Lotus Elan

Lotus Elan is the name of two separate ranges of automobiles produced by Lotus Cars. The first series of cars was produced between 1962 and 1975 as a rear-wheel drive vehicle. The second series was produced between 1989 and 1995 as a front-wheel drive vehicle.

Timeline

The first range of cars comprised:

Two seater sports cars:
* Lotus Type 26 drop head coupé marketed as the Elan 1500, Elan 1600, and Elan S2.
* Lotus Type 36 fixed head coupé marketed as the Elan S3, the Elan S4 and, lastly, in a higher performance model, the Elan Sprint.
* Lotus Type 45 drop head coupé, replacing the Type 26, delivered in parallel with the Type 36 in S3, S4 and Sprint form.
* Lotus Type 26R racing version of the Type 26.
Four seater sports car :
* Lotus Type 50, fixed head coupé, marketed as the Elan +2.

After the S2 was released the original Elan 1500 and Elan 1600 models were typically referred to as the S1 although the car was never explicitly marketed as such. Today, all models are often cited collectively as the 1960s Elans.
The second range of cars comprised:

Two seater sports cars:
* Lotus Type M100 drop head coupé, initially marketed as the Elan S1 and, later, for the UK market, the Elan S2.

This second model was also produced in South Korea by Kia Motors between 1996 and 1999, rebadged as the Kia Elan.

Lotus Elan 1500, 1600, S2, S1, S3, S4, Sprint

Overview

The Lotus Elan was the first Lotus road car to use a steel backbone chassis with a fibreglass body. This style of construction was to be repeated in subsequent Lotus models for nearly three decades. At approximately, the Elan embodied Colin Chapman's minimum weight design philosophy. The Elan was technologically advanced with a DOHC 1,558 cc engine, four-wheel disc brakes, rack and pinion steering, and 4-wheel independent suspension. Gordon Murray, designer of the McLaren F1 supercar, reportedly said that his only disappointment with the McLaren F1 was that he could not give it the perfect steering of the Lotus Elan.
In 2004, Sports Car International named the Elan number six on the list of Top Sports Cars of the 1960s. The original version of the car was designed by Ron Hickman who also designed the first Lotus Europa as part of Lotus' GT40 project bid and made his fortune having designed the Black & Decker Workmate.
Because of its successful design and rigorous attention to cost control on the body, chassis, engine and transmission, the Elan became Lotus' first commercial success and contributed to the funding of its achievements in racing over the next ten years. It revived a company stretched thin by the more exotic, expensive to build, and rather unreliable Lotus Elite, which used a fibreglass monocoque body/chassis and all aluminium Coventry Climax engine.
The original Elan 1500 was introduced in 1962 as a roadster. After a very short production run of just 22 cars the engine was enlarged and the car was re-designated the Elan 1600. An optional hardtop was also offered. The Elan 1600 of 1963 was replaced by the Elan S2 in 1964. In 1965 the Type 36, a fixed head coupé version of the car, was introduced while in 1966 the drop head coupé Type 26 was replaced by the Type 45. Both Types, 36 and 45, were offered initially in S3 form, followed in 1968 in S4 form, and finally in 1970 as the Elan Sprint. Production of the Sprint ceased in 1973. The standard S2, S3 and S4 models were also available in a slightly more powerful and luxurious "Special Equipment" variant, generally referred to as the SE.
In the UK the Elan was offered as a fully assembled vehicle and, for tax avoidance purposes, as a lower cost kit for final assembly by the customer.

Production

The total production number for the Lotus Elan is not definitively known; however John Bolster, in his book "The Lotus Elan and Europa: A Collector's Guide", provides a number of 12,224. This number was occasionally used by Lotus itself. See below for +2 production.
Meanwhile, Paul Robinshaw and Christopher Ross, in their book "The Original 1962–1973 Lotus Elan", assert that Lotus' somewhat erratic record keeping at the time meant that vehicle serial numbers were not entirely sequential or consistent. Their assessment suggests the actual count to be in the range 8,676-9,153.
As of April 2018, the voluntary, and thus inevitably incomplete, Lotus Elan registry lists approximately 1,100 known remaining vehicles in over 30 countries.

Construction

The basic structure of the Lotus Elan comprised a fabricated mild steel backbone chassis, similar to a double ended tuning fork, and a fibreglass body. The chassis was the primary stressed component, providing the necessary bending and torsional rigidity. It is readily changeable and most Elans on the road today have had a new chassis fitted at some point, because of either accident or decay.
The fibreglass body was solidly bolted to the chassis at 16 points, fitting over the backbone like a saddle. While not highly stressed the body nevertheless added to the overall rigidity of the structure.
The engine and gearbox are located between the front fork arms and the differential between the rear fork arms. The front and rear suspensions attach to the ends of their respective arms: turrets at the end of the arms hold the suspension springs and dampers.
This design resulted in light weight, high rigidity and easy access through wide door openings with low sills. Driver and passenger protection from front and rear impact was acceptable for its time, but side impact protection was minimal.

