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I need help designing my B-17 electrical system
  • I am building a B17 with a 48" wingspan. I have a spektrum dx6i. After looking at tons of products I'm confused on which brands of servos and speed controllers will work with it. As well How do I match batteries to to the rest and so forth. Please can some one help?


     


    Thanks


    Rich

  • well any brand of servos will work with your spektrum but I know hitec will have any size or strength you could need for that plane. what does the kit recommend for motor/prop size?  I would guess your looking at a 6s lipo for that plane to run 4 outrunner motors
  • Yeah, that sounds about right.

    Nowadays, servos work with any radio system. The connector may have a tab on it that needs to be cut out, but that is not hard to do. Same goes with speed controllers - they will work with any radio system.

    A rule of thumb that is use is to make the battery be 15% of the total airplane weight. Since you have a complex setup, you are better off using my free model airplane calculator and getting a more accurate answer.

    Carlos
  • The size of the speed controler hangs on the amp draw of the motor.  If it were me, I would determine the draw of a motor, and install a speed controler 10% larger than the max draw of the motor at full throtle. 4 motors = 4 speed controlers linked together at the reciever input .
  • That sounds reasonable. The amount of cooling air makes a huge difference in the current capacity of a speed control. A 10% safety margin may not be enough, but is a reasonable starting point.

    Carlos
  • Thanks all for the info. This will get me going. I still have alot of work to do lol
  • I'm curious to hear what happens. Please report back when you've made more progress.

    Carlos
  • This seams a little over powered to me. But all the electronics is still new to me. Does this look like it will work? and does this mean I would need to use 2- 6s or 8s battery packs and split them between the motors?


    Turnigy L3730A-1000 Brushless Motor
     
    Specifications:
    Dimension: 37mm x 30mm
    Weight: 112g Inc 4mm Gold Connector (130g inc all fittings)
    Kv: 1000rpm/V
    Voltage: 11.1v~14.8v (3s~4s)
    Max Power: 580w
    Max Current: 42A
    No load Current: 1.6A
    Diameter of shaft: 4mm
    Thrust: 1700g
    ESC: 60A



    ESC


    Spec.
    Weight: 63g
    Size: 55x35x8mm
    Cells: 12-24Ni MH ~ 4-8S Li Po
    Max Current: 60A
    Burst : 70A
    No BEC
    Timing: 1/7/15/30 programmable
    PWM: 8/16K

  • Looking back at your first post, I have to ask: is this your first model airplane? If it is, a B-17 is a terrible choice.

    You want to have only one power source feeding all of the motors. It is okay to hook up multiple battery packs together. For better efficiency, they should be hooked up in series for a higher system voltage.

    Off the top of my head, I could not tell you if your proposed motor and speed control are a good match for your project. That is exactly what my free online calculator is for. The interactive tutorials are excellent, and I strongly recommend that you go through them first.

    Carlos
  • This is my 3rd model and I have no problem with the building and covering. My first two models were both single engine warbirds and they fly great. The guys at the hobbyshop were just like heres the elctronics though. This is the first time to try to fugure out the design for electrical systems on my own.
  • Okay. That does not sound too bad.

    Carlos
  • So found a set up that looks like it will work great. I did a bunch of research and found a few examples of what was being used in comercial sales.  So this is what I found thats as similar as possible. As well most the models that I looked at were a bit larger so I down graded it a little bit But not by a whole lot.  


     


    4x Turnigy 2200mAh 3S 30C Lipo Pack ( note that there are 2 extra batteries here)


    4x Turnigy L2205-1350 Brushless Motor (100w)


    4x Turnigy TY-P1 25Amp HEXFET® Brushless Speed Controller


    1x OrangeRx R610 Spektrum DSM2 6Ch 2.4Ghz Receiver (w/ Sat Port) = $5.99
    1x OrangeRx R100 Satellite Receiver
    1x 90cm/10008 JR & Spektrum Satellite Receiver Extension Wire 60 & 90cm (2pcs/set)


     Befor I finnish my purchasing I have 1 more question about what you guys use to seal your edges on the plastic skins. I have heard of something that you brush on, then ironed the joint, but they did not say the name of the product used or where it could be found. This was in a post I read some time ago. I have not had any peices come apart on any of my other skins, But if there is away to keep this from happening in the future, That would be great.


    Well. my last planned pruchase on the B-17 should get me everything I need to get this old gal in the sky. I plan to spend about $370. I should only be in this project for about $600 bucks and around 300 hours. Not bad considering my first was well over $1000 and about 700 hours befor she flew her maiden voyage. Well this one is gonna be treat. I'm buiding a total of 3 planes in honor of my Grand Father, the B-17 B-25 Mitchel and the B-29. He is still alive, so I hope that he gets to see all 3 fly.

  • I like your product choices. Good values.

    You probably do not need to brush anything on the plastic covering (Monokote or similar). It comes with a thin layer of adhesive. Some of the stuff that you can brush on is called Balsarite, but I doubt you need any. What you need is a sealing iron to activate the adhesive that's already there.

    I really like what you said about your grandfather and the builds.

    Carlos

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