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Everything posted by Enthalpy

  1. Ocarina, Xun, Hun

    At low notes, all flutes, recorders, ocarinas... take more throughput but less airspeed hence pressure. The organ copes with that but the limited capacity of human lungs can't. While the piccolo's treble are satisfying and pass over a symphonic orchestra, the soprano flute's first octave is too weak, and to hear an alto flute, the orchestra must whisper. I suggest to multiply the throughput with a "Venturi" (...it's the usual name) like a bladeless fan does https://en.wikipedia.org/wiki/Bladeless_fan as the lungs provide easily more pressure than the jet needs. Dyson claim to multiply the flow by 15 in their fan, that would be fantastic for flutes. How quickly the big flow reacts is an interrogation. The sketched construction can be rectangular, wide and thin, where the breathpipe passes successively on both sides. The pipe could make a circle, a torus, pass several times to mix better with atmospheric air... or the breath could produce a swirl in a cylindrical tube like industrial designs do. A chamber shall dampen the turbulence before the nozzle and may contain obstacles. This applies directly to the instruments with a nozzle: the recorder, the ocarina, and the many I ignore. The xun, hun and tsuchibue with a nozzle would become ocarinas. The multiplier can combine with the already suggested variable fipple. Recorders too can get a wide bore, huge tone holes and some adequate fingerings as Boehm did for the flute, possibly with a metal body. If the resulting instrument plays louder than a low flute, it would be a reason to use it instead. Could the musician hold the multiplier (partly) in the mouth? He could then control with the jaw the variable fipple, if any, and maybe control the blowing angle. One or several pipes would bring atmospheric air in the mouth. The chamber's size constraints the blowhole's position, for instance if playing a flute or a xun and similar. Marc Schaefer, aka Enthalpy
  2. Ocarina, Xun, Hun

    Hello music lovers (and haters too if any)! The ocarina has an embouchure resembling a recorder coupled with a Helmholtz resonator instead of a tube shortened by side holes Menaglio and more manufacturers ocarina on en.wiki, es.wiki, it.wiki It's often made of terracotta and is very cheap among wind instruments. The fipple saves long training, and some fingering charts resemble the recorder. https://en.wikipedia.org/wiki/Fipple But the range is short, about 1.5 octave, and the instrument lacks horribly power, more so at the low notes. Though, a glass bottle, which is a Helmholtz resonator too, plays much stronger than an alto flute at the same height for instance. So here are suggestions for the ocarina, untested and not fully justified. Let wide long note holes replace the narrow short ones. Keep the geometric L/S ratio that defines the inductance (each end of L gets a correction ~0.3*D). Round the ends. Viscosity losses drop, which may produce a stronger sound, possibly by adapting the fipple. Losses at the blow hole or wedge can be reduced too: a glass bottle outperforms a recorder. The limit to wide long tone holes is their volume, which adds to the cavity. And if you put the hole lengths in series, you get a recorder, not an ocarina. Rearrange the fingerings and holes to open fewer holes, but bigger. Viscosity losses drop. Proper intonation isn't trivial to design. Let the musicican define the air jet thickness. After training, he can blow on the wedge directly with his lips. The Xun and Hun do it Xun and Hun at en.wiki hear on the record the even strength over 1.5 octave. Thicker and rectangular blow hole as on the flute, longer note holes? Or use a moveable of deformable fipple that directs properly a jet of adjustable thickness. This would apply to recorders too. If the parts always aim adequately, playing will be much easier than with the bare lips. Marc Schaefer, aka Enthalpy
  3. Ocarina, Xun, Hun

