Below is a short write-up on the architectural style of our house

Thursday, 2 January 2014

The Porsche 917 – a true legend

The Porsche 917 is the race car that gave Porsche its first overall wins at the 24 Hours of Le Mans in 1970 and 1971.
In this post I hope to provide some background about what made the iconic Porsche 917 so special, and take a look at its lasting impact on racing and popular culture.

The 917 display at the Porsche Museum
I was fortunate enough to visit the Porsche Museum in Stuttgart that has a number of 917’s on display. I also attended the Classic Le Mans race in 2012 with my son. There were a number of 917’s racing at the event.

If someone were to make a list of the greatest race cars ever made, the Porsche 917 would almost certainly have to be on it. In fact, the 917 makes a pretty good case for itself to be the greatest race car of all time.

Want some proof? How about how with some iterations of the car rated between 1,110 and 1,500 horsepower, it remains one of the most powerful race cars ever made -- not bad for a car that competed in the early 1970's. 

Click here to see and hear the 917 in action. 

Le Mans movie poster starring
Steve McQueen
Then there's how the car dominated at the track, securing multiple victories at the 24 Hours of Le Mans, Daytona, Watkins Glen and a host of other events and tracks. The car was also immortalized in the Steve McQueen film "Le Mans," which included footage of its victory in that race in 1970.

There are many more reasons why the 917 is considered among the all-time greats. If you don't immediately recognize those three numbers, don't worry -- you've probably seen the car in photographs somewhere.

Porsche 917 in Gulf Oil livery

With the car's low, wide shape that included a tapering tail at the back, swooping front fenders and massive tires, it looked especially striking in its iconic blue-and-orange Gulf Oil livery. Yes, it's that car!

According to Porsche, when 50 international motor sports experts from the British magazine Motor Sport were asked to name the greatest racing car in history, they cited the Porsche 917.

But while its reputation is considerable today, the 917 got off to a rocky start in the late 1960's when Porsche struggled to build enough examples of the car to qualify for competition. Then they had trouble finding drivers brave enough to drive the beast, whose power far outpaced its handling. It was also initially plagued with development problems. But Porsche persevered with the 917, and after some tweaks, the German automaker had a more than just a winner on their hands -- they had the makings of a legend.

Porsche 917 Development

Development of the Porsche 917 race car came about due to a rule change in motor sports. In 1968, the Federation Internationale de l'Automobile, the international racing governing body commonly known as the FIA, announced a new class of racing for sports cars with engines no greater than 5 litres and that weighed at least 1,760 pounds (798.3 kilograms). The decision was made to allow cars with smaller engines to race in the World Sports Car Championship and to attract new companies to the grid.

Following the frightening speeds attained in the 1967 race, the capacity of engines was limited to 3 liters. The old 5 liter cars were allowed so long as they had a production of 25 vehicles. The regulators thought that no manufacturer would be able to make, let alone sell, 25 prototypes... and yet on the 20th of April 1969 at the Porsche factory there stood the designated number of cars neatly parked. On the 14th of June, three 917 with 4.5 liter flat 12 power were at the start line. Although it was Ford with an 'old' GT 40 that took victory, the Germans took revenge in 1970 and '71.

In this new class of racing, only 25 examples of the car had to be built instead of 50, which lowered the cost of entry and production for other manufacturers. Development was headed by an engineer named Ferdinand Piëch, a member of the Porsche family and the chairman of the Volkswagen Group today.

Stuttgart, 20th of April 1969 : Lined-up at the factory,

 the 25 Porsche 917 awaiting inspection by scrutineers.
But when FIA officials visited Porsche's factory to inspect the cars for the 1969 racing season, they found only six examples of the 917, although engineers said they had the parts to build the rest. The FIA said "no way," and mandated Porsche have all 25 cars completed in order to race.

So in just three weeks, Porsche rushed the remaining cars into construction, using secretaries and office workers to quickly assemble the cars in time. They succeeded in building all 25 of the cars, and they passed FIA inspection -- although some of them barely ran and later had to be reassembled and rebuilt by Porsche mechanics!

Once it started racing, success was not immediate. The car only won one race its first season and was plagued with handling issues. It exhibited wheel spin at 200 miles per hour (321.9 kilometers per hour), and its instability on the track resulted in the death of a driver. Fortunately, John Wyer's Gulf Oil team discovered that adding aluminum sheets to the 917's rear end added some much-needed stability and downforce. Suddenly, the car -- now called the 917K -- became a monster on the racetrack.

