The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Wildlife

Other creatures in our world

  • Dry Ice Sublimation Rate

    For reasons I’m not at liberty to discuss, we had a cooler of dry ice pellets in the freezer for a few days. I used about a pound of it a time to mumble.

    I started with “10 pounds” of dry ice in a half-pound Styrofoam container with 1.5-inch thick walls; the total weights include the container. For what it’s worth, dry ice costs $3.50/pound under 10 pounds, then $2.75/pound over that. It used to be plenty cheaper in the old days, evidently, but everything else was, too.

    In between withdrawals, the cooler sat in the freezer and and the dry ice quietly sublimated; here’s how the weight varied between uses.

    Starting weight: 9.2 lb gross, so I lost quite a bit in transit. Which, as it happened, was about half an hour in a bike trailer during a rather hot afternoon.

    A) 7.2 to 6.7 lb -> 0.5 lb / 15 hr = 0.033 lb/hr

    B) 3.8 to 3.0 lb -> 0.8 lb / 11 hr = 0.072 lb/hr

    C) 2.7 lb to 2.0 lb -> 0.7 lb / 11 hr = 0.064 lb/hr

    I’m suspicious of that low number for the first stay, too. Maybe a side effect of having the cooler’s cavity nearly full of dry ice? Or the freezer ran defrost cycles for the other two?

    Anyhow, to a back-of-the-envelope resolution the cooler loses a bit over 0.05 lb/hour of dry ice. Call it 15 hr/lb.

    The temperature of sublimation is, according to Wikipedia, -109°F. The freezer is around 0°F: a differential of 109°F across 1.5 inches of Styrofoam. Assuming the cooler foam has R=4 with units of (ft^2·hr·°F) / (BTU·in ) and an internal surface area of 304 in^2, the cooler leaks heat at 38 BTU/hr. Call it 11 W.

    Cross check: Wikipedia says the enthalpy of sublimation at STP is 571 kJ/kg. Sublimating 0.07 lb = 0.031 kg requires 18 kJ (18 kW·s) and doing that over the course of an hour requires 5 W.

    Well, considering the rough-and-ready measurements and the fact that the freezer isn’t at STP and that I’m ignoring gas leakage and a bunch of other stuff, a factor of two error is spot on.

    If I were you, though, I’d double-check those calculations before leaping to any particular conclusions. Fair enough?

    When all was said and done, I found this thing in the bottom of the cooler. It wasn’t there when we started, soooo…

    Dry Ice Thing
    Dry Ice Thing

  • Chipmunks Discover Agriculture

    Chipmunk atop sunflower
    Chipmunk atop sunflower

    One of the sunflowers in the garden started swaying wildly, despite having no breeze at all. I though it was a goldfinch plucking seeds, but a quick look through the binoculars showed a brown furry tail hanging below the topmost seed head, about five feet off the ground.

    Mary reports that this is one of five sunflower plants growing in a tight group near the garden fence; she thinks a chipmunk’s seed stash sprouted. This could be the start of something big: next thing you know, they’ll be planting seeds and harvesting crops!

    As we watched, the critter’s cheeks became more and more distended.

    Chipmunk stuffing cheek pouches
    Chipmunk stuffing cheek pouches

    Eventually, however, gluttony overcame common sense.

    Getting the last seed
    Getting the last seed

    Seconds after the shutter clicked, the sunflower head disintegrated, depositing the chipmunk on the ground with a rustle and a soft plop.

    No damage done, we’re sure, and that critter’s pantry should be stuffed full in short order. Next year Mary will probably do some extensive sunflower culling to get room for the rest of her crops!

    And, yes, the title is a riff on Bears Discover Fire…

  • GPS Position Jitter: Into the Drink!

    We spent the night aboard BB62 in Camden NJ, with our bikes lashed to a post on the dock. Follow the light-color brick track from the upper-left GPS point across the dock to the black dot marking a memorial stone: we tied up just to the left of that spot.

     

    Position Jitter - ZNU at NJ2BB-15
    Position Jitter – ZNU at NJ2BB-15

     

    NJ2BB-15 is the APRS digipeater aboard BB62 with an antenna high in the superstructure. While I didn’t have any trouble with RF reception, packet collisions pose a problem in a dense urban environment. For what it’s worth, essentially everything in the superstructure is an antenna; the NJ2BB ham shack is a wonder to behold.

