Wikipedia:Reference desk/Archives/Science/2015 July 1

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 1

How to dissolve/remove insulation film on magnet wire?

Resolved

Hello Everyone. I would like to know how to dissolve/remove the insulation film on magnet wire. Also can this be done using everyday household products? Thanks for your help in advance, —SGA314 I am not available on weekends (talk) 13:35, 1 July 2015 (UTC)

Probably most knives would work. Nil Einne (talk) 13:48, 1 July 2015 (UTC)

Yeah I already did that. The problem with using a knife is the knife ends up cutting off most of the copper strands. Although that does work, albeit not very well. Is there any sort of solution I can whip up to dissolve the coating? I also read that the coating can only stand up to so much heat. So I was thinking about throwing it in the oven with a temperature of 500°F(of course I would first strip off the black plastic exterior). But I would like to use this only as a last resort. —SGA314 I am not available on weekends (talk) 13:59, 1 July 2015 (UTC)

Most magnet wire insulation will either burn or melt off (depending on the composition), and cleaning small amounts with a butane torch is not uncommon. However, the combination of carbon monoxide and isocyanates in the reaction product is really bad to breathe, so unless you are talking about very small quantities, I wouldn't recommend using heat without proper fume protection. Dragons flight (talk) 16:47, 1 July 2015 (UTC)

@Dragons flight: I am only talking about a fraction of the length of a set standard headphone wires. So I think that fumes wouldn't be a problem. However, there is some sort of soft, white cloth that the wire is wrapped around. I think that might cause a problem. However, I don't know whats it made out of. —SGA314 I am not available on weekends (talk) 16:52, 1 July 2015 (UTC)

Maybe sandpaper of a high grit carefully rubbed would get away the clear insulation without being strong enough to take down the copper. 20.137.7.64 (talk) 14:23, 1 July 2015 (UTC)

Great idea. I will try that. I don't know if it will make a difference but I have 4 wires. 2 of then are clear insulation and the other have green and blue insulation on them. Does the color make a difference? —SGA314 I am not available on weekends (talk) 14:26, 1 July 2015 (UTC)

Are you aware of wire strippers? From a standpoint of stripping insulation, it's not clear to me that magnet wire is much different than any other insulated wire, and hence I think the standard tool for the job should work just fine. (p.s. knives also usually work fine, if much slower, given enough practice at not cutting the wire. It's just matter of knife handling skill. Sort of like how some people can peel a potato or onion in a few seconds, while others take minutes :) SemanticMantis (talk) 14:42, 1 July 2015 (UTC)

In this case, the insulation adheres to the wire, so wire strippers won't work very well. 199.15.144.250 (talk) 14:53, 1 July 2015 (UTC)

My point exactly 199.15.144.250. Yes I do know about wire strippers. But I am talking about coated insulation, not just plastic insulation. Read about it here: Magnet wire. Also, I am working with very light gauge speaker wire. Look at a pair of ear buds and see what I am talking about. —SGA314 I am not available on weekends (talk) 15:40, 1 July 2015 (UTC)

Ok, guess I was wrong, thought it couldn't hurt to point out. But I have stripped insulation from speaker wire using wire strippers without much problem; maybe different types adhere differently. SemanticMantis (talk) 16:06, 1 July 2015 (UTC)

Emery cloth (but I expect fine sandpaper would be all right). Thincat (talk) 15:34, 1 July 2015 (UTC)

Huh, never heard of Emery cloth. Good to know. —SGA314 I am not available on weekends (talk) 15:42, 1 July 2015 (UTC)

I did it! I figured out how to get the coating off. I just burned it off with a candle lighter. The trick is though not to heat the wire so much that it glows brightly and falls off. What I do is I slowly move the flame up and down the wire until it starts to glow. Then I stop and blow on the wire to cool it down. And that's it. Now you can twist the wire with other bare conductive wires and it will conduct. If the wire doesn't conduct, then repeat the process. and test wire again. Thanks everyone for all your suggestions. Special thanks to @Dragons flight: for his suggestion. —SGA314 I am not available on weekends (talk) 19:20, 1 July 2015 (UTC)

