How to calculate torque

The moment of force is the physical quantity of the rotation of an object. It can be divided into moment of force to axis and moment of force to point. That is: M = lxf. Where l is the distance vector from the axis of rotation to the point of force and F is the vector force; The moment is also a vector

the moment of a force on an axis is the physical quantity that the force acts on an object to rotate about an axis, and its magnitude is equal to the proct of the component of the force on the plane perpendicular to the axis and the vertical distance from the line of action of the component to the axis. The moment of a force to a point is the physical quantity of the rotation action of a force to an object around a certain point, which is equal to the vector proct of the position vector of the force acting point and the force vector

extended data:

Properties of moment:

1. The moment of force F to point O is not only determined by the force, but also related to the position of moment center. The moment varies with the position of the moment center

when an object is in static equilibrium, the static force is zero and the net moment to any point is zero. Moment is the derivative of angular momentum with time, just as force is the derivative of momentum with time. The angular momentum of a rigid body is the moment of inertia times the angular velocity

In physics, torque is the size of torque, equal to the proct of force and arm of force. The international unit is nm. In addition, we can see such torque units as KGM and LB ft. because g = mg, when g = 9.8, 1kg = 9.8N, 1kgm = 9.8nm, and LB ft is the torque unit of British system, 1lb = 0.4536kg; 1ft = 0.3048m, it can be calculated that 1lb ft = 0.13826kgm. In people's daily expression, torque is often called torque (in physics, these are two different concepts). Now let's take an example: the torque of the 8th generation Civic 1.8 is 173 5Nm@4300rpm It means that the output torque of the engine at 4300 rpm is 173.5nm. How can the 173.5n power make a car with more than 1 ton run? In fact, the torque proced by the engine has to be amplified (at the cost of recing the speed at the same time), which depends on the gearbox, final drive and tires. The torque released by the engine is first amplified by the gearbox for "adjustable" torque (or reced when it exceeds the specific gear) and then transmitted to the final drive (tail teeth) for further amplification (at the same time, the speed is further reced). Finally, the driving force is released through the tires. For example, if the first gear ratio of a car is 3, the tail tooth ratio is 4, the tire radius is 0.3m, and the original torque is 200nm, the final torque on the axle becomes 200 × three × 4 = 2400nm (assuming the transmission efficiency is 100%). After dividing by the tire radius of 0.3m, the friction part between the tire and the ground has a driving force of 2400nm / 0.3m = 8000n, which is enough to drive the car
when it comes to mechanical efficiency, every gear transmission will proce a loss of power. The mechanical efficiency of manual transmission is about 95%, that of automatic transmission is about 88%, and that of universal joint of transmission shaft is about 98%. Overall, the driving force of the vehicle can be calculated by the following formula:
torque × Gear ratio of gearbox × Final gear ratio × Mechanical efficiency
driving force = ---, It is suitable for vehicles with large load. The cylinder with large diameter and short stroke pays more attention to the output of power, and the speed is usually higher, which is suitable for fast running vehicles. In short: power is proportional to torque × Speed
Add: why can engine power be calculated from torque
we know that power P = work W ÷ Time t work w = force F × So, P = F × s/t=F × Velocity V
here V is the linear velocity, and in the engine, the linear velocity of the crankshaft = the angular velocity of the crankshaft ω× The radius of crankshaft R is substituted into the above formula to get: power P = force F × Radius r × angular velocity ω And force F × Radius r = torque
it is concluded that power P = torque × angular velocity ω Therefore, the engine power can be calculated from the torque and speed
the unit of angular velocity is radian / S. in radian system, 180 degrees, torque and power are the important indicators to characterize the engine power performance
the torque output by the engine through the flywheel is called effective torque, expressed in te, and the unit is n · M. The effective torque is balanced with the resistance torque exerted on the engine crankshaft. The output power of the engine through the flywheel is called the efficiency, expressed by PE, and the unit is kW. It is equal to the proct of effective torque and crankshaft angular velocity
the effective power of engine can be measured by bench test, that is, the effective torque and crankshaft angular velocity can be measured by dynamometer, and then the effective power of starting motor can be calculated by using the following formula
PE = te · (2 Π· n / 60) / 1000 = te · n / 9550 (kw)
where te -- effective torque, n · Mn -- engine speed, R / min
the maximum value of effective torque is called maximum torque, and the maximum value of effective power is called maximum power
when a certain model is introced in newspapers, the torque and power in its technical parameters are usually the maximum torque and maximum power. The power and corresponding speed indicated on the engine nameplate are called rated power and rated speed, and the rated power is generally less than the maximum power. According to the provisions of automobile engine reliability test method, automobile engine should be able to run continuously for 300-1000h under rated conditions
