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Fat wires

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gilles.thesee(at)free.fr
Guest

Posted: Sun Jul 09, 2017 2:55 pm Post subject: Fat wires

Hi all,



Some buddies asked me to install the wiring in their brand new project.



The engine is a Rotax with short connexions so the fattest wires in the 

ship will be AWG 6.



Due to restricted space, they installed their fuseblock on a hinge 

within inches from the battery contactor, but the gauge 6 wire from the 

contactor to the bus proves very stiff and hard to manage with this 

pivoting installation.



I considered using a short length of welder cable, but the insulation is 

so thick that it did not help much.



What would be your opinion about downsizing this particular wire to AWG 

8 or 10 for more flexibility ?



Thanks in advance,



-- 

Best regards,

Gilles

http://contrails.free.fr

http://lapierre.skunkworks.free.fr

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alec(at)alecmyers.com
Guest

Posted: Sun Jul 09, 2017 3:22 pm Post subject: Fat wires

what about using a short stub of 8 gauge with a good splice to 6 gauge?



On Jul 9, 2017, at 18:54, GTH <gilles.thesee(at)free.fr> wrote:






Hi all,



Some buddies asked me to install the wiring in their brand new project.



The engine is a Rotax with short connexions so the fattest wires in the ship will be AWG 6.



Due to restricted space, they installed their fuseblock on a hinge within inches from the battery contactor, but the gauge 6 wire from the contactor to the bus proves very stiff and hard to manage with this pivoting installation.



I considered using a short length of welder cable, but the insulation is so thick that it did not help much.



What would be your opinion about downsizing this particular wire to AWG 8 or 10 for more flexibility ?



Thanks in advance,



-- 

Best regards,

Gilles

http://contrails.free.fr

http://lapierre.skunkworks.free.fr

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jul 09, 2017 3:39 pm Post subject: Fat wires

At 05:54 PM 7/9/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: GTH <gilles.thesee(at)free.fr>



 Hi all,



 Some buddies asked me to install the wiring in their brand new project.



 The engine is a Rotax with short connexions so the fattest wires in the ship will be AWG 6.



 Due to restricted space, they installed their fuseblock on a hinge within inches from the battery contactor, but the gauge 6 wire from the contactor to the bus proves very stiff and hard to manage with this pivoting installation.



 I considered using a short length of welder cable, but the insulation is so thick that it did not help much.



 What would be your opinion about downsizing this particular wire to AWG 8 or 10 for more flexibility ?

 	


  

 Wires need to be sized for the expected service.

 Fat wires in the starter circuit will, no doubt,

 want to be 6AWG. Given that the bus loads on this

 aircraft cannot exceed the system loads. The

 bus feeder can be downsized. What size  alternator

 is installed? Bus loads generally don't exceed

 alternator output . . . 12AWG would be fine for

 up to 30A of engine driven power source.



 I would use a fusible link on such smaller bus

 feeders . . . a 6" piece of 16AWG under

 some firesleeve would be about right for 12AWG

 bus feeder.



 

 

   Bob . . .

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raymondj(at)frontiernet.n
Guest

Posted: Sun Jul 09, 2017 3:40 pm Post subject: Fat wires

Maybe a couple of extra coils in the wire would solve the flexibility 

problem.



Raymond Julian

Kettle River, MN



The things we admire in men, kindness and generosity, openness, honesty, 

understanding and feeling are the concomitants of failure in our system. 

And those traits we detest, sharpness, greed, acquisitiveness, meanness, 

egotism and self-interest are the traits of success. And while men 

admire the quality of the first they love the produce of the second. 

-John Steinbeck, novelist, Nobel laureate (1902-1968)



On 07/09/2017 05:54 PM, GTH wrote:

 	  Quote: 	
		   

 

 Hi all,

 

 Some buddies asked me to install the wiring in their brand new project.

 

 The engine is a Rotax with short connexions so the fattest wires in the 

 ship will be AWG 6.

 

 Due to restricted space, they installed their fuseblock on a hinge 

 within inches from the battery contactor, but the gauge 6 wire from the 

 contactor to the bus proves very stiff and hard to manage with this 

 pivoting installation.

 

 I considered using a short length of welder cable, but the insulation is 

 so thick that it did not help much.

 

 What would be your opinion about downsizing this particular wire to AWG 

 8 or 10 for more flexibility ?

 

 Thanks in advance,

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user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Sun Jul 09, 2017 3:47 pm Post subject: Re: Fat wires

My Rotax 912 powered RV-12, along with 500 others that are flying, all have 12 AWG wires about 4 feet long connecting the Dynamo and battery to the main power bus.  The starter is connected with 8 AWG about 2 feet total length.

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_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Sun Jul 09, 2017 3:50 pm Post subject: Fat wires

On 7/9/2017 5:54 PM, GTH wrote:

 	  Quote: 	
		   



 Hi all,



 Some buddies asked me to install the wiring in their brand new project.



 The engine is a Rotax with short connexions so the fattest wires in 

 the ship will be AWG 6.



 Due to restricted space, they installed their fuseblock on a hinge 

 within inches from the battery contactor, but the gauge 6 wire from 

 the contactor to the bus proves very stiff and hard to manage with 

 this pivoting installation.



 I considered using a short length of welder cable, but the insulation 

 is so thick that it did not help much.



 What would be your opinion about downsizing this particular wire to 

 AWG 8 or 10 for more flexibility ?



 Thanks in advance,



You didn't mention the actual load, but if the plane is Rotax powered, 
	


I'd guess that it shouldn't be too large.



I did a quick google search for a DC current capacity calculator, & 

found this:

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

If you plug in 30 amps, 1% voltage loss, & 0.2 meters length (~8"), It 

says that 14 AWG is adequate. 70 amps asks for  10 AWG. Remember, with 

less than a foot of wire, there's very little resistance loss unless the 

wire is grossly undersized.



6 AWG sounds like major overkill to me, unless they're trying to run the 

starter current through it.



Charlie



---

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gilles.thesee(at)free.fr
Guest

Posted: Mon Jul 10, 2017 10:01 am Post subject: Fat wires

 	  Quote: 	
		  --> AeroElectric-List message           posted by: Charlie England <ceengland7(at)gmail.com> (ceengland7(at)gmail.com)           

           

                 	  Quote: 	
		           

           	
       You didn't mention the actual load, but if the           plane is Rotax powered, I'd guess that it shouldn't be too           large.           

           

           [...]

           

           6 AWG sounds like major overkill to me, unless they're trying           to run the starter current through it.         	
     

     Charlie, Joe, Bob, Raymond, Alec,

     

     Thank you for responding.

     Indeed the Rotax 912iS alternator is rated at 30 A, so 12 AWG with a     16 AWG fuselink seems adequate, and the wire stiffness problem will     be solved.

     

     Thanks a lot,

     

     

     -- 

       Best regards,

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

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