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  1. Nik_2213

    Q regarding fixing old busted water line w/ no water in it for 2 yrs

    I suggest you get entire line inspected. If good, okay. If bad, better to resolve now rather than have hidden / future leak(s). Those may cause anything from wasted water (metered ?) via sewage ingress during storms to sink-hole formation...
  2. Nik_2213

    Fan-motor system resonance problem

    A thought: Those diagonal stiffeners ? Do they resonate ?? If so, can you add masses to 'quench' them ??
  3. Nik_2213

    Connecting Shafts of 2 Very Different Diameters

    If low torque, classic trick is to spring-mount motor with small rubber wheel directly against friction band on cylinder. Like electric-assist bikes did before hub motors.... Plan_B is to machine end of bar down to compatible size, connect motor shaft via 'universal' or flexible joint. If only...
  4. Nik_2213

    Need a surface mount seal for chemical cabinet door

    Fridge-door type magnetic seals ? Plus cabinet vent to outside with riser chimney and 'cap'...
  5. Nik_2213

    I Slowing Earth’s Rotation

    While trying to rediscover a fascinating reference on Medieval tidal ranges, lost to a PC mega-crash a decade ago, I learned about the zoo of orbital issues and cycles of precession etc affecting the Moon's orbit, hence tidal stuff, day-lengths etc... Remarkably, seems distant Jupiter has much...
  6. Nik_2213

    News BITCOIN, Heists, Thefts, Hacks, Scams, and Losses

    IIRC, her appeal pipe-line has emptied: 'Orange is the new Black' looms... FWIW, did the psych assessment figure if she was 'Mad' (= delusional ) or merely 'Bad' ??
  7. Nik_2213

    Ways to join thin components in a secure way and quick to unfasten

    Does it have to hold pressure, or just the shape ?? Tangential, but I was faced with re-assembling under-sink back-board in-situ after repairing waste pipe where it ran through wall. Said pipe gnawed by rats within wall would you believe ?? Took ~15 mins to replace the push-fit pipe, many...
  8. Nik_2213

    Ramjet artillery shell of a big size

    A 'fixed' gun barrel requires a lot of materiel up-front, represents a 'Big Juicy Target'. IIRC, German V3 system, which used multiple charges in barrels' 'side-pockets' proved an abysmal failure. Worse, battery could neither dodge nor hide when RAF came knocking. Aren't the massive remnants...
  9. Nik_2213

    Lawn/Garden Convex Mirror in Backyard to reflect sunlight onto the house

    "... roof is 3 floors above..." Fair enough. FWIW, I'm adding a pair of 60 cm diameter mildly-convex (*) 'security' mirrors between cat-shelves on our garden wall to brighten this side of garden... *) Reflected objects are closer than they appear, especially T-Rex... ;-)
  10. Nik_2213

    Insights A Lesson In Teaching Physics: You Can’t Give It Away

    My last Math teacher pre-Uni had the most unfortunate reputation of asking 'trick' questions. As, that year, none of us were noticeably 'gifted', we soon learned that 'obvious' replies were probably superficial, wrong. This led to paranoid mind-set where no-one dared reply without a 's_l_o_w...
  11. Nik_2213

    Looking for a 12VDC motor with low RPM

    Low torque ? Perhaps a plastic gearbox, or a stepper motor...
  12. Nik_2213

    Trailer Frame Beam Design

    What sort of damping on those wheels ? As drawn, look like classic 'Indesuspension' with inner and outer square sections set ~45º off. Spacing looks bigger than 'close coupled' so, IIRC, you may need to go up a size / load rating. You must allow for considerable impact loads from potholes, a lot...
  13. Nik_2213

    The Short Story Thread: Post Yours Here

    Like the infamous 'Tower of Hanoi' puzzle, such recursion used to be a cruel test of your computer. Too many nested calls, brackets, indirections etc gave the feared, "Stack Overflow Error"> Hey, better than that infamous, un-documented 'HCF' op-code which released the 'Magic Smoke'... FWIW...
  14. Nik_2213

