https://www.youtube.com/watch?v=6BCgl2uumlI
Yes, you guessed it, in my continuing but erratic series on bikes that manufacturers possibly should have thought twice about, today I’m going to look at the small number of rotary-engined motorcycles.
The rotary engine, or the Wankel engine to give it its proper name, was designed by German engineer, Felix Wankel and was his answer to the problem of power loss in the conventional internal consumption engine. The normal reciprocating engine has pistons that go up and down (or across, or all of the other combinations) and the crankshaft of the engine then translates this up and down motion into a rotating motion that is then transferred by some method to the driving wheels. Wankel reasoned that, if the internals of the engine simply rotated in the same plane as the transmission and final drive, most of the power loss that occurs when the crankshaft switches the direction of travel could be eliminated.
The following animation shows the operation of the rotary engine in a bit more detail.
It didn’t happen overnight, as the ad says, but it did happen 🙂
The rotary engine made its first appearance in cars, mostly made by smaller, boutique German manufacturers, and soon in a more “mainstream” brand as Wankel licensed his technology to Mazda in Japan. Distinguished by a distinctive “buzzing” exhaust note, the rotary engines didn’t exactly set the world alight. This was especially since Mazda fitted the engine first into a small coupe that also continued to run alongside the conventionally engined car. Hence the full advantage of the Wankel’s excellent power-to-weight ration was not fully exploited.
But the rotary engine certainly made a splash, especially since it was the first truly well developed attempt to put anything but a conventional reciprocating engine in a car. The hot car set soon took to the concept, finding that the engine was open to tuning and, despite some initial disadvantages, the rotary engine carved out a niche in the market that has lasted to today with iterations of the Mazda RX series of personal coupes being up to its 8th generation.
However, as Jeremy Clarkson used to say, there was a problem (or a few of them). Firstly, despite producing oodles of power (by comparison) the rotary engine was notoriously thirsty, a fact that has persisted up to the present day though this has been ameliorated to a certain extent by constant refinements in the design. Secondly the problem of sealing of the rotating module withing the combustion chamber was a problem from day one. Over time, and with the use of more exotic materials, the seals now seal much better. Thirdly, the engine exhibited a ferocious appetite for spark plugs, no doubt exacerbated by the extremely high temperatures within the combustion chamber. Developments in this area have also reduced this problem dramatically but, with all these pretty major issues coming to light early in the motor’s history, it wasn’t surprising that it never really grabbed the attention of mainstream owners, manufacturers and the general public.
Unsurprisingly, it didn’t take too long for someone to figure that a light weight, powerful engine would be ideally suited to being used in a motorcycle. The reasoning isn’t quite as elementary as you’d think because conventional motorcycle engines are, by their nature, light anyway. And, unless the engine was located in the frame in a longitudinal fashion, the problem of switching the direction of rotation was still going to be a problem.
The first rotary-engined motorcycle was, pretty obviously, from a small German manufacturer, Hercules.
The Hercules motor had a capacity of 294cc and produced around 23bhp. On the subject of cubic capacity, debate raged at the time (and still does) as to how one could accurately measure the capacity of a Wankel engine. In Europe it was marketed as a Hercules, but is was branded as a DKW in Britain. The marque was well-respected there as they made some very good small cars. The Hercules was released in 1974. Road test results were generally favourable but the huge fan on the front of the engine to try and cool the ferociously hot engine did reduced ground clearance. With a small capacity and low power, the Hercules was never going to set the world alight in the performance stakes, but it was a start. Lubrication was achieved by mixing the oil with the petrol in the fuel tank (manually) and the first model had a drum front brake. In 1976 an upgrade was introduced with oil injection (a la the Japanese manufacturers), It also had an 18″ front wheel and disk front brake.
Wankel’s concepts had also been noted in Japan where Suzuki had been tinkering with the design for years. As well as having the engineering expertise to produce the bike, they also had the metallurgical expertise to develop the materials necessary to ameliorate the huge temperatures developed within the engine. In 1974 they produced their own rotary-engined bike ,the Suzuki RE5.
