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Thread: Crumbs! (And Friends) - Team Manuva's Antweight Build Log

  1. #1

    Building an antweight was always on the agenda for me, but it was put on the backburner due to upgrading Bread Dead Redemption between events. I've found myself with a bit of time on my hands and a 3D printer, so it's time to start on my new antweight!

    Introducing.... Crumbs!

    I've titled the build log "(and Friends)" because most events allow multiple robots and I will probably attempt more ambitious antweight projects in the near future to improve my CAD skills, so any other robots will be lumped in here too.


    So Crumbs consists of the following:

    • 3D printed chassis (ESun PLA+)
    • 2x N20 motors
    • 1.8A dual motor ESC from Ebay.
    • Flysky FS-RX2A Pro micro receiver
    • 2S LiPo

    The Build

    I played around with a few ideas for Crumbs, but my limited CAD skill let me down. I decided to do a test print of an antweight chassis downloaded from Thingiverse before I settled in to a designing session, just to see how everything worked and slotted together. Having a 3D model on your screen is one thing, but I learned a lot by just having a physical version to compare.

    Once I had deleted a few attempts, I fired up Sketchup and decided to make a simple 100x100x20mm wedge.


    Quite a hefty wedge at the front, all sides angled to deflect spinners. Even managed to get some motor mounts and lid supports built in. I was very proud of myself!


    Test print number 1. Printed at 50% infill to allow the wedge to have enough structure, but also hopefully flex a bit under impact.


    Small banana for scale.

    I experimented with a few different designs for wheels, but eventually settled on 24mm lego wheels. I found a hub adaptor for the N20 shaft to fit the lego tyres on Thingiverse. Works like a charm....

    ...downside is, it doesn't fit in the chassis. Back to Sketchup!

    Due to the size limitation of UK antweights having to fit in to a 100mm-ish cube, I could go up to 142mm in any dimension, providing that I don't expand the other 2. Having a preference for wide wheelbase robots, I upped the width to 130mm and tried again.

    Wide Crumbs CAD.JPG




    Size comparison with the previous chassis.

    Next was to design a lid. I wanted this to include a small block above the motor mounts to press the motors in place. The lid is 3mm, dropped in to the chassis as the posts I included in the chassis design are 17mm.

    Crumbs CAD with Lid.JPG

    Result! The lid just about fits, but with it being such a tight fit, I don't think it would stand up to impact too well if the chassis took a knock. Perhaps I should take it back 1mm or 2 in future revisions.


    And that's where we are at so far! I still need to add in a hole for the power switch and wire everything up, but at least everything fits in place. Currently weighs ~121g, so still some room left. It's a rough first draft but I have a functional antweight!

    The final plan is to make it look like a mini toaster, so I can maintain my team branding. With the extra weight I may add some stainless steel to the front and top, as I have some left over from the holes I cut in Bread Dead. The final robot will also be printed in white PLA+, with toaster slots either drawn or designed in to the lid.
    Last edited by Mr Manuva27; 18th April 2020 at 19:38.

  2. #2
    Ocracoke's Avatar
    Team Kaizen

    Looks good, well done!

    Due to the size limitation of UK antweights having to fit in to a 100mm-ish cube, I could go up to 142mm in any dimension, providing that I don't expand the other 2. Having a preference for wide wheelbase robots, I upped the width to 130mm and tried again.
    The official limit is 101.6mm or 4 inches. I tend to aim for 100mm cubed for mine to ensure it fits.
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Lafiel, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

  3. #3

  4. #4

  5. #5
    Ocracoke's Avatar
    Team Kaizen

    Thanks! I knew someone was going to bring it up haha! I've been informed that it doesn't have to go flat in the cube though, so will just wedge it in nose first .
    Hahahaa! Yeah, it is just a case of "will the robot fit in any orientation".
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Lafiel, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

  6. #6
    So a slight mishap in that I ordered the wrong reciever..... oops. After some discussion with people on Discord, it was established that it wasn't compatible with what I was trying to do. The main reason I ordered that one was because it was UK based and wasn't shipped from China. Disappointed, I decided to bite the bullet and ordered 3 Flysky FS2A receivers for delivery anywhere from late May to mid-June.

    The next day, I get a message on Discord informing me that Bristol Bot Builders had put the exact same Rx up on their store an hour ago. Typical! I couldn't believe it!

    I ordered one from BBB while I wait for the Chinese ones to arrive. With a surplus of receivers, I'll just have to build more ants!

    After some rather awkward soldering, I'm delighted to announce that Crumbs is funtional!

    The mixing is a bit wonky, but that will just be a case of switching the motor wires around.

    I'll take to fine tuning the CAD design soon for a final print. I still need to add a hole for the power switch and some walls around the wheels to prevent wires getting tangled up in them.


