Valve flow rating / Auto Cycle valve

[rogerfries]

Several of you guys have posted that you have auto cycle valves on your splitters. I have a question about them or any valve for that matter. The Prince auto cycle valve is rated at 25 GPM. Does that mean that a 28 GPM pump or larger will be restricted down to 25 GPM? I want to build a splitter using a 6" bore piston. I will be using a VW Diesel engine to run this beast and I would like to get a large pump 28 GPM minimum, perhaps more, but If the valve only flows 25 GPM am I stuck there or will it flow more, but is only recommended for 25? What would happen If I used a 43 GPM pump and a 25 GPM valve? Would it be 25 or somewhere between 25 and 43?

Thanks!

 

[Mr. Firewood]

most valves are rated by the flow at 0PSI (free flow) however with a 40ish gallon pump into a 25 GPM valve it will form resistance and build pressure until the flow increases

btw 43 gpm would result in a 4-7 second cycle time in a 6" cylinder, you will never be able to keep up with that splitter

 

[rogerfries]

One of the cylinders I'm considering is a 6"x30" at 28 GPM it's cycle time should be 13.8 Sec. Which is OK, I'd rather have 10 seconds.
Another cylinder I'm considering is a 6.5e" x 40" at a full 40" stroke thats 22.3 seconds. Even if I limit the stroke to 30" it' s 16.7 seconds.
A 43 GPM pump should cycle the 6.5 x 40" in 14.3 seconds.
http://www.surpluscenter.com/item.asp?UID=2007010110441875&item=9-2e025-A&catname=hydraulic
This pump does 43 GPM at 1,800 RPM I would have to manually hit the second stage as it will probably stall my little diesel engine at about 1,000 PSI
The reason for the diesel engine is that this machine is going to double as a backup generator for the house. I'm going to put a 20K generator head on it. I also want to try to put a PTO on it so I can drive other devices like maybe a PTO chipper. This diesel can rev up to the 3,600 RPM no problem, but I don't want to rev it that high. I want to run it between 1,800 - 2,500. This engine should make 33 HP at 2,500 RPM. Does anybody make a 2 stage pump larger than 28 GPM?

 

[CylinderService]

Treeco is right about being able to force more than 25 GPM though an autocycle valve, but you may have problems with the detents kicking out midstroke from too much backpressure. And the extra resistance in the valve and lines, fittings, etc from putting too much flow through too-small components will waste power and create lots of heat.
However, the 28 GPM pump only puts out 28 GPM at 3600 RPM. So you may have less flow to worry about than it first appears.
The Dowty 43 GPM double pump would need a bypass and check valve system attached to function as a 2-stage pump, but it could be done if you have the money. By the way, I think the Dowty pumps have been obsolete for at least 10 years.
Prince does make a larger 2-stage pump, but it’s pricey ($700?). Let me know if you want details.

Don the Hydraulics Guy

 

[rogerfries]

No doubt the 2 stage pump is the best, I just wish there was one that flowed more at a lower RPM. As for manually hitting the second stage, It should only be necessary on the monster logs. This big 6.5" cylinder makes more power at 1,000 PSI than my 4" makes at 2,500 PSI. The down side, if the operator does not hit the valves at the right time the engine will stall and need to be restarted.

Perhaps running 2 of the 28's in parallel is the answer. I can buy one and if it's too slow, buy a second one when the cash supply allows. The only problem is that I don't think any of thr 2 stage pumps are stackable, I would be forced to belt drive it. Does anybody know how much horsepower can be belt driven?

 

[CylinderService]

Roger,
2-stage pumps don't have the shaft strength or bearings to be belt driven. You would have to run the belt to a jackshaft and run the pump off the end of that. With a big enough belt (or 2) you could transmit the Hp.

Don

 

[rogerfries]

Don,

Are you saying that with a bypass and a check valve, This double pump will act as a 2 stage? Ah Ha, so obvious I guess that's all a 2 stage pump is doing. I think that's my solution. I would however be interested in that larger prince pump depending on the price/specs.

Thank's Sooo much

 

[CylinderService]

Roger,
I guess I spoke too soon - Prince's largest 2-stage pump is about 31 GPM. You could use a double pump and we handle a "hi-low" valve which includes the bypass, check valve and relief all in one package. These could go to 40 GPM or more, and could be big enough to drive at a lower RPM. You're probably looking at 800 or so for both the pump & valve. If you want me to get details, contact me at [email protected].

Don

 

[CylinderService]

Don it seems to me listening to my 18hp Briggs running at about 2400 rpm driving a 28gpm pump that a little extra flywheel weight would really improve performance. I'm just saying that because I hear the governor kick in under load and it seems increased moving mass would really smooth things out for the engine. The biggest surge load on the engine is not when it kicks into low flow but instead is when it kicks back into high flow. In low flow the engine drives the load almost effortlessly. Of course the complications introduced by a small flywheel are many.

This engine has been on this machine since 1990 and still runs just fine but if I do ever need to replace it I will most like go smaller as I can see 18hp is still quite a bit of overkill. I bet a little flywheel on a 12 or 14hp engine would really work well and save fuel in the long run.

Treeco,
It sounds like the bypass setting for the large pump is set a little high for your engine. I don't think that's adjustable though. A flywheel might help if the overload is only momentary, but I don't have any experience adding flywheels to engines. I agree that you might have other problems as side-effects.

Don

 

[SWI Don]

Don, (CylinderService)

What is the adjustment screw on the side of the Barnes two stage pumps for? I figured it was the adjustment for the step down pressure.

Don,

 

[CylinderService]

SWI Don,
Yeah, the side valve on the Barnes pump is the low pressure bypass. I just don't recommend people mess with it. If it's set too high it might increase the torque requirement to where the shaft breaks.

Don