Driveshaft

# Driveshaft

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Encyclopedia

A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement between them.

Drive shafts are carriers of torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

: they are subject to torsion
Torsion (mechanics)
In solid mechanics, torsion is the twisting of an object due to an applied torque. In sections perpendicular to the torque axis, the resultant shear stress in this section is perpendicular to the radius....

and shear stress
Shear stress
A shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...

, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, whilst avoiding too much additional weight as that would in turn increase their inertia
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...

.

Drive shafts frequently incorporate one or more universal joint
Universal joint
A universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion...

s or jaw coupling
Jaw coupling
A jaw coupling is a type of motion control coupling designed to transmit torque while damping system vibrations, which protects other components from damage. Jaw couplings are composed of three parts: two metallic hubs and an elastomer insert called an element, but commonly referred to as a...

s, and sometimes a splined joint
Rotating spline
Splines are ridges or teethon a drive shaft that mesh with grooves in a mating piece and transfer torque to it, maintaining the angular correspondence between them....

or prismatic joint
Prismatic joint
A prismatic joint provides a linear sliding movement between two bodies, and is often called a slider, as in the slider-crank linkage. A prismatic joint is formed with a polygonal cross-section to resist rotation...

to allow for variations in the alignment and distance between the driving and driven components.

## History

The term drive shaft first appeared during the mid 19th century. In Storer's 1861 patent reissue for a planing and matching machine, the term is used to refer to the belt-driven shaft by which the machine is driven. The term is not used in his original patent. Another early use of the term occurs in the 1861 patent reissue for the Watkins and Bryson horse-drawn mowing machine.
Here, the term refers to the shaft transmitting power from the machine's wheels to the gear train that works the cutting mechanism.

In the 1890s, the term began to be used in a manner closer to the modern sense. In 1891, for example, Battles referred to the shaft between the transmission and driving trucks
Bogie
A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

of his Climax locomotive
Climax locomotive
A Climax locomotive is a type of geared steam locomotive in which the two steam cylinders were attached to a transmission located under the center of the boiler. This transmits power to driveshafts running to the front and rear trucks....

as the drive shaft, and Stillman referred to the shaft linking the crankshaft to the rear axle of his shaft-driven bicycle
Shaft-driven bicycle
A shaft-driven bicycle is a bicycle that uses a drive shaft instead of a chain to transmit power from the pedals to the wheel. Shaft drives were introduced over a century ago, but were mostly supplanted by chain-driven bicycles due to the gear ranges possible with sprockets and derailleurs...

as a drive shaft. In 1899, Bukey used the term to describe the shaft transmitting power from the wheel to the driven machinery by a universal joint
Universal joint
A universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion...

in his Horse-Power
Horse power (machine)
A horse power is a now largely obsolete machine for using draft horses to power other machinery. It is a type of animal engine somewhat more sophisticated than a horse mill. A common design for the horse power was a large treadmill on which one or more horses walked. The surface of the treadmill...

. In the same year, Clark described his Marine Velocipede using the term to refer to the gear-driven shaft transmitting power through a universal joint
Universal joint
A universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion...

to the propeller shaft. Crompton used the term to refer to the shaft between the transmission of his steam-powered Motor Vehicle
Steam car
A steam car is a light car powered by a steam engine.Steam locomotives, steam engines capable of propelling themselves along either road or rails, developed around one hundred years earlier than internal combustion engine cars although their weight restricted them to agricultural and heavy haulage...

of 1903 and the driven axle.

### Vehicles

An automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

may use a longitudinal shaft to deliver power from an engine/transmission to the other end of the vehicle before it goes to the wheels. A pair of short drive shafts is commonly used to send power from a central differential
Differential (mechanics)
A differential is a device, usually, but not necessarily, employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it...

, transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

, or transaxle
Transaxle
In the automotive field, a transaxle is a major mechanical component that combines the functionality of the transmission, the differential, and associated components of the driven axle into one integrated assembly....

to the wheels.

