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How to choose a motor and esc

Discussion in 'Scratchbuild Talk' started by bluebaron12, May 9, 2012.

  1. bluebaron12

    bluebaron12 Cadet

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    I have 2 RTF planes and want to start scratch building. I don't have a very high budget, but want to get a quality esc and motor. I downloaded the extra 300 from rc superpowers and am confident in my abliities. Can someone post a link or instructions on choosing a good esc and motor? That would be really helpful. My goal is to be able to build all types of planes and design my own plans.

    Thanks
    bluebaron12
  2. Choosing a good motor can be easy and difficult at the same time. There's a few things to take in consideration when choosing one for your plane:

    1- Prop size; Do you want the plane to be fast or slow? How much clearance do you have?
    2- Amps; How many amps does the motor pull? More means more power
    3- Voltage; 2s or 3s lipo? 2s would be better for smaller, lightweight planes.
    4- kv; kv determines how fast the motor spins. Generally the higher the kv, the smaller the prop
    Keep all of those in mind and you will be able to find the PERFECT motor for your plane.
    5- Thrust; How heavy will the plane be? Heavier = need for more thrust to stay airborne

    Since you're building the extra 300, I'll show you what I would do if I were picking up a motor for it.
    First, I would think about how I want it to fly. The extra is more of a slow flying aerobatic plane than anything. This tells me that I want a bigger prop and a lighter setup *keeps that in mind* ;)
    Now I go looking for the motor.. A good size prop for the extra 300 is an 8x4 or 9x5. Most motors that can take these props are in the 1000 to 1700kv range.

    Ohhey, I found a 1400kv motor:

    Specification:
    No. of cells: 3-6S
    RPM: 1450kv
    Max efficiency current: 45A-50A
    No load current: 11.1/4.6A
    Current capacity: 70A/20sec
    Internal resistance: 0.010ohm

    Max performance;
    Voltage: 3-6S
    Prop: 7x5, EDF90

    ESC: 60A
    Thrust: 1450-2300g
    Power: 1600W

    Obviously, this is a VERY high power motor. We're looking for a light setup that draws maybe about 10-15amps (This means smaller battery) Need to find something else...

    New motor:
    Brushless Outrunner Motor.

    Load Current 9A
    Kv - 1500rpm/v
    Max Load: 7A
    No Load Current: .5A
    Suggested Lipo: 3 cell 11.1v
    Thrust: 400g+
    Suggested Prop: 8x3.8

    This motor doesn't draw too much power as you can see from the max load. This means you can have a small, lightweight battery and small esc. With a 3 cell and 8x4 prop, you get a little more than 14oz of thrust- more than enough for this plane. The prop is the right size too. This is the motor I would pick hands down. Here it is http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=4859

    It'd all about finding the right balance of characteristics for what you are looking for.
    Any confusion just ask!
  3. LukeWarm

    LukeWarm Top Gun

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  4. bluebaron12

    bluebaron12 Cadet

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