Regenerative Log-splitter Bi-Directional Circuit

[N8ghz]

Here is a circuit diagram of a circuit I intend to experiment with. This diagram is showing the circuit with the main valve centered, and the regen valve de-energized....with oil going to Tank as it would normally. The gauge on the P line is showing 0 PSI or a no restriction circulitory P to T flow. When the main valve is shifted to split, the machine would run the way it does before adding the regen valve and the (2) Tees with check valve. My main valve is a manual lever-type with detent pop-off on return, (not the solenoid type shown). I intend to use a solenoid N.O. valve for the added valve and add a tab on my main valve handle to add a N.O. momentary push-button that I can push as desired, with my thumb, to energize that valve,which will block the oil to the Tank and send it to the P thru the check valve, thus allowing regen to occur. This should allow me to rapidly extend and then release the button when nearing the log. It should also allow me to rapidly Retract (which will be faster than the regen Extend) and release the button wherever needed to set up for next split. I see no problem putting it into detent, pressing my button, and releasing the button just before it fully retracts, so as to have enough pressure to pop to neutral as it normally would do without the regen circuit.....and that is only IF I needed to fully retract which with similar length logs would not be an issue.

BTW, the 1000 PSI relief will be 1500 and the GPM will be lower than 10 for my test (tractor just above idle). This on a 3-point splitter with a 4"x24" cylinder with a 2" rod.

I am not mentioning hose/fitting sizes, as I do intend to move to 3/4", but am going to try it using 1/2" to see what it looks like in operation.

What do you think?

Here is the drawing:

 

[J_J]

The regen pressure on the retract might not be enough to operate the detent kick off to neutral.

Some are adjustable.

 

[N8ghz]

Yes, that is what I think too. However, with logs shorter than requiring full stroke, I should not have a problem, as I would stop before it ever went all the way back. Of course, if you wanted to do that, you could put it in retract and walk away. The regen button would be N.O, and thus no regen.

 

[J_J]

I have seen kick back to neutral as low as 600 psi.

Cyl regen.

http://www.hwhcorp.com/ml37939.pdf

Regenerative hydraulic circuits, in Hydraulic double acting cylinders. - Practical Hydraulics (Hidraulica Practica) - Find Information on Components, Manufacturers, Applications, Articles, Videos, Calculators, Formulas. Fluid Power at hand.

 

[oldnslo]

As an option I believe sun hydraulics makes a mechanical regen system that operates on pressure so no electrical switch is required. Not sure about the cost though.

 

[SPYDERLK]

How can regen work on retract? Pressure on the piston side must always be lower for it to retract. If it is even near the same on both sides it will extend because the pisto side has greater area. I think regen will cause extension even if you have the main valve calling for retract.
larry

 

[N8ghz]

That is a good question. I am hoping the check valve will take care of that, we shall see.

The more I think about it, I don't believe it will work retracting.

 

[oldnslo]

That is a good question. I am hoping the check valve will take care of that, we shall see.

The more I think about it, I don't believe it will work retracting.

It will not work on retract.

Not to rain on your parade but with a cylinder ratio of 1.33:1 it will be difficult to make regen work on extend also. Regen works best when cylinder ratio's are 1.8:1 or higher. I would suggest retracting the cylinder and then tie both cylinder ports common and install a gauge, then try to extend like regen mode just to see if it will work. Look at what your pressure does while in regen mode.

Reason being is that you only have 3.14 sq inches of area to extend the cylinder. Any back pressure from line losses, pressure drop through valves, fittings, etc. add up to make the whole system work real hard and do no work.

The reason regen works on the tilt cylinders of FEL's is the over hanging load helps extend the cylinder.

Roy

 

[kennyd]

The reason regen works on the tilt cylinders of FEL's is the over hanging load helps extend the cylinder.

Roy

I agree 100% Roy.
I have been thinking about this since he posted it-but could not wrap my head around how it could work. I know in cases like when a cylinder is used for chute rotation on a snowblower the regen will just cause the cylinder to lock-up since there is no weight "pulling" on the cylinder.

