We use the term speed in everyday use, whether it is how fast we can complete a task or how quickly we need to get from one location to another. The very notion of speed is the magnitude of the change in position of a particular object. It scalars quantity and is usually expressed in meters per second or km/h. Our CalCon calculator measures the piston speed, representing the average piston speed. In this article, you can learn more about piston speed, calculating, and using a measuring calculator.
What is piston speed: average piston speed?
Pistons are a type of cylinder used in piston engines. You can spot them right at the top of the machine. Their work puts pressure on the rods that move up and down, which leads to engine operation. A piston rod joins a piston to the crosshead. The rod allows power that transmits from a controlled explosion in the cylinder to the crankshaft.
Many well-known engine designers pay a lot of attention to the speed of the pistons when projecting a new type of engine for the first time. According to particular essential performance for engine operation in the automotive sector, determining piston speed is critical in deciding fuel mileage. The car must have tremendous power to achieve the lowest possible fuel consumption.
The piston’s speed is also critical components for the engine’s performance. It measure refers to the speed of the pistons when moving up and down in the cylinder.
The piston’s work has two stopping moments:
- the top dead center (TDC), and
- the bottom dead center (BDC).
After reaching both moments, the speed constantly changes, and one cycle of engine operation is created. The most common units of measurement for expressing piston speed, also known as average piston speed, are feet per minute or meters per second.
How to calculate piston speed?
After clarifying the definition of piston speed, you need to determine how to calculate it. You can calculate piston speed with the value of the average piston speed based on the movement in two strokes, up and down, multiplied by the engine speed.
Therefore, the formula has the following appearance:
PS = 2\cdot S\cdot RPMPS – piston speed,
S (length of stroke) – represents the distance the piston travels in one engine cycle within the cylinder,
RPM (revolution per minute) – represents the number of processes or cycles produced by the piston in one minute.
The equation is multiplied by the number 2 because one cycle includes situations when the piston reaches both the upper and lower torque in one turn.
When it comes to using our calculator, the procedure is identical. Our calculator contains two blank fields called a length of stroke and revolution per minute. After entering arbitrary values of the listed elements, the calculator will display the value of the piston speed in a few moments. The principle of operation of the calculator works on the formula we explained earlier.
Piston Speed Example
Example number 1:
The value of the piston stroke is known to be 5 inches, and one cycle is 1000 rpm. Calculate the engine piston speed.
Solution:
Having already known values, after including the data in the calculation formula, the value of the piston speed in this case is:
PS = 2\cdot S\cdot RPM = 2\cdot 1000\cdot 5 = 10000in/minWe interpret the obtained results so that the clips in this example move at an average speed of 10,000 inches per minute.
The purpose of calculating piston speed
Reading everything above, you probably wondered why you need to calculate the speed of the piston and what does it tell us? You can use this measure as an excellent indicator of the durability of components and the potential of engine operation under challenging conditions. The higher the piston speed, the higher the engine’s productivity, leading to better performance engines. The function of the piston applies a specific force that can convert into energy. If the energy is too large, it will affect the durability of the piston.
The engineers paid attention when making the piston to the strength of all the necessary parts of the rods, screws, and crankshafts to ensure sufficient speed of the piston.
Mean piston speed
You can also use the mean piston speed to measure the piston speed. This is the value achieved at the average piston speed in the engine associated with the length of stroke and angular displacement of the crankshaft per stroke at a given speed. It is proportional to higher fuel consumption, higher engine power, and piston acceleration and deceleration.
The measure of mean piston speed has strong power and importance in determining engine performance. It is the average piston speed achieved in a piston engine. The formula for calculating the mean piston is:
V_{mean} = 2\cdot \frac{S}{1000}\cdot \frac{RPM}{60}Examples of Mean Piston Speeds table
The limiting factor for engine operation is fuel consumption. To achieve the lowest possible consumption, keep the engine speed at the lowest possible. However, it all depends on the engine type and the power. That is the main goal of most engines that is achieved with the highest possible average piston speed.
The higher the mean piston speed, the shorter the fuel burning time. Reducing the gas, you can change time results and increase fuel consumption. Otherwise, low mean piston speed will not be enough to burn fuel because the heat is reflected. The following table shows some of the engine types with their mean piston speed values:
| Engine type | Max power (Vmps) |
|---|---|
| small industrial engine | 7 m/s |
| marine & generator | 8.5 m/s |
| train & truck | 11 m/s |
| automobile (low speed) | 14 m/s |
| automobile (typical) | 16 m/s |
| automobile (hi-performance) | 18 m/s |
| racing (endurance) | 22 m/s |
| racing (short race) | 25 m/s |
| drag racing | 30 m/s |
Maximum piston speed
You can calculate the maximum piston speed by multiplying the stroke value by π. Then, you need to divide the new value with the number 12 to obtain the result expressed in feet per revolution. After that, multiply the final value by the maximum engine speed to get the maximum rate per minute value.
The maximum speed of the piston is the point where the piston achieves an angle of 90 degrees concerning the crankshaft. The fact is that the average piston speed is much lower than the maximum speed. That is why you must know what the maximum speed means.
FAQ?
1. How do you calculate piston speed?
It would help if you had stroke and RPM data to calculate the piston speed. To calculate piston speed use the formula: Piston speed = 2 x RPM x Stroke.
2. What is a safe piston speed?
Depending on the type of piston and the engine that works on this principle, the usually accepted limit that is safe is around 3500 fpm.
3. How do you calculate piston speed from rpm?
According to the formula for the mean speed, you can get the average speed value. It means a cycle of two moments multiplied by the engine speed (RPM), which is further divided by 12 to get the result expressed in feet per minute (fpm).
4. How fast does a piston move in mph?
After the value obtained for the piston speed, you can express it in feet per minute (fpm).
If you want to express fpm in meters per hour (mph), you need to divide the result by 1,467.
