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Thread: Numa V2 - Quad Mech

  1. #1
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    Numa V2 - Quad Mech

    I'm working on a new quad. No random inspirations, so it's simply Numa V2. I've been working on this very sparingly since November 2016. It's a long shot whether I'll finish this in the next 2 months, with work being busy, plus a fine girlfriend to keep me busy on the weekends too. (ahh, the anti-social days past of grad school when I built Numa, Twitch, and TwitchMX...)

    The big thing I wanted to do differently is to try out MicroPython. There's a bunch of boards out there. The one that I found first that seemed to have what I wanted (lots of breakout pins, specifically; and lots of UARTs and smaller than the Axon) is the HydraBus. I got it for cheap, too; probably thanks to clearing inventory of the V1.1 board on Amazon.

    The other new thing, which I actually started first, back in November, is my adaptation of the R-Team "auto-cannon" auto-BB-loader. I made a janky prototype, with a Pololu Micro metal gearmotor controlled by an Axon Mote PWM'ing a Pololu VN5019 breakout. Bunch of pictures of that attached.

    Now for the horrifying part... Code? I'm manually converting Numa's C code to the Python3-like Micropython and its libraries. Fortunately the hard parts of the code that I've always depended on others to do is already done by the Hyland brothers (namely libaries like AX-12 control):
    - https://github.com/dhylands/bioloid3
    - https://github.com/JonHylands/roz (mainly serves as an example that uses bioloid3 library)

    Last night, I finally got rid of all the tracebacks in my code (tedious because I debug by running the code, rather than at least compiling first; I really need to set up the linux version of MicroPython for quicker testing, I think), and had it running the main loop.

    Tonight, I hooked up the XBee and Numa's old turret servos, and voila, they move with my Arbotix Commander! (Though somehow I ended up swapping the pan and tilt servos in code )


    The other changes:
    - Bigger base, so score panels fit between leg servos
    - Probably 3DoF per leg isntead of 4
    - Two levels of body; much lighter turret design once I start working on that.
    - Going to modify my servos like I'm an R-Team member ... except I bought copper because I forgot that aluminum actually has higher thermal conductivity. Oh well $10 mistake.
    - I'll stick to hand-cutting my carbon fiber base plates this time; water jetting took two months last time.

    A bunch of pictures... from last year, before I'd decided on the Hydrabus. The prototype hopper uses old spare chassis plates that were made for the original Numa, as well as 3D printed parts of course. Hopefully on the next iteration, I fully resolve any jamming issues :|

    Click to embiggen!
    Click image for larger version. 

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    I recently realized I probably shouldn't pipe the BBs out the center-back of the robot, as then the tube sligthly blocks the score panels.

  2. #2
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    Re: Numa V2 - Quad Mech

    Nice turret. Smooth action. Your carbon fiber parts look great.

  3. #3

    Re: Numa V2 - Quad Mech

    Looking good! Let's see which one of us finishes first :-)

  4. #4
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    Re: Numa V2 - Quad Mech

    I should mention that none of the parts shown are final parts. They're all scraps/old parts. So I have a *lot* of work to do.

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    Re: Numa V2 - Quad Mech

    Quote Originally Posted by Gertlex View Post
    - Going to modify my servos like I'm an R-Team member ... except I bought copper because I forgot that aluminum actually has higher thermal conductivity. Oh well $10 mistake.
    Eh? Depends on the specific blend, but copper (not brass or bronze allows) almost always has both thermal and electrical conductivities higher than aluminum. The big reason copper is used in heat blocks is its high heat capacity, so it is slower to change temperature due to sudden fluctuations in heat input/output while still having thermal conductivity at least as good as aluminum.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  6. #6

    Re: Numa V2 - Quad Mech

    I think the point is that the difference between copper and aluminum are not that big (aluminum is almost as good a conductor of heat and electricity as copper) but the weight and price differences are bigger than that.

  7. #7
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    Re: Numa V2 - Quad Mech

    I'm pretty close to building things now. I will have to use the original Numa's legs, rpobably, as I don't foresee having time to make new legs. I am regretting disassembling those legs preemptively :| .
    Click image for larger version. 

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  8. #8

    Re: Numa V2 - Quad Mech

    The dual layer design seems quite popular! I've tried to avoid it because I want a lower center of gravity, but having narrow hips is very important.

  9. #9
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    Re: Numa V2 - Quad Mech

    Cut out the top and middle plates Sunday! A few holes were forgotten or needed to be enlarged. Currently, my big mechanical iffy points are the ammo loader and the interface between spiral tubing and BB feed tubes. Doing lots of playing with objects to get a sense of what I want to contrive and print. My prototyping from the end of last year still had some issue with jamming, though did not use the best components, either.

    Quote Originally Posted by jwatte View Post
    The dual layer design seems quite popular! I've tried to avoid it because I want a lower center of gravity, but having narrow hips is very important.
    Given the legs I'm using, I've got plenty of height for a second layer of components below where the coax servos are mounted.

    Though your comment did make me consider moving the battery to the bottom front of the robot, but I probably won't do that.

  10. #10

    Re: Numa V2 - Quad Mech

    Is yaw for the turret driven directly by a servo, or by some kind of linkage?

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