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Message
After reading Davies
Craig reply I'm considering a series installation as it would allow for
redundancy without the addition of another possible failure mode from the
T/flapper valve. My only concern is that I've worked hard to reduce or eliminate
all possible restrictions to my system and am loathe to introduce another by
having a standby pump in the line. However it would be simple for me to measure
any change as I have a flow meter.
Hi Todd. It does
sound like series is the way to go. Tell us more about this flow
meter. If adding a second pump for a backup, you'll have to
know immediately if the first one quits working. I'm thinking
that you will likely damage the engine, or at least lose a large amount of
coolant if you don't get the second pump on ASAP. Ideally, there
would be a downstream pressure switch, or something hooked into you flow
meter to turn on the second pump
automatically.
The other option is to
just run them all the time, which is probably what I'll plan to do.
The plan would
be to have a pressure sensor downstream of the pumps. During pre-flight,
before cranking the engine, I can turn each pump on by itself, and verify that I
hear it, and that it increases the pressure. Even with the engine running,
you may be able to see a slight drop in the pressure when turning the pumps off
one at a time. Of course, to see this... (whining about not having an
EM-2 deleted) :-)
FWIW, this is the same philosophy that I use
with my fuel pumps. I check them individually as a
pre-flight item, then run them both during flight. My reasoning for this
is to virtually eliminate the possibility of an in-flight fuel
pump emergency. I'd MUCH rather find out that one of my pumps
has died while I'm safely on the ground, than to experience the anxiety of
having the engine quit in flight. The other plus is eliminating emergency
checklist items. If all your backup systems are already running, and
the engine quits, you might as well just concentrate on landing dead
stick. The only downsides are a bit more current draw, and wear
and tear on the pumps. If the alt fails, I'll turn off one fuel pump,
and one EWP to save some energy. If I have to replace the pumps within a
few years, big deal. It'll be the cheapest thing I've done on
this plane :-)
Everything that I removed
from my old mechanical system totalled 12lbs, so even with an additional pump
weight is still half.
I figure the pump itself is the
majority of the weight. The housing is only supposed to weigh about
3.5 lbs, maybe 4 - 4.5 lbs with the bolts. My current thinking is
that I won't save that much weight by removing the water pump housing,
especially since you have to add an adapter fitting for the water flow to
the block, along with an alternator mount of some type. I'm
going to look into just covering the water pump hole with a plate, and keeping
the housing for all of it's other uses. This realization was the
key to allowing me to go ahead and order the
EWP's.
The other key was thinking of a
potential place to mount the pumps. (Warning, unusual idea
follows) I plan to keep my radiator below the engine,
and at the very rear of the engine compartment. This takes advantage
of space in the cowl that is normally used for air exit, and exhaust
pipes. The rear, bottom edge of the cowling in an RV is a
few inches below the bottom of the firewall. Van even recesses part
of the fuselage in this area as well, to create more of an
opening. My radiator will probably require that I lower the rear of
the stock cowl an inch or so on top of that. Now, this leaves me with a
pretty large space on the bottom of fuselage, just behind the cowling, that will eventually get
a fairing to cover it. I've tried to think of things to put here, but
since the rear radiator tank blocks most of the opening, I can't get any
significant size hose through here. (At this point, anyone who can
figure out what I'm going to propose, can have the next room in the
loony bin.)
Because I'm moving the new radiator
back as far as possible, the tank ends up being under the rear motor
mount tubing. I figure that makes it impossible to put hoses in or
out of that tank, so the plan was to make this a double pass radiator.
Now, the front tank will be two separate tanks, with water going into one,
and out of the other. All it will do in the rear tank is flow from
one side of the radiator to the other. (You're getting less points if you
figure it out now).
So now, I have a big space behind the
radiator, with full access to the end of the rear tank. I also have
no water pump. What if I make the rear tank two separate tanks, just like
the front tank is? Now, it's effectively two radiators, side by side (take
note evap guys). The plan, is to put the two EWPs in
series, in the empty space behind the radiator. I would draw water from
one of the rear tanks, and flow it back into the other tank, completing the
circuit.
OK, here's the part where you all
burst my balloon, and tell me why this won't work. Go ahead, take your
best shot :-)
Cheers,
Rusty (I hear sirens...and why are
the sleeves so long on this coat)
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