Test: Simple Mechanisms - 1 - Mechanical Engineering MCQ

Structure and machine both are permanent construction. e.g. structure: Roof truss, machine frame, railway bridge etc.

If two mating links have a turning as well as sliding motion between them, they form a screw pair. This is achieved by cutting matching threads on the two links. The lead screw and the nut of a lathe is a screw pair.

The mechanisms used to overcome a large resistance of a member with a small driving force are known as snap action or toggle mechanisms.

The mechanisms used to overcome a large resistance of a member with a small driving force are known as snap action or toggle mechanisms. They find their use in a variety of machines such as stone crushers, embossing presses, switches etc.

Inversion of double slider-crank chain:
1. Elliptic trammel
2. Scotch yoke
3. Oldham's coupling Whitworth quick return mechanism is second inversion of single slider chain
Beam enigne is a type of steam engine

Except scotch yoke, all three are inversion of single slider chain.

Firstly, this topic is discussed under KINEMATICS PAIRING.

Based on nature of contact between elements;

Lower Pair: The joint by which two members are connected has surface contact (one element slides with another’s surface).
Discussion:
surface contact means large area of contact between two surfaces which divided into two categories:
i) Planar (2D) Mechanism -(2 axis movements)
ii) Spatial (3D) Mechanism -(3 axis movements)
Example:
Sliding pairs, turning pairs, screw pairs.

Higher Pair: The contact between pairing elements takes place at a point or a line.
Discussion:
it’s mentioned ‘a point’ or a ‘line’ because the surface contact between pairing elements is very small until it is considered as a point-to-point contact.
Example:

the contacts is relatively very small between pairing elements.

Binary joints :I and F
Ternary joints : H, G, E, C, A and D
Quaternary joint : B