Category: Science

If you measure something often enough, it becomes science

Polydryer Humidity: October

Another month of data from all those Polydryer boxes:

	7 Oct 2025			8 Oct
Filament	%RH	Weight – g	Wt gain – g	%RH
PETG White	28	26.6	1.6	19
PETG Black	25	26.6	1.6	20
PETG Orange	29	26.6	1.6	21
PETG Blue	23	26.7	1.7	15
PETG-CF Blue	26	26.6	1.6	23
PETG-CF Black	23	26.4	1.4	20
PETG-CF Gray	30	26.5	1.5	26
TPU	28	26.3	1.3	27
Empty 1 → White	35	26.7	1.7	37
Empty 2	36	27.1	2.1	24

The “PETG White” spool in the top line is nearly empty, so I loaded a new spool into the “Empty 1” box.

The “Empty 1” 35% value on 7 Oct matches the other empty box, the desiccant having pulled the humidity down from the 51% basement level. The weight of the water pulled out seems low compared to “Empty 2”, as they both started with a fresh batch of basement air while changing the desiccant in September.

They’re again filled with 25 g of alumina beads, although I’m beginning to think silica gel does a better job.

A picture of the boxes, thus avoiding WordPress reminding me pictures improve SEO:

PolyDryer PC4 Fitting - Prusa MMU3 setup — PolyDryer PC4 Fitting – Prusa MMU3 setup

2025-10-09

Belkin F6C1500 UPS Re-batterying

After about four years, the two well-aged 12 V 9 A·hr batteries in the Belkin F6C1500 UPS gave up after a few minutes without line power, whereupon I swapped the UPS out for a new one.

The old batteries don’t have much life left in them (the date in the title should be 2021):

SigmasTek 12V SLA -2025-09-30

That’s with a 1 A load, rather than the 2 A I used earlier, as they’ll never be used for heavy loads again.

The new 7 A·hr batteries can power a 300 W incandescent bulb for 10 minutes before sounding the Low Battery alert, then another three minutes before shutting down. That’s about 12 A at 24 V, call it 2.6 A·hr from grossly overstressed batteries.

2025-10-08
Fitbit VO2Max Estimation

My Fitbit Charge 5 exercise tracker estimates my VO2Max as somewhere between 51 and 55. That seems absurd for a guy of my age, where “Excellent” is a bit under 40. I am most certainly not a highly trained athlete at the top of my form, so I wondered what the real value might be.

Fitbit calculates VO2Max from the ratio of my maximum to resting pulse rates, probably according to the Uth formula using a coefficient applicable to a much younger man.

It also computes my maximum heart rate from my age as 220 – 72 = 148, much lower than the values I routinely see while biking around the area. Reviewing a few months of data suggests an actual value around 170, although I did see 185 on one occasion.

Forcing a maximum heart rate of 170 changed the VO2Max estimate to 50-54, which still seemed absurdly high. At least that change made the Fitbit’s “heart rate zones” a little more reasonable, as ordinary bike rides no longer have me in the Peak zone nearly as often.

The Rockport walking test calculates VO2Max from a timed walk over a one mile “track” course, so I laid out a half-mile out-and-back route on Zack’s Way, which is a quarter mile from home.

Maintaining a brisk pace covered the mile in 15:49 and left me with a 110 pulse; it’s obvious I’m not a trained athete. Feeding those numbers and a few other vital details into the Rockport formula gives me a much more realistic VO2Max of 28.5, putting me somewhere between the 50th and 75th percentile.

Which is good, but not extraordinary.

Bottom line: don’t believe the hype.

An obligatory picture and link for enhanced SEO:

FitBit Charge 5 stand – installed

2025-10-01

Polydryer Humidity: Another Month of Data

The 25 g of silica gel in each Polydryer box produced these results after a month:

	8 Sept 2025			11 Sept	23 Sept
Filament	%RH	Wt – g	Wt gain – g	%RH	%RH
PETG White	25	27.6	2.6	15	21
PETG Black	22	27.3	2.3	15	20
PETG Orange	21	27.2	2.2	21	23
PETG Blue	19	27.3	2.3	14	15
PETG-CF Blue	24	27.4	2.4	21	22
PETG-CF Black	21	27.3	2.3	15	19
PETG-CF Gray	27	27.1	2.1	24	26
TPU	25	27.4	2.4	22	24
Empty 1	51	no gel	n/a	27	30
Empty 2	35	27.9	2.9	19	28

The humidity levels seem higher than before, with a bit under 10% weight gain.

