#TPAI #video on #hoarding high-power junkyard stuff for #jugaad.
Loosely defined; Gerolf’s first “exciting find” is a 35kg transformer with a 200-amp secondary that’s only 5kVA because it’s 50Hz. Seems to be of E-I construction, so it could be a good source of electrical steel, not to mention high-ampacity copper, although his first step is to cut through the 6-kilogram 200-amp secondary with an angle grinder. His objective seems to be to make a kiloamp source for heavy welding, although I’d think a 200-amp secondary would be fine for that. He can’t usefully ohm out the primary because he doesn’t know about Kelvin connections, but he does succeed by measuring the inductances instead. He compares it to a couple of microwave-oven transformers, removing their secondaries and magnetic shunts to replace them with welding cables. 2½ turns on the small MOT can reach 395 amps. The larger MOT (also 2½ turns) reaches 649A. Another transformer he had lying around reaches 666A. 3½ turns on the 5kVA transformer exceeds 1kA, which is the limit of his clamp meter, so he got another one which measured 1200A.
This seems like high current but not high power; an inline-6 Mazda CX-90 is, by contrast, 16.6 horsepower, or 12.3kW, more than twice the rated power of this transformer, and presumably its actual output power is even less when you short-circuit its output through a wrench like this.
He also picked up a handheld spot welder (Dalex-Werke, 380VAC input, 9.2 kg, and various nameplate power ratings I don’t understand including 2.4, 6.1, 10, 2, and 20 kilowatts; I guess 7500 amps is the secondary short-circuit current and should not be multiplied by the nominal 2.3 volt output rating to get 20 kilowatts). He does get it to make some spot welds on razor blades.
He also found a component stereo system (Grundig RT 40 M tuner, Grundig SV 40 M amp, and Dual 1219 turntable) with a fake wooden façade; the tuner capacitor in the radio wasn’t even stuck, and both the radio and the amp from 01967 worked fine! He painted over the ugly fake woodgrain. He had to melt polymerized lubricant off the record player’s speed selection #mechanisms with a heat gun, then scrub it off with WD-40 and steel wool. Also the power switch doesn’t work, and he had to replace the pickup and the center pin. He explains the stroboscopic tachometer at 28'10".
More on skinhead #Papini #video #true-crime #toread
#video of interrogation of an innocent person for #true-crime in 02003, 37-year-old Michael Dixon in Hamilton, Ontario, contrasted with an ex-con named “Justin” who was also innocent.
#video of a cop watching Breaking Bad #crime (waste of time)
#video of #manufacturing a DIY wire #EDM for #machining; basically an ad for #Rack-Robotics’s (rackrobo.io) maybe-someday-open-source Wire Tool replacement hotend to turn any 24-volt 3-D printer into an EDM machine with 300μm brass wire, which looks silver, so maybe it’s tinned. Not sure how the filtration and feedback works, which seems like almost the most important part? He never mentions filtering. Also demonstrates hand-carving a 600μm aluminum plate with a 1.5mm brass rod electrode, which ought to be impossible because it should short out to the workpiece when you’re holding it in your hand, but actually it works fine. Gets up to 100mm/minute with the wire on the 600μm aluminum, or 20mm/minute in 3mm aluminum, while steel is 4½ times slower, while titanium is only 2–2½ times slower than aluminum. The power supply (“Powercore V1”) goes up to 72 volts, but the demo is all at 65 volts; he says the hard part is actually the power supply, which is “high voltage” (ha!), high power, 5000 Hz. This is at #rmrrf which I think is the Rocky Mountain RepRap Fest.
#video of #Rack-Robotics’s DIY wire #EDM #machining rig, including #manufacturing it with #3D-printing from carbon-fiber-filled PLA; the power supply here is their “Powercore V2”, which is 200 watts at 70 Vdc output with “up to” 90% efficiency for US$400. He uses a jug of distilled water from the store. He says the Powercore is “expecting a 1Ω resistance”, so it doesn’t shock him when he puts his hand in the circuit, though I notice he doesn’t connect it across his two hands. He says the wire’s outer coating is zinc, not tin as I had guessed. He says the water circulation is 100 “psi”, and it seems to be moving at a pretty good clip parallel to the wire. He touts ±100μm tolerances on the current revision, which sounds pretty shitty for wire EDM, and for the next revision they’re still only targeting 50μm, so they’re really trying for the rapid prototyping market here, not the traditional ultra-precision market of wire EDM. The motors (“hybrid” steppers) are kept out of the water, using only mechanical linkages to move the toolhead and tension the wire underneath the water. They dunk it in a 10-“gallon” aquarium to hold the water. They’ve moved to Colorado Springs and gotten funded. (This video is from this week.) 180 watts output at 5kHz implies 36 millijoules per spark, which implies about a 14μF output capacitor.
#video touting “BAXEDM”’s DIY wire #EDM kit for #manufacturing parts with high #precision; getting his “location” fit (ISO H7/h6) for his M-shaped “shaft” requires +0/-16μm tolerance on the “shaft” and +25/-0μm on the hole, so you need about ±8μm precision. He’s using a 300μm nominal kerf width, shooting for ±10μm precision, using 15mm-thick cold-rolled 304 stainless plate. He got the “shaft” almost 10μm under the nominal dimension.
Za3k’s cardboard #Zorchpad #hardware #electronics prototype mockup