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Thread: Piecing together a budget heavy

  1. #11
    craig_colliass's Avatar
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    Hi

    If you decide to use the A123 batteries the configuration I use is 2 4*4 cell packs 26.4v, that way one cellpro10 charger can charge the whole 32 cells at once. (BTW I think 6s LIPo packs have a nominal voltage of 22.2v)

    The motors look OK, what material are the wheel hubs made of? I was thinking your 100Kg robot being flipped 2 meters in the air and landing on it's side the force on the hub is extremely high and may break the wheel. If you can find smaller wheels to fit you would lower the ratio of the drive and increase the pushing ability of the robot, plus reduce the likely damage to the wheels and gearboxes. that might help.

    Bike tyres are favoured by me on almost all my machines.

    I like the basic look of the 40Kg machine, it's a good place to start.

    I would advise making a machine without a working weapon first, but you can design space in the robot for one to be retro-fitted once you Have a working platform.

    Screw jack lifters do work but because they are normally so slow, in battle environments you rarely have chance to use them effectively. Cherub lifting arm can achieve maximum lift height in 1.5 seconds and sometimes that's too slow!

    Looking forward to seeing you design

    Craig
    Never Mess With THE SAINT

  2. #12
    Shakey's Avatar
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    You're right on the nominal of a 6S lipo, but the Pack I use in my feather was the one from that 40kg and at 4000mah it drops from 25.2 (full charge) to ~24.5V in a feather fight.

    The hubs appear to be aluminium, if that won't stand up to it I can probably get some go kart wheels and fix them on somehow. I was going to have the chassis have side armour for the wheels though. I'll take your advice on just getting a rolling chassis first, that'll probably be best and give me some idea of what kinda of weapon would work for me in a heavy after a bout or two

  3. #13
    blazerbotics's Avatar
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    I would say if you're not in the position to try and make a competitive one, go for something that you can have a bit of fun with. I would suggest something like that chassis you have with exposed wheels at the ends, have a big ground clearance so you can almost drive up and over other robots, it won't get stuck on walls etc, as soon as it's flipped you can drive away, and it would be a lot of fun. My new one was built for our smaller shows and designed to be as simple as possible, but its design makes it great fun to drive even though it will probably never win a fight.


  4. #14
    Shakey's Avatar
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    Managed to wedge/duct tape gimli to the wheelchair frame and use it's electronics to see how this thing runs!





    The axe was electrically and mechanically disconnected just so you know.

    The drive seems quite nice actually speedy and a lot of torque, traction is not great though. I was able to drive around for a while with me on top even on the grass (Not the smoothest of rides). This gives me some confidence that I can actually roll around the arena
    Last edited by Shakey; 5th July 2014 at 19:03.

  5. #15
    Hi, all this HW stuff is way beyond me, but all I'll say is best of luck with the build
    Really like the paint on gimli too

  6. #16
    Shakey's Avatar
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    Thanks Masher, thought I'd make it brighter so I can find it in the featherweight melees!

    How do people go about attaching a go kart wheel to a wheelchair motor? Or any other suitable wheels that might fit easily?

  7. #17
    Shakey's Avatar
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    I've had another hunt around the garage and located some suitable wheels for the robot, I'll use a short chain drive (thick chain) just so the motor isn't directly connected to the drive.

    I also have a 50mm bore 80mm stroke CO2 Ram rated for 16 bar, I thought about going the axe route with this but I'm not sure it would have enough power to be of use or self right, your thoughts?

  8. #18
    typhoon_driver's Avatar
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    Gary Cairns
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    Do the math. Work out the force the ram will provide then work out what force you will get at the end of your axe based on whatever design you have in mind

  9. #19
    Shakey's Avatar
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    That doesn't help with what I need, I know the theoretical force output at the end of the arm, but that doesn't help to know if it would just be a feeble attempt when compared to other heavies. I was wondering if any of the guys with experience with axes might know about what I should be looking for.

  10. #20
    Gabe01's Avatar
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    Force = pressure x area . I would say that your ram is on the tiny side! It's fine for a feather

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