Mark Anderson

Jerry I have a strange idea. I think most of us appreciate the time and energy to you put in your 928 parts. Why not list several of your ideas and let the public vote of which ones they feel would be the most beneficial?
Like Greg said its not like there is a shortage of good used one available.

Jerry Feather

Thanks Mark for your input. First of all, the things that I might come up with are "Jerry Built" not "jury built" and those are not close to the same. Second, just about anybody, including me, does not have a very good idea about just what might be "beneficial." Finally, based on my now limited, but exclusive experience with one of these, since I am the only one who has ever taken one of them apart, I have a strong suspicion that there is a good chance that all of these now 40 to 50 years old, whether or not collapsed some or all of the way, may very well be completely or even partly dry. What have you ever done to be sure in fact that one you sell that is fully extended is also still in fact a "good used one" with any fluid in it?

Mark Anderson

We do measure them and if they showed any signs of leaking we would toss them ( much like a bad shock absorber)

icsamerica

I don't really think spring or hydraulic really matters. About 2 years ago i watched someone on a cell phone roll into the back of my 928. No damage but the "bumper shocks compressed" I don't know exactly how fast the driver was going but it was a slow roll and well under 10 mph. I cant see how those bumper shock would be meaningful in a collision say at 30 MPH which would have much higher forces.

These bumper shocks may be for the 5 MPH bumper requirement that came into effect around 1974. Although I'm no no expert on the subject, I don't think they can do much else and offer no safety margin above 5 mph. I have a similar bumper device on my 70's Jaguars which I've also opened with a modest pop. These systems were probably based on a literal, best effort, or somewhat incorrect interpretation of the law / regulations at the time and they clearly have evolved over time. Back then the car was crash tested and production started, parts contracts signed so no good reason to redesign as regulations evolved especially for low production cars.

I just replaced the bumper on my 7400Lb Cadillac Escalade. Behind the bumper is a large piece of white styrofoam and then a 100% rigid steel bar. That's cost cutting and product evolution.

Are any of the original designers still alive? It would be interesting to ask them the answer to this and many other questions. My first question would be to explain the LCA bushing design. My 2nd question would be why an aluminum ball joint? My 3rd question would be, Were changes in tire width and design tested and accounted for in the behavior of the Weissach axle? I could go on and on but the bumper shock question would be low on the list.


https://www.curbsideclassic.com/vint...-saving-money/

My reading of the law suggest Porsche was non-compliant becasue in 1979 collisions at 5 MPH or less were supposed to result in ZERO damage. A pushed in shock damper that requires bumper removal to repair and replace is NOT zero damage. My 70's Jag bumper will compress and then return to their original state so I can see how that's complient. 70's Jag Bumpers like many at the time look like add'ons and are bulky and ugly.

I would be more interesting to me if someone would put a good bumper strut in a press and then measure the force it takes to compress it.

soontobered84

Jerry,
The cowlings you make and sell are beneficial.
The early model splash shields (belly pans) are beneficial
The rear hatch under carpet battery covers are beneficial
The bushings for the boosted injectors you made for Darien are apparently beneficial.

Let us know what products you already have, and the products you are planning, and we can help you prioritize

Jerry Feather

I know, Mark, and that is really all you can do. However, the collapsed one I took apart was fully collapsed and still showed no sign of leakage, but it was completely dry inside.. That is why I am concerned about any that are partly collapsed or even still fully extended - - no sign of leakage, but still might very well be completely or at least partly dry.

Speedtoys

Thats not a practical example and not how the rules were written at all. You cant have zero, something has energy to absorb..somewhere, and that will create 'damage' to something that is not in the same condition as it was before...and therefore a loss to insurance. The idea was the common parking lot claims, needed to come down in consumer costs.

1971 were the first standards. (FMVSS) 215.
1972-1978 were the next set of rules.
No collision damage to headlamps and fuel systems at 5 mph for front bumpers and 2.5 mph for rear bumpers
1979 the 'Phase 1' standard
Prohibits any damage to safety-related parts and exterior vehicle surfaces at 5 mph, but did not limit damage to the bumper system.
1980-1982 'Phase 2'
Withstand a 5-mph impact with no safety system damage and no damage to the bumper exceeding a 3/8-inch dent and no more than 3/4-inch displacement.
1983 went back to 'Phase 1'
Impact speeds were lowered to 2.5 mph for front and rear collisions and 1.5 mph for corner impacts, and Phase I damage criteria was reinstated.

