Still a little confused about power beyond

CTPhil

Member
I've read a lot of the threads about power beyond, but still don't quite get it. What I want to do is put a PB adapter on my 3550 to run one remote valve to supply a third function to a grapple. Can it be installed with just supply and return hoses, or is it more complicated than that?

Thanks!
 
you need a PB compatible valve. the reason for this is you will be using downstream hyds ( like your 3pt. ), and non PB capable
valves, some of them may not tolerate that type of pressure.
 
(quoted from post at 11:03:00 11/09/17) you need a PB compatible valve. the reason for this is you will be using downstream hyds ( like your 3pt. ), and non PB capable
valves, some of them may not tolerate that type of pressure.
Can you elaborate on why there is more pressure? What makes a valve PB capable? Are we still talking about 2 lines only? Are there any secret words when sourcing a valve that is PB capable, or just "PB capable"?

Thanks!
 
look at it like this. hyds makes a series circuit. that PB plate under the seat interrupts oil from the hyd pump, after the
relief valve, but before it gets to the 3pt.

.. oil leaving that pb plate going thru your pb valve to run that third function, then travels back into the plate and to the
3pt. Now you lift the 3pt and there is a pressure load on the output port of that in line valve.

many non PB valves won't tolerate but a few hundred psi on their output port as they normally would see just a no pressure hose
return line to the tank.. not a 4 wire hyd pressure line to the 3pt delivering 2250 psi to the 3pt hyds.

PS.. since you didn't reply to me, but instead yourself, I almost missed this completely
 
So then anything "above" the PB plate is subject to pressure that wouldn't normally be there? Including the 3PH? The potentially damaging effects are to any valves of functions after the PB plate? If that is so is it OK to use a normal valve, like a log splitter valve, as the first valve on the supply side of the PB? Is there something different about how a regular under seat selector valve, that would be stacked on the PB plate, deals with it, or does the PB plate change how you'd use that valve?

Sorry to pile on, but I'm getting there, really. :)
 
Pick a valve then go to the manufactures web site and see if they offer a PB adaptor for that particular valve. Most valves will not be PB enabled without adding an adaptor after the fact.

You will have 3 hoses for the valve input/output. Input hose (pressure) from (adaptor/pump/PB out of existing valve), return hose to adaptor/pump (PB) and return hose to sump (can be T'ed into your existing return hose).
 
(quoted from post at 14:43:21 11/09/17) So then anything "above" the PB plate is subject to pressure that wouldn't normally be there? Including the 3PH? The potentially damaging effects are to any valves of functions after the PB plate? If that is so is it OK to use a normal valve, like a log splitter valve, as the first valve on the supply side of the PB? Is there something different about how a regular under seat selector valve, that would be stacked on the PB plate, deals with it, or does the PB plate change how you'd use that valve?

Sorry to pile on, but I'm getting there, really. :)
'm going out on a limb & say that you are confused here, because the use of PB valves/their location in the flow path (such as under seat on top of lift cover, or no PB valve there, but PB valve remotely plumbed in elsewhere), use of PB adapter plate or not and then you throw in 'selector valve". Probably every reader "sees" a different configuration than what you have or envision. Folks really need to know physically what you have in mind.
 
(quoted from post at 11:03:00 11/09/17) you need a PB compatible valve. the reason for this is you will be using downstream hyds ( like your 3pt. ), and non PB capable
valves, some of them may not tolerate that type of pressure.

That is not true if you are only running a single valve off of a power beyond plate that installs under the stock blocking plate. Those PB plates have 3 ports, power, return and PB. The instructions that come with it say that if you are only powering one valve, then connect the return line from that valve to the PB port and plug the return port.

I have it that way on the PB plate on my '73 4000 to power a front end loader that has a standard open center control valve without power beyond and it works just fine.

If using it with two valves the first one must be PB capable and the open center of the first one goes to the Return port on the block and PB port of the first valve goes on to power the second valve and the return from the downstream valve goes to the PB port.

Once it gets back to the block in either of the configurations I described, it goes on to the 3 point hydraulics the same way that any Ford remote vale would, so the 3 point is not considered downstream in terms of the PB setup.
 
You aren't out on a limb, I am confused. :)

I want to put a PB plate under the seat. On top I want to put a selector valve (Ford made, just one port out with a push/pull knob), to power a backhoe. The backhoe was on a parts 4100 and used that valve with the return going directly to sump. I want the PB to run a single valve like a splitter valve to add a third function to a loader grapple. The loader has it's own engine driven pump.
 
