What is a Motorcycle Chassis?
A motorcycle chassis is also known as the frame of the motorcycle. Its primary function is serving as the skeleton of the motorcycle onto which all other parts and components are attached and fitted.
Due to this skeletal function, the motorcycle chassis is typically made using materials that are highly resistant to tensile or torsional forces. Accordingly, steel and iron are the most common candidates for the constitution of the motorcycle chassis.
The chassis is composed of a series of metal plates, slats, and bars that serve as fulcrums for most of the components that make up a motorcycle. Since the chassis runs all the way through the motorcycle's length, all the various elements along the chassis can be fitted for optimum safety and engineering efficiency.
The motorcycle chassis accommodates the propulsion, suspension, power elements, wheels, and brakes, similar to how the human skeleton accommodates the muscles. Due to the undeniable importance of a motorcycle chassis, these structures have been consistently transforming overtime before arriving at the latest generation of shapes, designs, and angles.
What Components is a Motorcycle Made of?
Below are brief descriptions of all the components of a motorcycle. Note that the following list also covers most, if not all, of the parts of a motorcycle.
The motorcycle frame provides the vehicle with the structure onto which all other components are mounted and fitted. The frame comprises hollow tubes, usually composed of steel, aluminum, or an alloy of the two. The frame is also essential to keep the wheels in line during riding, thereby helping to maintain the overall handling of the motorcycle.
The frame supports the suspension system of a motorcycle. The suspension system is a series of springs and shock absorbers and helps maintain contact between the wheels and the road and cushion both the vehicle and the rider during bumps and jolts.
Motorcycle wheels are typically composed of steel or aluminum rims, although several models introduced in the 1970s and after offer cast wheels. Cast wheels have become more common since they allow for the use of tubeless tires, which do not have an internal tube to hold the compressed air like pneumatic tires do.
In cast wheels, the air is held between the tire and the rim, and the internal air pressure is maintained by a seal between these two components. Although the probability of a tubeless tire blowing out is low, they can create problems when ridden on rough roads as even a tiny bend in the rim will compromise the seal and cause deflation.
Notably, motorcycle tires are designed in different ways depending on the type of motorcycle and the road and terrain conditions on which it will most likely be ridden. For example, dirt bike tires have a treaded surface to provide maximum grip, while touring bike tires are made of very hard rubber that lasts longer but provides less grip.
Both the front and rear wheels of a motorcycle have a brake fitted onto them. The front brake uses a handgrip on the ride-side handlebar while the rear brake is activated using the right-side foot pedal. Today, most motorcycle brakes are disc brakes, which are superior in performance to the formerly used drum brakes.
Disc brakes are composed of a steel braking disc sandwiched between the brake pads and connected to the wheel. When the rider activates the brakes on their motorcycle, hydraulic pressure builds up in the fluid within the brake line, causing the brake pads to squeeze against either side of the disc.
The friction generated by squeezing the brake pads on both sides of the brake disc causes the wheel to slow down or stop completely.
Located on the top-side of the motorcycle frame and mounted just behind the gas tank, motorcycles seats are designed to carry one to two passengers. Usually, motorcycles seats can easily be removed from the frame.
Typically, motorcycle seats are made using a synthetic substance, usually polyurethane. Many motorcycle seats have compartments underneath or behind them for carrying cargo.
A carburetor is a mechanical device that forms part of the motorcycle's internal combustion engine. The function of the carburetor is to provide fuel to the combustion chamber to create an explosion and release energy, which is used to move the engine's pistons.
Carburetors mix air with raw fuel to produce a highly combustible blend of fuel, which is more volatile than raw fuel. A vacuum is created by the downward stroke of the engine's pistons, which pulls the fuel mixture into the cylinder walls. Another process initiates a properly timed spark, igniting the fuel, causing a controlled explosion that forces the piston downward and produces power to turn the wheels.
The transmission system of a motorcycle is composed of various parts, including a clutch, steel ball flyweights, metal plates, a crankshaft, gears, pulleys, and either rubber belts or metal chains.
The gears that make up a transmission system are known as a gear-set, enabling the rider to go from a complete stop to cruising speed. Most motorcycle transmission systems have four to six gears, which are engaged by shifting a lever that adjusts forks within the transmission system.
The clutch is another important part of a transmission system as its job is to engage and disengage power from the crankshaft, which rotates with the engine, to the transmission system. The clutch essentially allows the wheels to stop turning with the engine for a second without switching off the engine, which would be highly impractical.
The clutch comprises a series of spring-loaded plates that are pressed together to connect the transmission to the crankshaft. Upon shifting gears, the clutch is used to disengage the transmission from the crankshaft, allowing the gear to be smoothly shifted while the engine is still running. Once the vehicle has been shifted into the desired gear, the clutch is used to re-establish the connection between the crankshaft and the transmission.