I once watched an interview with David Piper where he said that the car's handling was so bad that you needed a compass to find your way out of a corner! The main problem was basically due to a lack of down-force at speed.

Porsche 917 Specifications

917 flat 12 cylinder air cooled engine
Before we look at the Porsche 917's racing record, let's learn a little more about the car itself, its engine, chassis and how it used novel techniques to keep its weight down. 

The 917 was designed to race in a class of cars with smaller engines than the Ford GT40, which dominated the World Sports Car Championship for years with its massive V-8 engine. But don't let the word "smaller" fool you -- the 917's engine had a little less displacement, but it was nothing to fool around with.
An exploded view of the 917 engine

An exploded view of the 917 engine

The car packed a 4.5-liter, air-cooled flat-12-cylinder engine, similar in design to the flat-six or boxer engines used in the Porsche 911 sports car. The 917 engine initially had 520 horsepower, could do the zero to 60 miles per hour (96.6 kilometers per hour) dash in 2.5 seconds and had a top speed of close to 250 miles per hour (402.3 kilometers per hour!)

Can-Am race car engine showing the gearbox and turbos
The engine was capable of far more than that. When Porsche began using the 917 to compete in Can-Am racing, which carried far fewer regulations than other events, the engine was tuned and turbocharged to produce anywhere between 1,000 and 1,500 horsepower. Even today it ranks among the most powerful race cars ever to compete.

Can-Am race car
But an engine is nothing without a body to put it in, and fortunately, the 917 had an impressive one. It featured a lightweight aluminum frame that weighed just over 100 pounds (45.4 kilograms), and included a variety of weight saving measures like a gearshift knob made from balsa wood. The body itself was made of fiberglass.

In addition, the car featured interchangeable rear ends. Teams could choose between the "long tail" with low drag for races with lots of straight sections, or the "short tail" for races with curves when downforce is called for. Other iterations of the car included a combination long/short tail, and open-cockpit "Spyder" versions.

The "Hippie Car" at Classic Le Mans
The "Pink Pig" second from left
at the Porsche museum
The 917 is also famous for coming in a variety of paint schemes, including the famous Gulf Oil colors, as well as a "Pink Pig" version and a psychedelic green-and-purple "Hippie Car" model raced by Martini Racing. Hey, it was the 1970s, after all.

Porsche 917 at the Racetrack

The Porsche 917K of Jo Siffert and
Brian Redman being inspected during
scrutineering at the Le Mans 24 Hours race,
Le Mans, June 1970
Ferdinand Piëch's goal for the Porsche 917 left nothing to the imagination: he wanted it "to be the best. Everywhere". However, while the car was unveiled in 1969, it would be a while before it would achieve greatness.

Helmut Marko and Gijs van Lennep pull into the lead in
their Porsche 917, at Tertre Rouge during the
24 hour race at Le Mans on June 13, 1971.
The car's handling was so sloppy in early races that many drivers refused to pilot it. Porsche asked two BMW drivers for a 1969 race on the Nürburgring, but they refused, saying the car was too dangerous. Later on, a driver named John Woolfe was killed in a 917 at the 24 Hours of Le Mans. The car ended up only winning a single race in 1969.

The 1970 racing season proved to be a better year once the Wyer team ironed out the kinks in the 917's handling. The car went on to claim victories at Daytona, Brands Hatch, Monza, Spa, the Nürburgring, the Targa Florio, Watkins Glen and at the Österreichring in Austria. The season's high point came in June when the 917 won the long-desired overall win at the 24 Hours of Le Mans. The car won nine of 10 races that year to secure the World Championship of Makes trophy.

Footage from the 1970 Le Mans race was used to create the Steve McQueen film "Le Mans," where the 917 featured prominently in the story. The Gulf Oil 917K was driven by McQueen's character Michael Delaney as he battles Ferrari's 512 race cars. 

Click  here to see some background on the making of the movie

The following year was equally successful. The car defended its world trophy in 1971 by winning eight of 10 races and once again won the 24 Hours of Le Mans. This time, it set a record of 240 miles per hour (386.2 kilometers per hour) on the track's Mulsanne straight, a feat that has yet to be broken today.

