good motoring
Shifting gears gets easier
H. Kishie Singh

We are all used to a manual gear box. It is all we have had on offer and have an addiction to it, to the extent that we shun all other types of a gear box. The Manual Transmission (M.T.) gear box houses a series of gears with different ratios. A coupling devise is required to separate the engine from the transmission while changing gears. For this, the clutch plays a vital role in manual transmissions. Without the clutch, the engine would be delivering power to the wheels constantly and any time the vehicle stopped the engine would stall. It is not be possible to change gears without a clutch.

When the clutch pedal is depressed, it is fully disengaged. No power is transferred from engine to the wheels. With the pedal released, the clutch is fully engaged and the engine's power is transferred to the wheels. The clutch acts as a rigid coupling. The manual gear box is used by just about every manufacturer. The shift time is about 400 milliseconds. The downside of the (M.T.) is the shifter and clutch are in constant use. The clutch wears out and needs replacement. Next, we have the Robotised Manual Transmission (R.M.T.). It has the same cluster of gears but they are operated by an electronic clutch. The immediate advantage is the shift time is about 120-150 milliseconds.

The downside is that at slow speed, while parking, it feels jerky. It cannot compare for smoothness with the M.T. clutch. However, the smoothness is sacrificed for the swiftness of change. Almost all the European manufacturers favour this type of gear box. The robotised manual gear box is ideal for small cars, which is why the Europeans prefer it. If one clutch does a good job, two will do it twice as well. So we have the dual-clutch transmission. The top-end super cars usually have a 6-speed gear box, gears 1-3-5 have one clutch and 2-4-6 have a second clutch. Each gear set has its own clutch.

The advantage is obvious, a longer clutch life. The shift time is 140-200 milliseconds. Another advantage is that it combines the smoothness of an automatic gear box with the swiftness of an M.T. The downside is that the dual-clutch gear box is heavy, complex and expensive as compared to a traditional M.T. For ease of driving, there is nothing to beat Automatic

Transmission or A.T. It gives you a smooth gear change and is perfect at slow speeds. The shift time is about 350 milliseconds. Just about every car in North America favours A.T. The downside is that the flywheel absorbs energy and is not fuel efficient.

The most revolutionary and practical automotive invention is the Continuously Variable Transmission — C.V.T. It is a belt, usually steel, and a pair of pulleys. One has a fixed diameter, the other has a variable diameter. As the engine r.p.m. build up, the diameter of the second pulley varies. This changes the gear ratio. The C.V.T is simpler in design, light weight and least expensive to build. Shift time? Zero, since it is always in the right gear! Good for small sedans and fuel efficient. Downside. Different from conventional gear boxes, it needs getting used to and cannot cope with powerful engines. Happy motoring!

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