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44 votes
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Why are engine blocks so robust apart from containing high pressure?

If you consider only the static forces then indeed the thickness might seem over-engineered. However, engine blocks are not statically loaded. They operate in the range of a few hundred to a few ...
NMech's user avatar
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44 votes

Why are bulldozers so slow?

I wonder why can't we engineer.. We CAN engineer a vehicle which is both fast, and has a lot of torque. (E.g. a tank, as you mentioned yourself) The reason why we don't do this for a bulldozer (I.e. &...
Chris_abc's user avatar
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40 votes
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Why do heavy trucks use air brakes?

Biggest advantage is that when connecting to trailers, there are no bleeding issues. Imagine having to connect hydraulic pipes and remove the air bubbles... As for the amount of air - the compressor ...
Solar Mike's user avatar
  • 15.9k
26 votes

Why are bulldozers so slow?

From memory, but pretty much realistic: a tank will use e.g. 1000 liters of diesel fuel just to move 100 km and will probably require a track maintenance afterwards. A truck with the same tank on its ...
fraxinus's user avatar
  • 499
17 votes

Copper is more conductive, so why use lead battery terminals?

Yes, copper is more conductive than lead, but that is not necessarily the primary criterion for selecting the connector material. For car batteries, making sure there's a good connection between the ...
Dave Tweed's user avatar
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15 votes

Is there a reason (in terms of the physics involved) why it is better to push start a car in 2nd gear rather than 1st?

It depends on the car. If it's a big displacement high performance engine, then you may not be able to get the rear wheels to turn unless you're in the highest gear. If it's got an itty bitty engine,...
TimWescott's user avatar
  • 2,682
15 votes

Why are engine blocks so robust apart from containing high pressure?

You need to consider that the complete engine block has to withstand the reciprocating forces generated by each of the pistons and con rods moving as well as the rotational forces from the rotating ...
Solar Mike's user avatar
  • 15.9k
15 votes

Why do heavy trucks use air brakes?

Several characteristics led to the adoption of air brakes. The primary one is reliability. A leak on a hydraulic brake system means the brakes don't work. A leak on air brake system means the ...
Tiger Guy's user avatar
  • 6,969
12 votes
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Why wont Petrol engine run on Acetylene?

There are certainly a few reasons why acetylene is not a very practical fuel for an IC engine. Perhaps the most important is that it is inherently unstable and tends to explode under pressure, this ...
Chris Johns's user avatar
  • 15.2k
12 votes

What is the purpose of grid-like details on engine blocks?

This pattern is to provide sufficient strength while minimising the mass of the block. These "webs" are designed to prevent any vibration, if the block wall was made thin and the full length and ...
Solar Mike's user avatar
  • 15.9k
12 votes

Why are engine blocks so robust apart from containing high pressure?

The vibration, loading, and fatigue aspects have already been addressed, but a wide range of operating temperatures is another factor. A typical consumer engine can be deployed in anything from say -...
brichins's user avatar
  • 221
9 votes

Copper is more conductive, so why use lead battery terminals?

A lead-acid battery has only lead and acid. If copper was used for the terminal posts galvanic corrosion would eat them. It is better to keep the same metal for the cell plates and the terminals. Also ...
ronald glen's user avatar
9 votes
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Is it true that four-wheel drive is less efficient and if so, why?

Simply put, power transmission is not free. Every time you have some energy over here, and you want to move it to over there, you are going to lose some of it in the process. In this case, if your ...
Daniel K's user avatar
  • 2,646
9 votes

Why do heavy trucks use air brakes?

"Power" brakes, like the ones you have in your car, use air pressure to assist your pedal effort. In passenger cars the air pressure is actually negative: it relies on intake manifold vacuum....
stretch's user avatar
  • 246
9 votes

When a car with an open differential turns, why does the inner wheel slow down and the outer wheel speed up?

TL;DR: The kinematic constraint imposes the redistribution of forces on the four wheels. This redistribution is permitted due to the car differential. IMHO it is easier understand this if you first ...
NMech's user avatar
  • 24.4k
8 votes

Are front wheel drive vehicles inherently flawed?

