Inflight smoking is forbidden not just for the comfort of non-smokers – there are actually technical reasons behind it

Inflight smoking is forbidden not just for the comfort of non-smokers – there are actually technical reasons behind it

Several decades ago flying was much less glamorous than it is now. Sure, people used to dress up for the journey, but everyone was smoking. Now we can appreciate fresh, even if a little bit dry, air in airplane cabins. But did you know that smoking in airplanes was prohibited not just to make flying more comfortable for non-smokers?

In fact, smokers in the airplanes didn’t bother people too much. They were typically seated at the rear of the cabin, where they could smoke without disturbing non-smoking passengers. Because air inside of an airplane is flowing from the front to the back smoke was evacuated pretty effectively, without filling entire cabin with unpleasant smell. When in 1988 smoking was banned from flights that are shorter than 2 hours, airlines were actually worried that people are going to fly less because of this decision. And now if you do try to light up a cigarette, you are facing a huge fine and/or ban from flying that airline again. Why is that?

Back in a day, you could buy cigarettes from flight attendances. That contributed to revenues of the airlines, which is why they were against in-flight smoking ban. Tobacco companies were also vocal about their disapproval or such decision. And, of course, smokers felt discriminated, especially when the ban included pretty much all longer flights. However, not airlines are very happy that no one is smoking in the airplane.

Smoking in planes was completely normal not so long ago. (Estormiz, Wikimedia)

The truth is that smoking costs money not only to people buying cigarettes, but also to airlines, because it increases the cost of plane maintenance. Smokers unintentionally drop ashes on the carpet, they fill up the ashtrays, sometimes damage the seats and so on. Cleaning airplanes that have been smoked in is more time consuming. Also, remember we said air flows from front to back?

The airplane cabin, as weird as it may seem, is not a completely sealed pressure vessel – it does vent out. The air pressure inside of the cabin is equal to the one at altitude of around 2-2.4 km. Air is constantly pumped into the cabin and so, some it has to be vented out through the main cabin outflow valve. The opening and closing of this valve is what controls the pressure inside. However, tobacco smoke can make this mechanism sticky. Thick sticky tar used settle all over the main cabin outflow valve. Sometimes it became so sticky that the system struggled to open it.

Now smoking in the airplane could result in a huge fine and even a ban to fly that airline ever again. (Kashif Mardani, Wikimedia(CC BY 2.0)

Furthermore, tobacco tar used to cover all the airways from the cabin, which were a significant hassle to clean during maintenance. Finally, smoking could have posed a safety threat as well, if the tar glued the oxygen mask compartment doors too. Pilots used to smoke back in the day as well, but that wasn’t doing any good for electronics.

And so now smoking in most airlines is forbidden. However, ashtrays in bathrooms still exists. They are there just in case someone breaks the rules. If there were no ashtrays and someone decided to smoke, they would probably put their cigarettes out on the toilet or in the sink, which someone would have to clean up later.

What is that black frame around the car windshield? What function does it serve?

What is that black frame around the car windshield? What function does it serve?

Pretty much every car on the road has a black frame, baked into the glass of the windscreen. It is around 3-4 centimetres wide and usually has a dotted pattern right next to it. While it may seem like just a strange design feature, this frame, called the frit, actually serves a purpose.

Even if you crack your original windscreen and get it replaces, they are going to install glass with a frit – it is simply unavoidable. Actually, its function has a lot to do with how windscreens are installed. Back in a day when windscreens were held in place with a rubber frame, frits didn’t exist. But now they are glued in and that is why there is a black frame baked into your windscreen.

And we do mean it when we sake “baked in”, because the frit is nothing else but ceramic enamel, which is applied during the manufacturing process, before the laminated glass is heat treated. Glass is very hard and smooth material, which is great, but because of that it glue doesn’t stick to it very well. That is one of the reasons why ceramic is baked into the perimeter of the windshield – glue sticks better to ceramic than it does to glass.

This black frame around the windscreen is actually baked in and is used to cover and protect the glue.(Matti Blume, Wikimedia (CC BY-SA 4.0)

Furthermore, black ceramic enamel hides the glue from the plain sight. Glue is ugly and so it makes sense to cover it with something. Glue also needs protection against the UV rays, because they can make glue hard and brittle, which is not great, having in mind all the vibrations it has to withstand. Eventually hardened glue would simply let go in some points, probably causing the windshield to crack. That wide frit band helps keeping the glue flexible and strong.

