Wrong place to ‘save weight’

Builders;

Smoky Yunick, was famous for the quote ‘In 50 years of racing, from Baja to Bonnieville and from Daytona to Indy, I have seen a great many things, but I have never seen a blown motor win a race.’

.

Yunick was one of the great communicators of practial mechanical experience. I have read most of what he published, the copies of his books I own are all well worn, dog eared and full of notes in the margins. He was very clear on one point: most engine failures he had seen in modified engines came from one source: People trying to make parts lighter. To Yunick, the idea was simple; if it did not run on the last lap, you could not win, therefore any theoretical advantage of a lightend part wasn’t worth it. In airplanes, this is ten times as true.

.

Below is a picture of a Corvair piston. It is from an forced landing several years ago. An engine failure leading to a forced landing, which fortunately ended in no injuries and light damage to the aircraft.

.

I came across this souvineer cleaning up. It was in the #5 position of a flying motor when the #6 piston grenaded. There was little of #6 to tell the story, but #5 told the tale: Look at the wall thickness of the wrist pin. Next to it is a stock wrist pin, three times as thick. Neither the guy who owned the plane nor the guy who assembled the motor saw this comming. The pistons had been purchased years earlier, and then donated to another builder. Lost along the way was the fact they were ordered with incredibly light pins, made by a company which I later found out went bankrupt after a number of failures. The total weight savings in the engine had been less than a pound, but it had been the cause of the failure. The same plane is flying today with regular wrist pins.

.

When I wrote in my manual:

“Nothing you get in exchange for reliablity was a good trade, in aircraft weight isn’t the most importiant factor, reliablity is” 

I’m not speaking theoreticaly. I have a lots of souvineers in my hangar, where builders wanted to ‘try something better’. I have quite enough, avoid all temptation to add one to my collection. Thanks.

.

.

Smokey Yunick was one of the most colorful mechanical Americans of all time. He was both an aviator and a motorsports innovator of the first order. He was a prolific practical tester and technical writer. He lived in Daytona Beach for 50 years, and he was unusually accesible; when I was a student at Embry-Riddle I drove over to his shop on Beach Street to ask him a technical question. His Garage appeared closed, but his daughter had a pet shop next door, and if she thought your question was valid she would pick up a phone and say “Dad, can you come up front?” and the man himself would apear and walk you inside and answer your question. Yes, a man who designed and built cars that won both the Daytona and Indy 500 was generious like that. Take a minute and read his story: https://en.wikipedia.org/wiki/Smokey_Yunick

.

Wewjr.

.