Enthalpy

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  1. A governmental health agency published a report on 19 July, including on page 30 a map made by the police of the lead deposits www.iledefrance.ars.sante.fr (20MB) it's frightening. The units are really µg/m2 and up to 1.3g/m2 lead deposited. I didn't find in the report when the measurements were made. I believe it was in July, after several rains had cleaned the surfaces. The figures tell how much lead gets dissolved by HCl under conditions that simulate the digestion, which I believe is a small fraction of PbO. Though, at least Wiki tells "Inhalation is a major source" fr.wikipedia so the poisoning of people present during the fire may be much worse. Multiplying the area by the surface density, I get only 1kg deposited right around the cathedral and 2kg on two districts downwind. Though, intuition shouts that the big dense yellow smoke that escaped for hours contained much more PbO. The figures don't add up. Probably most lead oxide deposited farther downstream: excess lead was observed in the air outside Paris. And most lead went to the sewage before the measurements. To illustrate 1g/m2, I weighed dust after cleaning a room: 1.9g over 30m2 is yuk, and this isn't poison. At the cathedral, they got nearly that amount on 1m2. Pictures appended. How unhealthy? Imagine that away from Notre-Dame, at Saint-Michel square that kept open and uncleaned, someone wanting to make photos lays his 0.02m2 croque-monsieur on the foutain's rim, then eats it. 30mg/m2 were measured (but when?), so he ingests 600µg of digestible lead equivalent. If he's an adult with 6L blood, his concentration climbs to 10 µg/dl, the upper limit set by the Center for Disease Control. On the cathedral's square, concentrations were 20* higher. The concentration may have been much higher right after the fire, and poisoning over the lungs worse.
  2. People whose native language is tonal (sung, if you wish) have better chances of having absolute pitch (perceive the height of a single note, not just intervals), according to one researcher https://en.wikipedia.org/wiki/Absolute_pitch#Linguistics
  3. Here's a different look for a modernized oboe da caccia, not with a curved body, but with angles. Easier to draw and to produce, but the much stiffer body may not give the clear soft sound of Eichentopf's design. At least it looks archaic too. I've carefully forgotten to display the thumb keys and the transmissions to the low joint, so the instruments seems simple. At least the front aspect is spare like a historical piece. Hand rests are needed but not displayed. Both hands at one joint simplify the thumb keys. I've shortened the main joint above the highest tone hole and lengthened the bocal whose shape tunes the ergonomy, but then the register keys are at the bocal. Other options are possible, even a second angle and a wooden joint that carries all register keys and runs directly to the reed. Baroque luthiers had no Dalbergia, so this instrument can use less good wood that passes borders, and clearer to look baroque, maybe Buxus sempervirens if not too toxic. Soft thin walls would help imitate Eichentopf's sound. Marc Schaefer, aka Enthalpy
  4. Thanks for your interest! Yes, I like jazz, though I started the alto sax for classical music, after hearing it at the pictures at an exhibition. I have a record of Take five with Gerry Mulligan at the baritone, very nice sound. Any woodwind is easier than the flute, and by much. The sax has easy fingerings but has less known shortcomings. Very high in demand are the oboe (needs only a huge pressure and extra-strong lips), the bassoon (rather easy, especially as compared with the flute), the bass clarinet (works very well, easier than the soprano, have your own and orchestras seek you already).
