Motorcycle frame
Encyclopedia
A motorcycle frame includes the head tube
that holds the front fork
and allows it to pivot. Some motorcycles include the engine as a load-bearing, stressed member. The rear suspension
is an integral component in the design. Traditionally frames have been steel
, but titanium
, aluminium
, magnesium
, and carbon-fibre, along with composites of these materials, have been used. Because of different motorcycles' varying needs of cost, complexity, weight distribution
, stiffness, power output and speed, there is no single ideal frame design.
Examples
single spine and single downtube.
Examples
Examples
Examples
Examples
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.
Examples
Instead, if the engine is rigidly mounted to the frame, vibrations pass to and are dissipated via the whole frame, and the rider. Rigid mounting allows the engine to contribute to the overall stiffness of the frame. It also becomes possible to mount the swingarm directly to the engine rather than the frame, avoiding the need for frame members extending downward to the swingarm pivot. By increasing the number of mounting points between the engine and frame, vibrations and stress can be better dissipated in the frame, typically creating a triangle between the swingarm in the rear, the cylinder head at the top and the lower crankcase area at the front. If a rigidly mounted engine not only contributes to, but is critical to, the stiffness of the frame, and is an integral part of closing the triangle or trellis structure that transfers force from the headstock to the swingarm, to the point that without the engine the frame would be deformed, the engine is called a stressed member, or a lifted engine. Sharing the load between the engine and frame reduces the overall weight of the motorcycle.
During early testing of the 1983 Kawasaki GPZ900R
, twin downtubes were included, creating a full cradle, but the downtubes were found to carry little load, so they were removed, relying entirely on the combination of the steel backbone and engine for chassis rigidity. BMW
's R1100 series twins of 1994 relieved the frame of stress entirely, with the engine carrying the total load from the front Telever fork to the rear Monolever.
Head tube
Most bicycles, tricycles and motorcycles have a tubular frame. The front fork pivots within the head tube . On a motorcycle, the "head tube" is normally called the steering head...
that holds the front fork
Motorcycle fork
A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a pair of triple clamps. It typically incorporates the front suspension and front brake, and allows the bike to be steered via handlebars attached to the top clamp....
and allows it to pivot. Some motorcycles include the engine as a load-bearing, stressed member. The rear suspension
Suspension (vehicle)
Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...
is an integral component in the design. Traditionally frames have been steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, but titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
, aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, and carbon-fibre, along with composites of these materials, have been used. Because of different motorcycles' varying needs of cost, complexity, weight distribution
Weight distribution
Weight distribution is the apportioning of weight within a vehicle, especially cars, airplanes, and trains.In a vehicle which relies on gravity in some way, weight distribution directly affects a variety of vehicle characteristics, including handling, acceleration, traction, and component life...
, stiffness, power output and speed, there is no single ideal frame design.
Steel
Examples- Norton Featherbed frameFeatherbed frameThe featherbed frame was a motorcycle frame developed by the British Norton motorcycle company to improve the performance of their racing motorcycles around the twisting and demanding Isle of Man TT course in 1950. It was considered revolutionary at the time, and the best handling frame that a...
- Early Honda CBR600
Aluminium and carbon-fibre
Examples- Bimota SB8KBiMoTa SB8KThe SB8K is a sportbike made by Italian motorcycle manufacturer Bimota.The bike was added to the present lineup after the company hiatus in late nineties financial crisis. The bike was built with a profusion of light alloys and carbon fiber; the materials employed in the construction of the chassis...
(composed of two aluminium alloy beams and carbon fibre plates)
Titanium
Examples- 1971 Titanium HusqvarnaHusqvarna MotorcyclesHusqvarna Motorcycles, a subsidiary of BMW, is a company manufacturing motocross, enduro and supermoto motorcycles. The company began producing motorcycles in 1903 at Huskvarna, Sweden, as a branch of the Husqvarna armament firm which had supplied the Swedish army with rifles since 1689.-History:As...
Inter-AMAAmerican Motorcyclist AssociationThe American Motorcyclist Association is an American not-for-profit organization of more than 300,000 motorcyclists that organizes numerous motorcycling activities and campaigns for motorcyclists' legal rights...
MotocrossMotocrossMotocross is a form of motorcycle sport or all-terrain vehicle racing held on enclosed off road circuits. It evolved from trials, and was called scrambles, and later motocross, combining the French moto with cross-country...
