"rijakits" <rijakits@cwpanama.net> wrote:
 
> maybe I missed it, but for what reason would you want to run electric waterpumps?
> There will never be a moment where you could shut down any or all for more than a few seconds, so saving fuel/power is not the reason. If you need a constant flow of water, why would you want to route the necessary energy from the engine/to the alternator/to the EWP, instead directly from the engine to the WP?

   You *don't* need a constant flow of water - or rather,
you don't need a constant _volume_ of water flow.  The
primary advantage of the EWP is that the flow rate can be
tailored to the *actual* cooling needs of the engine.  As
it turns out, a side benefit is that the actual needs of
the system at cruise demand much less power than the M_WP absorbs.

> Belt brakes what then? When was the last time a belt broke in your car? Redundancy? Buy/have it made a set of 2-belt pulleys and exchange the first belt at 400 hrs or 4 years whatever hits first. This way you have a new belt and an old one. If the old one ever brakes you the second one to keep you good until you get there. Change it anyway at 1000 hrs or 5 years.

   It doesn't work that way.  In my 30 years of experience -
full-time and part-time - as an auto mechanic, one of the
more common failure modes for belts is: one belt _breaks_,
then becomes entangled in one or more of the other belts,
resulting in another belt being driven off it's pulleys.

> Is there ANY vehicle out there that relies on an EWP for its cooling turnover - air, heavy industry, mining, trucking, boats, ships, anything? ........please forget about racing applications, except you're building a raceplane:)

   Why discount racing applications?  Racing is often the
crucible in which improvements in automotive - and other - technologies are proven.  Racing tends to be far more
stressful on components than "ordinary" use is.  Of course,
there has to be one notable exception: turbochargers.  Eh, John?  ;)

>...
> Back to the belts: Robinson Helicopters relies on belts to transmit 180hp and 280 hp. These belts are lightweight and easily last 2200 hrs or 10 years, additionally they are used as a clutch to engage the rotor, average about once every 1 1/2 hours of flight time! If electric drive would be that much better/lighter/cheaper/safer (pick any one or all!:) they would run it electric!!

   EWP is definitely not cheaper - just more efficient.  
Moreover, you are starting to compare pomegranits to peaches.  The primary issue wasn't reliability; it was
efficiency (within the boundaries of equivalent
reliability).

> Personally I think a dual belt set-up is more than enough, but if you want hardcore I'd do dual alternator/waterpump with dual belts (a total of 4 belts), but not electric!

   Personally, all that 4 belts does for me is quadruple
the opportunity for a belt failure to put me in the weeds.
I can see putting the alternator on a separate belt, in
the hope that the next belt failure _won't_ be one of those
which entangles the other belt(s). However, as you point
out below, belts are easily inspected/replaced as a
preventive maintenance item.  As belts go, a single
serpentine belt is more than sufficient for aviation-
quality reliability.

> Your alternator goes (and mostly it doesn't because of the belt, but burned circuits, diodes, voltage regulators, etc.), your EWP goes soon too! How long will your engine run on the battery which already supplies ignition/fuelinjection/fuelpump/radios/nav. Now you want to use another2-3 hp out of it? Well a bigger battery will need a heavier alternator!

   Wrong!  It isn't the bigger battery that requires a
larger alternator; it is the total system current
requirements.  There is an optimal rate for cramming
electrons back into a battery - faster than that isn't
better, it actually shortens the service life of the
battery.  

   Also, the failure rate for belts far exceeds those due
to your other listed causes.

> Besides it is way easier to check belts than to check the condition of an electric drive....
> I don't want to spoil the discussion, but it points into the wrong way safetywise!

   I disagree for two reasons.  (1) MTBF for belts is much
lower than for the pump mechanicals, electric or pulley-
driven.  (2) Redundancy for a pulley driven pump is much
harder to implement.  How do you plumb a second mechanical
pump?  (Hint: with *great* difficulty)

Be well,
Dale R.
COZY MkIV-R13B #1254