Today's Message Index:
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1. 09:08 AM - Master Switch/Contactor and Starter Questions (dgaldrich)
2. 01:23 PM - Re: Master Switch/Contactor and Starter Questions (Robert L. Nuckolls, III)
3. 02:09 PM - Re: Master Switch/Contactor and Starter Questions (Peter Pengilly)
4. 04:46 PM - Re: Master Switch/Contactor and Starter Questions (Eric M. Jones)
5. 09:38 PM - Re: Re: Master Switch/Contactor and Starter Questions (Robert L. Nuckolls, III)
Message 1
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Subject: | Master Switch/Contactor and Starter Questions |
Hi Robert et al.
Two issues to discuss
Under what circumstances could you recommend/condone the use of a simple mechanical
master switch (as in Z-17) rather than a traditional battery contactor?
I am building an aircraft with very similar loads to Z-17 but will have an 18 amp
dynamo/PMG and an Odyssey 680 battery so I guess the real question is, do those
two items change the ability to use a switch versus the additional complexity
and "hold" current usage of a contactor?
Second issue is wiring the starter. Mine has two separate terminals. One for
the serious current and one for the solenoid. I'm planning to wire the battery
directly to the starter with #2AWG cable and use #16AWG from the solenoid to
the start switch and back through a 5 or 10 amp CB. All of the Z- diagrams show
a start contactor so I'm wondering if my planning passes the "idiot" test.
Thanks.
Dave
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=403652#403652
Message 2
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Subject: | Re: Master Switch/Contactor and Starter Questions |
At 11:07 AM 6/30/2013, you wrote:
><dgaldrich@embarqmail.com>
>
>Hi Robert et al.
>
>Two issues to discuss
>
>Under what circumstances could you recommend/condone the use of a
>simple mechanical master switch (as in Z-17) rather than a
>traditional battery contactor?
It needs to serve the same purpose as any other form
of battery master . . . offer the pilot direct control
of the battery by means located as close as possible to\
the battery . . . generally less than 1 foot. EVERY OBAM
aircraft could use a manual master switch as long as it
was in convenient reach of the pilot.
>I am building an aircraft with very similar loads to Z-17 but will
>have an 18 amp dynamo/PMG and an Odyssey 680 battery so I guess the
>real question is, do those two items change the ability to use a
>switch versus the additional complexity and "hold" current usage of
>a contactor?
You CAN purchase a low-hold current contactor . . . but
have you done a load analysis? What are your full up
running loads?
>Second issue is wiring the starter. Mine has two separate
>terminals. One for the serious current and one for the
>solenoid. I'm planning to wire the battery directly to the starter
>with #2AWG cable and use #16AWG from the solenoid to the start
>switch and back through a 5 or 10 amp CB. All of the Z- diagrams
>show a start contactor so I'm wondering if my planning passes the "idiot" test.
It's not generally done that way . . . opening the
battery master is supposed to take the system max-cold.
This would include fat wires to the starter.
What kind of airplane/engine combination are we discussing?
Do you have night lighting? What drove your decision for the
680 as opposed to a smaller battery?
Bob . . .
Message 3
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Subject: | Re: Master Switch/Contactor and Starter Questions |
Dave,
Here's a couple of ideas for you to consider,
1. If a switch is used as the 'master switch' as you suggest, some
distance from the battery, consider installing a 20 or 25A (or similar)
c/b close to the battery, and in reach of the pilot, so if need be
breaker can be pulled and the system will be cold from there on.
2. Fit a starter relay close to the battery - that way you do not have
hot thick wires running to the engine all the time. The issue then is
the starter relay welding itself shut, where releasing the starter
button will not stop the starter. Some modern starters with an on board
solenoid allow for the path energising the solenoid to be broken - such
as SkyTec NL series. If a switch is added in the cockpit in this path
then the starter can be turned off with a welded starter relay.
Regards, Peter
On 30/06/2013 17:07, dgaldrich wrote:
>
> Hi Robert et al.
>
> Two issues to discuss
>
> Under what circumstances could you recommend/condone the use of a simple mechanical
master switch (as in Z-17) rather than a traditional battery contactor?
>
> I am building an aircraft with very similar loads to Z-17 but will have an 18
amp dynamo/PMG and an Odyssey 680 battery so I guess the real question is, do
those two items change the ability to use a switch versus the additional complexity
and "hold" current usage of a contactor?
>
> Second issue is wiring the starter. Mine has two separate terminals. One for
the serious current and one for the solenoid. I'm planning to wire the battery
directly to the starter with #2AWG cable and use #16AWG from the solenoid
to the start switch and back through a 5 or 10 amp CB. All of the Z- diagrams
show a start contactor so I'm wondering if my planning passes the "idiot" test.
>
> Thanks.
>
> Dave
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=403652#403652
>
>
Message 4
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Subject: | Re: Master Switch/Contactor and Starter Questions |
The FAA doesn't require a battery contactor and you car doesn't have one. The contactor
per FAA "must disconnect the battery with one hand in the event of an
emergency" e.g. crash.
Nascar has the same issues, but the cars' enormous vibration has pretty much forced
racecar builders to use battery switches instead.
I recommend Flaming River remote battery switches, but there are others.
The entire experimental aircraft can be built without contactors, and I think it's
a good approach.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=403664#403664
Message 5
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Subject: | Re: Master Switch/Contactor and Starter Questions |
>
>
>The entire experimental aircraft can be built without contactors,
>and I think it's a good approach.
I took dual instruction in a TriPacer back in '61 that
mounted the battery under the pax seat. The battery master
was a switch that you could reach under the seats between
pilot and co-pilot. The starter was a manual push button
in a similar position between the pilot's knees.
A contactor is not required . . . just a battery master
disconnect. If you can acquire manual switches suited to
the task and they can be mounted for convenient access
the choice is yours.
Bob . . .
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