile with Off Track’s very much functional weapon buzzing away.
I tapped out to save myself some time and money on repairing it at home.
Final Thoughts/Damage Report on Sandstorm
I was able to get a lot of info on some potential weak points on Sandstorm. Here are a few pictures.
Two things here.
Center of frame, Off track delaminated my bumper attachment. This was good because it prevented more catastrophic damage on the actual frame. This was bad because it only took 1 hit to delaminate. I believe the root causes were the design of the bumper and some potential underextrusion while printing. I think I’ll tweak the design just a bit, but this was a failure that I’m ok with.
On the left, I pocketed the weapon mounting plates too aggressively and that created a massive stress riser right where it was designed to take impact. There is a massive pocket in the middle of the frame, a slot for the baseplate of the weapon assembly, and a corner relief due to how the part was manufactured. I’ll be beefing this area up with fewer pockets and potentially make some thin titanium braces to support it.
The damage on this wheel guard occurred over the course of both fights with Off Track. Most interestingly, the first hit that off track scored on the wheel guard only delaminated the single outer perimeter wall.
And as expected, further impacts in the second fight caused the plastite mounting screws to tear out of the frame and cause some further delamination along the layer lines. I think I’ll just use longer screws and a more substantial thread to ensure that tearout damage only occurs on the bumper and not the frame.
This failure was interesting. The weapon motor shaft itself sheared at the start of my second fight against Off Track. The really odd part is there doesn’t seem to be any sign of the weapon itself hitting the pulley. As with previous failures of this nature, the shaft failed along the stress riser in the groove for the retaining ring.
I think I made the right move with the V4 build. V3 is now officially retired. I’ll be addressing some other issues for the next event:
- Drive wheel traction tends to drop off as the wheels pick up dust and debris. I’m going to play with cutting treads into the wheels that I’m currently using, trying out the softer wheels from Vex/WCP, or replacing them altogether with a CNC’d foam and latex solution. I also have some colson wheels I’d like to play with too.
- I want to revisit the weapon hub design to improve the pulley mounting interface. I’d really like to have a solution that would allow me to use a pulley that isn’t 3D printed.
- Redoing the magnet carrier plate for stronger/lighter magnets.
Overall, I’m happy with how the robots performed and I got a lot of good info on how to improve them. I firmly believe that in robots you should be able to fail fast and fail often and being able to practice against other builders is the best way to do this.