Machine Mechanics II (MAM21) 2021 S1
LF Monaheng
PRACTICAL 1: POWER TRANSMISSION
Submission date: To be announced.
Submission method: ethuto in pdf format
1. Aims of the practical work
The aims of this experiment are as follows:
i.
To familiarise with the calculation of input and output power and efficiency of the manual
automotive gear system under different speeds.
ii.
To determine the different gear ratios.
iii.
To calculate the amount of power and torque transmitted by the automotive gear system
under different gear ratios and speeds.
iv.
To determine the equivalent inertia of the gear.
2. Introduction
The automotive power transmission system is studied in practical 1. This system consists of an engine,
clutch, flywheel, compound gear, and differential gearbox. The compound gear system has 15 spur
gears of the same module. Whereas the differential gear system consists of arm and 2 gears in mesh.
The engine power is transmitted through the clutch to both compound and differential gear systems.
The wheel shafts are connected to gear P of the differential gear system. In Figure 1 an automotive
power train system is shown.
Figure 1: Automotive power transmission
3. Summary of theory
3.1.
State where and why gears are used in engineering.
3.2.
Describe how the automotive gear system operates.
3.3.
With a neat and clear engineering sketch, define a law of gearing.
3.4.
Derive the expression of the gear ratio using sketch drawn in 3.3 and the law of gearing.
3.5.
Derive an expression for the total torque which must be applied to the compound gear input
shaft to accelerate the gear system and state the equivalent mass moment of inertia. Follow
the procedure in chapter 3 page 49 of the Theory of Machines textbook.
Self-study: Chapter 12 and 13: Gears and Gear Train
Source: Khurmi, R.S. & Gupta, J. K., 2005, Theory of Machines, Eurasia Publishing House.
4. Experimental procedure
4.1.
For the practical application, the automotive power transmission system is fixed to the
ground and operated as shown in the video provided in ethuto (named: how car
transmission system works).
4.2.
The gear's number of teeth was counted and provided in the experimental data table 1.
4.3.
Set the first gear (1st) using the gear lever mechanism.
4.4.
Start the engine and measure the speed of the crankshaft in rpm.
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Machine Mechanics II (MAM21) 2021 S1
4.5.
4.6.
LF Monaheng
Press the clutch to disengage the power between the engine and the compound gear
system and select the second gear (2nd). Again, determine the speed of the wheel shaft.
Repeat step 4.5 for the 3rd, 4th, and 5th gears.
5. Experimental parameters
5.1.
With the support of a neat engineering sketch, provide the geometrical parameters of the
actual automotive gear system used in this experiment.
5.2.
Using the measurements obtained from the practical session, find experimental data in
Table 1 to perform the necessary calculations.
Table 1: Experimental data
6. Procedure for calculations
Using the experimental data in Table 1, calculate the following for all gear setting and list the
results in a table form:
6.1.
The speed of the wheel shaft. A clear calculation must be shown for 1st gear and other
calculations must be done using Microsoft excel software or any other electronic
mathematical tool.
6.2.
If the wheel shaft is connected to the wheel assembly with a diameter of 355 mm, calculate
the speed of the wheel in m/s.
6.3.
If the efficiency of the compound gearbox is 84% calculate the output torque of the
compound gear system.
The moments of inertia of the parts attached to the input shaft X of the compound gearbox is
0.019 kgm2 and that of the parts attached to the output shaft Y of the compound gear system is
0.1 kgm2. If input shaft X exerts a constant torque of 7.27 Nm and is geared to output shaft Y,
calculate the following:
6.4.
6.5.
The gear ratio that gives the maximum angular acceleration of output shaft Y.
The corresponding angular acceleration of each shaft.
N.B:
1. In general, the report must be electronically typed with a text of 12pt of size and Arial narrow
font.
2. The provided annotations (symbols) in this practical guide must be respected, and all used
annotations in any analytical expression must be well named and/or be shown on a supporting
sketch where it is necessary.
3. A compulsory COVER PAGE is attached. The cover page must be electronically filled and
signed.
4. A numerical or Harvard reference method must be used.
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Machine Mechanics II (MAM21) 2021 S1
LF Monaheng
RESULT%
Student number(s):
Surname and initials:
Programme:
BEng Tech (Mechanical Engineering)
Module name:
Module code:
Graduate Attribute (GA) exposed:
1
2
X
X
3
4
5
6
7
8
9
10
X
Assignment/project number:
Due date:
2
0
1
9
M
M
D
D
Lecturer:
DECLARATION OF OWN WORK:
I,
______________________________________________________________,
student
number______________________________________, hereby declare that the content of this assignment/project is my own work, as
defined and constituted in the Rules and Regulations of the Central University of Technology, Free State (Please consult the Programme
Guide of the Department).
