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jpx(at)Qenesis.com
Guest

Posted: Tue May 26, 2009 7:26 am Post subject: Engine mount as starter ground path

Does anyone have some scientific information (beyond the practical  

description in the Connection) that I can use to convince someone that  

running the engine ground strap to the engine mount is a poor choice ?



Thanks !



Jeff Page

Dream Aircraft Tundra #10

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Tue May 26, 2009 9:15 am Post subject: Engine mount as starter ground path

Totally separate but possibly dead on.  My 1978 Ford pickup suffered

catastrophic electrolysis of the cab floorboards and the entire bed

(years 28-31).  The Tailgate was replaced with an Electro-Hydraulic

1,000 pound Tommy Lift. The lift motor used high current capacity

welding cable with neoprene shielding for the Positive.  NO GROUND.

Just the mounting to the bed of the truck and the frame rails.  All of a

sudden over the last several years, the truck began rapid corrosion

(Really Rapid - Decomposition).



My conclusion.  Stray electrons looking for the primary path to ground -

found their path without the aid of the missing ground.  My action -

Never again! use a structural mount in hopes of taking a path of less

effort during installation.  Provide an adequate ground from the battery

or generator source.  Listen to Bob.  Semi-monocoque construction makes

it even more valid.



YMMV.

John Cox

 						Now for the experts.



--

longg(at)pjm.com
Guest

Posted: Tue May 26, 2009 9:52 am Post subject: Engine mount as starter ground path

How about the scientific principle of rubber engine mounts being a poor

conductor of electricity? That would go for the cadmium plating on the

bolts themselves. Not a perfect conductor. Scientifically engine

mounting bolts will corrode over time, get oily and generally loose what

connectivity they have.



Under Ohm's law the addition of the engine mount changes sub R in the

equation reducing the conductance value of the material. If he works out

the equation using the combined values conductivity will be less. After

he is done scratching his head, he'll recognize why it's done this way.



See: http://en.wikipedia.org/wiki/Electrical_conductance



If he is trying to save $3.00 on the cost of the additional 5" of cable

required to anchor it to the engine, there is little argument on his

side.

--

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 26, 2009 12:56 pm Post subject: Engine mount as starter ground path

At 10:14 AM 5/26/2009, you wrote:

 	  Quote: 	
		  



Does anyone have some scientific information (beyond the practical

description in the Connection) that I can use to convince someone that

running the engine ground strap to the engine mount is a poor choice ?



Thanks !


	


    The shortest, lowest resistance and minimum parts count path

    in any high current conduction path is the road to Ground

    System Nirvana. See:



http://www.aeroelectric.com/articles/grnding.pdf



    Engine mounts are steel assembled with steel

    hardware. The joints between mounts and other

    components of the airframe are not treated for

    the purpose of electrical "bonding". The engine

    mount is intended to hold the engine on the

    airplane and was not designed or installed to

    be a part of the electrical system.



    Note that Figure Z-15 and Chapter 5 of the

    'Connection speak to and illustrate a notion

    that engines are best tied to the single point

    fire-wall ground block with a single-flexible-

    fatwire. To avoid having the firewall sheet

    participate in a PARALLEL ground path (read

    ground loop) any bonding jumpers across the

    engine mounts are best removed.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

Kellym

Joined: 10 Jan 2006
Posts: 1706
Location: Sun Lakes AZ

Posted: Tue May 26, 2009 1:22 pm Post subject: Engine mount as starter ground path

Given such a ground path, how does one get lineboys trained that the engine exhaust pipe is a terrible place for ground wire, that the fuel tanks are in the wings, and something like a bare spot on wing tiedown has a much shorter ground path? I always wonder how static charge is supposed to make it from the fuel tank through the airframe to the engine and down the rusty, carboned up exhaust pipe, usually with a swivel or slip joint or two to that ground wire, without significant resistance.

 

 Robert L. Nuckolls, III wrote:  	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> (nuckolls.bob(at)aeroelectric.com)   

   

 At 10:14 AM 5/26/2009, you wrote:   

    	  Quote: 	
		  --> AeroElectric-List message posted by: "Jeff Page" <jpx(at)Qenesis.com> (jpx(at)Qenesis.com)     

     

 Does anyone have some scientific information (beyond the practical     

 description in the Connection) that I can use to convince someone that     

 running the engine ground strap to the engine mount is a poor choice ?     

     

 Thanks !     