Sean in PA, so once the PB plate is on, anything else gets it's power from the fluid coming back through the return to the plate?
 
Using an added valve that is not power beyond capable only puts that valve at risk when a demand downstream from that valve (3PT, your
backhoe recieving flow from the selector valve) allows system pressure to build on the discharge side of your added valve. Most valves are not
designed to be pressured on the return side. This is why a power beyond capable valve with dedicated PB and Return/Tank connections (3 total
hose connections to the tapping manifold) is a better choice.
 
(quoted from post at 20:22:51 11/09/17) Using an added valve that is not power beyond capable only puts that valve at risk when a demand downstream from that valve (3PT, your
backhoe recieving flow from the selector valve) allows system pressure to build on the discharge side of your added valve. Most valves are not
designed to be pressured on the return side. This is why a power beyond capable valve with dedicated PB and Return/Tank connections (3 total
hose connections to the tapping manifold) is a better choice.
do see your & SouNdguy's point of the high pressure on return side of non-PB rated valve...........that raises the next question & that is what if any is the application for the 2 port adapter plate?
 
For use of simple valves that lack PB capability. You can use a $50 valve if you don't grenade it with the 3 point load.
 

You need an "open center" external valve that when NOT in use, it returns the high pressure back to be used down stream for the 3 pt lift.

The external valves can be had in "open center" models and "closed center" models. A commonly used cross valve can be changed from closed center to open center by changing a special "double plug" on it, to a common "plug".

Also in addition to the open and closed center, the external valve can be a single one way, a single two way, a double combo of one way and two way, a triple....etc etc etc...

for a loader, most used is a double two way, open center valve.

Also you can get the external valve with features like.....detents, auto return to center at end of stroke, float, and other options.. Most external valves also have a overload safety valve built it.. This valve must be set at the same setting as the tractor's safety valve in most cases or it will lower the power of the 3 pt lift as well as lower the power of the loader. The lowest setting safety valve will always open first and drain off excessive pressure, there by controlling th e maximum you can pick up, either on the loader or the 3 pt. So if the tractor safety valve is set at 2300 lbs. the loader valve should be a bit more.. in most cases.

are you confused yet???
 
(quoted from post at 21:07:04 11/09/17) For use of simple valves that lack PB capability. You can use a $50 valve if you don't grenade it with the 3 point load.
f I have the 2 port connections correct, I don't see a path for the external cylinder to dump other than going thru the check valve (seems too high a pressure), or the backpressure valve if 3 point is in either hold or lower. What path do you see?
 
This may help...
5876.jpg
 
(quoted from post at 18:50:36 11/09/17) So I should be sure to get one with 3 ports.

Never seen an adapter plate with 3 ports and doubt you will be able to find one. Sump return is typically plumbed into the fill cap using some method of getting a pipe fitting installed in the cap.

I kinda went overboard with the Sump return on the 3600 I am in the middle of adding top and tilt to. Started with a 1 1/4 inch female to 1/2 inch male pipe adapter. 1 1/4 pipe threads are the same as the cap but because the adapter is threaded for pipe the threads are too long and tapered. I cut the threads down to be the same length as the threads on the cap then re-cut the left over threads to fit the smaller thread size of the cap. I then cut one end of a T fitting off as far as I dared and welded it to the top of pipe adapter. This gives me a return port for the hose and an opening for adding fluid without having to disconnect the hose.
 
(quoted from post at 04:49:33 11/10/17)
(quoted from post at 18:50:36 11/09/17) So I should be sure to get one with 3 ports.

Never seen an adapter plate with 3 ports and doubt you will be able to find one. Sump return is typically plumbed into the fill cap using some method of getting a pipe fitting installed in the cap.

I kinda went overboard with the Sump return on the 3600 I am in the middle of adding top and tilt to. Started with a 1 1/4 inch female to 1/2 inch male pipe adapter. 1 1/4 pipe threads are the same as the cap but because the adapter is threaded for pipe the threads are too long and tapered. I cut the threads down to be the same length as the threads on the cap then re-cut the left over threads to fit the smaller thread size of the cap. I then cut one end of a T fitting off as far as I dared and welded it to the top of pipe adapter. This gives me a return port for the hose and an opening for adding fluid without having to disconnect the hose.
hat separate return to sump makes good sense Bob. I do believe the HV5902 (3 port adapter plate) is likely the same as the HV4902 2 port plate with the absence of the third. return to sump connection, in the plate.
 
