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Thread: Deathly Hallows - Beetle - Evil K'Weevil

  1. #1
    Ladies and Gentlemen,

    I am proud to announce the build thread for my first combat bot.
    The text bed featherweight robot went really well and was completed to rolling powered chassis in record time. With this accomplished I can now move on to designing a combat bot and a beetle seems a good place to start. So without further a do I introduce.....

    Evil K'Weevil

    Who will have the following characteristics:
    Two wheel drive
    HDPE sub-frame
    Bolt on Metal armour (type tbc)
    Any way up operation
    Drill engine driven combination coring and flip weapon

    Been playing in OnShape and hope to have some rough designs to share by end of this week.

  2. #2
    Quote Originally Posted by Deathly Hallows View Post
    Drill engine driven combination coring and flip weapon
    This sounds very interesting. Could you explain a bit about what your plans are?

  3. #3
    A picture says a thousand words
    The front face is missing (as are the wheel, internals and some sub structure), from which the weapon protrudes, positioned centrally.

    Evil K'Weevil Empty Shell.png

  4. #4
    Keeping weight under 1.5Kg is going to be a lot harder than I thought. The mass calculations in the OnShape CAD very quickly highlighted that the initial design was not viable without some radical rework. So bulk heads will have to be lightened. I am still working on the idea of using those 12.7mm thick Bonzer Chopping Boards for these components, as they are such good value; but I may have to go thinner.

    Bulkhead.png
    The idea remains to build a sub-frame to bolt armour on to the outside and to fix the internal parts to. M5 counter sunk bolts should suffice to hold the structure together. Well back to the CAD for me...

  5. #5
    I reworked the design again. However it seems to me that the way forward is to resolve the internals first, then I can build a box they fit inside. I can rework the chassis ad infinitum without moving forward so I need some help.


    Drive motors are for a 1.5KG robot so I don't need a lot of power. Would something like 12V Pololu 75:1 be enough? I was looking for something a bit more torque but find it hard to find anything under 100g seems to be a jump from these 10-30g units to 150-250g units


    Hubs to fit


    Wheels very dependent on matching wheels to chassis height I want big wheel just clearing floor and roof for anyway up driving.


    If it was the mentioned motors I could get away with a pretty small ESC but these 20A Turnigy are cheap and light.


    Want to ensure I can save some weight for weapon motor and armour

    Appreciate any feedback

  6. #6
    Ocracoke's Avatar
    Team Kaizen

    The speed controllers won't work for this application if it is for the drive - the advert states they do not have reverse. I'd possibly also say the motors are too small though I'll leave that one for someone with better BW experience to call it - I had originally planned to use a similar type of motor in my Beetleweight but they are not powerful enough (though they were 6v 298:1 motors!).
    Team Kaizen - Build Diary for all the robots

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

  7. #7
    Damn it - must have been half asleep. <EDIT - still asleep the ESC has no reverse! >

    I found these rough looking units on ebay no mention of reverse but the advised applications would require it. <here>

    But these sound better on robotshop <here> a week or so till in stock but no rush. Decent torque for size and at 82g well under 100g target.

    <EDIT - then the speed controller must be different - I found this one but no brake here
    This one here but no BEC which I could work around using the weapon ESC or a separate BEC unit. or perhaps I should re-purpose my Sabertooth 2x12A RC for the job. But was saving that for by test bed.>
    Last edited by Deathly Hallows; 15th November 2017 at 12:31. Reason: misread prior message

  8. #8
    quick question, your beetleweight it looks like it is gonna be a ram bot why not design as much as you can, see how much it all weights then fill the rest of that budget with motors and gearboxes. nearly every bot ever made starts out over weight so you can always thin out some armour here or there or run a smaller battery

  9. #9
    Thanks for your input. It won't be a ram bot, but if drives are good that will be fine attack too. The intent is for something a little different. I want to get further into the design before sharing too much about weapon system. The weapon system, chassis and armour will require a lot of the available mass, the drive and wheels will dictate the dimensions. I've probably over complicated it but I am nearing a solution I think.

  10. #10
    fair enough. just had another idea that you could use a brushless drive similar to speed 900 setup use by a load of people.

    make me kinda want to design one.........

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