REFLECTOR: Oil lines and ground wire.
Al Gietzen
ALVentures at cox.net
Sat Sep 3 13:30:51 CDT 2005
Scott;
Don't know why, but I get different numbers than Larry. The tube wall area
is about .14 in. sq (equivalent to about .29" solid wire). The resistance
of aluminum (2.8 microhm-cm) is about 1.65 times as high as copper (1.7
microhm-cm). One tube would be equivalent to about a 5 AWG copper wire, and
two tubes would be equivalent to 2 AWG copper.
Unless I got something wrong, that would make an adequate ground return,
assuming you could get a good connection at each end.
As far as running the lines in separate ducts it only helps by preventing
the return oil being heated by the in-coming oil, so separating (or
insulating) them in the same is just as good. If you have outside air
flowing through the ducts, you can get some additional cooling, but that has
some additional issues. The high pressure hose that is already in there has
walls that are somewhat insulating; and a good steel-braid covered line
could be more reliable than solid aluminum (not subject to vibration
fatigue).
FWIW,
Al
-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Saturday, September 03, 2005 7:04 AM
To: Velocity Aircraft Owners and Builders list
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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