#Hand-build anything

Which soldering iron is that? Looks really handy.

No need for a mould?

He had a set of pulleys but no mini drill press, so built a portable rechargeable desktop drill press with no cord; drills square steel like cutting butter and even large threaded rod. Materials list (with prices): 795 motor 12–24V ¥28.9, drill chuck + 5mm adapter ¥15.28, 20/60-tooth pulleys ¥12.1, two tapered roller bearings (10mm bore) ¥10, linear bearing ¥5.5, flanged linear bearing ¥15.2, 10mm shaft 40cm (¥17.5/m), 5mm shaft 10cm (¥39.9/10), M6×90 hex socket screws ¥3.73/5 sets, small 5×10 bearings ¥17/10, springs ¥4.3/10; electronics: 6 × 18650 2600mAh 10C (¥343 per 100), 6S 35A balancing BMS ¥23.74, DC 7–100V charge meter ¥10.9, IP2369 PD 45W 2–6S charge/discharge module ¥21.3, 6mm rocker switch ¥1.9; if you don't want Li-ion, skip the cells and BMS and run direct DC; if you don't have a spot welder and other professional tools, better not build a Li-ion pack. Battery: main positive and negative brought out on nickel strip to the BMS; many people struggle with balance leads, just remember: from negative to positive, one per series group, sampling each group's voltage; fit the balancing BMS and spot-weld the negative, plug in the balance leads; some BMS boards need an input 2–3V higher than the pack for a second or two on first power-up to activate; measuring around 21V output means it's active. Mechanical parts modelled to size, free and open-source on MakerWorld, PLA printing takes four plates and a dozen-odd hours, ¥20-odd in filament. Assembly: cells into the box recess, fit the charge meter, main positive reserved as a lead, charging module glued in at the Type-C cutout; meter negative, charger negative and main output negative all go to the BMS negative output; BMS charge input lead to the charging module negative, the other to the module positive, flick the module's little switch and the light comes on, working normally, Type-C both charges and can discharge to a phone; the pack positive's other lead goes to the switch's centre pin (input); output load lead, meter positive and sense lead twisted together onto the switch output; switch into its reserved hole; power on, meter lights up, close the lid; tap the shaft into its round hole. Head: small bearings top and bottom, tapered bearing (10mm bore printed adapter down to 5, tight space makes it a struggle to fit, a design failure), drill-bit adapter, flanged linear bearing with 4 screws, the other linear bearing, chuck, motor bracket with 4 screws, motor, small pulley grub screw, belt (better to fit the belt before the pulley); turntable base with two screws, loosen/tighten to adjust table height; the bottom clamp's third set of hex screws adjusts bit angle; springs on the two vertical rods; the handle's pivoting link copies an old hand-pump well, copper wire through the outer hole to stop it slipping off; power leads to the motor, dust cover. Test drill: after one hole it wobbles and vibrates badly, the shaft isn't vertical, the head model has a serious problem; taking it apart shows the plastic already fused and scorched; while drilling the bit pushes upward, rubbing the plastic until it heats and melts; remodel so the tapered bearings go in from the outside, one top and one bottom, stopping upward push and downward drop, the bearing inner race spins with the bit without rubbing; found that the small bearing's 10mm OD works as a reducer for the 5mm shaft; nearly two hours to reprint, fitting difficulty and friction heat perfectly solved; square steel like tofu, threaded rod not quite all the way through but close, good enough for a desktop mini drill press. Comments: made one too (4); don't cost it at 10cm, nobody sells 10cm; how much do you spend a month on inventions; add a fixture to turn beads; make it waterproof to cut bottles; main column too thin and too many plastic parts, poor rigidity, fine for fun; the rear column needs a really thick tube; can you make a mini table saw (tutorial coming).

Is it open source?

