bpark1000

You should solder bypass 0.1 microfarad capacitors across GND/VCC at least every couple of LEDs. Signal is high frequency, and may get corrupted due to noise on VCC bus.

Your vinegar/steel wool wood stain will attack stainless steel, making it mottled and pitted if it sits for a time. Don't put that on a stainless steel sink! The stain will not immediately get dark in the wood; it needs hours for that to happen. (The relatively colorless ferrous iron needs exposure to the air to convert to ferric (brown) form. It reacts with the tannic acid in the wood to make ferric tannate (dark brown).You can dabble a little of the stain on the labels to give then a "rusty" appearance.Put tonic water in the clear bottle. It will fluoresce under UV light. You can get UV LEDs to illuminate from All Electronics.

If the clamp is slipping, you need to look at the pins that bear on the beam first. These get worn every time the clamp is slid or tightened. (The force is concentrated in 1 spot on each pin, whereas the wear on the beam is distributed, unless you always clamp the same thickness stock at the same screw setting.) When they wear, the sliding member becomes more inclined, giving less normal force. I would inspect those first. Look for flats on the side that faces the beam. Replace or rotate them to a fresh side of they are worn.Another strategy is to let the clamp rust on purpose (if the beam and pins are not plated).

That approach will not make the motor movement any more discontinuous than your other method. Figure how many steps are needed for a minute (gear ratios and number of steps in motor per turn will go into that calculation). Divide the processor clock (16 MHz?) by a factor that the number of steps factors into. Each interrupt will advance the stepper one step, and this will be at a uniform rate. (I don't believe in using complex libraries to do simple things. Nothing is simpler then dividing a clock down, and dividing that by 4 to drive the stepper. If the load is light, you can use wave drive and save power, else you can use "full step drive".)

Rather than gamble with the delay in the C code, why not set up a periodic interrupt using timer off the clock crystal (say 16 per second, or whatever is convenient) and run a piece of code that increments the stepper drive? This way, while the code produces time jitter, this is on the microsecond scale and does not accumulate. You will have much better control of the speed.

Are you sure you have the platinum/tin silicones in the right order? The reason I ask is that tin cure silicones usually are "just looking for an excuse to not cure". They are notorious for this. On the other hand, platinum-cure tend to be immune to having their cure interfered with foreign substances. I have never seen the reverse case, as you report.

Be careful! Is the glass lid of the pot rated to withstand the vacuum force? It could implode! (If the pot is 10" in diameter, the force on the lid with high vacuum is about 1000 lbs! Even with -40Kpascals-vacuum, it is still 400lbs.)What I would do is to draw vacuum, but also have a small leak that slowly admits air to the chamber. The moving air at low pressure will carry away the moisture better than still air. Without air circulation, the boiling point of water must be exceeded to get water transport out. With your -40kilopascals, that's only a 40% reduction in pressure. Boiling point of water is not even reduced 10C (so you would need to get hotter than 90C to drive off water). By bleeding air, any water that evaporates from the filament will be swept away. Better is...

Be careful! Is the glass lid of the pot rated to withstand the vacuum force? It could implode! (If the pot is 10" in diameter, the force on the lid with high vacuum is about 1000 lbs! Even with -40Kpascals-vacuum, it is still 400lbs.)What I would do is to draw vacuum, but also have a small leak that slowly admits air to the chamber. The moving air at low pressure will carry away the moisture better than still air. Without air circulation, the boiling point of water must be exceeded to get water transport out. With your -40kilopascals, that's only a 40% reduction in pressure. Boiling point of water is not even reduced 10C (so you would need to get hotter than 90C to drive off water). By bleeding air, any water that evaporates from the filament will be swept away. Better is to set this up so the bleed air comes from an area with dehumidifier running. At 120F, vapor pressure of water is only 0.12 atmospheres, so you would need -90kilopascals without circulation.

When making clear castings, you want to have a thickness of resin surrounding the embedded objects on all sides, to permit finishing and prevent moisture intrusion.Mix the resin in 2 batches. Do 1st pour as usual, then unmold, flip over, and do 2nd pour on back using mold a little larger in diameter (a pipe fitting piece could be cut for this.) First pour should be allowed to just soft-set. (2nd pour adheres to 1st better, and there is less shrinkage stress). It is best to anneal by baking at 120 degrees F for 3-4 hours a few days after it is set. This hardens the epoxy, making finishing go better, and relieves the internal stress which could lead to cracking later.Slit both molds in 1 place on side and seal with hot glue on outside. This makes unmolding easier. Do not allow epox...

When making clear castings, you want to have a thickness of resin surrounding the embedded objects on all sides, to permit finishing and prevent moisture intrusion.Mix the resin in 2 batches. Do 1st pour as usual, then unmold, flip over, and do 2nd pour on back using mold a little larger in diameter (a pipe fitting piece could be cut for this.) First pour should be allowed to just soft-set. (2nd pour adheres to 1st better, and there is less shrinkage stress). It is best to anneal by baking at 120 degrees F for 3-4 hours a few days after it is set. This hardens the epoxy, making finishing go better, and relieves the internal stress which could lead to cracking later.Slit both molds in 1 place on side and seal with hot glue on outside. This makes unmolding easier. Do not allow epoxy to contact hot glue (do all gluing on outside of mold. There may be a chemical reaction that inhibits epoxy setting.) You were wise to use epoxy, rather then polyester. The plasticizers in vinyl cable will inhibit setting of polyesters. Epoxies are much more immune to chemicals they come in contact with.

There was comment about allowing torch gasses to flow through chamber. Why not have back brick just sitting there, with small gaps for flue gasses to escape?Do bricks in oven need to be cemented together? What if they were just set together?

Rather than casting the cord directly into the concrete, I would cast a hose in instead. That way, if repairs are needed, a new wire can be slipped in. The wire will tend to fatigue at the point where it exits the concrete.

I would try displaying this piece with a corner facing downward, rather then edge downward. Or it could be hung by a corner as a ceiling fixture.

After finishing the cutting and degreasing, sand the sharp edges with #400 silicon-carbide wet-or-dry paper and water. Just a light sanding at 45 degrees over the edges will take off the sharp edge. Clean and dry.For strength the silicone needs to be applied between the mating surfaces. Apply bead to mating edge then assemble. This is cumbersome, as you can't tape beforehand. Make some cardboard jigs to aid assembly. Assembly can be done in steps allowing silicone to dry between each one. Second coat can be applied on inside as you describe after the first is set.Silicone is weak when freshly set. Allow at least overnight before handling. In dry climate, ball up wet paper towel after initial setting and put inside and cover to allow moist air to speed cure.

I would cut the molds to the desired thickness of the pavers. You can slightly overfill, then use screed board to trim to height. Every paver will match in height and won't be wedged.

One thing to watch out for when assembling wood around glass: in time, the wood can shrink and break the glass! Be sure to leave room around the glass edge. paneled doors have a lot of slop in the panels, concealed by the grooves they fit into for the same reason.I assume you put the film on the underside of the table top?

You could improve the terrain handling of this robot by using lever equalization on the wheels. (Look up "steam engine wheel equalization"). if you allowed 1/2 inch vertical movement of each wheel from its nominal position, you could climb even higher curbs, and navigate irregular terrain. Neither electrical nor software changes would be required, except to allow some flexibility in the wiring harness to the wheel motors. The trick is to make the robot equivalent to a tripod-wheeled vehicle. You could equalize the front wheel pair left-right, and the other left-side, right-side pairs front-back.

This design could be simplified by using NeoPixel LEDs. You can get as much brightness as the batteries can provide, and need not worry about I/O current capability.

