Speeding up hydraulics?

[mred2]

At the place I work, we sales big timber equipment. The saw heads are hydraulic. We have had problems for years, machines coming back in with blown hoses. People turning the pressure(flow?) up on the equipment. Much different systems from CUT's. But by turning the pressure up they think they will make it work faster. But all they do is break more. And with this equipment it can void the warranty. They want it to work faster, but they don't want to buy the bigger machine.

 

[FTG-05]

Nothing is going to help the problem but buying and fitting a pump with a higher flow rate or reducing the size of the lift cylinders in which case your maximum lift ability will be reduced.

The slow lift rate that some of you are complaining about is NOT a problem. It is a design feature. This is the way the system was designed by the engineering department. Another way of looking at this is to say " I would like a tractor that lifted less weight" The amount of weight that your FEL will lift to full height is designed in to the machine by engineering. If you want a FEL that will lift less, you are going to need to change out your lift cylinders to ones with less cross sectional area of the piston, or reduce the setting of the relief valve. If you keep the original pump flow rate with these new smaller cylinders you will find that not only does the FEL lift less weight, but ALSO now those smaller cylinders fill with fluid faster making the lift speed increase. So there now, we have achieved your goal of a faster lift speed.

What started me off on these explanations was a poster saying that "somehow", he didn't know how, you could adjust the relief valve to increase lift speed. And I refuted that premise. As the only way I know of to increase lift speed is to increase the flow rate of the pump, or decrease the size of the lift cylinders so they fully extend quicker as the volume of fluid need to fill them will be less than the larger ones you now have installed. It is as simple as that.

I'm pretty sure I've heard this story before:

Pressure, flow, speed - pick any two. Or something like that.

 

[k0ua]

I'm pretty sure I've heard this story before:

Pressure, flow, speed - pick any two. Or something like that.

Yep. And I wrote a "book", and you summed it up nicely in a sentence.

 

[mred2]

But James, you did it right. I mean I almost even understood it.
No, I have been around tractors most of my life and I am just understanding the difference between open and closed systems. The most that I have had to do was change a hose or pack a cylinder.

 

[k0ua]

But James, you did it right. I mean I almost even understood it.
No, I have been around tractors most of my life and I am just understanding the difference between open and closed systems. The most that I have had to do was change a hose or pack a cylinder.

What I find is really interesting about the flow rate, speed resistance thing in hydraulics is almost the very similar thing in electronics. The understanding of Voltage, Current, and Resistance as defined by Ohm's law.

 

[k0ua]

As an interesting note, When I purchased my current tractor a DK35se Kioti, I also tested the DK40se. Of course it was more money, the chassis was 4 inches longer and the rear tires were a size larger and one of the things my wife didn't like about it was the step to mount the tractor was a few inches higher and she had difficulty getting on the tractor. This was one of the factors that pushed me to the slightly smaller tractor. The flow rate of the pumps were only slightly different with the DK40se having about 1 more gallon per minute at around 11 and the DK35se at about 9.9 I believe.

Now the Loaders normally fitted to the two tractors have different specifications. The KL401 normally fitted to the DK40se has a maximum lift capacity of 2760 pounds at full height at the pins. the KL351 normally fitted to the DK35se has a maximum lift of about 1400 pounds to full height at the pins. That is one heck of a difference. While the KL401 can be fitted to the DK35se according to the book, I have never seen one so fitted. BUT when test driving them both, I noted a huge difference in the lift time between the two tractors. The KL401 equipped DK40se is MUCH slower to lift and curl etc than the smaller KL351 fitted to the DK35se, As the pump on the DK40se has only marginally greater flow rate, the massive cylinders on the KL401 take a lot longer to fill with fluid and are therefore much stronger and take a lot longer to lift.

It was very noticeable when I tested, and I also noted how much faster the Kioti DK35se was than my last tractor of about the same size the Kubota L3400hst. The pump on the Kubota was about 6 gpm as I remember and compared to the the nearly 10 gpm pump on the Kioti, it lifted slower, even though it cylinders are slightly smaller than the Kioti.

I quickly became accustomed to the KL351 loader on my new Kioti even though I thought it extremely fast at first as I was used to the Kubota. My new Kioti would outwork my old Kubota easily in loader operations because the loader was much faster, and also had a bigger bucket and would lift more even though the frame size and engine size were near the same. Kubota built the L3400 to meet a price point, the Kioti was built to meet a performance point. Kubota also builds other models that will match or even exceed the performance point of my Kioti, but they are a lot more expensive than an L3400.

It is all about engineering and the goals the engineering team are trying to accomplish, but always being restrained by marketing forces.

 

[PCABE5]

Good discussion going on about flow and pressure but I didn't want two posts to get lost in the mix when they mentioned increasing the engine RPMs.

Gear pump flow rates follow a linear curve with RPMs so both posters were correct and I thought it was worth mentioning it.

 

[k0ua]

Good discussion going on about flow and pressure but I didn't want two posts to get lost in the mix when they mentioned increasing the engine RPMs.