(quoted from post at 20:22:51 11/09/17) Using an added valve that is not power beyond capable only puts that valve at risk when a demand downstream from that valve (3PT, your
backhoe recieving flow from the selector valve) allows system pressure to build on the discharge side of your added valve. Most valves are not
designed to be pressured on the return side. This is why a power beyond capable valve with dedicated PB and Return/Tank connections (3 total
hose connections to the tapping manifold) is a better choice.

RickB - I may be misinformed, but I thought that when a diverter or remote valve is installed on top of the PB plate that the valve on top gets flow first.
 
Ignore my last post... I looked at the flow diagram that BobReeves provided after I posted that, so I learned something.
 
Learned something also, wasn't aware of a path to the sump under the plate and the availability of a 3 port adapter. Now wished I had known this when I bought the one I have. Too late now, already have everything plumbed and not going to change it :)

5877.jpg
 
(quoted from post at 04:49:33 11/10/17)
(quoted from post at 18:50:36 11/09/17) So I should be sure to get one with 3 ports.

Never seen an adapter plate with 3 ports and doubt you will be able to find one. Sump return is typically plumbed into the fill cap using some method of getting a pipe fitting installed in the cap.

I kinda went overboard with the Sump return on the 3600 I am in the middle of adding top and tilt to. Started with a 1 1/4 inch female to 1/2 inch male pipe adapter. 1 1/4 pipe threads are the same as the cap but because the adapter is threaded for pipe the threads are too long and tapered. I cut the threads down to be the same length as the threads on the cap then re-cut the left over threads to fit the smaller thread size of the cap. I then cut one end of a T fitting off as far as I dared and welded it to the top of pipe adapter. This gives me a return port for the hose and an opening for adding fluid without having to disconnect the hose.

The HV5902 is such a plate and it is readily available. More so than the two port version. It can be used with a plain open center valve or one equipped with power beyond. If using an open center valve the return port on the plate is not used. If using a power beyond valve all three ports [u:9b20b0ec06]must[/u:9b20b0ec06] be used.

When using the HV5902 plate the tractor's 3pt is a down stream valve and all upstream (external) valves should be power beyond if you want to do it right. That said I suspect there are hundreds of open center valves being used as upstream valves with few if any explosions ;-)

TOH
 
Referring to the posting of the schematic, but all of the other posts as well. And I'm feeling a bit better that others find this a hard subject to nail down also, lol. :)
 
(quoted from post at 08:04:32 11/10/17) Learned something also, wasn't aware of a path to the sump under the plate and the availability of a 3 port adapter. Now wished I had known this when I bought the one I have. Too late now, already have everything plumbed and not going to change it :)]
That's easy to understand, I've looked at countless PB plates online, and they never seem to tell you in the description whether there are 2 or 3 ports. :(
 
Always thought the valves had to be open center.

This is more or less how my 3000 is configured with two dual spool Cross valves. One is the loader and the other is for the rear remotes. Difference is my sump return goes into the fill plug.

5878.jpg
 
I think a little light bulb just lit over my head. Does the name Power Beyond come from the fact that the fluid remains under pressure beyond the powered directional control valve?
 
Speaking of control valves, if you are looking and have a choice I would recommend putting Cross at the top of your list. I have Cross valves on my 3000 and a Bailey being installed on my 3600.

The ports on the Bailey are too close together to be able to use two 90 deg fittings in adjacent ports. Not so with the Cross, two 90 deg fittings will clear each other. Also the handles on the Baily are too close together, I bent one over so I could grab one handle without skinning my knuckles on the other one.

Bought the Bailey off eBay because it was less expensive than any dual spool Cross listed, now wished I had spent the extra on a Cross. Ended up spending the difference in fittings to vertically offset the 90 deg fittings needed to make hose routing reasonable.
 
(quoted from post at 22:16:03 11/09/17)
You need an "open center" external valve that when NOT in use, it returns the high pressure back to be used down stream for the 3 pt lift.

The external valves can be had in "open center" models and "closed center" models. A commonly used cross valve can be changed from closed center to open center by changing a special "double plug" on it, to a common "plug".

Also in addition to the open and closed center, the external valve can be a single one way, a single two way, a double combo of one way and two way, a triple....etc etc etc...

for a loader, most used is a double two way, open center valve.

