Figure 1: Visual comparison . Steppers (Left) are dense and simple. Servos (Right) are longer and include a visible feedback encoder housing on the rear. The Million Dollar Question: "Which Motor Do I Need?" If you are designing a CNC machine, a packaging robot, or a conveyor system, you face the same dilemma every time: Stepper or Servo? Make the wrong choice, and you face two disasters: The Stepper Trap: Your machine "loses steps" (positional error) without knowing it, scrapping parts. The Servo Trap: You spend $5,000 on a system that could have been done for $500, blowing your budget. This guide bridges the gap between mechanical requirements and electrical reality. 1. The Stepper Motor: The "Digital Ratchet" Think of a Stepper Motor like a very strong, magnetic ratchet. It divides a full rotation into equal steps (typically 200 steps per revolution, or 1.8°). Pros: Incredible Holding Torque: Ste...
A flywheel is a mechanical device with significant moment of inertia
used to store rotational energy. Flywheels resist changes in rotational speed, helping to steady shaft rotation when a fluctuating torque is applied by its power source, such as a piston-based (reciprocating) engine, or when an intermittent load, such as a piston pump, acts on it.
Flywheels can also produce high-power pulses for experiments, where drawing power from the electrical network would create unacceptable spikes. A small motor can accelerate the flywheel between pulses.
Flywheels may be classified as balance wheels or flywheel pulleys. Their primary purpose is to equalize energy exertion and work done, thus preventing excessive or sudden speed changes. Permissible speed variation is a key factor in all flywheel designs: for example, steam engines may allow only 1–2% variation, whereas punching or shearing machinery may tolerate 20% variation.
Flywheels can also produce high-power pulses for experiments, where drawing power from the electrical network would create unacceptable spikes. A small motor can accelerate the flywheel between pulses.
Flywheels may be classified as balance wheels or flywheel pulleys. Their primary purpose is to equalize energy exertion and work done, thus preventing excessive or sudden speed changes. Permissible speed variation is a key factor in all flywheel designs: for example, steam engines may allow only 1–2% variation, whereas punching or shearing machinery may tolerate 20% variation.
The function of a balance wheel is to absorb and equalize energy when resistance or driving power varies throughout a cycle. The rim is typically heavy, designed for the energy it must store to minimize speed fluctuations while maintaining structural strength. Rims of balance wheels are usually square or nearly square in cross-section. Flywheel pulleys are commonly wide to accommodate a belt and relatively thin radially, though this is not a strict rule.
Flywheels may be solid or sectional. Flywheels up to ~8 ft in diameter are usually cast solid, sometimes with divided hubs to relieve cooling stresses.
Flywheels between 8 and 15 ft diameter are often cast in halves, and larger sizes in multiple sections, often matching the number of arms. Sectional flywheels are generally of two classes:
- Cast wheels formed in sections because solid casting is too large to transport.
- Special sectional wheels designed for higher peripheral speeds using engineered materials and arrangements.
Steel wheels may fall into three types:
- Center and rim entirely of steel plates.
- Cast-iron center with steel rim.
- Cast-steel center with steel rim of steel plates.
Rim joints are critical in sectional designs. Bolted or flanged joints between arms average ~20% of solid-rim strength, with a maximum of ~25%. By placing joints at the arm ends, ~50% efficiency can be achieved, as the joint is directly supported and not subjected to bending between arms. Using steel links shrunk into place can reach ~60% efficiency. Rims with box or I-section links may achieve 100% joint efficiency.
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