[kyzyl]

FWIW, we certainly can make synchronized tandem lifts, but as always it comes down to costs. Basically if you want both actuators to move in unison, you either need to directly link them mechanically, which is expensive to build/repair, and not very feasible over large distances, or you need to connect them electrically via their control signals.

In the latter case, you would usually synchronize their controller clocks, and specify the motors/cylinders/whatever to both have a very tight positioning tolerance. Then you mount the surface being moved on a system of bearings that have enough freedom s.t. it will self center automatically, absorbing the tiny bit of misalignment that can (and WILL) occur.

However, in my experience it's almost always better to use two passive, i.e. non-lifting, supports along with one actuator in the middle that is twice as powerful. In heavy lift applications it often comes down to getting a single cylinder that is powerful enough without blowing the cost through the roof. Nevertheless, if you look at marine architecture, airport gangways, earth moving machinery etc. you will often see just a single lifting point.

And in three paragraphs we've gone from office chair pistons to front-end loaders! Yay HN! As I said... for what it's worth ;-)