[Ariel Red Hunter]

When I was big enough for a full size bicycle, my father found me a Rudge-Whitworth. Needless to say, like every kid with his first bike, I loved the thing. So what? do I hear? I was trolling through you tube when I ran into the Rudge Enthusiasts Club. Click goes my memory of my long ago bicycle. So I check it out only to find out that Rudge-Whitworth built some great motorcycles. TT winners in fact. And, being of mechanical bent, so to speak, I found that they built a 250cc class racer that anyone could buy nick-named the "radial valve wonder" and I was hooked. AND, even better, they offered super-sport model roadsters with the same engine in it! Of course you had to have pretty heavy coin in order to buy one, but of such things dreams were built. I guess if you were a Rudge dealer in those days, what are now called brochures were going out the door in an avalanche. But let's cut to the chase. All Rudges are pushrod over head valve jobs in their sport machines. Never made an overhead cam engine. The first of these engines came out in 1927, and the very few last ones were made in early 1939. Shifted over to war production, making whatever the war ministry told them to make. I was intrigued by the idea of a four overhead valve engine, with radial valves operated by two pushrods. How was this possible, I wondered. I was so fascinated by this whole concept, I had to join British e-bay in order to find a couple of pieces of paper that described this action, illustrated by a drawing that only sort of explains how this is even possible, let alone works. And between the cost of those two very old pieces of paper and the postage to get it into my hot, sweating little hands, it was an experience, let me tell you. How lucky we are to have the U. S. Postal Service in the USA let me tell you. So visualize a radial valve head. A hemispherical combustion chamber with four valves equally disposed in a circle, each portruding at a 45 degree angle to the valve chamber above the head. There are SIX rocker arms up there. I think. Could be eight. Can you imagine this? In another little pamphlet, obtained through the same ruinous financial manipulations as above, one of the engineers described the reasoning behind "The Mechanical Wonder of The Age" as the pamphlet described it. According to him, they were constrained by cost considerations to stick with push rod operated valves, and went with a four valve layout in order to get good breathing with light valve gear, so as to lower the loads on the push rods, so as to keep the pushrods as light as possible. OK, the interviewer asks, but why a radial layout rather than a pent-roof combustion chamber? Heat problems on the exhaust side caused head cracking. Head expansion in the exhaust valve area caused distortion, which also caused exhaust valves to loose their heads, which, of course is a calamity. This was with cast iron heads, of course. In the early 1930's, their foundry people came up with a way to blend aluminum with bronze to be able to cast bronze heads. Improved heat rejection, which allowed a higher compression ratio to be run. Now the Rudge was not a successful racer and TT winner in what used to be called the "Lightweight Class", but is now called 250cc class, just because it had a magnificent engine. Oh no, it had great brakes and handling and light weight to go along with it. You don't win on the Ilse of Man with just mucho horsepower. Now to cut to the chase. About 1934, using the aluminum-bronze head, they found that they could run a half pentroof-half hemisperical head. the half pentroof valves were in a line, while the exhaust were kept radial, for exhaust cooling purposes. Thus the "Semi-Radial Rudge". I wanted to see if it was possible to see one of these mechanical nightmares in action. And I found one video of a race in 2007(!) of a semi-radial Rudge in action. If you choose to watch this little video, note that the Rudges are running girder front forks, and what some folks call a "hard tail" frame vs other bikes, later ones, with modern front forks and swing arm frames. Have fun. Go to youtube Rudge Racing British Historic Racing 2007. Granted the guy can ride, but still!