In article 5lS_c.4605$vI2.1373@trnddc02,
"Jerry Martes" wrote:

[...]

My problems are associated with a poor decission I made in the design of
this little dyno. I wanted the drag on the load's rotation to be minimal.
So, I made the lines into and out of the pump as flexible as possible. I
thought the output hose could be "light weight" because it is such low
pressiure. My brother-in-law spent his life designing hydraulics for
Northrop. He told me storries about high pressure liquids punching small
holes in outlet hoses due to some caracteristic of high pressure pumps. I
thought -- Oh Sh*t. Since I have other things to occupy my time, I dropped
that dyno for a while.

Unless you wind it up really tight or kink it a hose rated for 6,000
PSI working pressure would have to be spiked up well over 6,000 PSI many
times before developing a pinhole. Even then it's not very likely.
Also, the pinhole leaks are easily contained with a plastic hose wrap.
It's just a plastic spiral that you can wrap around the hose to protect
it. It's heavy enough a pinhole leak isn't going to cut through it at
any realistic operating pressures. You'd just see a dribble of oil
coming out of it near the leak.
Are you trying to actually spin the pump around or do you just want
to let it rotate a few degrees to push on a strain gauge or some such?
If it's spinning around, then yeah, that's dangerous and crazy and I'd
stay away from it. But if only rotating a few degrees you can use stiff
hoses without hurting your measurements. You could also just use a
pressure gauge on the pump and correlate input torque to pump pressure.

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