Can I Use a Double Acting Valve with a Singe Acting Cylinder?

Iplayfarmer · Dec 3, 2020

I posted about my new Terratrac GT30 crawler over in the "Projects" forum. Now that the initial enthusiasm and congratulations have worn off it's time to start the work of making it into what I need. The machine came to me with an electric hydraulic pump mounted behind the seat... Think dump trailer type pump. Not only is the wiring WAY wrong for it, but I'm sure the duty cycle would be wholly unfit for doing any real work. I'm going to re-build the hydraulic system with a real, engine driven pump and a real valve. I'm sure I'll need help along the way, so expect regular questions here.

The pump is from Surplus Center... 0.82 Cubic Inch. it should give me somewhere around 6-8 gpm at working engine RPM.
I have an old Jacobsen golf course reel mower that I'm scavenging parts from. It has a 3 spool valve, lots of hoses, filter, tank, etc.

I have two problems at present that I need to figure out:

1) The pump "does not have an out board bearing to support the shaft adequately under side load (pulley or chain drive) conditions." I was planning to belt drive off the fan belt, so I'll need to include some kind of bearing. I think I can figure this one out.

2) The real question that I have right now is that the lift cylinders on the sides of the loader are single acting. My valve is set up for double acting cylinders. How do I use a double acting valve on a single acting cylinder? Is it as easy as just blocking off the port that I'm not using on that spool of the valve?

mrmikey · Dec 3, 2020

You don't want to block the unused port in the valve, the pump would go over pressure relief every time you operated the valve in that direction. Plumb the unused port on the valve to tank, that way when you're moving the valve in that direction, the oil is just going thru the valve, out the extra valve port and right back to tank. Not the most efficient way to use a valve but you've got to use what you've got.
Put a filter of some sort on the unused port on the cylinder to keep dirt out, a rear end vent for example......Mike

Industrial Toys · Dec 3, 2020

Cute little CRITTER. What's it's name?

Iplayfarmer · Dec 3, 2020

Industrial Toys said:
Cute little CRITTER. What's it's name?

No name yet... Unless you count my satisfied chuckle every time someone asks me about it.

Maybe I'll put the kids to work thinking of a name.

Iplayfarmer · Dec 3, 2020

Next thought. I've been looking on ebay, and I'm surprised how cheap some of these large cylinders are...
Hydraulic Cylinder For Loader Welded Double Acting 2" Bore 32" Stroke 2x32 928879752151 | eBay

It may be worth it to just buy the double acting cylinders and have down pressure. Does anyone have experience with these cheap cylinders? Are the SAE8 fittings hard to find or work with?

Industrial Toys · Dec 3, 2020

Friend once leant me a 2 cyl Deere Dozer for the Summer. Great Fun. Amazing what it could push. No worry about thornes in Tires.

If you ever loose a track, you will wish you had down pressure.

mrmikey · Dec 3, 2020

SAE and JIC share the same thread pitch, just the seat angle is different, SAE is 45°, JIC is 37°. I think the SAE is more common for low pressure fittings. Me, I'd go with the JIC but to each his own. Saying that, you can get an adaptor to screw into the cylinder and change it to whatever you want to use for a hose end.

If you ever loose a track, you will wish you had down pressure.

Good point.......Mike

TMGT · Dec 3, 2020

mrmikey said:
SAE and JIC share the same thread pitch, just the seat angle is different, SAE is 45°, JIC is 37°. I think the SAE is more common for low pressure fittings. Me, I'd go with the JIC but to each his own. Saying that, you can get an adaptor to screw into the cylinder and change it to whatever you want to use for a hose end.

Good point.......Mike

That cylinder uses SAE o-ring fittings, no taper seal.

The SAE fittings are very common in cylinders, no problem finding fittings.

This is the style adaptor that is common for going from cylinder to hose.

TMGT · Dec 3, 2020

Thats a cool little crawler, I have a Oliver OC3 that I one day hope to restore.

On mine the hyd. pump is driven directly off the front of the crank, not sure if you'd be able to do that on yours. Mine has a heavy duty grill that allows a little more room for the pump.