A3.3 / Introduction to Mechanical Systems
A3.3 / Introduction to Mechanical Systems
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How are mechanisms present in everyday products?
Mechanical systems are fundamental components of everyday products, designed to convert an input into a specific output. These systems typically follow an input, process, and output model to perform work. One of the primary purposes of a mechanical system is to provide mechanical advantage to the user, which improves product performance in terms of both function and efficiency. Designers utilize these systems to increase or decrease the speed, direction, or power of a movement
3.3.1 - Types of Motion
3.3.1 - Types of Motion
In mechanical systems, there are four primary types of motion that designers must identify and apply:
• Linear: Movement in a straight line.
• Rotary: Movement following a circular path around a central axis.
• Oscillating: A back-and-forth movement along an arc.
• Reciprocating: A repetitive back-and-forth movement in a straight line.
These types of motion can be combined to create either simple or complex mechanical systems by integrating gears, pulleys, cams, levers, and linkages. For instance, a rack and pinion system is frequently used to change the direction of a handle's rotary motion into linear motion, which is particularly useful in tools like jar openers to reduce the significant torque required by the user.
3.3.2 - Key Mechanical Components & Systems
3.3.2 - Key Mechanical Components & Systems
3.3.2.1 - Gear Systems
3.3.2.1 - Gear Systems
Gear Systems
Gear Systems
Gears are used to transmit rotary motion from one shaft to another through interlocking teeth. Common gear systems include:
• Spur, Bevel, and Worm gears.
• Rack and Pinion
• Planetary gears
highly effective for optimising torque and speed
• Ratchet and Pawl, Idler, and Compound gears.
Spur gears
Spur gears
Spur gear systems are most common. They are used to increase or decrease speed or torque giving a mechanical advantage while tranfering rotational motion
Bevel gears
Bevel gears
A variation of spur gears are bevel gears whiuch use a tilted or beveled edge to rotate the motion and force through a set angle.
Most commonly this is done at 90 or 45 degrees but with precision machining bevel gears can achieve any angle.
Worm gears
Worm gears
Similarly, worm gears are used to change the angle or axis of rotation. Worm gears provide the advantage of size, making them useful in smaller mechanisms.
Rack and Pinion
Rack and Pinion
Rack and Pinion mechanisms are used to transfer a rotational motion from a spur gear (Pinion) to a linear motion along the "Rack".
This can also be adapted to create reciprocating motion by customising the gear teeth and meshing sequence.
Planetary gears
Planetary gears
A planetary gear set is a compact gear system consisting of a central "sun" gear, multiple "planet" gears, and an outer "ring" gear that work together to provide high torque density and versatile speed ratios.
They are commonly used in Automatic Transmissions to switch between different gear ratios smoothly and in Heavy Machinery to provide large amounts of torque in a small space
Ratchet gears and Pawls
Ratchet gears and Pawls
A ratchet mechanism consists of a toothed wheel and a pivoting lever called a "pawl" that allows motion in one direction while preventing motion in the reverse.
Idler gears
Idler gears
An Idler gear intermediate gear placed between two other gears to change the direction of rotation or bridge a physical gap without altering the overall gear ratio.
Compound gears
Compound gears
A compound gear consists of two or more gears of different sizes fixed together on the same shaft, rotating at the same speed to allow for significant increases or decreases in torque and speed within a small space.
Digital prototyping:
Digital prototyping:
Gear Generator - This online package can be used as a sandbox to design, prototype, and create downloadable CAD files for Gear systems
In the beta version of Gear Generator 2, you can design more complex systems using planetary gears, pulley and belt systems.
3.3.2.2 - Belt-Driven Systems and Pulleys
3.3.2.2 - Belt-Driven Systems and Pulleys
Belt-Driven Systems and Pulleys
Belt-Driven Systems and Pulleys
Pulleys are used to drive belt-driven systems. These are essential for changing the speed or direction of motion across a distance between shafts.
3.3.2.3 - Cams
3.3.2.3 - Cams
Cams and Followers
Cams and Followers
The shape of a cam dictates the specific type of motion it produces. Cams are primarily used to translate rotary motion into reciprocating motion.
Common cam shapes include:
• Pear, circular, and triangular.
• Eccentric, oval, and snail.
Pear (eccentric) cam
Circular cam
Triangular cam
3.3.2.4 - Levers
3.3.2.4 - Levers
Levers
Levers
Levers consist of a beam acting on a fulcrum (pivot) and are used to reduce the effort required to move a load.
They are classified into three types based on the relative positions of the Load (L), Effort (E), and Fulcrum (F):
• 1st Class: The fulcrum is between the effort and the load.
• 2nd Class: The load is between the fulcrum and the effort.
• 3rd Class: The effort is between the fulcrum and the load.
3.3.2.5 - Linkages
3.3.2.5 - Linkages
Linkages
Linkages
Linkages are designed to change the direction of movement, alter the magnitude of a force, or ensure parts move in a predetermined way.
Types include: parallel, reverse, and bell crank linkages
In engineering and physics, a linkage is an assembly of rigid bodies (links) connected by joints to manage forces and movement.
Think of them as the "skeleton" of a machine—they take an input motion (like a motor spinning) and transform it into a specific output motion (like a windshield wiper swinging).
3.3.3 - Design Considerations and Sustainability
3.3.3 - Design Considerations and Sustainability
Understanding mechanical systems allows designers to create integrated solutions alongside structural and electronic systems. In modern design, these principles are integral to the functionality of robotic technologies.
From a sustainability perspective, efficient mechanical system design is a core component of Design for a Circular Economy and Design for Sustainability. By creating mechanisms that operate with full functionality over long periods, designers can minimise waste and ensure that mechanical parts are simplified for easy disassembly and repair. Additionally, mechanical advantage is a key tool in inclusive design, enabling products to be more accessible for elderly users or individuals with physical impairments by reducing the physical force required for operation.
Atlas® robot - Boston Dynamics
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