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Discussion Starter #21
You're probably right Bob; according to that graph, the original lines of the tractor are just adequate for the original flow; at full rpm of course.
At the moment the hedge cutter is not mounted, so the pressures I'm reporting is just the original circuit + a diversion through a valve block for the FEL.
The FEL valve block has 3/8" ports and was made in Spain, probably before the American discoveries.
The back pressure [for lack of a better term] is significant even at idle, around 20 bar, and was the same with the old pump.
I always thought it's restriction through the 3-point lift system.

Pedro;
Yes, the other pump is the steering. The return from the steering feeds into the suction lines at the filter.

Next time I use the hedge cutter I'll see what happens with heat and pressure, then decide where to go with it; If the lines and / or FEL valve block needs upgrading.
I can check if the pressure drops when I feed it into a bucket instead of the 3-point lift.
I could add a bypass valve if that's the case.
 

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Mark, what is the size of the ports on the diverter valve? Upgrade to something with 3/4" or 1" supply and return ports.

How much flow is being diverted to the loader? If it's more than 4-5 gpm, the loader valve set also needs to be upgraded.

Smaller lines on bigger ports work fine. Bigger lines on smaller ports make for restrictions to flow and higher back pressure.
 

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Discussion Starter #23
I'm not sure what you mean by diverter valve, probably because I don't have one.
All the flow runs through the whole system.

The pump output runs through a 1/2" hose to a quick connector at the FEL valve block, the outflow from there runs to the original accessory valve [2 hydraulic ports at the rear] behind the seat, and from there into the case where it feeds the 3-point lift.

When I attach the hedge cutter, I disconnect the pump hose from the FEL and connect it to the 1/2" hedge cutter hose.
That runs up the FEL arm to the hedge cutter valve block and back to the FEL valve, where it feed into the pressure port again.

The back pressure is about the same with or without the hedge cutter connected [and when not at work of course].

Any upgrades will be expensive; not impossible but I'll only spend that sort of money after I'm 100% sure I need to.
I'll keep an eye on everything and if necessary run some tests to find where the restrictions are, so where my cash and work are best invested.

Remember that 95% of the time, I only run the engine at 1/2 speed or less.

On the other hand, I'm in the process of lowering the final ratio on the hedge cutter so oil flow will increase, and [hopefully] pressure decrease during use.

I wouldn't even be aware of this if I hadn't added a pressure gauge to the system.

I have some little electronic thermometers with sensor on a wire; I could attach them to the in and out of the FEL valve block.
If there is restriction, there would have to be a temperature rise?
 

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Do you have a way to run it without those quick disconnects? Like connecting the hoses to each other with a 1/2" adapter.

Those quick disconnects on the input/output side of the valves will also contribute to create heat and back pressure.
 

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Discussion Starter #25
I'd likely have to buy or make fittings. And there's always oil spilling around during that sort of operation.

So sure, I could do that, and a lot of other things when I decide to delve in.

I like the temperature measuring idea; it might not give a clear result but if it does then it's cheap and painless.

Otherwise I can start unscrewing things. Just start it up and run the oil into a bucket, or through a tube back into the case while watching the pressure gauge, and all will be revealed.

It will be messy.
 

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I'm not sure what you mean by diverter valve, probably because I don't have one.
All the flow runs through the whole system.

I wouldn't even be aware of this if I hadn't added a pressure gauge to the system.

I have some little electronic thermometers with sensor on a wire; I could attach them to the in and out of the FEL valve block.
If there is restriction, there would have to be a temperature rise?

Okay. Your comment in your previous post threw me off track.

so the pressures I'm reporting is just the original circuit + a diversion through a valve block for the FEL.
If all of the flow is going through the loader valve set, you need a new one with 3/4" - 1" supply and return ports. The 3/8" ports on the existing valve set are choking the fluid flow.

The electronic thermometers would make a good diagnostic tool used as you describe, but in this case they aren't warranted. The flow rate for 3/8" hose (and ports) is 6 gpm, and you're trying to push up to almost 3 times that much flow through the loader valve. That is a serious restriction!
 

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Discussion Starter #27
You're right of course, but there seems to be restriction even at idle, when flow is quite reasonable.
This is the only hydraulic machine I've ever had with a gauge on it and I have no idea what normal is.

I'm working on other things at the moment but I'll get back to it in a few weeks.
 

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On my tractor I guess 0 Bar even full throttle but the gauge accuracy on that low pressure won't be accurate. There is probably anything from 0 to 5 Bar.

Since the pump is just going through all the valves and then to tank, it won't create too much pressure.

If you are seeing those pressures even at idle, then something definitely creating restriction.

You mentioned some time ago that your loader is small for your tractor since it was made for much smaller tractors. I wonder if the loader valve is also undersized for your tractor.

I think I would bypass the loader valve, just to troubleshoot the restriction you have in hand. In my opinion the original hydraulic system should handle the extra flow just fine.

But I'm very suspicious that the Quick Disconnects are creating the issue. It depends on the brands of QD but generally a 1/2" QD is rated at 45 L/min with a max rating of 90 L/min. My understanding is that anything over 45 Liters will create restriction. If this is indeed the problem, you might need to upgrade the couplers.

