Different gas fills will get you different stand heights. That is why I simply fill up to desired stand heights on wheels, nothing else matters. Allright, having to fill up at those pressures by Schrader valve is a bit awkward, a screwed on adapter will be a good idea, not just like with car tires.
Just had another idea: Why not use CO2 cylinders for pressurizing struts ? Could be had from welding companies easily, less so with nitrogen I guess.
I guess it might have something to do with that CO2 is a liquid at relatively low pressures and so the pressure you get from the bottle is highly temperature dependent – around 60 bar / 870 psi at 22 degrees and less than 40 bar / 580 psi at 0 degrees.
High pressure Nitrogen is widely available from industrial suppliers, and cheap.
Helium would leak past the seals very quickly.
Yes; I posted the disposable cylinder details above.
There is however a funny problem with these, which nobody selling them is willing or able to discuss, and I suspect nobody knows: the thing which screws onto them
is a regulator. There seem to be no simple valves. When you unscrew the knob, it pushes a pin into the cylinder valve, which is required, but a “regulator” is not desired. The text says 4 bar output (60psi) which is nonsense; it is actually about 700psi. One cannot obtain the full cylinder pressure without constructing something, which will be my next job.
The pic shows an outlet for a plastic tube, which I obviously replaced with something much more robust.
The diagram posted by Cobalt above shows how you can get dry ice with CO2, without having to go “properly cryogenic”.
There seem to be no simple valves
One cannot obtain the full cylinder pressure without constructing something, which will be my next job
Good point.
It’ll be interesting to see what you come up with.
you want a regulator on the disposable cylinder, with output up to 50-100 bar ?
I just want an outlet valve. No regulator. I already have the filling rig above.
The thread is M10; 1mm pitch IIRC. I have plenty of the fittings but the only way one can buy them is as a regulator.
The “complication” is that the cylinder valve has a pin which needs to be pushed down to open the flow.
A simple enough engineering exercise but an irritation to discover the reason why the gas isn’t coming out 
The other thing is that all these “regulators” bleed a bit of air as you screw them on – because the pin already sticks out a bit.
The obvious way to disable the regulator function is to replace that spring with a piece of solid tube.
You have made the same thing except you have a DIN valve fitting, presumably for scuba cylinders.
Why do I bother using these crappy cylinders? Because anything above is rental-only, around 100 quid a year, plus 20 quid for a swap/refill.
I am still laughing at Cobalt’s cruel demolition of my concern (albeit widely posted) that 2000psi + will be needed 
Peter wrote:
I am still laughing at Cobalt’s cruel demolition of my concern (albeit widely posted) that 2000psi + will be needed
You’re welcome.
An hour on the lathe and voila
Works perfectly
and zero gas loss when it is screwed onto the cylinder. The old design is an incredibly stupid idea. You probably lose about 5% of the cylinder content on each attachment.
