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Robinson, Chad wrote:
In the meantime, I'd still love to hear from anybody who might have an elegant solution to a parallel arrangement, since I love the concept of being able to double the flow for critical times, such as while on the ground on a hot day, or during climbout, then shut the second pump off and have it act as a backup in case the first fails. 2 pumps == 4lbs, and the mechanical (no redundancy) is 10. Sounds attractive to me!
Are you telling us that you've built (or are building) an airplane and can't build a simple 2" valve?
----------------------------------------
-- --
----------------------- + + + + ---------------------
++ ****** ++
++ ****** ++ -> normal water flow ->
++ ****** ++
++ ****** ++
----------------------- + + + + ---------------------
-- --
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dash == aluminum tube
plus == screen
star == slug
A simple, hollowed out aluminum slug that is 'caged' in a tube. One end of the cage allows water to flow around and out. With reverse flow the slug slides into the intake end of the valve and stops flow. You don't have to have a perfect fit here. With 88 lpm, having a couple lpm backflow could only be noticed on climbout (and then only barely) which would probably be a good time to turn around and go back home.
This would be simple to construct, but I'd personally build a simple flapper valve out of some aluminum billet.
On the other hand, if you know that you're descending, and not using much power, you could use a pump speed controller to slow it down and require less juice. But the counter to that is that it's more workload for the pilot during a stressful time. Lots of tradeoffs.
The pump is on a controller that already does this for you.
--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber
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