That's not a safe method. You can easily end up with brittle or oxidized wire. If you could use something like a soldering iron or heat gun it would be much better, as those don't heat the wire nearly as much as a candle flame. Looie496 (talk) 13:32, 2 July 2015 (UTC)

I don't have access to a soldering iron or a heat gun. That's why I used a candle lighter. If I did have access to a soldering iron, I would definitely use it. And yes, the wire could oxidize or become brittle. But, if you do short strokes on the wire with the flame, it doesn't get brittle or oxidize. I have learned when the wire starts to glow, that's the time to pull the heat off and let the wire cool. —SGA314 I am not available on weekends (talk) 19:07, 2 July 2015 (UTC)

Some acids will do the job, but may also etch the metal, e.g. nitric acid, but that is not a household chemical. Martin451 20:28, 1 July 2015 (UTC)

That's good to know. It sounds way better than my current method described above. I will give that a try. —SGA314 I am not available on weekends (talk) 19:07, 2 July 2015 (UTC)

If it's an enamel based insulation you can use acetone (nail polish remover). Other solvents may work as well (home depot has many). If using a lighter or soldering iron, put a clip-on heat sink (soldering kits usually have them. It will stop the heat from transferring as much down the wire. --DHeyward (talk) 03:17, 2 July 2015 (UTC)

I am not working with a wire that has a heat sink or transformer at the end. I am only working with an audio wire. So heat transferring down the wire isn't a problem. —SGA314 I am not available on weekends (talk) 19:07, 2 July 2015 (UTC)

It's not a heat sink at the end of the wire, it's a clip on metal piece that looks like pliers. The reason is so you don't melt insulation beyond the point of attachment. It really just adds mass. It's also used when you are soldering wire and only want the solder point to melt, not the other connection-point especially with short wires. --DHeyward (talk) 20:12, 2 July 2015 (UTC)

Ok good to know. —SGA314 I am not available on weekends (talk) 13:51, 3 July 2015 (UTC)

Ape Ejaculation

(Moved from Entertainment desk by SemanticMantis (talk) 14:52, 1 July 2015 (UTC))

How does the quantity of ejaculation compare between different primates. For instance, people, chimpanzees and gorillas. Chimps, being smaller have the largest testicles whereas gorillas the smallest. People are in the middle. So who's load is the most? — Preceding unsigned comment added by 203.126.168.2 (talk) 14:23, 1 July 2015 (UTC)

Check out the book Reproductive Biology of the Great Apes: Comparative and Biomedical Perspectives here [1], maybe this book [2] the article Ejaculate quality, testes size and sperm competition in primates here [3], and the article Comparative Population Genomics of the Ejaculate in Humans and the Great Apes here [4]. If those don't have the info, it's probably in the refs cited therein. Some are freely accessible and some are not. You can ask me or at WP:REX if you can't get full access to an article (often doing a regular google search for the full title will bring up an available copy). SemanticMantis (talk) 14:50, 1 July 2015 (UTC)

Vinegar to clean glass - why?

Why is vinegar commonly recommended to clean glass? What are the chemical reactions intended? ----Seans Potato Business 16:52, 1 July 2015 (UTC)

Vinegar is mostly water and Acetic acid, which is a weak acid. Acetic_acid#Solvent_properties discusses the properties that make it a decent glass cleaner - in part it is because it can dissolve both polar and non-polar compounds. SemanticMantis (talk) 17:21, 1 July 2015 (UTC)

A few-percent acetic acid in water is pretty much "water" not "acetic acid", and is probably still a very poor solvent for non-polar materials. A petty common organic lab technique is to do a reaction in 100% acetic acid as solvent, then add water and the product precipitates out in good yield. It usually only takes 1–3 volumes of water vs the acid to accomplish it, which is still several times higher concentration of the acid than vinegar is. DMacks (talk) 19:23, 1 July 2015 (UTC)

