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Thread: Attitude Adjuster (Beetleweight)

  1. #1
    Inspired by going to the filming of S1 and S3 of the Robot Wars reboot, my friend and I have decided to each build a beetleweight robot and are aiming to complete them in time for the Euro championships.

    I want something that's more interesting than a box on wheels and I've always liked hammer/axe bots like Terrorhurtz, Beta and Mega Melvin so I've decided to design and build one of those. I know they're not super effective at the lower weight classes, but that suits me as I want something that isn't a scary spinner for my first build.

    After reading all of the build threads in here (and being particularly inspired by the detailed build diary for This Is Not A Drill, amongst others), over the last few weeks and months I've been gathering bits and learning to CAD on Fusion 360. I used to "build" vapour bots in CAD back in the days of Series 5-7, so it is all coming back. I have also joined a local hackerspace, so I have access to a workspace with suitable tools for making a beetleweight.

    This is the design I have so far. It's still WIP as I think there is some wasted space, and it is pretty close to the weight limit so I'll need to lighten it somehow.

    attitude_adjuster_v2_2018-Apr-04_09-44-41PM-000_CustomizedView20567221937.png attitude_adjuster_v2_2018-Apr-04_11-19-42PM-000_CustomizedView40449509705.png

    The bulkheads are 10mm HDPE, the wheelguards and rear are 5mm HDPE, the top and bottom are 2mm polycarb and the wedge is 1.2mm Grade 5 titanium.

    It's driven by 2 of the standard 1000rpm motors, with a 3S 1000mAh Hobbyking lipo and a Sabertooth 2x12A ESC.

    The axe is 10mm square aluminium 6061 bar, with a 2mm Grade 5 titanium axe head. It's currently powered by another 1000rpm motor geared down by a toothed belt at ~2.5:1. I think that probably needs to be changed though, it's too fast for an axe and I don't think it will have enough torque to self right. I was thinking about either a 37mm 500rpm gearmotor I have lying around, or possibly even going brushless for the weight/size reduction. The only doubts I have about brushless are that I'm not sure what motor to use or whether that's too ambitious for a first build?

    Ebay has been my friend for this, I picked up a second hand DX6i, all the random bits of metal, a Chinese car ESC for messing around with and all the screws.

    I've made a test bot made of some eBay motor mounts and a bit of polycarb that I can go chasing the cat with to prove that I can actually build a robot and wire it.

    IMG_9592.jpg

    I've also built a test axe platform using an old chopping board I had lying around. The cat REALLY doesn't like that.

    IMG_9585.jpg

    And finally a bit of CAD (cardboard aided design) to check that everything is a sensible scale.

    IMG_9584.jpg

    The most important part is thinking of a good name, which I am rubbish at. I decided to take inspiration from the ships of Iain Banks' Culture series of books, and the one that jumped out at me was "Attitude Adjuster", so I went for that.

    As soon as I finish the CAD design to a "good enough" standard then I'll be able to start building! Any comments/feedback on my design so far? In particular I'm interested in feedback on the weapon, on electronics/brushless motors, and whether I'm doing anything stupid.
    Last edited by scott; 4th April 2018 at 23:27.

  2. #2
    Andy's Avatar
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    Andy Russell
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    Awesome work, will be nice to have more weapons like axes in the beetle class, i've always wanted to make one myself but ended up going with spinners

  3. #3
    Thanks man! Ask Aaron seems to think that axes are ineffective in the insect weight classes, but we'll see how it goes

  4. #4
    Ocracoke's Avatar
    Team Kaizen

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    Anything can be effective with enough force and sharpness I am looking forwards to seeing this at the European Championships.
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
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  5. #5
    Deathly Hallows's Avatar
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    Simon Hallows
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    Sounds really good Scott. The internals sound similar to my Evil K'Weevil.

  6. #6
    It's been a while since my last update, life got in the way which meant I didn't have much time for robot fun, beyond terrorising the cat with my test platform.

