You can use your engineering knowledge for most nefarious purposes. -Prof. PK
Sunday, August 31, 2008
Sunday, August 17, 2008
Fun with numbers
This week, near the end of a long day at work, I was sitting in a conference room with some accountants from out of town. They were thinking about hitting a local 'riverboat' to waste a few hours and some money at the blackjack tables. They checked out this place online and noticed that there was a game variant called 'twenty one plus three.' Not remembering that they had an audience, one accountant asked another,
"What's twenty one plus three?"
Absentmindedly I replied,
"It's twenty four."
The room was silent for a moment before erupting in chuckles and disparaging remarks about accountants.
The lesson: Make sure your remarks are not taken out of context!
Friday, August 15, 2008
This week's post comes to you courtesy of the National Museum of the U.S. Air Force in Dayton OH. I just spent the week in Dayton and although I did not have time to visit the museum, I managed to dig these photos out of my archive. As I've said before, this is an amazing museum with a very large collection and you have to have plenty of time if you want to get the most out of it.
These pictures came from the WWII hangar.
Meet the P39 Airacobra. These were produced by Bell Aircraft Corporation beginning in 1939 and used in combat throughout WWII.
If it looks a bit odd for an aircraft of that era, there's a reason. Most propeller driven fighter aircraft were designed around an engine and prop in the nose of the aircraft. This design was different, it centered around an Oldsmobile T9 cannon which was actually made to fire through the center of the prop. This was a particularly large and bulky weapon and the desire to make it fire through the propeller made it necessary to find another location for the engine. The engineers at Bell settled on a mid-engine design.
That's what the P39 looks like on the inside. The engine sits behind the pilot and a driveshaft (which looks surprisingly thin to me) runs to the nose of the aircraft where it is joined to the propeller with a gearbox. This design gave it very different characteristics from the other fighter aircraft at the time. The location of the center of gravity made the aircraft nimble, with a roll rate comparable to or better than many of its contemporaries. This also led to a tendency to go into flat spins if there was not enough weight in the nose of the aircraft. (Aircraft which were not carrying ammunition had to be ballasted in order to be safely flown.) The plane also had to be equipped with unusual nose wheel landing gear system.
The engine location meant that the nose could have a very streamlined and efficient profile, but putting the engine compartment behind the fuselage meant that there was no room left for gas tanks. This meant that the fuel tanks had to be installed in the wings. This limited the fuel capacity (though it was often supplemented with drop tanks) meaning that the plane was typically limited to short range missions rather than long range patrols. The plane's operation was also limited because it was underpowered compared to many other aircraft. The single stage supercharger limited it to low altitude work, which is unusual considering that it was originally designed in response to a request for a high altitude interceptor aircraft. This was later resolved with the introduction of the P63 kingcobra that had a more powerful engine and different wing profile.
Pilots in the US and the UK typically did not find the aircraft very appealing. Aside from some complaints about having to fly with a high speed driveshaft between their legs, they found that the lack of power and high altitude performance severely handicapped their work. They were still quite effective as low altitude interceptors, which made them useful for quite some time. Unfortunately the tactics used in the western European theater did not allow the full potential of these planes to be explored. The US mostly used fighters for escorts on high altitude bombing runs, and the airacobra was not able to perform well at these altitudes.
It was the Russians who really used the plane to its full potential. They needed escorts for low altitude bombing runs and fighter bombers for ground attack. The airacobra shined in this role. Not having the engine in the nose meant that when the plane was making ground attacks, the engine was not up front and was therefore not very vulnerable to ground fire. The nose cannon also provided a very stable firing platform with an incredible amount of power. This made the airacobra an effective ground attack aircraft. It's commonly believed that the airacobra was used extensively as a tank killer, though some have questioned this as armor piercing rounds were not available for the P39’s cannon.
The Russians most certainly used this in fighter duty against the Germans in the air. This is where it developed a very good reputation as a fighter. Low altitude battles were the airacobra's forte because it had enough power to compete with other fighters and because of its considerable maneuverability.
In air combat altitude is quite important. It can be traded for speed and speed gives you the ability to escape from a dogfight. This fact has saved many fighter pilots from attacks by aircraft with superior maneuverability. But when you eliminate the ability to dive out of a fight, maneuverability becomes much more important and this is where the airacobra performed well.
It didn't hurt that it was incredibly well armed. The T9 cannon could fire a 1.3 lb projectile! Of course with ammunition of that size and weight, you couldn't carry very many rounds, or fire very fast, so the cannon was supplemented with either two or four machine guns mounted on the nose (In the conventional manner) and three machine guns mounted in each wing. Supposedly, some Russian pilots removed machine guns from the wings to improve the roll rate of the aircraft. They apparently felt that the nose guns were sufficient for their purposes. I can't blame them.
