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  1. #1

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    Need opinions on motor selection for large electric.

    I recently bought a Pilot RC Sbach 342 and I am having trouble deciding several things including which motor and how many cell a123 pack to build. The plane is 73ws and about 10lbs flying weight, I have used motor calc and the prop calc on castle creations web site and have narrowed down my decision to just a couple of motors but I want some opinions on which would be best. My first choice is a Hacker Brushless A60-5S V2 Outrunner Motor which would be way over powered but only slightly heavier than my other choices and would give me a lot extra power and according to motor calc would be a good choice. My second choice is a Hacker Brushless 2200W 300k/V would be less and less than optimal according to motor calc but still very sufficient. My third choice is aGreat Planes ElectriFly RimFire 1.60 63-62-250which was a choice because I have used Great Planes in the past and like their motors. I already have a ESC I am going to be using an Castle Creations Phoenix HV-85.

    I would also like to know how many cells should I buy to build an A123 pack I was thinking about a 8S2P packs for this plane which would give me about 15min flight time, so my normal flight of 7 minutes or so with extra for when I forget to turn on my timer.

    One last thing for now I would like to know what you think of Savox servo's I would save some money over the JR servo's I am planning on but I have heard mixed reviews on the Savox.

  2. #2

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    RE: Need opinions on motor selection for large electric.

    Your Rimfire motor is designed for higher voltages than 8S A123 (i.e. 26.4V) - the motor spec says 33-44V. In order to get 2000W (i.e. 200w/pound in a 10-ound plane), you would need 2000/26 = say 75A, which is at the top of your ESC spec and too much for the Rimfire, which will be getting red hot pretty quick during a hover.

    From the specs, either of the Hacked motors will do the job, but as I said above, you will be looking at fairly high current ratings. If your plane can carry the weight of the larger Hacker without c.g. issues, I would suggest it to allow for adequate thermal capacity. If there is any way you can up the voltage (i.e. more cells), that will help everything too. At these power levels, most people are running 9-12S lipo (say, 36-48V). At those voltages, you could also consider the Rimfire motor.

    Hope this helps...Chris

  3. #3

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    RE: Need opinions on motor selection for large electric.

    Yes Chris that helped a bunch. I was not sure about the Rimfire motor but I did forget about the high voltage rating on them and was not thinking that way, so that one is out thanks for pointing that out to me. Yes the plane can handle the hacker motor weight at 21oz's and the ESC are lighter than a 30cc gas engine and muffler which is what the instructions say to use in the plane. I can go with a larger battery I was just not sure where the weight will be to much for the CG or the plane. All other electrics I have done have been electric ready planes where the manufacture recommends the motor ESC and battery so I am learning here, and even with MotoCalc and the flight time calculator on Castle Creations web site I need some help because I don't understand everything on those sites. So what would be the best way to figure out how big of a battery I need and still get about 8 minute flight time? MotoCalc helps a bit with that but I have no idea about final weight and wing loading and other factors. I would still like to try the A123 cells simply because of charge time on those batteries over lipo's. but they are slightly heavier than lipo cells. Looking at some 30cc engines and their weight and figuring for fuel and ignition battery and comparing just motor and ESC I should have between 30 and 48 ounces before I am at the same weight as the gas combo. So a Thunder Power 6S 5000mah battery would be around 28oz's so would another battery of this size to give me a 12s 5000mah be to much weight?

    Thanks again for any help.





  4. #4

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    RE: Need opinions on motor selection for large electric.

    After rerunning some numbers I think I found a good combo but not sure. I think the Hacker Brushless A60-7S V2 Outrunner would work better than the motor I linked above with either a 10 or 12 cell battery. How much extra thrust should I have for a plane like this? Using MotoCalc and running the numbers I come up with a 10s1p battery using a 18X6 prop I would still have 260oz's of thrust with a plane at 197oz's. I understand most of this just not sure whats best.

  5. #5

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    RE: Need opinions on motor selection for large electric.



    lejongleur,

    problem posting, snail speed dialup is the pits,see next post please........


  6. #6

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    RE: Need opinions on motor selection for large electric.



    lejongleur,
    Not very knowledgeable in electric setups and was wandering if you could post your thoughts on electrifying a Bud Nosen Citabria I'm currently building. Any information would be a great help as I'm not to familiar with the electric scene although I do own a couple of small 450 size parkflyers and fly nitro and gas.The BNCitabria should comein around10.5 to 12lbs. flying weight and has a 105.5 inch wingspan, almost 9 feet. Going to use as a casual weekend flyer and not looking for superior power or 3D capabilites. I'm considering using a Rimfire 1.20 for power, http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWW0, any advice on batteries, esc and chargers would really help out. Would like to get 15 to 20 minutes of flight time if possible. Would really appreciate your thoughts on this, thanks!
    Mike





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