June 2022 – Shop Finds

SkyCam

Posted on June 25, 2022July 28, 2022 by Brian Garthwaite

Astronomy can be awkward. By necessity, observation happens at night. (Mostly.) And outside, in whatever weather permits clear skies. Hot and humid or bitter cold, the telescopes only function when they’re at equilibrium with the air around. When the temperature drops so low that the grease in the motorized mounts thickens, we call it quits, but nights reaching down to about 20°F are fair game. Precipitation always shuts things down, as does substantial cloud cover.

What to do when you’re at home, all warm in your jammies, and not sure if it’s worth trekking out into the cold? Check the Bucknell University Sky Camera website, of course. If it looks like this:

Camera image, night — *I see stars! And light pollution!*

Visible stars, no serious cloud cover: you’re good to go. The bright spot in this particular image is probably Saturn, but you get the idea. If you can see it here, you can see it through a telescope. Checking the weather forecast is fairly reliable, although it gets dicey around those transition zones between “good enough” and “should have stayed home.” Forecasts also describe cloud cover in terms of percentage obscured, without a distinction between sparse-but-dense and widespread-and-gauzy.

Depending on what you want to accomplish, sometimes clouds are something you can work with. Astrophotography? Visual observation? Naked eye and constellations? Sometimes, here in a Pennsylvania river valley, you shrug and make it work.

(The alternate method is to walk outside and look up – quite reliable, that – but maybe not ideal if you’re in the aforementioned jammies.)

Camera image, day — *Note: one particular star* ***very*** *visible.*

The skycam can also be entertaining to check during the daytime. You can watch the sun track across the ecliptic and see the discrepancy between clock time and solar time during Daylight Saving Time. On a cloudy day, sometimes the clouds themselves are just plain neat. Raindrops. Snow accumulating. Snow melting. Birds and bugs and all sorts of things captured by intermittent photography.

Including the occasional technician out on maintenance duty. Wave hi!

Screw Chek’r

Posted on June 22, 2022July 28, 2022 by Brian Garthwaite

Thread size check plate — *“Chek’r” shows their foresight for SEO way back in 1960.*

One of the ever-unfurling mysteries in the shop is this: what screw thread am I looking at? There are a multitude of reasons to pick one when designing an object, and while we’d all love for simplicity and consistency across a single piece of equipment, that’s not always the case. Hence, a precision-made piece of steel. Holes, smooth and tapped.

Smooth bores identify the screw size – SAE number standard or fractional inch – and are all marked with the corresponding drill size. For size 4 screws, number 33. For 1/4″ screws, a convenient 1/4″. In a moment of serendipitous coincidence, size 10 fits in a number 10 hole. All are marked in the right column with their diameter in decimal inches.

The threaded holes come in three flavors: N.C., N.F., and N.S. Sometimes N.S., at least. National Coarse, National Fine, and National Special.

Coarse threads are standard, and like all SAE threads indicate the number of threads per inch. (Metric threads use the pitch, or the center-to-center distance between threads.) If ever unsure, the answer is that it’s probably coarse thread. Double-check by seeing if it turns neatly into the hole.

Fine threads have certain uses, such as in locations where there will be a lot of vibration. More threads per inch means more contact area for the screw, and the increased friction helps reduce the screw’s ability to wiggle loose. For some reason, they never seem to wiggle in more securely.

Special threads show up in special situations, and are completely inconsistent across the range of sizes. Most are even finer threads, but #4-36 is even coarser, and #6-36 sits in between coarse and fine. Small fractional inch sizes don’t have special designations, and the small number sizes don’t… except for size 1.

Which is an uncommon screw size, to say the least. If we have any in here, they’re hidden away in some dark drawer. We do have a single #1-64 tap, so either they were around for a little project once, or a previous shop tech was very thorough in ordering tools.

Inspecting the Screw Chek’r more closely, you might notice that one of the tapped holes isn’t like the others. Several feel as though they’ve gotten a lot of use over the years – #4-40, #6-32, #10-32 – but poor, lonely #1-56?

No one has ever tried to thread a screw through that hole. There’s still a steel burr in the bottom.

