BTW one HP is 746 watts. At 14 volts with the alternator

running

that is 53 amps. In theory it does not take much HP to pump

water

at this flow rate and pressure. This is a stock Mazda
13B water pump. Any reduction in this flow rate risks
damaging the engine.


Paul Lamar

American Flyer wrote:

Has anyone tried measuring the current to the motor as an

indication

of HP? It might be easier than a mechanical measurement because
imbalance and vibration would probably not show up in the

readings.

The meter (assuming something like a digital clamp-on) would
naturally integrate out fast variations.

Harrison Young

With alternting current this is a loser, because of phase shift. If

you

can score a real wattmeter it then becomes a viable concept - Vance

American Flyer wrote:

Vance,

I agree that power factor is a problem, but if that motor is working
as hard as it sounds, it would begin to look fairly resistive
(i.e. little phase shift). I'd bet that you still get at least
as accurate a reading measuring current as with a mechanical device.
I wish I lived close to you guys, I'd bring over a power-meter
(AKA digital oscilloscope, current shunt, and software).

Harrison Young

Hi! Harrison! - My contention is that with my set up (now with Paul) was
using relatively little power - well under 1 hp with my 3hp motor. After
witnessing some runs, both Paul and I wonder why he an Bill were
blowing breakers. It would be nice to have a good DC motor
and we could dial up rpm and read power pretty directly. I have
some surplus perm mag DC motors of unknown origin, maybe I
will try some experiments with them - Vance

I am not sure I agree with Vance on that HP estimate yet. I need to balance that
motor around the pivot/shaft axis. Also we are still running the pump at a
modest 4500 RPM. It may start blowing the breakers when I get it
up to 6000 RPM using a larger pulley on the motor. Right now I am focused
on getting the NC mill to work and finishing the engine dyno. It will
be awhile before I can fool with the water pump dyno again. There is only
one of me.

Paul Lamar
 
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