Reusable adjustable Gas strut/spring

[transatlantic]

I'm wondering if there is any contraption out there that is like a gas strut or spring, where you can continually adjust (increase or decrease) the force needed to compress the mechanism?

I know that you can buy adjustable gas struts, but once you let the pressure out using the valve, there is not going back.

My thinking was that there might be a gas strut that allowed you to reduce the area containing the gas (when expanded) with a wrench or something, thus allowing you to increase or decrease the force required to compress it.

My other thought is to simply provide some mechaism that allows you to adjust the mechanical advantage point of the gas strut installation.

 

[AndyT]

I think door closers are adjustable like you want, but may be too big and clumsy for anything other than their original purpose.

 

[Myfordman]

Adjustable gas struts can be recharged if you go too far but by far the best method is an adjustable fulcrum on a test set up and fix them once you know where it needs to go.
With a bit of cunning you can make then have an over centre action to give both a counterbalance and a "keep shut function"