I have circuit question.  
Circuit is as follows:
- approx. 3 ton uneven load (i.e heavier on one side versus other) two cylinders rotating load, powered up and gravity down circuit.  PO (Pilot operated) checks mounted to blind end of cylinders.  Standard parker A & B to T (Motor spool) driving.  Using a cartridge style synchornizing flow divider/combiner between the valve and the cylinder.  The standard D03 bang bang valve flows approx. 14 gpm wide open which is way to fast for this application.  Currently have a heat generator/orfice in the A line which slows the assembly down and uses approx. .6 gpm to 1 gpm. (acceptable speed bad for the flow divider).

Three problems with this circuit:  with the third that I am looking for a solution at this time.

1.)  3 port pilot check valves are bad with paired cylinders in this situation due to the fact that the least loaded cylinder check will open first thus transferring the combined load to the second valve at double the pressure. (this is one problem)

2.)  Flow divider has a closed center function which allows a small amount of load holding capability.  When the driving D03 valve shifts to center (flow stops) the flow divider cartridge shifts to center, thus holding pressure between the flow divider and check valve mounted to the cylinder.  (No safety until the flow divider bleeds off pressure)  Thus the cylinder walks and is dangerous.

3.) and most troublesome of them all.  Uneven loading of cylinders without a mechanical timing device.  The flow divider at a low flow rate divides great/good and keeps the cylinders in time. In the combining mode(gravity down) the heavy side travels faster then the lighter side.  Thus the problem.  The flow divider is synchornizing which once the cylinders bottom in either direction the cylinders will level back out.  But I can not have the cylinders out of time due to other reasons.  I am looking for a possible economical fix for this.

Possible cost effective solutions for the third so far.
a.) inline flow control with free flow check..  Free flow for the up(dividing mode) and meter back out on the gravity down (combining mode of the flow divider).  Idea sounded possible and was better but still let the cylinders get out of time in the gravity down operation.

b.) size the heavier cylinder to the heavy load, have the ouput rod end oil be the fill for the blind end on the lighter side.  Have not tried in this application but have in others..  Bleeding air out of the cross line from one cylinder to the other is not fun.

c.) turn circuit into powered up and down, place heat generators/orfices on all lines, size the orfices accordingly to get the desired speed out of both cylinders depending on the loading conditions???  Might work but kinda farmer like and produces alot of heat.

d.) Expensive method, two piston motors tied together with a coupler for a flow divider.  Expensive but would work. $2000.00(ouch) for pistion flow divider

Does anyone have any ideas besides mechanically timing the system.

My advice would be...

1) Have a cup of coffee.
2) Have another cup of coffee.
3) Big problem with P' O' check valves...throw them away and use overcentre valves or counterbalance valves to hold the load. Intergrated Hydraulics and Sun Hydraulics both have good quality, cost effective valves and manifolds.

4) Chuck the flow divider away and replace it with a rotary geared flow divider...Rotary flow dividers have a much wider operating range...the faster they run the more efficient they are. Delta Power do an economical one.

As with most hydraulic systems the degree of accuracy depends on the amount of cash you throw at the job.

Having said that...changing the P' O' checks and the flow divider will be a cost effective solution.

Drive the cylinders in both directions...flow dividers don't work as flow combiners if the cylinders are not mechanically linked together...the lighter cylinder will always move before the heavier cylinder or in vertical applications the heavier load will move first because gravity makes it easier.

You will need 2 directional control valves. Put the flow divider before the valves...divide the flow between the valves and operate the valves to change the direction of the cylinder.

If you can, you should remove the chokes and install a flow control valve before the flow divider...it's not the best way to control the speed but it will be the easiest to install.

I am assuming that you have a fixed displacement pump...you might want to consider resizing the pump to avoid excessive heat generation or even better use a variable pump.

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