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PROBLEM. Electrical Grounding with a primed airframe.

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Geoff Heap

Joined: 12 Jan 2006
Posts: 266
Location: Lindenwold, New Jersey

Posted: Thu Nov 22, 2007 1:11 pm Post subject: PROBLEM. Electrical Grounding with a primed airframe.

I could use some advice or comment. Over the years, as I built my airframe I primed everything just before riveting/assembly. With the knowledge I have now that seems dumb. With the battery behind the passenger seat how can I ground it back there. All airframe parts are isolated from each other electrically. Will the rivets help me out? Would they give me the continuity I need? Do I need to run  a ground wire all the way back to the engine block?

          Lost in Lindenwold



912/dynon 180/icom-a210/garmin 296.

Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Thu Nov 22, 2007 2:54 pm Post subject: Re: PROBLEM. Electrical Grounding with a primed airframe.

The idea of running two cables and having a common ground point is a good one.  That said, the large number of rivets used in your plane's construction should provide ample continuity for ground return for lights, strobes, etc.  



Tim

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

larry(at)macsmachine.com
Guest

Posted: Thu Nov 22, 2007 3:38 pm Post subject: PROBLEM. Electrical Grounding with a primed airframe.

Geoff,

I don't think you have a lot to worry about if you have but a small 

amount of sandpaper

or Scotch Brite.  The link below shows the tray and base I used to get a 

ground via the

cross support.  Probably a dozen rivets involved, but you see the ground 

for both batteries

and I've never had any difficulty with the back feed or connections. 

Much easier to change

batteries this way as well.  check out the link.



http://www.macsmachine.com/images/electrical/full/chargebatteryconnection.gif



Larry McFarland 601HDS at www.macsmachine.com



Geoff Heap wrote:

 	  Quote: 	
		   



 I could use some advice or comment. Over the years, as I built my airframe I primed everything just before riveting/assembly. With the knowledge I have now that seems dumb. With the battery behind the passenger seat how can I ground it back there. All airframe parts are isolated from each other electrically. Will the rivets help me out? Would they give me the continuity I need? Do I need to run  a ground wire all the way back to the engine block?

           Lost in Lindenwold



 912/dynon 180/icom-a210/garmin 296.





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=147968#147968

Afterfxllc(at)aol.com
Guest

Posted: Thu Nov 22, 2007 4:39 pm Post subject: PROBLEM. Electrical Grounding with a primed airframe.

I ran 2 wires and grounded to the engine Mount. My battery is  also behind the seat. I don't like the idea of using the airframe as the main  grounding point. If the plane didn't have a starter it would be fine but it does  so I think 2 wires is the way to go. 

 This was a rough pic of the battery and not finished but you get the  idea.

  

   

              

  



  

  In a message dated 11/22/2007 4:12:45 P.M. Eastern Standard Time,  stol10(at)comcast.net writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: "Geoff Heap"    <stol10(at)comcast.net>



I could use some advice or comment. Over the    years, as I built my airframe I primed everything just before    riveting/assembly. With the knowledge I have now that seems dumb. With the    battery behind the passenger seat how can I ground it back there. All airframe    parts are isolated from each other electrically. Will the rivets help me out?    Would they give me the continuity I need? Do I need to run  a ground wire    all the way back to the engine block?

             Lost in Lindenwold



912/dynon 180/icom-a210/garmin    296.





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=147968#147968

	




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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Nov 22, 2007 4:43 pm Post subject: PROBLEM. Electrical Grounding with a primed airframe.

You should run a separate ground cable from the battery negative

terminal to the engine block. Don't rely on the chassis ground to carry

the starting current to the engine.



On my plane, my battery is behind the passenger seat. I have a 4 gauge

wire from the negative terminal to a brass bolt passing though the

firewall. On the front side of the firewall a 4 gauge wire continues

from the brass bolt to the engine block. I also have a common grounding

terminal block at the point where the brass bolt passes through the

firewall. I got the brass bolt and terminal block from B & C Specialty

Products.



Geoff Heap wrote:

 	  Quote: 	
		   

 

 I could use some advice or comment. Over the years, as I built my airframe I primed everything just before riveting/assembly. With the knowledge I have now that seems dumb. With the battery behind the passenger seat how can I ground it back there. All airframe parts are isolated from each other electrically. Will the rivets help me out? Would they give me the continuity I need? Do I need to run  a ground wire all the way back to the engine block?

