Reviewed by Unique Cars and Parts
Our Rating: 5
Age of the Monocoque
Formula One racing's "Age of the Monocoque" can be said to have dawned on May 20, 1962
, in the Dutch Grand Prix at Zandvoort
. On that day Jim Clark
started his brand-new Lotus 25 from third-fastest place on the grid, led the entire field going away for 12 laps, and then slowed as he struck clutch trouble. After a pit stop Clark finished 10th, but Colin Chapman's
then new monocoque-chassised car had set the GP world thinking. When it won the Belgian, British and United States GPs in the rest of the season, and ran Graham Hill's BRM
very close for the World Championship titles, the monocoque was here to stay.
Not that Colin Chapman's
brainchild was the first stressed-skin chassised competition car. Far from it. Nearly a century ago the 1915 Indianapolis Cornelian had a monocoque hull. In 1923 the mono-construction Voisins ran in the French GP, and a host of good-looking but unsung specials espoused the aviation principles which Chapman eventually employed so brilliantly. As with so many of his "innovations" Colin didn't know of any precedent; he simply saw a problem, recognised a solution, and decided to experiment to see if it would work.
Early Development of the Lotus Elan
The Lotus 25 story began, curiously enough, in early development tests for the Elan roadster
engineers were testing the rigidity of a backbone chassis, and found it to be enormously strong - particularly in comparison to its modest weight. Colin Chapman
would later recall; "I began to think about applying this backbone idea to a racing car. Strangely enough I really did draw out the original scheme on the back of a table napkin. I thought 'Why not space the sides of the backbone far enough apart to sit a driver between them?'
"...We'd had awful trouble for years with aluminium fuel tanks wrapped around tube chassis frames, and they were always cracking and having holes rubbed in them. So if we used double-skin walls to this backbone affair we could put rubber bags inside there and so contain our fuel more reliably. So we drew-up the 25 - so far as I knew the first ever monocoque racing car. We didn't know if it would work, so then we drew the 24 spaceframe car to pick-up the 25 suspension
. The spaceframe was a known quantity and so we sold it to our customers. We couldn't expect to sell them a revolutionary car which might not work at all and which might need a long and expensive development programme. At that time the monocoque - if that's what you want to call it - really was an unknown animal ..."
The way in which Colin Chapman rationalised his customer approach was typically convincing, but at Zandvoort
on the day the 25 was unveiled most of his customers for the spaceframe 24 were distinctly sick! Colin laid out the car with draughtsman Alan Styman and the usual conclave of Lotus engineers and mechanics all kicking around practical suggestions. Dick Scammell recalled "None of us really knew what we were doing but it all took shape nicely and certainly looked right. Mike Costin was in there wielding a rivetter because he had experience of the aircraft industry and so we all thought he must know what he's doing! ... It was that kind of project,"
Chapman recalled the original 25 R1 as "the cleanest and nicest looking car we'd ever made. There were no holes in the bodywork, the engine and gearbox were beautifully cowled-in - it looked supreme ..." The bathtub type hull of the new car was formed by two parallel box members fabricated from 16-gauge L72 AlClad aluminium sheet. These torsion boxes were cross-connected by steel bulkheads and fabricated cross-members, as well as by the rigidly-mounted Coventry-Climax V8 engine in the tail. Its 90-degree Vee formation demanded that the monocoque torsion boxes on either side of the engine bay were reduced in height to allow the heads to clear them, and so steel chassis horns were made up to add rigidity in this area.
The Lotus 21 Formula Junior
was classically Lotus F1 practise, with inboard front coil-dampers operated by bell-crank upper arms as on the 21 and 24 spaceframes. A 2F five-speed 5DS10 transaxle was used, and with the driver's seat laid back at around 35-degrees, a tiny "kiddy car" steering
wheel and every non-essential outboard component hidden away inboard the Lotus 25 offered a mere eight square feet frontal area - an 11 percent improvement on the 1960
Lotus 18s. While the Lotus 21 - the Formula Junior-based 1961
F1 car - had a torsional stiffness measured at 700ft/lb per degree, its space-frame weighed around 82lbs bare or 130lbs with all necessary brackets and tanks installed.
