REFLECTOR: 24 volts vs. 12 volts

[Douglas Holub]

30 feet round trip.
  ----- Original Message ----- 
  From: dandemitchell at earthlink.net 
  To: Velocity Aircraft Owners and Builders list 
  Sent: Wednesday, January 19, 2005 9:29 PM
  Subject: Re: REFLECTOR: 24 volts vs. 12 volts


  Thats a pretty long Velocity!  Based on your calculations and going say 20 feet then you will save ~1.505 Lbs.  Spread this along the length of the aircraft for proper W&B and it equals about three Big Mac's w/ fries (how many passengers are you carrying?) or 1/4 gallon of AVgas. Doesn't seem like a reasonable trade-off. As far as voltage drop, most of the drop is at the connectors so keep them clean and you should never see less than ~9-10 VDC  at the starter unless it is really cold. Then watch the oil pressure!

  Ed


    ----- Original Message ----- 
    From: Douglas Holub 
    To: Velocity Aircraft Owners and Builders list
    Sent: 1/16/2005 9:11:08 PM 
    Subject: Re: REFLECTOR: 24 volts vs. 12 volts


    If anyone is interested, I did some calculations: 30 feet of 2 AWG wire weighs 6 lbs, and will drop .468 volts with a 100 amp load; 30 feet of 4 AWG wire weighs 3.78 lbs and will drop .373 volts with a 50 amp load.

    Doug
      ----- Original Message ----- 
      From: Joe 
      To: Velocity Aircraft Owners and Builders list 
      Sent: Sunday, January 16, 2005 10:13 PM
      Subject: Re: REFLECTOR: 24 volts vs. 12 volts


      Doug,
      No real downside if all the components you use are rated for 24v (radios etc.)  You will need speed brake and trim actuators for 24v or build a voltage divider into those circuits.  I was going to go 24v myself, but since I am doing an auto conversion finding a 24v starter and/or 24v ECU made it easier to stay 12v.

      Be careful with your statement about wires being smaller by 1/2, wire size to current capability is not linear.  The wire length also has to be included into wire sizing so that there is no more than a 0.5v drop on 12v circuits and 1.0v on 24v circuits.  AC 43-13 is a good source for sizing wire in aircraft applications.

      One possible downside, if you want 110 vac power for say a laptop computer, you might have a hard time finding a 24V inverter.

      Joe
        ----- Original Message ----- 
        From: Douglas Holub 
        To: reflector at tvbf.org 
        Sent: Sunday, January 16, 2005 10:37 PM
        Subject: REFLECTOR: 24 volts vs. 12 volts


        If I have a 24 volt system I'll use half the current so my wires can be smaller by 1/2 and I'll save a pound or two. What's the downside?

        Doug


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