Your invitation to an intelligent discussion on vintage Porsche safety, Or random thoughts and a lot of questions, anyway.... Options

[horizontally-opposed]

The current post about r_towle's son and his close call with his 914 and a tree has been weighing heavily on me. It has also reminded me why it's important to be thankful to those who engineered the cars so well so long ago.

I posted the below in that thread in response to pictures of a race car with a ton of tubes in the floor to prevent intrusion, but think the subject probably deserves a thread of its own, and that it belongs in the Garage for several reasons, but mainly so the maximum brain trust can have its input. What we need is experienced minds, willing to think unconventionally about how to maximize our chances in the event of a collision on the road, track, or autocross.

I'm not sure I see roll bars as the solution, especially for street cars (and ESPECIALLY if it means your head is next to a nice, über hard bar), but I sure am willing to listen. Anyone who has experience with real crash testing or knowledge of applicable physics would be especially valued here.

Now, to my original post:

As to the bar-laden floor in the race car pictured above, it certainly looks like it will be harder for things to intrude into the cabin in the (let's hope VERY unlikely) event of an impact like the one seen in this thread.

However, one has to wonder if the energy absorbed by the 914 in this instance didn't play a part in preserving the lives of the two kids in the 914. Its "give" took a big chunk of the wallop out of what those kids would have experienced had there been rigid bars there, and the result (I suspect, but you'd have to do an extensive study to find out) was that their necks were subjected to a slightly lesser impact and their internals didn't have to slow down quite as quickly.

If the tree or pole had entered the cockpit a couple of feet back, it would have been a different story, of course. This demonstrates the erratic nature of car "accidents" and the difficulty (impossibility?) that faces engineers as they try to protect occupants. I think about the C-GT fatality in Fontana (having driven a C-GT there just before it happened...) and what killed those two was a side impact in which nothing intruded but the car simply came to a stop too quickly, too instantly. Their necks' didn't have much of a chance, if any. I sometimes wonder if they would have done better without helmets.

I've been thinking a lot about safety of late, and very unconventionally. Not so much because I think we should ditch helmets, HANS devices, etc., but because I think we should really be considering the lessons learned in production-car crash test engineering and how they might be adapted for race cars. Good seats are another key, and I agree with Patrick Long that we should modernize old race cars with modern seats, and wear HANS with helmets out there (extra weight of the helmet makes things tougher on your neck).

Problem is, all this is expensive, and I've seen very little discussion about how HANS or similar devices work without harnesses, i.e. with 3-point belts. Which then makes me wonder if those who autocross are actually less safe in modern street cars with a helmet on. Airbags and full-face helmets are just one thing that come to mind...

This is a hard subject, but there are good lessons for all of us to learn as we consider it.

The best news is we aren't studying it in tragedy with re: to Rocket. And for that, I am very, very thankful.

So let's learn from this near miss together...

pete

[Dave_Darling]

Race cars are race cars; street cars are street cars. We try to cross the line, make something that is both, but it really does compromise both.

In a race car, you have a stiff structure around you, you have seats that are good at keeping you in one place, belts that make sure you stay in that place, safety netting to make sure no parts of you (say your arms) get into a different area, helmets to make sure your skull stays intact, and head/neck restraints to make sure your neck doesn't break. Everything is very solid, very stiff, and you are very very supported and your movement is contained. Your body decelerates at pretty close to the same rate as the rest of the car, though there is some "give" in the belts and the seat mounting generally. One of the most important things is to prevent any intrusions into the driver's area, because decelerating the driver is something that the seat/belts/HANS/nets/etc. already deal with.

Street cars rely much more on energy absorption. Crumple zones being the main example that comes to mind. Those absorb some of the energy from a crash, and extend the amount of time that it takes to decelerate (or less often, accelerate) the car and the occupants. The occupants of the car are much less restrained, even in cases where the belts "pre-tension" and sixty-eight airbags go off. This means they continue to move at the same rate the car used to be moving at, and then get decelerated when they hit something--the limit of travel of the belt, the airbag, the dashboard, the windshield, the steering wheel.... So you really need for the rest of the car to be slowing more gradually, so there isn't as large a speed difference when the occupants hit it.

These two systems work quite differently. The street car has to decelerate more gently than the race car, so it crushes around the cockpit. The race car can decelerate less gently, so it can be strong and stiff to prevent anything "else" from getting too close to the driver. The street car also has to protect anyone sitting in all seats in the vehicle, while the race car only has one person in it. That gives less leeway in where the street car can crush (e.g., if the passenger seat area always crumpled, that's OK in a race car that never has a passenger...).

The safety systems in a car are indeed systems. In particular, modern street cars and modern race cars have been engineered so their parts all work together in the event of a wreck. Older cars were not always the recipients of such careful thought, but there are certainly places where some of them got it right.

Check the front and rear of the 914, for instance. Huuuuuuuge crumple zones! You are generally going to be a lot safer getting hit from the front or the rear in a 914 than getting hit in the side.

What can you do do shore up the side-impact capabilities of a 914? You could raise it back up to factory ride height. The longitudinal under the door is pretty strong, and gives you at least a little crush room--if it isn't below the bumper of the car hitting you. You can install mid-73 or later doors. These have the (heavy) beams inside them. Or you could go beyond that, and build a structure inside the door that is stronger. Of course, you have to rely on the door latches and such, plus the fact that there are gaps between the doors and the body. So you could gut the doors, weld them in place, and build "NASCAR bars" inside them. Plus you probably don't want them to be strong enough that they never crush at all...

Of course, you start reducing the streetability of the car pretty quickly at that point.

I don't really have any good ideas on what you can do to make a 914 a more crash-worthy street car. I've done some thinking about it, and every thing I have personally thought of is a compromise of some kind, making the 914 less of a street car...

--DD