  5. Thoughts about a modernized oboe da caccia with my even oboe fingerings. The range competes with the cor anglais. The very distinctive sound makes the oboe da caccia useful, to be kept. If it results from huge losses at the body, as I believe, these must be kept or reproduced otherwise. I wish a low Bb despite old scores write to C. Some orchestras play a semitone lower the baroque scores. Playing the same scores on all saxophones is also very convenient, so the oboe family should copy it. A body straight at the five lowest tone holes eases my even oboe fingerings. All known historical shapes were straight at the lower end. A low joint could be assembled there. Only five tones holes plus the five lowest ones need covers Sep 16, 2018 - Jul 30, 2017 - Aug 17, 2019 05:02pm One construction known from paintings had an angle in the air column between the hands and optionally a second one lower. Maybe the sound was completely different, but we ignore it as no instrument has survived. This shape would ease my thumb keys. The other construction is gently curved over both hands and documented. The angled contruction can just have bowls of polymer, or maybe <i>Buxus sempervirens</i>, where both joints converge with corks. A tone hole there looks possible. Assembling there is easy and shrinks the transport case. Transmitting the thumb keys is reasonable. A curved body is less easy. Filament winding is easiest for a thin long body curved by some 90°. There and around: Dec 16, 2018 - Mar 30, 2019 02:34 PM Electroforming seems reasonable. There and around: Jan 01, 2018 - Sep 29, 2018 2:24 pm Or apply the traditional method and the variants I suggested Aug 16, 2019 04:16 PM Maybe the soft sound needs the exotic construction. Or it's unrelated. Or other means can achieve the losses. The museum pieces or the replicas must tell the tone holes' diameters, to be kept narrow and adapted to my even system - that's a good part of the sound. Chambers can be added at the tone holes for softer sound, tuned lower than usual, and dummy tone holes never opened can introduce more chambers to dampen a wider spectrum. Jan 28, 2018 The bore can be kept as is. On the records of the copies, the sound gets harder on low notes. I prefer to suppress the wide flare, keep a nearly straight bell, and add many small holes as Stowasser did on the tárogató. Visual examples: Jul 30, 2017 - Sep 16, 2018 Marc Schaefer, aka Enthalpy
  6. Among my proposals for the oboe and similar, the D even fingering variant takes the fewest and simplest keys. How many bare holes can it use? None at the five thumb holes. Not at the second index hole that should be placed properly a semitone higher than the first. Supposedly not at the pinkies as they are short. 6 holes remain. They can all be bare at the oboe and oboe d'amore, for agile, silent, reliable, light and cheap instruments. At the oboe da caccia and cor anglais, the left hand holes can be bare, plus two at right hand: same R1 to R2 spacing as on the bassoon, comfortable but for children. The baritone oboe can have two bare holes at left hand. The real distances will be slightly smaller. The table takes half-wavelengths in air, but small tone holes are higher on the air column. I would not have long skewed tone holes as the bassoon has. They behave differently at the upper register, but the cross-fingerings there should fit a whole instrument family. Chambers eccentric above the tone hole narrow bore can gain a few mm. Marc Schaefer, aka Enthalpy
  7. Following the message of Jan 15, 2018, here''s one more comparison between grenadilla and Pmma oboes, both from Marigaux and played by the same musician, in the same bad room full of echo: rBEysvPiYPY at 0:34 and 1:38 and I hear exactly the same difference as with the other oboist: Pmma sounds like a piece of plastic, especially at the low notes. Simply the wrong material for a woodwind. It's even surprising that the difference is so strong and repeatable. Possibly the oboe depends more on the walls materials than other woodwinds.
  8. According to Cary Karp, who studied two remaining oboe da caccia made by Eichentopf jstor.org - wikipedia the body was first machined straight, then (gashes) kerfs were sawed at the rear side, the remaining wood bent over steam, a slat glued at the rear, and voids filled. Playing copies were made in recent times the luthiers know the missing process steps. My tiny contribution: let make a cutter to mill the gashes accurately. It can have precisely the needed shape, except for the rim that needs a minimum width. The conical shape demands cutting edges as far from the rim as the gashes are deep, and the cutter's radius can exceed this much. Several cutters on a shaft can work more quickly. ========== I've already suggested to cut wedged body segments completely from an other and glue them together as a curve scienceforums and here's an illustration: Slats can usefully hold the segments precisely in place while glueing, especially if they press against accurate flat surfaces made at the body before segmenting. ========== Both processes apply to polymers too, including polyketones and liquid crystal polymers, except that heat rather than steam softens them. I had already suggested electrodeposition Jan 01, 2018 - May 02, 2018 and filament winding Nov 01, 2017 to produce curved body parts. The two present processes need a different know-how, possibly more accessible to pure woodwind luthiers. Good glue joint aren't easy on polymers. Glueing POM is known. Solvents can prepare a surface for glueing or make the joint Few solvents are known for polyketones: hexafluoroisopropanol, meta-cresol, and the more benign solutions of ZnCl2, ZnBr2, ZnI2, LiBr, LiI, LiSCN that leave residues. Solvents for liquid crystal polymers are uneasy too: pentafluorophenol, trifluoroacetic acid. Though, slats alone won't bring much stiffness not toughness. Welding polymers is better than glueing them when possible. Many woodwinds need or would benefit from curved body parts of wood or polymer: alto and lower clarinets, bassoon and contrabassoon, baritone oboe, alto and lower tárogatók. Marc Schaefer, aka Enthalpy
  9. If someone makes an aluminium matrix composite with 12ppm/K instead of presently 15.5pm/K for 25vol% of SiC, that will make excellent frames for many-strings music instruments like cimbaloms scienceforums E=115GPa for ρ≈2900kg/m3 would give instruments more stable tuning for less weight than cast iron does for the piano. I imagine that more ceramic in the composite reduces its thermal expansion and further increases its stiffness. Mix different particle sizes as suggested previously. Of course, the composite must be cheap to produce and process, supposedly by casting. Flexural strength is interesting, but the stress isn't huge since stiffness decides the sections, and already the use in pure compression would be interesting.
