Synchronise Rams

Synchronise Rams
Over the years I have seen many methods used to synchronise hydraulic rams, some successful and some bordering on the bazaar.
Getting rams to move together can be tricky and applications like “ A frame” cranes can be potentially dangerous if the wrong method is used.
The simplest method is to join rams together using a mechanical strut / beam that is strong enough to take any out of balance forces. We often see rams used this way on Skip Lorries where the two rams are joined together with a cross beam and the input flow split using just equal lengths of pipe work.
More accurate control can be effective with flow divider valves, gear and piston motor types. These offer more better control with accuracy between 5-10% of stroke but as wear increases these figures will also increase.
The most accurate form of synchronisation will be achieved using a servo closed loop control with linear transducer feedback. One cylinder will be driven whilst the other slaved.
I have also used NC valves with stepper motor control. Using one digital input signal to two stepper motors that drive the NC valves. This has its own inbuilt mechanical feedback mechanism that can synchronise rams to just a few microns even with an off centre load.