Saturday, 20 January 2018

Wellworthy Al-Fin Bonding: Cool at Speed.

This is a blog relating to an advertising brochure published by the Wellworthy company, in which are detailed some of the successes gained during 1951.

The choice of an expert

Wellworthy Piston Rings Ltd. was based in Lymington, Hampshire and manufacturers of pistons, rings, cylinder liners and brake drums. They were also the exclusive licencees of the Al-Fin process. This process was employed to produce a bi-metallic component, usually consisting of a finned alloy muff surrounding a cast-iron liner. This bi-metallic arrangement offered the best of both worlds, the undoubted qualities of cast-iron as a bearing surface and the efficient dissipation of heat through the alloy muff. There was also a considerable weight saving over the traditional solid cast-iron component. 

It was an engineering solution that the racing world had long been waiting for and was very eagerly adopted at the time. Primarily it was used in the production of brake drums and engine cylinder barrels, both of which saw an immediate gain in efficiency.

Al-Fin brake drums

Al-Fin brake drums were quickly accepted as the best available at the time and used by leading race teams and drivers.

The following manufacturers specified and used these drums throughout the 1951 racing season:-

                                                Allard                    Frazer-Nash                       Jowett
                                                Healey                   Connaught                         Aston-Martin
                                                H.W.M.                  J.B.S.                                  Kieft
                                                                                Lester M.G.

Al-Fin motorcycle engine barrels

Al-Fin motorcycle cylinder barrels were used by Norton to win the World Championship in 1951.

They were also used by the following motorcycle manufacturers and machines:-

                                                                J.A.P. – 4B Speedway engine
                                                                Norton – Manx/500T
                                                                Triumph – Thunderbird/T100
                                                                Velocette – Venom/Viper/MAC

It is fair to say alloy muffs had been fitted to iron liners on many occasions previously, but this generally consisted of a machined alloy muff pressed or shrunk onto the outer diameter of the liner. The interference fit that is essential for good heat transfer clearly disappears as the temperature of the component rises, as alloy has a coefficient of expansion four times that of iron. This can result in local ‘hot-spots’, distortion and unpredictable behaviour, all of which should be avoided like the plague.

The Al-Fin process was a completely different animal and relied on the bonding of the two dissimilar materials. This bonding process was a closely guarded operation and was covered by the following:-Patent No. 599684                                           Patent No. 599725
                                               Patent No. 606330                                           Patent No. 652794

Applications:-    No. 5859/48                        No. 27437/50                     No. 30264/50

Wellworthy Piston Rings Ltd. Ampress Works, Lymington

The Al-Fin process was originally developed by Fairchilds Engine and Airplane Corporation, New York, USA. It consists of the formation of complex layers of inter-metallic compounds common to both materials applied to the surface of the iron, on to which the alloy is cast. This ensures that a true bond between the two materials takes place.