Engineering Timelines: Dr Alex Moulton

Mechanical engineer Dr Alexander Eric ‘Alex’ Moulton is the man behind the revolutionary small-wheeled lightweight Moulton Bicycle, models of which are still in production, more than 50 years after the initial development work. A specialist in the design of suspension systems, he is responsible for the smooth ride associated with a large range of cars built by the British Motor Corporation (later British Leyland), starting with the ever-popular Mini, first released in 1959.

Moulton is described by architect Norman Foster (b.1935, knighted 1990, Baron Foster of Thames Bank 1999) as a “remarkable man” and “brilliant engineer”. His design process linked form and function — inspired by a Japanese tradition that the spirit of the maker is in the artefact — and his ideas that led to prototypes went through a sustained process of testing and improvement. Through his company, Moulton Developments, he developed the innovative Hydrolastic and Hydragas suspension systems. The first of these was in use from 1962 to 1978, and Hydragas from 1980 to 2002.

Moulton’s undergraduate studies at King’s College, Cambridge, had been interrupted by wartime work on RAF aircraft engines at the Bristol Aeroplane Company, later assisting chief engineer Sir Roy Fedden (1885-1973). Research suited Moulton. He was driven by a desire to understand the fundamentals of a problem before tackling it, trying a solution and then checking the results. He liked to explain and share his conclusions.

The Moulton family’s engineering heritage goes back to his great-grandfather Stephen Moulton (1794-1880), an early fabricator in Britain of vulcanised rubber products, working from Bradford-on-Avon. George Spencer Moulton & Co (Spencer Moulton), the company that resulted from a later merger (1891) with a London firm, was a major supplier to railway and vehicle manufacturers for 65 years.

Moulton joined the company in 1945, where he was able to research rubber technologies and find new uses for rubber in place of metal, notably in spring suspension systems. Rubber maintains its volume under load deformation and regains its original shape when unloaded. At the time, its properties in compression were well understood but its behaviour under shear and bending was relatively untested.

In 1948 Moulton invented the Flexitor suspension unit — a torsional shear spring with an inner tubular steel shaft and outer rubber shell, loaded by the relative angular rotation of the two. It’s an improvement on the generally-used Torsilastic tubular rubber spring [pioneered by Alvin S. Krotz (1893-1970) in the USA]. Flexitor is easier to attach to a chassis and its shell is a single piece.

In the 1950s, Moulton developed the cone suspension unit that was used in Minis from 1959 until 2000 — a truncated cone (frusto-conical) rubber spring and shock absorber, consisting of a cup-shaped body of rubber bonded between steel plates and attached to a metal arm ending in a ball joint. The ball joint slots into a socket on the wheel strut and, as he noted, “resembles the typical anatomy of a muscle-actuated limb”.

Hydrolastic suspension is a refinement of the cone system. It used hydraulic fluid damping and linked a vehicle’s wheels into one system, greatly reducing vehicle pitching. Cars manufactured by the British Motor Corporation (later British Leyland) featured Hydrolastic suspension. After 1967, Moulton Developments worked on the Hydragassystem, with a pressurised cushion of gas at each wheel and hydraulic fluid interconnection.

In the late 1950s, Moulton started to think about bicycle design, determined to improve ride efficiency and comfort. He interrogated every component of the traditional bike, establishing the essential requirements. The result was the Moulton Bicycle, with its distinctive small diameter wheels, lightweight frame and rubber spring suspension. The Mark 1 prototype (F-Frame) was completed in early 1959, with a revised version (‘lazy F’) going into production for launch in November 1962. It was an instant success, and by the end of 1963, Moulton had become the second-largest bike frame manufacturer in Britain.

The Moulton bike’s high performance and distinctive design have made it popular with cyclists worldwide. Notable models (using the later AM space frame) include the record-breaking AM7 Speed (1983), the AM-ATB (all terrain bike, 1988), and the APB (all purpose bike, 1992). In 1998, the New series was released, using Flexitor suspension on the front wheels and Hydrolastic on the rear. The Moulton Bicycle Company (formed 2008) continues to operate from Bradford-on-Avon. Present-day fans include inventor James Dyson (b.1947, knighted 2007).

Alex Moulton was granted more than 250 patents in his lifetime, 90 percent of them as sole author and 58 percent of them in Britain. His most prolific decades were the 1950s and 60s, covering at least 148 patents. He always devised names for his inventions as he thought that a distinctive word describing their purpose would be memorable.

There was scarcely any boundary between Moulton’s life and work. He never married, and he was able to pursue ideas to his own timetable. However, he was keen on outdoor activities: hiking and kayaking into his late eighties, and riding a Moulton bike into his nineties. In 2010, on his 90th birthday, he unveiled the prototype MDev 90 — a new aluminium and carbon fibre-frame bike that can be put together in 20 minutes.

Fiercely intelligent, some would say eccentric and idiosyncratic, he followed through on his convictions. He mourned the decline in British manufacturing, believing in the superiority of moral over financial rewards: “Man should make things — make a profit, of course, but don’t take the money gain as the prime judgement”.