That's odd. I have one and consider it superior to the $1000 Derex grinder-mounted sharpener. One thing to watch out for in any drill sharpener: the key is getting the drill bit "timed" (rotated correctly in the collet before tightening). The Drill DR is much better at this, as it has 2 paddles to index the drill. Even more important, you can get your hand on the back end of the drill to help position it against the stop plate and get it rotated against the paddles. If you have the more expensive one, you can also split the point.

First problem you need to worry about is when making tree cross-sections, that the wood will split when it dries. The wood needs to be treated with a chemical called polyethylene glycol, preferably immediately after cutting. This is sold by wood working outlets.http://www.rockler.com/polyethylene-glycol-peg-gre...If your section has dried, soak it in water until the cracks close, then treat in PEG solution. Soak time is function of wood thickness, species, temperature, and solution concentration. After treatment dry the wood, and cut to final dimensions. Wood will be a bit "waxy" but there is no reason why the high voltage process shouldn't work. Experiment on scrap pieces.

I have no video, but can explain how I did it. In this case it was tree pruning saw of the sane tooth style as Japanese saw, except blade is curved concave and teeth are coarser. I set rest on "standard" bench grinder to be perpendicular to wheel, placed blade on rest, at angle to match facet angle, and VERY LIGHTLY touch to wheel, just enough to make a noise. Then move to the next tooth.Grinding wheel must be dressed very square on edge. Otherwise, there is risk of hitting side of next tooth. I use a "tool sharpening" wheel, not a "utility" wheel (that would be used on lawnmower blades).On fine saw such as you showed, this would be more difficult. I would most likely use small handstone and some sort of jig.Some saws of this type have the facets angl...

I have no video, but can explain how I did it. In this case it was tree pruning saw of the sane tooth style as Japanese saw, except blade is curved concave and teeth are coarser. I set rest on "standard" bench grinder to be perpendicular to wheel, placed blade on rest, at angle to match facet angle, and VERY LIGHTLY touch to wheel, just enough to make a noise. Then move to the next tooth.Grinding wheel must be dressed very square on edge. Otherwise, there is risk of hitting side of next tooth. I use a "tool sharpening" wheel, not a "utility" wheel (that would be used on lawnmower blades).On fine saw such as you showed, this would be more difficult. I would most likely use small handstone and some sort of jig.Some saws of this type have the facets angled across the blade, not just along the blade. For those, set the rest not perpendicular, and sharpen every other tooth, then flip blade over and sharpen the remainder.

The secret to these saws is the small slanted facet on the tip of each tooth. The edges of this facet must be very sharp. I use a small handstone to sharpen it, or a small grinding wheel on a Dremel tool. Normally, abrasive on a cloth wheel rounds edges. How do you get the cloth wheel to sharpen the facets?

What is the white cottony-looking stuff that you wrap the LEDs and the power supply with? I would be concerned with overheating because the white stuff would act as insulation. Is it flammable? (I did not see anything like this in the parts list).

Are you driving all the LEDs wth a single serial NeoPixel line, or are you driving the 8 strands with 8 separate serial signals?

Place gear print (laser printed) face-down on clean gear blank. Wipe back of paper with small rag lightly wet with acetone. Laser toner ink will transfer onto the wood. Let dry, and peel off paper. Design can also be transferred with hot iron.

Simple way to get thread square is to drill a clearance hole in scrap piece of wood. Slide the tap through that, and while holding the scrap firmly against the item being tapped, start the tapping a few turns. Then remove tap and scrap, and continue tapping.

Added suggestions: put adjusting feet on the base. Make the top "heavy" so it won't lift, then remove weight until it just BARELY lifts off the spinning plate. Then adjust the leveling feet to keep the top from going off to the side. Once you get it levitating, it will most likely collapse back to the plate. Remove a little weight to keep it floating. This scheme allows determining the proper weight first, rather then simultaneously having to determine weight and the leveling simultaneously. The heaviest possible weight also makes leveling adjustment less sensitive.Also keep in mind that temperature affects the top. When it gets warmer, you must remove a little weight.You can build a "perpetuator" to keep the top spinning "forever". It consists of a...

Added suggestions: put adjusting feet on the base. Make the top "heavy" so it won't lift, then remove weight until it just BARELY lifts off the spinning plate. Then adjust the leveling feet to keep the top from going off to the side. Once you get it levitating, it will most likely collapse back to the plate. Remove a little weight to keep it floating. This scheme allows determining the proper weight first, rather then simultaneously having to determine weight and the leveling simultaneously. The heaviest possible weight also makes leveling adjustment less sensitive.Also keep in mind that temperature affects the top. When it gets warmer, you must remove a little weight.You can build a "perpetuator" to keep the top spinning "forever". It consists of a thin pack of iron laminations spaced about an inch under the magnet platform, with a coil driven with a pulsed waveform at several hundred Hz. A 555 timer chip set to generate a narrow pulse feeding a drive transistor, and a 15V supply will do it. This was also sold commercially, but then discontinued. You will need to re-adjust the top weight with the perpetuator underneath. This can be done with the coil unpowered.

I use a propane torch, applied carefully, for gradual bends on heavy-walled pipe, for making underground irrigation sleeves into which the flexible line is inserted . It takes about 5 minutes of carefully moving flame to do it. This allows me to selectively heat only the parts to be bent. You could integrate this heating scheme with your hot sand method to heat the pipe from both inside and outside. You could also dump out and reheat the sand multiple times.

You can reduce the cogging forces in iron-based generators. (Ironless generators have no cogging forces). Do this by curving the magnets to reduce the harmonic field, and either skewing the slots or magnets by 1 slot end-to-end, or setting the magnets "off their correct positions" for short rotors.

For machines that turn slowly, the old-fashioned slotted iron designs work best, as iron losses are low, and copper losses high. Anything that boosts coil voltage (raising flux density) helps.

Don't be afraid of axial designs/centrifugal effects! The "pull" is in the plane of the disk. This is "easy" compared to pull directly away from the surface of a rotating drum structure. A ring around the outside, outside of the working parts of the motor, made of "real" material such as machined aluminum, can bear this.

Thinner wire gets you the voltage, but does not get you the current. The power available from a generator is proportional to the square of the speed. The magic number to look for is voltage squared divided by winding resistance.

I know that, but circuit determines frequency range. What is that range?

What frequency are you running at?

Refractive index of lenses cannot be "easily changed", but the lens power may be readily selected in 1/4th diopter units. Polycarbonate is about 1.58, and water 1.33, and those are fixed. But this use-in-water effect can be compensated for by selecting a stronger lens (as measured in air). This will require about a doubling in the "in air" power. So if you need a +2 diopter lens in air, you will want to order a +4 diopter lens for use in water.For use in sea water, the lens "in air" diopter power might need increasing further.

If you "crank up" the refraction of the lenses (on land) about 2X, you can make this work without having to have an air-enclosed chamber for the lens.(Refractive index lens, ~1.6. water, 1.33)You can buy some lenses, and test in swimming pool or lake. Be sure to hold lens at proper distance from eye.You can buy lenses from superopticalsystems.com for $0.75 each, with even cylinder prescription if you need it.

The convex lens theory you refer to is called "thin lens theory". "Simple" convex lenses perform equally well whether flipped or not, but they have terrible aberrations, outside their "thin lens regime". A camera lens is a complex collection of often 8 lens elements or more, some made of glasses with differing optical properties, all in the effort to minimize aberrations. Camera lenses are not "thin lenses"! That's why camera lenses are expensive. Low F-number lenses are more challenging to design; that's why they are insanely expensive. Not turning the lens around (but effectively turning the optical path around in macro mode) undoes all that wonderful design the manufacturer went to.