Also you can get the external valve with features like.....detents, auto return to center at end of stroke, float, and other options.. Most external valves also have a overload safety valve built it.. This valve must be set at the same setting as the tractor's safety valve in most cases or it will lower the power of the 3 pt lift as well as lower the power of the loader. The lowest setting safety valve will always open first and drain off excessive pressure, there by controlling th e maximum you can pick up, either on the loader or the 3 pt. So if the tractor safety valve is set at 2300 lbs. the loader valve should be a bit more.. in most cases.

are you confused yet???

I am not confused. When using an upstream open center power beyond valve with the relief pressure set higher than the tractor 3pt relief valve:
  • [*:2e0b1c497d]The tractor relief setting will govern the maximum pressure at the 3pt[*:2e0b1c497d]When any spool on the PB valve is shifted out of neutral the PB port is blocked and the valve is isolated from the downstream 3pt relief valve. At that point the relief pressure setting in the PB valve will limit the pressure in it's work circuits[/list:eek::2e0b1c497d]This is one of the motivations for PB operation. In general you should always put lower pressure valves downstream of higher pressure PB valves. For example you can have the relief on your upstream PB loader valve set to 3000 PSI and that is what the loader cylinders will see regardless of the fact the 3pt relief setting is 2000 PSI.

    TOH.
 
(quoted from post at 09:21:05 11/10/17) I think a little light bulb just lit over my head. Does the name Power Beyond come from the fact that the fluid remains under pressure beyond the powered directional control valve?

Sort of. It comes from the fact that you are going to use pass thru oil to pressurize/operate something downstream of the valve. PB valves are nothing more than open center valves with a slightly modified operation. A power beyond valve functions as follows:
  • [*:713379ea3b]When all spools are in neutral incoming pressurized oil is routed straight through to PB port (e.g. open center)[*:713379ea3b]When any spool is shifted out of neutral the PB port is blocked and incoming pressurized oil is routed to a work port and pressurized return oil if any from the work port is routed to the tank port. This prevent interaction with downstream valves/cylinders and is the motivation for PB design.[*:713379ea3b]When over pressure occurs inside a PB valve the relief oil is routed to the tank port rather than PB port as would be the case in plain open center operation. Using a PB with the T port plugged is a recipe for quick pump and/or valve failure because shifting any spool out of neutral is an instant hydraulic deadhead.[/list:eek::713379ea3b]TOH
 
(reply to post at 08:45:15 11/10/17)




the two port system.. you dont really need a separate return.. Using the open center to return to the under seat plate will work fine..

good points.. you can raise both loader and 3 pt at same time with the two port system, all though it might be a bit slower due to combined weight...

vary rarely do you need the third return line.

if.....you dont use the hvxxxx plate and just tap the factory top plate with one pressure line,,,, then you need the return the fluid somehow, and the line to the fill plug is then used...



And.. as others have pointed out.. there is a second type of hvxxxx plate that give a pressure only port as well as the in and out port so you can do both types of taps.. with the pressure only port.. you must use a closed center type valve to preserve the pressure for you 3 pt...if your not using the loader.

Again, the lower of the two safety valve settings will be the one to break open first, so you should have it set at the same as the hydraulic pump setting or slightly higher,, to preserve the rated pressure....
 
(quoted from post at 10:02:28 11/10/17)
(reply to post at 08:45:15 11/10/17)




the two port system.. you dont really need a separate return.. Using the open center to return to the under seat plate will work fine..

good points.. you can raise both loader and 3 pt at same time with the two port system, all though it might be a bit slower due to combined weight...

vary rarely do you need the third return line.

if.....you dont use the hvxxxx plate and just tap the factory top plate with one pressure line,,,, then you need the return the fluid somehow, and the line to the fill plug is then used...



And.. as others have pointed out.. there is a second type of hvxxxx plate that give a pressure only port as well as the in and out port so you can do both types of taps.. with the pressure only port.. you must use a closed center type valve to preserve the pressure for you 3 pt...if your not using the loader.

Again, the lower of the two safety valve settings will be the one to break open first, so you should have it set at the same as the hydraulic pump setting or slightly higher,, to preserve the rated pressure....
You really need to look at some hydraulic schematics of a PB directional control valve. I have plumbed dozens of them and they don't work as you think. The HV5902 adapater and an open center w/PB control valve will allow you to use equipment like a loader in tandem with the 3pt. Your loader operating pressure can also be higher than the 3pt relief setting. I'll draw you a line diagram if you like. The following is from Baum Hydraulics glossary of hydraulic terms.