It makes some sort of sense. #1-56 screws are rare as hen’s teeth these days. McMaster-Carr doesn’t carry any, and they have seemingly everything. A quick internet search will turn up hobbyists repairing early-20th-century equipment trying to locate replacement screws in that size. Even a glance at Ruelle Industries’ most recent versions of the Screw Check’r reveal that they don’t even put that thread size on anymore.

Of course, if you can’t find the precise screw you need, that’s what a metal lathe is for…

Cobalt-60

Posted on June 16, 2022July 28, 2022 by Brian Garthwaite

Radioactivity makes people squirm. It’s not hard to understand why. Whereas most potential dangers offer some sensory warning, radioactive materials don’t. For the most part. If your senses are picking up the direct effects of radiation, you are long past any level of safe exposure. Somehow, things have gone quite sideways for you.

But this is introductory Physics lab, and we’re here to learn in a safe environment. We’ll stick to sources that keep below the United States Nuclear Regulatory Commission’s Exempt Quantity Limit. That’s readily available in the table from § 30.71 Schedule B, which indicates the limits in microcuries [µCi] for a wide range of nuclides. In our labs, we use cobalt-60 and cesium-137 for different purposes, though you can have fun reading through the entire table to remind yourself that dysprosium, hafnium, and samarium are all on that periodic table, too.

Lots of elements struggle to become household names. Maybe it’s for the best that most of don’t have to concern ourselves with the particulars of terbium on a daily basis. (It’s key to creating the green phosphors essential to fluorescent light, so now we’ve all learned a new factoid.)

We use these little 1-inch disks as relatively constant reference sources in labs. The disk, of course, is way bigger than the tiny chip of cobalt inside, which randomly decays into a stable isotope of nickel-60, spitting out a beta particle (an electron) and some gamma rays (high-energy photons). While it’s impossible to predict when any specific atom will decay, a sufficient quantity of them all bunched up together result in an output that’s mostly predictable. In any given second, you might hear several (or zero) clicks on your Geiger-Müller counter, but if you count them over longer intervals, the clicks-per-interval numbers get awfully close to each other.

With a half-life of 5.27 years, one little disk of cobalt-60 can handle years of students labs. While we wait for Physics 212 to roll around again, they bide their time in this little box:

We keep it way in the back of a locked storage room. It’s lined with lead on the inside, even if that’s not strictly necessary. You probably shouldn’t stuff a bunch of cobalt disks in your pocket for the day, and you definitely shouldn’t eat any. (Physics labs don’t typically use edible materials, and even when we do – such as non-dairy coffee creamer – we mark them as not for consumption. Just don’t eat anything in the lab, okay?) It does keep everything in one easy-to-find place, though, and big CAUTION stickers tend to keep curious fingers out.

We use big, scary yellow CAUTION signs in the shop to keep curious fingers away from sharp objects, too. Sharp and poky things are way more likely to ruin your day around here. So be careful, please.

Plans

Posted on June 14, 2022July 28, 2022 by Brian Garthwaite

Tucked away in a back corner – we have so many of those – sits a set of the architectural plans for the Tressler Observing Laboratory from 2014. What had once been an exterior deck is now, thanks to a very generous gift, a fully enclosed structure housing six telescopes. On a good night for observing, or astrophotography, or simply appreciating the wonders of the cosmos, the building’s roof slides away, revealing the night sky. It’s a neat trick.

The plans are a (recent) historical artifact, a little water-damaged, but still fully readable. Nothing much in here you can’t just walk over and see in person, of course. For those with an architectural inclination, though, skimming through detail drawings is an always-interesting pursuit.

Hastings Triplet

Posted on June 10, 2022July 28, 2022 by Brian Garthwaite

We field a lot of requests for small objects in the shop these days. It’s not that there aren’t plenty of big/huge/enormous things worthy of serious research and scholarship (see: stars), but physics sometimes gets wild when you go small. And not even quantum mechanics small… that’s where calling physics not intuitive doesn’t even begin to cover it.

We’re talking channels and structures where 100 microns makes a difference. A micron, or micrometer, is one-thousandth of a millimeter; 100 of them is a tenth of a millimeter. In the general ballpark of the width of a human hair. It’s the scale where you learn the finer points of a tool’s tolerances, where you set a machine to do the work and wait until it’s all finished to figure out if it worked.

Mistakes happen.

