Hey everybody, welcome back to X-Men 5, the podcast where we take the questions you always want to ask and talk about them in a way that's easy to understand. We are your hosts, I'm Tim. Hey everyone, I'm Kevin. So Kevin, today we're talking about a topic that lots of five-year-olds love, and that is trucks.
So here's one of the most popular questions we get asked. Why do European trucks have an engine below the driver compartment compared to US trucks which have the engine in front of the driver? Well, that's a very observant five-year-old. And well, it is that way because of the way Europe and US regulate how long trucks are allowed to be.
So in Europe, they measure the entire length, including both truck and trailer, while the US is just the trailer. So in Europe, what they do to maximize cargo space and make the trailers as long as possible, they usually shorten the truck by putting the engines underneath the cab. And this is called a cabover. It can actually save like two meters of length this way.
While America did have cabovers before, but since the mid-1980s, restrictions were loosened a bit, so there's no more need to optimize the cab length anymore. I see. So it's purely regulation, and surely there are also practical reasons too. Well, regulation does usually come from practical needs.
So if you spend time in Europe, you will see just how small and narrow and generally space most trained cities in Europe are, for lots of historical reasons. And well, every centimeter counts on these narrow roads. Also in Europe, a truck transporting goods is quite likely to have to board a ferry at some point in its life. Now we're on a ferry boat, maximizing space is key to reducing costs.
However, in the US, it's pretty unlikely that a truck would ever be on a ferry boat. I see. So it's not so much about space and volume in the US. Maybe it's about weight.
And that leads me to my next question. In the US, you often see these weighing stations on US interstates. What are they used for? And are they still relevant today?
Oh yeah, I always notice those on road trips. Now, there are laws about maximum axle loads and generally vehicle loads for trucks on highways. And this is because of the amount of road wear a vehicle does increases dramatically with the axle weight. This is especially true when you're talking about roads up north in like colder climates, where there's freezing and thawing over the air.
So that's what they're checking for. Here's another interesting question. Why do trucks and actually many buses have this shh sound that you hear when they stop? Oh, so many fun questions today.
Well, large vehicles such as trucks and buses, actually they use compressed air to apply pressure to the braking pads that stop the vehicle, producing that shh noise. But the sound is made once the bus stops. So if the brakes are on while stopped, then surely they want to keep the air pressure and not release it, right? Oh, so there are actually two braking systems that work here.
First, there's the usual driving system brakes that use air to apply braking pressure and springs to release them. And secondly, there's the parking brakes, which apply pressure with springs and actually use air to release them. I see. Are these like the brake pedal and then the handbrake in the car?
Yeah, that's a pretty good analogy. So when the driver presses the brake pedal, compressed air is applied to the brakes, which is what makes the truck stop. And then when the driver releases the pedal after stopping, you know, even if they just release their foot partially, the air, it gets released under the truck making that shh sound. However, if the driver is going to be stationary for a while, they might apply the parking brake.
And the parking brake works the opposite of the brake pedal way. You know, it actually uses air pressure to release and springs to apply. So when the driver applies the parking brake, it releases the air from the park brake system. And this makes an even bigger shh noise than just releasing the brake pedal.
Thanks for explaining that. Now, you know how we started about the question about cab over trucks? Well, this question comes in particular from our listeners who have actual five-year-olds or young kids. Oh, could this be about the most famous truck of all, Optimus Prime and the whole Transformers line?
That's exactly correct. So Optimus Prime is a cab over truck with a flat front. Does this mean that Optimus Prime is, in fact, European? Okay, so just to explain the context really quickly, Optimus Prime is the leader of the Autobots, which is a faction of Transformers, which is both a TV show, movie, and toy line.
And basically, he's a white truck, which actually looks quite European, based on what we just discussed. But the answer to your question is actually no, because to be precise about it, Optimus Prime was originally based on a white Freightliner cab over semi-trailer truck. And Freightliner was an American company, and so also a very American truck at the time. So why the European design?
Well, remember we said American regulations were relaxed? Well, they only became relaxed in 1982. And at that point, Optimus Prime had already been invented as a Japanese toy that would become Optimus Prime. So Optimus Prime has Japanese roots as well as solid American credentials.
And to add to the story, the once American company Freightliner is actually now owned by Daimler, which is a European company. Okay, I'll just put this down as it's hard to say where Optimus Prime is truly from. Well, actually, so technically none of the above we just talked about. Technically, he is a Cybertronian.
That is, we should describe him as an extraterrestrial species of sentient, self-configuring, modular robotic life forms. Okay, I got it. Did you learn something new? If you did, send us an email.
We are at eli5podcasts at gmail.com. We love hearing from you, especially when you've got suggestions for us on future episodes. As always, thank you to the community at r slash at 7.5, and we will see you all next week.