    I suggested here on December 09, 2018 a moveable of deformable fipple to vary the thickness of the jet sent to the wedge. Here I propose an example of a variable fipple: The musician presses together with his teeth the mobile parts drawn darker. This controls the jet thickness. Here elastomer parts, drawn red, give elasticity and tightness. Natural rubber doesn't creep under permanent compression and resists humidity. The elastomer gets harder when it's thinner and wider. This helps control the jet when thinner. Two mobile parts define the jet thicknes, at the top and the bottom: the relative stiffness of the upper and lower elastomer parts define how the jet moves vertically with its thickness, or avoid this movement. The part drawn lighter is fixed to the wedge, directly or not, and may be the same part or not. Other designs are possible, especially if giving up the nonlinear compression. The mobile parts could be elastic and fixed with the immobile ones, possibly a single part. Or slopes could define the vertical movements of the mobile parts. Though, I like the control by the musician's jaw, as his hands and fingers are already busy. Up to now on the recorder and ocarina, the musician can only blow stronger or softer to choose the resonance mode or produce a sound in the first place. On the flute, xun, hun, tsuchibue, he controls additionally the jet thickness to play low notes stronger and high notes softer, after years of training. The variable fipple shall do that more easily, especially as it aims properly at the wedge, controls a thin jet easily, and keeps a good jet width. It hopefully keeps the recorder and ocarina almost as easy to play and gives them more possibilities. The xun, hun, tsuchibue equipped with a variable fipple would be ocarinas. Should flutists use such a fipple, fixed at the instrument or hold in the mouth? I doubt it. To produce strong low notes, flutists incline the jet more, starting higher and aiming lower, which is difficult to mimic by mechanical design. Marc Schaefer, aka Enthalpy
  4. Quick Electric Machines

    Hello, heirs of James Clerk, Nikola and the others! It is well known, but by too few people : in an electric machine, only the force means losses and heavy parts, the speed comes for free. When a motor or generator runs quickly, say 50 or 100m/s at a power plant, it is smaller than a turbine. Quick machines with rotating permanent magnets use to hold them in a tight sleeve of strong steel to counter the centrifugal force. I propose to wind a composite of graphite fibres around the magnets instead of the steel sleeve. Graphite fibres are lighter than steel and produce less eddy current losses where they cross the stator's windings; better, while the accurate diameter of a steel sleeve is difficult, fibres are commonly wound tight over varied cores, even with a pre-tension useful here. A unidirectional composite looks best here, and pre-impregnated graphite is usual at wound pressure tanks for instance - other fibres may emerge. Some thin elastic material below the magnets can prevent cracks. To run at 200m/s, 5mm thick magnets weighing 7500kg/m3 need 1.5mm of graphite composite withstanding 1000MPa - or scale both thicknesses. Neodymium magnets like Thyssen-Krupp's 300/110 still achieve 0.78T through the graphite plus 1.5mm radial gap. I already described a small electric motor turning a rocket engine pump, there http://www.scienceforums.net/topic/73571-rocket-engine-with-electric-pumps/#entry734225 and http://saposjoint.net/Forum/viewtopic.php?f=66&t=2272&start=80#p41298 the following one outputs 2083kW like the PW127M gas turbine that moves the ATR-72 and other successful planes. http://www.pwc.ca/en/engines/pw127m http://de.wikipedia.org/wiki/Pratt_%26_Whitney_Canada_PW100 http://en.wikipedia.org/wiki/ATR_72 The motor rotates at 255Hz, so a gear drives the propeller at 20Hz - but a turbofan would need none. 5mm thick magnets at D=250mm run at 200m/s. The 355mm long stator has 3 phases and 18 poles. The windings are one turn of square 5mm*5mm copper that makes 36 passes through the shared 54 slits. The induced coil voltage is 1726Vpk (reduce the length if I botched a cos30°...) and the current 804Apk, nice for an inverter supplied with 3kVdc maximum. Coil resistance is 13mohm (or a bit more as the skin depth is 1.4mm at 2292Hz) so ohmic losses are 13kW or 0.6%; core losses are small with the proper material. This electric motor weighs ~120kg, is ~400mm long and 312mm wide , while the PW127M is 660mm wide and ~1.2m long without the gear, and weighs 481kg with the gear. Direct retrofit, though we still lack proper fuel cells. Marc Schaefer, aka Enthalpy
  5. square root formulas