Can you turn on the lathe two fittings? Like 1/2" female on both sides. Then just replace the QD with your fittings to take that out of the equation.

EDIT: Or just search what brand and model of QDs you have and find the specs for it.
 

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On my tractor I guess 0 Bar even full throttle but the gauge accuracy on that low pressure won't be accurate. There is probably anything from 0 to 5 Bar.

Since the pump is just going through all the valves and then to tank, it won't create too much pressure.

If you are seeing those pressures even at idle, then something definitely creating restriction.

You mentioned some time ago that your loader is small for your tractor since it was made for much smaller tractors. I wonder if the loader valve is also undersized for your tractor.

I think I would bypass the loader valve, just to troubleshoot the restriction you have in hand. In my opinion the original hydraulic system should handle the extra flow just fine.

But I'm very suspicious that the Quick Disconnects are creating the issue. It depends on the brands of QD but generally a 1/2" QD is rated at 45 L/min with a max rating of 90 L/min. My understanding is that anything over 45 Liters will create restriction. If this is indeed the problem, you might need to upgrade the couplers.
Size of the tractor is irrelevant. Size of the pump is definitely relevant.

Proper design of a system would include that all components be capable of handling the maximum flow produced by the pump. Since the pump has been upgraded, everything in the system is suspect for adding restriction at max flow, some more obviously than others. At engine idle, not so much. All should be capable of handling the resulting flow without any more than the normal restriction caused by the fluid moving through the lines, usually something around 2-5 bar (30-70 psi).
 

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We don't get OEM loaders on tractors in Europe. Every loader you see on them, it's aftermarket.

The loader is an aftermarket loader made for a much smaller tractor, therefore whoever installed it, most likely used the same valve which may or may not meant for a smaller tractor. So the tractor size is still relevant with that loader on.
 

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Discussion Starter #31
The flowfit catalog shows 3/8" port directional control valves rated at 45 liters per minute; sufficient for maximum flow with the original hydraulic pump, and sufficient even for the new pump most of the time.

Of course Bob is right, things should be upgraded to handle the new maximum flow; but it is not under rated for the flow at 1,200 rpm where I have a back pressure of 25 [ish] bar.

I'm working on a new crankshaft + other upgrades for the hedgecutter, and also rain is forecast all week [this makes me really happy!]
So the tractor will stay in the shed for a while.

I bought one of those infrared thermometers a few years ago, it stopped working but maybe I can fix it.
That might speed up diagnostics a lot.
 

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We don't get OEM loaders on tractors in Europe. Every loader you see on them, it's aftermarket.

The loader is an aftermarket loader made for a much smaller tractor, therefore whoever installed it, most likely used the same valve which may or may not meant for a smaller tractor. So the tractor size is still relevant with that loader on.
You are assuming that the pump in a larger tractor is also larger with a higher flow rate.

Along with a higher than normal flow rate comes a higher than normal cylinder speed which can result in the operator over controlling the loader, with the result that the front end of the tractor can be bounced off the ground before control is re-established.

The valve may be too small for the higher flow rate, thus providing a restriction that generates heat and back pressure, but it will still pass enough flow to create the over controlling situation for the operator.

I have 3 different loaders, only one of which is original to the tractor. Two of them are physically similar in size except for the cylinders. The GT has a 6 gpm pump and the SCUT has a 4.6 gpm pump because it has much smaller cylinders. Both have a 2/3 throttle position as the sweet spot for speed and control. If the loaders were switched, the SCUT would have to be run at WOT to achieve acceptable cylinder speed, and the GT would be uncontrollable at anything over half throttle. Both tractors would cause serious control issues with the third, much smaller, loader.

I reiterate, tractor size is irrelevant, pump size is relevant.
 

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I'm not assuming nothing. I'm stating that that loader is too small for that tractor, therefore the valve is also smaller for a tractor that big even with the stock pump.

I believe you're missing the point that the loader is not meant for that tractor, so using the argument that a properly designed system won't quite apply in this situation.

That loader is usually mounted on a 50 to 65 HP tractor with anything from 8 to 10 GPM, so yes, tractor size also matters as the loader is designed for a 50 HP tractor, not a 85HP. And of course the pump will also be bigger on the 85 HP one.
 

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The point is that cylinder size determines the size of the pump and loader valve. The size of the loader or tractor doesn't matter.

If a small loader is installed on a larger tractor with a larger pump, then it won't work as advertised. The cylinder speed will be greater and, if the pump is significantly larger, the valve set may be too small.

Hydraulic systems are designed for specific purposes. ALL of the components for the system should work in harmony. If the cylinder sizes change, then the pump has to change in order to maintain that harmony. If the pump size changes to create additional flow, it may change enough to go beyond the flow rate of the valve set and will result in additional cylinder speed.

Yes, larger tractors generally have larger pumps, but it is the pump that is important to the hydraulic system, not the size of the tractor. Smaller tractors can also have larger pumps if they were designed for specific high flow rate implements, such as a hydraulic post hole digger.
 
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