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Date: Sat, 05 Dec 2009 08:53:03 -0600
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Primer in AC/DC Electricity
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Here's a link to a 'discussion' several years ago between the author of 
the article (Greg Richter) and Bob Nuckolls, who manages the 
Aeroelectric Connection here in the USA for homebuilders.

http://www.aeroelectric.com/articles/richter/richter.html

Like Bill says, the only real advantage to 24V is lower wire weight 
(negligible in a small homebuilt, since almost everything is very low 
power consumption these days anyway). Note that on pg 10, Richter 
negates even that advantage by recommending 18gauge wire everywhere even 
on 24 V. (??) The idea that devices will stay 'online' longer with 24v 
instead of 12v is highly suspect; the energy density in 12 or 24v 
batteries is the same, given the same (physical) size battery.

It's worth pointing out that Richter is the guy who made the Blue 
Mountain series of glass panels. His customers had years of nightmares 
getting the gear to work correctly and he's now abandoned them 
completely. You can buy the stuff now for about 15 cents on the dollar, 
if you're willing to gamble.

There are some useful ideas in the article, but if you're at the 
learning stage, how do you know which are useful & which are garbage?

Charlie


Bill Bradburry wrote:
>
> George,
>
> He is probably not talking to folks who install an electrically 
> dependant alternative engine. If you just forget the problems that 
> might arise getting Tracy’s controllers, etc, and the 12V auto starter 
> to work on 24V, you still have to accept the fact that that “big 24V 
> battery” can fail. If is does and you don’t have a second battery, it 
> will get very quiet in the cockpit until the screaming starts. Also 
> don’t forget that the only way you can get a 24V battery is to tie two 
> 12V batteries together. If you go with one 24V battery, you have the 
> same battery weight plus the weight of redundant busses. If you go 
> with two batteries, you now have 4 times the weight of one 12V 
> battery. If you try to mix the systems so you have 24V and 12V, you 
> have a nightmare.
>
> The only real advantage seems to me to be wire weight (smaller wire 
> for 24V). I am pretty sure that I ate more weight for last nights 
> dinner than the entire wireing system in my plane :>)
>
> If you really want to save weight in your plane, go on a diet! (I 
> don’t want to hear that you are 7 feet tall and weigh 120 lbs! :>))
>
> Bill B
>
> ------------------------------------------------------------------------
>
> *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] 
> *On Behalf Of *George Lendich
> *Sent:* Friday, December 04, 2009 3:45 PM
> *To:* Rotary motors in aircraft
> *Subject:* [FlyRotary] Re: Primer in AC/DC Electricity
>
> Kelly,
>
> Being electronically challenged I had a quick look. It says 24 volts 
> is better for aircraft use eliminating the need for extra batteries 
> and alternator, I'm wondering why builders collectively don't already 
> go that way. Are there complications or additional expenses to be 
> considered or are auto conversions typically locked in to a 12 volt 
> system for one reason or another - perhaps just the alternator.
>
> George ( down under)
>
>     Group,
>
>     Some of you may have already seen this and to others this may be
>     knowledge that you carry
>
>     around in your head and use everyday but to someone like me whose
>     schooling in AC/DC (Navy)
>
>     electricity was 50 plus years ago and also something I do not use
>     everyday the following link has
>
>     refreshed my old brain..............Hope some of the group finds
>     it useful..............
>
>     http://www.eaa.org/experimenter/articles/0903_aircraft_wiring.pdf
>
>     --
>     Kelly Troyer
>     "Dyke Delta"_13B ROTARY Engine
>     "RWS"_RD1C/EC2/EM2
>     "Mistral"_Backplate/Oil Manifold
>
>