Camera lenses are OPTIMIZED to focus light bundles that are nearly parallel from the "front" of the lens (because the object is "far away compared to the lens focal length and diameter"), and focus them to a plane that is almost exactly 1 focal-length away from the lens (on the "backside" of the lens) to the sensor, WITH MINIMUM ABERRATIONS.When using lens in macro mode, the conditions are approximately reversed; the object is positioned 1 focal distance away, while the sensor is relatively "far away".If the lens were not reversed, it would be used way outside its design parameters. While in theory the lens would still work, the aberrations will be hideous unless you stopped it down to a pinhole.

Cutting fluid for drilling, machining, or sawing aluminum, especially the gummier alloys.For CLEANING rusted bike chains. Spray on, ride brake some to break loose links and repel moisture, then apply oil. It is important that the oil penetrate inside the links. The WD-40 helps remove the grime and allow the oil get in. Thereafter, keep the chain well oiled.

What you have is a magnetic stirrer, used widely for stirring nasty chemicals in glass flasks. This principle is also used to couple drive to pump without needing moving seals. A variant of this is a commercial toy (patented in the 1970's) called "top secret". It is available on Amazon.www.amazon.com/Warm-Fuzzy-Toys-815895013987-Secret...Its top is the same as what you have except the magnet is much weaker. Inside the base, there is a vertical iron rod on center with 2 coils wound around it, a single transistor, and a 9-volt battery. On-off switch is not required! There are no moving parts in the base.This is patent description, which explains it well.http://www.freepatentsonline.com/3783550.htmlWhen the top is spinned, magnetic induction turns the transistor on in pulse...

What you have is a magnetic stirrer, used widely for stirring nasty chemicals in glass flasks. This principle is also used to couple drive to pump without needing moving seals. A variant of this is a commercial toy (patented in the 1970's) called "top secret". It is available on Amazon.www.amazon.com/Warm-Fuzzy-Toys-815895013987-Secret...Its top is the same as what you have except the magnet is much weaker. Inside the base, there is a vertical iron rod on center with 2 coils wound around it, a single transistor, and a 9-volt battery. On-off switch is not required! There are no moving parts in the base.This is patent description, which explains it well.http://www.freepatentsonline.com/3783550.htmlWhen the top is spinned, magnetic induction turns the transistor on in pulses, timed to keep the top spinning, like a DC brushless motor does. Unlike your system, the top must be off-center on the base to get energy. That's the purpose of the bump in the center of the base. Otherwise, the top of mechanically free to wander around on the base. The top can be started spinning in either direction. The battery can last up to 2 weeks!

If you use a significant amount of alcohol in a pie crust, and then bake it in the oven, you could accumulate explosive gasses in the oven!Any of the other uses where alcohol is at above 60% can be flammable, and should be handled as such.For other non-consumption uses (such as window cleaning or goo/paint removal), denatured alcohol is much cheaper and has no water dilution, which interferes with its solvency in some situitions.

I looked at your vacuum regulator video. It has a severe case of the "jimmies". This is because your "D" term is not enough, or noisy. (The problem with the "D" calculator is that it is a "vacuum cleaner for noise". What is the sample rate for your PID loop? How many bits is the pressure signal (or if you are you measuring the time delay directly in Arduino, what is resolution?) Another thing is that the servo/link is non-linear as you use almost all the 180 degree arc. You can linear-ize that with different linkage or "weird" valve opening shape (I would use rotary, rather then linear, valve).Another problem you probably have is stiction because the air force against the valve vane. Rotary valve or 2 opposed vanes can cancel mos...

I looked at your vacuum regulator video. It has a severe case of the "jimmies". This is because your "D" term is not enough, or noisy. (The problem with the "D" calculator is that it is a "vacuum cleaner for noise". What is the sample rate for your PID loop? How many bits is the pressure signal (or if you are you measuring the time delay directly in Arduino, what is resolution?) Another thing is that the servo/link is non-linear as you use almost all the 180 degree arc. You can linear-ize that with different linkage or "weird" valve opening shape (I would use rotary, rather then linear, valve).Another problem you probably have is stiction because the air force against the valve vane. Rotary valve or 2 opposed vanes can cancel most of this out, and make servo's job easier.Another thing: how much transport delay is the Arduino imposing? I suspect this because Arduino is notorious for "bloatware lag", when you use standard libraries. (For example, to write a port bit requires only 2 clock cycles in the hardware, but if you use port write library, it requires over 100 cycles!) I assume you are writing to PWM register to drive servo. Servos don't really have the resolution to deal with this type of task. They have deadband and jitter even "when perfectly driven". Also check CAREFULLY the voltage regulation of the power the servo gets. Best is to have a local regulator on EACH servo.You could let the servo drive a mechanism that controls the setpoint of a valve linked to the bellows. Thus the servo rule: use local feedback when possible.Is the bellows hinged on one side? If not, the bellows could be rocking, causing changed signal from sonar (unless sonar is "looking" at bellows center).

Certainly not!!! I built the puncher in 1965! It was totally manually operated. It required hours to punch a roll. The most important roll I made was a "test roll" for debugging the action. At that time, I DID have a SINGLE transistor that I scrounged from a discarded "transistor radio" in the optical sensor on a robot designed to follow a line painted on the floor. I also built a "computer" regulating trains in an S-gauge layout, consisting of about 20 relays. The system was able to regulate the motion of 5 trains at once by controlling "blocks" and 2 switches (to route faster trains around slower ones).

Regarding your comment on regulating the amount of vacuum: in player pianos they have a bellows held open with a spring, as you have. Inside the bellows is a knife valve connecting to vacuum source. As the bellows closes (vacuum increasing inside), the knife valve chokes off the vacuum, providing regulation.Sonar beware! If air temperature changes, you will get shift. (Expect change of 1 part in 30 for 20 degrees F change. How much this effects your setup is determined by ratio of change in distance due to vacuum to total distance measured. Most sonars have minimum distance which I assume is about 1 foot. How that compares to amount of movement you have I do not know.) Safest thing to do is have a fixed target also "looked at" by the sonar. You regulate the RATIO of t...

Regarding your comment on regulating the amount of vacuum: in player pianos they have a bellows held open with a spring, as you have. Inside the bellows is a knife valve connecting to vacuum source. As the bellows closes (vacuum increasing inside), the knife valve chokes off the vacuum, providing regulation.Sonar beware! If air temperature changes, you will get shift. (Expect change of 1 part in 30 for 20 degrees F change. How much this effects your setup is determined by ratio of change in distance due to vacuum to total distance measured. Most sonars have minimum distance which I assume is about 1 foot. How that compares to amount of movement you have I do not know.) Safest thing to do is have a fixed target also "looked at" by the sonar. You regulate the RATIO of the 2 times measured, rather then compare one time against a constant. Humidity also has a lesser effect.You could also have dump valve mechanically linked to bellows. This is the ultimate in simplicity!Some info about player piano standards: roll 11 1/2" wide. 88 holes, spaced 9 to the inch. How do I know this? I built a roll puncher! Player piano response speed: 10 "hits" per second on a given note.

This is an awesome project! I know as I overhauled a player piano made in the 1920's. If I were designing this, I would "steal" ideas from player piano design, and use pneumatics to activate the keys. (Each pneumatic is a bellows about 1 x 3 inches with 1/2 inch movement. You stagger them in 3 rows to get them close enough for the keys.) You eliminate the noise problem. So now the solenoids can be tiny things that open small valves. You can drive them from multi-channel driver chips. You will not blow anything up if you accidentally activate all keys at once.If you study a piano action, great lengths are gone to, to get rid of noise. Every bearing is lined with felt, and everywhere 2 things contact, there is also felt.Regarding providing suction: you need to slow vacu...

