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Everything posted by Externet

  1. On the news, a monolith someone had fun placing in the desert, worth spending a couple of nostalgic minutes...
  2. Solar heat collector: I do not know what a 'halfpipe' is, but a whole pipe for sure works for well under $800 unless you go lenghty big diametres. Irrigation pipe is not expensive. Place under a clear plastic sheet/box/film so wind does not takes away the heat collected; or/and recirculate to a storage tank in basement. Maintenance is near null.
  3. Thank you. Found some reading on the photons subject. Believe there is no such thing as half a photon, right ? ----> https://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html#:~:text=Since only about 10% of,actually required at the receptors.
  4. The time for visual persistence is typically taken as 1/30th of a second; what is the minimal time a light should be on to recognize its brief presence ? Example, a high speed mechanical shutter wheel in front of a light source. (Or a pulse on LED) The light passes a slot to the eye for one millisecond. Probable visible. What if one microsecond ? Would that time be long enough to be detected by the eye ? Is there a name for that 'time sensitivity' ?
  5. Externet


    Hi. A just born millipede has less legs count and new ones are created with age, or at birth has the full count and legs grow larger with age ? 🙄
  6. Greetings. Do you know of a simpler simulator program on the web to find times a model submarine takes to sink to bottom of a reservoir; and time it takes to reach surface from bottom when its buoyancy is changed/controlled ? Thanks
  7. Greetings. When I walked on the Galapagos glasslike volcanic soil, nothing grows on it, perhaps saw a lost lizard. How many centuries takes for that soil to turn to the "great soil of volcanic origin" often described covered by lush jungle vegetation ? How does lava converts to fertile soil ?
  8. Hi all. Which is wrong ? 'Door' or all the others ? door is not pronounced as poor book wood root tooth cook boost doom roof good hood cool food loop mood boot soot school And 'here' and 'there' ; differ by the added 'T' with a substantial pronunciation difference, being actually more like 'der'. (another silent E.) 🤔
  9. Excellent, gentlemen, thanks. Now am more convinced English has really absurd rules. 😮 A silent ending 'e' changing the sound of a previous vowel. It shows there is no language regulating entity. 😮
  10. Words like like blue orange there voltage George tube range and hundreds more, to the point of boring overdose. With all the passion for shortening writing in english, why is the silent e not eliminated ?
  11. Hi all. This not numbered ball bearing tells by dimensions to be a '6201ZZ' type; but has a groove where a staple-shaped piece lodges-in. Set aside to show the groove where fits. Is there a nomenclature suffix for such feature that you may know ? It has only a faint "USA" marking, but it is metric, from the seventies as far as I can tell.
  12. Why the moderator does not have a fifty cent microphone-off switch for who is not supposed to talk that moment ?
  13. Hi all. Does anyone know this new crap about hose sizes ? Trying to find 1/8 inch or 3mm i.d. hoses; found this. Have these geniuses never heard of the millimetre ? What entity governs dimensions and terminology ? ----> https://ph.parker.com/us/en/hydraulic-constant-working-pressure-hose-5000-psi-globalcore-787-hose
  14. Thanks for your response; appears to be clear and accurate enough. Is this an on-line tool that I can access ?
  15. Hi. Am not good enough and less when as blurry as this... Can someone translate the pharagraps following "14" ? Is that for a motor? 🤔 It is an image and do not know how to get a translation from images Thank you.
  16. Google did changes to the search process and capability a while ago and cannot access some foreign things now. Trying to locate a russian brand/factory of electric bicycles from several years ago, to find if they are still in business or production. From USA, cannot see internal russian sites any more ¿? That manufacturer had also a video of the bicycle; and a full site for the product. Can someone capable of doing such search inside Russia post a link where I could see maaaany results to choose the correct one ?
  17. Thanks ! OK, checking...; one of the 230V conductors in a plain wall outlet is neutral and does not come from a power pole transformer centre tap. The other is earth ground and comes from the utility company street pole. The last is 'live - hot - phase' from the utility company and does not come from a utility pole transformer 😕 and it is the only and single 'phase' electric conductor supplied to a household. And each country in the european community does it the way they want.
  18. Hi. Does wiring in concrete, block, stone walls runs mandatory inside metallic conduit?; with several insulated single conductors or multiple bundled conductors ? Is 'Romex type' multiple conductor wire used there ? Is the 230V two 'live' wires from a centre-tapped utility transformer or is one of the conductors neutral ? Are neutral and earth ground joined somewhere ?
  19. Thanks. 25 litres per minute is the atmospheric air pressure inlet before compression. Like at start of every cycle; 25 atmospheric litres are fed above the oil surface, then compressed and delivered trough a non-return valve and 25 more litres are admitted for the next (1 minute) cycle. 25 l/min is not the flow at 6000psi.
  20. Thank you. 25 litres/minute. Am very aware of dangers for gases under high pressure. Lubrication in an air high pressure piston compressor I had took a very special synthetic oil MIL6085A to avoid it from combusting as diesel fuel when exposed to high pressures and destroying the compressor; and wondered how worse would the similar risk of vegetable oils be.
  21. Thanks, gentlemen. Do you see a convenient way to compress air with no toxic contaminants as from synthetic/mineral oils ? The intention is to explore using a hydraulic pump to compress air above oil surface. Is there such contraption in the market ? Using water could corrode the pump.
  22. Hello. How to find at which pressure, which edible oils ignite/decompose ? Where to look for such data ? Say plain soybean oil; will it withstand being pumped/compressed at 6000 psi / 400 atm ? And other edible oils...
  23. Any reflecting or shading treatment should only be done at the exterior; before sunlight hits the windows glass. That produces a considerable cooling !
  24. Good day to all. If a catastrophic failure in the forum server damages the records of years of posts; is there a backup of all contents ? Is it possible to purchase DVDs with the SFN contents; since day one; or by years; or by subforum contents ? Or what is suggested to obtain/download the history of a subforum content -say Applied chemistry- to save in optical media in a readable format , like we access it normally any day ? What about copyrights, use restrictions, ownership ?
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