It’s pretty easy to see that Suzuki basically used the GT750 as the platform for the RE5. Unlike the Hercules, Suzuki turned the engine through 90 degrees so that the rotor rotated in the same direction as the wheels. Apart from the engine, As a mainsteam manufacturer, Suzuki had the ability to market the bike more effectively and the bike received plenty of advertising.
But, as so often is the case, the Japanese manufacturer marred the pudding by making the bike and its ancillaries ridiculously complex and, as a result, ridiculously heavy. It had water-oil cooling, two sets of coils for the ignition, three separate oil pumps, two separate valves in the inlet tract and the carburettor was activated by 5 (yes, FIVE) throttle cables. The exhaust system was dual-skinned as the pipes got ferociously hot. A little air intake can be seen in the picture, its job was to duct cooler air into the gap between the inner and outer exhaust pipes. The single rotor engine was fuelled by a car-type carburettor that was also hugely complex compared to a conventional motorcycle carby.
Added to all of this, the bike developed less power than the more conventional GT750 and it was always going to suffer by comparison. Suzuki produced 6000 units of the two models but it was a dead-end street as their conventional motorcycles at the time included the much more desirable GS1000 which was lighter, simpler, faster and an altogether superior bike. In 1985 Cycle World magazine in the USA named the RE5 as one of the world’s ten worst motorcycles, a bit harsh but probably fair. Surprisingly, plenty of them seem to have come to Australia and examples regularly turn up at bike shows, some of them even being ridden on normal registration!
There were several other rotary-engined attempts, the most notable (for its relative modernity) was the Van Veen OCR100, made in the Netherlands.
It had a licensed version of the Wankel engine along with cast wheels, disk brakes all round and very high build quality. But, it was awfully heavy (over 350kgs) very expensive, ($15000 eye-watering American dollars ) and, from the outset, there were problems with the Comotor engine. Only 38 examples were produced though the tooling and remaining spares were bought by another entrepreneur in 2011 who managed to make 10 more of them. (God knows how much they cost, though)
From here we jump forward quite a few years, to 1987 where we encounter the first of a series of rotary-engined motorcycles all bearing the same maker’s name, Norton. The first of the line was called the Classic and it was a most innovative machine. The engine was not based on the Wankel but was of British design (though the principle was the same). The engine proved to be underpowered so Garside obtained permission to produce a Wankel engine but introduced many detail changes along the way. The engine was air-cooled, a seeming no-no in light of how hot rotaries run. But the frame, which was of a semi-monocoque design also acted as a ram air duct forcing cool air from the front of the bike through the interior of the rotors (!) Despite this innovation, the motor still ran too hot and the high temperatures compromised the carburation, producing constant problems getting the mixture “just right”. The bike was, however, lighter and more powerful than the Suzuki RE5 but only 100 of them were ever made. A police-kitted bike called the Interpol was also produced in limited numbers.
The successor to the Classic was the Commander, produced between 1998 and 1992 (253 units altogether). This time the engines was water-cooled and again two versions were produced, a civilian one and a police-spec one. Much of the running gear was sourced from the Yamaha parts bin.
Norton’s next rotary was a home-grown one that was developed away from the factory and without official factory involvement. This was the RCW588.
Using the air-cooled engine from the Classic with considerable enhancing, the RCW was arguably the most successful of all of the rotary engined motorcycles. It won a TT race in 1992 in the hands of Steve Hislop. More importantly, the bike won the 1994 British Superbike Championship in the hands of Ian Simpson.
Finally we come to the last of the Nortons, the F1, a road-going version of the RCW588. Produced in 1990-91 (production figures not obtained) it was water-cooled (engine derived from the Commander) and carried over the features of the race bike with suitable adaptations for road usage.
The Nortons still make regular appearances in Classic racing overseas and local sidecar hot-shot, Doug Chivas has an outfit powered by a Norton rotary engine that sounds awesome and shoots out gouts of flame on over-run!
Here’s Dougie with Wade Boyd and Christine Blunck who rode the outfit at the Island Classic a few years ago.
So concludes the almost total history of rotary-engined motorcycles. It probably always was a dead-end street so all of these bikes can rightfully be called orphans, but it’s interesting, isn’t it?