Load Sensing Hydraulics

[openspaceman]

I wouldn't be that concerned about the heating, the tractor will have an oil cooler and when its not grafting and open centre valve isn't exactly generating volcano temperatures and not even anything like even under load.

 

Agreed but you should keep the resistances low and if you are using a remote valve to feed the winch do make sure you return it to the tractor via a low resistance, not through the return to a spool valve.

[monkeybusiness]

I wouldn't be that concerned about the heating, the tractor will have an oil cooler and when its not grafting and open centre valve isn't exactly generating volcano temperatures and not even anything like even under load.

 

Good to know. Yes it has got an oil cooler. How do you feed a pto pump from the tractor's back end? Does it pull from an existing spool or have its own pickup (I would assume the latter)?. What sort of money are pumps?

[treequip]

You are going to have to find a supply to the pump, it may take some imagination.

 

It needs to be as big as possible, if its too small the pump will cavitate, feeding or returning it through a spool will probably cause problems.

[treequip]

Price wise for the pump, get the motor data and ask white house or flowfit (other suppliers are available) to quote for a suitable pump, it will be in hundreds rather than thousands

[openspaceman]

You are going to have to find a supply to the pump, it may take some imagination.

 

It needs to be as big as possible, if its too small the pump will cavitate, feeding or returning it through a spool will probably cause problems.

 

As the feed is to a motor the return will be the same volume so it should be possible to TEE a supply from the return but below reservoir level and return must be below the fluid in tank or transmission. If the winch motor has an automatic (failsafe on no pressure) brake then the spool should be a motor spool with ports connected in neutral.

[monkeybusiness]

There are obviously a lot of knowledgeable people on here so maybe you can let me know if my next idea has any legs or not... The winch came with a spool valve, but not compatible with the load sensing hydraulics on the tractor. Is it possible to fit a straightforward load sensing valve (no spool control required) 'upstream' of the winch's original spool valve to control the tractor's pump? If so I could also plumb my timber trailer's crane into it - this currently runs fine through a bog standard constant flow spool on the back of the tractor but a bit more speed wouldn't hurt...

[openspaceman]

There are obviously a lot of knowledgeable people on here so maybe you can let me know if my next idea has any legs or not... The winch came with a spool valve, but not compatible with the load sensing hydraulics on the tractor. Is it possible to fit a straightforward load sensing valve (no spool control required) 'upstream' of the winch's original spool valve to control the tractor's pump? If so I could also plumb my timber trailer's crane into it - this currently runs fine through a bog standard constant flow spool on the back of the tractor but a bit more speed wouldn't hurt...

 

I don't understand the problem but then I've only come across load sensing on more modern kit and never needed to delve in to it. I thought load sensing just adjusted the pump output to match the pressure and speed the spool fed the cylinder. On a simple open centre system the control would be by gently bleeding oil through the spool with the remainder bypassing the cylinder (and heating up in the process) and going directly to tank, load sensing avoids the waste heat??

 

A simple swash plate pump used with an open centre valve is normally controlled by its internal system to deliver a constant power. As power is flow times pressure this meant in practice it delivered full flow at no load and then as pressure built up flow was reduced. I'm about 40 years behind the times when I was looking at these system as FC were developing their all hydraulic skidder.

 

Having said all that I borrowed a JD tractor and nearly boiled the oil with my logsplitter some years back, never did understand JD hydraulics.

[Breezeblock]

the only way i could see doing this would be to take a tapping off each side of the a + b side of the valve thru a double tee non return valve and feed this thru a pressure reg valve set 25 bar below the required pressure then thru another non return valve into the ls port on the tractor pump

[Breezeblock]

I don't understand the problem but then I've only come across load sensing on more modern kit and never needed to delve in to it. I thought load sensing just adjusted the pump output to match the pressure and speed the spool fed the cylinder. On a simple open centre system the control would be by gently bleeding oil through the spool with the remainder bypassing the cylinder (and heating up in the process) and going directly to tank, load sensing avoids the waste heat??

 

A simple swash plate pump used with an open centre valve is normally controlled by its internal system to deliver a constant power. As power is flow times pressure this meant in practice it delivered full flow at no load and then as pressure built up flow was reduced. I'm about 40 years behind the times when I was looking at these system as FC were developing their all hydraulic skidder.

 

Having said all that I borrowed a JD tractor and nearly boiled the oil with my logsplitter some years back, never did understand JD hydraulics.

 

ls systems let you fit a lower hp engine use less fuel and lose less energy to heat so you end up with a smaller cooling package

[monkeybusiness]

the only way i could see doing this would be to take a tapping off each side of the a + b side of the valve thru a double tee non return valve and feed this thru a pressure reg valve set 25 bar below the required pressure then thru another non return valve into the ls port on the tractor pump

 

Is that to 'confuse' the pump into not seeing the closed downstream spool as requiring maximum power? Would it work in the real world (would the pump perform as normal when called upon?). Would the pump be constantly engaged sending oil through the pressure regulator valve when not winching, negating some of the benefits of load sensing in the first place? Sorry for all the questions, I'm trying to get my head around how this might work but I don't want to reinvent the wheel.

It seems a shame not to make use of the pump already fitted to the tractor, particularly as a quick look at pto pumps on Flowfit's site appears to show nothing available from their standard line up that can match the performance of the power beyond setup. I would imagine an equivalent performing pto pump is going to be pretty heavy money itself. I know that there is going to be a chunk of money spent somewhere and that is fine, but I'd rather only spend it once and if I could kill 2 birds with one stone (ie use the flow to run the crane as well) then that would be superb.