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Three Fat Wires on Starter Contactor Bolt: How?

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nuckollsr(at)cox.net
Guest

Posted: Sun Jan 07, 2007 9:31 pm Post subject: Three Fat Wires on Starter Contactor Bolt: How?

At 10:37 PM 1/7/2007 -0600, you wrote:



 	  Quote: 	
		  Folks,



I'm building a GlaStar with the battery behind the baggage 

compartment.  I've run (2) 2 AWG cables from the firewall to the battery 

area.  I intend to terminate the (8 AWG) "B" alternator lead on the 

battery side of the starter contactor as it is shown on Z-11.  I also want 

to run another 8 AWG from the same starter contactor bolt to the fuse 

panel to avoid running another fat wire all the way to the back.



But the starter contactor bolt isn't long enough to capture three lugs 

with lock washer and nut.  I could gain some room by putting a thinner nut 

next to the contactor body but I'm afraid to start wrenching on that nut 

for fear of screwing up the contactor internals.  I have two possible 

approaches and am looking for comments or alternatives.



First, crimp the two 8 AWG wires into a single lug (I have a good crimper 

for big lugs and will fill the cavity with solder).  The space on the 

contactor bolt will be tight but should be feasible.  I could gain even 

more room by using a metal stop nut and eliminating the lock 

washer.  Second, fabricate a short buss bar out of heavy gauge brass and 

attach that to the contactor bolt and fasten the three lugs to the buss 

bar.  My concern here is properly insulating and securing the buss 

bar.  Any shorts here and I'd have a flying arc welder under my 

cowling.  Would that dippable plastic coating material (Plasti-Kote?) 

work?  How about the fuseable silicon tape?



(I've already used an uninsulated piece of brass to tie my ammeter shunt 

into the negative side.  The brass bolt through the "forest-of-tabs" also 

captures the ground strap to the engine crankcase and one end of the brass 

bar.  The ammeter shunt is attached to the other end of the brass bar and 

my 2 AWG negative return cable is attached to the other end of the ammeter 

shunt.)



Unrelated question:  Is Ultra Tef-Gel conductive?  I've been using it on 

some electrical connections on the assumption that it is conductive.  If 

it isn't, I've got some rework to do.



Best regards,



Bob



 

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        Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

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nuckollsr(at)cox.net
Guest

Posted: Sun Jan 07, 2007 9:37 pm Post subject: Three Fat Wires on Starter Contactor Bolt: How?

At 10:37 PM 1/7/2007 -0600, you wrote:



 	  Quote: 	
		  Folks,



I'm building a GlaStar with the battery behind the baggage 

compartment.  I've run (2) 2 AWG cables from the firewall to the battery 

area.  I intend to terminate the (8 AWG) "B" alternator lead on the 

battery side of the starter contactor as it is shown on Z-11.  I also want 

to run another 8 AWG from the same starter contactor bolt to the fuse 

panel to avoid running another fat wire all the way to the back.



But the starter contactor bolt isn't long enough to capture three lugs 

with lock washer and nut.  I could gain some room by putting a thinner nut 

next to the contactor body but I'm afraid to start wrenching on that nut 

for fear of screwing up the contactor internals.  I have two possible 

approaches and am looking for comments or alternatives.



First, crimp the two 8 AWG wires into a single lug (I have a good crimper 

for big lugs and will fill the cavity with solder).


	


    that will work.



 	  Quote: 	
		    The space on the contactor bolt will be tight but should be feasible.  I 

 could gain even more room by using a metal stop nut and eliminating the 

 lock washer.  Second, fabricate a short buss bar out of heavy gauge brass 

 and attach that to the contactor bolt and fasten the three lugs to the 

 buss bar.


	


   that probably works better.



 	  Quote: 	
		     My concern here is properly insulating and securing the buss bar.  Any 

 shorts here and I'd have a flying arc welder under my cowling.  Would 

 that dippable plastic coating material (Plasti-Kote?) work?  How about 

 the fuseable silicon tape?


	


   See pictures at:



http://www.aeroelectric.com/Pictures/Wiring_Technique/Firewall_Ckt_Protection.jpg

http://www.aeroelectric.com/Pictures/Wiring_Technique/Contactor_Interconnect/Contactor_Strap_3.jpg



   This is the engine side of firewall on Model 36 Bonanza. LOTS

   of exposed, high current conductors. What's going go get into them?

   You've got a propeller spinning up front that will make hamburger out

   of you in a heartbeat . . . but we don't put wire cages around them.



   It's perfectly okay to have "open hazards" as long as you've

   done the necessary homework to keep things from falling into them.



 	  Quote: 	
		  

(I've already used an uninsulated piece of brass to tie my ammeter shunt 

into the negative side.  The brass bolt through the "forest-of-tabs" also 

captures the ground strap to the engine crankcase and one end of the brass 

bar.  The ammeter shunt is attached to the other end of the brass bar and 

my 2 AWG negative return cable is attached to the other end of the ammeter 

shunt.)



Unrelated question:  Is Ultra Tef-Gel conductive?  I've been using it on 

some electrical connections on the assumption that it is conductive.  If 

it isn't, I've got some rework to do.


	


   No, it's an anti-seize compound and not conductive. However, in

   a properly bolted or crimped joint, compression forces in the

   metal-to-metal joints would extrude any Tef-Gel out of the joint.

   Don't worry about it.

        Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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