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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
  • 779
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
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
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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 ...
Dave Tweed's user avatar
  • 6,884
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
  • 15.7k
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
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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
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7 votes
Accepted

In a diesel engine, does more heat leave the engine through the tailpipe or the radiator?

They are very nearly equal for typical four-stroke non-turbo diesels under load. A turbo diesel under load should have slightly more radiator loss than exhaust loss. At the bottom is a link to the ...
Phil Sweet's user avatar
  • 4,755
7 votes

Alcohol as a working fluid?

Yes - for certain applications. Low-energy, low-temperature, small installations, possibly 'accessory' power where providing a bit of weak rotary power to some point of machinery would be difficult ...
SF.'s user avatar
  • 6,105
6 votes
Accepted

How friction between stator and rotor is dealt with in an electric engine/motor

... there's no space between the rotor and the stator. There is always an air gap between the rotor and stator. Iron has a permeability of about 1000 times that of air so the trick for maximum ...
Transistor's user avatar
  • 10.8k
6 votes

Why are bulldozers so slow?

You’d just need a lot of engine power and all the suspension, drivetrain (including tracks), brakes, safety equipment (seatbelts, airbags) etc. would have to be designed for the high speed. Just ...
Michael's user avatar
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5 votes
Accepted

Manual transmission: Why downshifting is less smooth than shifting up?

That's because when you upshift, you select a lower ratio, so your clutch speed drops. Since you took your foot of the gas, the engine rpm also dropped, and now the clutch and engine speed are close ...
Bart's user avatar
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5 votes

Why is soot produced in diesel exhaust, since diesel runs lean?

From the Wikipedia article: All diesel engines can be considered to be lean-burning with respect to the total volume, however the fuel and air is not well mixed before the combustion. Most of the ...
Chuck's user avatar
  • 3,565
5 votes

How many power strokes per rotation in a 3 cylinder engine?

A stroke consists of either one expansion, or one contraction. As such it corresponds to half of a rotation of the shaft. In a three cylinder engine, each cylinder will stroke with 2 strokes per ...
Rick's user avatar
  • 1,335
5 votes

Why doesn't the aircraft propel forward when on ground and the engine is running?

Brakes are used. And tyre wedges are also used. Turbo prop has the blades feathered to not produce any thrust. A jet is producing enough mass flow to run and little thrust.
Solar Mike's user avatar
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4 votes

Why do custom engines typically specify a type like "Ford" or "Chevy"?

There is no reason in principle why a custom engine builder couldn't cast a block themselves. Everything done by the level of automation in this process could by done by hand, given enough highly ...
alephzero's user avatar
  • 12.5k
4 votes

Why modern diesel engines have low compression ratio?

Diesel engines with turbos have a lower compression ratio. Also the compression ratio has been lowered generally to help reduce the nitrogen oxide emissions. The better fuel delivery control and spray ...
Solar Mike's user avatar
  • 15.7k
3 votes

In internal combustion engines, what determines when soft or hard gaskets are used?

Gaskets are selected based upon the mating surface materials, pressure, surface area, surface condition and what they are sealing. As far as I know, harder gaskets are used in harsher locations. But ...
Gwydionforge's user avatar
3 votes

What makes crosshead bearings hard to lubricate?

The crosshead bearing slides within a track and connects to the conrod and then to the crankshaft. In a vertically oriented engine the pressure on the bearing is always downwards, resulting in a ...
Donald Gibson's user avatar
3 votes

Effects of center of gravity very close to rear wheels of a car

One possible reason for placing the engine and most of the weight at the back of the car would be to improve rear wheel tire friction. This would be useful if the car has a rear-wheel drive, since the ...
BarbalatsDilemma's user avatar
3 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?

I never heard of pushing a car is 1st; have you tried it ? In the good old days when cars were not so reliable , I started more than a few in 3 rd ( of 3 speed ). Occasionally started one in second by ...
blacksmith37's user avatar
  • 6,134
3 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?

Having pushed many cars on many occasions, on snow as well as gravel and tarmacadam. I can categorically state; on gravel 3rd best nothing lower than 2nd, on snow 4th you can try 3rd and you may be ...
Barrie D Davey's user avatar
3 votes

Does the turboprop engine torque get transferred to the engine mount and ultimately aircraft when engine is active?

For every action there is an equal, but opposite, reaction. Never found a case that this is not true. Torque reaction on the P51 even caused uneven tire wear: https://www.aopa.org/news-and-media/all-...
Solar Mike's user avatar
  • 15.7k
3 votes
Accepted

Why is Scotch-Yoke mechanism not used for internal combustion reciprocating piston engines?

Making an engine using scotch-yoke mechanisms for all pistons on a multi-cylinder engine will increase the cost and add a lot of needless complexity and mass, especially rotating mass that won't ...
Solar Mike's user avatar
  • 15.7k
3 votes
Accepted

Throttle position as a function of engine torque and speed

why does the torque value at a specific rpm vary for different throttle positions This is the difference in acceleration when you fully open the throttle versus open it part-way. For a spark-...
Tiger Guy's user avatar
  • 6,871
3 votes

Effect of Earth's rotation on moving vehicles

The answer to the effects of Earth's rotation of moving vehicles: First, Earth doesn't rotate at a rate of 460 m/s. In fact, m/s is not the unit for the angular speed. It's like using Liters for mass. ...
Sina Atalay's user avatar
3 votes

Why are bulldozers so slow?

The objective of a bulldozer is to apply very large forces to very heavy loads of rock and soil. This requires a large engine combined with very low gearing mounted in a massive structure to generate ...
niels nielsen's user avatar
2 votes
Accepted

Why is soot produced in diesel exhaust, since diesel runs lean?

One important reason is that diesel fuel had a high molecular weight compared to gasoline this means that is is more difficult to disperse as it forms liquid droplets as opposed to vapour and even ...
Chris Johns's user avatar
  • 15.2k
2 votes
Accepted

Torque in different car gears?

The torque indicated by the car manufacturer is usually measured at the engine's output, without use of the gearbox. However it is still a good indicator of the car's global performance, but only if ...
MaximGi's user avatar
  • 318
2 votes

Inlet of an ICE

There are 2 ways to increase the airflow through a filter: bigger holes and more surface area. Bigger holes is usually not possible because that would defeat the purpose of the filter. The face mask ...
ratchet freak's user avatar

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