Wikipedia:Reference desk/Archives/Science/2018 March 26

= March 26 =

Transformers (not robots)
About how heavy are typical transformers of the sort which are placed on power poles? Would it be possible to squeeze one of those into a Mooney Bravo? 2601:646:8E01:7E0B:E5E2:F910:E2B4:1B46 (talk) 04:45, 26 March 2018 (UTC)
 * If you could squeeze hard enough, you could transform it into any shape you want. ←Baseball Bugs What's up, Doc? carrots→ 05:01, 26 March 2018 (UTC)


 * That aircraft can only carry 454 kg. Power pole mounted transformers can have a range of sizes. So what sort of capacity do you want? When I look at a 200kVA model, I don't think you will get it in the passenger compartment. Even if there is a freight compartment, it will be much smaller than the passenger space, and you would not get it in there. The weight of the Federal Pacific FPE-Reliance-225KVA-480-220Y-127V-3PH-Dry-Type-Transformer-Used-E-OK is 1100 pounds; a 100 kVA unit may be 600 kg, both still too heavy. Graeme Bartlett (talk) 06:07, 26 March 2018 (UTC)
 * That 3PH is likely a set of three single-phase transformers in a metal box for mounting in dry locations. A pole-mount is usually separate single-phase units wired together. Consider instead 100 kVA Utility Pole Mount Transformer - 14400/24940Y Wye-N Primary - 240/480V Secondary - Copper, which lists a weight of 1220 pounds. It takes 477 pounds of mineral oil, and I'm not sure if that is included in the 1220-lb weight. DMacks (talk) 06:37, 26 March 2018 (UTC)


 * Heavy. They're stationary and located in remote places, so they're designed for reliability, not light weight. They're based on a heavy iron core and on oil cooling.  If you wanted a lightweight design, could afford  to sacrifice some efficiency for weight saving, and had access to a stream of cooling air, then you could do a lot better. You might even switch to a higher line frequency, which would allow a more efficient core material, like a ferrite. Andy Dingley (talk) 10:03, 26 March 2018 (UTC)


 * Great -- and the useful weight includes the fuel (all 534 lbs. of it) as well as the payload. So then tell me, what other equipment could be needed at a shoe factory which is light enough for the Mooney to carry?  (This is for a fictional scenario -- I'm doing an IFR flight in FSX from Boeing Field to Scappoose Industrial Airpark, and I want something I could use as a payload -- the story being that something broke at the factory and they need it replaced right away, and I'm the only pilot who can deliver the spare parts on such short notice.) 2601:646:8E01:7E0B:E5E2:F910:E2B4:1B46 (talk) 12:42, 26 March 2018 (UTC)
 * Well traditionally, it's a Shoe Factory Repairman.
 * I used to work for a guy who flew a helicopter, lived a long way away, and we had machinery in a nearby car factory built on an old airfield. He'd often fly up and we'd both visit this factory by helicopter, just so that he could keep up his flying hours and also treat it as a business expense. Andy Dingley (talk) 13:40, 26 March 2018 (UTC)
 * What era is this supposed to be? eBay lists lots of relevant equipment of different vintages and sizes, and many of the larger ones obviously have lots of small but critical parts that could need replacing too. DMacks (talk) 16:19, 26 March 2018 (UTC)
 * It's supposed to be early 21st century (it's part of an ongoing story which I'm telling with a series of YouTube gaming videos, and there will be a time warp which sends the main character 100 years back in time, but at this point the time warp hasn't happened yet.) 2601:646:8E01:7E0B:E5E2:F910:E2B4:1B46 (talk) 08:33, 27 March 2018 (UTC)


 * When trying to put industrial equipment in a small airplane (or a large one!), you must concern yourself not only with weight, but also with balance. In fact, the February issue of FAA Safety BLAST had a great article on this exact topic: Minding Weight, Maintaining Balance from the NTSB.  Here's the official Weight and Balance textbook, and here's an unofficial online calculator for the Mooney M20J: "This calculator is presented for educational purposes only."  Remember: you need a correct calculation with exact data not only for every make and model, but for each tail number, whose exact empty weight and balance may vary from the standard aircraft.
 * As a general rule of thumb, putting two hundred pounds in the baggage compartment of a small single-engine aircraft does not work, even if it weighs less than the aircraft's "total useful load." Overloading the baggage compartment moves the center of gravity aft, possibly beyond the aircraft's safe operating envelope.  When that occurs, the aircraft is difficult to fly, and may be aerodynamically unstable.  In the worst cases, the aircraft is completely uncontrollable - e.g. no amount of elevator trim can keep the aircraft in level flight; nothing you push or pull in the cockpit will make any difference.
 * And don't forget to account for fuel weight and balance - for all phases of the flight - because fuel gets used up in the air! These little piston engines can carry a lot less actual cargo than you might think!
 * The pilot's job begins long before they take their seat in the cockpit!
 * Nimur (talk) 15:36, 26 March 2018 (UTC)

Re: "So then tell me, what other equipment could be needed at a shoe factory which is light enough for the Mooney to carry?", it just so happens that I designed a shoe factory many years ago (not the building, but pretty much everything inside it other than the workers). Your best bet for critical part that a small aircraft could carry is an electric motor. They range in size from the size of your fist to too heavy for the plane, so you can write a "just barely able to make it" scenario and have it be believable. If you want to get fancy, have the plane carry a servomotor and associated control unit. Also, it isn't plausible that no pole mounted transformers are available; every building has one.


