Tag Archives: 56

Wedge Evolution – Lotus 61

The 1969 Lotus 61 Formula Ford chassis origins can be traced back through the Lotus 51 Formula Ford, Lotus 31 Formula 3, and to the Lotus 22 Formula Junior designs.

Lotus Ford 61, Brooklands Double Twelve

The main external difference between the broadly cigar shaped Lotus 51 and the 61 is the introduction of the wedge shaped body which was first seen on the Pratt & Whitney turbine powered Lotus 56 Indy Car of 1968.

Lotus Ford 61, Brooklands Double Twelve

The last Lotus 51’s were in fact built concurrently with the first Lotus 61’s under the wedge body the 61’s have a slightly stiffer chassis thanks to additional chassis tubes that optimised the triangulation of the structure.

Lotus Ford 61, Brooklands Double Twelve

Further differences between the 51 and 61 models can be seen in the mounting of the steering rack, easier to adjust on the 61, and the brake master cylinder resevoirs, integral on the 51 and remote on the 61 which was not always considered an advantage when they needed topping up on the latter.

Lotus Ford 61, Prescott

Above Les Buck is seen at Prescott Hillclimb competing in the Pre 1972 Classic Racing car class.

Australian Dave Walker and Brit Ian Ashley drove for the works Lotus Formula Ford team in 1969, Walker won the British Formula Ford Championship and came third in the European Formula Ford Championship.

Lotus Ford 61, Brooklands Double Twelve

There were three variants of the Lotus 61 with M and MX featuring aerodynamic updates to improve the efficiency of the cooling system, the MX nose finished up with a lower nose than the original and no engine cover was supplied as most customers had found their cars were quicker without them.

Lotus Ford 61, Brooklands Double Twelve

Despite Dave Walkers championship success and sales of 248 Lotus 61’s this would prove to be the last but one Lotus model built for Formula Ford a class that would be come dominated by a new breed specialist Formula Ford suppliers.

Thanks for joining me on this “Wedge Evolution” edition of “Gettin’ a li’l psycho on tyres”, I hope you will join me for a Concours d’Elegance edition tomorrow. Don’t forget to come back now !

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Son of Silent Sam – Lotus 56

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.

Lotus 56, Goodwood, FoS

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

The Lotus 56Lotus 56, Goodwood, FoS

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.

Lotus 56, Goodwood, FoS

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.

Lotus 56, Goodwood, FoS

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

Lotus 56, Goodwood, FoS

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.

Lotus 56, Goodwood, FoS

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 !

Lotus 56, Goodwood, FoS

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.

Lotus 56, Goodwood, FoS

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 !

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