           Lost in Lindenwold

 

 912/dynon 180/icom-a210/garmin 296.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=147968#147968

 

 

 

 

 

 

 

 

 

 

 


	


-- 

Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

_________________
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Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Nov 22, 2007 4:47 pm Post subject: PROBLEM. Electrical Grounding with a primed airframe.

You should run a separate ground cable from the battery negative

terminal to the engine block. Don't rely on the chassis ground to carry

the starting current to the engine.



On my plane, my battery is behind the passenger seat. I have a 4 gauge

wire from the negative terminal to a brass bolt passing though the

firewall. On the front side of the firewall, a 4 gauge wire continues

from the brass bolt to the engine block. I also have a common grounding

terminal block at the point where the brass bolt passes through the

firewall. Most of my ground wires connect to this terminal block. I got

the brass bolt and terminal block from B & C Specialty Products.



Geoff Heap wrote:

 	  Quote: 	
		   

 

 I could use some advice or comment. Over the years, as I built my airframe I primed everything just before riveting/assembly. With the knowledge I have now that seems dumb. With the battery behind the passenger seat how can I ground it back there. All airframe parts are isolated from each other electrically. Will the rivets help me out? Would they give me the continuity I need? Do I need to run  a ground wire all the way back to the engine block?

           Lost in Lindenwold

 

 912/dynon 180/icom-a210/garmin 296.

 

 

 


	


-- 

Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

dougsnash(at)yahoo.com
Guest

Posted: Thu Nov 22, 2007 6:04 pm Post subject: PROBLEM. Electrical Grounding with a primed airframe.

Hey Geoff, I'm going to go a little farther than

everyone else in saying, run a groundwire for

everything.  Don't rely on the airframe for grounding

at all.  Yes this is more work now but it is still

easier than trying to track down a bad ground

somewhere later on.  It is especially important to

ground the strobes well as this will help eliminate

the zot, zot, zot in your headset as they run.



Personally, I have a bunch of the buss bar terminal

strips that Wicks sells on order.  I am going to have

a power buss and a return buss for everything.  Of

course I'm only building a day/night VFR equipped

CH-701 so the additional weight of the extra grouond

wire should not be excessive. If someone were building

a more complicated panel they might want to save the

weight.  But if that were the case, ,they would also

be looking for the redundancy as well.



Maybe I'm a little paranoid about the grounding issues

but I chase electrons for a living and they can be

tricky little devils at times.



Best of luck with your project.



Doug MacDonald

Industrial Electronics Tech.

CH-701 Scratch Builder

Fuse on gear, working on wings

NW Ontario, Canada.



Do Not Archive

 	  Quote: 	
		   I could use some advice or comment. Over the

 years, as I built my airframe I primed everything

 just before riveting/assembly. With the knowledge I

 have now that seems dumb. With the battery behind

 the passenger seat how can I ground it back there.

 All airframe parts are isolated from each other

 electrically. Will the rivets help me out? Would

 they give me the continuity I need? Do I need to run

  a ground wire all the way back to the engine block?

 >           Lost in Lindenwold

 > 

 > 912/dynon 180/icom-a210/garmin 296.

 > 


	


Never miss a thing.  Make Yahoo your home page. 

http://www.yahoo.com/r/hs

Geoff Heap

Joined: 12 Jan 2006
Posts: 266
Location: Lindenwold, New Jersey

Posted: Fri Nov 23, 2007 5:06 am Post subject: Re: PROBLEM. Electrical Grounding with a primed airframe.

As usual everyone came through. Thanks for the help. This is why I send Matt Draille 60 bucks every year. I have to go with the majority. I'm sure I wont regret having a better electrical system.

    Now the question becomes. How close can I have these two cables to each other? I'm assuming it would be a problem running them side by side....Geoff

Afterfxllc(at)aol.com
Guest

Posted: Fri Nov 23, 2007 7:12 am Post subject: PROBLEM. Electrical Grounding with a primed airframe.

I run both of them on the right side and tuck them into the trim below the  canopy arm. Then run the ground to the engine mount and then ground the mount to  the engine. I also run the starter relay on the inside of the firewall so the  only high voltage that passes thru the firewall is when the starter is  engaged.

