Assistance with locating a hydraulic flow divider

[B. Elliott]

At my shop we recently acquired an old 2-post automotive lift from the 70's. The lift has two cylinders, one for each post. The hydraulic lines were a bit hacked up when we got it and we're now in the process of trying to get it up and running again. We have it operational, but the arms are rising and lowering unevenly.

We're looking for some type of flow divider where we can adjust the amount of flow that is fed to either piston with 1-in and 2-out. For example, a 20/80 split, 50/50, or a 75/25. Something where we can fine tune it so that they will rise and lower at equal speeds.

~3000-3500 psi
3/8th NPT

We're having trouble sifting through all the available types on the market. Most of what we have found are priority-type, but that's not what we're looking for.

Any assistance would be greatly appreciated!

 

[Baluncore]

Your hydraulic cylinders should be of equal section. That will require exactly equal volumes of fluid pass to, or from each side. Because the mass distribution being lifted or lowered will not always be symmetrical, the pressure to the two sides of the lift may be significantly different.

So what you need is an accurate equal flow divider that is quite insensitive to pressure difference. Gear based, rotary flow dividers are maybe 3% accurate, so that should do the job OK. The differential pressure between the two sides will be countered by the torque difference on the gears in the flow divider.
http://www.salami.it/public/articoli/pdf/1608_1_Technical%20catalogue%202DRE.pdf

A mechanical solution could be to run a single loop of wire cable up, down and between both legs. That will need 6 pulleys. By clamping the lift points to the appropriate cable you can mechanically balance the pressure and the position on the two sides, the cylinder pressures can then be equal and so will work together. In that situation the actuator cylinder sections do not have to be identical.

 

[B. Elliott]

Thank you very much Baluncore. That information is exactly what we were looking for!

Cheers!

 

[Brad644]

A pressure regulator could be used 1 in 2 out adjusting the pressures to get both rams to work together. also can check the distances between both pipes, also have found if the rams are not bled properly and have small amount of air inside could be an issue. On one instance I found that the I/d of pipes where different thus giving different pressures. Thus a pressure regulator would be best option giving pressure equally if a load is put on.