This is an awesome project! I know as I overhauled a player piano made in the 1920's. If I were designing this, I would "steal" ideas from player piano design, and use pneumatics to activate the keys. (Each pneumatic is a bellows about 1 x 3 inches with 1/2 inch movement. You stagger them in 3 rows to get them close enough for the keys.) You eliminate the noise problem. So now the solenoids can be tiny things that open small valves. You can drive them from multi-channel driver chips. You will not blow anything up if you accidentally activate all keys at once.If you study a piano action, great lengths are gone to, to get rid of noise. Every bearing is lined with felt, and everywhere 2 things contact, there is also felt.Regarding providing suction: you need to slow vacuum cleaner down. You can use variac, or put inductors in series with it, or use a DC supply. That lowers power and wear & tear on vacuum (they are not made to run continuously!) to almost nothing, and gets rid of most noise so a padded box can do the rest. You will most likely need 30-40 volts on the vacuum to get the vacuum you need. Rather then tape hose in, make another flap-valve assembly on chest and connect vacuum to that with a more permanent connection. The organ will be able to be either manually pumped, or run on power, without needing to change connections. I did this for a war veteran (who lost one leg) so he could run his Story & Clark player piano (which I overhauled).Another thing to look at is the effect of the flyback diodes in the solenoids. They slow the release. One trick is to allow the flyback voltage to be higher (but still not high enough to damage FETS). Easiest way to do this is to put resistor in series with diode. For 1A solenoid current, this current will instantaneously flow in diode circuit. So each ohm you put in, is another reverse volt is allowed. 10 ohms added would allow 11 reverse volts, halving release time, while subjecting FETs to 23 volts at the instant switching off.Another thing I would do differently is to have the solenoids (or whatever other mover used) directly actuate the reed valves. That's the way player pianos work, and for best operation the keys are locked up to eliminate their inertia.

At its melting point, zinc is volatile! It fumes into the air, then oxidizes to a fine white powder which is readily inhaled.Workers in zinc smelting factories and brass foundries were known to get "zinc shakes". Campers who grill food on old galvanized refrigerator shelves also get poisoned (unless the shelf is heated red-hot in the fire first to boil off all the zinc).If you cast brass as a business, the EPA requires zinc-scrubbers on the chimney. The model railroad community has switched to manganese bronze for this reason.If you do one or a few coins, there is no worry, but it is best to do this outside to be safe.It is wise to understand the hazards of any operation you perform.

Be sure to state to get the zinc from "zinc-carbon cell", not "alkaline cell".Yes zinc-coated roofing nails could be used. But be sure the zinc coating is hot dipped (looks rough and crystalline, as on a roofing nail, not smooth and shiny). If it is not, the zinc will be so thin that the zinc will be etched from the steel before you have enough zinc ions in solution to electroplate on the coin.When heating the coin to alloy the zinc, be sure to do this in a well-ventilated area, as zinc heated to the melting point is volatile, will fume, and is somewhat toxic.

The zinc plate you got from the cell looks like it is from the older acid-based "zinc-carbon" of Laclanche cells. In the newer "alkalline" cells, the zinc is in powder form mixed with copper in the center electrode. Where did you get the cell you stripped the zinc sheet from? Did you get it from a foreign country?

If you remove the rotor from a shaded-pole motor and turn it on with full line voltage, it will quickly overheat! You are removing the path for the magnetic flux, which forces the motor to draw excessive current.

The "fan" in the base needs to develop more pressure then normal "propeller" fans can provide. Better would be a centrifugal "blower", which moves less air but at a greater pressure, to force the air through the slot. These can be purchased inexpensively like the usual "muffin" fans.

Use it for circuit board resist. For that, green color is best (shows against the copper), diluted with thinner. For wide traces, draw it directly on. For thin traces, color in an area, let dry, and scribe where the copper is to be etched away.

Make "engine finish" on metal shop projects. Us short pencil or cut off 2" long eraser end. Chuck in drill press. Place polished metal on press table, and "drill" with eraser, leaving a little swirl mark. Do repeatedly, overlapping marks.

Some comments about the process.IC sockets and connectors are some of the most heat-sensitive parts, and tend to warp. To prevent: connect mate (or put IC in socket) while desoldering, and let cool before unmating. Make sure IC put in socked doesn't have solder on leads. Put old EPROMS in large machined-pin sockets to support them. Pull the socket out by the EPROM.Sievert makes a "hot-air" torch burner that is perfect for this. It is hotter then a hot-air gun (which is too slow), but cooler then a direct flame.The secret is to pay attention to the heat flow. Heat moves up, so start at the bottom (and put more heat there). A piece of aluminum will not heat as quickly as plastic. A component with a heat-sink will be difficult to heat. Leads connecting to a ground plane ...

Some comments about the process.IC sockets and connectors are some of the most heat-sensitive parts, and tend to warp. To prevent: connect mate (or put IC in socket) while desoldering, and let cool before unmating. Make sure IC put in socked doesn't have solder on leads. Put old EPROMS in large machined-pin sockets to support them. Pull the socket out by the EPROM.Sievert makes a "hot-air" torch burner that is perfect for this. It is hotter then a hot-air gun (which is too slow), but cooler then a direct flame.The secret is to pay attention to the heat flow. Heat moves up, so start at the bottom (and put more heat there). A piece of aluminum will not heat as quickly as plastic. A component with a heat-sink will be difficult to heat. Leads connecting to a ground plane will require more heat, leading to possible overheating of other adjacent leads. Watch out for holes or slots in the board which could allow flame through. If parts hang over the edge of the board, hold another board against the edge to prevent flame from wrapping over the edge.Board-mounted heatsinks are almost impossible to get out by heating leads. Unfasten transistor first from sink, strip transistor off board, then apply torch flame to top-side of heat sink until it is almost at solder melt temperature, then finish with heat on leads from bottom-side.If heat or other damage is evident on a component, throw it away immediately so it doesn't get mixed in with the others.Do not strike board to mass-strip parts. Solder will splatter over the parts.Use a low, long cardboard box to catch the parts. Cardboard won't melt, and is replaceable. As soon as the part lands in the box, let it cool for a moment, then sweep it toward the other end of the box. This way if solder splatters, the parts will be out of the way.Practice on boards which don't have parts you want. Test-remove components you don't want, but are similar to those you want. Skilled application of the heat, as well as "reading" the temperature, are a must, and will be developed with experience. Hidden things like inner planes will affect heat flow.For DIP ICs and thru-lead parts: if you heat and pull it out just as the solder melts, there will be a blob on each lead right at the board surface, which you will have to clean off later. Better: rock the part as you are heating until you feel it is free, wait a second or 2 for the heat to come up the leads a little, then pull out a little, push back in, then pull out. The pull and push transfers heat from the lead (in contact with flame) to the front-side. The solder blob will not form, and the leads will come out clean.Surface-mount parts that have sat around in damp environment absorb moisture. That moisture turns to steam inside the part and damages it. Bake board at 200F for several hours to drive out this moisture before stripping. Remove all large electrolytic caps and batteries of any kind before torch stripping or baking as they can explode!Solid tantalum caps can ignite, and when they do, they burn white hot!If ribbon cables are connected to board and you want connectors, leave cables connected while the part stripping is done. This supports connectors from warping (the ribbons may be scorched).