Very tiny things also defy your eyes’ ability to inspect them, so we rely on microscopes and other optical magnifiers to check on the quality of work. One of the handiest is the magnifier shown above, a Bausch + Lomb Hastings Measuring Magnifier. It uses a Hastings triplet lens system, composed of three separate glass lenses bonded into a single, composite lens. Doing so produces crisp, distinct images without distortion. At the end it has a scale, so that we can press it against an object to inspect and actually measure features less than a millimeter across!

View through loupe — *Very small. Very small.*

One of the best features of this magnifier is its portability. At 7X magnification, it’s less powerful than a microscope, but its case fits in a pocket, so it can go anywhere. Clear plastic sides admit plenty of ambient light, removing the need for additional illumination that a microscope requires. You simply pick it up, inspect your object, and carry on. Confirm that microfluidics channels are the proper width. Ensure that you’ve cleaned all the swarf away from tiny features. Examine tools up close for minor damage to their edges.

Or check out the tiny world all around you, just because you can. Some of the best science starts with noticing something neat, and just digging deeper.

Trig-O-Matic

Posted on June 6, 2022July 28, 2022 by Brian Garthwaite

With enough drawers, boxes, bins, and dark corners in our shop and storage rooms, you’re bound to run across the occasional tool that you wish you’d known about sooner. Maybe it’s useful. Maybe it’s fiercely specific. Maybe it’s just a special sort of ingenious. Maybe it’s a pair of squeeze-and-strip wire strippers.

We have several pairs, but only this one is dubbed the Speedex TRIG-O-MATIC. Nothing like a glorious Space Age name to capture that little extra bit of attention.

Feed an insulated wire through the clamps – or several, once you’ve had a bit of practice – up to the adjustable guide. As you start to squeeze the handles, the left-side clamps gently grasp the wires, holding them steady. Then the notched blades close, cutting through the insulation surrounding the wire. The last step in this little dance splits the tool down the center, pulling wire and insulation in opposite directions, effortlessly.

Cleanly stripped wire, courtesy of the two ugliest birds you’ve ever seen. (What two-headed oddity do you see in that picture?)

At this point, you may be wondering when a relatively complicated gizmo like this would be worth having. After all, it has a lot of moving parts, and the more parts something has, the more parts it has that can break. A pair of basic wire strippers, or even just a pair of pliers with wire snips can do the job quickly and cleanly. Right? Well, there are two situations when this little tool is just the bestest thing ever.

1) When a novice needs to strip a few wires and doesn’t need to spend the time (and mistakes) to learn good, practiced technique. We were all there once.

2) When it’s time to put together toy kits for PHYS 212, and all of those lengths of wire* – each with two ends! – need to be stripped and tied. After a while, you get very good at clipping several at once, until it becomes a game to see how many you can manage. Yes, there’s a ceiling.

Toy kits! A subject for a future post: each semester, we put together hundreds of packs for the PHYS 211 and 212 students, full of odds and ends to use for problem sessions. They’re wondrous assortments of odds and ends (and honest-to-goodness toys!) that illustrate the principles of physics through just being neat-o.

* Cutting hundreds of pieces of wire to a specific length is its own problem, and there’s a shop-made solution for that. If you have to do a job a dozen (or a couple hundred) times over, build a jig!

Fulgurites

Posted on June 3, 2022 by Brian Garthwaite

Box of petrified Jersey lightning — *“Petrified Jersey Lightning”*

We have multiple storage rooms, each with shelves, cabinets, drawers, and seemingly endless places to tuck away small objects. It’s easy, so easy, to simply forget something. Then, years later, someone else gets the joy of stumbling across it.

Sometimes it’s a century or more.

Petrified Jersey Lightning

Fulgurites from South Jersey collected by John G. [unknown]

Presented to Physics Dept 1/14/10

That would be January 14th, 1910.

Fulgurites are a mineraloid formed when lightning strikes the earth and fuses mineral grains. They come in as many varieties as there are different types of soil, and as we’re in Physics, not Geology, our understanding of the particulars is as reliant on Wikipedia as yours.

We can only guess as to why John gifted Physics with these 112 years ago, but we appreciate it. Everyone should have the chance to stumble across a little petrified Jersey lightning from time to time.

Month: June 2022