115
votes
Why do cars have mirrors for rear view rather than cameras?
This is another case of fancy new (SHINY!!!) technology being A Bad Idea(TM) . When you're driving, your eyes are focussed roughly at infinity, i.e. looking at objects more than 5 m away. When you ...
- 4,189
62
votes
Accepted
How was Volkswagen able to trick the lab pollution test?
After the 2014 ICCT report revealed that these light-duty passenger diesel vehicles were emitting too much NOx and US regulators confronted VW about the results, VW did some testing and proposed a ...
- 3,211
61
votes
Why do cars have mirrors for rear view rather than cameras?
We still use mirrors because:
A mirror is cheap, simple, passive technology that works. Pretty much the only failure mode is it breaking on impact. (Though I have had a center rearview mirror fall ...
- 711
44
votes
Accepted
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 ...
- 24.2k
43
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. &...
- 748
38
votes
Accepted
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 ...
- 15.3k
32
votes
Why do cars have mirrors for rear view rather than cameras?
The industry is already going down that path for the exact reasons you mentioned. There is an article that provides information about that.
In summary the main reasons why we don't have it yet are
...
- 1,734
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 ...
- 499
22
votes
Why do cars have mirrors for rear view rather than cameras?
Digital camera systems with LCD screens impose latency of at least a frame on the images. Fine for slow moving parking cameras, maybe a problem at speed. An object moving at 60mph shown through a ...
- 339
19
votes
Accepted
Why do cars turn by turning the front wheel?
If you were going to turn left 90 degrees, without turning the wheels, then you wind up dragging the wheels sideways while you turn. 16 seconds into this video shows exactly what I'm talking about.
...
- 3,575
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 ...
- 6,864
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,...
- 2,422
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 ...
- 15.3k
14
votes
Can the Sabatier reaction power a vehicle?
According to Wikipedia:
It [Sabatier reaction ] involves the reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures in the presence of a nickel ...
- 2,160
14
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 ...
- 6,248
12
votes
Accepted
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 ...
- 15.1k
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 ...
- 15.3k
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 -...
- 221
11
votes
Accepted
How much clearance does a car need when turning a corner?
To slightly generalize I'll reform the question slightly.
A ridged 2-D body (car) has a line $l$ that moves with it.
The car can be linearly transformed as long as the instantaneous center of ...
- 1,335
10
votes
Why do cars have mirrors for rear view rather than cameras?
Cameras are used as rear-view mirrors, simply not in mainstream passenger cars. For example, here's how rear-view is done in tramways:
Aside from improved wind resistance which you mentioned, cameras ...
- 394
9
votes
Accepted
Why does reducing the amount of emissions control improve the fuel economy of a car?
Not all of the pollutants come directly from the fuel. Some (e.g. NOx) come from the air itself, based on the combustion temperature in the cylinder. Running a cylinder at a higher temperature (by ...
- 6,864
9
votes
Accepted
What causes the sound coming from electrical vehicles?
Correct, coil noise is generated in the windings of the motor because of Pulse Width Modulation (PWM) driving current. Different frequencies of modulation cause corresponding sound frequencies (may ...
- 7,794
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 ...
- 91
9
votes
Accepted
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 ...
- 2,646
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 ...
- 24.2k
8
votes
Are small car engines designed to tolerate a higher duty cycle than large car engines?
The primary issue (ignoring secondary issues like internal wear) is whether or not the engine can get rid of the waste heat.
Assuming that all engines for a given fuel have roughly the same overall ...
- 6,864
8
votes
How many power strokes per rotation in a 3 cylinder engine?
Each cylinder produces a power stroke for every (2-stroke engine) or every other (4-stroke engine) rotation of the crankshaft.
A 3-cylinder, 4-stroke engine will produce 3 power strokes for every 2 ...
- 6,864
8
votes
Why do cars have mirrors for rear view rather than cameras?
All the points mentioned by others are factors, but the true answer (i believe) is:
Why cameras (and obviously displays) are not used instead of
mirrors?
The law (regulations on street ...
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 ...
- 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 ...
- 11.4k
Only top scored, non community-wiki answers of a minimum length are eligible