On Aug 6, 12:14 am, HC wrote:
Hello, all.

Here's what I have:

- 8 HP Briggs & Stratton IC engine
- Haldex/Barnes 16 GPM direct drive hydraulic pump
- Prince "Logsplitter" vavlve (like can be seen hehttp://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_47..."
- 4 inch bore, 30 inch stroke cylinder
- 3.5 inch bore, 36 inch stroke cylinder

What works:
The engine, hydraulic pump, valve, and 4x30 cylinder are used as a log
splitter. Work great. No problems.

What does't work:
I disconnected the 4x30 cylinder and connected a 3.5 x 36 bore
cylinder for another project (with about 10 feet of hydraulic hose I
can use the logsplitter as a power supply for other hydraulic
projects, which is what I'm doing). Whereas on the logsplitter ram-
speed is not a concern, my current project is sensitive to ram speed.
When I move the handle of the spool slightly to move the ram at low
speed the ram moves very slowly, no problem, until it hits the load
and then the engine bogs and dies. However, when I move the handle to
full-open against the load the ram moves just fine, but way too fast
for my needs and control.

The problem is that I need to be able to control the speed of the
hydraulic ram in my current project but when I try to move the handle
of the vavle slightly, to move the ram slowly, it bogs the engine and
will kill it, under load.

It's got to be the valve or the pump, but I don't know enough about
these things to be sure which it is. I would guess the valve is the
problem, maybe restricting the fluid too much on partial
engagement....but I don't really understand the inner workings of
these things well enough to even form a theory.

Any help would be appreciated.

Thank you.

--HC

I finally found that the Haldex/Barnes 2 stage pump I have (the 16 GPM
model) has a large-volume pump of, I don't remember the exact figure,
but it's about 0.7 cubic inches...maybe 0.756 or so. The small-volume
pump is, and this I remember accurately, is 0.258 cubic inches. So,
with that knowledge I bough the smallest pump that I could find from
my supplier that used the same shaft, rotation, and mounting as the 16
GPM two stage. That pump has a 0.194 cubic inch displacement. I
rigged it up on the engine and to my assemblies and ran it with NO
problems at all, even at full pressure, 2,250 PSI. The engine did not
lug or bog at all! I then adjusted the bypass on the valve to a
higher pressure. Not knowing how fine the adjustment would be I
attempted a half rotation on the adjustment and then applied pressure
to the cylinder. It ran over 3,000 PSI and I immediately let off the
valve to return to center. But the engine had no problem with that
pressure. I adjusted it finally to 2,750 PSI on the bypass, 250 PSI
over the max working limit of the cylinder otherwise I'd set it to
3,000 PSI, and left it there. I can run the cylinder to load and stop
the cylinder, with 2,750 PSI on the gauge, and the engine runs fine.
So, either going from a 0.258 CI pump to a 0.194 CI pump really makes
that much difference (it's a 25% reduction in volume) OR the two stage
pump wasn't properly (if it ever would or could) shutting off the
large-volume pump portion. I have a hard time thinking the 0.258 CI
would KILL the engine at a load of 2,250 PSI and that the 0.194 CI
pump wouldn't even bog it at over 3,000 PSI. I think that two stage
pump is okay for a log splitter where there is no way a log is going
to be able to resist any where near 2,250 PSI on a 4 inch bore
cylinder and therefore won't ever really load the engine down, but is
a poor choice for where full power operation may be necessary.

Thanks again for all your help and input. I hope the results above
will help somebody else.

--HC