(ec)Vinegar (like most acids) removes limescale (calcium carbonate), converting it into CO2, H2O, and a calcium salt - Calcium acetate in the case of vinegar. This salt is usually water soluble, and hence easy to remove. --Stephan Schulz (talk)

Or you can use hydrofluoric acid, which will leave the glass so clean it will look like there's no glass there at all ! :-) StuRat (talk) 04:37, 2 July 2015 (UTC)

Dead slow, or damn fast

Up ahead on the track you know your loco engine and train will have to cross a severely damaged bridge. If the bridge fails, you are dead. What is the best speed to crosss the bridge. Dead slow, or damn fast??--86.149.100.245 (talk) 19:54, 1 July 2015 (UTC)

On foot.

It depends on the bridge. Remove as much weight as possible from the train, and go slowly. You will be less likely to damage the bridge than going fast. If there is a reasonable chance of the bridge surviving, then this is the best strategy.

If it is certain that the bridge will fail, then again remove all weight, and go as fast as possible, hoping to clear the bridge before it collapses.

In all circumstances, get the passengers, unneeded crew to walk across first, carrying as much needed supplies as possible. Unhook unneeded carriages. Martin451 20:23, 1 July 2015 (UTC)

The question is "What speed?" not "What else could I do?". SteveBaker (talk) 21:07, 1 July 2015 (UTC)

I think it has to depend on how the bridge is damaged.

1. Suppose a critical bolt has worked itself loose and is just holding together by an inch or so? Going fast would presumably create vibrations that would shake the bolt loose and destroy the bridge - where going slowly might avoid that.
2. Suppose it's a key component that's got a small crack in it - the process of crack propagation might take time - so going slowly would spell disaster, where getting across before the crack propagates to a disaster point would save the train.
3. Suppose induced oscillation in the bridge would spell disaster? In that case, travelling at some particular speed at which the oscillations are at their worst would destroy the bridge and any other speed would be safe. With that possibility, there is no specific speed which is better than any other - unless you know a lot about the bridge and how it's failing.

My (admittedly intuitive) bet is that there is no one "right" way - it depends on the nature of the damage, the nature of the train, etc.

SteveBaker (talk) 21:06, 1 July 2015 (UTC)

Dead slow, to mitigate the Hammer blow forces.--Aspro (talk) 21:21, 1 July 2015 (UTC)

But the bridge could fail under sustained static loading. What Then??--86.149.100.245 (talk) 21:36, 1 July 2015 (UTC)

I believe that these "hammer blow" forces only apply to steam locomotives...so that's unlikely to be a good answer in general. Also, I disagree that "dead slow" is always the right answer - it's easy to imagine engineering situations where the frequency of some vibration induced by the train is the cause of the final collapse - and the appropriate speed would be something that doesn't induce that frequency...which could quite easily mean that going faster is better. Hence the answer is still "It depends" and not "Slow". SteveBaker (talk) 18:38, 2 July 2015 (UTC)

A train? Over a failing bridge? Trains need tracks that are smooth and uniform in the separation between rails. Unlike what you might see in movies, I don't think there is any way that going "damn fast" is going to allow a train to get across a failing bridge. Once it actually starts to fail, it will already be too late for the train regardless of its speed. The only hope is that you can cross the bridge without it failing, which for most failure modes will make slow the only practical option. Dragons flight (talk) 22:45, 1 July 2015 (UTC)

I am also reminded of a mythbusters episode [5] where they tested whether it is possible to make a last second leap to safety from a failing rope bridge. Their answer in that case was no. Once the rope loses tension there is no longer anything to push against so you can't make an effective jump. Of course, rail bridges are not supported by simple tension, but if the failure mode of the rail bridge is such that the rails are really falling from under the train, then I'd expect the outcome to be similar and that no amount of speed is likely to change that. Dragons flight (talk) 18:49, 2 July 2015 (UTC)

What then? Then it's your own fault for collapsing your bridge!