And finally, what are those dots for? The answer is simple – for the looks. They break the hard contour of the enamel frame, allowing it to transition smoother into the clear glass. That dotted pattern does not serve any practical function. However, some manufacturers use it to hide some Easter eggs in their cars. For example, you can find a little Willys MB on the windshield of the JEEP Renegade. This little detail is formed from the same black ceramic enamel and is also baked into the laminated glass.

JEEP uses its frit to hide a little Easter egg – a silhouette of the brand’s first car Willys MB. (JEEP’s image )

By the way, you can also find the frit line around the side windows of the bus as well and there it serves the exact same purpose of hiding the glue.

Why this funny-looking tractor has only three wheels? (Video)

Why this funny-looking tractor has only three wheels? (Video)

Most tractors have four wheels. That is a standard configuration and deviations from it can only be found in history. However, there are exceptions – the Challenger Terra Gator TG 8333 is a modern machine and yet it only has three wheels. Why? What does it do?

Challenger Terra Gator TG 8333 is a self-propelled nutrient application vehicle. In other words, it spread fertilizer on the fields and does that very efficiently just because of how huge it is. It has telemetry equipment, adaptive suspension, GPS-controlled autopilot and loads of other technology.

The tractor in the picture below is spreading hard organic fertilizer- manure, but some other modifications can be used to spray liquid fertilizers. In fact, one three-wheeled Terra Gator can hold as much as 16 cubic meters of liquid fertilizer – that is more than 16 tons of weight.

Each of the three wheels is in its own track and thus the ground get driven over only once. (joost j. bakker, Wikimedia (CC BY 2.0)

Despite the massive size of this Terra Gator, it is supposed to be easily controlled. After climbing a set of stairs, the operator will find a comfortable workplace with a supportive seat, touchscreen, climate control and other equipment. But we are not selling you this tractor – we are more interested, why it has only three wheels.

All three wheels of the Challenger Terra Gator TG 8333 are the same size and all are driven. (werktuigendagen, Wikimedia (CC BY-SA 2.0)

The reason why Challenger Terra Gator TG 8333 has three wheels is weight distribution. Farmers do not want to compact the soil, especially when they are ready for fertilizing. It is harder for crops to grow in a compacted ground and heavy equipment squeezes out the air from the dirt, essentially reducing the harvest. Four-wheeled tractors may have a better weight distribution, but the rear wheels are following the front ones and, therefore, dirt that gets under the wheels gets driven over twice. It is also the reason why Challenger Terra Gator TG 8333 has such wide tires – they spread the weight of the machine over a bigger area.

Challenger Terra Gator TG 8333 at work


Other manufacturers apply different solutions to solve the issue of compacting the soil. Some use narrower front axles, while other fertilizers employ dual wheel arrangements. And then there are farmers who simply use lighter machines to not compact the ground too much.

Interestingly, Challenger Terra Gator TG 8333 is all-wheel-drive – all three wheels are driven. The front wheel, used for steering, is powered hydrostatically. Three-wheel configuration also allows for a better manoeuvrability – the front wheel can be turned by 75 degrees – it would be difficult to achieve that having two front wheels.

Why modern cars have so much plastic under the bonnet? We want to see the engine!

Why modern cars have so much plastic under the bonnet? We want to see the engine!

There is one thing you will not see under the bonnet of a modern car – it’s the engine. Nowadays, it is always hidden under several layers of plastic, moulded to look like some mechanical parts. They don’t even look good and you have to dig through them if you want to do any maintenance or repair work. But why every single car has these plastic engine covers? Why do car manufacturers bother to spend extra time and money to make them?

Not so long ago car engines were designed to be easily accessible and to look good. In the beginning of the previous century car manufacturers actually worked hard to make their engines pretty. They chose different metals, neatly organized fuel lines and wires and painted various parts different colours. All of that was expensive and time consuming, but such manufacturers as Packard, Daimler, Duesenberg and others did it anyway. Even Ferrari was always praised for how well its engines were dressed and how beautiful it looked inside and out, but now it is also falling under the plastic trend. But what changed?

Well, a lot of things. Back when Packard was one of the top premium brands, people actually admired engines. The internal combustion engine was the cutting edge of technology and not that many people could afford to own one. Nowadays cars a mundane and boring – everyone has one and no one wants to look at the engine. We, car enthusiasts, still do, but to be honest we don’t buy that many cars. And so manufacturers resorted to the function-over-form mentality, saving cost in the process. Investing into the looks under the bonnet is not a priority anyway, because no one buys the car just because it has a beautiful engine bay.