   	
   

    The shortest, lowest resistance and minimum parts count path   

    in any high current conduction path is the road to Ground   

    System Nirvana. See:   

   

 http://www.aeroelectric.com/articles/grnding.pdf   

   

    Engine mounts are steel assembled with steel   

    hardware. The joints between mounts and other   

    components of the airframe are not treated for   

    the purpose of electrical "bonding". The engine   

    mount is intended to hold the engine on the   

    airplane and was not designed or installed to   

    be a part of the electrical system.   

   

    Note that Figure Z-15 and Chapter 5 of the   

    'Connection speak to and illustrate a notion   

    that engines are best tied to the single point   

    fire-wall ground block with a single-flexible-   

    fatwire. To avoid having the firewall sheet   

    participate in a PARALLEL ground path (read   

    ground loop) any bonding jumpers across the   

    engine mounts are best removed.   

   

   

        Bob . . .   

   

        	
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

europaul260i(at)bvunet.ne
Guest

Posted: Tue May 26, 2009 1:22 pm Post subject: Engine mount as starter ground path

How about some anecdotal evidence. I had a Cadillac 4.9 liter V8 installed 

in my Pontiac Fiero. Since it weighted 15 pounds more than the V6 that was 

in there, I had the battery moved from the rear engine compartment to just 

on top of the front axle. My voltmeter would not show over 13.5 volts even 

when the battery was weak and would drop below 12 volts if I ran the AC and 

lights at the same time. I would also have intermittent problems starting 

the car when it was hot. The battery was grounded to the frame and the 

engine was also grounded to the frame. A 9 foot #2 wire went from the 

positive terminal to the starter. After putting on a new starter the engine 

would not start hot the very first time I drove it somewhere. I put a 9 foot 

#2 wire from the negative side of the battery to the one of the mounting 

studs of the starter and now no more starting problems. The voltmeter shows 

14.5 volts on start-up and after a brief drop when turning on the lights and 

AC, it shows 13.5 volts. The ground is important. I only wish it hadn't 

taken me 2 years to figure it out.



Vaughn Teegarden



---

frank.hinde(at)hp.com
Guest

Posted: Tue May 26, 2009 1:37 pm Post subject: Engine mount as starter ground path

Just be thankful your ground path didn't go thru your crank bearings..You would have figured itout a lot sooner though.. 



Frank

RV 7a and a tractor where the battery negative goes directly to the starter as well!



--

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 26, 2009 2:51 pm Post subject: Engine mount as starter ground path

At 04:21 PM 5/26/2009, you wrote:

 	  Quote: 	
		  Given such a ground path, how does one get lineboys trained that the 

engine exhaust pipe is a terrible place for ground wire, that the 

fuel tanks are in the wings, and something like a bare spot on wing 

tiedown has a much shorter ground path? I always wonder how static 

charge is supposed to make it from the fuel tank through the 

airframe to the engine and down the rusty, carboned up exhaust pipe, 

usually with a swivel or slip joint or two to that ground wire, 

without significant resistance.


	


   The line boy's ground lead is not intended to carry

   more than micro-amps of current . . . and then for

   only enough time to equalize the STATIC charge on

   the airplane with the STATIC charge on the fuel truck.



   Given the proliferation of composite aircraft it's

   not a bad bet for fuel truck operators to use the exhaust

   pipe . . . it's metallic and definitely connected to

   the crankcase through other metallic parts. Now, it's

   entirely possible that a metallic tank resides in a

   composite wing and is plumbed up with some modern

   synthetic tubing . . . it's a tiny bit of a crap-shoot.



   Bottom line is that the rusty, gunked up piece of pipe

   is not a bad choice.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

MauleDriver(at)nc.rr.com
Guest

Posted: Tue May 26, 2009 5:49 pm Post subject: Engine mount as starter ground path

The Z-14 I've put into my RV10 follows the best practices as described 

in the Connection with one oversight.... I have the 2 sided forest of 

tabs on the firewall but I only have an AWG 8 cable  running to it from 

the rear batteries instead of an AWG2 fat wire.  And it's too late to 

swap it out without significant re-work.

  The isssue is how to get the engine adequately grounded for the 

start.  I remember this same situation being discussed recently on 

either the RV10 or AeroConnection list but I'd like to get some more 

input regarding my choices as I see it.

