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Discussion in 'Electric Propulsion' started by emir_82, Jul 22, 2019.

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  1. Jul 22, 2019 #1

    emir_82

    emir_82

    emir_82

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    Hi everyone,

    I made this thread to compile the electric drive projects of this forum users.

    My current project is a retrofitable electric self launching system for sailplanes.

    instagram.com/grasshoppersystem

    In the near future i'll starting to manufacture our own motors too.

    Regards
     
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  2. Sep 26, 2019 #2

    Bille Floyd

    Bille Floyd

    Bille Floyd

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    My first post here :

    I fly a rigid-wing , carbon hang glider , with spoilers
    for turning and a flap for glide control ; it weighs
    100Lb, and i foot launch it with two fake legs and
    a 8kt breeze.

    This coming year i want to get rid of the pilot down
    tubes and control wires ; fit it all in a pod that's
    centered in the wing with a 15Kw E-motor, with
    a pusher prop that folds , (and a wheel) or two.

    I get 17:1 L/d claimed, (15:1 actual) , now ; podded
    up i should match a sgs 1-26, at a 45mph best glide
    speed. I "Want" 3 good climbs out of the battery
    to catch a thermal, kill the motor and fold the prop
    and soar away.

    Bille

    This is me at Torrey pines , San Diego :
     

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  3. Sep 27, 2019 #3

    BJC

    BJC

    BJC

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    Welcome to HBA, Billie.

    Consider opening a build log here, and post lots of photos.


    BJC
     
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  4. Sep 27, 2019 #4

    emir_82

    emir_82

    emir_82

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    Bille,

    Nice project!
    If you still have 15:1 glide ratio at 45mph and assuming 320lbs of total weight you will need a little less than 4kW of electric power (that includes the efficiency loss of battery, controller, motor and propeller) to maintain level flight, so with 10kw you will get a decent climb.
    15kW motor will be overkill, but is better to have spare power just in case the maths didn't help at first and the weight difference is very low. Price not so much.

    The battery pack will be a little more difficult to design to keep weight low and range high.

    Did you start picking the parts yet?

    Regards
     
  5. Sep 27, 2019 #5

    Bille Floyd

    Bille Floyd

    Bille Floyd

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    The Exxtacy Hg is old ; but built like a Tank !
    Fully cantilevered wing , (no wires or struts needed)
    in this carbon honeycomb D-tube , with carbon ribs.
    It's a tandem HG good for 160Kg , (358Lb) payload.

    I weigh 205 of that 358Lb it's good for ; so i
    can add 153Lb of weight and still stay inside
    the placard limitations , with a VNE of 58mph.
    The wing is already 100Lb ; so i can use all the
    153, (for power & pod), that it's weight limitation is
    good for, and stay legal under 254 Lb. The more
    weight i put on her ; the higher the, "Speed" i get
    my best L/D at .

    When i put the pilot in the pod , and get rid
    of the control-frame & wires ; i fully expect
    that 15:1 or 17:1 L/D, to go up to near 20 to 22:1 L/D.

    I want 15Kw power because i plan to do most
    my flying at King Mt Idaho ; mountain peaks are
    12K' ASL , and take-off is at 5,500' ASL. Seriously
    i think i might NEED a variable pitch prop , to
    clear a 12K' ASL Mt , with some reasonable degree
    of success ; even 15Kw power ?? !

    BTW - Not a lot of options for reliable, and well made
    electric motors , (not like gas engines) ; but i hope
    something fits my needs a year from now because
    that is how long it will take me to build and test-fly
    the pod i wanna use. I'm OK at mold making, and
    general composite lamination's. I am not an engineer
    but can copy and shape stuff , rather well.

    Bille
     
  6. Sep 28, 2019 #6

    emir_82

    emir_82

    emir_82

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    Bille,

    Electric motors does not loose power with altitude because don't need oxygen.
    The propeller does lose some power but is not much a problem.
    If you are using it only to climb you can set the pitch of the blade for that mission, there is no need of variable pitch.
    I dont know if there is a folding and variable pitch propeller in the market. Featherig and variable pitch propeller is more easy to find.
    I'll recommend a fixed pitch foldable propeller because they are less expensive and there is a lot of project around with those.

    The electric motors are reliable even the Chinese (some brands). The weakest link is the controller.

    How many ft you want to climb in total with the motor?
     
  7. Sep 28, 2019 #7

    Bille Floyd

    Bille Floyd

    Bille Floyd

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    I keep forgetting about how E-motors don't loose power
    like the gas engines do , at altitude.

    I would say on a good day ; a 500 to 800ft gain , would be
    enough to hook into a good thermal. Having power while
    searching for a thermal ; that would be a major bonus !

    Your right about the folding prop ; for my needs , it's
    the way to go.

    Has anyone here , ever dealt with this company :

    https://www.geigerengineering.de/avionik/produkte

    Bille
     

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