117 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

There are two main reasons why glass is still preferred over say PMMA. The first is durability. As long as it isn't broken, the glass in a window can easily last for hundreds of years in good ...
Chris Johns's user avatar
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47 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Here is a plastic (most likely PMMA) window, in a boat, after only 37 years. In addition to the obvious scratches, the outer surface has developed a cloudiness : possibly from degradation due to ...
user_1818839's user avatar
  • 1,620
31 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

What are the requirements for window glass? Resistance to moisture Resistance to UV radiation Resistance to cleaning agents Very high transmission in the visible spectrum (There are many more, from ...
JHK's user avatar
  • 1,618
29 votes
Accepted

Why would a train automatically derail if a signal is passed at danger?

Firstly, the incident happened as the train was leaving a siding passing a shunt signal. These provide less authorisation than a normal signal does, even when they are not at danger (the train can ...
gsnedders's user avatar
  • 406
24 votes
Accepted

Why would you launch a large ship by dropping it sideways?

A specific reason for doing this is simply when there isn't enough room to do a bow or stern first launch. This is often the case when a ship or boat is built in a yard on a river or canal either ...
Chris Johns's user avatar
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21 votes

Why would a train automatically derail if a signal is passed at danger?

While I'm sure it caused less damage than a train collision Exactly. This is a last-resort response intended to avoid a full-on collision. A derailed train causes some damage and is a mess to clean ...
Olin Lathrop's user avatar
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15 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

I actually did make windows out of plexiglas for an outbuilding. I could work them to the shape I wanted and they were lightweight. However, I discovered that they indeed scratch easily: just trying ...
JDługosz's user avatar
  • 257
13 votes

What is this locking pin for a hinge called?

That is a ring-grip quick-release pin, sometimes referred to as clevis pins. McMaster link
jko's user avatar
  • 2,347
11 votes

Why would a train automatically derail if a signal is passed at danger?

Why derail? If the train went past a red signal, then all of the other safety systems already failed! The method of last resort is to make absolutely sure that the train will not travel down the track....
hazzey's user avatar
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10 votes
Accepted

Is it safe to drop a bomb?

In general a modern commercial/military explosive device will not explode if dropped. The most common commercial/military explosives such as C4, TNT, ANFO are catagorised either as Secondary or ...
atom44's user avatar
  • 2,641
10 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

After some research, we are using glass windows as it was used traditionally. Actually plastic windows exists. Though it may take time for most of us to adapt to it. While the reasons to consider ...
Fennekin's user avatar
  • 585
10 votes

Why are train brakes so complicated?

This answer addresses the following sentence: So I'd expect to see the brakes applied by a spring that is capable of stopping the wheels of a fully loaded car, and a single-acting cylinder that works ...
NMech's user avatar
  • 24.3k
10 votes

Why are train brakes so complicated?

You need to consider what happens if a hose bursts, and your spring-applied brake locks the wheels on one or more cars - how do you get that train back to the depot? There could be a manual brake ...
jayben's user avatar
  • 451
10 votes

Do I need a pressure relief/safety valve if my pump can't exceed the rated system pressure?

Not a plumbing engineer, but: What about thermal expansion? You reach a dead end, pump stops. Pumps often have a checkvalve that prevents backflow, so you have now created a pressurized container. ...
Thomas's user avatar
  • 109
8 votes

Why do car-seats have an expiration date?

It's a combination of 1, 3, 4, the product development cycle, and the nature of the product. 1 - Damage in materials is a cumulative process, the product of hundreds or thousands of little events (e....
DLS3141's user avatar
  • 2,145
7 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Another issue is that the coefficient of thermal expansion of many plastics is higher than that of window glass. Frames for plastic windows would have to be able to accommodate more expansion / ...
r1677301k's user avatar
7 votes

Why would a train automatically derail if a signal is passed at danger?

Why would a train automatically derail if a signal is passed at danger? When the cost of derailment is lower than the cost of a train collision, and the possibility of train collision exists, then a ...
Adam Davis's user avatar
  • 1,116
5 votes

Why would a train automatically derail if a signal is passed at danger?

A derailer is used rather than a device to trip the brakes because there is no guarantee there are any brakes to trip. These things are not intended to stop trains moving under power with their air ...
David42's user avatar
  • 153
5 votes
Accepted

CNC milling of large cutouts

I'm assuming that you are cutting on a base sheet of some sort in my answer, if not, please do. In all my shop applications I have found that double sided taping the product to the base sheet is ...
4LPH4NUM3R1C's user avatar
5 votes

Why not use fire-retardant plastics everywhere?

Fire retardant fillers are pretty cheap; often cheaper than the base plastic (Alumina Trihydrate for example). Like anything in engineering though, there are always exceptions and functional reasons ...
ericnutsch's user avatar
  • 8,146
5 votes

Is it dangerous for a child (or anyone) to bang away with a hammer and unscrew an old clothes washing machine?

the washing machine does not contain any energy storage capacitors which would retain a lethal charge for days after being unplugged. In addition, there's no pressure or vacuum chamber inside the ...
niels nielsen's user avatar
4 votes

Why would a train automatically derail if a signal is passed at danger?

The short answer is because it's cheaper and there's less loss of life. Let's look at a simple example. Now, I only really know about US trains, so forgive me if some of this doesn't translate ...
coteyr's user avatar
  • 141
4 votes

Why would a train automatically derail if a signal is passed at danger?

It should probably be noted that this incident occurred on a section of multiple track railway just outside a very large passenger terminus. Based on the photograph linked to above, I'd estimate the ...
origimbo's user avatar
  • 141
4 votes
Accepted

Replace mercury with silicone oil in diffusion pump

I did some internet searching and did not find anyone that had done a direct swap out. Granted, probably the majority of these replacements occurred before the existence of the internet ;-). As I am ...
ericnutsch's user avatar
  • 8,146
4 votes
Accepted

Tornado Safety: Basement or first floor interior room?

The Wikipedia page on Tornado Intensity has example pictures of damage. Your location has mostly EF1 and EF2 tornados historically (I'm assuming EF scale). EF1 EF2 EF3 Result Just looking at those ...
hazzey's user avatar
  • 10.7k
4 votes

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Hardness aside, weathering effects (from e.g. rainfall, snow, hail, temperature and moisture variations etcetera) and UV degradation are of course important to consider for windows. In general, glass ...
rsunds's user avatar
  • 41
4 votes
Accepted

How do you prevent ignition of the gas-air mixture before it reaches the burner nozzle?

Depending on fuel, a flame has a certain propagation speed - the speed with which the flame wanders through the medium. If the fuel - oxygen mixture moves faster through the pipe than the propagation ...
mart's user avatar
  • 4,771
4 votes

How to remove protective valve cap from CO2 cylinder?

Use two strap wrenches or an equivalent - one on the tank and one on the cap. You won't crush the tank :) If you need to make one, then a length of 4*2 and some old car seat belt bolted to one end ...
Solar Mike's user avatar
  • 15.8k
4 votes

Swing safety: maximum load of beam (supported at one end, free with load on the other)

I would recommend you have your boys wear a helmet while playing. Also cover the landing area with 8 inch deep bed of mulch or some soft material like foam sheets covered by a mat. With all due ...
kamran's user avatar
  • 22.4k
4 votes

Why would an oxygen concentrator warrant an "Oxygen in Use" warning for firefighters?

The zeolite in the concentrator is a hazardous material if the concentrator is damaged by fire. At high temperatures it decomposes into hazardous compounds. Zeolite dust released by damage is also ...
alephzero's user avatar
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