TATP is an explosive, not a rocket fuel grain. PLEASE DO NOT MAKE TATP! Your procedure omits the most important step, keeping the mix below 10 degrees C during the reaction. if you don't, you make a related compound that is spontaneously explosive!This stuff (even when properly made) is dangerous, even when ignited in the open! It is used by terrorists for bombs! Please don't make this stuff!Flash paper is made of nitrocellulose, not TATP. Nitrocellulose is energetically flammable, but not explosive unless confined.

You need to ignite the engine at the end where you inject the oxygen (could be done with electric igniter inserted all the way in). The "rocket's" success isn't verified unless you measure its thrust-time product.Be careful, the pipe could explode! You should have secondary containment.Be careful

Hydrochloric acid will dissolve the rust. Apply dropwise and keep wet for an hour.

Do you know about releasable zip ties?https://www.parts-express.com/Search.aspx?keyword=...

Do you know about releasable zip ties?https://www.parts-express.com/Search.aspx?keyword=...

Various schemes are proposed for sensing the magnetic field (reed switch, hall sensor), but the simplest one has not been mentioned: induction in a coil when the field changes. Look up this toy:www.amazon.com/s/?ie=UTF8&keywords=top+secret+toy&...The original versions of this toy have a nail with a center-tapped coil wound on it, mounted vertically under the center of the base. Also there is an NPN transistor (2N3904) and a 9 volt transistor battery. one section of the coil is in series with the transistor's collector, and that is across the battery. The other coil is across the emitter-base of the transistor. The coils are phased so when the transistor turns on, the mutual induction to the E-B coil turns the transistor on further. In the presence of the initially spinning...

Various schemes are proposed for sensing the magnetic field (reed switch, hall sensor), but the simplest one has not been mentioned: induction in a coil when the field changes. Look up this toy:www.amazon.com/s/?ie=UTF8&keywords=top+secret+toy&...The original versions of this toy have a nail with a center-tapped coil wound on it, mounted vertically under the center of the base. Also there is an NPN transistor (2N3904) and a 9 volt transistor battery. one section of the coil is in series with the transistor's collector, and that is across the battery. The other coil is across the emitter-base of the transistor. The coils are phased so when the transistor turns on, the mutual induction to the E-B coil turns the transistor on further. In the presence of the initially spinning top, brief current pulses to the coil keep the top spinning (for about 2 weeks on a 9V battery).This same circuit could be used for the spinner accelerator. The drive coil would want to have fewer turns of heavier wire, as there is more friction on the spinner versus the top. This patent on the top explains the circuit in more detail.http://www.freepatentsonline.com/3783550.pdfThe advantages of this scheme are that no on/off switch is needed (the circuit automatically shuts down when the spinner is removed), an absolute minimum of parts are needed, and these are inexpensive.

You might want to think about another design I made. One problem I had when designing this type of "ironless" motor is the flux curving back between the poles without linking any coil. The Halbach magnet helps limit this happening in the plane of the magnet, but does nothing to prevent it in the air gap. Instead of having magnet on only 1 side of the coil, have magnets on both inside and outside the coils. The flux is now 'thrown" in from both sides. Now I agree this is difficult to arrange mechanically...unless you change things a bit. What I did was to "twist everything 90 degrees" and have the flux axial, and the current radial. The rotor consists of 2 pancake arrays of magnets, embedded in 2 aluminum discs, each backed with a ring of iron, and the sta...

You might want to think about another design I made. One problem I had when designing this type of "ironless" motor is the flux curving back between the poles without linking any coil. The Halbach magnet helps limit this happening in the plane of the magnet, but does nothing to prevent it in the air gap. Instead of having magnet on only 1 side of the coil, have magnets on both inside and outside the coils. The flux is now 'thrown" in from both sides. Now I agree this is difficult to arrange mechanically...unless you change things a bit. What I did was to "twist everything 90 degrees" and have the flux axial, and the current radial. The rotor consists of 2 pancake arrays of magnets, embedded in 2 aluminum discs, each backed with a ring of iron, and the stator a slab with coils embedded inside.(I built alternator this way to make 120VAC 3 phase 80W, 90% efficiency, to be rectified into 168VDC and fed into "world-wide" power supply. Alternator ran on 1HP engine at 3000 RPM. No circuit breaker was needed as engine stalled if load got too high. Geometry was 4" diameter, 16 poles, 12 coils in 3 sets of 4 per phase star. Weight 1.1 pound. Magnets 1/2 inch square, 1/4inch thick each side, 32 total. No Halbach array.)Disadvantage of that scheme is it is difficult to arrange for crossing end-turns of the phase coils, forcing you to have only 1 phase in a given sector of the air-gap. But your most ingenious 3D printing guide slots (yours is the best design I have seen to deal with this problem!) could most likely allow crossing turns within the stator plate. On purpose, you would make a 3D print for the stator that is weak and porous, wind in the coils, and impregnate with epoxy. (My opinion to the secret of good 3D prints is the post-processing. I am wearing Mykita eyeglass frames made this way. They are strong enough to not need reinforcing wire in the temples.)

To get the print on the cardboard, place the mirrored LASER print face-down on the cardboard, and tape in place at the corners. Pour a few milliliters of acetone into a small cup (not plastic!). Dip small rag into it, just getting a spot on the rag damp, not wet, with the acetone. Gently rub the back of the print. The paper will darken (as paper does when wet), but don't soak; just barely wet until you see the paper darken a little. You will be able to see the black through the paper; keep rubbing with a dry rag until the acetone evaporates, and the paper becomes white again. Carefully peel the paper off the cardboard; you should see the print on the cardboard. If the paper sticks and threatens to split, re-wet that spot with a little acetone and separate, Cut the cardboard in t...

To get the print on the cardboard, place the mirrored LASER print face-down on the cardboard, and tape in place at the corners. Pour a few milliliters of acetone into a small cup (not plastic!). Dip small rag into it, just getting a spot on the rag damp, not wet, with the acetone. Gently rub the back of the print. The paper will darken (as paper does when wet), but don't soak; just barely wet until you see the paper darken a little. You will be able to see the black through the paper; keep rubbing with a dry rag until the acetone evaporates, and the paper becomes white again. Carefully peel the paper off the cardboard; you should see the print on the cardboard. If the paper sticks and threatens to split, re-wet that spot with a little acetone and separate, Cut the cardboard in the usual way. To finish, spray-paint the cardboard (tan if you want natural color). This will cover any ink or dirt marks.Keeping the amount of acetone small will minimize the fire hazard.

Awesome design! Here are some suggestions to improve the performance. For the rotor, you really need a metal ring on the outside. The tension in the plastic at 8000 RPM is on the 100's of pounds. plastic slowly yields to this stress, and will fail. Preferably, a steel shell should be used both to withstand the forces, and to provide a return path for the magnetic flux. Since your rotor is made in 2 parts, you can omit plastic and put the ring in place, between the 2 halves.You also need a "real" flux-return path on the inside of the windings. This path must be laminated. It could be provided by winding in steel wire, as making laminations is difficult.I noticed a "howling" sound when the motor is running. This is due to harmonic noise, and adds to the loss. ...

Awesome design! Here are some suggestions to improve the performance. For the rotor, you really need a metal ring on the outside. The tension in the plastic at 8000 RPM is on the 100's of pounds. plastic slowly yields to this stress, and will fail. Preferably, a steel shell should be used both to withstand the forces, and to provide a return path for the magnetic flux. Since your rotor is made in 2 parts, you can omit plastic and put the ring in place, between the 2 halves.You also need a "real" flux-return path on the inside of the windings. This path must be laminated. It could be provided by winding in steel wire, as making laminations is difficult.I noticed a "howling" sound when the motor is running. This is due to harmonic noise, and adds to the loss. You can reduce the harmonic noise by slightly skewing the windings. Probably about half of one of your slot-spacings would be right.Regarding the magnets: they should not show a wide variation in power! I would look for better quality magnets, such as from K&J Magnetics.

