Automatic vs Manual had been a topic hot for the four wheeler segment ever since the first automatic car was born in 1940 by General Motors’ Cadillac. And now, it seems like it will create a havoc in the two-wheeler segment. Or would it?
Everyone agrees that having gears and ratios is necessary to the inner workings of the transmission to power the vehicle but there is no general consensus regarding what kind of transmission is most suitable – auto shift or manual clutch lever and leg shifter. If you take cars, 90% people of the top five developed countries love the auto shift, but the same was not applicable to two-wheelers as hardly any manufacturers had them, until recently when the scooters came in. A device that to this day is frowned upon in the motorcycle community and blaming it for taking away the ‘biking experience’.
Nonetheless, they gave automatic a new meaning to the two-wheeled world and were largely preferred for their ease of use and decent performance for a very limited run. It became a fine option for urban commuters, youth and casual riders.
Honda has been a pioneer in developing new forms of transmission systems and clutch designs. Every manufacturer, if they have an automatic, have their own versions of them. They are basically trimmed into three kinds that are out there on the roads currently in use:
This is the most simplest of them all which are also famously known as CVTs (Continuously Variable Transmissions). Introduced by Honda in 1973, it was embedded into India in the form of a Kinetic Honda. The country’s first favourite scooters that was once held by every college and office goer. Every scooter since then is running on the CVT technology that allows you to just twist the throttle and you are set to go. No shift lever, no neutral, no reverse and no leg pulls/push.
The CVT has three parts to it – two conical pulleys, a centrifugal clutch and a belt. As the engine rpm increases, the centrifugal clutch pushes the belt onto one of the conical pulleys and this causes the wheel to rotate, depending on the position of the belt on the conical pulley. The faster the engine revolves, more of the clutch is displaced and this pushes the belt to a higher section of the conical pulley. As a result, accelerating with a CVT is an incredibly smooth uninterrupted process.
All scooters available in India are currently rinning on the CVT transmission and every brand have their own variations of the same.
Preserved for the four wheels, this piece of technology was too brought into the biking world, again by Honda with their VFR1200F sport touring motorcycle in 2010. The engineers at Honda managed to take the Formula One derived transmission and put this into the confined spaces of two wheels and make it change gears without any interruptions. The DCT (Dual Clutch Transmission) uses two clutched instead of one. You get one for odd gears and one for even gears with benefits such as rapid and smooth shifting, genuine compression braking and a stall-proof operation.
The thumb operated shift controls negates the discernible clutch grab that would otherwise give the distinctive driveline lurch. This will also provide eminent fuel economy along with the ease of use and convenience.
Currently, Honda is running many models with this transmission including the VFR1200F and the recently launched CRF 1000L Africa Twin.
They are not an automatic in a true sense. This kind of a system will allow the rider to manually change the gear with the push/pull of a leg but there is no handlebar-mounted clutch lever. Also called as auto-clutch, they are predominantly found in all terrain vehicles and entry-level dirt bikes.
This system allows the rider to stop and move in any gear and is activated only when the engine rpm increases from an idle situation. As the engine rpm increases, the centrifugal clutch pushes the steel shoes and then the driveshaft. Such a mechanism wears out sooner than others, especially in a stop/go traffic urban commute.
This clutch was seen mostly on all scooters and bikes you get in South East Asian countries like Vietnam or Thailand. Centrifugal clutches are also majorly used on go-karts, snowmobiles, and other vehicles of conveyance.
There is a surprising story behind Honda developing the unique automatic centrifugal clutch for its Cub series. The goal was to produce a bike that could be operated one-handed, as at the time restaurant deliveries were made by bicycle riders carrying boxes with their right hand, whilst steering with their left. The result was the birth of the revolutionary automatic centrifugal clutch.
Recently our Indian manufacturer TVS Motors got themselves awarded with an Indian patent for automatic hybrid transmission (AHT) system for two-wheelers. A piece of technology which is an amalgamation of fixed speed transmission mechanism (FSTM) and a continuously variable transmission mechanism (CVTM).
The patented system of TVS gets the best out of this two system, especially their positives at low speeds. At high and constant speed and acceleration conditions, the FSTM fails to provide an efficient gear ratio due to constraints and that is where CVT steps in to also provide smoother power delivery. This will enable smoother power delivery and better efficiency at all operating speeds and condition of the engine irrespective of frequent acceleration.
Source: Cycle World