Wikipedia:Reference desk/Archives/Science/2015 July 28

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July 28

Multi-cylinder IC engine

Can the same cylinder design for an IC engine be used in multiple engines, with different number of cylinders? For instance, design a 250cc cylinder, and use it in 1, 2, 3, and 4-cylinder configurations for 250cc, 500cc, 750cc and 1000cc engines? Thanks! — Preceding unsigned comment added by 121.247.87.206 (talk) 09:21, 28 July 2015‎

Yes, to some extent. For instance it wasn't unheard of for manufacturers to chop two cylinders off a V8 to make a disgusting V6, and I was involved in a project that took a 4 cylinder and turned it into a 3 cylinder, but that did not go into production. But really you only reuse the con rod and piston and perhaps valves and liner, everything else is redesigned. Greglocock (talk) 09:48, 28 July 2015 (UTC)

According to something I read yesterday somewhere on the BBC website's current coverage of Formula 1, one of the engine manufacturers is currently testing a potential improvement on a single-cylinder setup (presumably a bench setup) which, if successful, will be incorporated in a forthcoming engine upgrade. This suggests that elements of the OP's scenario are valid. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 12:37, 28 July 2015 (UTC)

yes, research engines are often single cylinder engines. Greglocock (talk) 06:30, 29 July 2015 (UTC)

I remember in the late 1980s some people would bolt two Yamaha RD250 engines together to create a 4 cylinder 500cc bike. A few were featured as reader specials in Motorcycle Mechanics/Performance Bikes. Hesketh Motorcycles use the same cylinder, piston and conrod for both sides of the V (unlike say a Ducati Darmah SD900 which has different cylinder casting). --TrogWoolley (talk) 13:19, 28 July 2015 (UTC)

A significant problem that must be solved when taking a mature engine and converting it into one with a different number of cylinders is engine balance. To achieve satisfactory freedom from vibration requires much more than a new crankshaft and adding or subtracting a cylinder and piston. See balancing of rotating masses, Internal combustion engine#Cylinder configuration and balance shaft. For a high-speed engine, re-balancing with a non-optimal number of cylinders will require more effort and expense than balancing the original engine, and will deliver a poorer result. Dolphin (t) 06:42, 29 July 2015 (UTC)

When drinking sweetened drink (such as cola) is it coming to the kidneys as water molecules?

18:19, 28 July 2015 (UTC)

Water molecules among others, yes. It is delivered to the kidneys, with other waste products, through the bloodstream, after having been absorbed through the intestinal walls, and, in the case of sugars, etc., metabolized into waste products. Some of the water also leaves the body in sweat, respiration, tears, etc. StuRat (talk) 18:48, 28 July 2015 (UTC)

In most people (excluding diabetics with glucosuria) the body is pretty good about extracting as much energy from sugar as possible, which means that the carbons in the sugar leave as exhaled carbon dioxide. But the hydrogens in it go out the kidneys (and other places) as water, having found some oxygen (ultimately from the lungs) in the meantime. The other components are more complex - for example, if you read caffeine you'll see the various metabolites produced. (oxygen is involved there too, but CYP1A2 isn't trying to produce energy, but just to break stuff down into a form that hopefully will leave the body) The caffeine and all metabolites slowly go out in the urine, because urine is basically just blood that is filtered through a membrane and has a lot of different things the body wants to keep taken back out of it into the body, until whatever is left is peed away. Caramel color so far as I know is still mostly sugar and I'd expect is metabolized much like sugar. Wnt (talk) 19:26, 28 July 2015 (UTC)

Thanks. So can I understand that it doesn't matter what you drink for the kidneys (of course for the short term), always just the liquid that comes into the kidney is almost the same thing? 213.57.14.75 (talk) 19:30, 28 July 2015 (UTC)

I'm not sure what you're asking exactly. The kidney filtrate is just your blood plasma minus the large or highly-charged molecules that can't pass through the glomerulus. So whatever's in your blood will generally make it into the filtrate. I recommend CrashCourse Biology's video on the kidneys for an introduction. --108.38.204.15 (talk) 19:56, 28 July 2015 (UTC)

The general recommendation is to drink lots of water (except for people with kidney failure), as that dilutes the urine and makes kidney stone formation less likely. A high protein diet puts more strain on the kidneys, as does lots of tea (tannins) and a few other things. If you are asking about yourself, then you should consult a doctor for your specific case. StuRat (talk) 02:06, 29 July 2015 (UTC)

Well, almost. Urine is always mostly water, but there are a lot of substances dissolved in that water (see Urine#Characteristics for more information). The mixture of substances will vary, depending among other things on what you eat and some diseases that will change the composition. Two well-known examples are diabetes which will make the urine high in glucose, and asparagus which will give urine a peculiar smell. Both of these are because the blood holds a higher level than normal of a compound that is then excreted through the kidneys. Sjö (talk) 08:56, 29 July 2015 (UTC)

Has any serious effort been made to build a robotic sandworm?