What if the code throws errors

The kitchen knife is blunt; experts use a whetstone, I’m a novice, so build a portable rechargeable belt grinder: forward / reverse adjustable, charge display, a neat power switch, stepless like a gas pedal; kitchen knives and machetes come up sharp with a quick pass, belts are swappable, one minute and it cuts vegetables like tofu; cost ¥100-something. Core parts: belt-grinder head kit ¥44 (comes with 5 belts, drive wheel / idler); 795 motor ¥28.9 (with mount and dust cover, 200W). Assembly problems: the motor shaft is smaller than the drive-wheel bore, so buy 5mm ID / 8mm OD bushings (¥19.5 for 5), heat the drive wheel so it expands and drop the bushing in, then lock the grub screw to clamp the motor shaft; the frame holes don’t line up with the motor holes and can’t be drilled (the original design wasn’t for a 775/795), so he models a base and housing (with battery bay and slots for the electronics) plus a motor bracket, 3D prints them, and will release the models free and open source; two screws hold the bracket to the motor, the other side to the steel frame, drive wheel fitted; changing a belt means removing the idler; a quick power-up to fine-tune the idler until it runs smooth. Battery: for portability, 18650 2000mAh 5C-discharge at ¥3 each, 9 cells for 12V (3S3P, 12.6V 6000mAh); battery meter DC7-100V ¥10.9; forward / reverse via a KCD1 6-pin 3-position rocker switch, ¥13 for 10; Type-C 3S charge-management module ¥11.8. Spot-weld the nickel tabs on; note the parallel / series joins are welded in a “box” pattern so the balance BMS actually works, otherwise it only balances one group; wrap in fish paper for insulation and heat isolation; fit the 3S 60A 12.6V balance BMS (¥6.1) — separate-port, so both input and output leads must be connected; pack goes into the printed box, input side to the Type-C charging module, plug in and it charges normally. Fit the lit metal latching button ¥6.9: switch input to the pack’s output positive; button negative and meter negative twisted into one lead; meter positive, sense lead, switch output and switch positive twisted into one lead; the negative lead to the pack’s output negative; into the input of the adjustable buck-boost module ¥15.3, then the master switch; the light comes on, so the wiring is OK. Forward / reverse rocker switch: the middle pins are the power input, and whichever of top or bottom is used as output needs two jumpers crossed to the other side’s pins — the principle is simply swapping positive and negative; switch input from the buck-boost output; the buck-boost raises 12V to 24V so the 795 is more brutal and spins faster; not building 24V directly because 12V is smaller, portable use doesn’t need long runtime, and 12V parts are in stock. Output leads out of the box to the motor; lid on; the frame bottom is screwed to a bracket and strong glue fixes the frame to the box base; motor positive and negative connected; job done; test grind works really well and fast, usable for DIY too. 102 comments: this is the way, no argument (7); is a 12V motor enough? why forward / reverse for sharpening? sourcing (2) → every part has detailed sourcing info in the video; where to buy components / is LCSC reliable (2); add a rest to fix the angle (1); an angle grinder takes seconds → too aggressive, the edge quenches; does dry grinding anneal it → no; isn’t a bowl bottom good enough (many); wasn’t this on your livestream → yes; posting at 4 a.m. → afraid of copycats; which 3D printer; the kit is only ¥40-something, don’t rip people off; help fix two streetlight lithium packs.

