agurk

Joined 9 years ago

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968
Submissions
227
Member since
Sep 14
Been lurking daily since 2009. Finally felt like time to create an account.
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Recent submissions

Comment · 2 months ago
During the ongoing redevelopment of Belgrade airport I did find myself with a short connection there and unable to find a departure board. I checked the airport website, but it only had the flight names and not gates!

Beginning to get worried and with no-one to talk to in the construction site of an airport I discovered that I needed to rotate my phone and then the extra columns appeared on their website. Yes I had tried scrolling and zooming, but in portrait it wouldn't actually render outside of the visible width.

Comment · 2 months ago
Comment · 2 months ago
The Flag of Bosnia and Herzegovina has a triangle on it that is meant to represent the shape of the country (roughly).
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Comment · 1 year ago
On all the fuel injected engines I have owned there is a physical cable that controls the position of the throttle plate. There is an airflow mass sensor the other side of the plate to measure the amount of air and therefore how much fuel needs to be injected. So interestingly in these sort of engines you're really just controlling airflow to the engine rather than fuel/air mix like on one with a carburettor.

More modern engines have electronically controlled throttle plates, and this is definitely somewhere you could do something clever like you suggest - cutting fuel flow but also maximising airflow when there is zero throttle input.

I assume engine braking is generally considered a beneficial thing by manufacturers, but it could be fun to be able to customise the amount. Or do something like have the braking come on gently at first then harder. Maybe even try and have a linear or flat response curve vs. engine rpm.

Comment · 1 year ago
If it takes energy to compress the air in the cylinder - doesn't it also release most of that energy when that compressed air is expanded on the subsequent stroke?

If you release the compressed air without pushing the cylinder down you would lose that energy, but you would need a extra device to do so (by lifting a valve at the right time). This option does exist for large vehicles like trucks as a compression release engine brake [0], but this isn't something you'd have on a family car.

In a petrol engine you always want the same ratio of petrol to air in the mix that is taken into a cylinder. As you want to vary the amount of fuel, and therefore power developed, you have to be able to therefore limit the amount of air that is sucked in. Otherwise the engine would always run at full power.

There is a mechanical restrictor called a throttle plate that lives inside the throttle body that restricts how much air the cylinder can pull in (and therefore how much fuel is injected to get the same fuel/air mix). This is controlled by the throttle. When you are coasting, this plate is in its most closed position. This creates significant resistance on the intake stroke, and is where the majority of energy is lost during engine braking. This is also known as a pumping loss.

Diesels always intake the same amount of air, so they can compress it enough to autoignite the fuel. They vary the amount of fuel injected to the same volume of air. This means no throttle body or plate, so unless an extra exhaust restrictor has been added there is minimal engine braking on a diesel engine.

[0] https://en.wikipedia.org/wiki/Compression_release_engine_bra...

Comment · 1 year ago
Curiously I have the opposite problem with Too Good To Go - they never give me notifications of available things I might be interested in, even though I've set that I want them.

This is on Android though, so perhaps an ecosystem difference?

Comment · 1 year ago
Comment · 1 year ago
You are absolutely correct about autorotation and helicopters not falling out of the sky. There is one nuance that the rotor blades still need to be able to rotate for this, and a failed gearbox can prevent that. Anecdotally that feels like the most common cause when I read about another crash in the North Sea.
Comment · 1 year ago
Not all boots are made the same though. I had some bad luck with a pair of veldtschoen welted boots from the English firm Crockett and Jones in a custom leather. The commando sole split twice at the toe, which they repaired, but after less than five years of wear the lining at the heel had worn through.

I took them in to be rebuilt, but after inspection they said the stiffener had come loose, and nothing could be done. Here have your expensive and now broken boots back.

I'd assumed when I got them I'd be wearing them for decades, and at least a few rebuilds. Maybe there was something wrong with that specific pair, but I did have a goodyear welted sole randomly detach from a pair of six month old city shoes from the same firm. And yes I had been looking after my shoes (frequent cleaning and polishing, always using shoe trees, skipping days between wears, etc).

When I had a pair of Church's fall apart I put that down to them no-longer being a quality brand, but now I don't think you can guarantee a long life just as the shoe was expensive and from a reputable brand. I have many shoes that have lasted better (and now since covid I don't wear polished shoes daily), but that does sometimes feel like luck of the draw.

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