  

 Jeff

  

  In a message dated 11/23/2007 8:08:02 A.M. Eastern Standard Time,  stol10(at)comcast.net writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: "Geoff Heap"    <stol10(at)comcast.net>



As usual everyone came through. Thanks for    the help. This is why I send Matt Draille 60 bucks every year. I have to go    with the majority. I'm sure I wont regret having a better electrical    system.

    Now the question becomes. How close can I have these    two cables to each other? I'm assuming it would be a problem running them side    by side....Geoff





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  [quote][b]

dredmoody(at)cox.net
Guest

Posted: Fri Nov 23, 2007 10:44 am Post subject: PROBLEM. Electrical Grounding with a primed airframe.

The rivets ought to do the job. To test whether or  not you have continuity through the airframe, use a charged battery and a long  jumper wire (14 - 16 AWG). Clip the jumper wire to the formed head of a  rivet the rear of the fuselage. Connect the other end of the wire to  one lead of a multimeter and check continuity to some part of the airframe  near the firewall. If you don't have decent continuity, you may have to install  a ground buss back in the aft section and run a heavy wire (12 - 14 AWG) all the  way back to the firewall area ground buss.

  

 All my airframe parts have been either primed or  primed and painted as I assembled the plane and I have continuity through out my  airframe so I doubt that you'll have a problem.

  

 Dred

 [quote]   ---

dredmoody(at)cox.net
Guest

Posted: Fri Nov 23, 2007 10:47 am Post subject: PROBLEM. Electrical Grounding with a primed airframe.

Good for lights..... not good for the strobes,  strobe driver, or electrical motors. Those tend to be electrically noisy and  should have a dedicted shielded ground wire with the shield grounded at one end  as near the engine as possible.

  

 Dred

 [quote]   ---

dredmoody(at)cox.net
Guest

Posted: Fri Nov 23, 2007 11:00 am Post subject: PROBLEM. Electrical Grounding with a primed airframe.

Might be good to run them as a twisted pair.  Electronic gurus on the list can confirm or correct.

  

 Dred

 [quote]   ---

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Sat Nov 24, 2007 10:40 am Post subject: Re: PROBLEM. Electrical Grounding with a primed airframe.

I don't know if you follow Bob Nucholls stuff in the Aeroelectric section, but this topic has come up there numerous times. I'm no electrical expert so I can only say what I have done and what experts like Bob have recommended. Basically with an aluminum airframe there is no reason to run a ground cable forward to the firewall. There is enough contact with the rivets, even if everything is primed, to provide an ample path for the electrons to flow. You'll find more resistance in a 2 G cable than you'll see in the airframe. You can also safely ground pitot heat, landing lights, and position lights locally.

s.c.richards(at)homecall.
Guest

Posted: Mon Nov 26, 2007 2:45 am Post subject: PROBLEM. Electrical Grounding with a primed airframe.

Hi Geoff

                    In Rays 601 HD we ran two cables 4AWG together under 

left longeron section below canopy, negative ground bolted to shelf in front 

of fire wall with strap to engine & a wire to common panel ground. Master 

Contactor near battery in rear. Did not fancy starting current passing 

though rivets. The avionics alternative feed was fed from a small fuse near 

battery. Other circuits we ran a + & - together Intercom & aerial cables we 

ran on right hand side

           Should have used 2 AWG to reduce volts drop but this is heavy. so 

we keep the battery float charged & it starts OK.

G CBDG Continental 0-200  179 Hrs



Clive

Do not archive

---

billmileski

Joined: 07 Aug 2006
Posts: 68
Location: Ledyard, CT

Posted: Mon Nov 26, 2007 7:20 am Post subject: Re: PROBLEM. Electrical Grounding with a primed airframe.

I have a 701 with a 912S, and a battery behind the access panel in the bottom of the rear fuse.  The battery is grounded to the airframe nearby, with a ring lug and AN3, with primer cleaned off with thinner first.  Even with the old 912 starter (not new high torque one) the engine spins up quickly at start, year-round, and I would think this is preferable to the weight and complexity of the additional ground cable.



The strobe power supplies are at the wing tips, and their +12V power wires are unshielded. The output to the strobes, however, is shielded, which seems to make sense, as this is the high voltage transient signal.  That said, I do hear a very slight whine of the power supplies charging, in the headsets.



Bill Mileski

Ledyard, CT

701 912S 114hrs

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