Why is it that powertrain evolution in motorcycles has not kept pace with that in motor-cars? Were attempts made to devise bikes with front-wheel or both-wheel drives? Intrigued by these questions, Piyush Sonsale decided to dip into motorcycle history. As he garnered fascinating information, he also got in touch with companies involved in such innovations overseas to get a complete picture
“Now I know how owls feel,” I thought to myself as my head pointed towards the corner exit and my body swayed laterally out of control with the bike. Legs stuck in ankle-deep slush, the helmet visor still mud-stained from my last fall, I struggled to find traction on the rear wheel of my bike while the spectators witnessed my helplessness. Finally, I steered out of my misery by stepping out and pushing the bike. Well, my first off-road experience on a motorcycle wasn’t exactly, er, smooth, but it gave birth to an idea in my head. What if motorcycles were all-wheel driven? Now, most of us have seen the wonders of all-wheel drive cars on YouTube and sported a 4 X 4 vehicle wallpaper on our desktops some time or the other, but, as they say, you don’t get it till you do it. So back to the question. As Leonardo DiCaprio says in ‘Inception’, “What’s the most resilient parasite? An idea!” I was possessed by the idea and had enough faith in human curiosity to believe that such experiments had been done in the past and, maybe, some exist even now. I was right.
Wiping the dust off motorcycle history, I found a treasure-trove of what can only be called marvellous engineering feats. Before getting nerdy, however, let’s find out what this ‘drive’ term I have been using means. The ‘powertrain’ (engine-transmission-countershaft-final drive) transmits the engine’s power and torque to the wheels. The wheels transmit the same to the ground by spinning and as a reaction the motorcycle moves. Conventionally it’s the rear wheel that gets the honour and is said to be ‘driven’. The front wheel in this case is called a ‘dead wheel’ as it only steers (directs) the motorcycle.
There are three ways in which motorcycle wheels can be powered or ‘driven’: a) rear-wheel drive (RWD), b) front-wheel drive (FWD), and c) all-wheel drive (AWD). Among these, the rear-wheel drive system is the only one conventionally used in on-road, off-road and even racing prototype bikes. However, in this article we are concerned with the unconventional, with experiments that never made their way to the mainstream. Let’s examine why.
All-wheel drive (AWD)
The all-wheel drive system is probably a communist idea since it involves distribution of the engine’s power and torque to both the wheels of a vehicle. But the distribution of power may not be equal. A capitalist intrusion? Well, whatever the case, the AWD gives pulling power to both the wheels and amazing climbing and off-roading ability to the vehicle.
The second chain
powering the gearbox on
The under tank gearbox
and shaft drive
There are two types of AWD systems: i) Both the wheels are constantly driven. ii) The front wheel is powered only when the rear one loses traction. Used only to regain traction.
An American brand called Christini has developed a mechanical linkage to power the front wheel. Their patented technology makes use of a combination of chain and shaft linkages to transmit the engine’s power and torque to the front wheel. They use a second chain drive apart from the one powering the rear wheel. Mounted on another countershaft sprocket, this chain powers another gearbox located on the frame. A shaft drive from this gearbox, passing from under the fuel tank, enters the head tube of the bike. Counter-rotating bevel gears then pass the power to the lower triple clamp. A chain-sprocket mechanism in the triple clamp further passes the power by rotating two telescopic counter-rotating shafts. These run down the length of the forks and finally transfer the engine power to the front wheel. Phew!
|The bevel gear mechanisn in the head tube which allows angular linkage in the front powertrain||
The chain- sprocket mechanism in the lower triple clamp and the counter rotating shafts it powers
Approximately 80 per cent of the engine’s power is transmitted to the front wheel and is used to regain traction when the rear wheel slips. Otherwise, under normal conditions, one-way clutches in the front wheel hub keep the front wheel passive. Christini use this mechanism to modify frames and forks of standard rear-wheel driven KTM and Honda off-roaders and sell these modified frame kits under their brand-name. The mechanism, though complicated, is the only one available in a production line and their decent success in the arena of off-road motorsport has proved its worth.
