What is an Automotive Flywheel?
A flywheel is a rotating mechanical device that is used to store rotational energy and maintain engine speed. It is connected to the crankshaft in almost all gasoline and diesel engines. The main purpose of a flywheel is to maintain a constant rotational speed of the crankshaft. It smoothens out the power strokes of each cylinder and provides inertia to keep the engine running smoothly between power strokes.
Construction of an Automotive Flywheel
Automotive Flywheel typically has the following main components:
- Rim - It is the outer ring or edge of the flywheel which stores rotational energy through its mass and speed of rotation. The rim material is usually cast iron for its density.
- Starter Ring Gear - It is a toothed ring machined into the outer edge of the flywheel. The starter motor meshes with this gear to turn over the engine during starting.
- Flange - It is the flat face of the flywheel that bolts directly to the crankshaft. Precision machining is required for a tight fit between the crankshaft and flywheel flange.
- Bolts - Multiple bolts are used to securely mount the flywheel to the crankshaft flange. Heavy-duty bolts are needed to withstand the torque loads.
Working Principles of Automotive Flywheels
Here are the key working principles of an automotive flywheel:
Storing Kinetic Energy
When the combustion force pushes the pistons down during each power stroke, it rotates the crankshaft. This rotational motion is transmitted to the heavier flywheel due to its attachment to the crankshaft. The flywheel stores this kinetic energy of motion in its rotating mass.
Smoothening Torque Surges
In a four-stroke engine, only one cylinder is on the power stroke at any given moment, with the other cylinders on intake, compression or exhaust strokes. This results in torque pulses from each cylinder. The flywheel's stored rotational energy helps to smooth out these torque surges, delivering a constant torque to keep the engine speed uniform.
Carrying Engine over Dead Centers
At certain points in the crankshaft's rotation, the pistons pass through positions where they are neither moving up nor down, called dead centers. At these instants, the crankshaft experiences minimal driving force from the pistons. The flywheel inertia keeps the crankshaft rotating over these dead centers until the next power stroke.
Keeping Engine Idling
When the engine is idling with no load or throttle, the ignition, fuel injection and combustion events alone may not be enough to continuously rotate the crankshaft. The flywheel carries over this momentum to maintain a steady idling speed without stalling.
Engine Starting Function
During starting, the starter motor engages with the starter ring gear teeth on the flywheel rim. The motor uses electrical current to spin the heavy flywheel, which in turn rotates the crankshaft to start piston movement and ignition.
Key Factors Affecting Flywheel Design & Material
Several factors influence the design and construction of automotive flywheels:
Engine Size & Performance
Larger engine displacements require flywheels with greater mass and inertia to smooth out torque irregularities over a wider rpm range. Conversely, smaller engine flywheels can be compact. Performance-oriented flywheels are lightweight for rev-ability but generate more torque spikes that must be managed.
Material Selection
Common materials are cast iron for its affordability and density, and bimetallic composite designs using cast iron rim bonded to an aluminum hub for reduced weight. More premium engines use metallic composites.
Mounting & Stress Loads
Crankshaft design, transmission configuration and gearing vary engine mounting loads on the flywheel. Bolts must withstand high twisting torque stresses during acceleration and deceleration. Failure analysis tests optimize bolt arrangement.
Starter Ring Gear Teeth Design
Number, size and pitch of teeth are matched to the starter motor gearing for reliable and efficient starting across all operating conditions and service life of the vehicle.
Balancing & Machining Tolerances
Unbalanced flywheels cause unwanted vibrations. Precision machining and balancing techniques ensure smooth, vibration-free operation up to high engine speeds. Tight running tolerances between crankshaft and flywheel are required.
That covers the key aspects of automotive flywheel construction, working principles and factors governing design variations. Flywheels play an important inertia role in maintaining uniform engine operation between power strokes and across different driving conditions and rpm levels. Their robust design is crucial for repeated starter engagement and torque transmission over long vehicle usage.
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Ravina Pandya, Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. (https://www.linkedin.com/in/ravina-pandya-1a3984191)