In the United States, railway bridges are 100% private - (unlike all other bridges - pedestrian bridges, automobile bridges...) - there is no government agency or public utility who oversees railway bridges or even vets them for safety. For example, have a read through this article on a new rail bridge route proposed near my childhood hometown: an LPG rail transport bridge over Watkins Glen State Park. So: if a train crushes a bridge and the bridge fails catastrophically, it's your own fault for owning a rail bridge and operating a railroad! (This is why the Watkins Glen issue is so controversial: how can we make sure a fiery explosion doesn't engulf our state park if our regulators have no authority?)

As I enjoy reading about railroads and federal regulations, I went digging into the details here, and I found this Explanation and Amplification of FRA's 'Statement of Agency Policy on the Safety of Railroad Bridges' . If you own or operate a railway, you should have a professional engineer with competency "in the field of railroad engineering" evaluate whether your bridge is safe at any speed. It is your responsibility to determine what speeds are safe! Specifically, the FRA recommends against returning rail track to operation over a suspicious bridge - even at restricted speed, until the actual structural problems with the bridge are diagnosed and resolved by a competent engineer. However, this is a recommendation and not a regulation! FRA Track Safety Standards Fact Sheet.

Nimur (talk) 22:49, 1 July 2015 (UTC)

But I thought "unsafe at any speed" wasn't applicable to choo-choos? Nyttend (talk) 23:29, 1 July 2015 (UTC)

One case where faster is better is the "Evel Knievel" jump (my name for it):

  ->
-------+
       |     +------
       |     |
       +-----+

Here there is a break in the track and a drop. If you go fast enough you will land safely on the other side, while if going too slow you will splat into the wall on the other side. I've seen this at work in the case of a car driving over a pothole. However, with a train, it would somehow need to get back on the track, although perhaps derailing on the other side would be less dangerous than crashing down into the ravine. StuRat (talk) 00:57, 2 July 2015 (UTC)

The only solution I can think that mitigates both dynamic and static problems (assuming the bridge is level), is to accelerate as fast as posible and coast across the bridge. Coasting should be a static load (though the rate of change of mass on the bridge could still be a problem). Under power, there is a also a lateral stress on the rails that isn't present wjile rolling except for the rolling friction force against motion). It's still not a tractable problem without knowing the mechanism of failure (i.e. damage). If the damage is exacerbated by cantilever or horizontal forces is a different solution than vertical load damage. Now, if you have a near lights speed drive....you probably don't need a bridge. --DHeyward (talk) 04:11, 2 July 2015 (UTC)

There is no point in risking being dead, so dead slow obviously. At the slow rate of one cm per day you will have time to have a crew work on getting the bridge fixed before you begin crossing. Otherwise enlist the help of Thor to hold it together if he is available. --Wetdreamshere (talk) 04:43, 2 July 2015 (UTC)

Guys, you all seem to be repeating a lot of pseudoscience, and without any reference at all! Have you got a professional engineering license with specialization in railroad engineering? Have you studied bridge design as part of your civil engineering curriculum? Have you even bothered to spend a half hour reading about this topic before speculating on it? Why do you think riding slowly is any safer? At least User:DHeyward has shifted the discussion towards static and dynamic loads, which is a step in the right direction towards an analytical solution. But without actually studying a specific bridge, performing detailed and rigorous analysis, we can't know that riding slowly is even slightly safer than riding fast. In fact, I've already provided a source which specifically calls out this fallacy as a contributing factor to many accidents!

Step back, find some reliable sources - like a textbook on railroad bridge engineering, or a website on Railroad Bridge Safety Standards. Read it. Exercise some critical thinking. Then you can provide informed commentary, instead of idle (and often wildly inaccurate) speculation. Engineers do not validate bridge safety using ASCII-art and unrefined gut intuition. Nimur (talk) 05:33, 2 July 2015 (UTC)

Thor and company doesn't really need a textbook because they will hire only the very best qualified bridge contractors. --Modocc (talk) 06:13, 2 July 2015 (UTC)