The 917 became so dominant that the FIA once again changed their regulations, and the car was no longer eligible to compete. So Porsche brought it North America, where they entered it in the Sports Car Club of America's Canadian American Challenge Cup, better known as CanAm. This form of racing had far fewer regulations than the FIA races, so the car was able to compete with well over 1,000 horsepower. As could be expected, it dominated there as well.

Not all the 917's were on display at the Porsche museum. This one 
was at the Classic Le Mans  2012 
Only 65 examples of the Porsche 917 were ever built. Seven exist in the Porsche Museum in Stuttgart, Germany, while many others are in the hands of collectors all over the world. They tend to command high premiums at auctions due to their prestigious histories -- and still inspire awe over their power today.
Porsche Museum in Stuttgart

I hope this short write-up has done this magnificent car justice . . . .


  • Lieberman, Johnny. "Jalopnik Fantasy Garage - Porsche 917." Jalopnik. Aug 21, 2007. (March 25, 2011) Click here to follow the link 
  • Porsche. "40 Years of The Porsche 917." March 9, 2009. (March 25, 2011) Click here to follow the link    
  • Porschebahn Weblog. "1970 Porsche 917LH at the 2010 Amelia Island Concours." April 17, 2010. (March 25, 2011) Click here to follow the link 
  • Read, Dan. "Four decades of cool." March 19, 2009. (March 25, 2011) Click here to follow the link 

Wednesday, 1 January 2014

The history of the Howmet TX turbine car of 1968, still the world's only turbine powered race winner

Howmet TX Gas Turbine Prototype - Le Mans 1968 
Johann and Piet van Biljon
I was fortunate enough to attend the 2012 Classic Le Mans event with my son, Johann. We heard a car driving past the main grandstand that made a very strange sound. Not realising what it was I remarked that it sounded that that car must have a blown turbo! It was making a very loud hissing type noise, but it was still extremely fast. Someone then told us that it is a Howmet TX and that it uses a turbine engine!

I have done some research on the car. This is what I found.


The 1960's was a time when there were fewer restrictions placed on race car designers than today, and that period saw the appearance of gas turbine powered cars, such as Andy Granatelli's STP-Paxton and Lotus 56 cars and the American Howmet Corporation's TX sports-racing machine of 1968. 

The Howmet TX (Turbine eXperimental) was an American sports prototype racing car designed in 1968 to test the competitive use of a gas turbine engine in sports car racing. Planned by racing driver Ray Heppenstall, the TX combined a chassis built by McKee Engineering, turbine engines leased from Continental Aviation & Engineering, and financial backing and materials from the Howmet Corporation.

The Howmet project was conceived early in 1967 by Ray Heppenstall, a sports car racer from Philadelphia. Heppenstall reckoned that a suitable lightweight turbine mounted in the back of a conventional sports-racing chassis would be a competitive proposit ion. He also convinced one of his racing friends, Tom Fleming, then the sales vice-president of Howmet, one of the United States leading metal companies and a major supplier of precision castings to the aircraft gas-turbine industry. Fleming and Heppenstall convinced the Howmet board that running a race-car program would be an ideal promotional tool. 

The turbine engine
A suitable power unit was found at Continental Aviation & Engineering, who had recently lost out in a bid for a US government contract for a light observation helicopter engine and had ten TS325-1 turboshaft engines left on the shelf from its development work. This unit developed a nominal 325 bhp at the output shaft, 650 lbs. ft. of torque at stall, and weighed 170 lbs. Applying the FIA's engine equivalency formula it was rated at 2960 cc, slotting it neatly into the Group 6 sports-prototype three litre class. Continental contributed two of these engines for installation in a relatively conventional tubular space-frame chassis built by Bob McKee.

The turbine was mounted at the rear, above a single speed transmission driving the rear wheels through a specially designed quick-change differential which allowed ratio changes. The necessary reverse was provided by a separate electric motor drive. A 32 gallon fuel tank was mounted centrally between the cockpit and the engine. Suspension was by conventional wishbone and coil spring/shock absorber units, with outboard disc brakes.

The TS325 engine comprised a two-stage gas generating turbine driving the two-stage compressor while also providing gas to the power turbine whose output shaft, via reduction gearing, drove the rear wheels. Heppenstall's solution to the turbine lag was to insert a wastegate bet ween the gas-generating and the power turbines. The first third of throttle pedal movement controlled fuel supply to the combustion chambers, and thus the speed of the engine. But once spinning at its maximum 57,500 rpm and delivering full power, the final two-thirds throttle movement activated the wastegate, thus controlling the amount of gas directed to the power turbine, and hence the rear wheels.

