Pneumatic --> Hydraulic need Clippard MJTV 4 valve but for fluids.

[booshambo]

Hello,

Summary: I want to convert pneumatic 100 psi 3 cylinder (2 1.5 in 5 in stroke and one 1.5 in 3 in stroke) system
to hydraulic (water or atf or whatever works).

For this I need a suitable replacement for the current clippard MJTV 4 valve, which has 1/8 npt ports
for each of pressure in, extend and retract. It also has a two exhaust ports that vent to atmosphere.

I think I need a valve that is very small, (MJTV 4 is similar outline to a box of matches) has two toggle
positions (extend and retract) and has P, T, A and B ports to run double acting cylinders.

Advice and comments welcome.



Background

I have a running system that uses a pair of 100 psi compressors (very small, 24 vdc from an rv) to maintain a small tank
(about 5 in. diameter by 6 in.) that is used to extend or retract three 1.5 in diameter cylinders.

I'd like to be able to use a hand pump to operate the machine if power fails.

I rigged up a double acting hand pump (a fourth cylinder that is 3 in stroke, 1.5 in diameter) with some checkvalves and it is a
total nogo - can get to about 30 psi and force at handle goes excessive. (1.55 in**2 * 30psi = 46 pounds on the cylinder
shaft).

I replaced the pump cylinder with one that is 3/4 in diameter and I can get up to 41 psi (stroke effort is not bad at
all) but it takes 200 strokes (a stroke here is an extend and a retract of the pump). Target stroke count is
anything below 15 for full cycle (extend or regract) of the machine.

At this point I tried thinking (for the first time it seems) and it is now my belief that the compressibility of
the air and the compression ratio of the 3/4 in (pump) cylinder are causing me to put all that energy into compressing
air rather than moving the load. Sadly ALL that extra energy is thrown overboard immediately when reversing the
machine direction. An efficiency nightmare.

I then tested the theory by putting the switch (valve) and inlet lines of the pump into a jug of water. After fighting
a bit with getting the thing to purge a bit (not even completely purged in fact), I get
between 3.5 and 4 strokes to cycle the machine depending on direction.

Suddenly the virtue of fluid power became clear...

Wish I'd gone directly to the proper book.

Anyway, now I need a two way control valve and any advice one might have on a optimum fluid. I've heard of people
using ATF in pneumatic cylinders. Dexcool seems benign relative to corrosion. Very suggestible at this point.

Thanks
b

 

[booshambo]

Update: Clippard mjtv-5 is suitable and unlike the -4 has 1/8 npt ports for "exhaust" which are plumbed to tank if using oil.

Sorry for the bother but in case someone else is in need of this kind of thing...
Just got off the line with Clippard and to my surprise they work with oil or water as well and have a variant that has the "exhaust" ports tapped.

Regards,

b