Choice1: Run a flat fat wire (AWG 2 equivalent) from the forest of tabs 

lug to the engine and keep the engine mount out of the circuit.  Here 

I'm depending on the AWG 8 cable and the firewall to provide and 

adequate ground for starting.  I feel that I do have a solidly grounded 

airframe and it is a metal fuselage.

Choice2: Ground the engine to the mount per Van's wiring diagram  - 2 

straps from the mount to the engine and relying on the 6 mount bolts to 

provide what they're  not designed to provide.  Here I'm trusting that 

the steel engine mount will work as a working part of my  electrical 

system - clearly this is what the Connection is steering me away from.

Choice3: Do both 1 and 2 which gives me a better chance of an adequate 

ground than either choice alone gives me, but I run the risk of ground 

loops.  (what is the potential impact of ground loops in the starter 

circuit?  Does this introduce potential ground loop problems to systems 

connected to the forest of tabs?)

Bob, thanks for covering the same ground over and over!

Bill "enjoying panel wiring and fiberglassing at the same time" Watson

RV10 40605

Robert L. Nuckolls, III wrote:

 	  Quote: 	

 <nuckolls.bob(at)aeroelectric.com>

 At 10:14 AM 5/26/2009, you wrote:

> 

>

> Does anyone have some scientific information (beyond the practical

> description in the Connection) that I can use to convince someone that

> running the engine ground strap to the engine mount is a poor choice ?

>

> Thanks !

    The shortest, lowest resistance and minimum parts count path

    in any high current conduction path is the road to Ground

    System Nirvana. See:

 http://www.aeroelectric.com/articles/grnding.pdf

nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 26, 2009 8:38 pm Post subject: Engine mount as starter ground path

t 08:47 PM 5/26/2009, you wrote:


<MauleDriver(at)nc.rr.com>



The Z-14 I've put into my RV10 follows the best practices as 

described in the Connection with one oversight.... I have the 2 sided 

forest of tabs on the firewall but I only have an AWG 8 

cable  running to it from the rear batteries instead of an AWG2 fat 

wire.  And it's too late to swap it out without significant re-work.



   Is this the ONLY ground for the rear-mounted batteries?

   8AWG is waaayyyy too small. Pull it out and ground the

   battery(ies) locally to the airframe.



http://aeroelectric.com/Pictures/Batteries/Battery_Install_OBrien_1.jpg



http://aeroelectric.com/Pictures/Batteries/Battery_Install_OBrien_2.jpg



http://aeroelectric.com/Pictures/Grounding/Local_Battery_Grounds_1.jpg

The isssue is how to get the engine adequately grounded for the 

start.  I remember this same situation being discussed recently on 

either the RV10 or AeroConnection list but I'd like to get some more 

input regarding my choices as I see it.



Choice1: Run a flat fat wire (AWG 2 equivalent) from the forest of 

tabs lug to the engine and keep the engine mount out of the circuit.



    This is a given . . . no matter what the

    rest of the ground system looks like.

   Here I'm depending on the AWG 8 cable and the firewall to provide 

and adequate ground for starting.  I feel that I do have a solidly 

grounded airframe and it is a metal fuselage.



    I'm not sure from your description where the ends

    of the 8AWG wire are tied. This size of

    wire is too small for any significant starter

    performance.



Choice2: Ground the engine to the mount per Van's wiring diagram  - 2 

straps from the mount to the engine and relying on the 6 mount bolts 

to provide what they're  not designed to provide.  Here I'm trusting 

that the steel engine mount will work as a working part of 

my  electrical system - clearly this is what the Connection is 

steering me away from.



    It's been done before. Leave it alone.



Choice3: Do both 1 and 2 which gives me a better chance of an 

adequate ground than either choice alone gives me, but I run the risk 

of ground loops.  (what is the potential impact of ground loops in 

the starter circuit?  Does this introduce potential ground loop 

problems to systems connected to the forest of tabs?)



    Do them both and ground the batteries

    to the airframe. The 8AWG wire can be

    cut loose and pulled out.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

nuckolls.bob(at)aeroelect
Guest

Posted: Wed May 27, 2009 5:37 am Post subject: Engine mount as starter ground path

At 11:35 PM 5/26/2009, you wrote:

 	  Quote: 	
		  

<nuckolls.bob(at)aeroelectric.com>



t 08:47 PM 5/26/2009, you wrote:


<MauleDriver(at)nc.rr.com>



The Z-14 I've put into my RV10 follows the best practices as 

described in the Connection with one oversight.... I have the 2 

sided forest of tabs on the firewall but I only have an AWG 8 

cable  running to it from the rear batteries instead of an AWG2 fat 

wire.  And it's too late to swap it out without significant re-work.


