Hinge

Key takeaways

Hinge belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hinge to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hinge from memory before moving on to harder problems.

Reference excerpt

A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation, and all other translations or rotations are prevented; thus a hinge has one degree of freedom. Hinges may be made of flexible material or moving components. In biology, many joints function as hinges, such as the elbow joint. Hinges are frequently used on pivoting doors, but also are seen on folding ladders and many other flexible mechanisms such as automobile hoods (bonnets), and even large bridges.

History Ancient remains of stone, marble, wood, and bronze hinges have been found. Some date back to at least Ancient Egypt, although it is nearly impossible to pinpoint exactly where and when the first hinges were used. In Ancient Egypt, doors were constructed using a pivot hinge system, which consisted of pivots protruding from the edges of a door made either from dowels or carved as part of the door. These pivots were contained within a stone socket. In Ancient Rome, hinges were called cardō, and gave name to the goddess Cardea and the main street Cardo. Cardō, in the sense of "the chief thing (on which something turns or depends)", is an element of modern words such as cardinal. According to the Oxford English Dictionary, the English word hinge is related to hang.

Building access Since at least the medieval period, there have been hinges to draw bridges for defensive purposes for fortified buildings. Hinges are used in contemporary architecture where building settlement can be expected over the life of the building. For example, the Dakin Building in Brisbane, California, was designed with its entrance ramp on a large hinge to allow settlement of the building built on piles over bay mud. This device was effective until October 2006, when it was replaced due to damage and excessive ramp slope.

Large structures Hinges appear in large structures such as elevated freeway and railroad viaducts, to reduce or eliminate the transfer of bending stresses between structural components, typically in an effort to reduce sensitivity to earthquakes. The primary reason for using a hinge, rather than a simpler device such as a slide, is to prevent the separation of adjacent components. When no bending stresses are transmitted across the hinge, it is called a zero moment hinge.

Spacecraft A variety of self-actuating, self-locking hinges have been developed for spacecraft deployable structures such as solar array panels, synthetic aperture radar antennas, booms, radiators, etc.

Terminology

Pin – The rod that holds the leaves together, inside the knuckle. Also known as a pintle. Knuckle – The hollow—typically circular—portion creating the joint of the hinge through which the pin is set. The knuckles of either leaf typically alternate and interlock with the pin passing through all of them. Leaf – The portions (typically two) that extend laterally from the knuckle and typically revolve around the pin. End play – Axial movement between the leaves along the axis of the pin. This motion allows the leaves to rotate without binding and is determined by the typical distance between knuckles (knuckle gap) when both edges of the leaves are aligned. Gauge – Thickness of the leaves. Hinge width – Length from the outer edge of one leaf to the outer edge of the other leaf, perpendicularly across the pin. Hinge length – The length of the leaves parallel to the pin. Knuckle length – The typical length of an individual knuckle parallel to the pin. Leaf width – Length from the center of the pin to the outer edge of the leaf. Pitch – Distance from the end of a knuckle to the same edge of its adjacent knuckle on the same leaf. Doorstop – A colloquialism referring to loose angular movement of the leaves relative to the pin.

Types

Barrel hinge A barrel hinge consists of a sectional barrel (the knuckle) secured by a pivot. A barrel is simply a hollow cylinder. The vast majority of hinges operate on the barrel principle.

Butt hinge / Mortise hinge Any hinge designed to be set into a door or door frame is considered a butt hinge or mortise hinge. A hinge can also be made as a half-mortise, where only one half is mortised and the other is not. Most mortise hinges are also barrel hinges because of how they pivot (i.e., a pair of leaves secured to each other by knuckles through which runs a pin).

Butterfly / Parliament (UK) hinge Butterfly or parliament hinges are hinges that hold surfaces flush when opened 180 degrees.

Case hinge Case hinges are similar to butt hinges, but are usually more decorative; most commonly used in suitcases, briefcases, and the like.

Concealed hinge Used for furniture doors (with or without a self-closing features and/or damping systems), concealed hinges consist of two parts: (1.) the cup and arm, and (2.) the mounting plate. They are also called "cup hinges", or "Euro hinges", as they were developed in Europe and use metric installation standards. Most concealed hinges offer the advantage of full in situ adjustability for the position and gaps of cabinet doors/panels in space by means of three screws on each hinge. Vertical Adjustment (Height): Controls the vertical height of the door panel, resolving issues such as sagging, tilting, or uneven gaps. This is typically achieved by adjusting the hinge base screws. Horizontal Adjustment (Level): Controls the lateral movement of the door panel, resolving issues such as door misalignment or uneven gaps between doors. This is typically achieved by adjusting the screws on the inside of the hinge arm. Front-to-Back Depth Adjustment (Depth): Controls the distance between the door panel and the cabinet/door frame, resolving issues such as doors failing to close properly, colliding with side panels, or excessive gaps. This is typically achieved by adjusting the eccentric screws on the outside of the hinge arm.- **European Standard:** EN 15570 / EN 15828

Continuous / Piano hinge Continuous or piano hinges are a variety of barrel hinge that run the entire length of a door, panel, box, etc. They are manufactured with or without holes.

Flag hinge Flag hinges are simple two-part hinges where a single leaf, attached to a pin, is inserted into a leaf with a hole. This allows the hinged objects to be easily removed (such as removable doors). They are made in right- and left-hand configurations.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Hinge

Start with the simplest possible case. Write down what Hinge claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hinge before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hinge ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hinge

In research: Hinge appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hinge in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hinge is common in secondary-school and first-year university syllabi. It links to neighbouring topics Door furniture, Hinges, Household hardware, so understanding it makes those chapters shorter.
In everyday life: Look for Hinge outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Hinge in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hinge means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hinge out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hinge in simple terms?

A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation, and all other translations or rotations are prevented; thus a hing…

Why does Hinge matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hinge?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hinge.