Critical thinking tells us that the answer clearly depends on the state of the bridge and the exact nature of the failure that it's suffered. So the answer is "It depends" - and no amount of additional reading or reference hunting will improve on that answer since the OP is unspecific as to the nature of the failure, the size/weight/length/etc of the train or how slow is "slow" and how fast is "fast". So we don't need to go to all the difficult lengths you describe to answer the question clearly and simply. SteveBaker (talk) 18:34, 2 July 2015 (UTC)

@Nimur: Give these guys a break. They're not going to give a professional answer because the professional answer about how to cross a damaged bridge with a train is pretty obviously going to be don't, which is no fun at all. :) Wnt (talk) 03:39, 4 July 2015 (UTC)

Right, and while "it depends" is the ultimate answer, we can certainly help by listing many of the things on which it depends/cases where faster or slower would be better. (And we can be reasonably certain the OP isn't planning on actually driving a train over a damaged bridge, so the risk of harm is minimal.) StuRat (talk) 03:08, 5 July 2015 (UTC)

If I may digress into fiction: This exact situation occurs in Jules Verne's famous novel Around the World in Eighty Days. They decide to go as fast as possible; they get across, but the bridge collapses behind them. Of course Verne was a science-fiction/adventure writer, not an engineer! Incidentally, in the novel the speed they reach is 100 mph (and yes, even in the original French it's given in miles per hour): in fact the speed record for steam locomotives at the time was around 80–90 mph. But in the 1956 movie they changed it to 30 mph!

And back to real life: in 2005 there was a bridge that collapsed under a train in Italy, but the train got across—because the rails remained intact and supported it! See Eurostar 9410 derailment. --70.49.171.136 (talk) 07:08, 2 July 2015 (UTC)

No seasons

Is there anywhere in the world that experiences no significant meteorological seasons, places where the stars are the only part of nature that changes from month to month? Of course it would have to be on or close to the equator, since the amount of sunlight can't vary very much. But it seems like most equatorial regions have distinct dry and wet seasons; are there any exceptions? Just looking for locations on land, not oceanic locations. Nyttend (talk) 21:38, 1 July 2015 (UTC)

Map of all tropical cyclone/hurricane tracks from 1945 to 2006.

The answer here [6] seems useful. Dragons flight (talk) 22:13, 1 July 2015 (UTC)

Singapore may have the smallest seasonal amplitude of any well-known place. It has near-zero temperature seasonality and a modest annual cycle of rainfall due to the monsoon. Short Brigade Harvester Boris (talk) 01:08, 2 July 2015 (UTC)

I remember a professor in college saying that Quito, Ecuador - due to the combined facts that it is on the equator and its elevation is over 9000 feet - was mild and spring like all year round. According to Quito#Climate it looks like there is a little more to it than that. MarnetteD|Talk 03:22, 2 July 2015 (UTC)

Being on a small island in the middle of an ocean helps to moderate temperatures (as long as the ocean doesn't freeze over). So, I'd go with an island near the equator, for temperatures. Of course, hurricanes/monsoons/cyclones are still a possibility, but some spots seem relatively safe from those, too, as the pic of historic hurricanes and cyclones shows. StuRat (talk) 04:27, 2 July 2015 (UTC)

Based on people that have lived there, I have to go with Singapore as well. Ocean islands are temperate but the ocean is pretty seasonal everywhere. Another interesting place is the southpole. Not really a season as one long 6 month day followed by a 6 month night. No rain and the temperature is only cold. At "night" planes can't get there though. --DHeyward (talk) 04:50, 2 July 2015 (UTC)

"Cold" is a relative thing. South_Pole#Climate_and_day_and_night puts the lows at -20°F in summer versus -80°F in winter. That's the difference between relatively normal winter gear and something more akin to a space suit. StuRat (talk) 05:09, 2 July 2015 (UTC)

Ahhh but that's a day/night diurnal difference, not seasonal. :). Besides, for me, the difference between -20°F and -80°F is like the difference between dead and deader :). --DHeyward (talk) 05:44, 2 July 2015 (UTC)

That is -29 °C to -62 °C for those that use sensible units. Fgf10 (talk) 07:23, 2 July 2015 (UTC)

That makes it sound so much warmer. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:12, 3 July 2015 (UTC)