     

    BB62 starboard side
    BB62 starboard side

     

    The point-to-point jitter is about 20 meters (18.52, says the GPS info dump), so you’re looking at the un-augmented GPS accuracy of a long-term stationary object. I’m sure there’s a slight registration mismatch between the satellite imagery coordinates and the GPS coordinates, enough to put the upper-left point across the dock.

    If you get the chance, take the tour. The guides are retired Navy, some served aboard BB62, and they take their storytelling duties very seriously. The bunk space, even with air conditioning, is claustrophobic at best; a tip of the bike helmet to you folks who live in these machines!

    [Update: Our daughter discovered three itchy bites in a line across her tummy the morning after spending a night in the bunks. That means BB62 has bedbugs, which you do not want to bring home in your luggage. As a result, I cannot recommend an overnight on BB62, alas. We wish she’d mentioned that before we got home…]

    [Further update: when I reported this to the folks at BB62, they had an exterminator check out the berthing spaces and conclude they have no bedbugs on board. That’s encouraging, but I still heartily recommend that you follow the same decontamination procedures that you should use after all trips.]

    It turned out one rider in our group was an active-duty Rear Admiral who, evidently, could (or should) have supervised the signal gun firing after Colors and Taps. She was traveling incognito, though, and didn’t stand on ceremony.

  • A Night Visitor

    One of those midnight “I heard such a clatter” events: somebody or something was kicking a can all over the driveway.

    Turned out that a raccoon found the stack of carefully rinsed salmon cans in the recycling bin and was puzzling over how to get them apart. Evidently he figured there was something really delicious hidden in there somewhere!

    I had time to fiddle with the camera before he gave up and wandered away on his rounds…

    These are in near-IR “Nightshot” mode with my ancient DSC-F717 and the 1.7X teleconverter. They’re automagic crops from larger frames, walloped en masse with ImageMagick:

    
for f in *jpg ; do mogrify -crop 1200x900+700+450 -resize 750x563 $f ; done

    The gritty texture plays hell with JPEG compression, but that’s what the camera delivers. An incandescent spotlight on the driveway contributes the deep shadow, but an ordinary camera (my DSC-H5) produced completely black images, even with the high-power flash setting.

    Memo to self: start keeping the recycling bin inside the garage. But will that just piss off the bears that are moving (back) into the county?

  • Red Squirrel

    Red Squrrel - front
    Red Squrrel – front

    I cleaned the compost out of the gutters yesterday and this critter came by to help with whatever missed the wheelbarrow.

    Squirrels and chipmunks show how far you can get with a snappy color scheme and a good PR agent. These things are rodents, pure and simple, but those large eyespots trip your protect-the-baby response every time.

    They’re not particularly well-behaved, either: the chipmunks and gray squirrels have had running battles with them this spring. We think the area’s chipmunks had a population explosion and are shoving into traditional red-squirrel territory. Could get ugly out there.

    Where are the hawks when you need ’em?

    Red Squirrel - side
    Red Squirrel – side

  • Chipmunk on High Alert

    The chipmunks are busy cleaning up all the maple seeds from the driveway, but, being chipmunks, they like to stay near a safe spot.

    The absolute best spot to watch for danger seems to be the 4-inch PVC pipe I attached to the garage downspouts: you can see out, but when a threat appears you can run up the downspout!

    [Update: the Cooper’s Hawk just swooped on a red squirrel, missed, and landed on the patio railing as the rodent vanished up the pipe.]

    Chipmunk peering from drainpipe
    Chipmunk peering from drainpipe

  • Too Many Deer: Another One Bites The Dust

    One Less Deer
    One Less Deer

    Sat down for some tech reading in the Comfy Chair one morning and spotted a lump near the road, at the foot of the deer crossing warning sign.

    While I don’t know if this deer was one of that group, it’s a fair bet.

    There was no freshly smashed glass or broken plastic in the area, which indicates a relatively low-speed collision, the kind where the deer’s legs snap against the bumper and the body rolls over the hood, crushing sheet metal and deforming plastic frippery along the way.

    Many cars display that kind of damage around here. They look as though somebody walloped them with a huge sandbag, which is pretty much the case.

    The animal huggers seem strangely silent about such events. If they had the courage of their convictions, they’d subsidize drivers (and gardeners) affected by the deer overpopulating the area. But, no, they never offer to do that.

    I did find this in the driveway across the street…

    Deer Whistle
    Deer Whistle

    Before equipping your car with such gimcrackery, read that.