    I've been refining my design to optimise it for weight, until I realised that in my spreadsheet of component weights I had the fingertech wheel hubs as 70g each instead of 7g! So with that sorted, I decided to start making bits of plastic smaller.

    IMG_9728.jpg

    I have a sheet of 10mm HDPE and a sheet of 5mm. So far I've made the sides, the front and the rear bulkheads. I was using the table saw and chop saw in the hackerspace for the first time, so I used an old plywood cupboard door that I had lying around to practice on.

    IMG_9727.jpg

    Some of my images have uploaded sideways :/ With plywood bot done, I moved onto chopping up the HDPE. I made it slightly too tall by a couple of millimetres, so I will look into taking that off using a plane next time I'm in the hackerspace.

    parts.jpgIMG_9731.jpg

    I'm not totally sure how to connect the rear to the sides. I'll probably use long wood screws to connect the front to the sides, but for the rear I want to also attach the wheelguards using the same bolt. I used a spare bit of HDPE to test out my idea for using threaded inserts to make them removable, however I'm not sure if there's enough on each side for them to bite into, what do you guys reckon? I'm planning to make some threaded bar out of aluminium for the wedge and the top and bottom plates, possibly with an o-ring for some ghetto shock mounting.

    IMG_9732.jpg

    Over the last few weeks I've been learning how to machine aluminium using the small metal milling machine at the hackerspace. You can see below my attempt at making a bit of 2mm aluminium into a square (ignore the bit where I broke a drill bit...). It's satisfying when it turns out more or less how it was designed in CAD!

    motor mount.jpgDrivetrain_V2_2018-Apr-29_09-26-43PM-000_CustomizedView31606388638.png

    Next job is to get the edges of the parts brought and then to get some holes drilled so I can mount the motors in the side bulkheads, hopefully I will get to that in the next week or two.
    Last edited by scott; 29th April 2018 at 22:09.

  7. #7
    Small update - I needed to shave a few mm off my pieces of HDPE and remove the saw marks, so I used a hand plane, which worked pretty well. I now have some pieces of HDPE that are roughly the same height and the right length. Next step is to make a template for the holes I need to make for mounting and motors, which I'll laser cut in some MDF.

    IMG_9791.jpgIMG_9790.jpg

    Before I can start on weapon construction I need to finalise the design. I've already bitten the bullet and finalised the dimensions of the robot as a whole (LxW 17.5x20cm), but I'm still not 100% on the battery placement, which affects the construction of the weapon bulkheads and the distance between them. I had them right next to the weapon motor in the initial CAD, but I think that it is too close to the weapon wires. I can't make the body wider as it is already too wide, and my piece of Grade 5 titanium is 20.2cm wide.

    I'm thinking of making a battery box to be mounted to the weapon bulkheads, sideways so it doesn't interfere with the weapon belt. Is the design/idea in the second image too complex or vulnerable? The plan would be for it to be protected by two layers of 3mm polycarb, and for it to be easily removable for serviceability.

    Screen Shot 2018-05-11 at 14.05.13.pngScreen Shot 2018-05-11 at 14.04.45.jpg

  8. #8
    Ocracoke's Avatar
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    Looks OK to me, if a bit tight to the motor. Worth experimenting with the orientation of the battery so it is vertically mounted in the robot rather than horizontally? Looks like it is coming on well though
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
    MW: Kaizen (Build Thread)

  9. #9
    Thanks for the words of encouragement! Good idea, when I have a rolling chassis up and running I'll check out having it vertically before making a final decision, my hesitation was that it would be tight to the top of the chassis, as the chassis is 35mm tall and the battery is 33mm.

  10. #10
    Ocracoke's Avatar
    Team Kaizen

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    Weapons that go through the top of robots in the BW category are comparatively rare compared to the side. However, I wouldn't be comfortable with that much clearance either (though says me, my Beetleweight's batteries are pressed up against the rear panel :S).
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
    MW: Kaizen (Build Thread)

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