Suzuki’s 1985 2wd concept, the Falcorustyco
The Nuda, showcased in 1986
Another interesting innovation and, perhaps, one of the most successful implementations of a mechanical all-wheel drive system has been done by an American firm called Rokon. They were the first to make the concept digestible and offer a whole range of two-wheelers based on the same. The first Rokon concept, the ‘Trail-Breaker’, was tested in the late 1950s and later evolved into a three bike production range. The Rokons are, shall we say, a mutated motorcycle sub-species aptly called ‘Mototractor’, characterised as they are by a huge but simple chassis design and chunky off-road tyres like the ones seen on tractors and industrial cranes.
First production Rokon — the ‘Trail-Breaker’
Rokon offers a host of accessories such as side panniers or a front tray to suit your purpose
The 2-Trac-powered AWD Yamaha WR450F off-roader that surfaced in 2004
|The alien looking ‘oily’ concept bike Dryvtech 2x2x2 with its maker, Ian Drysdale|
|Is it a robot? Is it a lunar rover? No! It’s the Dryvtech 2x2x2’s handlebar and headlamp assembly!|
Ian Drysdale riding the two-wheel driven, two-wheel steered Dryvtech 2x2x2 cocept. A dream come true!
The Japanese giant Suzuki were the first to play with the hydraulic AWD idea. They displayed a dummy concept bike, called the Falcorustyco, at the Tokyo Motor Show in 1985. A year later, they came up with a GSX-R750-powered concept, called the Nuda, which actually worked.
Yamaha and the Austrian brand KTM have also developed their own hydraulic solution to power the front wheel of a bike. The Yamaha system, called 2-Trac, was developed along with suspension maker Öhlins. The system had been under development since 1985 and was tested on various models, mostly off-roaders. A 2-Trac-powered YZF R1 was also tested and showed noticeable improvement in lap times on a race track. The system uses a chain drive to power the rear wheel while the front isdriven by a hydraulic motor in the wheel hub. The KTM version has a similar design and also shares the technology partner (Öhlins) with Yamaha, but the two bike-makers have separate patents for their respective innovations.
However, the most ground-breaking innovation I came across was the Australian inventor Ian Drysdale’s Dryvtech 2x2x2 concept. The third 2 is not a typographical error. The Dryvtech was a 2 (wheel) X 2 (wheel drive) X 2 (wheel steered) motorcycle! It had a specially built 250-cc, two-stroke internal combustion engine as the main powerhouse. The engine actuated a hydrostatic (positive displacement) pump, which pressured hydraulic oil through steel tubes. This oil transmitted the engine’s power and torque to both the wheels by actuating a hydraulic motor located in the wheel hubs. The all-wheel steering system also used hydraulics to steer both the wheels, but the handlebar-to-wheel ratios varied for both the wheels. The rear wheel turned a little late to allow the front wheel counter-steer in a turn.
The list of innovations does not end here. The brakes worked using the hydraulic system used to drive the wheels, both wheels had single-sided swingarm with monoshock suspension and the wheels were concave, depressing in towards the hub on the side where the hydraulic motor was attached. The Dryvtech 2x2x2 was a working prototype and, at a basic level, proved most of the theories of its creator. Sadly, it never underwent further development or production and the prototype exists as a museum exhibit at the Donnington motor museum in the UK.
