Mechanical Engineering

# Mechanics Corner

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A Journal of Applied Mechanics and Mathematics by DrD

## SR-71

I've seen this plane close enough to touch it. It is the most frightening machine you can imagine. DrD   SR-71 Blackbird: The Cold War's ultimate spy plane     (Image credit: Lockheed Martin) By Stephen Dowling1st July 2013   Colonel Rich Graham spent 15 years as a Blackbird pilot and wing commander. He told BBC

## Mine Hoist Problem, #54

Mechanics Corner     A Journal of Applied Mechanics and Mathematics by DrD, # 54     © 25 August, 2020                                                          Mine Hoist Problem Introduction     As we saw in the previous problem (A Hoisting Problem for Engineers, #53), hoisting problems can be fun. This has gotten me to thinking about some other hoist related problems, and here I present three variations on a new problem. The problem is much the same in all three cases, with

## A-10

This is another incredible aircraft, essentially a plane built around a cannon. DrD

## Wheel Climbing A Step

Mechanics Corner     A Journal of Applied Mechanics and Mathematics by DrD, # 55     © December, 2020                                                        Wheel Climbing A Step Introduction     The problem that follows was brought to my attention by a student at a great European university. It was a part of a much bigger problem with which the student was engaged, but this is quite enough to hold our interest. The results are differential equations of motion which could

## Mine Hoist Problem, Hint #2

Mechanics Corner A Journal of Mechanics & Mathematics by Dr.D, #54 B                                                          Mine Hoist Problem, Hint #2 Introduction     The original Mine Hoist Problem was posted 25 August 2020, and the first Hint was given on 8 September. We are now almost one month into this problem, and thus far no one has sent me even so much as a question other than Tim Dennison's request for a video. I'm not quite sure how to understand this. I see

## Why You Shouuld NOT Use the D'Alembert's Principle

Mechanics Corner   #50 A Journal of Applied Mechanics and Mathematics by DrD                                    Why You Should NOT Use the D'Alembert's Principle I think it is safe to say that every engineering student studies both Statics and Dynamics. We are told that Statics is easier than Dynamics, which is often true but not so in all cases. When we get to Dynamics, many teachers, particularly physics teachers, will urge the use of something called D'Alembert's Principle. The

## What Makes A Ship Move?

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #47                                                               What Makes a Ship Move? One of the problems that often confronts engineers is the description of large, interconnected systems. Engineers tend to specialize, so that one is very knowledgeable on gears, another knows bearings, a third knows pumps, but none of them are comfortable with the whole system. In the automotive context, this is often exp

## What Would You Like to Know?

What Would You Like  to Know? If you could ask me any question you want, what would you like to know that you think I might know? I certainly do not know everything, but through the years I have accumulated a certan amount of knowledge that I'd like to pass on to you. Therefore, I ask, what would you like to know? Many readers are still in college, and no doubt they would like to know what is going to be on the next exam. I'm sorry, but I have no way to know that. What I might be able

## When You Ask for Help ....

Today, I have a question for readers. I'd like to get everyone who is willing to answer the same question, but also tell me whether you are a practicing graduate engineer or if you currently a student. I think these two groups will answer somewhat differently, so it is important that you identify which one you fall into. The question is really simple: When you ask for help, what do you really want? Are you asking for someone to step in and solve a problem for you? Or, are you asking for a f

Mechanics Corner A Journal of Applied Mechanics & Mathematics, #49 A Bad Example Most of us are inclined to trust an established textbook. We assume (1) the author knows what he is talking about, (2) the book has been carefully vetted by several editors and reviewers, and finally (3) the fact that it is well established in the market means that thousands of other readers have tacitly endorsed it as well. While these assumptions are usually true, they are no guarantee, and they

## New Help Site

I'd like to invite all readers to visit my new website: Machinery-Mechanics-Professor.site I'm offering free help for engineering students through that site, so come on over and take a look. DrD

## Mass On Multiple Spring Supports

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #48                                                     Mass On Multiple Spring Supports   Introduction One of the classic problems of elementary mechanics is to determine the load on each leg of a four-legged table. The table top is assumed to be a uniform rectangle, the legs are of equal length, the center of mass is the centroid of the table top, and the floor is level. What is the load in ea

## A Calculus Challenge

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #45 (c) DrD, 2018 It has been quite a while since I last posted anything here, but an interesting problem has come to mind that I wanted to share with you. If you really know calculus, this should be straight forward; if you don't know calculus, don't even try! MEForumChallenge.pdf   ***********************************************************************************************************

## How To Become An Expert

Mechanics Corner     A Journal of Applied Mechanics and Mathematics by DrD     © Machinery Dynamics Research, 2016 How To Become An Expert      Introduction     This is going to be another of those personal experience/opinion pieces, so if these bore you, be warned! This may be the time to click on something else.     A reader recently wrote to me asking how to become an expert. I have to tell you, I don't spend much time thinking about being an expert, but I suppose o