	


   Bill, re-reading my posting from last night I'm not

   sure I conveyed a clear image of my recommendations.

   In a nutshell:



   Add local grounds to airframe for the batteries if

   you don't already have them.



   Add crankcase to firewall ground stud for engine.



   Leave jumpers across the engine mount biscuits.



   You can cut the 8AWG wire out if you wish and

   if it is practical. It adds only weight and

   offers no significant electrical function.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

airlincoln(at)sbcglobal.n
Guest

Posted: Wed May 27, 2009 10:03 am Post subject: Engine mount as starter ground path

The discussion about engine mounts as ground points has generated a question.  The "When is a Good Ground Not?" article shows 2AWG wire for the high current paths as do the Z-15 diagrams demonstrating various grounding architectures.  



The Z-13/8 diagram I was planning my electrical system around shows 4AWG wires for these same high current paths.  All my "fat wires" will be under 3 feet since my RG battery, starter and battery contactors, 40A alternator, and firewall ground block will all be on or close to the firewall.  I thought I had read somewhere in the "AeroElectric Connection" that 4AWG was fine as long as all the fat wires were 3 feet or less, but now I can't find it.

Could someone confirm that 4AWG welding cable is acceptable for the high current wires when these wires are all located on the hot side of  the firewall, wired per Z-13/8 and each under three feet in length?

Lincoln Keill

RV-7A

Do not archive

 [quote][b]

MauleDriver(at)nc.rr.com
Guest

Posted: Wed May 27, 2009 10:13 am Post subject: Engine mount as starter ground path

It's crystal clear now!  Thanks



Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 At 11:35 PM 5/26/2009, you wrote:

> 

> <nuckolls.bob(at)aeroelectric.com>

>

> t 08:47 PM 5/26/2009, you wrote:

> 

> <MauleDriver(at)nc.rr.com>

>

> The Z-14 I've put into my RV10 follows the best practices as 

> described in the Connection with one oversight.... I have the 2 sided 

> forest of tabs on the firewall but I only have an AWG 8 cable  

> running to it from the rear batteries instead of an AWG2 fat wire.  

> And it's too late to swap it out without significant re-work.



   Bill, re-reading my posting from last night I'm not

   sure I conveyed a clear image of my recommendations.

   In a nutshell:



   Add local grounds to airframe for the batteries if

   you don't already have them.



   Add crankcase to firewall ground stud for engine.



   Leave jumpers across the engine mount biscuits.



   You can cut the 8AWG wire out if you wish and

   if it is practical. It adds only weight and

   offers no significant electrical function.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Wed May 27, 2009 11:25 am Post subject: Engine mount as starter ground path

Static is usually described as high voltage and  little to no current.  

 That means those nasty electrons are really juiced  up...like a 2 year old loaded with chocolate cake, etc.  They can jump tall  buildings, and wide gaps, etc.  

  

 A hopped up electron does not need a good conductor  to move and be a nuisance.  Rusty or otherwise not well connected pipes,  etc. work just fine.  So connecting a static grounding line to an exhaust  pipe should work just fine to dump most, if not all, of the electrons to  ground.  

  

 Most of my Cessna wing is bare aluminum.  As  an extra precaution, I lightly touch the fuel nozzle to the wing surface before  I even take the fuel caps off.  That also relieves any final electrons off  the table before fueling.  Also, as the fuel flows, I make sure the nozzle  is touching the metal filler neck.  In dry climates especially, flowing  fuel will also generate some static.  With the nozzle grounded against the  filler metal that takes care of those speedy critters also.

 David

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed May 27, 2009 1:37 pm Post subject: Engine mount as starter ground path

At 01:00 PM 5/27/2009, you wrote:

 	  Quote: 	
		  The discussion about engine mounts as ground points has generated a 

question.  The "When is a Good Ground Not?" article shows 2AWG wire 

for the high current paths as do the Z-15 diagrams demonstrating 

various grounding architectures.



The Z-13/8 diagram I was planning my electrical system around shows 

4AWG wires for these same high current paths.  All my "fat wires" 

will be under 3 feet since my RG battery, starter and battery 

contactors, 40A alternator, and firewall ground block will all be on 

or close to the firewall.  I thought I had read somewhere in the 

"AeroElectric Connection" that 4AWG was fine as long as all the fat 

wires were 3 feet or less, but now I can't find it.