In comparison, the Lotus 25 monocoque - which was the fuel tank and which included all necessary brackets - scaled just 70lbs. In addition its torsional rigidity was basically 1,000ft/lb per degree, and with the engine mounted it increased enormously to 2,400ft/lb per degree. In other words the new monocoque offered three times the space-frame's rigidity for a trifle more than half its weight! Obviously such a sweeping innovation - or rediscovery - required some development, such as a massive cross-brace being built in between the rearward lower front wishbone mounts to prevent the hull "parting" under heavy braking.
Team Lotus worked quickly, and Jim Clark
drove like a god. In Monaco he lost second place with another clutch failure after breaking the lap record, at Mallory Park his oil pressure vanished and six days later Clark won brilliantly at Spa-Francorchamps
- the circuit he most feared and disliked, but on which he was to win four times. The season continued, with Clark and Graham Hill
locked in combat for the World titles. A second 25 - R2 appeared at Rouen for Clark
to drive in the French GP, while his team-mate Trevor Taylor took over the prototype and had it demolished in the celebrated finish-line collision with Trintignant's 24. It was the first modern monocoque racing car to be destroyed in an accident - and the tub displayed its enormous strength as it allowed Taylor to step out unscathed after bulleting into the other Lotus at an impact speed of around 160 km/h.
In September a new 25 - R3 - made its debut in the non-Championship Oulton Park Gold Cup race, which Jim Clark
won in R2. He drove the later car to victory in America and now had to beat Graham Hill
in South Africa to clinch the World Championships for himself and for Marque Lotus. In between came the non-Championship Mexican GP, which Jim Clark
won sensationally in R2 after his own R3 was disqualified for being push-started. On the way there from Watkins Glen
he drove one of the 25s in exploratory laps of the Indianapolis Speedway, lapping at a consistent 220-225 km/h (142-143mph).
The South African Tour
The South African tour started with the Rand GP at Kyalami, and there Team Lotus placed 1-2 with Jim Clark
in R3 and Taylor in R2 ... the first monocque GP car one-two finish in history. Taylor then won the Natal GP in R2 with Jim Clark
second in an off-song new 25 just flown out from Cheshunt - R4. Yet another new car - R5 - was flown out for the all-important South African GP at East London, and Jim Clark
started from pole position in it, drew out a 30-second lead by half-distance and then lost lubricant as a bolt dropped out of his Climax engine, giving the titles to Hill and BRM
Clark and Taylor placed 1-2 at Pau in R5 and R3, Jim Clark
won at Imola in R5, and again in the same car at Silverstone
. In August the World Champion won the Swedish Karlskoga Kannonloppet in R3 from Taylor in R2, and in September he drove R4 to victory at Oulton Park. His Grande Epreuve victories were all scored in his favourite R4, in Belgium, Holland, France, Britain, Italy, Mexico and South Africa - a seven in one season record. In addition Jim Clark
led at Snetterton, Monaco, Germany and Zeltweg in races which he did not win. This was the incredible season in which he completed at least three races on the same set of Dunlop tyres
Head to Head with Graham Hill and Innes Ireland
Both Clark and Trevor Taylor swapped cars after the Scot's R5 had died on the line in the Aintree 200 and set off after the field a lap late. Charging hard in Trevor's R3 Jim Clark
shattered the lap record, and came home an inspired third behind Graham Hill
and Innes Ireland
. At Monaco Jack Brabham
was loaned R3 when his own team was beset by engine failure, and he finished ninth and last in the first non-works outing for a Lotus 25. In practice at Spa-Francorchamps
Taylor totally destroyed R5 at Stavelot Corner, careening along a wall before hitting and demolishing a wooden observer's hut. The accident was caused by an inboard rear wishbone mounting pulling apart, it was reputedly after a tea-break, and all that was holding the wishbone to the chassis was a mechanic's screwdriver, poked through the hole. Whatever the truth, R5 was shovelled-up, put in a tea-chest and taken home as scrap.
Then at Enna for the Mediterranean GP, Trevor Taylor was showered with stones by Bandini's drifting BRM
, and lost control of R2. She tore onto the verge on the pits turn at around 220 km/h cannoned off the bank and literally flew back across the track in front of a horrified Peter Arundell, driving the works' R3. He glimpsed his team-mate hanging half out of the cockpit before R2 smashed itself to pieces against the pit barrier, and somersaulted away down the road, exploding into flames as the Yorkshireman was flung out and sent flurrying over and over along the track! Amazingly he came round within moments, bruised and shaken but with nothing broken. The pit-barrier saved a massacre, but one mechanic couldn't move or speak for long minutes - just staring dumbly at a signal board he had been holding. There were two sides to Team Lotus' most successful year ever!
