New loader valve not working properly

[oldnslo]

I suspect Struck advertising is an error. With the 31 HP they can either run the drive/propel system at 3000 PSI or the attachment system at 3000 PSI not both at the same time which is what the single pump system that jd put together is trying to do all the time.

For JD to get speed an lift he desires he needs to go with either two speed motors, double pumps, pressure compensated piston pump with HP control. or a combination of the above.
The pressure comp piston pump would give him the best performance under all conditions but they are expensive. I.e max drive torque and max lift simultaneously.
2-speed motor would give him speed at loss of torque.
double pump would give him propel torque or attachment lift force but not both simultaneously

single pump and flow divider gives him travel speed but limited torque and limited attachment force.

 

[J_J]

I called Struck, and they could not explain anything to my satisfaction.

Anyway back to the original problem, I see no reason for the loader valve to malfunction.

However, if the drive is being powered, and then you move the loader valves, the pump will try and stall as you have used up the available HP.

Now, if there is 0 travel on the drive motors, and you use the loader, the engine should not stall.

A hyd gage and pressure readings might be somewhat helpful, and a flow test into a bucket for the motor spools and the loader valve under different conditions, would be good.

What I am not sure of is, what is the flow rate and pressure on the 7 GPM of the divider when the pump is working at max for the drive circuit, at 3000 psi.

Which circuit is using the constant flow port on the divider? Drive circuit or loader?

 

[oldnslo]

Anyway back to the original problem, I see no reason for the loader valve to malfunction.

However, if the drive is being powered, and then you move the loader valves, the pump will try and stall as you have used up the available HP.

Now, if there is 0 travel on the drive motors, and you use the loader, the engine should not stall.

A hyd gage and pressure readings might be somewhat helpful, and a flow test into a bucket for the motor spools and the loader valve under different conditions, would be good.

What I am not sure of is, what is the flow rate and pressure on the 7 GPM of the divider when the pump is working at max for the drive circuit, at 3000 psi.

Which circuit is using the constant flow port on the divider? Drive circuit or loader?

Since this is one large fixed pump the pump will see whatever pressure is required to do the highest demand. Flow divider will require some pressure drop to function so this is also added to the required pressure. Installing a gauge at the pump outlet and the FEL valve inlet would provide the loss between these two points. I would suspect a minimum of 200 PSI and possibly as much as 500 PSI.

Operating the FEL requires xxx amount of pressure and this would be added to the required system pressure on all of the pump output. I believe we have calculated around 1500 PSI is the max pressure JD can run before stalling his motor. I suspect between the valve and line losses he is probably seeing this much loss while raising the FEL causing the engine to stall or strain. I know on my little tractor it takes around 500 PSI to raise the FEL MT.

Time the cylinder movement and if cylinder sizes are known we can calculate approximate flow rate.

 

[jd4310man]

J_J, The Loader valve is being fed by the constant flow port of the divider valve. I think we are getting somewhere here. I been comparing their specs to arrive at my pump size and flow requirements. Obviously they know something we dont. I figured that if they can run 23gpm from a 31 hp gas engine, Then I should be able to do near the same with my diesel. Anyway, I think all my loader problems are coming back to the fact that I have way too big a pump and the flow requirements are too great for the set pressures. Let me ask you this, what is the best approach to running this thing with a single pump and have enough flow to run all the functions of this machine with the power I have available? If you look at their model 4800, they are using one pump to run all functions. Im not sure if they are using a flow divider or not. I just want this thing to be function properly and have enough power to dig. The 4800 with the 12gpm pump runs just under 2mph and has no overdrive. 2mph regular drive would be fine, but I would like to retain the overdrive function too.

 

[oldnslo]

J_J, The Loader valve is being fed by the constant flow port of the divider valve. I think we are getting somewhere here. I been comparing their specs to arrive at my pump size and flow requirements. Obviously they know something we dont. I figured that if they can run 23gpm from a 31 hp gas engine, Then I should be able to do near the same with my diesel. Anyway, I think all my loader problems are coming back to the fact that I have way too big a pump and the flow requirements are too great for the set pressures. Let me ask you this, what is the best approach to running this thing with a single pump and have enough flow to run all the functions of this machine with the power I have available? If you look at their model 4800, they are using one pump to run all functions. Im not sure if they are using a flow divider or not. I just want this thing to be function properly and have enough power to dig. The 4800 with the 12gpm pump runs just under 2mph and has no overdrive. 2mph regular drive would be fine, but I would like to retain the overdrive function too.

JD,
You have to determine what pressure is required to operate your loader and propel your machine. Then you can back figure the pump size that you can drive with your motor.

as a reference: With 23 HP you can run around 12.5 GPM @ 2750 PSI. More flow = less pressure

HP = (GPM x PSI) / 1500 this allows for around 85% efficiency

 

[J_J]

I think Struck is fudging the figures, similar to the log splitter manufactures bragging about the tonnage.

I believe you simply need more HP.

You can run the machine with what you have, but with constraints.

The pump with the engine running at max, 3000 rpm, can pump 16 GPM with no load

If your motor valves are set for 3000, and the motors are 3500 psi motors, they will try and develop the the HP with the GPM's and pressure available.

Even though the pump, running at 3000 rpm will pump 16 GPM's, the engine will start to stall at about 12 GPM's with the motors working at 3000 psi trying to drive the machine up to the stall speed.

You can go to a smaller pump, and produce less GPM, but if the relief valves are set to 3000 psi, you will still have the power for the drive, just less speed, and have power for the loader.

You could go to a larger engine and not stall with that pump.

Your power is derived from the pressure and the speed from the GPM.

A good flow meter would be a big help in your situation, and show what is actually happening with the flow and pressure.

The loader only needs about 3 GPM 's at 3000 to do work. More GPM's, only increases speed of operation.

 

[jd4310man]

The Loader valve is set at 2000 psi. I get what your saying about flow and pressure. I either want to get a smaller pump or redesign the pump mount to allow the use of two separate pumps. The room I have to work with is a problem and limits what I am able to do with pumps and hoses. I was thinking about the priority flow divider, what if I make the priority flow to the track valve and set it to put out 12 gpm to the drive motors, and then whats left over to run everything else? I dont think it takes much power to run the loader or any of the cylinders as it does the drive motors. If I get a 16gpm pump and run 10gpm to the priority flow side and the rest to attachments, Would that work better? Im going to contact Struck and see if I can get a hydraulic diagram of the 4800 and see how they used a one pump system.

 

[jd4310man]

Thought I would post an update to this thread. I did replace the hydraulic pump with a smaller one than I first installed. The speed is a bit slower that before, but it now has plenty of power to dig and work the loader. The 21 GPM pump was just too much even with the flow divider in place. I can now use all functions of the loader without staling the engine. The new pump is a 1.35 CU In displacement at 17 GPM at full 3000 RPM. The factory twin pump set up is ideal to get the most of the available HP. One larger pump does take a bit more power to run. Here is a pic of the new loader valve installed. It is so much nicer to use than the factory single lever stack valve.