## Two Short Math Problems

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #40 July, 2017   Two Short Math Problems Do you ever read the ads that appear on ME Forum? I try to avoid them as much as possible, but an organization called BRILLIANT has put up some interesting math problems of late that have caught my eye. Two of them are the subject of today's post. The first problem that I want to discuss is actually more recent than the other, but it gives us a good plac

## #44 Mouse Trap / Pendulum Dynamics Challenge

Mechanics Corner     A Journal of Applied Mechanics and Mathematics by DrD, # 44       Machinery Dynamics Research, 2017      Mouse Trap / Pendulum Dynamics Challenge - Part I Introduction     Mice are a problem all over the world, and as a result, I'm sure that there are mouse traps of various sorts found everywhere. It would be utterly amazing if this were not true! In the USA, there is a very common type of mouse trap that I have seen used all my life, the sort of system

## #43 Four-Bar / Toggle Linkage Mechanism

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #43 (c) Machinery Dynamics Research, 2017   Four-Bar / Toggle Linkage Mechanism Introduction   I believe that it would be correct to say that all of the single degree of freedom mechanisms that I have discussed on ME Forums have involved only a single loop. This might lead a reader to conclude that a single degree of freedom implies only a single loop, and vice versa, that a single loop imp

## Comments on a Textbook - Khurmi & Gupta

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #39 (c) Machinery Dynamics Research, 2017 Comments on a Textbook Theory of Machines by R.S. Khurmi & J.K. Gupta 1 Introduction Recently, through the wonders of the Internet, I have come across a copy of the textbook Theory of Machines by R.S. Khurmi and J.K. Gupta (S.Chand & Co., Ltd., 2005). Since theory of machines has been my primary technical interest since the early 1980s, I was interested

Many of you have asked me various questions, so now it is my turn. Let me lay a bit of background first, and then the questions.   I have had some conversations recently with JAG (one of the other writers here at ME Forums) regarding the choice of software for 3D modeling and analysis. JAG has made some excellent suggestions, specifically a cloud based program called Onshape. Unfortunately, for reasons that are unclear, my computer cannot run Onshape; I have worked with their help peop

## Triple Rocker

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD July 31, 2017 Triple Rocker Over at the Kinematics of Machines club, I recently ask if anyone could show me an example of a four-bar linkage that would be classed as a triple rocker. In the terminology of four-bar linkages, a link is classed as either a crank or a rocker: Crank - can rotate in a complete circle Rocker - cannot rotate in a complete circle] Thus my question was for an example

## #42 Gear Pair Problem

Mechanics Corner     A Journal of Applied Mechanics and Mathematics by DrD, # 42     © Machinery Dynamics Research, 2017 Gear Pair Problem      Introduction     In this post, I want to discuss a seemingly simple problem currently being discussed at Physics Forums (PF). The original question, posed by someone, perhaps a student but perhaps not, is quoted below:       So, we have a pinion and a gear. I give an input torque Tp in the clockwise direction. Th

## Modeling Hysteresis

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #41 (c) Machinery Dynamics Research, July 2017   Modeling Hysteresis 1. Introduction What do you know about hysteresis? Many Mechanical Engineers will associate this term with the magnetization curve of a piece of magnetic material, and quickly conclude, "I don't have to worry about that!" But that would be wrong. While hysteresis does occur in magnetic systems, it happens in many other situatio

## Rocket Homework Problem

Mechanics Corner     A Journal of Applied Mechanics and Mathematics by DrD, #38       Machinery Dynamics Research, 2017 Rocket Homework Problem Introduction     Most engineers find problems involving rockets to be exciting. There is something about a rocket that fires our imagination, whether we think of going to the moon or one of the planets, or simply of shooting down an incoming missile. The subject of this post involves a rocket on a mobile launcher. The rocket is i

## ODE Solution --- Fail!!

Mechanics Corner     A Journal of Applied Mechanics and Mathematics by DrD, # 31       Machinery Dynamics Research, 2016 ODE Solution --- Fail!!      Introduction     Digital computation has become a major tool for engineers, and it is a great benefit. It can also lead to many pitfalls for the unwary. This note is about the latter, a potential pitfall that many engineers risk on a daily basis, most of them with little awareness of the danger.     Early in the developme

## Where Would You Publish It?

Mechanics Corner Where Would You Publish It? Since long before my time, there has been a desire to have important results published where they become accessible to many others. Some of the great names, such as Newton, Euler, Bernoulli, and others, we know primarily because of what they published. Their work formed the fundamentals upon which modern engineering and science is built. Publication of research results has long been particularly important to faculty members; it is often take

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