The 1964 Season
Two 25s, R3 and R7 which had appeared new in South Africa at the close of '63, were sold to Tim Parnell's team for this season, being fitted with BRM
V8 engines and Hewland gearboxes and sprayed dark blue with maroon bands round the nose intake, Dunlop introduced their new generation of wide-tread tyres, and in deference the 25s were progressively modified, with brand-new suspension uprights and hub carriers, smaller brake discs to fit within the new 13-inch instead of 15-inch wheel diameters, altered suspension and steering geometry. As the '25B' - a classification to which Chapman objected - the monocoque cars kept winning, but with nothing like their dominant regularity of 1963
Jimmy used R6 to win at Goodwood, and the Grands Prix of Holland, Belgium and Britain. He won at Spa without knowing it after everybody ahead of him ran out of fuel and his Lotus 25B died as well on the slowing-down lap! Old Faithful R6 - the term might as well have been applied to R4 which followed its sisters into Parnell's team - also led the Silverstone, Monaco, French, Mediterranean and United States races before being sidelined by mechanical trouble.
Meanwhile, a new mode! had appeared, purpose-built for the new generation of 13-inch wheels and tyres. This was the Lotus 33, visually almost identical to the 25s but with sweeping suspension geometry changes, a wheelbase increase of some %-inch, heavier-duty half-shafts, solid steering arms and extra rivets in joints found suspect in the original hulls. Jimmy drove the new car, R8, first time out in the Aintree 200 and was leading before Jack Brabham shouldered by. Down into the daunting ESS-bend at Melling Crossing, a back marker moved aside to let Jack by, then moved onto line without noticing Clark in his mirrors. Jimmy went onto the grass, lost control and virtually wrote-off R8's left-side and front end against straw bales defending an old boiler house.
The car was rebuilt as a spare in time for Spa, but was never to show any improvement over the well-proven 25Bs, Clark won with it in the Solitude GP, and it was then turned over to his new team-mate Mike Spence (deputising for the gravely injured Pete Arundel I who had crashed in an F2 race at Reims) while another 33, R9, was completed for the Scot. Jimmy led the German and Mexican GPs in this car, losing an excellent chance of retaining his title on the very last lap at Mexico City when R9's engine ran out of oil and seized after leading all the way . . .
For Parnell, Mike Hailwood
dropped R7 into the lake at Enna, wading hurriedly out of its snake-infested waters, and while it was being dried and straightened-out Team Lotus' R4 joined the team whose much-damaged, much repaired R3 was virtually disintegrating from overuse, rivets fidgeting, ball-joints rattling and the car generally in need of an extensive rebuild. Meanwhile, Team Lotus completed another 33, R10, in time for the Rand GP in December, and with Clark in bed after slipping a disc the car gave Jackie Stewart his F1 race debut. After breaking a drive shaft on the grid for heat one he won heat two going away.
The 1965 Season
Team Lotus entered their monocoque cars in nine of the ten Championships rounds (having taken time" off from Monaco to win the Indy '500' with a Mark 38) and Jim Clark won six of them. They contested five out of six non-Championship races, and won three; and all eight Tasman Championship rounds and won five and the title with a 2.5-litre Climax FPF engine shoe-horned into a tube bay at the rear of a modified Lotus 32 F2 tub. Jim Clark
took his second Drivers' Championship, Lotus the Constructors' title and the Indy dollars and Tasman triumph were just the icing on the cake.
The Race of Champions
During the year Jim Clark
drove his new 33 - R10 - to win the South African GP, and the first heat of the Race of Champions at Brands Hatch. Under pressure from Dan Gurney in Heat Two he had an uncharacteristic shunt, totalling R10 beyond all doubt but again walking away unhurt. Mike Spence won the race on aggregate in R9. Another 33 - R11 - was hastily completed for Clark's use and he won first time out in it, at Syracuse, while at Goodwood Jimmy probably drove old R6 to win with the new 32-valve Climax engine installed. He subsequently fell back on 'Old Faithful' to win the French GP, and place second at Enna, while R 11 brought victory at Spa - yet again - and in the British and German GPs. R9 was used to win in Holland, and R11 failed as Jimmy's regular mount in the late-season events - after he had clinched his World Championship titles.