The two “Empty” boxes show the difference between ambient basement humidity and letting 25 g of silica gel work on the box for a month. Comparing the latter’s weight gain with the other boxes shows occupying (much of) the interior with (relatively) dry filament reduces the desiccant’s workload.

The beads in the “Empty 2” box were definitely darker after soaking up an entire box full of 50 %RH air:

Polydryer - 37%RH meter - empty — Polydryer – 37%RH meter – empty

The meter reads 37%, rather than 35%, due to being out of the box for a few minutes.

They’re the darker swirl in the pan of beads:

Silica Gel regeneration - starting bead colors — Silica Gel regeneration – starting bead colors

That’s an accumulation of beads from a few months, not just what you see in the table.

I used an induction cooktop to heat the cast-iron pan. Some fiddling with the cooktop’s constant-temperature mode got the beads to 200 °F with a 460 °F setting in about an hour. Setting the cooktop to 50% in constant-power mode worked better, as the beads reached 220 °F in an hour and 230 °F after another hour.

The bead weights at various stages:

Start = 531 g
+1 hr at constant temperature = 491 g
+ 1 hr at 50% constant power = 483 g
+ 1 hr ditto = 480 g

The 41 g weight loss is 8.5% of the dry weight, roughly what you’d expect from the humidity readings.

After reloading the meters with 25 g of alumina beads, the 11 Sept humidity readings are slightly lower and the 23 Sept readings are roughly comparable.

2025-09-26

All’s Well Who Ends Well

Eventually this happened:

Negative COVID tests

Three weeks, more or less, from my exposure to clearing the hurdle. Mary, being tougher than I, got it done in two.

For the better part of the first two weeks I was in bed ten hours every night, plus an hour or two of afternoon nap (no milk & cookies, drat), plus dragging around the house getting nothing done.

No major health problems, good blood oxygen levels throughout, no loss of smell apart from what you’d expect during three days of complete nasal blockage, and we’re both feeling OK-ish now.

However, we are making more than the usual number of stupid mistakes, which is one way we know we’re not really OK yet.

Back to the Basement Shop, with considerable caution …

Memo to Self: That was the first time in four years you didn’t wear a mask in close quarters. Don’t ever do that again.

2025-09-23
Wasp Blower: Carnage

The day after I set up the Wasp Blower, the carnage was terrible to behold:

Wasp Blower – carnage

Two weeks later, the blower is chopping up two or three wasps each day.

As far as I can tell, the blower killed essentially every wasp leaving the nest and most of the returning foragers:

Wasp Blower – shattered wasps

After two weeks, (nearly?) all of the eggs remaining in the nest have hatched, the larvae / pupae have starved for lack of incoming food, and I’ve put out ant bait traps to discourage scavengers.

The plan is to keep running the blower until a week goes by without any kills, then seal the crack under the door sill.

I have no idea how the queens (Yellowjacket wasp nests have multiple queens!) are doing in there, but they must be getting pretty hungry and, we hope, will not survive the winter.

This makes me feel awful, but not nearly bad enough to regret dealing with the critters.

2025-08-28
Switchyard Hum

For reasons not relevant here, I walked along IBM Rd to the end of Sand Dock Rd and back, passing the switchyard serving the IBM Poughkeepsie site:

Street View – 1 Sand Dock Rd

The overall capacity is surely in the tens of megawatts and there’s an overwhelming hum coming down that driveway:

Switchyard hum

Those peaks and the corresponding lines in the waterfall show the equipment emits acoustic energy all the way up to about 480 Hz, call it the eighth harmonic of 60 Hz.

Transformer steel has low magnetostriction, which produces most of the noise at even harmonics of the 60 Hz power line (because each cycle has two current maxima). The spectrogram shows the switchyard handles enough current to emit plenty of odd harmonic energy, with a notable peak at 180 Hz.

For comparison, standing a few feet from the transformer behind a medical office building along IBM Rd:

Transformer hum

No 180 Hz energy from that transformer!

Moving a few feet further away dropped those peaks into the background.

Even with my deflicted ears, I think can hear the switchyard hum from a considerable distance along the road, so maybe the background isn’t as quiet as I think.

2025-08-14