#### Front-engine, rear-wheel drive

In front-engined, rear-drive vehicles, a longer drive shaft is also required to send power the length of the vehicle. Two forms dominate: The torque tube
Torque tube
A torque tube system is a driveshaft technology, often used in automobiles with a front engine and rear drive. It is not as widespread as the Hotchkiss drive, but is still occasionally used to this day...

with a single universal joint
Universal joint
A universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion...

and the more common Hotchkiss drive
Hotchkiss drive
The Hotchkiss drive is a system of power transmission. It was the dominant form of power transmission for front-engine, rear-wheel drive layout cars in the 20th century...

with two or more joints. This system became known as Système Panhard after the automobile company Panhard et Levassor
Panhard
Panhard is currently a French manufacturer of light tactical and military vehicles. Its current incarnation was formed by the acquisition of Panhard by Auverland in 2005. Panhard had been under Citroën ownership, then PSA , for 40 years...

patented it.

Most of these vehicles have a clutch and gearbox (or transmission) mounted directly on the engine with a drive shaft leading to a final drive in the rear axle. When the vehicle is stationary, the drive shaft does not rotate. A few, mostly sports, cars seeking improved weight balance between front and rear, and most commonly Alfa Romeo
Alfa Romeo Alfetta
Alfa Romeo GTV redirects here. For 916 series GTV see Alfa Romeo GTV & SpiderThe Alfa Romeo Alfetta is an Italian rear-wheel drive executive saloon car and fastback coupé produced from 1972 until 1987 by Alfa Romeo...

s or Porsche 924
Porsche 924
The Porsche 924 is an automobile produced by Porsche AG of Germany from 1976 to 1988. A two-door, 2+2 coupé, the 924 replaced the 914 as the company's entry-level model, and was the model that finally retired the 912. In production terms, the 924 was the first Porsche model powered by a...

s, have instead used a rear-mounted transaxle
Transaxle
In the automotive field, a transaxle is a major mechanical component that combines the functionality of the transmission, the differential, and associated components of the driven axle into one integrated assembly....

. This places the clutch and transmission at the rear of the car and the drive shaft between them and the engine. In this case the drive shaft rotates continuously as long as the engine does, even when the car is stationary and out of gear.

Early automobiles often used chain drive
Chain drive
Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles...

or belt drive mechanisms rather than a drive shaft. Some used electrical generators and motors to transmit power to the wheels.

#### Front-wheel drive

In British English, the term "drive shaft" is restricted to a transverse shaft that transmits power to the wheels, especially the front wheels. A drive shaft connecting the gearbox to a rear differential is called a propeller shaft, or prop-shaft. A prop-shaft assembly consists of a propeller shaft, a slip joint
Slip joint
A slip joint is a mechanical construction allowing extension and compression in a linear structure.-General forms:Slip joints can be designed to allow continuous relative motion of two components or it can allow an adjustment from one temporarily fixed position to another. Examples of the latter...

and one or more universal joint
Universal joint
A universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion...

s. Where the engine and axles are separated from each other, as on four-wheel drive
Four-wheel drive
Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

and rear-wheel drive vehicles, it is the propeller shaft that serves to transmit the drive force generated by the engine to the axles.

A drive shaft connecting a rear differential to a rear wheel may be called a half shaft. The name derives from the fact that two such shafts are required to form one rear axle.

Several different types of drive shaft are used in the automotive industry:
• One-piece drive shaft
• Two-piece drive shaft
• Slip-in-tube drive shaft

The slip-in-tube drive shaft is a new type that also helps in crash energy management. It can be compressed in the event of a crash, so is also known as a collapsible drive shaft.