TOH

K16 TERMS FOR HYDRAULIC CONTROL VALVES

POWER BEYOND (Also referred to as high-pressure carryover), obtained by using a sleeved outlet that carries oil under pressure directly from the open center passageway of a control valve to the inlet of a down-stream control valve bank. This sleeve outlet prevents back pressure on the exhaust or return passage of a control valve which normally is not designed to take high pressure. This option also prevents back pressure on spool seals and also does not put back pressure on the built-in relief valve which, if allowed, tends to increase the relief valve opening point to the total of the relief valve’s original setting by the amount of back pressure in the control valve’s exhaust passage. This option is often used to obtain more valve sections or spools than normally obtainable by one control valve bank, or used when additional spools need to be added in the field. Still another use is to obtain a circuit in which it is desirable to have certain valve functions take “Priority” on flow. This is accomplished by having those functions requiring “Priority” flow be controlled by the upstream valve bank equipped with power beyond, then whenever a spool of the power beyond valve is fully activated, this will take all oil from pump and stop the flow of oil to any downstream valve until the power beyond valve spool is returned to neutral, at which time oil will again flow to the downstream valves. NOTE: It is always necessary to provide a tank return port on all power beyond valves in order that the “return” or “dump” oil from a cylinder or motor can be returned to the tank.

[color=red:9e9dcc1f9b]When several valves are fitted in a power beyond hook-up, it is also possible to provide different relief valve settings for each bank of valves in the circuit provided the highest pressure is in the valve bank closest to the pump and the next highest in the second bank, etc.[/color:9e9dcc1f9b] If all valve spool functions are to operate at same pressure, then only the first valve bank needs to be equipped with a relief valve and all downstream valve banks do not need a relief valve, however if they are equipped, the reliefs in all valve banks should have the same setting.
 
the two port system.. you dont really need a separate return.. Using the open center to return to the under seat plate will work fine..
vary rarely do you need the third return line.
ut if you did that you'd still need a directional control valve designed for the extra pressure, right?
 
(quoted from post at 10:50:55 11/10/17)
the two port system.. you dont really need a separate return.. Using the open center to return to the under seat plate will work fine..
vary rarely do you need the third return line.
ut if you did that you'd still need a directional control valve designed for the extra pressure, right?

Are you feeling lucky punk :roll:

Open center valves typically have a maximum outlet pressure rating of something around 500 PSI. SOP for hydraulic design is a safety factor of at least 3 so the theoretical working pressure of that section is probably close to 1500 PSI maybe even 2000 PSI. I have used open center valves on N-series hydraulic systems (1500 PSI relief) without any issues. I would be reluctant to use them on a system with higher pressures. The cost of a PB valve is negligible and if you want to do it right use a valve with PB. There are plenty of good reasons other than outlet pressure for doing it correctly. See the snippet I posted from Baum's glossary for specifics.

TOH
 
You really need to look at some hydraulic schematics of a PB directional control valve. I have plumbed dozens of them and they don't work as you think. The HV5902 adapater and an open center w/PB control valve will allow you to use equipment like a loader in tandem with the 3pt.

That depends on what you mean by "in tandem with". Yes, both will work without having to change the configuration, but not simultaneously, at least according to ypour description in your previous post about when the PB control valve is not centered, the PB port is blocked, so the 3 point will stop functioning for that period of time that the PB valve is off center.
 
(quoted from post at 10:08:53 11/11/17)
You really need to look at some hydraulic schematics of a PB directional control valve. I have plumbed dozens of them and they don't work as you think. The HV5902 adapater and an open center w/PB control valve will allow you to use equipment like a loader in tandem with the 3pt.

That depends on what you mean by "in tandem with". Yes, both will work without having to change the configuration, but not simultaneously, at least according to ypour description in your previous post about when the PB control valve is not centered, the PB port is blocked, so the 3 point will stop functioning for that period of time that the PB valve is off center.

That is true and I did not mean simultaneous. How do you propose to use them simultaneously? Think carefully before answering....

TOH
 
That is true and I did not mean simultaneous. How do you propose to use them simultaneously? Think carefully before answering....

Only way to do that properly is to use a proportioning valve to provide part of the flow and pressure to one and part to the other. At that point you wouldn't use a PB valve though, just a regular open center valve

But a regular open center valve without power beyond will provide flow downstream even if the spool is not centered with dual acting cylinders, but the downstream flow will just be what is being pushed out of the back side of the cylinder(S) being powered by the open spool, so you will lose a bit of power on the downstream valve, but it will still have some flow and pressure. Again, be careful that you don't try to lift something too heavy on the 3 point because the seal in the upstream cylinder is what is transferring the power and you don't want to cause a leak there.
 
