Like so many ‘original’ ideas, the 1973 John Player Norton was not entirely original and, of course, it was not all my own work. It was created by a team led by John McLaren and managed by the late Frank Perris who, to his credit, accepted and approved my basic concept. And the concept was to give the motorcycle the smallest frontal area as possible by utilising one part to perform as many duties as possible – for one part to take the place of several parts.
I knew that the reason riders on racing bikes put their chins and chests on the tank was to reduce frontal area but I learned quite early in my racing career that raising my chin off the tank by 5 cms would take 100rpm or 4 kph from my top speed. In my first GP at ~Hockenheim a high, big capacity fuel tank added two seconds a lap compared to using a sprint tank. And I bought a book on land vehicles aerodynamics which described a motorcycle and rider as a ‘bluff’ object – a fairly large frontal area but short length and it said that reduction of frontal area was, therefore, more effective than a ‘streamline’ shape.
The 1973 John Player Norton was a development from the 1972 model and both owed hugely to my wonderful Arter Special Matchless G50 on which I first tried and proved most of the 1973 features such as the cast magnesium wheels, disc brake designs, engine cooling air ducting as well as the pannier fuel tank the 1972 bike had which improved the ‘feel’ of all three bikes so much. I had always wanted to get rid of the frame and to make a ‘stressed’ fuel tank to carry the loads instead; for 1973 I had my chance. Without the pesky frame tubes cool air could be taken to the carburettors over the top of the engine and the position of the centre of gravity could be controlled more easily and, most importantly of all, the frontal area could be minimised. We used stainless steel because it does not lose its strength as badly as aluminium does when welded. We visited the MIRA wind tunnel three times with our ideas for the fairing and, with the screen at a precise height, the best drag-area measured was 0.222 square metres.
As I write this, it is interesting to note that the Arter Special Matchless G50 was the step towards the 1973 John Player Norton F750 ‘Monocoque’ and that, in its turn, is the platform upon which Peter Williams Motorcycles is based. The target for PWM is to make modern bikes and, in particular, to make what we call the ‘Real Monocoque’. I mention above that I had always wanted to use the fuel tank a part of the chassis but the top aim is to use the bodywork as the chassis. The idea is from college fifty years ago! And at last I met some like-minded people who wanted to make motorcycles – better motorcycles. Greg Taylor was one of them and he and I are now partners in PWM. We realised that my ambition could only be realised with cash – by capitalising on the success and reputation of the motorcycles I used to race. There were only four John Player Norton ‘Monocoques’ made and as they were one of the first to have cast magnesium wheels and the first to demonstrate the advantages of the twin-spar frame configuration they are unique – and valuable. We figured that we could sell replicas for a fraction of the value of the originals and we could make them at a profit.
It has been a huge task to ‘reverse engineer’ two of the original JPN ‘Monocoque’ bikes but the use of modern measuring and manufacturing techniques has resulted in an extraordinarily high quality product. Every part was remodelled and redrawn on CAD by Greg and me. As an example of the quality overall, the high specification stainless steel sheet of the fuel tank/chassis was laser cut to an accuracy of +/-0.2 mm whereas the originals were cut with shears. Who knows what accuracy John McLaren would have achieved? The cut panels were bent with modern accuracy and fitted to the jig by Gavin Tappenden and welded with modern equipment and extraordinary skill and dedication by
Peter Williams Engineering 