Could someone confirm that 4AWG welding cable is acceptable for the 

high current wires when these wires are all located on the hot side 

of the firewall, wired per Z-13/8 and each under three feet in length?


	


   The drawings published on our website and publications

   are intended to illustrate architectures. Exact sizing

   of circuit protection, wires, batteries, alternators, etc.

   are up to the builder based on a host of considerations.



   Your recollection is accurate in that if the battery,

   starter and alternator are all within short distances

   of each other (3' or so) then 4AWG is adequate to the

   task of managing fat-wire duties.



   When engine and batteries are remotely located from each

   other (rear mounted batteries in RV-8, canard pushers) will

   benefit from something bigger like 2AWG battery cables.

   Really extreme cases like some some winged watercraft,

   parallel 2AWG or 0AWG is often used.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

tomhanaway

Joined: 12 Aug 2006
Posts: 111
Location: Murphy, NC

Posted: Thu May 28, 2009 5:08 am Post subject: Engine mount as starter ground path

 	  Quote: 	
		  Bob,My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W.One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts?Thanks, Tom HanawayBoynton Beach, FLRobert L. Nuckolls, III wrote:> <nuckolls.bob(at)aeroelectric.com>> > At 11:35 PM 5/26/2009, you wrote:My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
0 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
1 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
2 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
3 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
4 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
5 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
6 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
7 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
8 	  Quote: 	
		  My first post to this site.  I’m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. 	
9 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
0 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
1 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
2 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
3 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
4 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
5 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
6 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
7 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
8 	  Quote: 	
		  One and two are clear.  I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit.  In a later post, you advise “any bonding jumpers across the engine mounts are best removed” to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? 	
9 	  Quote: 	
		  Thanks, 	
0 	  Quote: 	
		  Thanks, 	
1 	  Quote: 	
		  Thanks, 	
2 	  Quote: 	
		  Thanks, 	
3 	  Quote: 	
		  Thanks, 	
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		  Thanks, 	
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		  Thanks, 	
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		  Thanks, 	
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		  Thanks, 	
8 	  Quote: 	
		  Thanks, 	
9 	  Quote: 	
		  Tom Hanaway 	
0 	  Quote: 	
		  Tom Hanaway 	
1 	  Quote: 	
		  Tom Hanaway 	
2 	  Quote: 	
		  Tom Hanaway 	
3 	  Quote: 	
		  Tom Hanaway 	
4  

   

       [quote][b]

_________________
RV-10. Built and sold
RV-8a. Building

nuckolls.bob(at)aeroelect
Guest

Posted: Thu May 28, 2009 1:11 pm Post subject: Engine mount as starter ground path

At 07:58 AM 5/28/2009, you wrote:



  	  Quote: 	
		   	  Quote: 	
		  Bob,[/b]

My first post to this site.  I’m working on an

rv-10. I thought I understood the grounding once you gave the below

explanation to Bill W.[/b]One and two are clear.  I read #3 as putting a

jumper across an individual mount t0 both sides of a single

biscuit.  In a later post, you advise “any bonding jumpers across

the engine mounts are best removed” to avoid parallel grounds. Equally,

the Connection speaks of a single point ground at firewall. Is this a

contradiction or does it refer to not having jumpers between two

completely separate mounts?

[/b] 	
	


    No, I was referencing a project-in-process where an

    already too-small 8AWG battery(-) wire was installed.

    Upsizing that wire was not an attractive option.

    The work-around involved the used of jumper straps

    around the shock mount biscuits and local battery grounds.



    Now, if you're starting from scratch and your

    battery is located near the firewall, that

    posting was not applicable to you. Use NO

    JUMPERS on the engine mount biscuits. Wire

    as suggested in chapter 5 and Figure Z-15.



    Welcome to the List!



 

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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



     [quote][b]

tomhanaway

Joined: 12 Aug 2006
Posts: 111
Location: Murphy, NC

Posted: Thu May 28, 2009 4:42 pm Post subject: Engine mount as starter ground path

Thanks Bob.  

Sorry to beat a dead horse but I need one more clarification.  Your response mentions “if battery near firewall”.  The batteries are actually both in the aft area.  Can the battery be locally grounded to airframe at site of battery (metal frame craft) with B&C tab forest on firewall for grounds and engine ground?     