 

[J_J]

http://www.hwhcorp.com/ml37939.pdf

 

[N8ghz]

I agree too now. This is a hard concept to get a grasp on. I had ignored the rod/bore ratio, as I can't really alter what I have. I added some calcs to my excel spreadsheet to figure ratios. To achieve near 2:1 I would need a 4x24x2.75 or so rod. And with an oversize rod, normal retract would be alot faster anyway. I attended a Bunyan festival last weekend, and saw a few processors that had 5" cylinders with 3.5" rods...they would have a good return speed with the pumps they used.

I now think that my experiment would be an exercise in futility with the cyl. I have.

 

[J_J]

What about the chance of using an accumulator to add to the volume of fluid going to the retract stroke.

If you had 5 GPM pump, and a full 1 gal accumulator and used them both to retract the cyl, what would be the outcome.

 

[N8ghz]

I have a bottle of nitrogen around here somewhere....might keep an eye out for an accumulator...projects,projects,projects....

Thanks for all input.

 

[oldnslo]

Accumulators are a bit difficult to apply on a free moving system like retracting a splitter. They want to dump all of their flow instantly. They also require some time to charge or fill with oil. I would be concerned about this since the charge time could / would add to your cycle time.

Roy

 

[J_J]

About the accumulator, would not a controlled release provide the right speed. The hose on the base end would have to be large enough for the increased velocity caused by the accumulator. The accumulator could charge up in the dead time/or neutral time.

 

[SPYDERLK]

I agree too now. This is a hard concept to get a grasp on. I had ignored the rod/bore ratio, as I can't really alter what I have. I added some calcs to my excel spreadsheet to figure ratios. To achieve near 2:1 I would need a 4x24x2.75 or so rod. And with an oversize rod, normal retract would be alot faster anyway. I attended a Bunyan festival last weekend, and saw a few processors that had 5" cylinders with 3.5" rods...they would have a good return speed with the pumps they used.

I now think that my experiment would be an exercise in futility with the cyl. I have.

Well, I dont. You have 3.14 times whatever pressure your system runs as your net extension force. Thats thousands of pounds to push an unloaded ram. All you really need is a valve between A and B that when activated closes off the B port to the main valve while simultaneously linking the AB lines going to the cylinder. Your engine will work hard sure, but the ram will move quickly as is your goal.
larry

 

[glastron23]

if you are trying to increase retract speed it would be a lot cheaper and less trial and error to just have a hydraulic shop build you a cylinder with a really big rod, we have some corner cranes with a 6 inch cylinder with a 5.5 rod. We only need the extend to have power, the retract is for stowing only.
To try and build a system that has regen on retract is a waste of time and energy. If people like Sun hydraulics, Prince and others can't get it then it's a lost cause.
Sun Hydraulics - Standard Valve Package

 

[glastron23]

Spyderlk.. if you close off the B port on the valve and then hook it to the A/B hoses from the cylinder together, how is the oil from the pump going to get to the rod side of the cylinder??

 

[oldnslo]

Well, I dont. You have 3.14 times whatever pressure your system runs as your net extension force. Thats thousands of pounds to push an unloaded ram. All you really need is a valve between A and B that when activated closes off the B port to the main valve while simultaneously linking the AB lines going to the cylinder. Your engine will work hard sure, but the ram will move quickly as is your goal.
larry

Larry,
problem with regen is that the rod end area of the cylinder is 9.42 square inches. So if there is 100 PSI in line loss from the rod end port to the cap end port it will require 3 x times that much pressure or 300 PSi pump pressure to extend. He only has 1000 PSI available and using 300 PSI in loss through the extra valves, hoses, etc may not be unreasonable. I never said it wouldn't work, just may not work as expected.

Roy

 

[SPYDERLK]

Spyderlk.. if you close off the B port on the valve and then hook it to the A/B hoses from the cylinder together, how is the oil from the pump going to get to the rod side of the cylinder??

This is only for extension. As you extend, oil is exiting from the rod side of the cyl. You essentially are connecting both cyl ports to "A" and applying the same pressure to both ends. The piston end has more area so the cyl trys to extend. If this extension encounters low resistance it extends. The fluid forced out of the rod end has nowhere to go but over to the piston end. This added fluid increases ram speed a lot. The cyl quickly moves toward its maximum volume condition [extends]. No fluid has to return to sump during this move so the B port is blocked by the same valve that simultaneously connects the cyl ends. After quick extension to the point it needs to do work this valve is put back to its normal position returning the system to standard operation.
larry