Unit 60 Dynamics of Machines



Unit 60:

Dynamics of Machines


Unit code:
H/601/1411

QCF level:
4


Credit value:
15






Aim

This unit will deepen learners’ knowledge of the principles and techniques used in the design of machine elements.

Unit abstract

This unit will develop learners’ understanding of the parameters and characteristics of mechanical systems. Learning outcome 1 is concerned with the characteristics of a wider range of power transmission elements. Learning outcome 2 will introduce learners to an in-depth analysis of some common mechanical systems using both analytical and graphical techniques. Learning outcome 3 is concerned with mechanical vibrations and in particular the transient and steady-state response of mass-spring systems to disturbing forces.

Learning outcomes

On successful completion of this unit a learner will:

1       Be able to determine the kinetic and dynamic parameters of power transmission system elements

2       Be able to determine the kinetic and dynamic parameters of mechanical systems

3      Be able to determine the behavioural characteristics of translational and rotational mass-spring systems.
Unit content

1      Be able to determine the kinetic and dynamic parameters of mechanical power transmission system elements

Gears: gear geometry; velocity ratios of simple, compound and epicyclic gear trains; acceleration of geared systems

Screw drives: motion on an inclined plane; efficiency of square-threaded lead screws and screw jacks

Flywheels: turning moment diagrams for reciprocating engines and presses; determination of required flywheel moment of inertia to satisfy specified operating conditions

Universal couplings: Hooke’s joint; constant velocity joint; conditions for a constant velocity ratio

2      Be able to determine the kinetic and dynamic parameters of mechanical systems

Cams: radial plate and cylindrical cams; follower types; profiles to give uniform velocity; uniform acceleration and retardation and simple harmonic motion outputs; output characteristics of eccentric circular cams, circular arc cams and cams with circular arc and tangent profiles with flat-faced and roller followers

Plane mechanisms: determination of instantaneous output velocity for the slider-crank mechanism, the four-bar linkage and the slotted link and Whitworth quick return motions; construction of velocity vector diagrams; use of instantaneous centre of rotation

Resultant acceleration: centripetal, tangential, radial and Coriolis components of acceleration in plane linkage mechanisms; resultant acceleration and inertia force; use of Klein’s construction for the slider crank mechanism

Gyroscopic motion: angular velocities of rotation and precession; gyroscopic reaction torque; useful applications eg gyro-compass and gyro-stabilisers

3      Be able to determine the behavioural characteristics of translational and rotational mass-spring systems

Natural vibrations: mass-spring systems; transverse vibrations of beams and cantilevers; torsional vibrations of single and two-rotor systems; determination of natural frequency of vibration; whirling of shafts

Damped vibrations: representative second-order differential equation for mass-spring system with damping; transient response of a mass-spring system to an impulsive disturbance; degrees of damping; frequency of damped vibrations; logarithmic decrement of amplitude

Forced vibrations: representative second-order differential equation for a damped mass-spring system subjected to a sinusoidal input excitation; transient and steady state solutions; amplitude and phase angle of the steady state output; effect of damping ratio; conditions for resonance

Learning outcomes and assessment criteria




Learning outcomes
Assessment criteria for pass


On successful completion of
The learner can:


this unit a learner will:










LO1 Be able to determine the

1.1
analyse geared systems to determine velocity ratio


kinetic and dynamic


and required accelerating torque


parameters of mechanical

1.2
determine the operating efficiency of screw jacks


power transmission system





and lead screws


elements











1.3
analyse turning moment diagrams for reciprocating





engines and presses to determine the required





flywheel parameters for specific operating conditions




1.4
analyse the characteristics of Hooke’s joints and





constant velocity joints and recognise the conditions





for a constant velocity ratio








LO2 Be able to determine the

2.1
determine the output motion of radial plate and


kinetic and dynamic


cylindrical cams


parameters of mechanical

2.2
determine the velocities and accelerations of points


systems





within plane mechanisms and the associated inertia










Forces




2.3
analyse systems in which gyroscopic motion is





present to determine the magnitude and effect of





gyroscopic reaction torque







LO3 Be able to determine the

3.1
determine the natural frequency of vibration in


behavioural characteristics of


translational and rotational mass-spring systems


translational and rotational

3.2
determine the critical whirling speed of shafts


mass-spring systems










3.3
determine the transient response of damped mass-





spring systems when subjected to a disturbance




3.4
determine the steady state response of damped





mass-spring systems when subjected to sinusoidal





excitation.










Guidance

Links

This unit is intended to provide progression from Unit 2: Engineering Science and Unit 4: Mechanical Principles.

Essential requirements

There are no essential requirements for this unit.


Employer engagement and vocational contexts

Delivery of this unit will benefit from centres establishing strong links with employers willing to contribute to the delivery of teaching, work-based placements and/or detailed case study materials.

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