    I feel the comments are hard here. It's not every day that we read a new method to compute square roots. Maybe the proposal is not faster than the algorithms running presently in computer libraries, but it may have other benefits. At least, it opens news windows.
  6. Manufacturers don't speak about yields. When starting a process, yield is catastrophic, and 0% is normal - or rather, a new factory and process get tuned before any marketable product runs on the chain. But when production is near its maximum volume, yields are closer to 1 than to 30%. Several other factors influence the yield. The chip's size, because the same factory can make 3cm2 GPU and 0.3cm2 southbridges. Redundancy, where possible, with highly uniform chips having 1 or 2 units more than the minimum guaranteed to the customer. Sometimes defective chips are sold as good chips of an other series, typically for GPU: the MegaSuper XXX has 20 zlimmers while the Super XX has 18. The company tries to make all 20 work, but if 1 or 2 zlimmers are defective, they sell the chip with 2 zlimmers turned off. And when the market wants more Super XX, the company turns good zlimmers off. Then come smart customers who unlock the zlimmers and have a MegaSuper XXX at the Super XX's price. This operation works more often than not, telling that yields are near to 1, not to 30%.
  7. Question regarding resistance

    Hi Rasmus, welcome here! AC and DC work the same here, at small frequencies. Since R varies like L/S, both L and S are equally important. Coils are usually compared at identical volume, that is, proper design stuffs as much copper as possible in the available room, and the copper volume is L*S not forgetting a fill factor. This means also that the designer can adapt a coil to the load voltage and current. For a given magnetic circuit hence available room and shape of the coil, the coil L varies as the number of turns N and the wire section S inversely, so the resistance changes like L2. The produced voltage varies like N and the current at identical power like 1/N, so the lost RI2 does not depend on N. You can design the magnetic circuit for a fictive coil with 1 turn, and later adapt N to the load. In your project, you supposed that the coil resistance is the only limit to the output power, but generators have other limits. Especially, the current in the coil creates a magnetic field that reduces (but doesn't directly subtract, it's more complicated) from the inductor, maybe a permanent magnet. This effect can be more or less important than the resistance losses. With more turns, the same output current creates more of the unwanted magnetic field, so at some point more turns reduce the output current.
  8. Quick Electric Machines

    Thanks for your interest! There are a few biasses in my comparison. Tugplanes used presently were designed >50 years ago while I compare with a more up-to-date design and modern materials. They are too big: most accommodate 4 people while only the pilot is needed there to tow a glider. They are too fast: meant for >200km/h or more while towing is done at 110km/h. So my comparison is unfair in that the reference is unfit for the job. Or said differently, I compare with the existing stuff, not with what a new, specialized combustion engine tugplane could achieve. Other comparison elements are more fair. Conversion from electricity to shaft power is >95% efficient, but from fuel it's rather 40% (or less with the old engines), giving an other 2.5* advantage to batteries, over the 2* you mentioned. Then, piston engines that power the existing tugplanes use aviation gasoline, not jet fuel. With high octane rating, low water, formulated with lead for old engines, Avgas 100LL costs typically 2.5€/L here in ol' Europe, ouch. The tugplane's descent contains almost 1/2 the energy put in the ascent, so maybe 1/3 or 1/4 can be gotten back to the battery. A turbine sized for small aircraft would use cheap jet fuel, but presently small turbines are rare and demand a special license. A Diesel engine could burn jet fuel and be less inefficient than the present Volkswagen and Lycoming that are 0.5 century old designs - several aviation Diesel were under development 25 years ago. Maintenance is costly with a piston engine and nearly unnecessary for an electric motor. The battery must be kept under surveillance, but electronics does it for free. Fill less the tank: in my estimate, I wanted a battery 5* bigger than the minimum, because the pilot wants the capability to wait in the air or join an other airfield if something goes wrong. That would be the same with a fuel. So while I didn't check how good a new design with a combustion engine would be, the usual comparison is that electricity (at the present taxes...) is easily 3* cheaper than gasoline for the same flight and design epoch. ---------- Battery cost: I had feared a replacement every season, due to the very frequent charges and discharges. The estimated 10 years lifespan that result from shallow discharge are a relief to me. ---------- Silent propeller: this is a recommendation, not a consequence from the electric motor. I should have made it clearer. Once the motor is silent, most noise comes from the propeller, which shall bear the emphasis. The first standard means for that is a more solid propeller, with more blades, wider. This goes in the good direction for regenerative braking. The other means is to bend the blade tips backwards.
  9. Ocarina, Xun, Hun

