"B.B." u wrote in message
news
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. --

BB

The motor is mounted firmly and the pump is mounted inside a big ball
bearing from a VW Bug transaxel. So, the pump's shaft is connected to the
motor's shaft and the pump body is free to rotate. The pump body is
restricted from rotating by a ~ 1 foot long bar.

I think you could have been a big help to me when I made this. My plan
was to keep the 'resistance to pump rotation' at a minimum so the residual
drag would be low and low HP could be recorded. So, I used some very low
pressure hose on the outlet.
I thought the spiking might be eliminated as a problem if the pump outlet
had a metal U at its outlet. I put the U at the pump outlet and stopped
working on the load since I got interested in the eddy current load at the
same time I was finishing the hydraulic pump load.
I'd bet that you could solve another problem I wonder about with this pump
load. I bagan to worry about how to get the oil to swiril properly in the
~ 5 gallon oil reservoir.

Note, all the dyno loads I've tried so far cant be used for more than a
few minutes at 5 HP without coolant spray. So, the hydraulic load would be
a good device for any "motor heat' testing. Thats why I havent disassembled
it yet.

Please let me know if you are available for information on how critical
the reservoir size and shape will be.

Thanks
Jerry