Magnesium
Examples- 19881988 Grand Prix motorcycle racing seasonThe 1988 Grand Prix motorcycle racing season was the 40th F.I.M. Road Racing World Championship season.-Season summary:Eddie Lawson would recapture the championship from Wayne Gardner in a season that witnessed several fierce duels. Two newcomers joined the Grand Prix circuit with Americans Wayne...
Elf ROCElf AquitaineElf Aquitaine was a French oil company which merged with TotalFina to form TotalFinaElf. The new company changed its name to Total in 2003...
-HondaHondais 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...
Elf5-NSR500Honda NSR500thumb|right|Shinichi Itoh, riding his Honda NSR500 in the Japanese Grand Prix 1993The Honda NSR500 is a race motorcycle from the Honda NSR series. It was created by HRC and debuted in 1984 for the Grand Prix motorcycle racing's 500 cc class. Honda won ten 500cc World Championships with the...
500 cc Grand PrixGrand Prix motorcycle racingRoad Racing World Championship Grand Prix is the premier championship of motorcycle road racing currently divided into three distinct classes: 125cc, Moto2 and MotoGP. The 125cc class uses a two-stroke engine while Moto2 and MotoGP use four-stroke engines. In 2010 the 250cc two-stroke was replaced...
Magnesium and aluminium
Examples- MV Agusta F4 750 Serie Oro
Pressed frame
The frame is mass-produced by sheet metal pressed or stamped into shape. Typically a single-cradle structure is used.Examples
- Honda Super Cub
- Ducati 65TDucati 65TThe Ducati 65T, and the 65TL luxury version, were motorcycles manufactured by Ducati Meccanica S.p.A, from 1952 to 1958, coming out in the same year as the 98. The 65TS appeared in 1955, ten pounds lighter, with a different gas tank, lower handlebars and dual seat.In 1958, the 65T sold in London...
Half-duplex cradle frame
The motorcycle engine is held in a double cradle with asingle spine and single downtube.
Examples
- Suzuki GSX250
- Suzuki TS50ERSuzuki TS50ERThe Suzuki TS50ER was a 49cc single cylinder motorcycle which sold during 1980 - 1983.- Popularity :The TS50ER was extremely popular with 16 year olds and young adults as its simplicity to ride and un-restricted potential power gave many the chance to explore the world of motorcycling...
Full duplex cradle frame
The motorcycle engine is held in a full by two separate cradles, normally with a single spine.Examples
- Norton ManxNorton ManxThe Norton Manx or Manx Norton is a British racing motorcycle that was made from 1947 to 1962 by Norton Motors Ltd. A Norton had contested every Isle of Man TT race from the inaugural 1907 event through into the 1970s, a feat unrivalled by any other manufacturer, and the development and honing of...
- Suzuki TS50XSuzuki TS50XThe Suzuki TS50X was an enduro motorcycle that was first produced in 1984 and was discontinued in 2002.-Specifications:It has a Stock 5-speed aircooled TSX engine with around 2,9 horsepowers. The Suzuki RMX/SMX has almost the same engine but it has 6-gears and is watercooled. The TSX frame is the...
Double cradle or perimeter frame
Two cradles follow the perimeterExamples
- Early Suzuki GSX-R750Suzuki GSX-R750The GSX-R750 is a 750 class sport bike motorcycle from Suzuki's GSX-R series of motorcycles. It was introduced in 1985 and can be considered to be the first of the modern racer-replicas with many race-derived technologies and the looks of a Suzuki Endurance racer at an affordable price.-Air-cooled...
, - Suzuki GSX-R1100Suzuki GSX-R1100The GSX-R1100 was a sport bike from Suzuki's GSX-R series of motorcycles. It was introduced in 1986.-Background:In the mid 1970s the motorcycle industry was in a period of transition...
- Suzuki RG250Suzuki RG250The Suzuki RG250 was a two cylinder, 250cc two-stroke road motorcycle. First released in 1978 with the rg125 and rg250 to replace the popular gt125 and gt185. The Rg250 was a completely new bike when compare to the gt series....
Spine or backbone frame
The motorcycle engine is suspended from a single spine.Examples
- Honda CB92 Benly
- Kawasaki Z1000Kawasaki Z1000The Kawasaki Z1000 is a four-cylinder motorcycle in the streetfighter or standard style.-History:Kawasaki introduced the Z1 motorcycle in 1972. Four years later they introduced the Kz900. The original Kawasaki Z1 was the first series of Japanese motorcycles with the combination of four cylinders,...