#### Four wheel and all-wheel drive

These evolved from the front-engine rear-wheel drive layout. A new form of transmission called the transfer case was placed between transmission and final drives in both axles. This split the drive to the two axles and may also have included reduction gears, a dog clutch or differential. At least two drive shafts were used, one from the transfer case to each axle. In some larger vehicles, the transfer box was centrally mounted and was itself driven by a short drive shaft. In vehicles the size of a Land Rover
Land Rover
Land Rover is a British car manufacturer with its headquarters in Gaydon, Warwickshire, United Kingdom which specialises in four-wheel-drive vehicles. It is owned by the Indian company Tata Motors, forming part of their Jaguar Land Rover group...

, the drive shaft to the front axle is noticeably shorter and more steeply articulated than the rear shaft, making it a more difficult engineering problem to build a reliable drive shaft, and which may involve a more sophisticated form of universal joint.

Modern light cars with all-wheel drive (notably Audi
Audi
Audi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....

or the Fiat Panda
Fiat Panda
The Fiat Panda is a city car from the Italian automobile manufacturer Fiat. The first Fiat Panda was introduced in 1980, and was produced until 2003 with only a few changes. It is now sometimes referred to as the "old Panda". The second model, launched in 2003, is sometimes referred to "New Panda"...

) may use a system that more closely resembles a front-wheel drive layout. The transmission and final drive for the front axle are combined into one housing alongside the engine, and a single drive shaft runs the length of the car to the rear axle. This is a favoured design where the torque is biased to the front wheels to give car-like handling, or where the maker wishes to produce both four-wheel drive and front-wheel drive cars with many shared components.

### Drive shaft for Research and Development (R&D)

The automotive industry also uses drive shafts at testing plants.
At an engine test stand
Engine test stand
An engine test stand is a facility used to develop, characterize and test engines. The facility, often offered as a product to automotive OEMs, allows engine operation in different operating regimes and offers measurement of several physical variables associated with the engine operation.A...

a drive shaft is used to transfer a certain speed / torque from the Internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

to a dynamometer
Dynamometer
A dynamometer or "dyno" for short, is a device for measuring force, moment of force , or power. For example, the power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed .A dynamometer can also be used to determine...

.
A "shaft guard" is used at a shaft connection to protect against contact with the drive shaft and
for detection of a shaft failure.
At a transmission test stand a drive shaft connects the prime mover with the transmission.

## Motorcycle drive shafts

Drive shafts have been used on motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

s almost as long as there have been motorcycles. As an alternative to chain
Chain drive
Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles...

and belt
Belt (mechanical)
A belt is a loop of flexible material used to link two or more rotating shafts mechanically. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys. In a two pulley system, the belt can either drive the pulleys in the...

drives, drive shafts offer relatively maintenance-free operation and long life. A disadvantage of shaft drive on a motorcycle is that gear
Gear
A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

ing or a Hobson's joint or similar is needed to turn the power 90° from the shaft to the rear wheel, losing some power in the process. On the other hand, it is easier to protect the shaft linkages and drive gears from dust, sand and mud.

The best known motorcycle manufacturer to use shaft drive for a long time—since 1923—is BMW
BMW motorcycles
BMW's motorcycle history began in 1921 when the company commenced manufacturing engines for other companies. Motorcycle manufacturing now operates under the BMW Motorrad brand...

. Among contemporary manufacturers, Moto Guzzi
Moto Guzzi
Moto Guzzi is an Italian motorcycle manufacturer. It is one of seven brands owned by Piaggio.Established in 1921 in Mandello del Lario, Italy, the company is noted for its central historic role in Italy's motorcycling manufacture, its prominence worldwide in motorcycle racing, and a series of...

is also well-known for its shaft drive motorcycles. The British company, Triumph
Triumph Motorcycles Ltd
Triumph Motorcycles Ltd is the largest surviving British motorcycle manufacturer, which was established in 1984 by John Bloor after the original manufacturer Triumph Engineering went into receivership...

and all four Japanese brands, Honda
Honda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...