Manufacturers can provide the required impact protection by any means they chose.

Speedtoys

Probably not much at all.

It's about capturing and damping a sudden force, not a slow application of it. It's really just a "tight" non-returning shock absorber. They operate the same way. Its not about load, its about force and damping.

YOU can push in a shock over 20-30 seconds, not a tall order, but do it in .5 seconds bare handed, you cant.

At the track we have shock dyno's for this purpose, to test compliance with spec rules.

Jerry Feather

I received the three struts Stan sent me. However I find that they are all collapsed only a few millimeters. That means that in order to cut them apart I have to have them fully collapsed. That is because I cannot cut through both the outer and inner skins/sleeves unless they are locked together in the fully collapse position. It is going to be interesting to see if there is any fluid left in them.

Even then, based on what I have found so far, and may find further with the fully collapsed strut from the other side of my 85, I find that there is too much of a chance that any one of these struts, whether collapsed any or not, and maybe even a new one off the shelf, particularly NOS, may very well be low on or empty of fluid. There is really no way of telling. What that means for me is that I now have to forge ahead with this project of converting to a spring, and that will probably be without regard to any given MPH of impact, and that is even if the only ones I do are for my own cars.

In fact I think my motto for these is going to something like "boing at any speed."

Jerry Feather

This morning I cut the other of the collapsed struts from my 85 open in my lathe. I cut thru the bottom end of it at just above what I thought was the tight spot and I cut through both inner and outer shells down to the plug swagged into the bottom end of the inner shell. That is the plug that the connecting rod passes through. To my surprise my cut(s) did not allow the separation of the inner and outer shells and does not allow even any movement with some hammering. However, I was able to clamp the bottom piece cut away in my mill vise and then hammer all the rest of the strut off of the cylinder inside the inner shell. That leaves the inner and outer shell stuck together and the cylinder, piston assembly connected to the cut free bottom piece of the strut by the connecting rod.

When I was able to start the cylinder assembly coming out, as soon as the bottom plug came free there was a small gush of greenish fluid from the opening. It appeared to be about an ounce and it filled part of the trough on my mill vise only part of the way on one side. The fluid has no smell and it does not feel oily or even soapy. It actually seems kind of like it is water based. I have not seen anything like it before except perhaps antifreeze. Now there is a thought. I was able to mop most of it up with a coupe of sheets of blue paper shop towels that were laying nearby and finished up with a clean sheet. Later, in only a few minutes, I noticed that the clean sheet was completely dry; and about an hour later after laying the first two sheets outside they too are completely dry and with no sign of any residue from the fluid.

It does not appear to me that the cylinder cavity was completely full of fluid and the seal at the bottom, contrary to the first one I opened up, appears fully intact. There is no sign of any leakage of fluid on the outside of the strut even though it has been fully collapsed.

Jerry Feather

I am beginning to think that it is getting close to the time that we or I ought to be asking the question about why BOGE printed the warning on all of these struts that says DO NOT OPEN. I think Greg had a very logical tentative answer to that about hydraulic oil being under pressure and leading the a risk of injury from a squirt of it. However, so far I have found no oil or other fluid under any pressure in the two struts I have opened up. I wonder what other reason there might be for the warning. I have some thoughts about that that I am going to try to further develop.

rcrone928

Jerry. Could you drill some holes above the piston in the full extended position and fill with low low density poly ?

Jfrahm

If good used ones become unobtanium then I think filling them with silicone or something would be a decent option. If they have to be cut apart and the absorption system replaced perhaps a collapsible tube or a loose roll of sheet metal would be better than a spring. The metal could be diagonally pre-folded and unfolded to seed the collapse.

Or maybe just use relatively fine hardware cloth rolled into a tube?

Mrmerlin

try shaking them and listen for the oil sloshing

Jerry Feather

Stan, I think the darn things are just too heavy to either hear or feel any slosh inside them; and besides, the space the fluid is supposed to be in is so broken up with the cylinder inside the inside sleeve and with the connecting rod and piston there it probably does not really slosh.