    Anyway, I said I'll have to build more ants, so I'll share my next plan with you. I never want to set out to build a "boring" robot, and Crumbs is certainly heading towards that way. It's a first attempt at CAD, so I suppose it is ok, but I want something more extravagant for the next one.

    So, I'm introducing plans for "The Walking Bread". I wanted to do this at Beetle level, but Antweights are AFAIK the only weight class remaining that has a weight bonus for shufflers, with the exception of a few competitions.

    I'm basing the design from Mike Franklin's series 6 robot Anarchy, the most successful shuffler in Robot Wars history and one of my favourite robots of the original series. This could be achieved with my 3D printer and would give me 225g, allowing me to focus on adding a powerful weapon like a brushless spinner.

    Anarchy uses 2 banks of 4 cam gears driven by chains to move the legs, which may be a bit much for an ant. Looking at the mechanism for Scuttle, the Technogames predecessor to Anarchy, I think it is run from one motor, with a set of smaller gears driving the bottom bank of cams. As far as I can see, the top bank is unpowered.

    So at the moment I'm in two minds. I either copy Scuttle and end up with many small gears (See below draft), or I utilise a pulley system along the bottom bank with 3D printer timing belts. The pulleys would be easier to design and print, but may be heavier and less durable.


    It's definitely going to be a challenge. I'm still working all the details out, but I've posted it now. I have to follow through with it.

    If you have any ideas of feedback, please let me know!

  7. #7
    Ocracoke's Avatar
    Team Kaizen

    Looks good, well done so far. Receivers I find can be a bit fiddly but then again, I tend to stick with DSMX. Lemons I find work best with the OrangeRX transmitter I have. I think the gear system on a walkker could work but it would be awfully exposed to weaponry, you may need to layer it like Anarchy. Bonus points for kudos though.
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Lafiel, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

  8. #8
    First of all, 10/10 for naming it The Walking Bread

    You're right with Scuttle, only one motor driving each side. The motor pinion drives the middle small gear which in turn drives the bottom row which is then geared to the top. I've attached a couple of pictures of it I took at RoboNerd 2018; there's very little inside it! While timing pulleys may be the easier option, there's more chance of a belt slipping or similar, which would knock the walking gait right out of sync and you could end up with legs that move but don't propel you anywhere. With properly meshed gears, once you've set up all the legs in their positions, they won't go out of sync. Just for reference, Scuttle's legs are set 90 degrees apart in the gearing so only has one foot on the ground per side at any one time, whereas Anarchy has 180 degree spacing so has two feet on the ground per side.

    scuttle.jpg scuttle 2.jpg

  9. #9

  10. #10
    I've attached a couple of pictures of it I took at RoboNerd 2018
    Jamie, you absolute hero! I was struggling quite a bit with that, that helps out massively. Thank you very much for the info!



    Thank you for all the kind words, everybody. I'm afraid I haven't started the shuffler yet, but I have been focusing on making Crumbs a bit more interesting than just a wedge. I wasn't happy with how cramped it was inside the bot and wanted to make space for a servo so I could incorporate a lifter. I wasn't too happy about it, but I tried moving the wheels to the outside.

    Crumbs MK2.JPG Crumbs Modified CAD.JPG

    This new design incorporated new individual motor mounts, plus mounting posts in the back panel and lid for a power switch. Print time!


    Ok, so:


    • Motor mounts fit perfectly


    • Wheel gaps are too tight and exposed
    • Not much extra space
    • Print quality is awful.
    • I absolutely hate it.

    After a few days of swearing at SketchUp, I came to the conclusion that I had lost all sight of what was good and bad within the project, so I scrapped it and started again.

    The following result was an improvement:

    Crumbs mk3.JPG

    Finally, some steps in the right direction! Can we guess what the next steps are?



    ..If you guessed "Scrap it again and start learning a different CAD software", you would be absolutely right!

    Yes, I downloaded Fusion360. I initially used SketchUp from it being the only free software I knew of, but when I was told that Fusion was free for hobbyists, I signed up immediately. It took a day or two to get used to, but over the course of the weekend I ended up with the below:


    Much better. This design includes enough space for all the electronics, plus a servo. With the layout of the design, the servo gear can be used to drive a lifter, axe or grabber, depending on which opponent I am fighting.


    Above: first test print. Below: Weigh in with all electronics fitted.


    Still not quite there yet, it still needs a lid and a weapon. The chassis itself needs a few tweaks too, like lowering the walls of the motor mounts and including posts for screws, power switch, etc. With only 22g remaining, I may be a bit pushed for weight, but hopefully I can work around that.

    All in all, very pleased with how it is going!

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