, Suzuki
Suzuki
is a Japanese multinational corporation headquartered in Hamamatsu, Japan that specializes in manufacturing compact automobiles and 4x4 vehicles, a full range of motorcycles, all-terrain vehicles , outboard marine engines, wheelchairs and a variety of other small internal combustion engines...

, Kawasaki
Kawasaki Motorcycle Corporation
Kawasaki motorycles are manufactured by the Motorcycle & Engine division of Kawasaki Heavy Industries at plants in Japan, USA, Philippines, Indonesia and Thailand. The motorcycles have been produced since 1954.-History:...

and Yamaha
Yamaha Motor Company
, is a Japanese motorized vehicle-producing company. Yamaha Motor is part of Yamaha Corporation and its headquarter is located in Iwata, Shizuoka. Along with expanding Yamaha Corporation into the world's biggest piano maker, then Yamaha CEO Genichi Kawakami took Yamaha into the field of motorized...

, have produced shaft drive motorcycles. All geared models of the Vespa
Vespa
Vespa is an Italian brand of scooter manufactured by Piaggio. The name means wasp in Italian.The Vespa has evolved from a single model motor scooter manufactured in 1946 by Piaggio & Co. S.p.A...

scooter produced to date have been shaft-driven. The automatic models, however, use a belt.

Motorcycle engines positioned such that the crankshaft is longitudinal and parallel to the frame
Flat-twin
A flat-twin is a two cylinder internal combustion engine with the cylinders arranged on opposite sides of the crankshaft. It is part of the class of flat engines, sub-type "boxer", and shares most characteristics of those engines.-Motorcycle use:...

are often used for shaft driven motorcycles. This requires only one 90° turn in power transmission, rather than two. Bikes from Moto Guzzi and BMW, plus the Triumph Rocket III
Triumph Rocket III
The Triumph Rocket III is a British three cylinder motorcycle made by the Hinckley Triumph factory and has the largest displacement engine of any mass production motorcycle , at ....

and Honda ST series
Honda ST series
The Honda ST series, also known as the Pan-European in some markets, fills the gap between touring-oriented sport motorcycles such as the CBR1000F and full-dress tourers such as the Honda Goldwing....

all use this engine layout.

Motorcycles with shaft drive are subject to shaft effect
Shaft effect
The shaft effect, also known as elevator effect or shaft jacking, is a phenomenon occurring in shaft-drive motorcycles. This effect occurs because the acceleration being applied to the rear wheel creates a reactive force on the drive shaft. This in turn lifts the rider and the body of the bike,...

where the chassis climbs when power is applied. This is counteracted with systems such as BMW's Paralever, Moto Guzzi's CARC and Kawasaki's Tetra Lever
Kawasaki 1400GTR
The Kawasaki 1400GTR, also known as the Concours 14 or ZG1400 in some markets, is a motorcycle produced by Kawasaki. The 1400GTR was introduced in September 2007 and is based on the ZX-14 platform....

.

## Marine drive shafts

On a power-driven ship, the drive shaft, or propeller shaft, usually connects the transmission inside the vessel directly to the propeller
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...

, passing through a stuffing box
Stuffing box
A stuffing box is an assembly which is used to house a gland seal. It is used to prevent leakage of fluid, such as water or steam, between sliding or turning parts of machine elements.-Boats:...

or other seal at the point it exits the hull
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

. There is also a thrust block
Thrust block
A thrust block, also known as a thrust box, is a specialised form of thrust bearing used in ships, to resist the thrust of the propellor shaft and transmit it to the hull.- Early thrust boxes :...

, a bearing to resist the axial force of the propeller. As the rotating propeller pushes the vessel forward, any length of drive shaft between propeller and thrust block is subject to compression, and when going astern to tension
Tension (mechanics)
In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...

. Except for the very smallest of boats, this force isn't taken on the gearbox or engine directly.

Cardan shafts are also often used in marine applications between the transmission and either a propeller gearbox or waterjet.

