The Sinclair C5 is a small one-person battery electric recumbent tricycle, technically an "electrically assisted pedal cycle". It was the culmination of the English entrepreneur Clive Sinclair's long-running interest in electric vehicles. Although widely described as an "electric car", Sinclair characterised it as a "vehicle, not a car". and a "notorious ... example of failure". The C5 went on to become a cult item for collectors. Thousands of unsold C5s were purchased by investors and sold for hugely inflated prices, as much as £6,000 compared to the original retail value of £399. Enthusiasts have established owners' clubs and some have modified their vehicles substantially, adding bigger wheels, jet engines, and high-powered electric motors to propel their C5s at speeds of up to .

Design

right|thumb|C5 with the left side of the body shell removed, showing the pedals, chassis, drive chain, battery, and electric motor

right|thumb|C5 seen from the rear, showing the driver's cockpit and the open luggage compartment at the rear

The C5 is made predominantly of polypropylene, measuring long, wide, and high. It weighs approximately without a battery and with one. As the C5 does not have a reverse gear, reversing direction is done by getting out, picking up the front end and turning it around by hand.

The C5 is powered by a 12-volt lead–acid electric battery driving a motor with a continuous rating of 250 watts and a maximum 4,100 revolutions per minute. It is coupled with a two-stage gear-drive that increases torque by a factor of 13, without which the motor would not be able to move the vehicle when a person is on board. However, the motor is vulnerable to overheating. The torque increases as the load on the vehicle increases, for instance by going up too steep a gradient. As the speed of the motor reduces, the current flow through its windings increases, drawing up to 140 amps at stall speed. This would very quickly burn the motor out if sustained, so the motor's load is constantly monitored by the C5's electronics. If it stalls under full load the electronics disable the motor after 4 seconds, while if it is under heavy load (around 80 or 90 amps) it trips after two or three minutes. A heat-sensitive resistor inside the motor warns the driver if the vehicle is beginning to overheat and disconnects the motor after a short time, and a third line of defence is provided by a metallic strip mounted on the motor. If an excessive temperature is reached the strip distorts and the power is disconnected.

Although it was usually billed as an electric vehicle, the C5 also depends significantly on pedal power. The vehicle's battery is designed to provide 35 amps for an hour when fully charged or half that for two hours, giving the C5 a claimed range of .

The C5 was initially sold at a cost of £399, but to keep the cost under the £400 mark a number of components were sold as optional accessories. These included indicator lights, mirrors, mud flaps, a horn, and a "High-Vis Mast" consisting of a reflective strip on a pole, designed to make the C5 more visible in traffic. Sinclair's C5 accessories brochure noted that "the British climate isn't always ideal for wind-in-the-hair driving" and offered a range of waterproofs to keep C5 drivers dry in the vehicle's open cockpit. Other accessories included seat cushions and spare batteries.

History

Origins

Sir Clive Sinclair's interest in the possibilities of electric vehicles originated in the late 1950s during a holiday job for the electronics company Solartron. Fifteen years later, in the early 1970s, he was the head of his own successful electronics company, Sinclair Radionics, based in St Ives in Cambridgeshire. He tasked one of his employees, Chris Curry – later a co-founder of Acorn Computers – to carry out some preliminary research into electric vehicle design.

Early development: the C1

It was not until late 1979 that Sinclair returned to electric vehicle development. Around Christmas that year, he approached Tony Wood Rogers, an ex-Radionics employee, to carry out consultancy work on "a preliminary investigation into a personal electric vehicle". The vehicle was dubbed the C1 (the C standing for Clive). He built a number of prototypes to demonstrate various design principles and clarify the final specifications.

A specification of the C1 emerged by the end of the year. It would address short-distance transportation needs, with a minimum range of on a fully charged battery. This reflected official figures showing that the average daily car journey was only , while the average moped or pedal cycle journey was just . The users were envisaged as being housewives, urban commuters, and young people, who might otherwise use cycles or mopeds to travel. The electric vehicle would be safer, more weather-proof, and would offer space to carry items. It would be easy to drive and park and for the driver to enter or exit, and it would require minimum maintenance. The vehicle would be engineered for simplicity using injection-moulded plastic components and a polypropylene body. It would also be much cheaper than a car, costing £500 () at the most.

One area of development that Sinclair purposely avoided was battery technology. Electric vehicles powered by lead–acid batteries had once actually outnumbered internal combustion engine vehicles; in 1912 nearly 34,000 electric cars were registered in the U.S. However, the efficiency of internal combustion engines greatly improved while battery technology advanced much more slowly, leading to petrol and diesel-driven vehicles dominating the market. By 1978, out of 17.6 million registered vehicles on Britain's roads, only 45,000 were electric vehicles in day-to-day use and of those, 90% were milkfloats. Sinclair chose to rely on existing lead–acid battery technology, avoiding the great expense of developing a more efficient type. His rationale was that if the electric vehicle market took off, battery manufacturers would step up to develop better batteries. Wood Rogers recalls:

The Consumers' Association published a critical report on the C5 in the June issue of its magazine Which?, concluding that the vehicle was of only limited use and represented poor value for money. All three of the C5s that it tested broke down with a "major gearbox fault" and their High-Vis Masts snapped. The longest run between battery charges was only , and a more realistic achievable range was . It also echoed the AA's concerns about the C5's safety and the omission of the High-Vis Mast from the standard package. The magazine also called the C5 "too easy to steal", hardly surprising considering that while a security lock could be used to prevent it being driven away, the C5 was light enough that a would-be thief could simply pick it up and carry it off.