Opens with ‘Second Battalion Commander, your Italian cannon’. The romance the New Year deserves: walkie-talkie in hand, set off firecrackers remotely by voice, load 5 at a time for burst or single shots; materials are scrap steel pipe and rebar plus a few dozen yuan of electronics; the principle is a WiFi transmitter and receiver controlling ignition. Mechanics: cut pipe and weld a rack, a pivoting joint at the bottom to adjust the angle, a tail so it stands stable; the front support uses old rebar and galvanised pipe, also adjustable; firecracker clip: slot the pipe for the clip bracket, weld a slide on the short end on the other side, weld as many pipes onto the base as shots you want (5), weld nuts at the head and the slide’s tail, cut a fuse groove in the pipe; the clip rides the slide, a rubber band through the screw hole anchors to the base, and after ignition it springs to the next one for automatic feed. Electronics (with shopping screenshots): one 2000mAh 18650 (¥3) powers the walkie-talkie (transmitter) with a 5V charge/discharge module (¥2.85); 6 old salvaged 1500mAh cells make the 24V pack with a 24V 6S balance BMS (NMC 6S common-port 35A with balancing, ¥25.74); a CC/CV adjustable buck-boost module (¥15.3) charges the pack, 5–30V wide input; an XL4005 adjustable buck module (¥5.5) takes 24V → 5V for the MCU; a USB port powers the ESP8266; 2 × ESP8266 (¥13.94), one transmit, one receive; ASR-PRO voice-recognition dev board (¥26.2) + small speaker; 5V relay module (¥2.9) switches the ignition; 24V high-voltage ignition kit (high-frequency transformer, two pins produce an arc). Programming: the voice module uses the vendor’s Chinese block-based tool, wake word ‘Second Battalion Commander’, commands ‘bring up my Italian cannon / fire / open fire / launch / stop / continuous fire / stop continuous fire’, sent over serial to the ESP8266, with synthesised voice generated in the model and flashed; the transmitter ESP8266 in VSCode PlatformIO: opens a hotspot + TCP server, relays the voice serial data, reconnects on drop, 300-odd lines; the receiver connects to the transmitter and handles ignition / auto cut-off / continuous fire, with its own hotspot serving a phone web page for settings (cut-off time etc.), 700-odd lines; flash and test via serial log. 3D-modelled boxes (ignition head, receiver box, transmitter box), open-source on MakerWorld for printing. Assembly: remove the ignition head’s HV leads, pass them through the box and re-solder, lengthen the power lead; the 24V pack is 6 cells in series, 25.2V full, 24.63V on the multimeter after spot welding, wrapped in fish paper, main + and − nickel tabs spot-welded on; balance leads run from the main positive, one per group in order; the balance BMS only takes the negative input and negative output, the positive bypasses the board and goes straight out; plug in the balance leads; the BMS is inactive by default and needs a moment of 26V+ to activate; voltage tests fine, boxed up, snug fit; the buck-boost output set to 25.2V and connected to a parallel pair of leads on the pack; the 24V output feeds the buck module set to 5V; forgot a switch, so cut the lead, extended it and added one; 5V leads to the USB socket; the relay also needs 5V, taken from the 5V buck; the buck-boost output also feeds two 24V leads, positive through the relay to the ignition head; relay 5V + IN signal + 24V in/out extended to the ignition pack, controlled by the ESP8266 high/low level; fit the ESP8266, Type-C power, aviation-connector socket as the charge port; power-up test — charge LED on, the switch wiring doesn’t smoke, manually triggering the relay gives a normal arc, receiver done. Transmitter: the voice module’s two serial wires go to the ESP8266 serial with RX/TX crossed; 18650 + 5V common-port module, nickel tabs spot-welded onto the cell to make soldering easier, then + and − leads soldered on and into the module input, Type-C charging with green flashing for charge and blue for discharge; two Type-C leads with + and − paralleled into one input, plus a switch (one end to 5V +, negative straight through, switch output to the Type-C +); fit the ESP8266, speaker on the lid, voice module, Type-C common-port module; the two Type-C leads feed the voice module and the ESP8266; power-on test, ‘fire!’ OK; lid on, a decorative ‘soul antenna’; phone into the config page to set auto cut-off time / continuous fire; the ignition head is fixed to the rack with an acrylic sheet for insulation, ignition pins glued so the arc lights the fuse; outdoor test, ‘fire!’, fires in sequence, works really well. 257 comments: does this count as manufacturing a firearm (an entertainment toy, not a weapon); I’ve only programmed 8266 with Arduino, can I learn this (absolutely); how to program it (follow the video); a rotary-drum launcher would be perfect (sold online); is it open-source; the pipe has no rifling; won’t the police have a word; are you selling, how much; fireworks are banned.

Somehow ended up making a few fun color-changing night lights / mood lights as a gift for the students who took a term of the science maker extension class — a little present for the last lesson, tied to what we covered. Simple parts: a cell, a charge-management module, a switch and a color-changing LED bead; the LED draws only 0.01A, so one 2000mAh 18650 keeps it lit for a month; the goals were long runtime, fun color changing, durable, rechargeable, simple and cheap to make. Build: nickel strip is already welded to the cell’s +/−; fold the strip over so it doesn’t stick out, and a wrap of tape around the outside makes it more secure; the cell’s +/− go to the charge-management module, charged over a Type-C cable, the module charges the cell at 4.2V; the module’s 5V output goes to the +/− leads; the LED negative goes straight to the output lead, the switch sits on the positive side; test lit fine, decent brightness; loose parts look untidy, so model a shell, one print run of three sets takes over 4 hours; the two halves fit together seamlessly; three done (short on time). Over hills and around eighteen bends to the school; in class every student gets hands-on, small hands not yet skilled but earnest, helping each other, completing the circuit together and lighting their first light-controlled lamp; maybe one day this light will shine among the stars; the lights he made go to the best students; applause closes the last lesson. Comments (143): where to buy such a low-power LED, link? (5); Biao, when’s the next spot-welder sponsorship (why?); a cell must have a BMS, safety first / no BMS, aren’t you afraid the kids get blown up (creator replied); the charging port sits too low to plug in easily; a white shell would diffuse the light better; what brand of multimeter (ALIENTEK); how’s the welder / how much.