    You can hear the Chinese Xun, the globular flute without fipple, on youtube: 96u1Ye1csB8 nX1q-E4tuF4 (music at 1:03) eNzGLAGLLuE The Corean Hun is rare there LFb7IXblgzM and I found no Japanese Tsuchibue (did I latin-spell properly?), only an ocarina mistaken for a Tsuchibue. You can hear that the wedge without fipple enables stronger low notes and softer high ones, like on the flute. I had to find the word "fipple" on Wiki... Not only in English! The sound varies among flutes, but we recognize the family, sure.
  10. "Bending" X-rays

    The index of most materials increases with the energy of visible photons, but above some threshold that X-rays vastly exceed, photons ionize matter and other laws apply. Refraction needs electrons to be little disturbed by light, but X-rays use to ionize. So "means similar to visible light" is bold. Check the XMM satellite for instance, and what kind of unreasonable "optics" it needed to make X-rays pictures.
  11. Induced emf in airplane wings

    1. Uniform over the span 2a. Yes, but the capacitance is tiny. 2b. Several T and 100m/s and 20m make only several 2kV, a little bit short for discharges in air. Around sharp edges and at altitude yes, some corona effect. 2c. No clouds needed. Yes, a complete circuit IF the current can pass from one wing tip to the other through something like air that doesn't move with the plane. Electricity generators work like that, often with refinements in the shape and materials. 3a. No danger within a conducting aeroplane. 3b. The passengers experience the same field and induction as the aeroplanes because the speed is the same. No potential difference, no risk. 3c. Disintegrate: I don't understand.
  12. Krokodil railway engine

    Hello you all! The "Krokodil" Ce 6/8II is arguably the most beautiful electric railway engine ever built, beauty and beast in one https://de.wikipedia.org/wiki/SBB_Ce_6/8_II despite the first delivery was in 1919, the design, with prow and stern traction sections connected directly, plus a driver cabin resting on both, still makes sense today for >6 axles, to pass sharp bends and spread the weight evenly on the track. So here's a modernized look for 8 axles, it could be 12 too: Marc Schaefer, aka Enthalpy
  13. Quick Electric Machines

    A battery-powered aeroplane can tow airgliders. Towing is the major cost of a glider flight, as the aircraft used presently are too big, designed for a higher speed, and consume lots of expensive special gasoline. Batteries power the very short flight easily and use cheap electricity. The market isn't huge, but an electric tugplane is simple to design and build, its use saves much money, so it could be a first commercial success for electric planes. The typical flight profile is to manoeuvre on the runway, wait for operations on the cable and the glider, take off, climb in <5min to ~800m, release the glider, plunge to the airfield and land. Some Li batteries are designed for quick charge and discharge; I take data from Saft's VL25PFe, safer thanks to Li-phosphate and efficient enough here: 28Ah, 0.94kg, 360kJ/kg, 1700W/kg (yes, 200s). They show the feasibility but are not an optimized choice, nor did I check the availability and price. 300kg batteries provide 108MJ and up to 510kW. Electronics, a geared motor and the propeller convert just 120kWe (163HP) to 90kW traction. Neighbours would appreciate a silent propeller. Several features shall avoid messing with the towing cable. The bigger wing at the rear shall counter vertical forces by the glider better. An additional rudder can fit at the bottom. The design has a fixed landing gear and no landing flaps for safety and cost. 35m/s operation and 25m/s stalling permit the 44kg/m2. The D>1.9m propeller pulls 2.6kN at 35m/s frame speed. 350kg frame, 300kg battery and 100kg pilot total 750kg tugplane flight mass. Climbing at 5m/s with a 600kg glider takes 1.9kN, moving the L/D>35 glider 0.2kN more, leaving 0.5kN to move the tugplane, for which L/D>15 suffices - the aspect suggests L/D>25. 30s equivalent full-power of ground operations and take-off, then 160s climbing, use 23MJ or 21% discharge depth at 4*C pace, sparing the batteries meant for 17*C. They should last >15 000 cycles or about 10 years; that cost remains to check. Electricity costs only 2€ per cycle. Regenerative braking by the propeller would be useful. A 100kW cable must be brought to the runway. 85MJe left after towing can still fly the tugplane for 130km and 1h at L/D=15, or rather 220km and 1.7h at L/D=25. That's important for safety, and to convey the tugplane, and for secondary uses. Marc Schaefer, aka Enthalpy
  14. Woodwind Materials