Cooling the diode is neither difficult nor expensive. You use standard hardware for mounting transistors, which routinely must be isolated from the grounded heatsink. You bolt the diode down, with insulating shoulder washers under the heads of the bolts, and use mica or kapton insulators with heatsink grease on each side.I don't understand how a "diode route" solved this problem. Please explain. Another way to solve this is to float the laser driver circuitry off ground, and convey the on/off signal to it with an opto-isolator or level-shifter.You must be careful, as shorting the laser diode's case to ground can bridge the driver, sending huge currents into the laser diode. This transforms the laser diode into a "dark-emitting laser" which emits energy that cann...

Cooling the diode is neither difficult nor expensive. You use standard hardware for mounting transistors, which routinely must be isolated from the grounded heatsink. You bolt the diode down, with insulating shoulder washers under the heads of the bolts, and use mica or kapton insulators with heatsink grease on each side.I don't understand how a "diode route" solved this problem. Please explain. Another way to solve this is to float the laser driver circuitry off ground, and convey the on/off signal to it with an opto-isolator or level-shifter.You must be careful, as shorting the laser diode's case to ground can bridge the driver, sending huge currents into the laser diode. This transforms the laser diode into a "dark-emitting laser" which emits energy that cannot be detected by any known device.

Some lasers have the diode's anode tied to the case, which is usually tied to the positive supply in the driver electronics. Either you need to insulate the case from ground (but have a scheme for heat sinking) or use an isolated supply to power that laser.

One thing about laser-cutting (and for that matter, any type of cutting) Plexiglas is that the cut process makes heat, and that heat melts the plastic at the surface of the cut ("heat affected zone"). On cooling, this zone solidifies, and then tries to contract, but the unaffected plastic "braces" and forbids the contraction, leading to tensile stress at the cut surfaces, and lower compression stress in the bulk behind the cut surfaces.Plastic, unlike metal, "doesn't like" continuous tensile stress, and will crack in time, especially if exposed to the elements outdoors or bright light indoors. The right thing to do is to anneal the plastic sheets immediately after cutting (many references on the web how to do this). This relieves the internal stress. (T...

One thing about laser-cutting (and for that matter, any type of cutting) Plexiglas is that the cut process makes heat, and that heat melts the plastic at the surface of the cut ("heat affected zone"). On cooling, this zone solidifies, and then tries to contract, but the unaffected plastic "braces" and forbids the contraction, leading to tensile stress at the cut surfaces, and lower compression stress in the bulk behind the cut surfaces.Plastic, unlike metal, "doesn't like" continuous tensile stress, and will crack in time, especially if exposed to the elements outdoors or bright light indoors. The right thing to do is to anneal the plastic sheets immediately after cutting (many references on the web how to do this). This relieves the internal stress. (This stress can be seen with a polariscope). This requires an oven that is large enough to hold the largest piece, with maximum processing temperatures around 250F. (You can kludge something together to do the annealing, might be a good future Instructable).You can do other things to lessen the likelihood of cracking. Us only cast, not extruded Plexiglas that is free of internal stress to start with. Have the cutting done in a warm room. Do not cut cold plastic! Cracks will start in sharp concave corners, such as at the root of your mortise joints. (So the advantage of laser cutters "having zero cutter radius" should not be taken advantage of!) Pretend you are cutting with a 1/8" cutter, and add "crack-stop" circles at the root of the mortises. On non-fitting inside corners, put a fillet radius.You can make a polariscope from a cheap pair of polarized sunglasses. Take the lenses out, and put one lens on each side of the plastic to be inspected, and rotate one lens so the majority of the area is dark, with illumination from behind.You can take advantage of this project to bring together industrial engineering and art!

Some advise. You will miss holes and spots on a wall in bad repair. Do the repairs you see as described, and then prime everything (I use oil-based paint because it adheres better). Now you have a uniform color and can see the missed spots. Fix those, and re-prime over those spots.

I am a little bewildered, as all the lenses I have seen for DLSRs, such as my Olympus E-PLE micro 2/3rds camera/lenses, have no aperture lever (or anything else mechanically connected to the lens), so it is not possible to open the aperture without an electrical connection between the camera body and the lens. All the mechanical movements in the lens are done by electric actuators.Is this not true for the "full size" mirrorless camera/lenses?

This is not "chip on board". What you show is "surface-mount PACKAGED chips soldered onto a circuit board". "Chip on board" means the LED chips (the die are naked) are directly (usually) epoxied to the board and a wirebonder welds tiny wires from the die to the board for the electrical connection. The assembly is then covered over with a blob of transparent epoxy. There is no solder. Chip on board is not repairable. For this reason I avoid lighting products boasting of "chip on board". A similar scheme is used to mount micro-controllers in cheap toys. They are non-repairable!

COB IS used on LED lighting, and if you are smart, you will avoid lighting products boasting of this (they usually claim it as a feature).

Weighing isn't necessarily "exact" either. Packing density affects flour quantity measured by volume, flour initial water content affects quantity when weighed. Damp flour has less flour per unit weight then dry flour!As for salt, are you trying to kill everyone consuming the bread? I make bread without salt all the time. 20g of salt is way too much sodium! Why is salt needed in a pizza where salt-laden sauce, cheese, pepperoni, etc. are added on top? Entrees made from multiple ingredients should have salt in ONE ingredient. I am not interested in gorging water for the next 2 hours after eating the bread of pizza!

You may want to explore using Hydrocal gypsum cement instead of mortar. it is easier to handle in thin sections, as it is stronger when set.When you use a "dry mix" to get the look you want (either mortar or gypsum cement), the result may be weaker as there is not enough water present to complete the cure. The solution is to make with the dry mix as usual, allow to set, then soak the whole thing in a bucket of water for an hour before lifting out and drying.Anther thing about the lithium battery: your charger "protects" the battery from over charging, but nothing protects the battery from over discharging (if you left the light on too long). You can buy modules (you connect between the battery and the LED) that control discharge as well as charging. Some batterie...

You may want to explore using Hydrocal gypsum cement instead of mortar. it is easier to handle in thin sections, as it is stronger when set.When you use a "dry mix" to get the look you want (either mortar or gypsum cement), the result may be weaker as there is not enough water present to complete the cure. The solution is to make with the dry mix as usual, allow to set, then soak the whole thing in a bucket of water for an hour before lifting out and drying.Anther thing about the lithium battery: your charger "protects" the battery from over charging, but nothing protects the battery from over discharging (if you left the light on too long). You can buy modules (you connect between the battery and the LED) that control discharge as well as charging. Some batteries come with such modules pre-installed.

A word about safety. First, you need to establish that the glass is not under stress. You can do this by building a polariscope. Get a cheap pair of polarized sunglasses, and remove the lenses. Set up in following order: light source, diffuser, lens #1, glass being inspected, Lens #2, eye. Rotate the lenses so without glass in place view is dark, then insert glass between lenses. if view remains dark or dim, stress is low and it is safe to drill. Dazzling dark and white bands indicates stress. Don't drill! A lot of modern glass pieces are "tempered" (such as newer "Pyrex" glass kitchenware) and will shatter if drilled.Back-up pad: you do not want a "soft" pad! It will give, then release at the moment of break-through. You want something rigid but...

