917 engine pics, been looking for a 908...but its cool Options

[r_towle]

what an amazing piece of mechanical enginering...

http://www.pbase.com/917carl/917_12_cyl_engine

[BigD9146gt]

Helium making the chassis lighter? I don't think so. Yes, helium is lighter than air, but by the time you pressurize it, your probably looking at the same mass as atmospheric pressure (14.7 psi/1 bar) air in the tubes would be. Now what would be lighter is if they sucked all the air out of the tubes and made it a vacuum.. less mass in the tubes, less mass overall.

The reason why the put helium in the tubes is because the welds need it on the backside to be stronger. "Perge" is the term used to weld tubing that needs to be structurally strong, stainless is one metal that REALLY shows a difference. When you purge those metals, if fact any metal for that matter, the opposite side that would normally be exposed to oxygen now is sheilded by the inert gas, making the back side of the weld look almost like the front side.

TIG welding, which is sometimes refurred to as Heli Arc, is what they had back in those days. The company that came up with the TIG welder was called "Heli Arc Co.". Now I would assume they named their company that because they first used helium as the inert sheild for welding, but thats not the reason why TIG welding is refurred as Heli-Arc. Kind of like "Vice Grip" or "Allen wrench", they are name brands.

The drivers were nerveous because they were in an 800hp car that weighed ~1700lbs and had horrible aero dynamics. Vic Elford finally became their test driver, and with his rally experience, he, more than any other driver, helped develop the 917's.