    My Friend's Math Talent: A Story of Amazement

    4-figure log etc tables... I'd a precious book of 5-figure tables, but it got 'borrowed'... And we were so jealous of the kid who'd 'inherited' a big, circular 'Engineering' slide-rule: It never 'fell off the end'. FWIW, nor did mine, which had Pi-offset markings on reverse... But a neighbour's...
  15. Nik_2213

    Lawn/Garden Convex Mirror in Backyard to reflect sunlight onto the house

    Even minimal research will find neat commercial 'light wells' with a domed roof 'catcher' feeding a reflective 'chimney' down to room...
  16. Nik_2213

    My Friend's Math Talent: A Story of Amazement

    "I told her, I see words but it takes me a whole second to give each word a name. I am amazed how fast other people read, I can't do that." I feel for you. I'm at the other extreme: Often, I don't consciously 'read' as words, sentences, even paragraphs, but devour text at a few saccades per...
  17. Nik_2213

    Local Effects of a Kimberlite Eruption?

    Almost tektites !! But seriously, per Wiki, 'potentially from anomalously enriched exotic mantle compositions', you'd have bad stuff launched into stratosphere, then raining down for miles around... This 'pop-science' discussion may amuse ...
  18. Nik_2213

    Lawn/Garden Convex Mirror in Backyard to reflect sunlight onto the house

    "You may only need to whitewash the wall." Which is what our neighbours did. Proved remarkable effective... FIL lined back of his small, lean-to greenhouse with 'radiator reflector', matte Al foil on expanded polystyrene sheet, stuck to wall with recommended 'non-solvent' tile cement. Sheltered...
  19. Nik_2213

    Solve angle issues for opening a door with a linear actuator

    Having recently disconnected a fused linear actuator, a screw-thread type, from our 'up&over', I'm reminded the door had a big stand-off bracket to mitigate the effects of adverse Sin/Cos etc, provide adequate 'starting' force...
  20. Nik_2213

    Increasing the Range of Howitzers

    IIRC, Battleships' 'big guns' wore sufficiently rapidly that a range of 'driving band' sizes was required... Also, their gun-laying analogue computers had to include both count and rate of firing, as rapid-fire wore even faster...
  21. Nik_2213

    Insights How to Measure Internal Resistance of a Battery

    Slightly tangential, I remember measuring the internal resistance of Uni lab's wall-power via current & voltage of an incremental dummy load, a bank of 60 watt incandescent lamps. And, yes, the Lab Tech did warn us NOT to 'just' use the resistance scale of the big Avo analogue multi-meters...
  22. Nik_2213

    What is the Easiest Spoken Language to Learn?

    I'm told Esperanto is probably the easiest, but has roots in Indo/Western, so may not qualify... FWIW, my parents were polyglot, but I was unable to grok any language beyond my native English (regional) until I met BASIC in ~1978...
  23. Nik_2213

    English is not normal, says John McWhorter

    Can we simply say that English is just an inherently 'Acquisitive' language ?? Something to do with sundry invasions, then ocean-spanning shipping and Empire... FWIW, English English is my 'native' language but, as a kiddy, I read enough Victorian (Strand Magazine & Kipling ) and US ( Cousins'...
  24. Nik_2213

    I Gravity of the Sun: Einstein's Calculation and Beyond

    IIRC, the Sun's gravity was calculated by Einstein et-al to provide a 'focus' about 550 AU out. Current value is ~542 AU. Aside from effects due solar oblateness, frame dragging etc, may I assume this value also applies to eg neutrinos, gravitational waves etc etc ??
  25. Nik_2213

    Hydrogen-fueled Internal Combustion Engine (ICE)

    Sounds like that design is running much too hot, at least in parts of cylinder. A generic problem with hydrogen as IC fuel, which will take some fixing... IIRC, UK airships' gasoline-type engines were intended to burn H2 as fuel, but never solved it so reverted to hydrocarbons. Also, Zeppelins...
  26. Nik_2213