A word about safety. First, you need to establish that the glass is not under stress. You can do this by building a polariscope. Get a cheap pair of polarized sunglasses, and remove the lenses. Set up in following order: light source, diffuser, lens #1, glass being inspected, Lens #2, eye. Rotate the lenses so without glass in place view is dark, then insert glass between lenses. if view remains dark or dim, stress is low and it is safe to drill. Dazzling dark and white bands indicates stress. Don't drill! A lot of modern glass pieces are "tempered" (such as newer "Pyrex" glass kitchenware) and will shatter if drilled.Back-up pad: you do not want a "soft" pad! It will give, then release at the moment of break-through. You want something rigid but not so hard. Wood is the excellent choice. For irregular glass piece, cut wood scrap to support only right below where the drill breaks through. Fasten this to drill press table lined up with drill.If possible, drill from inside to outside, even if you must rig an extension onto the drill bit. If the outside is flat in the region of hole break-through, hot-melt a glass scrap on so the drill can go into the scrap part-way. Bottle can also serve as a reservoir for the coolant. The bottom of the bottle is probably the safest place to drill if it is not stressed. The thicker the better!Regarding the coolant: on core drills (the best type to use), the coolant needs to get inside the core. If you are drilling a bottle bottom from the inside, drill a small hole crosswise into the side of the drill bit just above the cutting end so coolant can get in. Better yet: extend drill bit with a long piece of tubing. Plug chucking end. Near chucking end, drill several small holes crosswise through tube. Fit plastic fitting around this with pressurized water feed, which enters tubing at holes, goes down through the center of the bit and continuously flushes chips out of hole.Watch drill bit carefully. "Milky" appearance says drill is working. If water clears, diamond cutting edge is clogged (with the nickel plating it is held in place with) and needs clearing. Drill brick scrap for a moment, pressing harder and skidding drill sideways. Contrary to popular belief, diamond drills work best at high speed and low pressure IF coolant is present AT THE CUTTING EDGE. If not pressure fed, lift drill every second to allow coolant to flow back in. Any smoking or dusting indicates dryness; lift more often! This is not true of carbide spade bits. Coolant can get in easier. They must turn slowly and have heavier pressure or they will just rub and dull (sound of the drill will tell). They need frequent sharpening. It is almost mandatory to have back-up glass to prevent shattering at break-through.Regarding gloves: gloves are usually a no-no when working on a machine with rotating parts. Be careful not to get caught into the machinery!

Whether the screw is on wood, metal, or plastic, heat can free it. Get an old screwdriver that fits the screw. Heat the tip red hot, with a propane torch, then immediately touch it to the screw. You may need to repeat the reheating of the driver and touching it to the screw to get things hot enough. In wood, the surrounding wood will dry out and char, loosening its grip. In metal, the heat will soften any "lock-tite" that was put in at assembly. Also, the thermal shock of suddenly being heated will disrupt the screw-to-metal bond. In plastic, a thin film of plastic will melt around the screw, allowing for its quick removal without damage to the surrounding plastic (as on an access cover in a laptop computer). It is essential to act immediately before the heat spreads. ...

Whether the screw is on wood, metal, or plastic, heat can free it. Get an old screwdriver that fits the screw. Heat the tip red hot, with a propane torch, then immediately touch it to the screw. You may need to repeat the reheating of the driver and touching it to the screw to get things hot enough. In wood, the surrounding wood will dry out and char, loosening its grip. In metal, the heat will soften any "lock-tite" that was put in at assembly. Also, the thermal shock of suddenly being heated will disrupt the screw-to-metal bond. In plastic, a thin film of plastic will melt around the screw, allowing for its quick removal without damage to the surrounding plastic (as on an access cover in a laptop computer). It is essential to act immediately before the heat spreads. If the attempt doesn't immediately work, allow everything to completely cool before trying again. Contrary to instinct, it is important to have the driver at least red hot! The secret is to apply the heat so quickly that it doesn't have a chance to spread.If the screw turns freely, but won't come out (as in the video) jam a thin-bladed screwdriver under the side of the head while turning. For easier cases, pushing sideways on the driver causes the screw to engage on one side and backing out.

Don't you have trouble with splitting as the wood dries for such thick pieces with "crazy" grain? If I were doing this, I would cut the tree green, rough the bowl out, PEG treat it, then dry and finish turn. Normally wood logs air dried for years have built-up stress, if they have not split already.

You say the electronics in the dome "are completely independent of the base, no wires to tangle". Does that mean that there is a separate battery in the dome to power the electronics in it, or is there a set of leads to provide power from the base?

The secret to engraving acrylic plastic is using a sharp carbide cutter, running the cutter insanely slowly (2000 RPM for 1/16" cutter), and feeding very slow. If you do, you will get a mirror finish in the cut and no melting at all. Are your cuts made from the backside? (Back cuts throw more light forward). A V-cut is best.

Another thing about annealing aluminum. Aluminum, unlike iron, has annealing temperature dangerously close to melting point, and aluminum doesn't "show colors" like iron when heated. So you risk melting the thin sheet. One way to get temperature indication is to cut air to torch so it smokes, and lightly soot the aluminum. Then, admit air and start the anneal, slowly. You are done when the carbon just burns off. Don't smoke the metal heavily, or the warning will come too late!If you use 6061 alloy, you can re-heat treat it back to hardness by heating in oven at 350F for 24 hours, then allowing it to cool in open air. Several weeks later, it will be hard to "T6" condition.

You comment about heating and to "stamp quickly" as the metal is cooling. I maintain that no matter how fast you stamp, the metal will have cooled. What made it work is that the metal was annealed by the heating step, and it doesn't matter how long you wait after annealing; the metal will flow better.

Was the dead tree outside? If so, it will still have a high water content, which when brought inside, will shrink and crack. The recommended procedure in this case is to soak in PEG until hydrated, then dry. This can take some time.Otherwise, you can rough oversize, then wait to dry to see if it cracks, and discard if it does.

As this robot is propelled by the center of gravity shift, it would work better if the weight on top (the internal magnets coupling to the head) were reduced. (This is evident in your videos, as the head swings through a large angle before the robot moves). Use rare-earth magnets there, as well on the head. Add lead ballast on the internal "cart" as low as possible, or add more batteries, again as low as possible.When sanding the outside of the body, use a trick that optic fabricators use. After you make the body, make a "tool" by putting plastic wrap over a part of the body, and cast a concave paper-mache tool about 1/4th the diameter of the ball. After this sets, remove the wrap, and rub it over the body, rotating as you do so. Both it and the body will abrad...

As this robot is propelled by the center of gravity shift, it would work better if the weight on top (the internal magnets coupling to the head) were reduced. (This is evident in your videos, as the head swings through a large angle before the robot moves). Use rare-earth magnets there, as well on the head. Add lead ballast on the internal "cart" as low as possible, or add more batteries, again as low as possible.When sanding the outside of the body, use a trick that optic fabricators use. After you make the body, make a "tool" by putting plastic wrap over a part of the body, and cast a concave paper-mache tool about 1/4th the diameter of the ball. After this sets, remove the wrap, and rub it over the body, rotating as you do so. Both it and the body will abrade to match each other, forming the body into a perfect sphere.How do you connect charger? Do you have a small hole in the body for the cord?

These rust strippers contain hydrochloric acid. This acid will fume and cause resting of all iron/steel in the shop, so do outside or ventilate thoroughly. After using the acid-containing product and wiping off (and immediately carrying used rags outside), I would wipe with damp rag containing some dilute ammonia/water. This neutralizes any residual acid, both on the surface and in the air. Then apply a liberal application of WD-40 to the surface of this, and any other tools in the same room, to get rid of any moisture.Do not store the bottle of rust remover in the shop! Its fumes will cause rusting of all tools in the shop.

