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Current Limiter On The Aft Side of Firewall

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nuckollsr(at)cox.net
Guest

Posted: Wed Apr 12, 2006 9:47 am Post subject: Current Limiter On The Aft Side of Firewall

At 12:01 PM 4/12/2006 -0500, you wrote:



 	  Quote: 	
		  



Bob ...

Do you see any problem with mounting the current limiter on the aft side of

the firewall?  I'm trying to keep most electrical hardware components off

the engine side of the firewall.


	


    Why? There's nothing inherently evil about mounting

    things under the cowl. You simply choose parts designed

    to function well in that environment. Certainly things

    like contactors, current limiters, shunts, and batteries

    are candidates for mounting on forward side of firewall.



    Generally speaking, from a maintenance perspective, things

    are easier to get at on the forward side of firewall than

    aft side. I'd put as MUCH stuff as practical on the front side

    with an idea of minimizing firewall penetrations by wires . . .

    especially fat wires.

 	  Quote: 	
		  Is there a limiting wire size for fuselinks ... where the smoke generated

from burning them is just too much for the human body to cope with?


	


    Review Note 4 of



http://aeroelectric.com/articles/Rev11/AppZ_R11F.pdf



    Fusible links are ROBUST. They're kind the mini-version

    of ANN/ANL current limiters. Compared with fuses, they'll

    carry a LOT of current for a long time. I would not

    recommend them for any applications other than those

    suggested in the Z-figures. Further, it's best that

    any fusible link be under the cowl and not in the

    cockpit.

 	  Quote: 	
		  At one time, I thought, the max fuse size for fuse blocks was 20A.  B&C now

lists 15A.  For amperages over 15, what do you suggest for protection of the

wire?


	


    The Bussmann rating for these fuseblocks is 30A max

    for any one branch. As I pointed out in the recent article

    on switch failures . . .



http://aeroelectric.com/articles/Anatomy_of_a_Switch_Failure/Anatomy_of_a_Switch_Failure.html



    . . . electronic components are most likely to fail because

    of environmental effects (in this case, compromised metal

    to metal contact at the contact rocker). De-rating helps to

    slow down the rate at which environmental effects chip away

    at a device's performance.



    What system needs a higher fuse value than 15A?

      < 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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Jerry Grimmonpre'

Joined: 09 Jan 2006
Posts: 144
Location: Huntley, Illinois 60142

Posted: Wed Apr 12, 2006 11:35 am Post subject: Current Limiter On The Aft Side of Firewall

 	  Quote: 	

 <nuckollsr(at)cox.net>   Firewall

 At 12:01 PM 4/12/2006 -0500, you wrote:

>

>

>Bob ...

>Do you see any problem with mounting the current limiter on the aft side 

>of

>the firewall?  I'm trying to keep most electrical hardware components off

>the engine side of the firewall.

    Why? There's nothing inherently evil about mounting

    things under the cowl. You simply choose parts designed

    to function well in that environment. Certainly things

    like contactors, current limiters, shunts, and batteries

    are candidates for mounting on forward side of firewall.

The airplane is an RV8A which is nose heavy by design.  The battery goes 

behind the aft baggage area.   There is no battery planned to go on the 

firewall.  Therefore any electrical hardware mounted to the firewall would 

require more penetrations than already planned.

 	  Quote: 	
		      Generally speaking, from a maintenance perspective, things

    are easier to get at on the forward side of firewall than

    aft side. I'd put as MUCH stuff as practical on the front side

    with an idea of minimizing firewall penetrations by wires . . .

    especially fat wires.

The design of the RV8A includes a storage well directly behind the firewall, 

on the right side and below the fwd baggage area.  This storage well 

provides convenience for working on fuses, contactors, aux battery and a 

wiring center.  This makes the distance from contactors to fuse blocks only 

4-6 inches.  The baggage door covers all of this storage well.  There is no 

need to remove engine cowling unless there is a stater or alternator 

problem.

 	  Quote: 	

    What system needs a higher fuse value than 15A?

The endurance bus feed is planned to be tapped off the hot battery bus 

through a fuse  similar to Z12.  The endurance bus will be running about 

22A.  It seems this feed wire needs to be moved to the hot battery bus lug. 