It's hard to think you need more firepower when you have one of these!
Labels: Transportation - Air
Sunday, August 10, 2008
Friday, August 08, 2008
The Instant Engineer Kit
"You have to be born to it." That's what my supervisor said about our types of jobs. This was after I related an incident that had occurred a few weeks earlier.
I was in a manufacturing facility (a regular occurrence in my position) when the plant manager came into the office to review my work. When I opened my computer, he looked at my desktop wallpaper with one eyebrow raised, so I explained that it was from the Atwater Kent radio factory during the 1920s. He looked at me with a somewhat bemused expression and said "You know, most people have pictures of family or vacations on their desktop, not a factory from the 1920s."
Skipping ahead to when my supervisor first saw the photo, he glanced at the picture then looked back again with the slight grin that he always has when his curiosity has been aroused. I told him about the plant manager, and he replied "You have to be born to it."
I don't know if I believe that, but I suspect there is a grain of truth to it. I didn't have much exposure to industrial environments when I was young. I did, however, have plenty of exposure to machinery, even if most of it was made more than a few decades before I was. So maybe there is a reason why I enjoy the kinds of things I work on.
Enjoying my job is a big part of being able to do it well, or at least I think it is. But that's not to say that there aren't things that can help you be an effective engineer.
Recently True Blue Sam introduced me to his "ACME Instant Forester Kit" It's a compilation of the data and tools that are needed to generate a forest management plan. Of course, you should have at least a basic understanding of what you're doing before the kit will do you much good, but if you have some basic knowledge, it has pretty much everything you need.
Inspired by this kit I've decided to put together a list of the essential tools that I use for my job.
Click Here [+/-]
Information (or more precisely, correct information) is your biggest ally on the job. That is why the first two items on my list are books.
If you ever set foot in a machine shop or draft a single mechanical drawing, you should have this book, as it is full of every type of design related information imaginable. I have the 26th edition, which is relatively recent, but I have a certain fondness for older, well worn copies. They feel like old bibles when you hold them, and fittingly so as such books have guided machinists and engineers for generations.
Of course, if you don't like carrying around a book the size of an unabridged dictionary (or have a problem with small print) you can always get the CD version and read this book straight from your computer.
The Machinery's Handbook's theory based cousin is a much more portable, if somewhat less practical, resource. Geick's Engineering Formulas has been around for more than 30 years, but is something of a recent discovery for me. If I were a little more paranoid I might think that knowledge of this book was intentionally withheld. Why? Because for about $35 this book gives you all of the formulas that I have in about $700 worth of college text books. Admittedly, there is not much of an explanation for most the formulas, but I was still awed by the fact that most of my 4 years of college (OK 5 but who's counting?) could be condensed into one little book. Even better, every other page is blank so after you derive more useful or specific versions of a formula you have plenty of room to add it to the book.
Also in the photo above you'll notice the next item on the list.
This may seem silly, but I actually do consider this important. Back in college I always used plain old #2 pencils. I felt no shame in picking these up from the classroom floors in the evenings so I rarely had to pay for writing utensils. They were great for scantron style test forms (where you have to fill in the bubbles) because you could use a blunt tip and get nice even coverage. They worked well for written exams too , with the exception that they often blunted too quickly. You could see this in my exams as the writing would start out with nice even lines and then slowly decline into broad graphite swaths. Then I would have to get out my pocketknife (occasionally frightening TAs who led overly sheltered lives) and touch up the pencil. The cycle usually repeated several times an hour.
I will sharpen no more!
A 0,5mm mechanical pencil provides a consistent, thin line that is perfect for doing sketches. Better still, there's no time wasted touching up the tip on your pencil (which is important when you're transcribing data in a hurry.) Of course you better remember to carry extra graphite or you'll be in a real bind, because it's often hard to find the 0,5mm in many storerooms.
What good is a pencil with nothing to write in?
If you're trying to look important or you're filling out forms on the go, a clipboard may be more your speed, but sooner or later most engineers are going to need an actual book to keep track of their information.
It used to be common to take these to a notary at the end of each day or week and have each page stamped to certify that you had generated the ideas on the date shown. Now that we have so much electronic communication, there are plenty of timestamped records to document what we say and do. Still, the log book is indispensable for keeping track of your actions in the field or your experiment, because if you're working around heavy machinery or in dirty environments, you just can't walk around with a computer.
