Step effects of adding shims on hydraulic pressure

This was my highly scientific method of reaching my desired 1,450 psi:







Andreas

Andreas,

Is the washer the rubber looking piece in the cap? Flat on one side and rounded on the other? An O ring actually!

I wish I had talked a pic!

Bruce

Hostaman said:

Andreas,

Is the washer the rubber looking piece in the cap? Flat on one side and rounded on the other? An O ring actually!

I wish I had talked a pic!

Bruce

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pictures can be found here:
https://www.mytractorforum.com/16-s...3-legacy-k92-hydraulic-psi-increase-done.html

Hostaman said:

Thanks Mattman,

That is the thread that I reviewed before my first pass at adding the shims. I don’t have the washer, just shims:dunno:

I have now reduced the X729 from 1,450 psi to 1,275 and my X700 is now at 1,350.

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As a side topic.... I assume you're increasing the pressure for a 45 loader... What's your experience with the loader? I heard people were popping the rear steering links when the loader was loaded on 4WS tractors.

That’s true, I bent the rear wheels steering linkage once when I was in a jam. I also hear a lot of popping in the linkages with what may be too much ballast with the liquid filled HDAP’s and a lot of weight out back so I’m changing the lineup to matching the X700 to loader work and the X729 to mowing.

Hostaman said:

Probably, that's why I specified it.

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cadman56 said:

Question. In the first post you stated "cold engine". Isn't the engine supposed to be at operating temperature to get accurate pressures while shimming?

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Probably a dumb question, but does the pressure increase as the fluid warms up? I’m pretty sure I shimmed mine when cold. From the factory, I was at 95si, added one 1mm washer and went to 1250. Added another one, and went to 1550. I took that washer back out and am happy at 1250psi.

papashelby said:

Probably a dumb question, but does the pressure increase as the fluid warms up? I’m pretty sure I shimmed mine when cold. From the factory, I was at 95si, added one 1mm washer and went to 1250. Added another one, and went to 1550. I took that washer back out and am happy at 1250psi.

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I'm not sure, but every write up I've read said to have the engine at operating temperature. Maybe someone more knowledgeable about hydraulics will chime in here on whether the engine should be hot or cold when doing the test.

cadman56 said:

I'm not sure, but every write up I've read said to have the engine at operating temperature. Maybe someone more knowledgeable about hydraulics will chime in here on whether the engine should be hot or cold when doing the test.

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At lower temperatures, the hydraulic oil has a higher viscosity (thicker), which means that you can see higher pressures at lower temps. (The pump will have to work harder and build up more pressure to move the oil). Having said that, the relief valve should negate that effect in most cases, as long as the higher viscosity oil can easily pass through the small hole in the relief valve. Its always recommended for the oil to heat up a bit so that the relief valve can easily do its job, and you will get more accurate readings.

Hi - the JD High-guard hydraulic oil is thin even when cold, temp does not matter much. I think you are needlessly worrying about the valves set point. I stacked washers in mine like a roll or quarters - at - I have run my 45 FEL shimmed for 12 yrs w/o an issue or a leak. At idol, I have 1500 PSI at the hose connect. At 1/2 throttle, I have 3,200 PSI, at full throttle, I have 3,600 PSI :tango_face_devil:
I have measured the lift capacity of the loader - it was still going to full height w/o a problem with 1500 lbs in the bucket. I ran out of payload! I heat w/wood, and move 24" diameter x 6 to 8 ft long green oak logs all the time. Shim-it and forget it!!

whx595 said:

Hi - the JD High-guard hydraulic oil is thin even when cold, temp does not matter much. I think you are needlessly worrying about the valves set point. I stacked washers in mine like a roll or quarters - at - I have run my 45 FEL shimmed for 12 yrs w/o an issue or a leak. At idol, I have 1500 PSI at the hose connect. At 1/2 throttle, I have 3,200 PSI, at full throttle, I have 3,600 PSI :tango_face_devil:
I have measured the lift capacity of the loader - it was still going to full height w/o a problem with 1500 lbs in the bucket. I ran out of payload! I heat w/wood, and move 24" diameter x 6 to 8 ft long green oak logs all the time. Shim-it and forget it!!

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Hi,
I have a few questions:
1- How much ballast weight do you have?
2- What front tires are you using? I don't see them squatting with that load
3- looks like dual tires in the rear?
4- I guess your configuration helps with the tractor stability with that load?
5- Do you run at full throttle all the time (or only when lifting heavy loads)?
6- Are you not worried about the front axle?
7- Also, I find the JD Hy-gard Oil pretty thick at low temps.. I used the loader today at -12C and when cold, the loader would lift at half speed until the oil warmed up. I wonder why you don't see that effect.
Its nice to see that the K92 is well designed to handle that pressure.
thanks, matt

whx595 said:

Hi - the JD High-guard hydraulic oil is thin even when cold, temp does not matter much. I think you are needlessly worrying about the valves set point. I stacked washers in mine like a roll or quarters - at - I have run my 45 FEL shimmed for 12 yrs w/o an issue or a leak. At idol, I have 1500 PSI at the hose connect. At 1/2 throttle, I have 3,200 PSI, at full throttle, I have 3,600 PSI :tango_face_devil:
I have measured the lift capacity of the loader - it was still going to full height w/o a problem with 1500 lbs in the bucket. I ran out of payload! I heat w/wood, and move 24" diameter x 6 to 8 ft long green oak logs all the time. Shim-it and forget it!!

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The pump in the K92 is rated for 1502 psi. I'd be more concerned about pump breakage than leaks in lines rated for 1900-4100 psi or fittings rated for 3500 psi.

Any open center hydraulic system with a functioning relief valve that I have seen will reach the same pressure at idle as WOT. Of course, fluid has mass, and that mass in motion will cause a spike in pressure before the relief valve can react to redirect the flow. A higher throttle setting will result in a higher pressure spike due to the higher rate of fluid flow. It's the steady state of pressure after the spike that indicates the actual relief setting.

The heaviest known weight that my GT loader has lifted and transported was a 1250 lb crate containing a metal lathe strapped over the back of the 210 lb bucket. The 4-ply front tires were wide ovals with the resulting 3000 lb load being supported. The tires were load rated for 960 lb each at 35 psi. Total ballast was 650 lb plus operator.

The heaviest load lifted also lifted the rear wheels off the ground. Ballast for that lift was 865 lb plus operator. Estimated payload weight . . . about 2000 lb. I was pulling 10" diameter concrete piers, with the associated suction and friction, out of the ground. Actual weight of the piers is just shy of 400 lb each.

It has lifted one end of a 2185 lb pine log (scaled weight) 3' off the ground at just above idle.

The relief valve setting is about 1500 psi. A hydraulic system will lift a payload with limited indication of strain until it reaches the relief setting, then it will no longer lift.

There is no doubt in my mind that you have lifted the weights that you mentioned. I'm just surprised that the pump in the K92 hasn't failed catastrophically before now with the pressures mentioned. It's either well underrated by the manufacturer, or you are incredibly fortunate. In any event, excessively high pressure increases the rate of wear in pumps dramatically.