Sandworms come in two types: the giant kind in fantasy that infest the deserts of Dune and some town in Nevada, and the kind that actually live and burrow through (wet) sand. I'm not too clear about what can be done in between, though. Are there factors of scale that limit how large an annelid can be and burrow through sand, and could machines get around them? What would happen if you tried to make a huge metal tube with a slightly pointed end around an intake, which gathers the sand it takes in and uses a hydraulic ram to push it backward out and the rear? Has such engineering been explored seriously? Wnt (talk) 19:13, 28 July 2015 (UTC)

Seems like it would be quite slow and use a lot of energy. What would be the goal, just to imitate nature ? In that case expanding and contracting, with a surface that grabs sand in one direction and slides in another, might be closer to that. Of course, this only works on a small scale, as you don't see Dune sized sandworms in nature. StuRat (talk) 19:18, 28 July 2015 (UTC)

Microchaetus_rappi seems to be the largest Annelid. This [1] page says max diameter is 2cm. I would not suppose that this is hard physical limit to how large of a worm can burrow, but rather a limit based upon ecological niche that also incorporates life history, resource competition, predation, general body plan, etc. etc. SemanticMantis (talk) 19:53, 28 July 2015 (UTC)

There should be a low limit on diameter, since sand or soil can only compact so much to make tunnels, and beyond that it needs to be removed to make room. As for the length, the limit on that, if there is one, should be far greater. Worms have multiple "hearts" to circulate blood, so could just add more. They breathe through their skin, so length isn't a problem there. As for nerve impulses, the various parts could operate only knowing what the parts on either side of them are doing, much like a centipede or millipede, so that's no issue either. The inability to hide from predators might be the limiting factor on length. Or the energy needed to send food through the long digestion tract could be a limit, but there the anus could just be moved to the side somewhere (which would leave open the Q of what would be left in the "tail"...maybe the reproductive tract ?). StuRat (talk) 21:30, 28 July 2015 (UTC)

There are lizards that "swim" in dry desert sand [2], and lizardy robots inspired by them [3]. --Amble (talk) 20:22, 28 July 2015 (UTC)

Here's two research papers on worm-bots [4] [5]. SemanticMantis (talk) 21:05, 28 July 2015 (UTC)

There's also the sidewinder, which "swims" through sand, but only on the surface. This has led to attempts to replicate it with a snakebot. StuRat (talk) 21:35, 28 July 2015 (UTC)

• It's rather insane to swim through sand. The golden mole does it in a way to find its food. The naked mole rat burrows in hard soil for safety and to find the tubers it eats. Herbert's sandworms used friction to power an unexplained chemical process that created Spice and oxygen. It can be discounted as unsupported fiction. The energy required is pretty much prohibitive without a huge ecological advantage. μηδείς (talk) 01:53, 29 July 2015 (UTC)±

This sounds a lot like the approximate fact that most animals that are not specialized for jumping can do a standing jump to a height of about a foot off the ground. Elephants, humans and mice...all about the same. This happens because the weight of an animal increases as the cube of it's size, but the cross-sectional area of their muscles only grows as the square of their size - so when you double the size of an animal, you don't double the height it can jump. I'd expect a similar problem with scaling up a worm - and I'd speculate that a giant sand-worm would only be able to move at the same speed as a pencil-sized sand-worm...which would seem excruciatingly slow. A robotic sand-worm could (perhaps) have a more efficient power supply - but even so, I'd expect it to have difficulties with moving at any speed.

According to this, "Bertha" (the world's largest tunnel-boring machine) manages to travel 35 feet per day - according to this, a typical earthworm manages 27 feet per hour. Bertha doesn't carry it's own power source - but has to install concrete liners into the tunnel it makes rather than allowing it to collapse behind it. Be we could perhaps imagine that a machine that's optimised for sand - and which is more interested in forward speed than in tunnel construction might maybe be able to go ten or twenty times faster - but that would only be about the same speed as an earthworm. All of which fits rather well with my intuition that all sandworms would move at about the same speed, regardless of size. SteveBaker (talk) 14:39, 29 July 2015 (UTC)