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Freddy Prince formed The Rotrax company in a cycle shop in the city of Southampton where craftsmen made the famed Rotrax lightweight cycle frames.

It was to be later, in 1952 that Rotrax started to produce their first Rotrax Speedway Motorcycle Frames. Mike Compton, who was the Workshop foreman, together with the British Oxygen Company, developed a nickel-bronze brazing technique for the frame lugs and "Renolds 531" tubing that was to give the beautiful hand-built frame the strength and quality needed for track racing. This method of brazing was later adopted by the aircraft industry on their jet engine frames

The early Rotrax frames had a Red badge with RT in white letters on the head stock the same as the cycle frames.

Meanwhile, Alec Jackson (himself a former rider) had taken over manufacturing rights of the JAP speedway engine in 1951 and continued to hand build engines and spares for many years afterwards, later still to be taken over by George Greenwood.

The Rotrax frames were initially chromed by Blakes of Gosport and then sent on to Alec Jackson's in London for the fitting of a JAP engine. And so the Jackson-Rotrax was formed.

The earlier Rotrax Mk1 machines were fitted with 22 inch rear wheel whilst in 1956, this was changed to a 19 inch rear wheel. Former Norwich rider Phil Clarke made many of the Rotrax frames under contract from his workshop in Norfolk.

 

This evolved in 1969, which included an oil-in-frame lubrication system and a loop rear frame.

Frame: Rotrax design built with Reynolds 531 tubing and low temperature bronze welded throughout. Finished in bright polished chromium plate.

Front Forks: Telescopic type with concealed springs. Fork girders bridged for strength.

Clutch: NORTON type with multiple bonded plates. Chain wheel running on .25" rollers and incorporating rubber shock absorbers. Chain wheel 42T. Final drive sprockets 14T, 15T or 16T

Countershaft - Single Speed: Hardened steel shaft running on ball- bearings in alloy case.

Transmission: Primary Chain: 1/2 x .305 Renold. Final Drive Chain: 5/8 x .255 Renold.

Wheels: Strongly built on steel hubs with heavy gauge spokes and steel nipples. Knock-out spindles.

Rear Sprockets: Light alloy. Sizes 57T to 60T.

Footrest: Solid one-piece type supplied for fitting to R.H side to customers own positional requirements.

Rear Mudguard: Valanced at R.H. side to protect carburettor air intake from dirt.

Tyres:Special Speedway 2.75 x 23 front and 3.50 x 19 rear. Two solid security bolts fitted to rear wheel

With George Greenwood now in charge of producing the JAP Speedway Engine, the final development came about with the introduction of the 84S Four Valve DOHC engine designed by former rider Mike Erskine.

We are indebted to Tony Webb of Binbooks for the above information

The Rotrax

The Rotrax Mk I

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Rotrax
Mk 2