6 replies to this topic

[NSwanberg]

I did not know... or did I just forget?

 

[stoo23]

  Hmmm... perhaps both?? 

 

I'm not 100% sure if all the 917 chassis were made of lightweight gas-filled tubing, but most definitely... the very early ones were.

Most were of welded aluminium, but I think perhaps three were made using magnesium.

 

There are a number of fantastic stories by both Frank Gardner (Always a Great Story teller, if sometimes creatively related / remembered lol) and David Piper about their experiences driving one of the very early cars at a very wet and snowy Nürburgring in 1969.

 

A somewhat scary experience to say the least it would seem!!

 

 Scary at the best of times and perhaps even More so when seen Naked like this !!!   

 

 

This Must be a later chassis due to the lack of Side Exhausts.

[Cheater]

Nice video, Nelson. Thanks for posting it.

I think it was David Hobbs would said the early 917 was the only car he drove in his carrer that abolutely frightened him.

 

I do feel the chassis would be more accurately described as "pressurized," as opposed to inflated.

 

Porsche was relentless in their program of reducing weight in this series of cars. There's a pic in one of my Porsche books showing the ignition ballast resistor fitted to many of the 917s. It's a block of balsa wood wrapped with some turns of Nichrome wire, as it was lighter than any other type of ballast resistor they could find!

[Isaac S.]

Stewart is correct, 917Ks are some of my favorite foreign cars.

 

Most of the 917Ks chassis were magnesium and aluminum but I think all of the 917 Can-Am cars were nitrogen filled.  

[Dave Crevie]

Only the 917-10s and 917-30s had magnesium space frames; the rest of the series had aluminum tubes.

 

When I helped John Bohlander work on Sandy MacArthur's 917K, so many years ago, I asked him what the plug in the frame tube near the rear of the car was for. He told me it was to fill the frame with nitrogen for a leak-down test to check for cracks. I thought about that for a while, and realized that on every joint the tubes would not only have to be ground out to fit close, but they needed to remove the area of the tube which would be covered by the end of the adjoining tube. Otherwise, gas could not pass from tube to tube. There are a lot of tubes in that frame. I can't imagine how many hours it must have taken to construct one of those frames.

 

John interned at the Weissach works, and until his untimely death from a brain tumor, was considered one of the top mechanics for racing Porsches. He was there when they were building the 917-30s. He told me the story on how they normalized the frames on all the 917s, and how they had to spend hours straightening the frame afterward. Then normalize again. 

 

By the way, even the ignition keys on Porsche factory race cars are drilled for lightness.    

[Martin]

Dave,

 

For 35 years all the NHRA Prostock M/C and car frames I built had the air in the frame feature. I would mark where the tube lands then drill a 1/4'' hole to leak them all together. Once welded, I would fill with 120 psi then look for leaks with a soapy water bottle. Really made you focus on weld starts, stops, and the crotches. 

 

This was used as an air tank to power the air ram to shift gears. Plenty of air for drag racing.

 

It had the added benefit of knowing it was crack free. I did not know the 917 had this arrangement. 

[Paul Lindewall]

For 35 years all the NHRA Prostock M/C and car frames I built had the air in the frame feature. I would mark where the tube lands then drill a 1/4'' hole to leak them all together. Once welded, I would fill with 120 psi then look for leaks with a soapy water bottle. Really made you focus on weld starts, stops, and the crotches.  

 

We did the same thing at the kart shop I worked part time at long ago. The guy that did the welding at the shop was an artist, but still we checked.