Do the math. Wheel slippage isn't a issue unless you are trying to accelerate exceptionally hard. In practice, front wheel drive cars usually have better accelerating traction because the load on ...
Olin Lathrop's user avatar
  • 11.4k
8 votes

Why do electric cars claim "instant torque?"

ICEs (internal combustion engines) take some time to ramp up their output torque. Various mechanical systems have to react before more mixture is injected into cylinders, and that then makes more ...
Olin Lathrop's user avatar
  • 11.4k
8 votes

Is it possible to build an efficient Electric Vehicle engine with minimal to no computing control systems?

Yes, it's possible, but electronics do it cheaper, lighter, and in a more sophisticated manner than what electro-mechanicals can do it. You can also tweak software to tune a basic design. With electro-...
Phil Sweet's user avatar
  • 4,765
8 votes

On a car with all-wheel drive, how does the engine provide the angled front wheels with power?

You could also include front-wheel drive in your question. It would be enlightening for you to look at what radio control rock crawlers do. It has much of the excess of a full-sized car stripped away. ...
DKNguyen's user avatar
  • 5,641
8 votes

Why are bulldozers so slow?

Because the tracks or tyres and suspension needed for sufficient ground contact when pushing, dozing or grading does not match the suspension etc needed for higher speed situations. Even the ...
Solar Mike's user avatar
  • 15.9k
8 votes

Why are bulldozers so slow?

They need to be heavy for traction, which makes them too heavy for speed. To have enough friction between ground and tracks, the machine needs to be very heavy. The Caterpillar D9 you mention weighs ...
jpa's user avatar
  • 1,953
7 votes
Accepted

Why can't energy be entirely recovered from a moving car's rotating wheels?

Get a small DC motor from a cheap toy or something and put a gear or a flywheel or something on the shaft to make it easy to spin with your fingers. You should find these in the toy as well. Ask your ...
ChP's user avatar
  • 623
7 votes

Is there a reason (in terms of the physics involved) why it is better to push start a car in 2nd gear rather than 1st?

A higher gear ratio means that less force is needed to turn over the engine by pushing the car. Aside from the issue of the tires slipping, humans are more likely to be able to maintain the speed of ...
alephzero's user avatar
  • 12.5k
7 votes
Accepted

Why excavators use Hydraulic motors for rolling or moving forward instead of diesel engine?

Yes, because many or most excavators can 360 rotate so getting a classic gearbox/ prop shaft drive to the wherls or tracks would be challenging. Then sorting the ability to do forwards with one side ...
Solar Mike's user avatar
  • 15.9k
7 votes
Accepted

Why does a newer car have a bigger engine and produce less power?

The main difference is the combustion cycle that is used. Presumably the Citroen uses the Otto cycle which is the most common for intenal combustion engines. The main benefit is that for the same ...
NMech's user avatar
  • 24.4k
6 votes

Why do these car headlights run on AC?

LEDs, especially high output ones are often run off pulsed DC, this is a convenient and efficient way to control current and thus brightness, especially in a vehicle electrical system where the ...
Chris Johns's user avatar
  • 15.2k
6 votes

Why isn't it possible to build a car moved by wind power?

The fundamental problem in this case is that the turbine in not powered by 'wind' as such but by the relative motion of the car through the air. This is not 'free' energy, because the turbine must ...
Chris Johns's user avatar
  • 15.2k
6 votes
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Reason of Using exactly 5 Wheel Studs per Wheel

On reason is that die cast (alloy wheels) generally have an odd number of spokes. This is because having directly opposed spokes causes problems with residual stress distribution as the casting cools ...
Chris Johns's user avatar
  • 15.2k
6 votes
Accepted

Why are car bodies not made of titanium?

The bulk price of titanium doesn't tell the whole story. A big chunk of the cost of titanium parts is down to the fact that it is significantly more costly to make things out of titanium than steel. ...
Chris Johns's user avatar
  • 15.2k
6 votes

Why don't car engine piston-rods (or similar parts) fail as often as other car parts?

The main reason from a designer's point of view is the consequence of a failure. Almost always, something like battery failure or a puncture doesn't cause any collateral damage - you just replace the ...
alephzero's user avatar
  • 12.5k

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