## Locomotive drive shafts

The Shay
Shay locomotive
The Shay locomotive was the most widely used geared steam locomotive. The locomotives were built to the patents of Ephraim Shay, who has been credited with the popularization of the concept of a geared steam locomotive...

, Climax
Climax locomotive
A Climax locomotive is a type of geared steam locomotive in which the two steam cylinders were attached to a transmission located under the center of the boiler. This transmits power to driveshafts running to the front and rear trucks....

and Heisler
Heisler locomotive
The Heisler locomotive was the last variant of the three major types of geared steam locomotive, Charles L. Heisler receiving a patent for the design in 1892 following the construction of a prototype in 1891. Somewhat similar to a Climax locomotive, Heisler's design featured two cylinders canted...

locomotives, all introduced in the late 19th century, used quill drive
Quill drive
A quill drive is a mechanism that allows a drive shaft to shift its position relative to its driving shaft. It consists of a hollow driving shaft with a driven shaft inside it...

s to couple power from a centrally mounted multi-cylinder engine to each of the trucks
Bogie
A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

supporting the engine. On each of these geared steam locomotive
Geared steam locomotive
A geared steam locomotive is a type of steam locomotive which uses reduction gearing in the drivetrain, as opposed to the common directly driven design....

s, one end of each drive shaft was coupled to the driven truck through a universal joint
Universal joint
A universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion...

Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

, transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

or another truck through a second universal joint. A quill drive also has the ability to slide lengthways, effectively varying its length. This is required to allow the bogies to rotate when passing a curve.

Cardan shafts are used in some diesel locomotive
Diesel locomotive
A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

s (mainly diesel-hydraulics, such as British Rail Class 52
British Rail Class 52
British Rail assigned Class 52 to the class of 74 large Type 4 diesel-hydraulic locomotives built for the Western Region of British Railways between 1961 and 1964...

) and some electric locomotive
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

s (e.g. British Rail Class 91
British Rail Class 91
The British Rail Class 91 is a class of , electric locomotives ordered as a component of the East Coast Main Line modernisation and electrification programme of the late 1980s. The Class 91s were given the auxiliary name of InterCity 225 to indicate their envisaged top speed of...

). They are also widely used in diesel multiple unit
Diesel multiple unit
A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...

s.

## Drive shafts in bicycles

The drive shaft has served as an alternative to a chain-drive in bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

s for the past century, although never becoming very popular. A shaft-driven bicycle
Shaft-driven bicycle
A shaft-driven bicycle is a bicycle that uses a drive shaft instead of a chain to transmit power from the pedals to the wheel. Shaft drives were introduced over a century ago, but were mostly supplanted by chain-driven bicycles due to the gear ranges possible with sprockets and derailleurs...

is described as an "Acatane", from one of their early makers. When used on a bicycle, a drive shaft has several advantages and disadvantages:

• Drive system is less likely to become jammed, a common problem with chain-driven bicycles
• The rider cannot become dirtied from chain grease or injured by the chain from "Chain bite", which occurs when clothing or even a body part catches between the chain and a sprocket
• Lower maintenance than a chain system when the drive shaft is enclosed in a tube
• More consistent performance. Dynamic Bicycles claims that a drive shaft bicycle can deliver 94% efficiency, whereas a chain-driven bike can deliver anywhere from 75-97% efficiency based on condition
• Greater clearance: with the absence of a derailleur
Derailleur gears
Derailleur gears are a variable-ratio transmission system commonly used on bicycles, consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another...

or other low-hanging machinery, the bicycle has nearly twice the ground clearance

• A drive shaft system weighs more than a chain system, usually 1-2 pounds
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

heavier
• Many of the advantages claimed by drive shaft's proponents can be achieved on a chain-driven bicycle, such as covering the chain and gears with a metal or plastic cover
• Use of lightweight derailleur gears with a high number of ratios is impossible, although hub gears can be used
• Wheel removal can be complicated in some designs (as it is for some chain-driven bicycles with hub gears).