The 1968 Lotus 56 picked up on the technology used by the STP-Paxton Turbocar “Silent Sam designed by Ken Wallis for the 1967 Indy 500 with which Parnelli Jones came within 8 miles of winning before a transmission bearing failure intervened.

Like the STP Paxton Turbocar the Lotus 56, was also bankrolled by STP’s Andy Granatelli, used four wheel drive transmission.

The Lotus 56

However the Lotus 56 rather than mounting the engine alongside the driver on a backbone chassis as had been the case with the STP Paxton Turbocar, Maurice Phillipe’s design had the motor conventionally mounted behind the driver in what was to become an influential wedge shaped vehicle.

Jim Clark was originally penciled in to drive the Lotus 56 but his death during a race in Germany in April ’68 meant British driver Mike Spence was called in to do the early testing of the Lotus 56, unfortunately Mike was killed during practice three weeks before the start of the Indy 500 after hitting the wall in turn one.

After an accident with in older STP Paxton Turbo car Joe Leonard joined Graham Hill and Art Pollard in the remaining Lotus 56’s.

Despite running with an air restrictor plate mandated for 1968 Joe managed to qualify on pole for the ‘500’ thanks in part to the efficient aerodynamics and superior 4wd handling.

The big advantage of using a Pratt & Whitney Canada PT6 turbo shaft motor, more familiarly seen in a variety of fixed wing and rotary wing aircraft, was reliability these motors are known to have a mean time between outages (MTBO) of 9000 hours !

The disadvantage of turbo shaft motor was eye watering fuel consumption which means turbine powered cars carry more weight and have to re fuel more often than cars powered by conventional piston motor’s.

In the 1968 500 Graham Hill had an accident Art Pollard broke down while Joe Leonard was leading with a few laps to go when a fuel pump shaft failed meaning Granatelli came close but failed to win a cigar for the second year running.

Turbo shaft motors and four wheel drive were outlawed from the Champ Car circuit from 1969. The Lotus 56 design, in 56B specification, was subsequently sporadically used in Grand Prix races during 1971, but apart from phenomenal performance in the wet no overall advantage was found by using the combination of four wheel drive and turbine shaft propelled vehicles.

Thanks for joining me on this ‘Son of Silent Sam’ edition of ‘Gettin’ a lil psycho on tyres’, I hope you will join me again tomorrow. Don’t forget to come back now !