I should note, however, that when you work in a manufacturing environment it's best to make sure your log book has a few battle scars. Walking into a machine shop with a pristine logbook is like showing up in a white shirt and kakis. You'll look like you never do any work. Cuts, grease stains, and smudged fingerprints are all appropriate methods for breaking in your log book.
I have yet to meet an engineer that does not rely on a calculator at least part of the time. Since the introduction of the first electronic pocket calculators in 1970, scientists and engineers alike have been relying upon them to process data more quickly and efficiently. Of course there are always concerns about computational errors, but these are possible with mental and manual calculations too. With today's reliable electronics, the only likely cause for calculation error is G.I.G.O.
Powerful graphing calculators are increasingly common even among high school students. They are probably overkill for most people, but having a programmable, equation graphing, formula storing, and upgradable calculator comes in handy when you're having to do some mental and mathematical thinking.
Personally I like my HP 48GX. I've had it for more than 10 years, and it has served me well despite an occasional ding or dent in the case. What's special about this calculator is that it's designed to work primarily in Reverse Polish Notation (RPN)
What? you've never heard of it? Most people haven't, and most people won't believe me when I say that it's just as easy to use as a standard calculator. In fact, I find that it's even easier to program.
Still, some people can't get used to using a calculator without an = key so I carry around a backup calculator which I frequently lend to people who can't figure out how to use the good one.
And I do mean THE catalog.
If you haven't seen the McMaster Carr catalog then you need to go here immediately. This catalog has everything but the kitchen sink. Wait, never mind, those are on page 1965.
The only problem I have with this catalog is that it makes it too easy to become a catalog engineer. There is a solution to most of your engineering problems in this book and it is much too easy to get in the habit of opening the catalog every time you are looking for a gadget to fix one of your problems. Still, it's a very handy thing to have on the shelf.
If you carry a toolbox anyway, you don't need one of these. (Though I'd be willing to bet that you have one anyway.) Multitools, be they Swiss Army knives, Leatherman tools, or some similar knockoff product are an important tool for everyday life, but I've found that they are equally important as a tool for engineers.
They aren't really suited to heavy work, but they will occasionally save you from taking the time to find a screwdriver or a set of pliers. They're also very good for what I consider to be 'parlor tricks' in which you run across an unusual problem and solve it with only what you have in your pockets. (Hopefully an appreciative audience will be present.) This sort of thing doesn't really reflect upon your ability of an engineer, but it can do wonders for your reputation among mechanics who think engineers can't turn a wrench or less creative individuals that don't like to get their hands dirty.
And with that we move on the the last (and perhaps somewhat facetious) item on the list.
I cannot sing enough praises of this little device. Whether it is a travel mug, demitasse, insulated mug, tall mug, short mug, or plain old standard issue ceramic model it is something no engineer should be without. It helps me wake up in the morning, it can carry a cheerful (or pithy) message, it provides refreshment, and an excuse to get up for a walk to the coffee pot (or to the porcelain one.) I usually use an insulated mug with the company logo on it because it keeps the coffee warm through entire meetings or late into the afternoon when everyone else has stopped drinking coffee and the pot has been turned off.
Of course, I am almost never without the typical ceramic mug. It's a nice, simple, functional design. Plus, it serves a vital purpose! It leaves a very specific kind of stain on your engineering drawings. How else are you going to convince people that you stayed up all night working on them?!
Bonus item: The portable planner. [+/-]
I needed a way to plan my daily tasks, keep track of things on my to do list, store useful contact information, hold business cards, keep receipts, plan trips and record my daily activities. Oh and all of this needs to fit in my back pocket, or else I won't be able to keep it with me when I need it. As usual, I put together my own solution to this problem.
The leather cover is from an At-A-Glance calender, with an elastic band added to hold it closed when it's not in use. Inside I've added my own favorite calender (cut down to fit neatly inside.) The back of the calender has room for post its and miscellaneous information. Phone numbers and other contact information are written inside the front cover. A clear plastic sleeve (like you use for a passport) is stapled to the calender's cover. That's where I keep my to-do list. A scratch pad sits in the pocket on the left, I use it to plan my day's activities. The receipts and business cards go in the pocket behind the scratch pad. This thing even holds a pen.
Generally when I need to do something, it goes on the to do list. When appropriate I transfer it to my daily list on the left and scratch it off of the original list. At the end of the day I tear off the daily list and either move things to the next day or log them in my calender. It has the advantage of not only keeping track of the work I have to do, but allowing me to track of the tasks I've performed on any given day. You wouldn't believe how often it comes in handy, and as far as I'm concerned, this is more effective than a pda or smart phone, because I never have to charge it (though I do occasionally get new pen cartridges)
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