The rest of a motorcycle's transmission system components are contained within the drive system. The drive system is composed of either a chain, belt, or shaft, which transfers power from the engine to the motorcycle's rear wheel.
The most common type of drive system uses a chain, where a sprocket is mounted on the output/transmission shaft and is connected via a metal chain to a sprocket mounted on the rear wheel. The transmission system turns the smaller front sprocket, which transmits power to the rear sprocket along the chain and turns the rear wheel.
The power system or electrical system of a motorcycle consists of several parts and can be divided into a number of separate circuits. The following circuits must be part of a motorcycle if it is to be approved for road use.
- Charging Circuit – Supplies the battery with power via the voltage regulator and alternator
- Ignition Circuit – Supplies the ignition unit with power using spark plugs and ignition coils
- Lighting Circuit – Supplies power to the headlight and taillight
- Other Electrical Circuits - Supply power for the brake light, turn signals, horn, and warning lights
A motorcycle's power system is also composed of the charging system, which is made up of an alternator, a battery, and a regulator/rectifier. Below are the functions of each of these components of a motorcycle charging system.
- Alternator – Creates alternating currents used to charge the battery
- Battery – Stores electrical energy and acts as a buffer for the motorcycle's power system
- Regulator/Rectifier – Rectifies the alternating current generated by the alternator into direct current so that the battery can store it. The regulator also regulates the amount of current generated to prevent overcharging
Raw Materials of a Motorcycle
To this day, motorcycles are still manufactured using mostly steel and aluminum. Aluminum is a highly valued metal for motorcycle manufacturing due to its lightweight, high tensile strength, and non-corrosive properties. Meanwhile, steel is highly valued for its strength and durability, despite being heavier than aluminum.
Due to the specific properties of both steel and aluminum, these raw materials are typically the go-to metals for motorcycle manufacturing. They are also used to manufacture gas tanks, handlebars, forks, and wheels.
The steel or aluminum parts of a motorcycle can be manufactured using three distinct processes. Metal parts can be billeted using a CNC machine, cast using a mold, or forged using a combination of heat and hammering.
Depending on the function of the part, the type of metal used, and the design of the part, any of these three processes can be used to manufacture metal parts for a motorcycle from steel or aluminum.
How is a Motorcycle Manufactured?
The manufacturing of a motorcycle consists of a series of steps that can be described as follows:
- Raw materials arrive at the manufacturing plant by rail or truck. These parts are typically delivered on a daily basis and arrive at the same location where they are to be installed.
- The manufacturing process begins in the welding department, where high-strength frame materials are used to fabricate the motorcycle frame via computer-controlled welding. The various components of the frame are fashioned out of tubular or hollow metal shells made using sheet metal. The various sections are welded together using a combination of manual, automatic, and robotic processes.
- In a process known as injection molding, small plastic resin pellets are melted before being injected into molds under high pressure, thereby forming plastic body trim parts. This process takes place in the plastic department of the manufacturing plant.
- In the paint department, a process known as powder-coating is used to paint the motorcycle's various plastic and metal parts. The apparatus used to paint these parts functions like a large spray-painter, using a pressurized system to disperse paint evenly.
- Painted motorcycle components are sent through overhead conveyors to the assembly department, where they are fitted and installed on the motorcycle frame.
- As the motorcycle is sent down the assembly line, the engine is mounted onto the frame along with other components.
- The last step in the motorcycle manufacturing process involves fitting and installing the brakes, wheels, footpegs, wiring cables, seat, exhaust pipe, lights, saddlebags, radio, and several other parts.
Motorcycle Quality Control
The last part of motorcycle manufacturing is quality control. This is where inspectors undertake a visual and tactile inspection of how well the parts have been fitted and painted. After this, the proper functioning of each motorcycle is inspected using a dynamometer, which accelerates the motorcycle from 0 to 60mph.
The motorcycle is inspected during the dynamometer tests to ensure proper braking, shifting, wheel alignment, and acceleration. Headlight and taillight alignment and function, exhaust function, and horn function are also inspected during this stage.
Once the inspectors have concluded that the motorcycle meets international standards for safety and performance, the inspection is complete, and the motorcycle is boxed and prepared for shipment.
About THE AUTHOR
Russ currently owns a Yamaha FZ6N and KTM RC 390. When it comes to vintage bikes, his favorite motorcycle is the feisty BMW R32. He also holds a particular interest in the LAMS segment and triple cylinders. Himself a riding enthusiast, Russ has had experience with racetracks from around the world including Willow Springs Raceway in California and the Imola Circuit in Italy.Read More About Russ Crowley