Way to avoid paint run-under of masking; after applying masking, apply light coat of first color and allow to dry. This will run under and seal masking. Then paint with second color.

Too late! GE patented this method of charging electric toothbrushes in 1959.

Your comment about "experimenting with the secondary", but your illustrations show experimenting with the primary.

Boil the water first to remove dissolved air.

Stand the bottle at a 45 degree angle in the water, keeping the water level below the bottom of the label, but above the hole. Fill the interior to the same level as the outside when the bottle is so positioned.

No need to fiddle around with putty dams!Put the whole bottle in a tray flooded with water so the side of the bottle is just covered with water. This cools the glass as it is being cut, both from the inside and the outside, and totally eliminates the glass dust. If you use a battery-powered drill, there is no shock hazard doing this.You can also use the diamond core bits, which cut out only a ring of material, and so cut faster and with less heating. Run the RPM higher with these bits.You must completely dry the interior of the bottle before adding the lights.

I find it easier to fit 2 wood plugs into the ends of the pipe with 1/4' holes in them, and insert a 1/4-20 all-thread rod through with nuts on the ends. A wood crank handle is affixed to one end of the rod with nuts. a frame made of a piece of 2 x 4 (the "lathe bed") and 2 scraps of plywood on the ends (for the "headstock" and "tailstock"). because you are hand cranking, you have more control, and can recover from crossed turns, etc. Also advisable is to add a friction brake to hold things in position when not holding the crank. This can be built on any scale, but for really large coils, 2 people work best. The spray painting can also be done while the coil is on the 'lathe".

In the photo you have the magnet wire contacting the aluminum member while winding the coil. You should avoid having the wire contact anything other then itself, wood, or other soft materials or your skin, as you may scrape the insulation. Anything it contacts should be rounded. In your case a strip of masking tape over the metal edge will fix this.When cleaning the pipe, use acetone after your other cleaning. This will soften the pipe a little and enhance adhesion. You may want to pre-coat the pipe with the spray before winding.Also be sure to check the inside of the pipe for dirt, and prepare the means of end-termination before starting the winding.

Normally, these motor controllers use a standard servo PWM signal to operate. You can use a micro-controller, or a 555 timer with a pot control to generate this signal. Typically, signal goes between 0 and 5 volts, and has a rep rate of about 60 Hz (not critical), and a "high time" that varies between 1 milli-second (for extreme "low"end of control range) to 2 milli-seconds (for the extreme "high" end of control range).

There are many more details of the motor construction that determine the way the magnets must be placed. The winding configuration must be such that all the coils in a phase have the same (or similar) relation to the magnets, or the forces will not "add up" within the motor. Most motors of this type are of "high pole count" type. Each coil links only the iron between 2 adjacent slots. There are usually either 6, 9 or 12 slots. The number of magnets must be even and "close" to the number of slots. So 9 slots/8 or 10 poles, and 12 slots/14 or 16 poles is common. The number of poles must have at least one factor of 3 not common to the number of slots (so, for example, 9 slots/12 poles is OK as they have one factor of 3 in common, but the 9 has a factor ...

There are many more details of the motor construction that determine the way the magnets must be placed. The winding configuration must be such that all the coils in a phase have the same (or similar) relation to the magnets, or the forces will not "add up" within the motor. Most motors of this type are of "high pole count" type. Each coil links only the iron between 2 adjacent slots. There are usually either 6, 9 or 12 slots. The number of magnets must be even and "close" to the number of slots. So 9 slots/8 or 10 poles, and 12 slots/14 or 16 poles is common. The number of poles must have at least one factor of 3 not common to the number of slots (so, for example, 9 slots/12 poles is OK as they have one factor of 3 in common, but the 9 has a factor of 3 "left over" that 12/3 does not have).The safest thing to do is match the number of poles the original motor had, unless you want to study the details of the winding.

CAUTION! If you choose to use acid/hydrogen peroxide mix for etching, be sure you COMPLETELY rinse it off with running water, then dry COMPLETELY, before applying the acetone. If you don't, you can accidentally end up with acetone peroxide, which is EXPLOSIVE!NEVER allow acetone to mix with hydrochloric acid and hydrogen peroxide!

That is explained in detail in my previous comment. My guess it will be in the 0.01 uF range. It is selected to resonate with the primary alone, at the same frequency that the secondary resonates with its top loading sphere only, with the bottom grounded. I can't give value, as that depends upon the diameter of the secondary, number and spacing of turns, and the loading capacitance of the sphere you choose. I would have to build an exact "carbon copy" of the coil to determine that. That's why I included the long-winded explanation of how to determine the value in the previous comment.If you don't have test equipment, you can build an oscillator from a CMOS chip, a capacitor, a resistor, and a pot. Wave shape is not important, but stable amplitude is, which a CMOS oscilla...

That is explained in detail in my previous comment. My guess it will be in the 0.01 uF range. It is selected to resonate with the primary alone, at the same frequency that the secondary resonates with its top loading sphere only, with the bottom grounded. I can't give value, as that depends upon the diameter of the secondary, number and spacing of turns, and the loading capacitance of the sphere you choose. I would have to build an exact "carbon copy" of the coil to determine that. That's why I included the long-winded explanation of how to determine the value in the previous comment.If you don't have test equipment, you can build an oscillator from a CMOS chip, a capacitor, a resistor, and a pot. Wave shape is not important, but stable amplitude is, which a CMOS oscillator will give you. The important thing is that you can "make the same frequency twice" by marking the pot position when you test the secondary, and tuning the primary to "dip" at the same pot setting.

The unmarked capacitor is selected to tune the primary's resonance to match that of the secondary. Diode, earth ground, and sphere on top are shown. What you do is: wind secondary, and put sphere on top. Drive bottom end of primary with signal generator (or kludged-together oscillator) connected through a 1K resistor. Ground other terminal of generator. Do not make any other connections. Put meter from ground to the 1K/secondary node. Turn on generator to a couple of volts. When you are out of resonance, meter will read generator's voltage (as expected, you have no circuit "connection"). Sweep the generator. When you hit resonance, the meter will show a dip in voltage. (This should happen at about 1 MHz). You know you have it when waving hands around secondary dist...

The unmarked capacitor is selected to tune the primary's resonance to match that of the secondary. Diode, earth ground, and sphere on top are shown. What you do is: wind secondary, and put sphere on top. Drive bottom end of primary with signal generator (or kludged-together oscillator) connected through a 1K resistor. Ground other terminal of generator. Do not make any other connections. Put meter from ground to the 1K/secondary node. Turn on generator to a couple of volts. When you are out of resonance, meter will read generator's voltage (as expected, you have no circuit "connection"). Sweep the generator. When you hit resonance, the meter will show a dip in voltage. (This should happen at about 1 MHz). You know you have it when waving hands around secondary disturbs meter reading.Wind the primary over the secondary, tape it, and then slip it off the secondary, but keep the form intact. Connect cap in series with primary, and sweep with generator as for secondary, except "far end" of primary is grounded. Adjust cap value until primary resonates at same freq as secondary.Slip primary back on secondary, connect cap in parallel with primary, and proceed with Tesla coil assembly/test.

I made the cannon from aluminum sheet, scaled up some from "Airzooka" toy, and put a large long-throw subwoofer driver. I found the optimum pulse shape to be complicated by experiment (involving a back movement followed by front movement, followed by back).

Problem is that inner beaker will try to float, a lot! You will need lead weights in inner beaker.

The trouble, nowadays, that is not good enough! "Perfectly good" boards twist and bend up into wood only fit for the fire-pit in a few months. The only thing that can't happen is more knots "move in"! What you need at the lumberyard, is a crystal ball!