REFLECTOR: [c-a] Re: COZY: 24 Volts VS 12 Volts

[Don Johnston]

One thing to keep in mind about the ACC (fatwire)... Is that it's
*VERY*fat. I have 30' of 4AWG wire and it's a larger diameter than
standard
copper 2AWG.  And it has a very large bending radius. That said, it is
very, very light.

BTW, if anyone wants 30' of AWG4 fatwire, let me know. :-)



On Mon, Oct 7, 2013 at 4:13 PM, John Tvedte <johnt at comp-sol.com> wrote:

>  From a practical standpoint 22awg is the smallest wire size one is likely
> to use in an GA aircraft.  Most of the wiring is going to be 20 or 22awg
> and shielded versions thereof...none of which is going to change if 12 vs
> 24V.  Pitot/Electric fuel pump/Alternator(s), feed wires and the starter
> are the 'fat wires'.  Even the alternator "B" field can be 20awg.
>
>
> Here is one way to save weight for the starter and can double as main
> alternator feed.
>
>  http://www.periheliondesign.com/fatwires.htm
>
>  Suggest you use a field wound starter for best performance/lowest
> current draw.
>
>
>
> -------- Original message --------
> From: Clayton Chase <chasec at gmail.com>
> Date: 10/07/2013 1:18 PM (GMT-06:00)
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Subject: Re: REFLECTOR: [c-a] Re: COZY: 24 Volts VS 12 Volts
>
>
>  I'd prefer to go with 24V but have chosen to use a 12V system because of
> the depth of pocket required to go up to 24V.  The equipment isn't any more
> expensive to make, however since there is not a demand for it like there is
> for the 12V equipment.  Due to the auto industry, almost everything you
> could want in a 12V part is mass manufactured.  Therefore I'll be using 12V
> in my plane even though it will add some weight in wires.
>
>
> On Mon, Oct 7, 2013 at 9:37 AM, Dave Philipsen <velocity at davebiz.com>wrote:
>
>>  Heh, heh...nice techno-humor!  The only point I'm trying to make with
>> all of this is that, yes, there are some benefits with a 24v system.  There
>> would be even more benefits with a 48v system and even a 96v system. But at
>> some point the advantages of increasing the voltage diminish to a point
>> where they are not really practical.  Obviously, for automobiles, the
>> engineers decided almost universally that that point was at 12 volts. I
>> believe that for our experimental aircraft the point is also at 12 volts.
>> But, others with perhaps deeper pockets and a desire for slightly greater
>> reliability and dependability may arrive at the point of 24 volts.
>>
>>
>>   Dave Philipsen
>>> Velocity STD FG
>>>
>>     N83DP
>>>
>>
>> On Oct 7, 2013, at 11:08 AM, Don Johnston <numa at comcast.net> wrote:
>>
>>   You are forgiven.
>>
>>  Now go say 50 "Hail Tesla's" and sin no more. :-)
>>
>>
>> On Mon, Oct 7, 2013 at 10:35 AM, Dave Philipsen <velocity at davebiz.com>wrote:
>>
>>> I messed up on the 24v calculations. Strike out the paragraph below and
>>> change to:
>>>
>>> The same scenario with a 24volt 100 amp starter would work out to a 290
>>> milliohm total resistance (starter is 240 milliohms and solenoid contacts
>>> are 50 milliohms). The circuit will now draw 82 amps and you will see 19.86
>>> volts across the starter and 4.13 volts across the solenoid contacts.  This
>>> is a better scenario than the 12v system but not as exaggerated as the
>>> scenario you stated below.
>>>
>>>
>>> Dave Philipsen
>>> Velocity STD FG
>>> N83DP
>>>
>>>  On 10/7/2013 10:15 AM, Dave Philipsen wrote:
>>>
>>>> The same scenario with a 24volt 100 amp starter would work out to a 170
>>>> milliohm total resistance (starter is 120 milliohms and solenoid contacts
>>>> are 50 milliohms). The circuit will now draw 141 amps and you will see 16.9
>>>> volts across the starter and 7.1 volts across the solenoid contacts.  This
>>>> is a better scenario than the 12v system but not as exaggerated as the
>>>> scenario you stated below.
>>>>
>>>
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