 * Consider also that, presuming your fictional work might have non-North American readers, such pole-mounted transformers would likely be unfamiliar to them. For instance, as an aged Brit who has worked for facilities maintenance and installation companies in the UK, I've never seen or heard of them before now. {The poster formerly known as 87.81.230.195} 2.218.14.51 (talk) 23:40, 26 March 2018 (UTC)


 * Thanks! I don't know all the details of a shoe factory (I'm a chemist by trade, not a shoemaker or a mechanical engineer), but I do know the kinds of machines they use in general, and I know that lots of stuff uses electric motors -- so just one last question, which machines at such a factory are the most critical (i.e. if they break down, the whole plant could go offline -- which would give extra urgency to having it replaced right away, even if it means paying extra AND breaking normal procedure)? 2601:646:8E01:7E0B:E5E2:F910:E2B4:1B46 (talk) 08:33, 27 March 2018 (UTC)


 * That would be the injection molding machine that puts rubber soles on shoes. If your fictional shoe company makes all-leather shoes then there is no answer; people were making those kind of shoes using simple hand tools before 3000 BCE. --Guy Macon (talk) 12:20, 28 March 2018 (UTC)
 * Thanks! And I happen to know how they work, so as of now the question is resolved. 2601:646:8E01:7E0B:7C09:CBDA:7D04:34CA (talk) 03:41, 31 March 2018 (UTC)


 * Aside: This is not on topic but. During the 2nd World War the RAF often had to bomb U boats  at night. Radar could detect them from a distance, but  the boats immediately did an  emergency  dive on the aircraft’s approach. The only way that the aircraft could  then home in  on the U-boat was to illuminate the whole target area with light for visual aiming.  A generator to provide that amount of illumination was too heavy, but since they only need  brief intensive illumination they use lead acid batteries. As Michael Caine might have said “ not a lot of people know that”. Aspro (talk) 21:08, 27 March 2018 (UTC)


 * Leigh Light, Leigh Light Operation --Guy Macon (talk) 12:20, 28 March 2018 (UTC)


 * Did anybody caught the idea to use an electronic transformer like SMPSs. HVDC ist also made this way to have less material, less mass, less weight and more efficiency. -- Hans Haase (有问题吗) 16:23, 30 March 2018 (UTC)


 * Someday, maybe, but an electronic transformer that can handle thousands of volts and hundred of amps is not practical at this time. See [ http://www.powerelectronics.com/alternative-energy/are-solid-state-transformers-ready-prime-time ]. BTW, do you have any evidence for that "more efficiency" claim? Iron and copper are really, really efficient. --Guy Macon (talk) 06:00, 31 March 2018 (UTC)

Non-cylindrical aerosol can
Would it be too bothersome, expensive or unsafe to design an aerosol can (for deodorant, for example) that does not have a cylindrical form? It would obviously not have any practical advantage over a cylinder. But in product design many things are the way they are just to 'look cool'. --Hofhof (talk) 12:21, 26 March 2018 (UTC)
 * An aerosol can is basically a pressure vessel, Pressure vessel has a discussion of the issues involved, and even has an aerosol can as an example. -- Jayron 32 12:35, 26 March 2018 (UTC)
 * A spherical can would have advantages. Looie496 (talk) 13:36, 26 March 2018 (UTC)
 * And disadvantages. Please see the above link, which mentions both.  -- Jayron 32 13:43, 26 March 2018 (UTC)


 * Very few are simple cylinders. Even hairspray has domed ends, one concave, one convex.
 * The pressures are low. It's not hard to make them of any rough shape, one-off tooling costs permitting. What's more of a design problem is to avoid unsupported corners. A flat-sided oval tank may be pressurised, even though it has flat sides, but sharp corners are avoided because they would represent the highest stresses and would be the first part to require reinforcement. It's common to have sharp corners where the ends join on, but these are only a single edge, not multiple edges joining in a corner, and they also have a stiffened rim as reinforcement. Andy Dingley (talk) 14:02, 26 March 2018 (UTC)
 * I found Shaped Aerosol Cans, but they are still fundamentally cylindrical and I imagine more expensive than the plain ones. Alansplodge (talk) 15:01, 26 March 2018 (UTC)
 * As a digression, what's the best name for a shape like this which is an "un-prism"? These shapes seem to maintain radial symmetry (for structural reasons about the recognised benefits of a circular pressure vessel), but vary the diameter along their axis. Andy Dingley (talk) 19:59, 26 March 2018 (UTC)
 * A solid of revolution is circular symmetry. I don't understand the "unprism" terminology idea. DMacks (talk) 20:51, 26 March 2018 (UTC)
 * Thanks, that's another tickbox for the dementia diagnosis. My "un-prism" is that these are asymmetric in just the way that prisms are symmetric. Andy Dingley (talk) 21:22, 26 March 2018 (UTC)
 * No worries:) Thinking more, some of them could be more an antiprism, which has radial symmetry with specific steps around rather than a smooth rotation. DMacks (talk) 21:42, 26 March 2018 (UTC)


 * Lynx (known as Axe in the US) has cans with hard corners like this. I don't think this shape has a technical name, but it's a lofted shape with a circular cross-section at one end, and a slightly rounded square at the other end. I think being flat makes it a bit easier to hold (so you spray it where you want to spray it, rather than accidentally pointing the nozzle in the wrong direction). Smurrayinchester 09:26, 27 March 2018 (UTC)