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  1. #1

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    Old Crow 1100mm 11.1v UPGRADE

    Hello, I recently purchased the Durafly Old Crow P-51 1100mm. It is a nice flying plane and has the scale looking 4 bladed prop. I know that might hinder the performance a bit but I would really like to keep it. The recommended battery is an 11.1v. I'm pretty new to electrics so I don't know all of the tricks, do's and don'ts yet.

    If I am flying the plane with an 11.1v 20C battery, will going to a higher C rating make the plane faster ?

    I have heard some guys talk about going to the next size up battery. What is the best way to find out if a motor and ESC can handle going from a 3S 11.1v to a 4S 14.8v ? Thanks , Dil

  2. #2
    Moderator aeajr's Avatar
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    Your questions, and ones you have not yet asked are answered in this free on-line book.

    EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT

    http://www.rcuniverse.com/forum/m_7100376/tm.htm


    But some quick answers:

    Going to a higher C rated battery might make the plane faster if the battery pack in the plane now is not up to the load that is being placed upon it.

    The best way to understand if you can go to a 4S pack would be to read the instructions for the motor and ESC you are using. There is a chance that if you go from 3S to 4S you may have to go to a smaller prop.

    Read the book at the link and all will be revealed.
    Long Island Silent Flyers
    www.lisf.org
    Eastern Soaring League
    www.flyesl.com

  3. #3

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    Lots of good information on that link so Thanks for that. However, my brain is having some difficulty trying to grasp all of the info so I'll ask a more specific question:
    Will the motor that comes installed in the DuraFly1100mm Old Crow P-51 handle a 70 amp ESC and a 14.8v battery ?
    I have purchased the same 70amp ESC that RocHobby/ FMS use in the P-51 Strega.

    I tried contacting DuraFly through their website but they have an issue with their contact page and it keeps giving an error message. The only info/specs I can find on the Durafly web page is that the motor is a 750KV Brushless Outrunner, part # 142000141 and it shows 16V. Does that mean the motor will handle up to 16V ? Any help is appreciated, Dil Brandow
    PS there are no motor specs in any of the literature supplied with the plane and nothing on the motor itself.
    Last edited by superchargedill; 05-29-2014 at 06:33 PM.

  4. #4
    Moderator aeajr's Avatar
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    [QUOTE=superchargedill;11813770] Lots of good information on that link so Thanks for that. However, my brain is having some difficulty trying to grasp all of the info so I'll ask a more specific question:
    Will the motor that comes installed in the DuraFly1100mm Old Crow P-51 handle a 70 amp ESC and a 14.8v battery ?
    I have purchased the same 70amp ESC that RocHobby/ FMS use in the P-51 Strega.

    You can put any size ESC you want on the motor. The motor doesn't care. BUT the motor will pull a certain number of amps based on what prop you put on it. So if you put a 10 amp ESC on the motor and it pulls 20 amps the ESC will burn up. If it pulls 20 amps and you put a 50 amp ESC, no problem. If you put a 70 amp ESC, no problem but no change in the performance of the motor either.

    Will the motor handle 14.8 V? I don't know. Would need the specs on the motor.

    If I had a link to the plane so I could read the specs I might be able to help you.

    I did some searching and found this article but it provides no info to answer your questions.
    http://www.flyrc.com/durafly-p-51-old-crow-1100mm-pnf/





    Quote Originally Posted by superchargedill View Post
    I tried contacting DuraFly through their website but they have an issue with their contact page and it keeps giving an error message. The only info/specs I can find on the Durafly web page is that the motor is a 750KV Brushless Outrunner, part # 142000141 and it shows 16V. Does that mean the motor will handle up to 16V ? Any help is appreciated, Dil Brandow
    PS there are no motor specs in any of the literature supplied with the plane and nothing on the motor itself.
    If you say the spec is 16 volts than it should be able to handle 16 Volts, but not necessarily with the prop you are using.

    And we have no idea what the amp rating is on the motor but it is likely less than 35 amps because the ESC that comes with it is a 35 amp ESC.

    Without the specs we can tell very little.
    Long Island Silent Flyers
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  5. #5

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    I really appreciate your help. I am using the 4 bladed prop that comes on the plane 10 x 8. So the main thing I would need to be sure of using the larger ESC and 14.8v is that I don't exceed the rated amp draw for the motor. I'll keep digging to see if Durafly can provide the specs.

  6. #6
    Moderator aeajr's Avatar
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    That is correct. If you exceed the motor's max amps it will heat up and likely cause a short in the windings or the shaft bearing will swell and seize up. Make sure you have excellent cooling over the motor if you go to a 4S pack and consider doing down a size in the prop.

    If you have a 10X8 today, consider going to a 9X8

    Finally, if you are going to start to go off on your own with props and motors and batteries a Wattmeter is a vital tool.

    This is the one I use:
    http://www3.towerhobbies.com/cgi-bin...&I=LXLMV0&P=ML
    Last edited by aeajr; 05-29-2014 at 07:43 PM.
    Long Island Silent Flyers
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  7. #7

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    Great, I will order the meter tomorrow. With the meter installed and the plane sitting static, can you run up the motor and get a good idea of the total amp draw or will the amp draw be higher or lower once the plane is in the air ?

  8. #8
    Moderator aeajr's Avatar
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    Static will usually give you the highest amp draw. There is a certain "unloading" factor when the plane is actually in flight. I have never tested in flight but I am told it is between 15 and 20%.
    Long Island Silent Flyers
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  9. #9

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    Okay,I got the specs on the motor
    GC3536-KV750 +-5%
    Battery 2-4 Lipo
    350W
    Max Current 24.2 amp
    ESC 40amp
    recommended props 13x8, 11x7, the plane came with a 4 blade 10x8 and said to use 11.1v

    So I understand that the motor can handle the 4s battery pack. Now I need to learn what math to do to find out what the amp draw will increase to with the larger battery and if I can get away with the 4 bladed prop or is the only way to discover a particular prop/amp draw combo to use the amp meter ?
    Last edited by superchargedill; 05-30-2014 at 09:37 PM.


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