Mailing List flyrotary@lancaironline.net Message #10286
From: Bob White <bob@bob-white.com>
Subject: Re: [FlyRotary] returnless fuel system
Date: Tue, 10 Aug 2004 06:55:59 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Hi Todd,

I haven't seen Jim Weir's conversion circuit, but it seems to me that
when the tank is empty it wouldn't matter what fuel was in it, so what
you need is a pot to adjust full scale when you fill the tank.  There
may be a little shift in the zero when full is adjusted, but your
accuracy should be much better.

Congratulations on the new family member, and best wishes for a good
nights sleep.

Bob White

On Tue, 10 Aug 2004 00:39:40 -0700
"Todd Bartrim" <haywire@telus.net> wrote:

    First I'd like to thank everybody for their congrats on & offline,
everybody is still doing fine, but sleep is still at a premium.
Definitely no time for flying :-(, maybe in a few days.  No jump seat
in the 9 yet, but I'm already planning it :-)

    Second I need to say that even though I seem to have found a
    successful
fuel system, I do regret not adding fuel return fittings in each of my
6 tanks. A simple 1/4" bulkhead fitting with a cap is not too much
$$$, or weight and it will allow simple plumbing changes if ever
necessary. While I have 30 successful flight hours on my returnless
system, it is prudent to remember that I only have 30 flight hours on
my returnless system.:-). And none of this flight time was down south
where your idea of summer & winter are vastly different than up here
in the great white north. At this point I'd recommend that you install
return fittings while it's still easy to do. I wish I had, however if
I had I may not have ever tried this system and only went with a
conventional system. Even if my system continuous to be successful, if
I ever have a reason to remove my tanks, I will add return fittings
with caps.

    I may have this opportunity. I currently have capacitive fuel
    sensors,
which are read by an E.I.sensor. I bought the components to build a
converter as per Jim Weirs plans from a past KitPlanes article, in
order to display on the EM2 which needs a 0-5 volt signal. However I
find that auto fuel seems to vary in it's capacitance. When properly
calibrated they are very accurate, but put in fuel from another batch
and the readings are less accurate, put in fuel from the original
batch and they are accurate again. Start adding pre-mix fuel and of
coarse they're inaccurate again. I'm unsure if it is the fuel itself
that has dielectric variations or possibly the dye used to mark the
fuel as off-road use only? I've noticed that the purple colour seems
to vary as some batches seem to have almost no colour while others are
very dark.

    In any event, while I will still leave the capacitive probes in
    place, I
think I will order a set of float resistive sensors to display fuel
info on the EM2. If I do this I will add the return fittings and then
possibly I may add an electric fuel tank selector valve that I have,
except that it will be used to select fuel destination instead of
source. In it's normal un-energized state it will continue to operate
as a returnless system, but when energized it will return to a wing
tank. In the event of an unexpected vapour lock, I can just hit a
mom-on push button to return to a wing tank. My concern with this is
that these fuel tank selector valves are meant to be located on the
suction side of the fuel pump, so I'm unsure how well they would work
in the return line.

Bottom line... Install the return fittings while still it's easy!

Todd Bartrim        (trying to think of a way to burn diapers for
fuel)

RV9Endurance
13B Turbo Rotary
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

             "The world will always have a place for those that bring
             hard
work and determination to the things they do."




--
http://www.bob-white.com
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