What I Learned Today

When the contractor tore off my old shingles to replace my roof, they found that underneath were the original wooden shingles. California code no longer permits wooden shingles (fire hazard!), so these had to come off, too. But the wooden shingles were laid on slats with 6-inch gaps between them, so that meant I also needed a layer of plywood put down to support the new shingles. California code (at least in my town) also requires that this plywood be radiant barrier plywood, which is plywood with a foil backing on one side. You lay the plywood shiny-side *down*, and then in theory it reflects heat back up through the shingles, reducing what gets into the attic.

My contractor was skeptical as to whether this plywood would really make a difference, but agreed to install it per code. (It is also not much more expensive than regular plywood.) Naturally, I wanted to test it empirically. So I collected some data.

My SCE smart meter reports the maximum daily temperature and my energy consumption per hour online. I have my thermostat set to 85 F during the day, and I can track when the air conditioner came on by looking for a spike in energy consumption. I defined the hour at which the A/C came on (i.e., internal house temperature reached 85 F) as an hourly consumption greater than 1 kWh. In the following plot, I show the time when the A/C came on as a function of maximum outside temperature. Higher values are better (later in the day). And sure enough, the new roof out-performs the old one.

Note that I used a linear fit here, but that probably isn’t appropriate at higher temperatures. Also, the times are capped at 18:00 (6 p.m.) as that’s when my thermostat switches to “evening” mode and tries to drive the temperature down to 82 F instead of 85 F.

Caveats: this is the result of the roof as a package, not just the plywood. I also had attic vents installed that probably help keep the attic cooler. It’s also possible that I’m seeing more of an effect than others might, because as far as I can tell my house has no insulation in the ceiling (California!). Thus, the living space and attic are more coupled than they would be with insulation.

Overall, however, I’m pleased to see that my new roof is performing so well! The only down side of the radiant barrier plywood is that it came with an intense chemical smell that soaked down through the attic into the living space and, on hot days, was so bad that I had to turn off the A/C so I could open the windows and tough out the heat just to be able to breathe. I couldn’t access the attic at all. Happily, after about three weeks, this finally faded away. The manufacturer claims this is due to the glue in the plywood.

I love fixing things. So imagine my delight when today I finally tore open a wall clock that stopped running years ago and got it working again. This clock has been stopped for so long that I’ve lost the habit of even looking at it, yet I’m so fond of the thing that I haven’t had the heart to replace it. (It was one of the first decorations I added to my first grad school apartment.) I’d previously given up when replacing the battery didn’t do the trick.

This clock has a simple time piece stuck to the back of it. I examined its mount and then carefully pried it off, at which point the hands fell off their spindle and clattered to the bottom of the front of the clock (it has a plastic enclosure). I couldn’t tell if that had destroyed anything, but since I had nothing to lose, I pressed on. I pried the time piece apart so I could get at the inside, which featured a bunch of flimsy plastic gears, a tightly wound spool of copper wire, and a tiny circuit board. I pried this up to see the circuit board, at which point the gears exploded off their mounts and went flying.

Nothing seemed obviously fried or broken with the circuit board, so I decided to try reassembling it. Because I hadn’t taken a picture of their arrangement, I then spent several minutes puzzling out the mechanical logic of the seven (!) interlocking gears (two are underneath in this shot). This is not the correct solution. This is the picture I took after reassembling them the first time (which I thought was correct). Everything fit together, and it started ticking (hooray!), and the little gears all started turning at different rates. But right after taking this picture, when I snapped the case on top, I heard a SNAP and then a little rattle when I moved the case. I was sure I’d broken some vital plastic bit. I opened it back up and found that one of the plastic stand-offs was broken. However, it didn’t seem vital, so I pressed on. The rightmost gear in this shot is the one that’s wrong. I finally figured out that it goes underneath the platform (it’s the gear that lets you manually set the time). The gear that drives the ticking is on the far left.

Encouraged, I snapped the case on, and it was still ticking. I then disassembled the front of the clock to get at the hands. I mounted the time piece to the back of the clock frame, took the battery out (it stopped ticking), stuck the three clock hands on the spindle axis in the correct order, and set them to point at 12:00:00. I twisted the dial to manually set the time, stuck the battery back in, and IT WORKED!

So basically, I didn’t learn anything about what was wrong or how to fix it, except that (as sometimes happens), just taking the thing apart and putting it back together did the trick. The fun part was figuring out how to get in, and then how to fit everything together. It’s possible that some dust had wedged in there or some of the tiny gears were just slightly not touching or the battery leads weren’t making the right contact. I favor the latter hypothesis since I couldn’t hear any ticking. But either way, it works now!

Ever wondered how a Swiss Army knife is put together? Wonder no more!