Meanwhile the privateers were having plenty of action. Old R8 whose monocoque had never been satisfactory, took Paul Hawkins into the harbor at Monaco (having been entered by its new owner, Dickie Stoop), and Parnell had chosen to rebuild R4 to almost new condition, Dick Attwood spun it into a telegraph pole in the rain at Spa, and almost cut it in two. It was written-off, although Attwood thankfully escaped serious injury. Mike Spence settled R9 upside down amidst "Hailwood's reeds" at Enna in mid-season. "R4" reappeared in the non-Championship Rand GP in December, which was run to the forthcoming 3-litre regulations which were not to take effect officially until January 1, 1966. Jo Bonnier
appeared with Old Faithful R6, her Team Lotus lettering simply taped over, while Ireland drove ParnelTs "R4" whatever its true identity and R3 appeared with a 2.7 Climax engine for Hawkins, who drove it into third place. It was the end of an era.
THE LOTUS 25 FAMILY
- 25-R1 1st Belgian GP, 1962, driver Jim Clark. W/o Trevor Taylor, French GP, 1962.
- 25-R2 1st British GP, Mexican GP, Oulton Gold Cup, 1962, driver Jim Clark. 1st Natal GP, 1962, driver Trevor Taylor. W/o Trevor Taylor, Mediterranean GP, 1963.
- 25-R3 1st United States GP, Rand GP 1962, and Karlskoga Kannon-loppet, 1963, driver Jim Clark. Sold to Parnell, crashed Mexican GP practice 1966 - subsequent history unknown - possibly chassis owned by Climax engine service company in UK.
- 25-R4 1st Belgian GP, Dutch GP, French GP, British GP, Italian GP, Mexican GP, South African GP, Oulton Park Gold Cup, 1963, driver Jim Clark. Sold to Parnell, W/o Richard Attwood, Belgian GP, 1966.
- 25-R5 1st Pau, Imola, Silverstone International Trophy, 1963, driver Jim Clark. W/o Trevor Taylor, Belgian GP practice, 1963.
- 25-R6 1st Goodwood, Dutch GP, Belgian GP, British GP, 1964; 1st Goodwood, French GP, 1965, driver Jim Clark. Sold to Joakim Bonnier 1966, then to MGM for 'Grand Prix' film. Subsequent history unknown.
- 25-R7 Team Lotus for South African GP 1963. Sold to Parnell 1964, raced by his team into 1967 with BRM V8, then 2.7-litre Climax, 3-litre Climax Godiva V8, 1.6 Cosworth FVA as F2 car, and converted for 3-litre BRM V12 as F1. Restored to 1963 Team Lotus Climax V8 trim in Donington Collection, UK.
- 33-R8 1st Solitude, 1964, driver Jim Clark. Sold to Dickie Stoop for Paul Hawkins in 1965 - to MGM for 'Grand Prix' 1966 - subsequent history unknown.
- 33-R9 1st Dutch GP, 1965, driver Jim Clark. Sold to Joakim Bonnier 1966 - to MGM - subsequent history unknown.
- 33-R10 1st South African GP, 1965, driver Jim Clark. W/o Jim Clark, Brands Hatch Race of Champions, 1965.
- 33-R11 1st Syracuse, Belgian GP, British GP, German GP, 1965, driver Jim Clark. Sold to Earl Chiles 1967 driven by Mike Fisher and Pete Lovely - to Paul Scott 1969 fitted with Olds V8.
- 39-R12 Chassis built for unraced Climax flat-16 11/2-litre engine in 1965 - modified for Tasman Formula 1966. Sold to Leo Geoghegan, fitted 2.5 Repco V8 1967.
- 33-R13 Parnell Special, built 1965 probably rebuilt R4 - Sold to Peter Yock 1967/8 - to Peter Hughes, fitted Daimler V8 1969.
- 33-R14 1st 1967 Tasman Championship, driver Jim Clark. Presented to Leonard Lee of Coventry-Climax on their withdrawal from F1 engine development. Became part of the Donington Collection.