On Nov 12, 10:20*am, "Dave, I can't do that"
wrote:
On Nov 11, 3:47 pm, Winston wrote:

Hi Winston, thanks for the reply but it is not quite that simple. The
gas spring has to compress almost fully during about 80% of the door
movement when closing, then it passes a toggle point and the gas
spring begins to extend again to provide the holding pressure....

Dave

I solved a similar problem with the hydraulic cylinder geometry on my
front end loader by drawing the parts to scale and using a ruler
marked with the extended and retracted lengths for the hypotenuse.