    The rare alto and tenor tárogatók have a curved metal bocal that fits in a mouthpiece with wider end bore like the saxophones do, instead of fitting outside a mouthpiece with narrower end like the clarinets do. As opposed to the soprano tárogató that uses clarinet (-like) mouthpiece and reed, they must even use bocals, mouthpieces and reeds from alto and tenor saxophones, leaving even a chamber in the mouthpiece. One tenor can be seen and heard there: pn6X4vvbbz8 on youtube at 12min Logically, the alto and tenor don't sound like the soprano tárogató, but very much like saxophones, hence are little useful. Already Stowasser used saxophone-like alto and tenor bocals: I suggest instead that the alto and tenor tárogatók receive bocals that fit on the mouthpieces of alto and bass clarinets, and use corresponding reeds, to achieve the distinctive sound. ========== All low wooden clarinets and tárogatók, beginning with the altos, have their curved parts made of metal. Though, a wooden bell is claimed to give the bass clarinet a "more powerful and centred sound": wMbK_zhcmOk on youtube at 2min16 so graphite composite may improve the bells and bocals of clarinets and tárogatók. While injection needs a costly mould, filament winding companies would easily produce a bocal shape. A U-turn and a bell may need several parts. I suppose a low-melting alloy can make the mandrel, cast for each part and molten away. Paraffin loaded with talc makes great mandrels for glass web, but may be too weak for graphite winding. Graphite fibres don't, so the matrix must dampen the vibrations. Epoxy doesn't. Whether ABS, PP or polyketone can impregnate the filament? Marc Schaefer, aka Enthalpy
  15. Woodwind Materials

    Hello everybody! The material used for the walls of woodwind instruments, and its real, perceived, imagined or absent influence on the sound and ease of playing, has been and is the controversial matter of recurrent discussions that I gladly reopen here. The air column is the essential vibrating element of a wind instrument, the walls are not, but this is only a first analysis. The walls are commonly made of wood (sometimes cane, bamboo etc.), metal, or polymer aka plastic, which manufacturers call "resin" to look less cheap. Mixes exist too, with short reinforcement fibres or wood dust filling a thermoplastic or thermosetting resin ("Resotone" for instance). I'm confident that long graphite fibres were tried too, as fabric, mat or in filament winding. The choice results from marketing, tradition, weight and manufacturing possibilities (a tenor saxophone is too big for grenadilla parts), cost - and perhaps even acoustic qualities. ========== Plastic is a direct competitor for wood, as the possible wall thickness, manufacturing process, density, stiffness, shape possibilities, are similar. As opposed, the density of metal restricts it to thin walls made by sheet forming an assembling, but permits big parts. Manufacturers typically use plastic for cheaper instruments and grenadilla for high-end ones - some propose cheaper wood in between, possibly with an inner lining of polymer. Musicians who own a grenadilla instrument disconsider the plastic ones; I never had the opportunity to compare wood and plastic instruments otherwise identical, so I can't tell if the materials make a difference, or if grenadilla instruments are more carefully manufactured and hand-tuned, or if it's all marketing. Two polymers are commonly used: polypropylene for bassoons, and ABS for all others, including piccolos, flutes, clarinets, oboes. These are among the cheapest polymers, but 10€/kg more would make no difference. They absorb very little humidity, but some others too. More surprising, they are uncomfortable to machine: POM for instance would save much machining cost and (my gut feeling) easily pay for the more expensive material. But ABS and also PP absorb vibrations while others don't, which I believe is the basic reason for this choice. They limit the unwanted vibrations of the walls. As a polymer that dampens wall vibrations, I should like to suggest polyketone https://en.wikipedia.org/wiki/Polyketone it's known to make gears more silent than POM and PA, its glass transition is near ambient temperature, its density and Young modulus resemble ABS, it absorbs little humidity. Still not widely used, it can become very cheap. Its creep behaviour and ease of manufacturing are unknown to me, but ABS and PP aren't brilliant neither. Marc Schaefer, aka Enthalpy
  16. Sound Perception