  10. Hello nice people! Metal Matrix Composites (MMC) mix ceramic powder, nanotubes, other small things with a matrix of metal like magnesium, aluminium, titanium, iron alloys. The goal is to increase the stiffness, the compression resistance, have a small density, and hopefully keep a decent tensile resistance and toughness. I haven't searched for long, but apparently they use a single range of particle size, to about 40% volume filing factor. Though, a suspension becomes quickly a slurry, and with about 40% volume of solid particles, it doesn't flow any more. I understand that particles touch an other as their arrangement isn't optimum, so they immobilize the suspension, and more particles create cracks. A solution is already know and may apply to MMC. Concrete uses three very different ranges of particle sizes: pebbles, then grit to fill the voids between the pebbles, then sand to fill the voids between the pieces of grit. In this way, the liquid fraction is much smaller when concrete is mixed, and it still flows. It is my hope that, by using several very different particle size ranges in MMC, a higher volume fraction can be used, and as the metal is still contiguous, the MMC retains a decent tensile resistance and toughness. Marc Schaefer, aka Enthalpy
  11. I developed one such machine, but it was a quarter century ago, so they can have evolved in a completely different direction meanwhile. This automatic cashier could read a barcode, let the customer pay with a bank card, and deactivate the anti-theft stripe, optionally reactivate it. The anti-theft stripe is covered with permanent magnets which, after they're made, deactivate the stripe by saturating it, so the detectors at the store's exit don't notice the stripe. The magnets are chosen weak, but it still takes a good magnetic field to make them, and at some distance through the air. This demands a strong current in the deactivating coils, which I obtained over a short time by capacitor discharge. The combination of significant field, strong current and short time creates a mechanical shock that is noisy. It could be reduced by making the coils stiffer and suspending them separately from all surfaces. I didn't care at that time, possibly nobody did meanwhile. In a different experiment, I had 350V and 20kA in several turns that created 7T, and this one was much more noisy. Even the feed cables had to be hold on the table or they would jump away from the other. The friend how did that regularly told me that once a connection screw wasn't tied, it just vaporized when the current passed, and he stays deaf for a day.
  12. All piano soundboards I've seen have the plate's fibres in one direction and bracings in the cross direction, where the plate alone would be too flexible. The spreadsheet HackbrettBracings.xls from July 28, 2019 in this thread claims that a thinner plate, and bracings in both directions, would be much lighter at identical resonant frequencies. The instrument would then be louder. This needs tall narrow ribs that keep stiff where they cross, not trivial. Cimbalom Vsiansky do it, with shallow wide ribs cimbaly.cz and some guitar luthiers too. Maybe one direction can be above the plate and the other below. This should combine with the use of kiri, Paulownia tomentosa. Unless the balsa sandwich of August 03, 2019 03:45 PM is better. It's not the lightest, and I doubt about its damping, but it looks easier to build. Marc Schaefer, aka Enthalpy
  13. The OP wrote "strength", not stiffness, and strength doesn't depend on parts length if extended or compressed. One first element of answer is then to make parts longer. A truss construction that loads the elements only axially is better. Bending for instance is much worse, as it amplifies the stresses a lot but doesn't isolate, so the bigger cross-areas conduct more heat. Though, everything depends completely on individual cases, especially the concentration of the forces. How much conduction is accepted is quite important too. "Maximize this and minimize that" is a counter-productive information in engineering that often leads to uselessly complicated designs. And whether the solution uses titanium, stainless steel, aramide belts, glued spruce, a truss of thin electrodeposited nickel tubes, plastic foam or cork depends on the needs. Obviously the shape won't be the same then. Whether air convection is acceptable matters a lot too. So Engineer43, could you at least tell the forces, the accepted heat transfer, the warm and cold temperatures, the dimensions, mass...? Or far better, describe your project. For a satellite, we afford designs and production methods inadequate for a fridge.
