Note (in the above photo) that this bike has his innovative "saddle tank" which is draped over the top frame rail, providing room below for the new and taller OHV engines then taking over.
The Irish McCandless brothers, Cromie and Rex, in 1950 achieved a new chassis synthesis – telescopic fork and swingarm suspension with supple all-hydraulic damping, a box-like twin-loop frame, and forward rider and engine positions. With it, Norton's single-cylinder Manx in 1951 outran Gilera's much more powerful transverse-four to carry the late Geoff Duke to the world 500 championship. When Gilera "Nortonized" their fours, they became unbeatable.
Yet how did chassis design advance from the bicycle’s flexy single-plane ‘diamond’ frame of the early days, into something that could handle rising engine power, 1925-1939?
Engineering and science are driven by crisis, forcing us to look beyond the usual. The failure of Newton's physics forced Albert Einstein to consider that time and space may not be absolute. His ideas were accepted because they worked. The same would be true of the Quantum Theory of Niels Bohr and others, which gave correct answers but only by abandoning traditional cause-and-effect.
Howard R. Davies did not change the world as Einstein and Bohr did, but he did change the motorcycle forever.
For years all I knew about this man was that his initials – HRD – were for a time part of the hallowed ‘Vincent-HRD’ brand, created in 1928 when Phil Vincent bought the remains of Davies’s little company for 450 pounds, as the basis of his own enterprise.
MORE KEVIN CAMERON:
Davies was born in 1895, apprenticed at AJS, and in 1914 finished 2nd in the Isle of Man Senior TT on a Sunbeam. When World War One broke out two months later, he volunteered, spent a year as a battlefield dispatch rider, transferred to the Royal Flying Corps, and received his pilot’s certificate in July 1916. Flying as an artillery spotter, he was shot down twice, was declared killed in action, and spent the rest of the war as a POW. Being a “guest” of the Germans gave Davies time in which to consider the design of improved racing motorcycles.
In the first postwar TT, 1920, he entered on AJS machines but broken valves – then a common ailment – put him out. Shortly he became their competitions manager, streamlining their racing operation. In 1921 he was 2nd in the Jr. TT (350) and won the Sr. (also on a 350), demonstrating the power of the new OHV engines AJS was building.
Leaving AJS in 1924, he entered motorcycle manufacturing as ‘HRD’, showing a prototype late that year. The problem he tackled was that of integrating the new, taller OHV engines into a stable but responsive chassis.
Motorcycles of the time were long and low, with two top frame tubes, one above the other, between which was slung a flat soldered fuel tank. This was practical only with the low height of side-valve engines. These bikes were often built in “keystone” form, in which the engine bolted to the downtube at the front and to the seat post at the rear, with no chassis structure beneath.
What Davies did to get extra room for a tall OHV engine was delete the lower one of the top tubes and make the fuel tank in a ‘saddle’ form, draped over that single top frame tube. He shortened the wheelbase, providing a more upright riding position, and continued the single downtube as a cradle under the engine to join the chainstays, of which there were “a multiplicity”. He placed the engine well forward, which enhances stability. Power came from the same proprietary J.A.P. OHV singles that many other makers were now using.
Why six chainstays? The greater power of OHV engines was bowing traditional chassis enough to threaten stability and even to make chains run off. George Brough would continue the trend with his SS100 liter-bike, which he gave “doubled stays” – 12 of them.
People liked the traditional long-and-low flat-tank look, so fashion might have rejected Davies’s creation had it not been sensationally successful;
- He rode the 350 version into 2nd in the Junior TT, and;
- He won the Senior TT, defeating the big names - AJS, Norton, P&M, and Scott.
In 1925 winning the TT was the pinnacle of motorcycle racing. Think how utterly impossible it would be today for anyone to design, build, and ride a bike to victory in MotoGP.
The following year he further updated his chassis, trying to stiffen the steering-head by using twin downtubes, both of which passed under the engine in 'cradle' form, then continued as lower chainstays to the rear axle. This 1926 HRD chassis was less successful than the first, but its 'duplex cradle' chassis concept continued in use as recently as the G50 Matchless (1958 – 1962) and Yamaha TD1 series (1962-68). Davies may not have been first to use such a chassis, but he did show what chassis updates could do.
The 'saddle tank look', made trendy by racing success, caught on. When George Brough needed to find a place to carry all the fuel required by his thirsty big road twins, he adopted the saddle tank but with a bulbous and roomy front end. When Indian and Harley management heavies toured the British industry in 1923 and '24, they saw the coming trends clearly.
That bulbous saddle tank look continues to this day in Harley-Davidsons and in Mr. Bloor's Triumphs.