Beam
Twin beams join headstock to swingarm pivot in as straight and short a line as possible.Examples
- 1885 Daimler ReitwagenDaimler ReitwagenThe Daimler Reitwagen or Einspur was a motor vehicle made by Gottlieb Daimler and Wilhelm Maybach in 1885, and is widely recognized as the first motorcycle. Daimler is often called "the father of the motorcycle" for this invention...
- Honda VFR750Honda VFR750The Honda VFR750F is a sport touring motorcycle produced between 1986 and 1997. The fully faired motorcycle featured a reliable 98 horsepower liquid-cooled double overhead cam V4 four-stroke engine. All generations of VFR750 since 1990 employ an ELF-designed single-sided rear swingarm...
- Yamaha FZR600Yamaha FZR600The Yamaha FZR600 is a sports motorcycle produced by Yamaha between 1989 and 1999. It was the successor to the FZ600 and was replaced by the YZF-600R...
Monocoque
Supports structural load using the external skin of the frame.Examples
- 1944 Piaggio MP5
- Honda NR500Honda NR500NR500 was an innovative racing motorcycle developed by Honda HRC in 1979 to compete in Grand Prix motorcycle racing. The NR stood for New Racing....
- 2008 Kawasaki Ninja ZX-14Kawasaki Ninja ZX-14The ZZR1400 is a motorcycle made by Kawasaki and is currently their most powerful sport bike. It was introduced at the Tokyo 2005 show and released for the 2006 model year as a replacement for the ZX-12R. The ZZR1400 is capable of accelerating from 0–60 mph in 2.5 seconds...
Trellis
Similar to the beam frame, connecting the steering head and swingarm pivot point directly as possible. The frame is made up of a large number of short steel (or aluminium) tubes welded together to form a trellisLattice girder
A lattice girder is a girder where the flanges are connected by a lattice web. This type of design has been supplanted in modern construction with welded or bolted plate girders, which use more material but have lower fabrication and maintenance costs...
.
Examples
- Most modern Ducatis
- Suzuki SV650Suzuki SV650The SV650 and variants are street motorcycles manufactured since 1999 for the international market by the Suzuki Motor Corporation, featuring a mid-sized V-twin engine and medium performance components...
- Kawasaki VersysKawasaki VersysThe Kawasaki Versys, also known as the KLE650 is a middleweight motorcycle with a standard riding posture, introduced by Kawasaki to the European and Canadian markets at the end of 2006, and to the US market in 2007...
- Honda VTR250Honda VTR250The Honda VTR250 is a 90° V-twin motorcycle produced by Honda that has so far had one major revision. The original VTR250 was a faired model sold only in the USA and Canada from 1988 to 1990...
Engine as a stressed member
For rider comfort, a motorcycle's engine can be mounted on rubber bushings to isolate vibration from the rest of the machine. This strategy means the engine contributes little to frame stiffness, and absorbing rather than dissipating vibration can lead to stress damage to the frame, exhaust pipes, and other parts.Instead, if the engine is rigidly mounted to the frame, vibrations pass to and are dissipated via the whole frame, and the rider. Rigid mounting allows the engine to contribute to the overall stiffness of the frame. It also becomes possible to mount the swingarm directly to the engine rather than the frame, avoiding the need for frame members extending downward to the swingarm pivot. By increasing the number of mounting points between the engine and frame, vibrations and stress can be better dissipated in the frame, typically creating a triangle between the swingarm in the rear, the cylinder head at the top and the lower crankcase area at the front. If a rigidly mounted engine not only contributes to, but is critical to, the stiffness of the frame, and is an integral part of closing the triangle or trellis structure that transfers force from the headstock to the swingarm, to the point that without the engine the frame would be deformed, the engine is called a stressed member, or a lifted engine. Sharing the load between the engine and frame reduces the overall weight of the motorcycle.
During early testing of the 1983 Kawasaki GPZ900R
Kawasaki GPZ900R
The Kawasaki GPZ900R was a sport bike manufactured from 1984 to 2003. The 1984 GPZ900R was a revolutionary design that became the immediate predecessor of the modern-day sport bike. Developed in secret over six years, it was the world's first 16-valve liquid-cooled inline four-cylinder motorcycle...
, twin downtubes were included, creating a full cradle, but the downtubes were found to carry little load, so they were removed, relying entirely on the combination of the steel backbone and engine for chassis rigidity. BMW
BMW Motorrad
BMW Motorrad is the motorcycle brand of the German company BMW, part of its Corporate and Brand Development division. The current General Director of the unit is Hendrik von Kuenheim....
's R1100 series twins of 1994 relieved the frame of stress entirely, with the engine carrying the total load from the front Telever fork to the rear Monolever.