   

Or is best solution still to run a 2awg ground wire up to firewall and proceed with grounding to tab forest as above?  

   

Thanks,  

Tom  

         

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III

 Sent: Thursday, May 28, 2009 5:10 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: Re: Engine mount as starter ground path  

  

   

At 07:58 AM 5/28/2009, you wrote:

 

 

    	  Quote: 	
		  Bob, 	
  

    	  Quote: 	
		  My first post to this site.  Im working on anrv-10. I thought I understood the grounding once you gave the belowexplanation to Bill W. 	
  

    	  Quote: 	
		  One and two are clear.  I read #3 as putting ajumper across an individual mount t0 both sides of a singlebiscuit.  In a later post, you advise any bonding jumpers acrossthe engine mounts are best removed to avoid parallel grounds. Equally,the Connection speaks of a single point ground at firewall. Is this acontradiction or does it refer to not having jumpers between twoMy first post to this site.  Im working on an 	
0  



    No, I was referencing a project-in-process where an

    already too-small 8AWG battery(-) wire was installed.

    Upsizing that wire was not an attractive option.

    The work-around involved the used of jumper straps

    around the shock mount biscuits and local battery grounds.

 

    Now, if you're starting from scratch and your

    battery is located near the firewall, that

    posting was not applicable to you. Use NO

    JUMPERS on the engine mount biscuits. Wire

    as suggested in chapter 5 and Figure Z-15.

 

    Welcome to the List!

 

 

     

       Bob . . .

 

        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------   	  Quote: 	
		  My first post to this site.  Im working on an 	
1 	  Quote: 	
		  My first post to this site.  Im working on an 	
2 	  Quote: 	
		  My first post to this site.  Im working on an 	
3 	  Quote: 	
		  My first post to this site.  Im working on an 	
4 	  Quote: 	
		  My first post to this site.  Im working on an 	
5 	  Quote: 	
		  My first post to this site.  Im working on an 	
6 	  Quote: 	
		  My first post to this site.  Im working on an 	
7 	  Quote: 	
		  My first post to this site.  Im working on an 	
8 	  Quote: 	
		  My first post to this site.  Im working on an 	
9 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
0 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
1 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
2 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
3 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
4 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
5 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
6 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
7 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
8 	  Quote: 	
		  rv-10. I thought I understood the grounding once you gave the below 	
9 	  Quote: 	
		  explanation to Bill W. 	
0

       [quote][b]

_________________
RV-10. Built and sold
RV-8a. Building

nuckolls.bob(at)aeroelect
Guest

Posted: Thu May 28, 2009 5:03 pm Post subject: Engine mount as starter ground path

At 07:34 PM 5/28/2009, you wrote:

  	  Quote: 	
		   Thanks Bob.

 Sorry to beat a dead horse but I need one more clarification.  Your response mentions “if battery near firewall”.  The batteries are actually both in the aft area.  Can the battery be locally grounded to airframe at site of battery (metal frame craft) with B&C tab forest on firewall for grounds and engine ground?   

  

 Or is best solution still to run a 2awg ground wire up to firewall and proceed with grounding to tab forest as above?

  

 Thanks,

 Tom

  	
 

 

     You say "both batteries". Which Z-figure are

     you crafting?



 

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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



     [quote][b]

Kellym

Joined: 10 Jan 2006
Posts: 1706
Location: Sun Lakes AZ

Posted: Thu May 28, 2009 5:12 pm Post subject: Engine mount as starter ground path

The RV-10 by necessity and design has the battery(s) located in the 

tailcone to partly offset the weight of the IO-540 up front.

Given that the structure from the battery location to the firewall is 

all riveted aluminum in the lower half of the fuselage there likely is a 

solid ground path. Running a fat wire to parallel that ground path, or 

to replace it doesn't appear to be all that good an option.

Kelly



Robert L. Nuckolls, III wrote:

 	  Quote: 	
		  

    No, I was referencing a project-in-process where an

    already too-small 8AWG battery(-) wire was installed.

    Upsizing that wire was not an attractive option.

    The work-around involved the used of jumper straps

    around the shock mount biscuits and local battery grounds.



    Now, if you're starting from scratch and your

    battery is located near the firewall, that

    posting was not applicable to you. Use NO

    JUMPERS on the engine mount biscuits. Wire

    as suggested in chapter 5 and Figure Z-15.

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

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