    Again researching why the highest piano notes would be perceived too low while nobody complains about the glockenspiel and celesta pitched even higher, I synthesized notes at the piano's highest C and the F below, this time with attacks slow to snappy. The program is again my TingPoc.cpp and exe. TingBingMake.txt feeds TingPoc.exe to create a wav renamed TingBing.wav TingBing.zip My ears perceive the same height for 50ms, 20ms, 10ms, 5ms, 2ms rise times. Neither an explanation for the piano's high notes. And I hear again a good fifth here. Marc Schaefer, aka Enthalpy ========== Still researching why the highest piano notes would be perceived too low, I synthesized notes at the piano's highest C and the F below, with varied decay times as on Nov 25, 2018 but beginning now with the shorter ones. The program is again my TingPoc. PingBMake.txt feeds TingPoc.exe to create a wav renamed PingB.wav PingB.zip When I'm not influenced first by the longer ones, my ears perceive lower and less precisely the shorter notes. Here the exponential decay time is 5ms, 10ms, 20ms, 50ms, 100ms. I hear inaccurately the 5ms and 10ms, and 20ms isn't good. This isn't so surprising. 20ms of 4186Hz sound contain 84 periods, which is little to discern semitones 5.9% apart, and we claim to hear height far better than a semitone. While the glockenspiel and celesta sound longer and nobody complains about their pitch, the piano's highest C may last around 20ms, and this can contribute to the imprecise and too low perception. Marc Schaefer, aka Enthalpy
  17. Sound Perception

    Hello everybody and everyone! I'd like to share some thoughts about sound perception here. ========== First, does the phase of the harmonics matter in a periodic sound? This was a debated question when Hi-Fi was fashionable, and is still interesting. Here's a piece of software I made for more general purposes. It creates a file Tut.wav playable by Winamp, Windows' Sndrec32.exe, Media Player and probably more. The user defines a spectrum (hence of a periodic sound), the soft writes the sound in the file. TutD.zip I recommend to listen with headphones rather than PC loudspeakers that create misleading distortion even at low level. And this is a 440Hz sound with H1, H2 and H3 of equal amplitude, where the phase of H2 or H3 vary between two seconds intervals: 0s 2s 4s 6s 8s 10s 12s 14s 16s =========================================================== H1 (0dB) | 0° 0° 0° 0° 0° 0° 0° 0° H2 (0dB) | 0° 45° 90° 135° 180° 180° 180° 180° H3 (0dB) | 0° 0° 0° 0° 0° 0° 180° 45° =========================================================== H123Phase.zip And the net result is: I hear no difference at all. The phase of the harmonics does not matter. Marc Schaefer, aka Enthalpy
  18. Woodwind Fingerings

