Let us now talk about Torque, the single terminology that
separates engineers and physicists from the rest of the human race. Some people
have heard about it, others read about it, and the vast majority of people
simply don’t care about it. To be fair, torque is not actually that important
to the point where you have to actually choose between knowing what it is and
dying. Spending money on books about torque and time to read them all will not
give any considerable change to your life either. It is just like knowing that
the Earth is round, rotating on an imaginary axis, and orbiting the solar
system center mass; will knowing those facts change your life? It probably will
not.
The principal of torque can be seen in various objects or
activities in everyday situations such as opening a bottle cap, hinged doors, playing
seesaws, wrenches, as well as bolts and nuts. Despite the common applications,
it is highly unlikely that you are aware of it. No one counts how many
pound-feet of torque are necessary to open a lemonade bottle or the basement
doors. It also does not help that your plumber never explained to you about the
torque he generated while he was in the toilet – to loosen the rusty bolt and
nut form the drain pipe, of course.
Torque is most prominently used in automobile and associated
with cars or vehicles in general, measured in either Nm (Newton meter) or lb-ft
(pound feet). Among the common examples, the single biggest chance that torque
is mentioned during a conversation between two people during lunch break is when
they talk about cars. By the time one of them mentions it, they realize that
they cannot afford the cars they talked about and so they go back to work.
While torque is not as popular as horsepower or turbocharger and supercharger, it
actually is one thing that makes them all work. You can think of horsepower as
lamps, turbocharger as TV, and supercharger as a computer, but torque is the
electricity puts them to function.
While all average car enthusiasts realize that torque and
horsepower play major roles in determining performance, many (if not most) of
them do not exactly how those things work. Some probably have good ideas in
their heads, but they don’t know how to tell it properly; in other words, they
just pretend to understand.
Torque
Simplest definition of torque is engine rotational force,
which gives no comprehensible meaning to the average mind. Remember that any
car starts the acceleration and reaches whatever top speed allowed by road
signs from zero. Your car does not start at 60 miles per hour or any speed for
that matter; it starts from zero, and this is what torque is for. The initial
energy that moves your car forward originates from the engine combustion
chamber; fuels and oxygen are delivered to the chamber where they collide and
explode. Forces generated from the explosion move a group of pistons connected
to the crankshaft. The rotating crankshaft is where torque develops. Once the
crankshaft rotates, the energy is forwarded to multiple components including
flywheel and transmission before it actually reaches the wheels.
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| If you look hard enough there is torque somewhere in there, maybe |
Remember that torque number simply tells you how much
rotating force is at work inside the engine. Higher rotating force generally
means faster acceleration, but it depends on how much the car weighs as well. You
can also say that torque is the force required to move the entire car. Imagine
a plumber’s wrench that clamps to a rusty toilet pipe; assuming the wrench is
about 1.5 feet long and he needs to apply 100 pounds of torque to start
loosening the pipe, the total amount of torque he generates is 150 pound-feet
(100 pounds x 1.5 feet). Double the torque and the plumber probably will twist
the rusty pipe as if it is nothing and burst some damp ugliness all of a sudden
into the air. Apply that analogy to a car, and you get the idea of how torque
works.
Horsepower
Another way to put it, torque is the potential energy of a
car used for rotating the wheels – and potential is what it’s all about. Torque
is the base number of work for moving the car, whereas horsepower is the rate
at which the car is doing the work. Our understanding of horsepower is a little
bit ancient. James Watt and Mathew Boulton standardized horsepower as the
amount of power required to perform 33,000 foot-pounds (not to be confused with
pound feet) of work in one minute in 1783.
Note:
- Foot-pound (ft/lb): the traditional English unit of work indicating the amount of work possibly done by one pound of force for one foot distance.
- Pound-feet (lb-ft): the traditional English unit of torque that indicates the tendency or potential energy of a force to generate rotation.
James Watt used an actual brewery horse to measure that. Now
whether or not the fact that the horse was working in a brewery played a role
in the number is anybody’s guess. Maybe a winery horse was more relaxed and therefore
it generated less power, for example. Centuries later we still use the same
equation to measure the horsepower of supercars.
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| Use one more wrench and it is just going to be a waste of torque |
If torque starts a car movement from a point of standstill,
horsepower is what keeps it moving to maintain speed. You want torque to get
the car start moving quickly such as in the start line of a race or more
realistically in a parking lot because you don’t want to rev-up the engine only
to move the car as far as 15 feet. On the other hand when the vehicle is going,
you want low torque and more horsepower. Of course it is not that simple
because you also have to calculate downforce, too. Lack of downforce and more
torque leads to excessive wheel-spin which does not always translate to how
fast the car is going. Sure the wheel is rotating unbelievably fast, but the
wheels have to grab and stick to the road and generate traction for movement,
so it helps if you are slightly overweight.