New loader valve not working properly

[J_J]

Was the original purpose of hose 510 from the loader valve to add flow to the drive motor circuits?

It tees up with hose 513 and looks like is adds flow to the input of the motor valves.

Is hose 510 now coming from the stacked valve using the single work port?

The HP necessary to run a pump is derived from the pressure desired and the GPM which is determined by the pump displacement and the rpm of the pump.

If you run out of HP, then you have to reduce the pressure or the GPM.

You are trying to transfer power and the hyd motors will develop the HP at about 85% efficiency.

12 GPM at 2800 psi = 23 HP

17 GPM at 2000 psi = 23 HP

20 GPM at 1700 psi = 23 HP

The 12 GPM pump will provide the most power from the above figures at the available HP, but at a reduced speed.

http://www.mgbryan.com/shop_image/product/Hatz-2G40-SS.pdf

Your max torque is around 2200 rpm, but if you run the engine at say 1800 rpm, the HP is about halved.

I believe a .9 cu in pump will use all of the 23 HP and pump 12 GPM, and have a pressure of 2800 psi.

So the hyd motors working at 85 % efficiency will develop about 19.55 HP

 

[jd4310man]

Yes hose 510 is still in place, I did not change that. OK, 12gpm seams to be the magic number for the hp rating. .900 cu in pump is a bit smaller than than the combined displacement of the two original pumps. The original track drive pump was .730 cu in, and the attachment pump was .509 cu in. So would it be safe to say that I could use a single pump of 1.200 cu in displacement? Is there less power required to run two pumps compared to one larger one? Looks like I have no choice but get a smaller pump anyway.

 

[J_J]

Your 23 HP engine, turning at 3000 rpm will pump 16 GPM's using a 1.2 cu in pump with the relief set to 2100 psi.

You can split that flow ever how you want.

But again, do you want power or speed?

Using two pumps, the displacement of the two pumps just add together.

Example:

Two pumps with .5 cu in each at 3000 rpm = 1 cu in = 12 GPM.

A .5 cu in pump turning at 3000 rpm will pump 6 GPM each X two = 12 GPM.

 

[jd4310man]

Does the flow divider make any difference in regards to power requirements? If I gave an 18gpm pump and I divide the flow with the priority flow divider, and only 12gpm is going to track drive circuit and the rest is going to the loader valves, would it provide the same affect as only having the 12gpm pump? Im not using the loader as much as the drive circuit.

 

[J_J]

If you do not use the loader valve , the fluid is just passing through the valve to tank and the flow is wasted.

However, if you activate that one SA spool lever, you add that flow to the drive circuit.

18 GPM, at 1800 psi = 23 HP

My thoughts on a situation like this would be to figure out the speed and torque you want for the drive.

Then use the displacement of the hyd motors to see how many GPM you need and how much pressure to operate the motors.

You know the cu in of the hyd motors, so based on the GPM which equals speed and the operating pressure, you figure the pump size you need in cu in, and then the HP required to drive it.

You have to compromise now using the 23 HP motor as to pump size and pressure.

The hyd motors can only develop the HP and speed if the pressure and the GPM's is there.

A set pump flow is also used by the loader valve for short periods based on the divider valve.

You could also eliminate the divider valve and put all the valves in series.

However if the first valve is using all the flow, there is none left for the other functions.

What you do in that case is to not use full lever, and allow a small amount of fluid to go to the loader valve, and you could eliminate the stacked valve.

The flow might look like this. Pump to motor valve, then to loader valve, then to tank.

All the valves should have the GPM rating of the pump. A little off will not matter much.

 

[J_J]

Example for a hyd wheel motor computing HP, speed, torque.

Disp. 11.0 cu. in. / rev.
Motor Type Geroler
Pressure:
3000 PSI cont.
4000 PSI int.
Torque:
5098 in-lbs. cont.
6776 in-lbs. int.
Speed:
381 RPM cont.
477 RPM int.
Flow:
20 GPM cont.
25 GPM int.

Need a 20 GPM pump turning at 3000 rpm = 1.5 cu in

So if you run that flow through a 11 cu in wheel motor, up to 3000 psi,

That pump will require 41 HP to run it.

That one motor will turn about 420 rpm and develop HP about 15 % HP less than the engine HP, and have torque of 5098 in-lbs .

That is just for one motor.

If using two hyd motors one for each track, then that machine will need an engine of about 82 HP.

 

[jd4310man]

The engineers at CF Struck corp designed this machine, Magnatrac 5000 with a 20hp Kohler gas engine, a drive pump of .730 cu in, an attachment pump of .500 cu in. The two drive motors are 10.6 cu in. each. Regular drive is 2.4 mph and overdrive is 3.5 mph. This thing is slow! I can live with that but lack of power I cannot. Right now with the 1.78 cu in pump, it will move the tracks and work the loader but it doesn't have quite the power I need. I dont think putting all the valves in series without the use of the flow divider would work very well. if one side of the divider isnt being used, it isnt taking any power to run it. I like the idea of having dedicated flow to each circuit so there will be power where and when I need it.

 

[J_J]

A .730 cu in pump, and a .5 cu in pump for a total of 1.23 cu in pump running at 3600 rpm, will pump 18 GPM.

19 GPM at 1500 psi requires about 20 HP from the orig Kohler engine.



New pump, 1.78 cu in, at 3000 rpm will pump 23 GPM

23 GPM at 1450 psi will require about 23 HP

If the full flow splits between the two 10 cu in hyd motors, and if each motor gets 11.5 GPM, at 1450 psi, the torque is only about 2309 in lbs per motor.

Can you verify if those hyd motors are 1500 psi motors?

 

[jd4310man]

The motors are rated at 3500 max psi. The motor valve is set at 3000 psi. Any lower pressure and the motors would stall easy. I never touched the pressure relief on the track drive valve. Attached is the current specs from Struck.

 

[J_J]

Something is not right in Struck advertising.

Using the MH8000 as an example, they say a 31 hp engine can produce 23.5 GPM at 3000 psi.

However the formula says different.Horsepower Required to Drive a Hydraulic Pump Calculator

Insert pressure of 3000 psi, then 23.5 GPM for the MH8000 and you will see, that 48.39 HP is required.

A big difference

 

[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.