The 1968 Racing Season

The TX's first race was the Daytona 24 hours in February and two cars were brought, a newer car with 2.25 inch longer chassis and the original as spare; drivers were Dick Thompson, Ed Lowther, and Heppenstall. After 34 laps, and running as high as third, the waste-gate valve stayed shut as Lowther arrived at a tight corner leading from the infield to the banking, the resultant contact with the wall putting the car out.

At the Sebring 12 hours the car was qualified third, just 1.2 seconds adrift of the pole. In the race, the TX was running seventh when one of the engine mountings broke, and retired just before the seventh hour.

At the BOAC 500 at Brands Hatch in April British pilot Hugh Dibley joined Thompson and the TX qualified seventh. In the race the wastegate problems struck again, sending Thompson into the bank at Druids after seven laps. Dibley then drove in the Guards Spring Cup at Oulton Park the following weekend. Here he qualified second, and was running in fourth place until he pitted for fuel, but the starter failed and there was no way he could rejoin.

Heppenstall then campaigned the cars in a number of SCCA regional events. The first race finish came in May in the Cumberland 200. Then on June 8th Heppenstall won the qualifier for the Heart of Dixie race at Huntsville, and then the main race the following day, the first race win for a turbine powered car. The following weekend at Marlboro, Dick Thompson joined him for the 4.5 hour 300 mile race. Thompson won the qualifier, then the following day with Heppenstall the feature race also, leading from start to finish. 

The Watkins Glen 6 hours in July was the next FIA Championship outing, and for the first time both TX's were raced, with Thompson/Heppenstall being joined by Hugh Dibley/Bob Tullius in the older car. The cars qualified 8th and 9th, and were running well in third and fourth places, until the final hour. Heppenstall and Thompson maintained third spot until the end, but the transmission of the Dibley/Tullius car broke, although they managed to cross the finish line and be classified 12th.

Howmet TX at Classic Le Mans 2012
The Le Mans 24 hours on 28/29th September turned out to be something of a disaster. After only three laps Thompson came back in to hand over to Heppenstall, feeling that his car wasn't quite right. A fuel system problem limited the engine to 70% power and strangled the speed on the straight. They kept going however, and had worked up to 29th place when, at 9.45pm, Thompson crashed at Indianapolis corner and rolled, severely damaging the car although being unhurt himself. A rear wheel bearing broke on the Tullius/Dibley car after less than two hours. Although repaired in a lengthy 3 hour rebuild, it was finally disqualified in the seventh hour having covered insufficient distance.
Le Mans marked the final race appearance of the unique TX's, Howmet choosing not continue with a race program in 1969. 

Gas turbine operating principle explained

A gas turbine operating principle is simpler than a reciprocating piston engine. There are only three rotating parts not in rubbing contact with their surrounding cases as shown in the above simplified diagram. There are two shafts. The first shaft supports the air compressor and the primary turbine while the second shaft supports the power turbine and transfers the power by gear reduction to the wheels. An electric starter provides assistance by rotating the air compressor for the starting procedure. Compressed air is fed to a combustion chamber where it is mixed with kerosene fuel and ignited. Hot and high pressure gases are generated and sent to the primary turbine before reaching the power turbine. The primary turbine rotates with the air compressor. Hot gases are then sent to the exhaust system. In the case of the Howmet TX, there are two ways to adjust the power transferred to the wheels. The first method is the conventional approach with a gas turbine and operates with the variation of the fuel quantity injected in the combustion chamber. This conventional method, however, is known for a response time unwanted with racing cars. A second method utilizes a variable vane system on the hot gases admitted to the power turbine. This system also called waste-gate, allows to adjust the quantity of hot gases sent to the power turbine while sending the remaining portion directly to an exhaust pipe. This second method allows to keep the combustion chamber at full power and adjust the power sent to the wheels. The third exhaust pipe at the rear is dedicated to this waste-gate.

The Howmet TX gas turbine rated at an equivalent 3000cc produced nearly 400 hp at 55,000 rpm. The power transfer system contains a gear reduction that set the proper rotation to the wheels. 
Reproduced from Wikipedia and various other sources