Antweight Combat Spinner Bot - Shrapnel

by Fryddog, published

Antweight Combat Spinner Bot - Shrapnel by Fryddog Jul 27, 2016
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V11 Update:
Found two issues with Shrapnel. First, I would never be able to go to full speed with the weapon and would always vibrate wildly when at greater than half throttle. Second, due to the strength of the weapon motor and because the motor is only mounted to the top half of the chassis, the motor ripped clean out off the chassis on more than one occasion.
This version fixes these issues:

  • Shortened the chassis by 5mm.
  • Made the motor mounting area a little larger.
  • Allowed for an M2 screw and nylock nut to be held in the front bottom section hole. This screw is trimmed to sit inside the center hole of the weapon bar. I also trimmed the shaft of the motor to make room for this screw.
    With these changes, Shrapnel can now spin the weapon to full speed and the motor hasn't ripped out yet!
    Also uploaded a shorter weapon lock and a stand for Shrapnel.

V10 Update:
Gave Shrapnel a wedge on the back, increased the underneath clearance by 0.5mm and changed the side columns so that they are hollow. Each of these hollow columns hold two nylon spacers that get secured by two M3 nylon screws each.
These changes were added after a few fights using the V8.0 Shrapnel. The layers split at the columns and he got stuck around the arena sometimes. If you're interested in printing or messing around with V8.0, I've now added it to this thing.

This is my 3D printed design of a bot used in our 150 gram Antweight combat league. I've named him Shrapnel.
He is a horizontal spinning weapon bot and weighs in at 148 grams! (not counting the weapon lock)

This bot leaves a lot for you to customize as far as the internal components go but please use this list of components that I used to make Shrapnel as a guide to get you started:


  • Print out The Version 10 top and bottom sections and two motor mounts. Drill out the holes described above.
  • Mount the brushless motor up front and the two drive motors on the sides, using the motor clamps to secure the motors.
  • Solder up your power circuit. Connect the battery positive to one side of the power switch. Connect other side of the power switch to all of the ESC positives and to the anode of the led. Connect the battery negative to all of the ESC negatives and to a 220ohm resistor. The resistor then connects to the cathode of the led.
  • The ESC's may come with switches of their own. Cut these off and short together these wires on only ONE of the ESC's.
  • Shorten your ESC leads that go to the receiver and either solder them directly to the receiver or splice in connectors that can plug right in. You can lose a save of weight doing this and it is far easier when fitting everything inside. The plugs you use will depend on the receiver you select. The micro receiver listed above uses Micro Molex 3 Pin connectors. (I prefer using the plugs, I like to make sure everything can be unplugged and swapped out easily).
  • Plug the ESC leads into your receiver. I connected the brushless ESC to the throttle channel on the receiver. This is important because this bot will vibrate a LOT and likely damage itself if your weapon bar is not balanced well enough. By using the throttle control, I can increase the throttle gradually and find the sweet spot before the bot starts vibrating and still be effective in the fighting ring. You can avoid this issue all together by using a lighter aluminium bar or blade (approx 10 grams). It won't be as effective when fighting but the bot will barely vibrate at all.
  • Secure the ESC, battery, power switch and any loose wires with some super glue or hot glue.
  • Manufacture your weapon bar with the material of your choice. Follow the diagram on the brushless motor's eBay page for screw hole placement.
  • Mount the weapon bar to the brushless motor with the M2 screws.
  • Attach the top section to the bottom with the M3 screws; two on each side and one on the rear of the bot.
  • Before you power your bot on, always power the transmitter on first and always have the weapon lock fitted. The weapon lock should be printed or spray painted afterwards in a highly visible color for safety.

Here's a video of a time lapse build of Shrapnel:

And here's a video of him in action:

Print Settings


Flashforge Dreamer








Layer height: 0.2mm
Print speed: 40mm/s
Shells/layers: 2
Print material: ABS
Supports: Required for the rear of the top and bottom sections.

Designed using Sketchup.


I gave the whole chassis a coat of red spray paint, faded with some black. I used Tamiya hobby spray paint. What ever works for you really.

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I noticed you added a cover. What's it for?