    Here's a system D contrabasson, bent at the bell to be less tall. What would be the boot at a bassoon is folded to the front for compactness. Disassembled, it fits in a manageable case. The right and left tubes could very well be swapped so the left fingers' tips reach between the tubes to make simpler keys. Only the two low B and Bb keys cross an assembly line, plus the hypothetic register keys at the bocal. All tone hole covers can be at wooden parts, and the bell and U-turns are passive. Some strict woodwind manufactures should find it easier. But the bell, turn and two nearby cylinders can be one metal joint. The metal walls could be electroformed as already suggested Jan 01, 2018 and May 02, 2017 and nearby while graphite composite might perhaps replace wood too if the polymer matrix dampens enough (polyketone? Abs?) Nov 01, 2017 and followers Whiskers-loaded polymers can be machined similarly to wood while filament winding can make bent shapes Nov 01, 2017 Marc Schaefer, aka Enthalpy
  19. Woodwind Fingerings

    Hello dear musicians, music lovers and everyone! I'd like to describe fingerings for music instruments with tone holes (which almost means woodwinds) and the associated mechanics. My goals for these fingerings are: Open all holes below the height-defining one, at least on the two first registers; Have no difficult key nor sequence of notes; Not need to close a hole and open an other simultaneously, at least on the two first registers. That's a difficulty of the flute; Need few tone holes regularly spaced and reasonable mechanics; But I don't primarily address the ease or possibility to disassemble the instrument. 1) and 4) make the sound quality more even and let build an instrument with better intonation. To achieve that, my very own personal proposal (... other people have proposed so many!) is: Give one half-tone to the index, middle finger and ring finger of each hand, to cover the upper part of all registers; Continue lower by approximately 4 half-tones with the little fingers. Each has the full set of keys like on the Boehm clarinet; Continue even lower by approximately 5 half-tones with the thumbs. Each has the full set of keys too; Trills near a register limit are made by the little fingers or thumbs, so the registers must overlap. No extra tone hole. Have register keys at the thumbs. Preferably, each thumb has the full set of register keys. The third register and above can't be common to all instruments: an additional register key suffices for some, others need cross fingerings, still others have extra tone holes. One finger for each of the highest six holes make cross fingerings more flexible. Expect differences among the instruments at the two first registers too. The thumbs, being agile in two directions, are the best fingers to operate several keys - bassoon players can confirm. The full set of keys at right and left little fingers is very convenient on the Boehm clarinet, where musicians alternate the notes among the hands. I propose to generalize it to the thumbs, both for lower notes and register keys. Drawings to come should make it clearer. They take me a little time. Marc Schaefer, aka Enthalpy
  20. Sound Perception

    In a renewed attempt to explain why the highest piano notes would be perceived too low, I synthesized notes shorter and shorter, at the piano's highest C and the F below. The program is my TingPoc that already served there https://www.scienceforums.net/topic/111316-woodwind-materials/?do=findComment&comment=1078729 PingMake.txt feeds TingPoc.exe to create Ping.wav Ping.zip My ears perceive the same height for 200ms, 100ms, 50ms, 20ms, 10ms decrement times. Not an explanation for the piano's high notes. By the way, I hear a good fifth here. Marc Schaefer, aka Enthalpy
  21. Woodwind Fingerings

    This shows flutes with four systems, three already described and one coming here, retroactively named A B C D: The differences reside high at the main joint. ========== The D flute system has four tone holes above the left hand, without overlapping due to other trills and octave switch, and moved by both thumbs. True tone holes high at the main joint shall emit altissimo notes easily, 3 or 4 fork holes too. Though, the additional big holes may increase the losses at other registers. Maybe the bore can be slightly wider for balanced improvement everywhere. I've drawn the added tone holes aligned, consistently with a rumour about losses, but the keys would be simpler if at the tube's side. I ignore which system is better. At least, they're very similar, so trying them is a smaller effort. Marc Schaefer, aka Enthalpy
  22. Alloys to store hydrogen?

