Re: AW: [DML] Door Gas Struts life Span

[Martin Gutkowski <webmaster@xxxx>]

Hi Elvis

I know what you mean, but you're not correct to say "there's always the 
same pressure". A gas strut works like this: It's basically a simple 
piston assembly. The only difference is gas is able to flow from one end 
of the barrel to the other. I've never taken one apart so I'm not sure 
how it's done, but would guess there're grooves machined into the wall 
of the bore. As the piston is compressed, gas flows from the base end to 
the rod end, but of course the more the strut is compressed, the more 
volume is taken up by the rod itself, so the highest pressure (and the 
geatest "push" from the piston) comes when the rod is fully retracted. 
The force exerted on the rod is proportional to the cross sectional area 
of the rod only, NOT the bore. [This principle is used in hydraulics 
when implementing "regeneration" - the pressurising of both ends of the 
ram by the same amount, but creating an imbalance in force because of 
the cross-sectional area of the rod, allowing you to shift the piston by 
only passing the volume of the rod through the pump, and not the volume 
of the whole bore]. The speed the strut moves is set by the size of the 
grooves (or whatever) that pass the gas from one end to the other. Make 
a smaller groove, the slower the piston will move - this is how the 
"brake" is acheved. It does not reduce the force of the strut.

Make sense?

Martin

Elvis Nocita wrote:

> Tom, what do you mean with the gas spring is compressed while in non-use ?
>
> You should take a look at the Lift-O-Mat homepage. There's always the
> same pressure inside the spring, no matter if compressed or not.
>
> I mentioned it before - the German Delorean Club sells adjustable and 
> refillable gas struts. No more messing around with torsion bars !