This is just one of a whole pile of fascinating “How It’s Made” videos put out by the Science Channel. Here’s another great one about how thermometers are made:

In these thermometers, they use an unspecified blue liquid (to avoid toxic mercury) that expands and contracts with temperature. The calibration process is fascinating (and surprisingly manual).

I’m already having trouble dragging myself away from this site! Enjoy!

OSU offers a course called ME 412: Design of Mechanisms. Sadly, it is only offered during the winter term, and I am here for the fall term. So I contacted the professor to find out more about what sort of books and other materials the course uses, for my own investigation. Imagine my delight when he gave me a copy of the latest edition of the textbook and sent me on my way!

This textbook, Design of Machinery, may well be the best textbook I’ve ever read. Really. Unlike some books that pay lip service to being clear and accessible, this text really is clear and accessible. It is also annotated with lots of amusing cartoons and very clearly illustrated examples — the latter being crucial since we’re talking about physical devices and how they move. The book comes with a DVD with animations that I haven’t been able to play with, since it is Windows-only. But, of course, there are linkage animations galore online. And even better is building them yourself, physically.

Chapter 1, “Kinematics of Mechanisms,” is charmingly written and touches on the broader subject of what it means to be an engineer, and how one of the biggest challenges is learning how to “structure the unstructured problem” to go from a concept to a problem definition to a solution. One tip the book offers is to use “functional visualization” (meaning, focus on the desired behavior of the solution, but no one kind of “embodiment”) so as not to limit your creativity and be restricted by a specific kind of solution early on. It also encourages you to make cardboard models of linkages that you design (as above) — a philosophy I think makes a lot of sense.

The chapter also includes the text from a paper given by George A. Wood Jr. titled “Educating for Creativity in Engineering.” Two of my favorite quotes from the paper are, “To me, the creative moment is the greatest reward that the profession of engineering gives,” and “If a person decides to be a designer, his training should instill in him a continuing curiosity to know how each machine he sees works.” Yes! Yes!

On a more concrete level, I learned that kinematics is “the study of motion without regard to forces,” while kinetics is “the study of forces on systems in motion.” The first half of this book focuses on kinematics, reserving forces for the second half. I can already tell that kinematics alone provides ample material to keep me busy!

“Once you become familiar with the terms and principles of kinematics, you will no longer be able to look at any machine or product without seeing its kinematic aspects.”

It’s already happened. At a conference last week, after ironing a shirt in my hotel room, I sat down and drew my first kinematics diagram — of the ironing board.

I’ve already started working through Chapter 2, “Kinematics Fundamentals,” which is fascinating but slower going, as it’s dense with new information, terms, and concepts for me. But I’m already impatient to get to the end of this chapter, where there are 15 pages of problems to do! Starting with… drawing kinematics diagrams of familiar objects like ironing boards. Ooops, jumped the gun on that one!

I recently had the pleasure of seeing tea being made into tea bags, right before my eyes! While in Boulder, CO, for a conference, I stopped by the Celestial Seasonings tea factory. They have not only a wonderful gift shop but also a free tea-tasting bar filled with great art and a free tour of their factory facilities.

After donning a hair net (plus beard net for whiskered men), we entered the factory and got to see black tea being milled (chopped up), filling the air with the most delicious odors. We walked past bales of herbs piled to the ceiling, filled with hibiscus and chamomile and tilia and all sorts of other things. We entered the tea room, where actual tea (black, green, and white) is stored, and then the “world famous” mint room, which of course is filled with mint. It turns out that a room full of mint bales, kept closed 99% of the time, builds up an overpowering mintness. Two feet into the room, my nose started to tingle and then burn faintly. I couldn’t get back out because of the flow of people coming in, so I edged over to the spearmint side of the room since it was less painful than the peppermint side.

Next we entered the main assembly room floor. This was so awesome I’m having trouble putting it in words. It was heaven for any tea-loving geek — like Willy Wonka’s Chocolate Factory, but with tea! Little conveyor belts sent half-assembled boxes of tea zooming around the room, pausing to be folded or stamped or sealed or wrapped in plastic, all by amazing automated machines. I wanted to stop and stare and figure out all of their gears and mechanics, but the tour kept pushing onward. Perhaps most intriguing was their “Robotic Palletizer”, which picked up packed cartons tea boxes in groups of six and stacked them precisely on a pallet. Later I saw the whole pallet being spun so it could be wrapped in plastic, a 6-foot stack of tea cartons all wound up like a cocoon. I could have spent the whole afternoon watching this busy, enchanting process.

Right there at the factory, the various herbs and constituents are magically converted into a lovely beverage experience. They mill, mix, and bag the tea (using unique no-string teabags so as to save frightening amounts of paper), then deposit the bags into boxes that are sealed and sent off for distribution and sale. You can get some glimpses of this geeky awesomeness through the Celestial Seasonings virtual tour; click on the tea cups marked “3″ and “4″. Enjoy!