    Hello everybody! You know hydrogen is thought as a way of storing energy, before transformation in a fuel cell for instance. Storing liquid hydrogen isn't very easy because it needs really cold temperatures, and pressurizing gaseous hydrogen needs heavy tanks with little capacity, so research is being done to adsorb hydrogen in a solid in the hope to store much hydrogen in a small volume under reasonable conditions. My own two-cents suggestion is to use abnormally light metallic alloys for this purpose. That is, alloys whose volume is bigger than the sum of the volumes of their constituents. My hope is, of course, that more free room is available to hydrogen in the alloy then. Alloys known for their abnormally low density (and modulus) include: - Bell bronze (20% Sn, 80% Cu) - Invar (36% Ni, 64% Fe) Also Mn-Cu (vibration damping alloy) has abnormally low modulus, but I haven't found its density. ---------- Both Ni-Fe and bell bronze alloy elements with slightly different molar volumes. Is this a key to abnormally low alloy density? On the other hand, Ni-Ti has in some metallurgical states a very low Young's modulus but still an abnormally high density, so Young's modulus isn't a reliable indicator. ---------- Shape memory alloys (like Ni-Ti) change their volume over temperature. Provided they store an interesting amount of hydrogen, the density change could be a means to release the gas at will. ---------- Well, I guess competitors like zeolite are already better than any metallic alloy, but anyway, that was my message in a bottle. Marc Schaefer, aka Enthalpy
  23. Alloys to store hydrogen?

    I've seen figures like 15kJ/mol for adsorption heats. Measures from serious storage candidates would be better. That's 1/20th the combustion heat. So if the engine uses the hydrogen in 3h to produce 60kW with 50% efficient cells, and the user tanks in 6min, 3*60kW=180kW must be evacuated. So what's the trouble? We have hydrogen in the tank, an excellent fluid for that task. Once the heat is at the tank's walls, blowing some air removes it. It's as much heat as from a 240HP thermal engine, except that this heat is already at the atmosphere. I won't put my time in this. Banal engineering.
  24. Hello everyone! The Argentine submarine ARA San Juan last reported on November 15. On November 23, the Navy published that two hydrophone stations operated by the CTCBO, meant to detect nuclear explosions, heard a non-nuclear explosion near the possible position of the submarine, suggesting a total loss of the ship. My information isn't at the source, alas - data from Twitter, and so on. Signals, positions of the hydrophones, timescales https://twitter.com/SinaZerbo/status/933745155399708674/photo/1 do you understand too that the three blue-to-red histograms are strongly amplified, hence the scale does not apply? I suppose the blue histogram maybe fits the scale in dB ref µPa2/Hz, the others not. How do you understand the several replicas after 90s? I can only image an artefact from signal processing. An echo would need a reflector >70km away, and then the echo couldn't have an amplitude similar to the first sound. Do you know if the hydrophones on Tristan da Cunha were active? And if yes, why didn't they pick the noise? They were nearer than the ones at Ascension and Crozet that picked it https://www.ctbto.org/verification-regime/featured-stations/types/hydroacoustic/ha09-tristan-da-cunhaunited-kingdom/ https://www.ctbto.org/verification-regime/featured-stations/types/hydroacoustic/ha09-tristan-da-cunhaunited-kingdom/page-1-ha09/ https://pbs.twimg.com/media/DPVIXa_W4AEyAcF.jpg and from the sensitivity map (look at the shadows by the islands), those on Tristan da Cunha seem as efficient as the others, to the West too https://twitter.com/ferencdv/status/933737271748050944 they were put into service before 2010. And if the hydrophones' sensitivity at the inferred loss location wasn't worse than 1t TNT or 4.2GJ (see map), it corresponds to 7MPa (700m depth to crush the hull) times 600m3, or 1/6th the vessel's volume (D=8.2m L=65m), so at least this would be consistent. It's consistent with other potential sources too. Thank you!
  25. Disappeared Argentine Submarine

    The control loop includes the crew, which has several means to act on the depth of a submarine. Ballasts are one means. The flaps are an other if the boat moves. At least some submarines have weights than can be dropped if everything else fails. But (all?) these need power on board and some valid crew members. A valid explanation must tell why none of the control means brought the submarine to the surface.