Crank Mechanism
Name: Monish Kumar (S11065194)
The University of the South Pacific
MM313 Dynamic Systems
Experiment 2- Crank Mechanism
Aim:
To investigate the relationship between piston displacement and crank angle for different ratios between the connecting rod and the crank. Also to look at the relationship between the turning moment on the crank shaft and crank angle for a given force on the piston.
Equipment and Instrument:
Introduction:
A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to convert circular motion into reciprocating motion, or vice-versa. The arm may be a bent portion of the shaft, or a separate arm attached to it. Attached to the end of the crank by a pivot is a rod, usually called a connecting rod. The end of the rod attached to the crank moves in a circular motion, while the other end is usually constrained to move in a linear sliding motion.
Theory:
Figure 1.0: Slider crank mechanism
The slider crank mechanism as shown in figure 1.0 is a kinematic mechanism. The piston displacement from the top dead centre, x, can be determined from the geometry of the mechanism, in terms of the lengths of the connecting rod, L, and crank, R, and the crank angle, θ, can be expressed as x=L+R-(Lcosφ-Rcosϑ) Also from the geometry, it can be seen that
Rsinϑ=Lsinφ
And
sinφ=sinϑn
Hence
cosφ=[1+sinϑn2]1/2
Where n is a ratio: n=LR Procedure:
Part A: 1) No weights and hangers required, the unit initial starting position 0 in the protractor is setup and 90⁰ and 270⁰ protractor positions to be in line with the level lines in each side. 2) The unit is to be setup in its highest point, Top dead centre point was used to work out the displacement value 3) The mounted disc was turned 30⁰ and the displacement was noted on the results table, this step was again repeated for different angles and different crank positions.
Part B:
The University of the South Pacific
MM313 Dynamic Systems
Experiment 2- Crank Mechanism
Aim:
To investigate the relationship between piston displacement and crank angle for different ratios between the connecting rod and the crank. Also to look at the relationship between the turning moment on the crank shaft and crank angle for a given force on the piston.
Equipment and Instrument:
Introduction:
A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to convert circular motion into reciprocating motion, or vice-versa. The arm may be a bent portion of the shaft, or a separate arm attached to it. Attached to the end of the crank by a pivot is a rod, usually called a connecting rod. The end of the rod attached to the crank moves in a circular motion, while the other end is usually constrained to move in a linear sliding motion.
Theory:
Figure 1.0: Slider crank mechanism
The slider crank mechanism as shown in figure 1.0 is a kinematic mechanism. The piston displacement from the top dead centre, x, can be determined from the geometry of the mechanism, in terms of the lengths of the connecting rod, L, and crank, R, and the crank angle, θ, can be expressed as x=L+R-(Lcosφ-Rcosϑ) Also from the geometry, it can be seen that
Rsinϑ=Lsinφ
And
sinφ=sinϑn
Hence
cosφ=[1+sinϑn2]1/2
Where n is a ratio: n=LR Procedure:
Part A: 1) No weights and hangers required, the unit initial starting position 0 in the protractor is setup and 90⁰ and 270⁰ protractor positions to be in line with the level lines in each side. 2) The unit is to be setup in its highest point, Top dead centre point was used to work out the displacement value 3) The mounted disc was turned 30⁰ and the displacement was noted on the results table, this step was again repeated for different angles and different crank positions.
Part B: