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londonskies

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  • Ice Arch - 6' Freestanding

    A possible labour-saving variant: create the catenary upside-down, hanging from its ends. You can then either leave it hanging or carefully try to turn it the other way up!I haven't tried this, and Oxford UK is not cold enough to do so right now, but I would think that some procedure like the following could evolve into a usable alternative technique. The transverse strut/plank would not be necessary if you plan to leave it hanging (for hanging catenary you could simply omit plank and screws from my proposed method, and thread a strong thin white string through entire tube before filling and before freezing, hanging it from each end of the string ready for post-freeze skinning ... though you might want to stretch the innertubes a bit to avoid unsightly wrinkles).Proposed method: hang a 2m…

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    A possible labour-saving variant: create the catenary upside-down, hanging from its ends. You can then either leave it hanging or carefully try to turn it the other way up!I haven't tried this, and Oxford UK is not cold enough to do so right now, but I would think that some procedure like the following could evolve into a usable alternative technique. The transverse strut/plank would not be necessary if you plan to leave it hanging (for hanging catenary you could simply omit plank and screws from my proposed method, and thread a strong thin white string through entire tube before filling and before freezing, hanging it from each end of the string ready for post-freeze skinning ... though you might want to stretch the innertubes a bit to avoid unsightly wrinkles).Proposed method: hang a 2m plank horizontally in freezing location, 3m off the ground, with one very long slightly angled screw or stiff wire at each end to connect the frozen catenary to underside of the plank. Then get 2 or 3 large-wheel-diameter bicycle inner tubes and cut and join (use bicycle repair kit glue and a bit of skill - make sure the overlapped joint is waterproof) to make a long open-ended pipe. 26" innertube opens up to be circa 2.07m, so a couple of these might give you a long enough catenary. Position the tube ends so that the tube hangs from the plank, each tube end concentric with a long screw. Fill with water so the water brims up to meet the plank. This needs some care: you want a large contact surface between the water and the plank. Maybe use screws and washers to stretch the mouth of the tube into a large oval around the nail? And somehow fill with water, maybe through hole drilled in plank (you might get some bonus ice-strengthening sawdust in your tube while you are at it! Leave it to freeze, but the sagging tubular bladder might creep and need topping up, or squeezing by wrapping more bicycle innertube spitrally around it mid-span, to ensure that the water stays in contact with the plank. Possible problem: you want mid-span to be thinnest, or at least not thickest, but filling with water may cause some undesirable longitudinal stretch near ends and undesirable radial stretch near midspan. Another possible problem: the overlapped joints might stretch less, causing undesirable local constriction. When it is well frozen, skin the innertube off the ice by cutting longitudinbally with scalpel, and maybe have multiple people very carefully (good luck with that!) turn the entire structure over if you want an upside-down (rainbow orientation) catenary.If anyone has the cold weather and the will to try this please let me know, as it's just untested fantasy design! :) Dom#DisruptiveOpportunist

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    • Plastic Glove Upcycled From Plastic Air Bag Bubble Packaging Padding
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  • londonskies commented on Epbot's instructable Penny Desk!

    I make it $2.96 per sq Ft.Calc:Hex-packed circle density is 0.90689968211 (all figures here are approx.)Diameter of US 1c = 19.05 mm. Area of 1c coin = pi*r^2 = pi*(19.05/2)^2 = 285.022956992 sqmm. Therefore close-packed 1c coins per sqm =1000*1000/285.022956992*0.90689968211 = 3181.84784721 or 3181.84784721/3.28084^2 per sq Ft = 295.603318905 1c coins per sq FtDom

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  • londonskies commented on Epbot's instructable Penny Desk!

    Great instructable thanks ... I didn't know about the blowtorch technique, useful to learn of this.To calculate how many coins you need you might want to adapt the following UK penny calculations to your preferred coin size ...How many British 1 pence coins could you fit in a meter squared?if 1p coin diameter= 20.3mm ...1p coins per sqm square packed: (1000/20.3)^2 = 2426.65. That s a coindensity of pi/4 or approx 78.54%.But lets work out the coin density if arranged in hexagonal closepacked layout, Let s work it out for circle of diameter=1 unit. Sketch4 adjacent circles with centres forming a rhombus. Within the rhombusyou have a pattern which when repeated describes the entire hexagonalclose-packed layout.Rhombus area = (1^2-.5^2)^.5 = .75^.5 = 0.86602540378Area which is within a circl…

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    Great instructable thanks ... I didn't know about the blowtorch technique, useful to learn of this.To calculate how many coins you need you might want to adapt the following UK penny calculations to your preferred coin size ...How many British 1 pence coins could you fit in a meter squared?if 1p coin diameter= 20.3mm ...1p coins per sqm square packed: (1000/20.3)^2 = 2426.65. That s a coindensity of pi/4 or approx 78.54%.But lets work out the coin density if arranged in hexagonal closepacked layout, Let s work it out for circle of diameter=1 unit. Sketch4 adjacent circles with centres forming a rhombus. Within the rhombusyou have a pattern which when repeated describes the entire hexagonalclose-packed layout.Rhombus area = (1^2-.5^2)^.5 = .75^.5 = 0.86602540378Area which is within a circle AND within rhombus =pi*.5^2 = 0.78539816339Therefore circle density is 0.78539816339/0.86602540378 =0.90689968211. A density of circa 90.69%.Area of 1p coin = pi*r^2 = pi*(20.3/2)^2 = 323.6547 sqmmTherefore close-packed coins per sqm =1000*1000/323.6547*0.90689968211 = 2802.05936175This doesn t account for edge conditions. circa 2802 coins per sqm. Good luck!Dominic P

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