MECH3230
Chapter 1 Lecture
DR. BEALE
Chapter 1 Topics and Assignments
 Reading/HW for Tuesday 1/24
 Sections 1.1 – 1.5 (briefly, not testable material)
 Section 1.6: Systems of Units, Problems 22, 23, 24, 26, 27
(Due Tuesday)
 Section 1.7: Methodology for Solving HW Problems
 Section 1.8-10: Work and Energy/Power/Conservation of
Energy
 Reading/HW for Thursday 1/26
 Problems 34, 40, 47, 55
Section 1.6: System of Units
 Metric mishap caused loss of NASA orbiter
 NASA's Climate Orbiter was lost September 23, 1999
 (CNN) -- NASA lost a $125 million Mars orbiter because a
Lockheed Martin engineering team used English units of
measurement while the agency's team used the more
conventional metric system for a key spacecraft operation,
according to a review finding released Thursday.
 The engine fired but the spacecraft came within 60 km (36
miles) of the planet -- about 100 km closer than planned and
about 25 km (15 miles) beneath the level at which the it could
function properly, mission members said.
Table 1.4 (p. 16)
English, British, and SI Units for Length, Time, Mass, and Force
Figure 1.3 (p. 17)
Comparison of units of force (or weight) and mass. Note that the weight for each of the
standard masses is valid only or the standard earth gravitational field (g = 9.81 m/s2 or g
= 32.2 ft/s2).
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Comments on Units
 The thing that messes everybody up occurs when English
Engineering (EE) units are used for calculations in
formulas for calculating weight and inertia force terms.
In EE: W=mg/gc
inertia force term: ma/gc, where
gc = 32.174 lbm ft/(s2 lbf) = 1
 BG “fixes” EE, by replacing lbm with slug
 In BG: W=mg
inertia force term: ma
 In SI: W=mg
inertia force term: ma
 You don’t have to memorize these formulas if carry the units with
you and remember:
 N=kg m/s2,
 gc = 32.2 lbm ft/(s2 lbf)=1, or lbf = 32.2 lbm ft/s2
 lbf=slug ft/s2.
 QUESTION: What is g on the moon (approximately)? What is
gc on the moon?

Problem 1.21
Homework Problem Methodology
 Known: State known values
 Find: State what is to be determined
 Schematic and Given Data: handsketch of system,




FBD
Decisions: For design problems where you pick
something, e.g. a material, size, etc.
Assumptions: list any simplifying assumptions to
simplify the problem (e.g. “neglect friction”)
Analysis: show equations, calculations
Comments
Work and Power
Problem 1.31
Conservation of Energy
Punch Press Problem SP1.3
Known: 60 rpm (60
punches/minute), 1200
rpm motor, gearbox. No
flywheel and link inertias
small
Find: Motor Power
Also: Punch presses are
slider-crank mechanisms
Since no flywheel, the motor
must be able to supply the
peak torque of 10 kNm.
Without a flywheel to help,
the motor must be able to
supply it by itself
Sample Problem 1.3 Calculations
Sample Problem 1.4
Known: 60 rpm (60
punches/minute), 1200
rpm motor, gearbox.
FLYWHEEL
Find: Motor Power
 A flywheel stores energy.
We should be able to pick a
flywheel that can release
enough energy during the
punch to reach the crank
torque required load, and
after that build up
rotational kinetic energy
(i.e. the flywheel speeds
up).
Sample Problems 1.4/1.5
Figure 1.9 (p. 28)
Punch press flywheel proportions.
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Problems 1.33/1.39
Automotive Performance Analysis
 Figure 1.10: Vehicle Power Requirement (hp) vs. Speed
(mph). This is the “load”. What is the major force
contributor here?
 Figure 1.11: Engine Output Power (hp) vs. Engine Speed
(rpm). Wide open throttle.
 Use Power In = Power Out. “Power In” is the Engine
Output Power from Figure 1.11. “Power Out” is the
Vehicle Power Requirement
 Figure 1.12: Specific Fuel Consumption (lb/hp h) vs.
Engine Output Power show the effect of a transmission.
Where do you want to be on the curves for best gas
mileage?
Figure 1.13 (p. 31)
Vehicle for Sample Problem 1.4.
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Figure 1.10 (p. 29)
Vehicle power requirement. Typical 4000-lb sedan (level road, constant speed,
no wind).
What force type is the major contributor to this?
What sort of experiment(s) could you use to measure this??
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Figure 1.11 (p. 30)
Engine output power versus engine speed. Typical 350-in.3 V-8 engine.
Full Throttle - How would this be measured in an experiment?
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Brake HorsePower and Dynamometers
Figure 1.12 (p. 30)
Specific fuel consumption versus engine output power. Typical 350-in.3 V-8 engine.
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Figure 1.12
 Where would you operate on Figure 1.12 for best gas
mileage for 1000 rpm? 2000 rpm? In general?
 Where are the full throttle conditions on Figure 1.12?
Figure P1.29 (p. 35)
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Figure P1.32 (p. 35)
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Figure P1.34 (p. 36)
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Figure P1.47 (p. 37)
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Figure P1.54 (p. 38)
Fundamentals of Machine Component Design, 4/E by Robert C. Juvinall and Kurt M. Marshek
Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved.
Problem 1.27 (Assigned)
John Stapp
Examples