Quote Originally Posted by Chris 16409 View Post
Tom, I didn't mention in my other posts, but I am in for a pair of your authentic German made Stabilus door struts.
Chris, you did mention it a while ago. Your name is on my pre-order list at number 18 and I will contact you as soon as the struts are ready.

Quote Originally Posted by chris williams View Post
All very interesting, perhaps I have fake ones then! I will have to go and get some part numbers from them, If I can remove the stickers!
Chris, it would be great if you could get the part numbers off of them. I can call Stabilus and confirm it since they have ALL the part numbers they ever produced. With the part number there should be a production date. When you look at the cylinder you should see all those warnings and under that should be a part number consisting of 6 digits, a force of 1200N and production date. In case of my old struts from one of my cars it looks like this:
867691 1200N 204/98
Part #, force, production date 1998

Quote Originally Posted by Bitsyncmaster View Post
You may not want the struts specified the same as original if they now have "soft lift" operation. I would think a little more force would make them last longer since the soft lift prevents bounce.

It's also interesting John now has soft lift for all the struts. I don't see the need of soft lift on the others but again specifying more force would make them last longer.
Having stronger door struts might create more problems and will not really make them last longer. This is coming from the experts at Stabilus and other manufacturers I'm in touch with. Here's what I know:

More force will put more load on the strut mounts. The lower mount which is attached to the fiberglass body is very weak and actually it is too weak for the original force. The bracket bends, deforms and eventually comes off as the fiberglass around cracks. I will post pictures later on today... You should inspect your lower bracket to make sure it's not bending. Open the door and look at the lower door strut mount. It should be pointing straight towards the front of the car. If you see that it's starting to point outward the bracket is bent. I will be offering stainless steel reinforced brackets with the struts to fix this issue and prevent a disaster.

More force would not really extend the useful life of the struts by much. Higher pressure will cause higher leak rates and the struts will only last a little longer.

More force will mean more effort to close the door and more stress on the door structure and rear hinges.

The strut size used for the DeLorean doors (10mm piston rod, 22mm cylinder) has an absolute maximum force of 1200N with recommended maximum at 1100N. No sensible manufacturer will go above the 1200N max limit.

Original force of 1200N with properly adjusted torsion bar should provide between 10 and 15 LBS (about 5 - 7 kg) of force holding the door fully open. If you go higher this force will increase, if you go lower the door might sag in cold weather.

The 1200N is measured with the strut fully extended. As you push it in (collapse it) the force increases at a predetermined progression rate. At fully collapsed the force is higher. This progression is dependent on damping and the more damping you need the higher the max force will be. So, a nice soft lift is usually accomplished by adding more damping (it's where the struts slows down at the end of travel) and more friction on extension. The problem with that is more damping causes more progression and in the end the max force with the doors closed might be too much for the fiberglass body and the lower mount. If you raise the initial force you have to add more damping to prevent strong bounce and in turn this will increase the collapsed force. If you make a 1400N strut the resulting progression might cause the collapsed force to increase to well over 2000N and that will result in a loud crack and a snap. Adding more friction to slow down the extension causes more wear on the seals and the piston rod shortening the useful life of the strut. The higher the force the more friction is needed to slow it down.

As you can see making gas struts is not as simple as it might seem. I learned all this just recently as I started working on them. It's seems like a simple tube with gas inside but in reality it is a very complex piece of engineering. Making a good strut is a matter of finding the best mix of force, speed, damping, progression and not to forget critical dimensions.