Single cylinder engine

A single cylinder engine is the most basic piston engine configuration of an internal combustion engine. It is often seen on motorcycles but has many uses in portable tools and garden machinery. It has been used in cars and tractors.

Characteristics

Single cylinder engines are simple and compact, and will often deliver the maximum power possible within a given envelope, though they are less suitable for the biggest and most powerful engines. They require more flywheel effect than multi-cylinder engines and the rotating mass is relatively large, restricting acceleration and sharp changes of speed. They are prone to vibration (though this can be controlled with balance shafts). Cooling is simpler than with multiple cylinders, potentially saving further weight.

Pros and cons

Single-cylinder engines are simple and economical in construction. The vibration they generate is acceptable in many applications, while less acceptable in others. Counterbalance shafts and counterweights can be fitted but such complexities tend to counter the previously listed advantages.

Components such as the crankshaft of a single-cylinder engine have to be nearly as strong as that in a multi-cylinder engine of the same capacity per cylinder, meaning that some parts are effectively four times heavier than they need to be for the total displacement of the engine. The single-cylinder engine will almost inevitably develop a lower power-to-weight ratio than a multi-cylinder engine of similar technology. This can be a disadvantage in mobile operations, although it is of little significance in others and in most stationary applications.

Uses

Early automobiles and motorcycles were all single cylinder, as were engines for marine use. The configuration remains in widespread use in dirt bikes and is almost exclusively used in portable tools, and garden machinery such as lawn mowers.

The bestselling motor vehicle of the world, the Honda Super Cub, has a very fuel-efficient 49 cc single-cylinder engine and big-diameter 17-inch wheels (rolls smoother over obstacles).

Some motorcycles with strong single-cylinder engines are available today. There are sportbikes like the KTM 690 Duke R which has 70 hp 690 cc single-cylinder engine and reaches 125 mph (200 km/h) with a curb weight of only 150 kg, dual-sport motorcycles like the BMW G650GS, as well as classics like the Royal-Enfield 500 Bullet with a long-stroke single-cylinder engine.

Nearly all Auto rickshaws have very fuel-efficient single-cylinder engines. Typical mileage for an Indian-made auto rickshaw is around 35 kilometers per liter of petrol (about 2.9 L per 100 km, or 82 miles per gallon [United States (wet measure), 100 miles per gallon Imperial (United Kingdom, Canada)].

Racing classes

Off-road

• Enduro, Hare scrambles, Motocross, Rally raid, Track racing

Street

• Supermono, Supermoto, Super single

Go-cart

• Kart racing, crosskart

Gallery

External links

• Images of several single-cylinder marine engines