as for the meaning of torque and power, generally speaking, torque is like the momentum of a hundred meter runner who squats at the starting point, is ready to go, and is ready to rush forward; And power is the ability to maintain this momentum and run faster and faster all the way to the end. Increasing the displacement of the engine can increase te and PE. In order to increase the engine displacement, the number of cylinders can be increased (such as changing 3 cylinders into 4 cylinders), or the volume of unit cylinder can be increased (such as increasing the inner diameter of cylinder)< Second, correctly understand the relationship between "torque" and "power" of the engine.
in short, the torque of the engine represents the amount of oil that can be absorbed by the cylinder in one breath, which will increase with the increase of throttle opening and engine speed, but it will not increase all the time, and it will reach the peak at a certain speed, This is what people usually call the maximum torque. If the engine speed increases again, it will graally decrease. This is the characteristic of gasoline engine and other internal combustion engines in terms of torque, and it is also the most unsatisfactory place. Power is equal to the torque times the speed, which represents the amount of oil that can be absorbed by the engine in unit time. Therefore, when the engine speed graally rises to the maximum torque point, the amount of oil absorbed in each breath and the number of suction times per unit time are increasing, so the power has been rising; When the speed exceeds the maximum torque point, although the amount of oil absorbed by each breath decreases, it increases to the maximum power point e to the small decrease and the increase of suction times; When the rotating speed exceeds the maximum power point, the decrease of the amount of oil absorbed in each breath is greater than the increase of the number of suction, so the power begins to decrease
thirdly, how to compare the advantages and disadvantages of different engines or the enhancement degree
the engine power performance indexes te and PE required by the automobile are obtained at a certain speed. Different vehicles have different requirements, different speeds (for example, trucks and cars have different speeds) and different engine speeds. Therefore, engines for different purposes have different speeds even when their effective power is equal. On the contrary, engines with equal power can not meet the requirements of all models, It is also necessary to consider the power and torque at the same time to see the corresponding speed, so as to fully see whether the engine's dynamic performance indicators te and PE meet the requirements< However, TE and PE can not be directly used to evaluate the advantages and disadvantages of engines with different displacement, that is to say, the engine with high power and torque is not good or the engine with high strength, but the power and torque per unit cylinder working volume
TL and PL are the torque and power per unit cylinder working volume. Only by using these two indicators can we compare the advantages and disadvantages of different engines or the degree of enhancement
the range of TL and PL of automobile engine:
gasoline engine: TL = 600kpa-1000kpa, PL = 22KW / l-55kw / L
diesel engine: TL = 600kpa-900kpa, PL = 11kw / l-26kw / L
under rated working conditions, the power generated by the working volume of engine per liter cylinder is called liter power
PL = PE / (VH · I) (kW / L) where: VH is the working volume of cylinder (L) I is the number of cylinders
The liter power indicates the utilization rate of working volume of unit cylinder. The larger PL is, the greater the power of working volume of unit cylinder is. When the engine power is constant, the larger PL is, the smaller the engine is and the smaller the material quality is
there are four ways to increase the power up:
(1) increasing the amount of charge requires air for fuel combustion, and it is more difficult for air to enter the cylinder than fuel. Using supercharging technology or improving the ventilation process (such as recing the intake resistance) can increase the inflation rate
(2) improve the quality of mixing gas and combustion. Under a certain amount of air, the air and oil are mixed evenly, the combustion is sufficient, and the heat supply per unit cylinder volume is increased
(3) only by improving the mechanical efficiency and recing the mechanical loss can the effective power output be increased. Recing the mechanical loss is mainly to rece the friction loss of each friction pair, followed by recing the power consumption and pumping loss of auxiliary mechanism
(4) properly increasing the speed is mainly to increase the frequency of work (or inflation), that is, to increase the amount of inflation per unit time. However, in addition to the mechanical strength, the increase of engine speed will rece the charge per cycle, increase the mechanical loss, and make the combustion process difficult to organize. That is to say, the increase of engine speed will rece the PE, so the increase of engine speed should be moderate

Torque:

torque is a special kind of torque that makes an object rotate. Engine torque refers to the engine torque output from the crankshaft end. To explain what you don't understand, to put it bluntly, it's the force you add multiplied by the distance from the force point to the axis you twist, so the torque w = FXL. Here, the unit of F is cattle. So force F = torque / L< br />