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.
If you measure something often enough, it becomes science
New hawks must somehow learn that swooping across roadways doesn’t work like swooping across lawns:
We think one of “our” new Cooper’s Hawks didn’t survive its lesson.
That’s the third dead hawk we’ve seen on recent rides; it’s been a rough few weeks for new hawks. Mary also spotted a smashed owl along one of her routes.
Yeah, they’re just birds, but …
Cropped and tweaked from a Sony HDR-AS30V helmet camera image.
Just for the record, heating four 500 g bags of silica gel at 230 °F for 12 hours overnight works exactly the way it should. Two of the bags baked down to 490 g, another was at 509 g, and the fourth had bulldog clips (rather than staples); given that they started with a measured 500 g of beads, that’s entirely good enough.
Memo to Self: don’t try to cut corners: heat the silica gel packs above water’s boiling point, let them cook overnight, don’t worry about wrecking the weird ground-cloth landscaping bags, and be done with it.
This resembles nothing so much as a “developing country” shipbreaking operation:
For all I know, the ants haul the carcass into position, blow the scuttling charges to loosen the armor, and sink it in a convenient spot on the driveway:
The hulk vanished later in the day.
This is the season for staghorn beetles; the one we spotted a few years ago was in much better condition.
We often see Red Tailed Hawks circling high above the area, but this one came closer than most (clicky for more dots):
Surely you can see it, just to the left of the speed limit sign? It took us by surprise, too!
Near the middle of the road:
And away:
Perhaps it’s taking a break to enjoy just flying around? That’s about what we were doing; it was a fine morning for that sort of thing.
Squinting at a few more frames, it’s flying at 18 mph with 4 wingbeats per second. Not in a hurry, that’s for sure, and still traveling faster than we were.
We spotted a few Gas Hawks above the airport, too, but they stayed too far away for pictures…
“Our” pair of Cooper’s Hawks (or their descendants, of which there have been many) hatched a pair of chicks that recently fledged and have been exploring their world:
Sometimes they perch together:
Their world contains many interesting things, not all of which are visible to the human eye:
I’ve spotted a parent hawk circling high overhead while the youngsters practice their flight skills near the treetops. If you listen carefully, you can hear a hawk calling from far above:
We’ve seen them hopping from branch to branch, testing their wings, and by now they can launch from a standing start:
New squirrels emerge at about the same time, with equivalent levels of experience:
Right out of the nest, new hawks know what to do, if not quite how to accomplish it:
That little squirrel instantly pasted itself to the bottom of the branch and escaped. This time, anyway.
Mary watched one hawk practicing its pouncing skills by attacking a pine cone. A talon wedged under a tight pine cone scale, to the extent that the hawk spent the next half hour flopping around the yard trying to part company with its personal Pine Tar Baby.
Perhaps the piles of Chipmunk Gibbage came from a new hawk practicing its regurgitation skills …
Go, new hawks, go!
Taken with the Sony DSC-H5, sometimes with the 1.7x teleadapter, under ambient light, hand-held, sometimes braced against the frame of a partially open door.
So then this happened:
Yeah, tanker boots and all; not the weirdest thing we saw during RIT’s graduation ceremonies.
This summer marks her fourth of four co-op semesters with Real Companies Doing Tech Stuff and her final classes end in December; RIT holds one ceremony in the spring and being offset by a semester apparently isn’t all that unusual. She (thinks she) has a job lined up after graduation and doesn’t need her doting father’s help.
But, hey, should you know someone with a way-cool opportunity (*) for a bright, fresh techie who’s increasingly able to build electronic & mechanical gadgets and make them work, drop me a note and I’ll put the two of you in touch. [grin]
(*) If that opportunity should involve 3D printed prosthetics with sensors and motors, she will crawl right out of your monitor…
With a new motor and controller in the reconfigured SqWr Power Wheels chassis, I made a few measurements under somewhat less than controlled conditions, with the butt end of the chassis on jack stands. The general idea was to find out what the “lightly loaded” condition looked like in terms of motor current; after some mechanical and electrical improvements, we’ll be in a better position to determine the battery load & suchlike.
Preliminary measurements:
With everything in position and the Tek 6303 probe set for 10 A/div, this is what happens when you push the deadman switch:
Obviously, the motor controller takes much too long to wake up & sense the current.
The initial slope of that current waveform looks like 80 A/360 µs = 220 kA/s. The upper trace gives the motor voltage, so 23 V / (220 kA/s) = 104 µH, surprisingly close to the measured 128 µH.
Deploying the mighty Tek CT-5 (with an enclosed A6302), cranking the gain to 50 A/div, and poking the deadman again:
During that initial pulse, the controller connects the battery directly to the motor, so you’re looking directly at 200 A of battery current. For reasons that aren’t relevant here, the mandatory 60 A safety fuse isn’t present, although it should be able to withstand a millisecond or two of moderate overload without blowing.
With that out of the way and the motor running at a few hundred RPM, due to the nonzero twist-grip output voltage with no throttle applied, the controller actually does PWM pretty much as you’d expect:
It’s not clear what caused the small dent just before the middle pulse; perhaps the motor commutator switched from one winding to the next.
The battery current will be much lower than the motor current in this mode, roughly (motor current) * (PWM fraction). We haven’t verified that, but for 30% PWM it should be around 5 A = 15 A * 0.30. The actual battery current looks smoother than I expected, although I have no traces to show for it; more study is needed.
Eks once again graciously loaned me his Tek current probes; this whole Power Wheels mess motivated me to get off my ass and accumulate my own collection, about which more later.
The Smell of Molten Projects in the Morning 