  14. Positioning the big tube higher at the metal frame suggested for cimbaloms, Hackbrett and similar is advantageous. Both tubes experience a force less amplified, and their deformations act less amplified on the strings. At least the distal tube can be level with the mean string height. Then the small tube feels no force and contributes no string deformation - it can be lighter, maybe suppressed. As compared with tubes 30mm and 180mm below the strings, the big tube's elasticity acts (5/6)2* as much on the strings, so it detunes by 0.7 semitone instead of 1.0, or it can be lighter, and the small tube doesn't add 0.1 semitone. How high can the proximal big tube be, ideally level? Alas, I don't play these instruments. The mallets strike the strings head down, but I ignore by how much. The strings are also higher than the average where striked. So a D=48.26mm tube doesn't have to be 30mm below the strings.
  15. I described on July 23, 2019 a metal frame running outside the soundbox for a Hackbrett: before, behind, and at the sides above the box. Here's an attempt for the grand cimbalom with sixth tuning as on June 16, 2019. The instrument is heavier and less stiff than with metal beams through the box as on July 08, 2019, but it's easier to assemble. Octave tuning as on July 17, 2019 with added bass strings would further complicate the present attempt. July 23, 2019 - June 16, 2019 - July 08, 2019 - July 17, 2019 on scienceforums The bridges and saddles could spread less at the bass strings for an instrument smaller and maybe easier to play. Here as previously, the bass strings drop to 0.54*C, the others vary smoothly between 1.10*C and 1.16*C. I take round 60kN total string tension. The pinblocks are skewed by cos=0.783 so F=21kN pull perpendicularly to each X=0.4m half-pinblock. 1.1*C stretch the strings by 0.54% so a semitone detuning is 320ppm, or for middle strings 169µm per side, 244µm perpendicularly to the pinblocks. Using 22-05 duplex everywhere, E=200GPa G=76GPa rho=7820kg/m3, so tubes of D=48,26 e=5,08 and D=17,20 e=2,30 at 30mm and 180mm below the mean string plane feel 36kN and 6kN and deform by 261ppm and 279ppm, cumulating 360ppm = 1.1 semitone at the strings. They buckle at safe 111kN and weigh 15kg together. The e=15mm W=180mm pinblocks can be narrower at the ends. Holes leave metal at the outer 34mm; round holes aren't best. EI=1,1MN*m2 in 5FX3/(24EI) bend by 253µm = 1.0 semitone at middle strings. 21kN spread on 0.4m shear by 54µm = 0.2 semitone at middle strings the pinblocks' 2*15mm*34mm. Twisting inertia is 0.24e3W for each 15mm*34mm part of the pinblocks as from Dubbel, together GJ=4.2kN*m2. If 21kn spread over 0.4m pull 5mm outside the middle plane, 5.0mrad let middle strings 15mm away from the plane stretch by 75µm = 0.3 semitone by torsion. At a narrow cantilever beam according to Dellus, here EI=4.8kN*m2 at the thin direction, buckling would occur for 4.1*(EI*GJ)0.5/L2 = 115kN, a first hint for the present case. Cumulated 2.6 semitone at the centre strings (but 1.1 at the extreme) mean 4 tuning passes after restringing and 1 pass to shift by 0.2 semitone the whole instrument, not bad. Temperature and moisture shall have no effect. Two pinblocks cost 34kg material and weigh some 19kg. Width at the centre brings much stiffness, costs money but adds little mass. Casting seems interesting, including the struts optionally. Thicker edges at T shaped pinblocks would catch broken strings and improve the stiffness versus mass tradeoff. Marc Schaefer, aka Enthalpy