Drive train

The engine, gearbox and differential were all sourced from Ford UK components. See below for details on the engine. The gearbox was a high volume unit used widely across the Ford range. Lotus offered regular and close ratio versions. The differential unit was also sourced from Ford but converted for independent rear suspension use. Three differential ratios were offered at various times during the production life of the vehicle: 3.55, 3.77 and 3.9. Most Elans were fitted with 3.77 differentials. 3.9 differentials provided the best acceleration and were often favoured by purchasers of early cars. 3.55 differentials became more common in later cars to provide more relaxed cruising on newly built highways.
The final drive used four Rotoflex couplings to connect the differential output shafts to the rear hubs. These "rubber doughnut" couplings were widely used at the time for road vehicles and racing, prior to the availability of constant velocity joints. In the case of the Elan, which had exceptionally supple rear suspension that allowed significant vertical wheel travel, the deformation of the Rotoflexes in operation resulted in some "wind up" of the couplings. This could be readily detected by the driver, especially at takeoff and during gear changes, and was slightly disconcerting when driving an Elan for the first time. In practice drivers typically adjusted their clutch technique within a few minutes and no longer noticed it. In recent years the uncertain quality of replacement Rotoflex couplings, combined with the availability of half-shafts built with CV joints, has resulted in many Elans being converted from Rotoflex to CV joint drive.
A notable feature of the drive train design was its use of standard mass-produced components in combination with a minimal number of specialised aluminium castings to create a power unit and transmission suitable for a high performance sports car:

The engine cylinder head and timing chest. Converted the Ford Kent pushrod engine into a twin overhead cam engine.
The differential rear cover and carrier. Converted a live axle to independent suspension operation.
The rear wheel hubs. Required for the Chapman Strut rear suspension.

These three items were unique to the Elan.

Engine

The 1,558 cc "Lotus TwinCam" engine was based on the Ford Kent Pre-Crossflow four-cylinder 1,498 cc engine, with a two-valve alloy chain-driven twin-cam head designed by Harry Mundy. The rights to this design were later purchased by Ford, which renamed it the "Lotus-Ford Twin Cam". It was later used in a number of Ford and Lotus production and racing models.
Lotus reported different power outputs for the Twin Cam engine during the production of the Elan. Before the release of the Sprint the following outputs were reported in the Workshop Manual:

Model	Power	rpm
Std		5,500
SE		6,000

Lotus marketing material from the S3 period quoted the SE variant at, noting high lift cams, carburettor re-jetting and a four branch exhaust.
The final version of the Workshop Manual revised these numbers, as shown in the following tables. The increased power of the Sprint engine was primarily due to slightly larger inlet valves, so it was named the Big Valve engine :

Model	Power	rpm
Std		5,500
SE		6,000
Sprint		6,500
Sprint Emission		6,500

Model	Torque	rpm
except Sprint		4,000
Sprint		5,500
Sprint Emission		5,000

Suspension, steering, braking

The Elan used modern technologies for its suspension, steering and brakes. The overall design was simple and easily maintained. In common with many Lotus cars they were perhaps the Elan's most highly regarded features.

Front suspension: The front suspension was based on Triumph wheel uprights and steering components while the remaining pieces were of Lotus design. The layout was a classic double wishbone arrangement with coilover springs and shock absorbers. Each "wishbone" consisted of two separate arms, with the upper pair connected to a ball joint at the top of the suspension upright and the bottom pair connected to a trunnion joint at the base of the upright. The bottom pair also held the base of the shock absorber and coil spring assembly; the top was connected to its chassis suspension tower. Similarly, the steering was of classic rack and pinion design; the Triumph rack was modified for the Elan's narrow track with custom track rods and rack collars that set the minimum turning radius. The steering, 2 turns lock-to-lock, was not power assisted, which allowed for the visceral steering feel for which the Elan was famous.
Rear suspension: The Chapman Strut rear suspension was designed and manufactured by Lotus. A single brazed "A frame" wishbone was bolted to each side of the base of a cast aluminium upright/wheel-hub, and to the chassis at two widely set points. The shock absorber and coil spring strut was integrated into the upright and bolted via a rubber "Lotocone" coupling to its chassis suspension tower. This resulted in a simple design with just three chassis connection points.
Brakes: The disc brakes, front and rear, were supplied by Girling. Most Elans used a single hydraulic circuit although Federal cars were fitted with dual circuits. Early Elan brake systems were not servo assisted, but servos were fitted to SE and later models. In practice the Elan was light enough that power assistance for the brakes was not required, so the servo may have assisted marketing more than braking.