Overclocked - a Shuffling Axebot

Back when I started designing my half of Accept Cookies, I wondered if the weapon motor could be put onto a beetle. Thus I started planning…

The idea was to use dual cam shuffling pods, which would be bolted on separately, so if necesary I could swap out a drive pod quickly. Big thanks to Sion for your help and chats about shuffling mechs.

I also reused the forks and axe arms from PMXL, to save on some costs.

First thing to prototype was the shuffling mechanism. V1 uses a BBB brushed motor, with a 24:20 reduction to the cams.

Okay, I had the mechanism working, now I needed to get some speed out of it. I tried my 1804s on a 5:1 gearbox, but they lacked the torque to move the shufflers. I then spied a 2836 on my shelf from older versions of PMXL’s weapon. Hmm…

That’s more like it! Next step was to get some grip. Around this time, I also picked up a Bambu P1S as they were having a big sale. As an aside, I didn’t realise how good some of the more modern features like a magnetic build plate or auto-bed levelling were to the printing experience until I got this.

With grippy feet, this really became responsive.

With that done, I could then focus on the main build.

At this point, I realised I had run out of the usual natural TPU I use, and with them being out of stock, I bought some blue TPU. I think it ended up looking quite nice.

As it stands, it is a few grams over the weight limit, so I’m going to need to pocket a load of the HDPE. I also had to print my TPU with fewer walls than I’d like (3 instead of 5) to further cut weight, and there’s no way I’ll be able to run 4 forks at once.

I did a drive test once assembled, and started melting the gears on the left hand side after about 30 seconds! I’ll need to come up with a way of mitigating that problem. Some lithium grese might help, but is probably going to leave a residue across the floor as it is an open gearbox.

Overclocked is set to debut at BBB Summer Showdown on 20th July!

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Thomas when someone says “Beetle axes can’t do damage”

Incredible build mate, love to see you continuing to push the boundaries of what’s possible at this scale!

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From video’s I’ve seen, it’s mostly about how sharp the axe is and/or how much air space is in the robot being hit.

You don’t see many shufflerbots around, so it’s good to know at least a few robots are benefiting from the shuffler weight bonus.

I think there’s a few factors limiting the effectiveness of beetleweight axes.

Primarily, I think the typical construction of beetles (HDPE top plates, ~5mm thick) has the right amount of flexiblity and thickness to prevent axes from fully piercing them. I’ve only managed around 2mm of penetration against HDPE in testing. When I was over in the US, I was chatting to some folks and they said the typical top plates over there are 1-1.5mm carbon fibre, which I reckon axes would have a much easier time with piercing.

As you say, the sharpness of the axe also contributes to its ability to pierce armour.

Mass is important as well. You want more mass at the tip of the axe head for more force when landing blows, but that also increases the bucking when you fire the axe. Even with the relatively light axe heads on PMXL (ranging from around 28g to 40g IIRC), I still get a bit of bucking, and when I tested additional weight (by stacking multiple axe heads together), the bucking only increased, which actually reduced the damage on my test piece as a lot less force actually went into the target.

This has led me to believe that the way to increase damage in a beetleweight axe is to increase the velocity of the axe. In PMXL, the theoretical tip speed is around 28mph, and for Overclocked, I’ve increased the theoretical to ~42mph. Of course, they’re not actually going to reach these speeds, the unbalanced rotating mass and the ~180 degrees that it rotates limits the acceleration that can be achieved. However, I think the true utility of an axe is to hit vulnerable parts of the opponent, such as the link or exposed belts. I’ve yet to cut a belt, but I have managed 3 link snipes!

I should be soldering up the weapon ESC today, so I can start testing the weapon.

what a beauty! and moves great for a shuffler, really was surprised by that turn of speed.

whats the idea behind the front pointy bit of the shuffler btw? seems like it would be pretty fragile compared to the rest of the system

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Yeah, they’ll be be pretty fragile. I guess it’s an oversight on the leg design, but I didn’t like the look of big leg panels as much, and the legs did need to taper towards the front anyway because of the wedge.

Got the weapon wired up today, and it feels more impactful - when I blip the firing button, it has enough speed to recoil when hitting the end stop/target that it bounces back in a sort of auto-retract! However, inspecting the target, it didn’t look like it had done much more than PMXL. I’ll try some heavier axe heads (I conducted the test with my lightest axe head, a 3mm hardox piece around 28g), if the pocketing of the HDPE parts saves sufficient weight.

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