Since the dawn of Modern IC engines, manufacturers have made countless configurations of them. There is a V-twin, an inline 3, V4, single cylinder and many more. Some of them like the V-Twin stood the test of time and have been with us for about 80 years. There is also another parameter related to the engine, with which manufacturers seem to play a lot and that is Crank rotation. We have 90-degree crank, 180-degree crank and so on. Keep in note that this is only possible in multiple cylinder configurations because a single cylinder can only go up and down on its own. But there is one special configuration, the 270-degree crank which stands out from the rest in terms of both torque and power delivery. So let’s talk about it in detail.
The visual representation of a 270-degree crank setup looks like this:
In the picture, it is clearly visible that one of the pistons is at the top dead center and the other one is somewhere in the middle of the cylinder. To understand how this configuration is better than the rest, you need to understand what the rest of the configurations lack. Imagine a cycle, the paddles or the footrest at the 180-degree position from each other. The moment you will put your foot down to paddle the cycle, the whole structure of the cycle vibrates or shakes. Even the force which you need to apply to make the paddle travel 90 degrees from its original position, is high and the distance covered by the cycle isn’t even that big. The same scenario is with pistons in this configuration, there are vibrations, very little bottom end torque generated for a comparatively more force applied.Now, let’s examine the 270-degree crank position. Imagine the pistons when one of them is at the top position and the other one is somewhere around the middle. Let’s apply the force, the one at the middle of the cylinder can easily be pushed upward by the downward motion of the second piston which is at the Top Dead Center (TDC) and is bound to travel downwards. The primary forces produced are balanced by the vertical balance shaft and the vibrations are balanced by secondary reciprocating forces, as in a 270-degree crank, these forces cancel each other out.
A beautiful exhaust note and refined nature of the motor becomes the defining characteristics of the motorcycle as well. Triumph's Bonneville series have used the 270-degree crank rotation to stabilize their big engines and deliver smooth and linear torque throughout the rev range. Even the new Royal Enfield 650 twins, showcased at EICMA 2017 in Milan had the same configuration. If the math is to be believed, then we will have a smooth running Royal Enfield on Indian roads soon enough. The likes of which have never been heard before. But again miracles are a part of India, isn't it? For everything related to motorcycles, stay tuned to BikesMedia. By: Yetnesh Dubey