Gear pump flow rates follow a linear curve with RPMs so both posters were correct and I thought it was worth mentioning it.

Good point, I don't suppose you have those curves for any of the models in question? I don't. But in general the higher the RPM the higher the flow rate, to a point. But the pressure's reached in the system will be the same until the relief kicks in then increasing the rpm will actually give you slightly more because the flow rate can be more than can flow over the relief valve. but Very little more. And that is really reaching for straws.

Just like the water valve on the side of your house and your garden hose. Crack the valve so that it barely drips. Attach the hose, and put thumb over the hose. Depending on how much water was in the hose to begin with, it will take SOME time to fill the hose. With your thumb over the hose the pressure will slowly increase until you may not be able to hold it depending on the city or your own pressure system is set for. Usually 60 to 100 lbs per square inch. Unless your thumb is very strong, the water will escape past your "thumb valve" and water will spill on the ground.
How can this be you say? The flow rate is extremely low, due to the valve just barely being cracked to a drip. BUT the drips will keep on coming against that obstruction of your thumb until the system maximum pressure is realized or your thumb lets water escape. As a corollary, there is near zero pressure in the hose until you put your thumb over the end. your thumb is the obstruction that caused the pressure to rise albeit very very slowly.

If you open the valve fully, the result will be the same except the flow rate will have drastically increased, but the ultimate pressure rise in the hose will be the same, but now your thumb will start to release water in milliseconds instead of minutes/hours. Still the pressure will be very low in the hose when you take your thumb off, only the friction of the water with the inside of the hose will develop some pressure. Put a restriction nozzle on the end of the hose, and the pressure will rise more and the water can be delivered in a stream to water your flowers.

Once you understand these ideas of flow and restriction and pressure rise, the hydraulic system is a piece of cake. Unless we start talking about regeneration. Some loader valves have a regeneration feature, Many compact tractors loader valves in fact do. Some manufacturers call it "fast dump" or some other name like that. on that second loader valve circuit. NOT the lift circuit, but the Curl/Dump circuit. We can talk about that if someone wants to. Otherwise, I am not going to spend the typing time unless there is interest.

 

[PCABE5]

Good point, I don't suppose you have those curves for any of the models in question? I don't. But in general the higher the RPM the higher the flow rate, to a point.

Yes I posted the flow rates for the XR31xx and XR41xx in this post.

https://www.tractorbynet.com/forums/showthread.php?t=425767

 

[k0ua]

Yes I posted the flow rates for the XR31xx and XR41xx in this post.

https://www.tractorbynet.com/forums...hydraulic-pump-upgrade-deplorable-diesel.html

Very good thread there, real world figures.

Well, guys there you go, a real way to make your loader faster. Replace the stock pump with a higher flow rate pump as shown in the thread.

 

[PCABE5]

Very good thread there, real world figures.

Well, guys there you go, a real way to make your loader faster. Replace the stock pump with a higher flow rate pump as shown in the thread.

You mentioned it above but thought it was worth repeating. The "system" has to be able to support the larger pump. The lines and valves in the system have to be able to support the new flow rate or it will not perform as expected. The XR's had lines and valves that could support a 12gpm flow.

One piece I have found marginal in my new setup is the loader QD's. 1/2 inch QD's would be ideal but would require some custom plumbing to make that work.

 

[k0ua]

Did you notice any temprature rise in any of the components with the increased flow rate? How about the engine, did you notice any more load on engine HP? Or would it be so little as to be unnoticeable?

 

[PCABE5]

Temperature at the suction filter with an infrared meter was 160-165°F at about 89°F ambient temperature with the old and new pump. So I'm not seeing a temperature spike and I'm okay with that fluid temp. That is after 4 hours of finish mowing.

I did notice some temperature increase doing a flow test at the loader valve as I could feel it in the hose and I did not notice it at the rear outlets. That was why I think the loader QD's are marginal. 3/8 industrial (loader) verses 1/2 AG connectors (rear) make a difference.

Engine runs at 180°F when it's 80+ outside and that is where the thermostat starts to open so I'm good with that. Keep in mind that the air conditioner is running as well.

I'm sure there is a hit on horsepower but not noticable in my use. At full pressure it will take more HP but that is not a constant state. I'm just guessing here, but at a no load condition the additional power needed to run this pump vs the stock pump is probably is less than 1 HP. In my limited field testing I notice about the same load in certain sections of my property with either pump. I'm also not noticing any appreciable increase in fuel usage.

 

[k0ua]

So you are saying the only real downside noticed is the extra onetime hit to the wallet and a single hit to the time budget to install it. The rest is all upsides. More loader work can be accomplished per unit time, less frustration waiting on the loader overall.

 

[PCABE5]

You pretty much nailed it on the head.

I should add I have 50 hours on the setup with no issues. Pretty darn happy with everything.

 

[AnotherBueller]

Outstanding explanation of how a hydraulic system works.
Bob
ex Air Force aircraft mechanic