Should this be done and what method of wire protection should be used with 

this source of power for the endurance bus?

Thanks ...

Jerry Grimmonpre'

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endspeed(at)yahoo.com
Guest

Posted: Wed Apr 12, 2006 1:14 pm Post subject: Current Limiter On The Aft Side of Firewall

Hi Jerry,  I too, believed the 8A would be more

forward in cg than the tailwheel 8.  I came across

some info, where escapes me, that stated the 8A is

actually less forward in cg than the 8.  Apparently,

the gear towers in the 8 are quite heavy and move the

cg more than the 8A's nose gear.  Investigate this to

verify it. I too, will check it out.  Bob



--- Jerry Grimmonpre <jerry(at)mc.net> wrote:



 	  Quote: 	
		   

 Grimmonpre" <jerry(at)mc.net>

 

 

 

 > 

 L. Nuckolls, III" 

 > <nuckollsr(at)cox.net>   Firewall

 >

 > At 12:01 PM 4/12/2006 -0500, you wrote:

 >

 >>

 Grimmonpre" <jerry(at)mc.net>

 >>

 >>Bob ...

 >>Do you see any problem with mounting the current

 limiter on the aft side 

 >>of

 >>the firewall?  I'm trying to keep most electrical

 hardware components off

 >>the engine side of the firewall.

 >

 >    Why? There's nothing inherently evil about

 mounting

 >    things under the cowl. You simply choose parts

 designed

 >    to function well in that environment. Certainly

 things

 >    like contactors, current limiters, shunts, and

 batteries

 >    are candidates for mounting on forward side of

 firewall.

 

 The airplane is an RV8A which is nose heavy by

 design.  The battery goes 

 behind the aft baggage area.   There is no battery

 planned to go on the 

 firewall.  Therefore any electrical hardware mounted

 to the firewall would 

 require more penetrations than already planned.

 

 

 >    Generally speaking, from a maintenance

 perspective, things

 >    are easier to get at on the forward side of

 firewall than

 >    aft side. I'd put as MUCH stuff as practical on

 the front side

 >    with an idea of minimizing firewall

 penetrations by wires . . .

 >    especially fat wires.

 

 The design of the RV8A includes a storage well

 directly behind the firewall, 

 on the right side and below the fwd baggage area. 

 This storage well 

 provides convenience for working on fuses,

 contactors, aux battery and a 

 wiring center.  This makes the distance from

 contactors to fuse blocks only 

 4-6 inches.  The baggage door covers all of this

 storage well.  There is no 

 need to remove engine cowling unless there is a

 stater or alternator 

 problem.

 

 >

 >    What system needs a higher fuse value than 15A?

 

 The endurance bus feed is planned to be tapped off

 the hot battery bus 

 through a fuse  similar to Z12.  The endurance bus

 will be running about 

 22A.  It seems this feed wire needs to be moved to

 the hot battery bus lug. 

 Should this be done and what method of wire

 protection should be used with 

 this source of power for the endurance bus?

 

 Thanks ...

 Jerry Grimmonpre' 

 

 

 

 

 



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Jerry Grimmonpre'

Joined: 09 Jan 2006
Posts: 144
Location: Huntley, Illinois 60142

Posted: Thu Apr 13, 2006 9:10 am Post subject: Current Limiter On The Aft Side of Firewall

Do Not Archive

Hi Robert ...

Your thoughts about the 8 cg being more fwd, were thought provoking sending 

me to Van's site.  Empirical comparisons brings me to the possible belief 

the lack of rake on the 8 gear along with the weight of the towers, could 

place the cg fwd of the 8A.  That tail wheel, being some 16' aft of the main 

gear, does serve as a powerful arm in the scheme of things.  Thanks for your 

info Robert.

Jerry Grimmonpre'



 	  Quote: 	
		   

 <endspeed(at)yahoo.com>



 Hi Jerry,  I too, believed the 8A would be more

 forward in cg than the tailwheel 8.  I came across

 some info, where escapes me, that stated the 8A is

 actually less forward in cg than the 8.  Apparently,

 the gear towers in the 8 are quite heavy and move the

 cg more than the 8A's nose gear.  Investigate this to

 verify it. I too, will check it out.  Bob



 --- Jerry Grimmonpre <jerry(at)mc.net> wrote:

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