(quoted from post at 10:53:50 11/11/17)
That is true and I did not mean simultaneous. How do you propose to use them simultaneously? Think carefully before answering....

Only way to do that properly is to use a proportioning valve to provide part of the flow and pressure to one and part to the other. At that point you wouldn't use a PB valve though, just a regular open center valve

But a regular open center valve without power beyond will provide flow downstream even if the spool is not centered with dual acting cylinders, but the downstream flow will just be what is being pushed out of the back side of the cylinder(S) being powered by the open spool, so you will lose a bit of power on the downstream valve, but it will still have some flow and pressure. Again, be careful that you don't try to lift something too heavy on the 3 point because the seal in the upstream cylinder is what is transferring the power and you don't want to cause a leak there.

A divider is one answer but it would have to have reverse flow checks. Without them it would work just like an open center valve.

And the problem with using an open center valve is this. Once both valves are active the cylinders are connected in series. The cylinders are operating independent loads and almost certainly have different cross sectional areas and mechanical advantages. As a result one set of cylinders is going to require a higher cylinder pressure than the other to operate. What you have at this point is a hydraulic teeter-totter. Consider this example:

Your loader has a 1500# load in the bucket and your 3pt has a 300# load on it. You start to raise the loader and half way to the top you pull the 3pt control up. What happens? There is no single right answer because we don't know what the cylinder pressures are but given the large disparity in loads I would expect that most likely the loader bucket is going to start to drop and the 3pt is going to raise. The loader will continue to drop until the 3pt cylinder is filled and fully extended and then the loader will start to raise again. Not only is that inconvenient it can be downright dangerous because the implement movements when the second valve is opened could be quite precipitous. This is another reason power beyond is used in these situations. It eliminates unexpected and unwanted interactions between the cylinders/valves that could potentially be dangerous.

TOH

PS> I have loader tractors and I have never attempted to raise the 3pt and loader at the same time. Not that I might not have had a need/desire - rather because I only have two hands ;-)
 
(quoted from post at 11:29:40 11/11/17)
(quoted from post at 10:53:50 11/11/17)
That is true and I did not mean simultaneous. How do you propose to use them simultaneously? Think carefully before answering....

Only way to do that properly is to use a proportioning valve to provide part of the flow and pressure to one and part to the other. At that point you wouldn't use a PB valve though, just a regular open center valve

But a regular open center valve without power beyond will provide flow downstream even if the spool is not centered with dual acting cylinders, but the downstream flow will just be what is being pushed out of the back side of the cylinder(S) being powered by the open spool, so you will lose a bit of power on the downstream valve, but it will still have some flow and pressure. Again, be careful that you don't try to lift something too heavy on the 3 point because the seal in the upstream cylinder is what is transferring the power and you don't want to cause a leak there.

A divider is one answer but it would have to have reverse flow checks. Without them it would work just like an open center valve.

And the problem with using an open center valve is this. Once both valves are active the cylinders are connected in series. The cylinders are operating independent loads and almost certainly have different cross sectional areas and mechanical advantages. As a result one set of cylinders is going to require a higher cylinder pressure than the other to operate. What you have at this point is a hydraulic teeter-totter. Consider this example:

Your loader has a 1500# load in the bucket and your 3pt has a 300# load on it. You start to raise the loader and half way to the top you pull the 3pt control up. What happens? There is no single right answer because we don't know what the cylinder pressures are but given the large disparity in loads I would expect that most likely the loader bucket is going to start to drop and the 3pt is going to raise. The loader will continue to drop until the 3pt cylinder is filled and fully extended and then the loader will start to raise again. Not only is that inconvenient it can be downright dangerous because the implement movements when the second valve is opened could be quite precipitous. This is another reason power beyond is used in these situations. It eliminates unexpected and unwanted interactions between the cylinders/valves that could potentially be dangerous.

TOH

PS> I have loader tractors and I have never attempted to raise the 3pt and loader at the same time. Not that I might not have had a need/desire - rather because I only have two hands ;-)

I guess I am the one that should have thought more carefully before answering :oops:

After a little more thought I saw my error. In my example both cylinders are in SERIES so neither cylinder can retract. Both will continue to extend and the upstream cylinder pressure will be the sum of both loads.. However once one comes to the end of it's stroke the other will stall at that point.

Mea Culpa

TOH
 

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