REFLECTOR: Oil lines and ground wire.

[Scott Derrick]

In spam cans, we use the entire airframe as a ground return, skin, 
spars, aluminum fuel lines and all..

I would envision a ground buss bar at both ends with a soldered braided 
line from the bars to the lines. Disconnecting  the flexible oil line at 
the engine or cooler would not effect the ground return path.

Scott

Douglas Holub wrote:

>.127" would be the radius. The diameter would be .254", or about 2 AWG.
>
>I personally shudder at the thought of running electricity through an oil
>line. I know oil is a good insulator, and transformers are filled with oil
>sometimes, but oil is flammable, and a spark at the wrong time would be a
>disaster. For example, if the oil line should become disconnected while the
>power was on, there could be intermittent sparks. Hot oil gushing into the
>airplane is a bad enough problem without it also catching on fire. Or maybe
>you're doing some maintenance in the hangar and disconnect the oil line
>while the power is on.
>
>I'm sure it could be done safely, but I think it's asking for trouble.
>
>Doug Holub
>
>----- Original Message -----
>From: "Laurence Coen" <lwcoen at hotmail.com>
>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>Sent: Saturday, September 03, 2005 11:19 AM
>Subject: Re: REFLECTOR: Oil lines and ground wire.
>
>
>  
>
>>Scott,
>>
>>As far as using the aluminum oil lines for a ground return, don't.  Their
>>ability to conduct electricity is a function of cross sectional area and
>>    
>>
>the
>  
>
>>material.  Aluminum has four times the resistance of copper for the same
>>cross section.  1/2" aluminum tubing has a wall thickness of 0.035".  I
>>calculated the cross sectional area and it is equivalent to a wire of
>>    
>>
>about
>  
>
>>0.12" dia.  That's far too small even if it were copper.
>>
>>The other question about up one side and down the other has been discussed
>>before and as a result I chose to do it that way.  I believe that someone
>>    
>>
>at
>  
>
>>the factory took measurements of temperature at both ends of both oil
>>    
>>
>lines.
>  
>
>>The lines were in the same duct.  The oil flowing foreword lost 20 deg. F
>>but the return oil was reheated 15 deg. F.  The two lines together were
>>acting as a counter flow heat exchanger.  At least in theory, moving the
>>return line to the other duct should make the oil entering the oil cooler
>>    
>>
>15
>  
>
>>deg. warmer thus increasing its' efficiency and getting perhaps another 5
>>deg. drop in the return line.  I've never had my oil lines in the same
>>    
>>
>duct
>  
>
>>so I am unable to test the theory.
>>
>>Larry Coen
>>N136LC
>>
>>----- Original Message -----
>>From: "Scott Derrick" <scott at tnstaafl.net>
>>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>>Sent: Saturday, September 03, 2005 10:04 AM
>>Subject: REFLECTOR: Oil lines and ground wire.
>>
>>
>>    
>>
>>>My plane came with high pressure hoses for oil lines. Both ran in the
>>>pilot side duct.  I noticed that the manual calls for 1/2 " aluminum
>>>lines.   I was considering replacing the high pressure rubber/steel flex
>>>lines with aluminum.  Much lighter and smaller, those hydraulic lines
>>>      
>>>
>are
>  
>
>>>huge and heavy.
>>>
>>>I was also considering running one up the pilot side and the other down
>>>the copilot side to take advantage of the additional cooling benefits.
>>>Has anybody done the comparison of running both in one duct and one in
>>>each to see if there really is an advantage?
>>>
>>>Then I got to thinking about using the oil lines for my ground return
>>>      
>>>
>path
>  
>
>>>from the battery to the engine?  Aluminum is a pretty good conductor,
>>>      
>>>
>and
>  
>
>>>having two lines would seem to provide a substantial return path if I
>>>bonded both tubes at both ends?
>>>Anybody do this?
>>>
>>>Scott
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