Not quite sure what you mean by cover. Do you mean the weapon lock? It slides in over the chassis to prevent the weapon from moving when it's not in an arena (a requirement of all robot fighting events)

Not that. How do you reply so fast? I mean the thing that says Shrapnel on it. It also resembles the shape.

That's a stand for it. Tournament rules usually require you to keep your bot on a stand so that the wheels don't touch anything when you are in the pits, that's what the stand is for.

Consider changing the link to the proposed brushed ESC with brake in the descripton. Many ESC's with brake do not work well, you have to move the stick twice to change direction. They make basically the same 10A ESC without brake which works as intended and gives quick direction changes. Great design, Thanks. Building up 2 with my kids here in the States.

You're right I've since stopped using braked esc's but must have forgotten to update this page. Apologies!

Antweight needs to be 10x10x10cm max? I printed the first plate and its more then 10cm?

You're right for competing in the UK.
This bot was designed and used in Australia, where the 4"x4"x4" size is not enforced in the rulesets followed here (sparc.tools).
Sorry, I should have mentioned that in the description.

disculpen tengo motores dc sera que me podrían ayudar a saber como los puedo controlar con un control de radiofrecuencia

For everything combined how much do you think this robot would cost to make?

Approx AUD$110 I reckon, if you selected one of those cheap $30 hobbyking transmitters.

What about USD?

USD? Sorry don't follow.

No idea on USD, I've bought everything in Australian Dollars. I assume you could look up all of the parts yourself and count up the cost in USD.

Can you put some instructions for the v8 Shrapnel as well as the parts list for it? I know you might thin this is not necessary but I want to build one as well as the v10 so I would like it if you put a parts list for the v8. P.S I also would like to see some pictures and a build video of the v8 Shrapnel.

The parts in V8 shrapnel are exactly the same with exception for using the M3 nylon spacers and screws in the support columns. I won't be able to take any build pictures or a build video of the V8.0 shrapnel because I always took all the components out of previous versions for the newest one. The V8.0 chassis has since been scrapped.

The only differences between V8.0 and V10.0 were the addition of the rear wedge and the changes to the support columns.

Hope this helps.

I meant to put some pictures, old ones if you have to. I just want to see the old v8. For the video you could just print another v8 chassis and just build that one

Sorry, I haven't got photos or time to make another Version 8.
It's similar enough to the later versions that you should be fine, only without the rear wedge and slots in the columns for nylon spacers. Good luck! Please post pics if you make anything, I'm always keen to see what others come up with!

I am also guessing the v11 is the exact same assembley as the v10.

Does this comply with uk antweight rules or will I need to do some resizing ? Uk rules state that it must fit in a 4 inch cube.

Yeah good point. Here in Australia, we originally tried to follow UK rules but then some of our fellow members started making larger bots after following some other advice in another state. So now we just keep to the 150 gram rule and that's it.
Shrapnel measures 5.1" long and 4" wide when assembled.
You might get lucky and your group might not enforce the size rule. We follow rule sets found on http://sparc.tools/ which don't even mention the 4" cube rule.
Good luck building! If you do make one, please put it up on the made section, I'm heaps excited to see Shrapnel built by other folks! Cheers!

I imported the stl files into sketchup and noticed that it was bigger, so I just resized it a bit and made sure that the motors and stuff would fit.

My printer ships today, so I should have it printed in the next week or so!

Ive just printed the bottom segment.

Hi, how do you power the motors and weapon motor off one battery?

I connect the battery to 3 esc's (electronic speed controls). Two esc's connect to a drive motor each to get the bot moving. The third esc connects to the weapon motor. If you're curious about the specific parts I used, have a look at the links in the description.

Is this based off of Tombstone from battle bots?

Nah, I started designing Shrapnel before I got into watching Battlebots (only recently bulk watched!).
I've since tried to distance my bot from Tombstone as much as I can. The only similarities are that it has a bar as a weapon and it has two wheels, lol.

Not accusing yeah just reminded me of Tombstone right off the bat. Neat idea though wish I thought about designing a bot on my printer. Guess there is only so many designs you can do before you have similarities with preexisting items.

Very true. Never to late to get designing tho! :)