Mechanics of machines

just ni yang aku dapat share

NO.	Questions
1	Power Transmission       ·         Electrical power- transmission with underground cable(short-distance power)                                                              ·         Mechanical power- The oldest long-distance power transmission             - Transmission by gears             - Transmission by Belts             -Transmissions by ropes ·         Chemicals and fuels- radioactive isotopes, methane, hydrogen gas       4 gears (still tak berapa paham)       Only those who really u/s concept can answers
2	Types of belt   (http://www.roymech.co.uk/Useful_Tables/Drive/Flat_belts.html)       -flat belts       -Vee belts       -Timing belts       & arrangement of belt       Study necessary symbols “creep of belt” Creep theory describes the transmission of power between a running pulley and elastic belt. The name “creep” comes from the fact that frictional forces cause a change in belt tension thereby causing the elastic belt to extend and contract. This action results in relative motion between the belt and pulley surfaces which is termed elastic creep. The theory does make some simplifying assumptions concerning friction and elasticity which do not apply exactly to all materials. (still tak tau nak label) Fc = Centrifugal Force (N) R = Pulley reaction Force (N) P = Max power transferred kW T = Belt tension Tc = Belt tension due to centrifugal force μ = Coefficient of Friction. b = Belt width (m) ω = Angular velocity of pulley (rad/s) n = Rotational Speed (RPM) θ = Angle of belt lap v = Linear velocity of belt (m/s)       -Length of belt       (http://library.thinkquest.org/20991/geo/circles.html) 1. Problem: Find the length of a 24o arc of               a circle with a 5 cm radius.           Solution:      n             24           2(PI)               L = ---(2(PI)r) = ---(2(PI))5 = -----                   360           360             3                                                     The length of the arc is (2/3)(PI) cm.     -need to think/logic
3	Term primary balance, secondary balance, firing order         Primary balance is the balance achieved by compensating for the eccentricities of the masses in the rotating system, including the connecting rods. Primary balance is controlled by adding or removing mass to or from the crankshaft, typically at each end, at the required radius and angle, which varies both due to design and manufacturing tolerances. In theory, any conventional engine design can be balanced perfectly for primary balance. Secondary balance can include compensating (or being unable to compensate) for: The kinetic energy of the pistons. The non-sinusoidal motion of the pistons. The motion of the connecting rods. The sideways motion of balance shaft weights. The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine. This is achieved by sparking of the spark plugs in a gasoline engine in the correct order, or by the sequence of fuel injection in a Diesel engine. When designing an engine, choosing an appropriate firing order is critical to minimizing vibration and achieving smooth running, for long engine fatigue life and user comfort, and heavily influences crankshaft design       4masses
4	Term flywheel, coefficient of energy, coefficient of speed A flywheel is a rotating disk used as a storage device for kinetic energy and smooths the operation of a reciprocating engine The ratio between the energy transmitted forward in a wave per unit crest length at a point in shallow water, and the energy transmitted forward in a wave per unit crest length in deep water. The coefficient of speed fluctuation Cs is defined as where ω = rotational speed at the flywheel and ωavg = average of ωmax and ωmin. Ranges for Cs for several categories of speed variation are given in the following table. Assume that the system is stiff (the speeds of all shafts are proportional)
5	Difficult question (put for eac)