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Thread: YorkNott Robotics: Shuriken (FW spinner)

  1. #1
    Danny B's Avatar
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    Hi all!

    I'm starting up this thread as I begin work towards my new featherweight, Shuriken. Since this is my first time building a spinner, I thought it best to try it in FW scale first as a proof of concept, so I can ultimately work my way up to a heavyweight version, Samurai.

    Despite this being a new thread, I have been planning and tweaking this design for a while. Having followed a few other threads, I think I have some basic aspects and a general layout clear in my mind.

    • HDPE chassis (20mm sides, 8mm top/base, reinforced with aluminium in key areas)
    • Drivetrain: 2x Gimson GR-EP-45 gearmotors
    • Weapon: 500 x 60 x 15mm Hardox 500 spinning bar, weight 3.6kg, angled forward approx. 25 degrees
    • Weapon motor: Turnigy Rotomax 50cc brushless
    • Power source: 1x 4000mah 4s lipo for drive, 2x 5000mah 5s lipos in series for weapon


    This is going to take a while, certainly I won't start buying parts until the end of summer, but at least by then I should have a finalised design. If anyone has any advice to offer, feel free. I need as much help as I can get!

  2. #2
    R9000's Avatar
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    Rory Charlesworth
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    Wowsers... a 50cc brushless for the weapon?! I mean, sure, if you can make it work and stay underweight, it just seems a little like overkill to me. Maybe I'm wrong though, I certainly don't have experience with spinners. So is this going to be an NST-esque machine, or were you thinking of a different shape?

  3. #3
    Danny B's Avatar
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    More like a cross between Ironside 3 and Ghost Raptor, but smaller.

  4. #4
    R9000's Avatar
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    Ahh so it's an overhead bar. Sounds mean.

  5. #5
    overkill's Avatar
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    Angled blades like that have serious disadvantages: hitting on the down-stoke will tend to flip your own bot and its difficult to add self-righting to an overhead spinner. The tilt on the blade will give the bot some gyroscopic precession (gyro dancing) and the bot's steering will suffer. If you want a more effective horizontal bar spinner, go for an undercutter; its harder to defend against and eliminates both those issues.

  6. #6
    Danny B's Avatar
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    UPDATE

    So after some thought, I've decided to change the design to a more conventional, NST-esque setup. I'm still keeping the weapon bar the same size and weight, and using the same electronics and drive/weapon motors.

    Going by the size, power and relatively low kv of this motor, I reckon it has some impressive torque behind it, but I still want to reduce the speed by 1.5:1 just to be safe. Accounting for a 5-10% reduction in speed due to mechanical and aerodynamic drag, I estimated the bar's tip speed should be around 230-240 mph.
    Given the reasonably substantial weight of 3.6kg, will that be enough kinetic energy to cause any damage?
    Last edited by Danny B; 26th June 2017 at 20:33.

  7. #7
    Andy's Avatar
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    Andy Russell
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    It'll do more than "cause any damage" if you get that working mate, it'll be deadly as hell

    Signed up for the FW champs in august with it?

  8. #8
    overkill's Avatar
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    I worked out the kinetic energy using the Cosmos on-line calculator. From my own horizontal spinner experience, you will probably see up to 15% speed loss from air resistance, friction, voltage sag, etc. With the 1.5:1 reduction, that makes the worst-case speed 3,606 RPM:



    5.3KJ will cause extreme damage and if you got the efficiency up to 95%, it would be 6.65KJ

  9. #9
    Danny B's Avatar
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    Quote Originally Posted by Andy View Post
    Signed up for the FW champs in august with it?
    Not a chance, won't have enough money to even start buying bits until the end of summer! XP

    Nah, this one will definitely be for next year instead. If Extreme Robots ever end up allowing spinners, I might try my chances there first. If not, then I'll just have to take it out on some old household junk instead

  10. #10
    Danny B's Avatar
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    Quote Originally Posted by overkill View Post
    I worked out the kinetic energy using the Cosmos on-line calculator. From my own horizontal spinner experience, you will probably see up to 15% speed loss from air resistance, friction, voltage sag, etc. With the 1.5:1 reduction, that makes the worst-case speed 3,606 RPM:

    5.3KJ will cause extreme damage and if you got the efficiency up to 95%, it would be 6.65KJ
    Thanks for the info, that's a really handy tool you've found there. Now I'm much more confident about the effectiveness of this setup!

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