- Reduction in power wastage as power is distributed between both the wheels
- Reduced wheel spin, tyre wear
- Increased climbing ability due to increased traction
- Benefits in racing: Tighter corners, increase in corner speeds. Lesser high side crashes
- Benefits in off-roading: More traction, faster jump recovery
- Reduction in power wheelies
- Complex design
- Increase in weight, mass
- Complexity in division of power and splitting torque
- Leakage and resultant part failures a big area of concern where the system is hydraulic
- Difficult to repair, high maintenance cost
- Increased production cost
One of the very few surviving Megolas
Front-wheel drive (FWD)
Here, the front wheel is the protagonist; it steers as well as drives the bike while the rear (dead) wheel follows. FWD systems have been tried and tested on motorcycles by modifying rear-wheel drive bikes, but the innovation that intrigued me was an attempt back in the 1920s. A motorcycle called Megola was produced in Germany for a brief period between 1921 and 1925. Although not very efficient mechanically, it was a production model and was popular for its ground-breaking design. The Megola had a 640-cc, five-cylinder Gnome Monosoupape (single-valve) rotary engine as seen in World War I fighter planes with radially arranged cylinders. It produced almost 15 PS of power in the standard version and over 25 PS in the sport version, attaining speeds upto 140 kph. The engine was mounted in the front wheel (between the spokes) and the cylinder valves were mounted sideways on the cylinder heads. The axle doubled up as the crankshaft, which remained stationary while the cylinders rotated radially with the wheel. Furthermore, the crankshaft was hollow and also served the purpose of the inlet manifold.
The Megola’s front wheel-mounted engine
The bike had no flywheel, no clutch nor a gearbox. The engine was fired by spinning the front wheel and stopped by switching the ignition off. The fuel was stored in the frame and fed a reservoir located over the axle. Fuel from this reservoir was then fed into the engine by gravity. The tyre tube was like a sausage (closed at both ends), so it could be pulled out without dismantling the wheel assembly. And the air striking the rotating cylinders cooled the engine as the bike moved. Genius!
About 2,000 Megola bikes were produced, but only a handful survive today.
In 1935, a group of German engineers (Killinger and Freund) created a front-wheel drive prototype by modifying the Megola design to improve its handling, aerodynamics and reduce engine weight. However, their production plans never materialised on account of the outbreak of World War II. This makes the Megola the only production FWD motorcycle ever made.
FWD Hypothesis (Based on the Megola)
- Greater traction under braking and otherwise too as the heavier front end loads the front wheel to increase tyre contact patch
- Better handling due to low centre of gravity, especially in racing. (The Megola won the German Motorcycle Championship in 1924)
- Less lateral movement of the front wheel is required to maintain balance as the centre of mass is closer to the front wheel
- Reduction in rear wheel slides round corners as the front wheel is powered
- Lesser power losses in the powertrain
- The wheel-mounted engine increases unsprung weight (mass not supported by the suspension) and adds greater load on the suspension, reducing braking force and acceleration. Also the undulations on roads may damage the engine
- Heavy steering as the front wheel is heavy
- Since the centre of mass is near the front wheel, the rear end is lighter, which may result in frequent stoppies while braking
My find gave rise to a question: are motorcycles less fascinating than cars? My mind immediately cried out, ‘No way!’ Then why is it that ever since Gottlieb Daimler gave us the first motorcycle, the basics have not changed much while all the three drive systems (front, rear, all-wheel) have steadily evolved in cars? The answer is that bikes are not flexible enough. It’s the whole two-wheel business. Motorcycles evolved from bicycles and the basic geometry remains the same. Lateral movement of the front wheel is easiest by using forks since the front swingarm linkage has a complicated mechanism. Transmitting power to the front wheel while allowing it a free lateral movement is difficult and the powertrain losses are heavy.
Motorcycle chassis are built to be supported by two wheels, which puts restrictions on the weight and mass of a motorcycle. In order to counter the gyroscopic, inertial and centrifugal forces, motorcycles have to lean in the direction of the turn. So a bike needs to be thin, especially at the wheel level.
The simplest solution to all these was to power only the rear wheel. Motorcycle design and ergonomics evolved with this geometry. So did the way motorcycles are ridden. Billions were then spent in refinement. Hence the extra bit of traction was not worth the increase in weight, complexity and expense. However, with giants like Yamaha and KTM working on such systems, it won’t be wise to rule out the possibility completely. For the time being, though, I had better learn off-roading!