"B.B." u wrote in message
news
In article gIw_c.2426$j62.422@trnddc04,
"Jerry Martes" wrote:

[...]

Anyone know about web resources for different approaches?


Thanks,

Jon Anderson

I had a teacher who built a dyno with a hydraulic pump & a flow
meter. He'd use a valve to build up back pressure and monitor the
flow.
After allowing for pump efficiency he could calculate the horsepower
running through the system. Knowing pump displacement he could
calculate RPM.
Simple and scalable to just about any size you need.

--
B.B. --I am not a goat! thegoat4 at airmail.net

BB

I've got a little pump-dyno here where I mounted the pump so it is free
to
rotate. Then, when the flow is restricted, the pump tries to rotate.
When I measure the torque imposed on the pump and the shaft RPM, I assume
I
can calculate HP with Excel. But, the idea of several GPM at a thousnd +
PSI scares me enough that I dont want to test it in the garage. I might
get courage to test it on a fractional HP motor. All the other dyno
loads
I've tried get too hot when loaded for even a few minutes. Water spray
helps extend the test run time, but even the water makes a little mess.

Jerry

I believe that if you measure only the torque load of the pump trying
to twist loose you'll only be able to calculate pressure--you would
still need to know flow rate coming out of the pump. I suppose if you
know the pump RPM and the pump's efficiency you could calculate the
flow. But you'd need to recalibrate your setup occasionally as the pump
wears.
If you're worried about the hydraulics blowing up you only need to
have pressure-rated hardware from the pump through the flow meter, to
the restricter valve. Outside of that area everything will stay
low-pressure. Many pumps come with a built-in relief valve so you can
set that to keep the system from exploding if you crank the valve down
all the way. And many flow meters come with a built-in restriction
valve, so you won't need to worry about that either.
The two dangers with a hydraulic system are pinhole leaks and a burst
throwing hardware. Use pressure-rated hardware and keep a relief valve
set slightly below the working pressures and you'll be fine. If you use
a large enough pump you could even do all of your dynoing at only a few
hundred PSI--but that gets somewhat expensive and less accurate.
I didn't study my teacher's dyno too closely, but from what I could
see he apparently used an old drum as a reservoir to allow the oil to
cool. It was actually quite a clean setup--I only saw oil residue
around the vent on the barrel.
FWIW he used his to test transmissions he built and had a chevy V8
driving them. His dyno never had a problem with high horsepower.

--
B.B.

BB

I dont know how to measure flow. I could probably learn But, I think
here is no need to measure flow in the hydraulic path in order to measure
motor HP. The pump is doing the work on the fluid. The motor supplies the
power to the pump. I wanted to know only how muvh work the motor is doing.
It is pretty essy to measure and record motor RPM. I figure the pump could
be mounted firmly and measure the motor's torque with the motor base free to
spin - or - Mount the motor firmly and allow the pump to rotate.
I'm pretty confidant the motor's HP can be calculated by measurement of
the pump's shaft RPM and the pump Torque.

Although I did get a pump and valve that are rated for the pressure I'd
generate, I got woried about the 1,500 PSI finding some way of making me
realize I had made some mistake. 1,500 PSI and 5 GPM of hydraulic oil could
make my garage look terrible. I'll test it outside whenever I do need to
load a motor for more than 5 or 10 minutes.

Jerry