Friday, December 8, 2023

Peek inside Royal Enfield design books

Cover of Reg Thomas design notebook.
Royal Enfield designer Reg Thomas's notes are yours to puruse.

 It's an opportunity any Royal Enfield history buff would envy: a chance to leaf through the internal memos company managers wrote as they worked to create the British Royal Enfield motorcycles that established the brand that thrives today in India. 

That lucky history buff can now be you, to a degree. 

Royal Enfield Owners Club (UK) archivist Bob Murdoch recently completed the processing and upload of the final sections of the Reg Thomas Collection of company photographs, bulletins, memos and drawings the club owns. 

Bob wrote this in the December-January issue of the club magazine, The Gun:

"Several years ago, the club joined forces with Allan Hitchcock to buy a historic collection of Royal Enfield documents from the deceased estate of Reg Thomas, who joined Royal Enfield as a draftsman in 1945 and became Chief Designer for Royal Enfield/Enfield Precision Ltd.

"Sean Keogh, our website manager spent many hours uploading these photographs, reports, memos, drawings, and Reg’s personal design notebooks for you to view on our website."

Unsurprisingly, you will have to join the club to see them.

But no harm in giving you a taste of what I found fascinating as I glanced through the materials. What I liked most was getting a feel for the place. What concerned the executives, how did they shape their decisions, and how did they treat one another in the process? 

I can't begin to decipher most of the engineering specifics, but the human element I'm looking for pops out.

For instance, the archive offers a look through the design books and correspondence of long-time Royal Enfield designer Reg Thomas himself, starting in 1945.

The first subject he addresses is a "gun predictor," a precision aiming device for shooting down enemy airplanes. (Jorge Pullin has an item on these in his My Royal Enfields blog.)

In his textbook style writing, Reg Thomas records points brought up in a meeting June 6, 1945 with a  "Mr. Brown." Point No. 2 caught my eye:

"Enlarge main casting to eliminate protrusions and give outside appearance more aesthetic lines."

This for a weapon!

I couldn't help thinking of the Supermarine Spitfire, a deadly fighter plane of the war but also one of the most beautiful airplanes ever imagined. It's a cliche to say that something that looks right will be right. Could it be that some designers naturally wanted to make something that worked right look right?

In a later notebook, Reg Thomas made a sketch of the Royal Enfield Crusader Air-Flow fairing that has almost feminine lines. His June 2, 1958 drawings of a rear crash bar for "Durham Police Model" Crusaders is strictly tubular in comparison.

Drawing for Royal Enfield motorcycle fairing.
Drawing of Air-Flow fairing for Royal Enfield Crusader.

Reg Thomas worked on small (50cc to 98cc) designs considered to compete with Hondas and Suzukis. He even considered gear ratios for a junior version of the Royal Enfield Revelation bicycle.

There's a Reg Thomas letter tracing progress of his design for an overhead cam 175cc Royal Enfield. In May, 1963 executives considered the result sound and that production should go ahead. But in June, 1963, the figures compiled by the Cost Office showed that the 175 would be uneconomical and it was shelved.

In July, 1966, Reg Thomas was at work on the 736cc Interceptor motor. He made a note to himself to "try WIPAC (as a supplier) for air filters." And YOU are there.

By July, 1969, Reg Thomas was recording his tests of the 800cc Interceptor prototype that enthusiasts ever since have regretted never reached a production line. It was not easy going.

A piston seized at 867 miles. A new barrel and piston were fitted, and the fuel mixture was richened. This piston seized after 1,725 miles (at 95 mph!).

A new barrel, and a piston with reduced diameter, were fitted. This seized after 542 miles.

New oil scrapper rings were fitted to allow more oil consumption, and the engine ran for 5,000 miles using a pint of oil every 300 miles.

With no special preparation the engine was tested on the track at 115 mph, experiencing oil leakage through a porous head. Further changes brought a further 3,063 miles without trouble and oil consumption of 800 miles per pint.

His notes show that at the track the 800cc Interceptor touched 122 mph, equivalent to 7,210 rpm with a 20-tooth gearbox sprocket, and 123 mph with a 21-tooth sprocket at 6,970 rpm. Success indeed.

By the way, Royal Enfield test rider Richard Stevens used the 800 Interceptor on "a holiday run to the continent," Reg Thomas notes.

He brainstormed a list of ideas to improve the 800cc Interceptor. These included Italian handgrips. An oil warning lamp. A self starter! What could have been.

His last entry in the design book was Aug. 20, 1971:

"Specifications for 1972 -- 250s -- some 1971 models to be up-dated. New air filter with silencer tube. Glass fibre legshields for police model."

These were not to be. For Royal Enfield in Britain, 1972 would never come. Royal Enfield's future would rest with India.

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