AeroElectric-List Digest Archive

Sun 06/30/13


Total Messages Posted: 5



Today's Message Index:
----------------------
 
     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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    Time: 09:08:44 AM PST US
    Subject: Master Switch/Contactor and Starter Questions
    From: "dgaldrich" <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? 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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    Time: 01:23:51 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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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    Time: 02:09:14 PM PST US
    From: Peter Pengilly <peter@sportingaero.com>
    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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    Time: 04:46:57 PM PST US
    Subject: Re: Master Switch/Contactor and Starter Questions
    From: "Eric M. Jones" <emjones@charter.net>
    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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    Time: 09:38:57 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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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