Need help with a competition

Discussion in 'First Build' started by RedGuy, Mar 11, 2018.

  1. RedGuy

    RedGuy New Member

    Hey everyone, I've got a dilemma. I'm in a quad-copter competition and the specifications look very odd.
    b. Rotors
    i.Maximum length (tip to tip) = 6 in.
    ii.Metallic materials are not permitted.
    iii.Rotors must not be sharpened to a point.
    c. Motors
    i. Maximum angular speed at rated voltage (no load) = 7200 rpm.
    ii. Maximum propeller to motor gear ratio = 5.
    d. Power:
    i. Maximum output voltage = 24 V.
    ii. Maximum capacity = 2400 mAh.

    Simply, with those rotor sizes and that maximum RPM, we don't see any way to get lift on this. Gearing is not an option for my team. We have a 250 quad kit with a 2 cell battery, 920kv motors (aprox. 6600 RPM), and 5-inch 6-bladed props and we get no liftoff. Some insight would be greatly appreciated! This is for the Science Olympiad Quadrotor event.
     
  2. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    Is it required to be a "quad"copter? Also, I'd suggest higher voltage low KV motors and a lot more surface area on the prop if you want to get off the ground. Do the propellors need to have 2 blades?
     
  3. RedGuy

    RedGuy New Member

    Unfortunately yes, it does have to be a quad. So more depth on the blades? And it can be as many blades as we want, we currently have 6 blades. Would 6x4x3 work?
     
  4. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    You are going to need lightweight materials, here is a 3DP prop designed for low RPM

    https://www.thingiverse.com/thing:264438

    It doesn't look like it would fly IMHO, but you might increase the surface area and make it lighter. Take a look at microfilm aircraft as well.
     
  5. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    Take a look at this video for some ideas as well.
     
    mozquito1 likes this.
  6. mozquito1

    mozquito1 Well-Known Member

    Good find. He had another post & I said it would have to be like matchsticks.
    O r maybe I forgot to post the reply.
    But I would like to see the frame you have. Or as it is. He can't max them specs put & expect it to run.
    What is the purpose, race or lightest flying build.?
    Does it have to be 250mm Base.
    2S & the rpm is achievable with smaller motors. I just don't get why the weight to power difference. How long does it need to fly or how far.
     
    GJH105775 likes this.
  7. David Beckham

    David Beckham New Member

    [​IMG] The competition is the Florida Science Olympiad. The Rules are fairly restrictive. The quad and all spare parts have to fit inside of an 18x18x18 box. We chose 250 becuase it seem like the right size. We removed top and bottom plate and have everything mounted on a single frame plate. The competition involves flying through an obstacle course like a box tunnel, over-under a pvc box and past a box fan and tunnel. Total flight time would be 5 minutes or less. Also, there is a second part called rescue where you have to pick up objects. That is a little more concerning given our weight issue already. We are considering a gear box of some kind, but given we have 2 weeks before competition, I am not sure anything could be fabricated in time. We can't find an already made system that would work. It has to be built by the team in order to qualify. Any ideas out there would be welcomed. Thank you.
     
    Last edited: Mar 13, 2018
  8. mozquito1

    mozquito1 Well-Known Member

    What type of lifting mechanism. This is a hard one. Without some mad prop & the skinnier build I can't see this happening with a lifting jig on a 2S lipo for 5 min.
    I suppose this is why it's a comp..
    Without testing different stuff out, it's hard. Your basically trying to fly with 4 drill motors, no load 7200rpm.
    Sorry but good luck & keep us posted please.
     

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