    I The Effect of Wind on the Rate an Outside Spigot Freezes

    For 'historical reasons', our wall-mounted garden spigot is fed by a pipe which emerges from house, turns, meets a screw-down 'service' valve, runs along wall for a 'cubit' then rises a 'cubit'... (*) All straight copper pipe with remarkably reluctant compression fittings... When the old...
  27. Nik_2213

    Question About "Engineered Criticality Devices" In A SciFi Scenario

    Um, neutron embrittlement is subtle ?? Rather than eg 'Tin Disease', where cryogenic allotrope is suddenly, uselessly brittle... IIRC, the 'canon' FTL missiles were salvoed from a safe distance until the 'BMF' in question was sufficiently impaired. ( Fusing ? Target mass sufficed to 'trip'...
  28. Nik_2213

    Can comets create a microclimate crater on Mars 30km deep with 0.7bars?

    Why would you drop icy comet(s) on Mars when 'a shower of rocks' would release ample volatiles locked in the ice-caps ?? Also, regardless of the initial crater depth, crust/mantle structure etc, the material would be sufficiently shattered to 'slump' rapidly. Perhaps aided by released...
  29. Nik_2213

    The interior design of the central trunk of a ring spaceship

    Why not think a bit bigger ?? For my City-Class 'Convention' star-ships, I tackled this 'spin' conundrum by having pairs of contra-rotating Hab drums mounted side-saddle to the central spine. In effect, each drum was a stack of your rings. On orbit, their brackets provided un-spun docking...
  30. Nik_2213

    The interior design of the central trunk of a ring spaceship

    If ship accelerating at fractional apparent-gravity, internal transit would be more like a 'mountain railway', by analogy with SF cable-riding trams or Alpine funicular. You'd certainly have safety doors isolating each ring to contain leaks, spills, smoke, airborne toxins etc. You'd have no...
  31. Nik_2213

    Hydrogen-fueled Internal Combustion Engine (ICE)

    Bravo ! But, IMHO, a couple of issues... Hydrogen gas is a nuisance to store and transport. I had to wrangle our lab's gas chromatographs' bottled hydrogen and, even with 'Due Care' and correct handling, those big, heavy cylinders were scary... ( Our LPG cylinders were bigger, heavier and...
  32. Nik_2213

    A vanishing pencil

    IMHO, cats embody one of the many corollaries to Murphy's Implacable Law... :wink::wink::wink::wink::wink:
  33. Nik_2213

    How do you measure time on a tide locked planet?

    A caution about female cycles: several of my wife's friends had to go to boarding school as teens while their parents were 'out of country'. IIRC, was mentioned that, disconcertingly, and apparently driven by pheromones, their cycles soon phase-locked with the swiftest 'cycler' in group during...
  34. Nik_2213

    A vanishing pencil

    Should you, with a merely human life-time, open box and find it empty, I'd suggest searching where your cat usually leaves play-things... Yes, we have 'Poltercats': If neither stuck down nor in a clip-locked lunch-box, consider it moved...
  35. Nik_2213

    Ground currents to detect a civilization?

    Perhaps karst landscape ?? IIRC, the Postogna (sp) and neighbouring cave mega-systems in former Yugoslavia were significantly deepened by the Med's dramatic draw-down during Messinian Event. Just as several rivers running into Med have very deep 'buried valleys' and offshore canyons, the karst...
  36. Nik_2213

    Help requested on long-term habitable-zone stars

    Possible solution could be as face-locked mega-moon of Neptunian, beyond cold edge of usual hab-zone ?? Combination of internal heat and tidal stirring keeps 'planet' active, thick atmosphere keeps it warm, Neptunian's albedo provides some 'insolation for much of the long nights. Have a...
  37. Nik_2213

    How to calculate the weight of a gear?