Signed: ________________________________
Date:
________________________________
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Machine Mechanics II (MAM21) 2021 S1
LF Monaheng
Data and
observations
Experimental
procedure
Summary of
theory
Sketch of
apparatus
Aim of
practical
Practical Assignment rubric with integrated ECSA graduate attribute for exposure
Topic
Poor
Below average
Average
Above average
Excellent
Total
Weight
0-1: No aim
at all
1-2: The aim is
presented, but
not clear
2-3: The aim is given as stated in
the lab guide
3-4: The aim reflects an
overall understanding of what
needs to be done.
4-5: The aim is explained, in
the words of the student, the
objective of the experiment is
clear.
0-1: No
sketch
2-4: Copied and
pasted picture
4-5: Unlabelled sketch
Work is performed within the
boundaries of the practice area.
(GA2)
6-8: Hand-draw sketch with
labels and description of the
operation of the apparatus.
8-10: computer -sketched with
labels and a short description
of how the apparatus works.
10
0 No
summary is
given at all
2-4: It is
presented In
point form and
not essay style
6-7: Good writing skills
(language and grammar).
There should be coherence.
8-10: Correct language and
grammar. The relevant points
presented to good coherence.
10
0-1: Copied
from the
practical
guide
1-2: Written in
student’s own
words but is not
clear.
4-5: No continuity of facts. No
relevance of the discussion.
Coherent and detailed
engineering knowledge
underpinning the technology
area is illustrated. (GA1)
Concepts, ideas, and theories
are communicated (GA 2)
2-3: Presented in student’s own
words and the process is clear.
Investigations and experiments
are planned and conducted
within an appropriate
discipline. (GA4)
3-4: Presented in student’s
own words and the process
is clear and correct.
4-5: Written in past tense and
in third person, student’s own
words. The procedure must be
clear and correct.
0: No data
collected
2-4: The data
collected is
presented in an
informal
manner.
4-5: The data is present in a table
form and the analysis is provided.
Uncertainty and risk are
handled. (GA2)
Information is analysed,
interpreted, and derived from
available data. (GA4)
6-8: The data is present in a
table form and the analysis
provided is correct.
8-10: The data is clearly
captured and tabulated. Short
description of the data or the
table. Data and its analysis are
correct.
4
5
5
10
Conclusion
Results and
discussion
Calculations and
graphs
Machine Mechanics II (MAM21) 2021 S1
0-4:
Calculations
not done
according to
the
instruction in
the guide or
any scientific
source.
5-10: The
calculation
formulas are not
used.
0-1: No
results and
no
discussion.
3-4: The results
are tabulated
without any
discussion.
0-1: No
conclusions
are drawn.
2-4: No firmness
in the ideas
presented that
are taken from
the data
collected.
LF Monaheng
10-15: The calculations are
clearly shown as instructed by
any scientific source and
presented with the graph, or
sketch where are applicable.
The problem is solved using a
structured analysis technique.
(GA1)
An appropriate mix of
knowledge of mathematics is
used. (GA2)
5-6: The results are correctly
tabulated, and discussed.
Reasoning about and
conceptualising engineering
materials, components,
systems or processes is
performed. (GA2)
5-6: If the partial correct
conclusion is made.
Conclusions are drawn from an
analysis of all available
evidence. (GA2)
5
15-18: The calculations are
clearly shown as instructed in
the guide or any scientific
source but graphs or
sketches were drawn are not
of the correct properties.
18-20: The calculations are
clearly shown as instructed in
the guide. The graphs or
sketches drawn are of the
correct properties and are
labeled correctly.
7-8: The results are correctly
tabulated, and correctly
discussed.
9-10: The results are correctly
calculated and tabulated. The
discussion is clear and
scientifically correct.
7-8: Correct conclusion is
made covering all the
aspects from which
assumptions were made to
close the argument.
9-10: Correct conclusion is
made covering all the aspects
from which assumptions were
made to close the argument. A
statement provided in this
section fully convinces that
researched ideas or the
problem completely is
completely solved.
20
10
10
Accuracy and neatness
Machine Mechanics II (MAM21) 2021 S1
0-4: Substandard
presentation
of workpages not
numbered,
topics not
fully covered,
spelling and
grammatical
errors.
Unfollowable
order of the
numbering.
5-10: No logical
order on the
ideas presented.
Writing skills,
sentence
construction,
grammar, etc
are below
average.
LF Monaheng
11-14: Average writing skills.
Quite easy to follow. Meaning
ideas in a coherent order.
Repetition of words in writing.
The purpose, process, and
outcomes of the investigation
are recorded in a technical
report. (GA2)
15-17: Average writing skills.
Quite easy to follow.
Meaning ideas in a coherent
order. No unnecessary
repetition of words in writing.
Correct grammar and
punctuations. 80% of the
report is typed.
6
18-20: Easy to follow
(coherence). Consistency in
font and academics writing
style. All the topics and subtopics are numbered
sequentially. Clear table of
contents, which correspond to
the report contents. Topics
put as numbered on the index.
Correctly referenced (Harvard
method). 100% of the report is
typed and the sketches are
done in any digital method.
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