As the summer of 1985 continued, sales of the C5 remained far below Sinclair's predictions; only 8,000 had been sold by July. In the middle of that month, the Advertising Standards Authority ordered Sinclair to amend or withdraw its advertisements for the C5 after finding that the company's claims about the safety and speed of the C5 either could not be proved or were not justified. Retailers attempted to deal with unsold stocks of C5s by drastically cutting the vehicle's price. Comet first reduced the price to £259.90 but by the end of the year was selling C5s with a complete set of accessories for only £139.99, 65% less than the initial price.

Production was terminated in August 1985, by which time 14,000 C5s had been assembled. Cashflow problems caused by the paucity of sales caused relations to break down between Sinclair Vehicles and Hoover. In June 1985, Hoover obtained a writ against Sinclair for unpaid debts of over £1.5 million, relating to work carried out over the previous eight months. It did not actually serve the writ but entered negotiations with Sinclair. In mid-August, it publicly announced that it was ceasing production of the C5.

On 5 November, TPD was formally liquidated at a creditors' meeting. It was revealed, to the anger of the creditors, that Sinclair had taken out a £5 million debenture to cover the money that he had put into the company. Ordinary creditors faced little prospect of recovering the £1 million left outstanding. Primary Contact, the marketing agency used by Sinclair to promote the C5, was left with the biggest unpaid bill, of nearly £500,000.

Some commentators attributed the C5's failure to problems with Sinclair's marketing strategy; only a year after the demise of Sinclair Vehicles, the Globe and Mail newspaper called it "one of the great marketing bombs of postwar British industry". He comments that the experience of working on the C5 convinced him of the need for industrial designers such as himself to get "involved early in the innovation process, shaping basic configurations, never again [being] satisfied to simply decorate a fundamentally bad idea".

Legacy

Sinclair's other electric vehicles

Sinclair envisaged producing follow-up vehicles such as the C10, a two-seater city car, and the C15, a three-seater capable of travelling at . As Wills put it at the launch event, "We're developing a family of traffic-compatible, quiet, economic and pollution-free vehicles for the end of the '80s." The C5 was described as "the baby of the family".

At the time of the C5's launch, Sinclair described the C15 as having "a futuristic design with an elongated 'tear-drop' shape, a lightweight body made of self-coloured polypropylene and a single, possibly 'roller' type rear wheel". However, it could only have worked if sodium sulphur batteries had realised their promise. In the event they did not, the project could not continue, due to thermal problems.

In 2017 Sir Clive's nephew Grant Sinclair presented what he called an updated version of the Sinclair C5 called the Iris eTrike.

Cult following

right|thumb|C5 enthusiasts gather at the [[Brooklands Museum in Surrey]]

right|thumb|A heavily modified C5 fitted with a [[jet engine]]

The C5 gained an unexpected cult following. reselling them for considerably more than their original retail price. One such investor, Adam Harper, bought 600 C5s from a film company as a speculative investment in 1987. He sold all but four within two years, selling them to customers who wanted a novel or more environmentally friendly form of transportation. He also found willing customers among drivers who had been banned from the road, as the C5 did not need a driving licence or vehicle tax. By 1996, a Special Edition C5 in its original box was reported to be worth more than £5,000 to collectors.

C5 owners began modifying their vehicles to achieve levels of performance far beyond anything envisaged by Sinclair. Adam Harper used one C5 as a stunt vehicle, driving it through a tunnel of fire,

As quoted in the 1987 Guinness Book of Records under battery powered vehicle: "John W. Owen and Roy Harvey travelled 919 miles (1479 km) from John O'Groats to Land's End in a Sinclair C5 in 103 hr 15 min on 30 Apr-4 May 1985" ( average).

Chris Crosskey, an engineer from Abingdon, set a record for the longest journey completed on a C5 on a trip to Glastonbury – away ("I nearly died of exhaustion") – and tried three times to drive one from Land's End to John o' Groats, a distance of . while plumber and inventor Colin Furze turned one into a "monster trike" with wheels and a petrol engine capable of propelling it at .

The singer John Otway has used a C5 in his stage show and publicity.

See also

  • eROCKIT
  • List of motorized trikes
  • Velomobile

References

  • "Sir Clive Sinclair on the C5" – BBC News report from the January 1985 launch of the C5
  • "Sinclair C5 electric car 'ahead of its time'" – BBC News report from January 1985 showing reporter Elfyn Thomas driving a C5 in Cardiff city centre