The engine of the 1910 Packard. (David Berry, Wikimedia(CC BY 2.0)

A plastic engine cover hides unsightly rat’s nest of wires and fuel lines, while making them still quite easily accessible. A nicely dressed engine bay typically means that some components can be hard to reach for repair. When you have a big piece of plastic hiding everything, you don’t have to worry about the looks – it is the cheapest way to keep the engine bay looking tidy. This is equivalent to cleaning the mess off of your desk straight into the drawer – out of sight, out of mind.

Ferrari used to be famous for its well-dressed engines. (Sfoskett, Wikimedia(CC BY 2.5)

However, plastic is not that bad. Sure, metal looks nicer, but it is easier to control the quality of the plastic. It also doesn’t add too much weight on top of the engine, allowing for a lower centre of gravity. Finally, plastic engine covers can be heat-resistant and absorb vibrations, making the sound of the engine just that little bit quieter.

Even luxury car manufacturers are hiding their engines under some cheap plastic covers. (Autoviva, Wikimedia(CC BY 2.0)

And so, plastic is here to stay. Even luxury car manufacturers are hiding their engines under several layers of plastic. And we cannot blame them. Covers do make the engine bay look clean and tidy, they are light, heat resistant and cheap to make. In fact, it is likely that in the future engines are going to be tucked away even more and not accessible without specialized equipment.


Why semi-trucks are called like that? What is so “semi” about them?

Why semi-trucks are called like that? What is so “semi” about them?

We use words without paying much attention to them. For example, words “semi-truck” are used commonly, but how many people know what that means? What is “semi” about these machines? There are actually two possible explanations.

In US and some other countries semi-trucks are simply referred to as Semi’s. It is a name everyone understands and once you mention a semi-truck everyone has an image in their heads of an articulated vehicle, consisting of a tractor unit and a trailer. Actually, the trailer is part of the story why semi-trucks are called like that.

Semi-trucks are, most of the time, hauling semi-trailers. A simple trailer is a wheeled platform, which can stand on its own on its wheels without any support. Meanwhile semi-trailers only have wheels at one end of the platform. The other end relies on the chassis of the semi-truck for support when driving. It cannot stand by itself on its wheels – it needs extendable legs or some other type of support structure. Semi-trailers cannot be hauled by anything else – they need an appropriate semi-truck to move. Even if you took the most powerful agricultural tractor, you could not safely pull a semi-trailer, because the front of it doesn’t have wheels and needs a chassis to rest on when travelling.

Semi-trucks consist of a tractor unit and a semi-trailer. Image credit: PRA via Wikimedia(CC BY 2.5)

But that is just a part of the explanation. Semi-truck is a combination of a semi-trailer and a tractor unit. Not that difficult to understand and it totally makes sense. But there is another explanation for where did this name come from.

The hitch mechanism at the back of the semi-truck is commonly called a “fifth wheel”. There are two most common types of fifth-wheels: semi-oscillating and fully-oscillating. Most semi-trucks feature a semi-oscillating hitch (turntable hitch or fifth wheel – whatever you want to call it). It means that the hitch mechanism is not entirely rigid – it tilts slightly from front to back. Imagine that the rear of the semi-trailer gets a little bouncy and starts moving up and down. The fifth-wheel will accommodate that movement, making the entire truck more stable. But if the trailer is tilting sideways, the semi-oscillating hitch will not move with it – a semi-oscillating hitch does not tilt from side to side. It is not usually a problem, though, because semi-trailers typically have enough flexibility in their chassis to absorb lateral movement without disturbing the balance of the tractor unit.

Logging trucks sometimes use fully-oscillating hitches. Image credit: ChattOconeeNF via Wikimedia(CC BY 2.0)

However, in some situations a fully-oscillating hitch has to be used. For example, in forestry semi-trucks. Because the terrain is so uneven, semi-trailers get rocked quite a lot. A fully-oscillating hitch tilts from side to side and thus allows for more movement in the trailer without disturbing the truck. This is also beneficial when the semi-trailer is very rigid (for example, when it is a tanker). However, fully-oscillating fifth-wheels are more complex, more expensive and typically unnecessary, which makes them pretty rare. That could be why semi-truck name stuck.

The reason why semi-trucks are called this name is probably combination of both of these theories. You should remember that a typical semi-truck is an articulated vehicle, consisting of a tractor unit and a semi-trailer, connected through a semi-oscillating hitch.

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