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rv8ch
Joined: 10 Jan 2006
Posts: 250
Location: Switzerland
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 Posted: Sun Apr 22, 2012 9:31 pm Post subject: Starter contactor location |
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I have a rear-mounted battery on my RV8 and I'm trying to figure out why I wouldn't want to install the starter solenoid in the back near the battery instead of on the firewall - anyone see an issue with putting it back there?
Advantages I see:
1) the long run of the fat cable will not be energized when not starting the engine
2) less stuff on the firewall
3) a bit more weight in the back
Thanks for any tips.
--
Mickey Coggins
[quote][b]
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Mickey Coggins
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stuart(at)stuarthutchison
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| Posted: Mon Apr 23, 2012 12:51 am Post subject: Starter contactor location |
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G'day Mickey,
The aim is to pick off master power from the "big lead" as it enters the starter solenoid up front. Seems to be more cumbersome to run a big lead forward to carry start currents (energised or not) and another lead forward to carry main bus power.
Kind regards, Stu<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY [url=about:www.teamrocketaircraft.com]www.teamrocketaircraft.com[/url]
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Mickey Coggins
Sent: Monday, April 23, 2012 3:29 PM
To: aeroelectric-list(at)matronics.com
Subject: Starter contactor location
I have a rear-mounted battery on my RV8 and I'm trying to figure out why I wouldn't want to install the starter solenoid in the back near the battery instead of on the firewall - anyone see an issue with putting it back there?
Advantages I see:
1) the long run of the fat cable will not be energized when not starting the engine
2) less stuff on the firewall
3) a bit more weight in the back
Thanks for any tips.
--
Mickey Coggins
[quote]
href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
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maca2790
Joined: 26 Jan 2011
Posts: 59
Location: Australia
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| Posted: Mon Apr 23, 2012 1:39 am Post subject: Re: Starter contactor location |
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Electrically Speaking (Impedance) there is no difference between the Solenoid being at the front or the rear.
Mechanically you will need to run another Heavy cable (8ga) to the front if
you have the Solenoid at the Battery.
So in the end you will save weight and dollars by running the 2 ga cable to the firewall and then an 8 ga cable to the distribution bus.
cheers
John MacCallum
RV10
VH-DUU
#41016
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stuart(at)stuarthutchison
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| Posted: Mon Apr 23, 2012 1:39 am Post subject: Starter contactor location |
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Sure, but even medium wires + twisted metal = enough sparks to ignite fires ... hence the reason for turning the master off (once the flaps are out/comms complete) before any crash landing  Some builders also slot the forward wing tank attach point to help avoid the tank being ripped open in a crash ... any fire is bad of course, but I would be more concerned about igniting fuel fumes than a slower starting fire electrical fire ... and practically any gauge power wire can spark off fuel fumes.
Kind regards, Stu<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bob Verwey
Sent: Monday, April 23, 2012 7:03 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: AeroElectric-List: Starter contactor location
I have had the same thought as Mickey.....from a safety point of view, I think this is a huge plus. Twisted metal and big conductors equals sparks.....
Best..
Bob Verwey
Safari ZU-AJF in rebuild
On 23 April 2012 10:51, Stuart Hutchison <stuart(at)stuarthutchison.com.au (stuart(at)stuarthutchison.com.au)> wrote:
[quote] G'day Mickey,
The aim is to pick off master power from the "big lead" as it enters the starter solenoid up front. Seems to be more cumbersome to run a big lead forward to carry start currents (energised or not) and another lead forward to carry main bus power.
Kind regards, Stu
F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY www.teamrocketaircraft.com
From: owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com) [mailto:owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)] On Behalf Of Mickey Coggins
Sent: Monday, April 23, 2012 3:29 PM
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: Starter contactor location
I have a rear-mounted battery on my RV8 and I'm trying to figure out why I wouldn't want to install the starter solenoid in the back near the battery instead of on the firewall - anyone see an issue with putting it back there?
Advantages I see:
1) the long run of the fat cable will not be energized when not starting the engine
2) less stuff on the firewall
3) a bit more weight in the back
Thanks for any tips.
--
Mickey Coggins
href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Mon Apr 23, 2012 1:45 am Post subject: Re: Starter contactor location |
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Mickey,
A rear mounted starter contactor will work just fine. The disadvantage is that a longer wire will be required to connect the battery to the main bus at the panel. Weight can be saved by wiring the plane the conventional way using shorter wires for the main bus and starter contactor control.
If installed properly, the big fat cable is unlikely to short to ground. Just remember to shut off the master switch if a forced landing is imminent.
Joe
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Joe Gores |
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nuckolls.bob(at)aeroelect
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| Posted: Mon Apr 23, 2012 1:15 pm Post subject: Starter contactor location |
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At 12:29 AM 4/23/2012, you wrote:
| Quote: | I have a rear-mounted battery on my RV8 and I'm trying to figure out
why I wouldn't want to install the starter solenoid in the back near
the battery instead of on the firewall - anyone see an issue with
putting it back there?
Advantages I see:
1) the long run of the fat cable will not be energized when not
starting the engine
|
and it's also not available for taking alternator
output to the battery . . . or bringing current
forward for running your electro-whizzies.
| Quote: | 2) less stuff on the fire wall
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The forward side of a fire wall is sort of the
preferred place to be a distribution depot for
things electrical and fluid. It's a flat surface
of significant area for organizing such tasks and
compared to all other spaces, much easier to get
at (cowl removal) than say stuffed in between
the panel and fire wall.
| Quote: | 3) a bit more weight in the back
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If you have a w/b problem better to put in a larger
battery (useful weight in terms of watt-seconds per
pound of energy stored) or move the battery aft.
Legacy design goals for distribution of power from
the most dangerous source of energy on the airplane
calls for (1) crew controlled disconnect of all
major feeders AT the battery via either battery contactor,
keeping always-hot feeders small and protected by
fast devices (7A or less fuses) or 'mini-contactor'
for isolating less than minor feeders like the alternate
feed to the e-bus.
http://tinyurl.com/756ydec
By taking your fat wire from battery contactor to
a starter contactor on the fire wall, this single
fat-wire starts the engine, supplies power from battery
to electro-whizzies, charges the battery, and terminates
at a handy distribution point right up front where things
are happening.
It was once said that "all roads lead to Rome." In little
airplanes all wires lead to the battery side of the starter
contactor.
Bob . . .
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