What did it cost

A monster fan hand-built on 6 × 32140 cells. The 3D-printed model is his own design, prints well, and the whole structure is joined with heat-set inserts. The motor is a 3660KV brushless paired with aluminium blades; the small motor can burst to 1200W. Insulating rings go on the cells, then spot welding with the AWithZ U3 welder set to manual; the motor is rated 1200W, which by Ohm’s law is about 100A, and this nickel strip passes at most 33A, so three layers of nickel are stacked one after another to make sure the cells can deliver their full discharge rate; the welds come out perfectly smooth. Cells in, fan housing and grip screwed together, done; thrust tested at over 1000 grams. Comments: asking for the files (×2), no mould needed?, how much did it cost, ‘1200W? my e-bike is only 1200W’.

Sharing money-saving experience from hand-building lithium packs so beginners spend as little as possible. The three-piece kit: the welder is essential, the internal-resistance meter is optional, the load tester is optional — a beginner only needs a welder, skip the other two for now; early on, only build small packs and order straight from the cell brand’s official channels (EVE official site / Tmall / Alibaba; the page shows 18650 3.6V 3200mAh / 2850mAh etc.), which basically needs no testing — with a welder you can build right away; think about instruments later when going to big capacity. Key point — which welder suits a beginner: buy the most expensive one you can accept within your budget, and go for a big brand as far as possible; this is the third welder I’ve bought (AWithZ); one feature is very beginner-friendly: the pen sits on the cell for ages and nothing happens, because the manual weld button hasn’t been pressed — press it and it welds instantly, the semi-auto mode; beginners often mis-place the spot or set the nickel tab crooked, and if the pen welds the moment it touches, the cell is ruined, so a semi-auto button is best to have; there is also a repeat-pulse mode that welds the same spot repeatedly, suited to copper sheet that needs more power — hold the pen steady and it fires up to 3 welds in quick succession. Mine is the AWithZ U3 Pro: pure nickel 0.2mm MAX, and it also does steel and copper sheet (copper 0.1 MAX; nickel-plated / steel / iron 0.35 MAX); nameplate U3 battery spot welder, 4.2V MAX, Type-C 5V/2.1A, USB 5V/2.4A, 11000mAh 40.7Wh, Juequi Technology; plenty for a beginner. Consumables: glass-fiber tape, heat-shrink film, fish paper. A special note on cells: this is the positive, this side is negative — many people don’t know the whole can is negative; open one up and everything except the positive is negative, so positive insulation is critical, always use positive fish paper. Non-essential accessories aren’t covered; get the three-piece kit straight and you save a lot. Comments: asking for the EVE official link (search results are all ads) (2); lend me the welder for two spots nearby; can UV glue join them; what battery for a 24-set net-hauling boat; a mis-weld ruins the cell? can’t you pull it off and re-weld?

The creator wanted an adjustable supply that works without mains — for the price of one you can hand-build four. The core is an adjustable buck module with a coulomb-counter display; power comes from 12 × 18650 in 3S4P (12.6V) with a 3S 40A BMS. A plastic box is cut for the quick charge port, a square hole for the coulomb-counter display, round holes on both sides, vent holes and a fan slot, a battery gauge and a master switch. The charge input feeds a CC/CV buck-boost module with charge management, output set to 12.7–12.8V; two 40℃ normally-open thermostat switches in parallel control the fan (one stuck on the boost module heatsink), with the fan and gauge negatives on the boost module input. Battery 12.6V goes through the master switch into the boost module set to 36V max, then into the digitally controlled regulator module with thyristor; output leads with clips on the output terminals, the coulomb counter’s ribbon cable into the core board. Power on — charging works, the coulomb counter lights red, a multimeter on the output clips shows the knob sets voltage precisely, up to 33V; it can charge while in use, set voltage and current precisely for load tests, and work as a universal charger for all kinds of batteries.