    Um, unless your CAD app can simply cough up the volume, why not model the gear by parts, adding and subtracting solid-geometry primitives ? And, to a first approximation, model the teeth as a disk of 'datum circle' diameter ??
  38. Nik_2213

    The interior design of the central trunk of a ring spaceship

    I think you need to look at how very much 'stuff' is in the service core of a sky-scraper. Okay, a lot would be 'side-ways' but, unless each ring is almost self-contained, probably a good idea, the central core will be 'very busy'... Getting from spoke to spoke ? Ring_1 Spoke to core to Ring_n...
  39. Nik_2213

    B Sig fig question: Adding 3000 + 1.234

    Similar problems arise with basic statistics if you, your soft-ware or your 'trad' button-box use the 'wrong' algorithm to calculate eg standard deviation. Small differences between large numbers can easily trip you up. I had a situation where my stats calculator gave a sufficiently different...
  40. Nik_2213

    The Short Story Thread: Post Yours Here

    'Chaparral', a 'Convention' Tale... Their pioneers called the planet 'Chaparral'. Bit smaller than Earth, slightly bigger than Trilorn, there was even a breathable oxy/nitrogen atmosphere thanks to the abundance of green 'sorta-algae' in the vast low-lands' marshes. Okay, the limestone...
  41. Nik_2213

    News BITCOIN, Heists, Thefts, Hacks, Scams, and Losses

    Remember when some-one unkindly compared crypto / bit-coin boom to 'Wild West' era when a zoo of local banks issued their own scrip ?? Only took one fraud, 'oopsie' or bandito raid to break them... Nah, 'crypto' is safe, safe, safe... Until, of course, it isn't... Due Care, Please ??
  42. Nik_2213

    The difference a new computer makes for 3D rendering

    What is the mesh format, please ? Portable OBJ+MTL, or proprietary, Blender-only ??
  43. Nik_2213

    Can I move a macro object at a very small distance (around 10 nm)?

    Sounds like a job for piezo driver. IIRC, they are COTS in both linear & rotary form...
  44. Nik_2213

    What kind of fusion do you think Star Wars has?

    Beyond the surfeit of other handwavium, struck me that SW having convenient gravity control provides a fairly easy way to do fusion. Just use it to keep your uppity plasma in the middle...
  45. Nik_2213

    Docking spaceships to ring habitats

    Sorry, IMHO, is readily scalable if dock big enough to enter. Mantis/HiAb cranes grapple craft, move it aside. Rotating reference fields are not a problem. Especially if on-axis dock has guide lasers and such. Shuttle control is trivial to auto-pilot cued to dock's rotating reference frame...
  46. Nik_2213

    Docking spaceships to ring habitats

    IMHO, you need to revisit the classic sequence in '2001' where AC Clarke clinically put a 'thumb in eye' of his critics who claimed you could never, ever dock to a rotating space-station... :wink::wink::wink::wink::wink: That dock had on-axis spin, so a trivial solution if you switch co-ordinate...
  47. Nik_2213

    News BITCOIN, Heists, Thefts, Hacks, Scams, and Losses

    It's not over 'til the lawyers get rich... I'm reminded of the historical, utterly infamous 'Dutch Bulb' bubble. At its peak, rare blooms' bulbs were changing hands for outrageous prices. One such consignment of bulbs arrived at a European dock. A hungry sailor helped himself to a bulb as sack...
  48. Nik_2213

    What is the correct way of measuring remaining battery capacity?

    Inverse problem to battery charging, no ? Without going into 'smart' load-sharing etc etc, the 'trick' was to nimbly navigate that load-curve, avert wasteful over-charging and scary over-heating...
  49. Nik_2213

    Should we hit Mars with The Behemoth Comet?

    Yeah, a former colleague would say that each time I trivially falsified yet-another of his 'perpetual motion, over-unity and/or zero-point energy' notions... :wink::wink::wink::wink::wink: ( "Run IC Engine on water !" Sorry, there's a world of difference between water-injection to prevent eg a...