The same tracked vehicle, why is the speed difference between the tank and the excavator so much?

The reason is simple and rude-the engine power of excavator is much lower than that of tank engine. Welcome to pay attention to the knowledge spectrum of weapons. Today we are going to learn about tanks and excavators.

Excavators are civil engineering machinery and equipment, which are mainly used for earthwork in engineering construction; Tanks are military equipment, and their only purpose is to fight.

civilian equipment emphasizes economic applicability, and excavators are no exception. under the premise of meeting performance requirements, the use cost, such as oil consumption, should be reduced as much as possible.

however, the traveling speed is not heavy for excavators, so the power distribution ratio of traveling speed is very low in power design, and the main power is distributed to the working mechanism such as the arm and bucket, so as to improve the core performance of digging force.

Take the 5-ton SY485H excavator of Sany Heavy Industry as an example: its engine power is only 3 kW, the maximum speed is 18 rpm, and the maximum traveling speed is 5.1 km/h..

The most important thing for a tank is combat effectiveness. Everything is only for winning, and the performance index is always higher than the cost of use. Driving speed is one of the main performance indexes. The faster the driving speed, the stronger the maneuverability, so the power of the tank engine is very large, and the bigger the better.

Take the 5-ton Type 96 main battle tank as an example: its engine power is 735 kW (1 HP), its maximum speed is 57 km/h, and its maximum stroke is 4 km (road maneuvering).

It can be seen that the power of the tank is 2.45 times that of the excavator, and the running speed is more than 1 times! Therefore, the excavator, which is also a tracked vehicle, can't compete with the tank.

then the question comes-being tracked vehicles, why do tanks need to travel at high speed and excavators don't? We analyze it from the following points.

▼ The picture below shows the 96B main battle tank with a 12 HP engine, which is equivalent to 88 kW, nearly three times that of an excavator! The maximum road maneuvering speed of this type of tank has reached 7 km/h, which is beyond the reach of excavators. The core performance index of excavator is digging force < P > The three most important parameters of excavator are: operating weight (mass), engine power and bucket capacity, which determine the digging force of excavator, and digging force is the core performance index of excavator.

The so-called "digging force" refers to the actual force generated by the bucket when the working mechanism of the excavator is doing work. The greater the digging force, the better the overall performance of the excavator, and vice versa.

the most direct and effective way to improve the digging force of excavator is to improve the power of hydraulic system, which comes from the power provided by engine, so in the final analysis, it is necessary to improve the power of engine.

however, it is not possible to only improve the engine power, because the improvement of the digging force means that the whole excavator is out of balance, and when digging with the maximum digging force, it is very easy to cause a rollover accident.

Therefore, while improving the engine power, the vehicle weight should be increased accordingly, so as to achieve the purpose of improving the operating quality of the vehicle.

the improvement of the digging force is bound to increase the size of the bucket, that is, the bucket volume (bucket capacity), so as to improve the work efficiency. If the bucket volume is not increased on the premise of improving the digging force, it is meaningless to improve the digging force. After all, the excavator's improvement of the work efficiency in engineering construction is ultimately reflected in the earthwork excavation volume.

Therefore, it does not mean that the greater the engine power of the excavator, the better. When the engine output power exceeds the actual demand power of the digging force, the engine output power will be surplus, which is undoubtedly a waste of resources, and the final result is a substantial increase in the use cost.

let's take an example: suppose that the 3kW engine of the SY485H excavator mentioned above is replaced by the 735kW engine of the 96 main battle tank. What will be the result?

according to the national regulations, excavators above 32 tons must use the variable hydraulic station system, so after replacing the high-power engine, the variable system of the hydraulic station will automatically increase the full power variable, and the digging force of the excavator will be increased by more than 6%.

because the vehicle weight and bucket capacity have not been increased, this type of excavator still works with bucket capacity of 3.1 cubic meters. The result is that the excavator will move more smoothly when the digging force is improved, but the work efficiency has not changed, but the fuel consumption has increased by more than 2%, which is really not worth the candle.

so can the increase of engine power improve the form speed of the excavator?

The answer is yes. The maximum speed of the 735kW engine of the Type 96 main battle tank is 22rpm. If it is used on an excavator, the driving speed will be increased to 1km/h, which is obviously improved.

But this is really not what the excavator needs. During construction, the total daily travel of the excavator will not exceed 3 kilometers, and the average speed is about 3.1 kilometers per hour. It is meaningless to give it a speed of 1 kilometers per hour.

Therefore, the research on excavators mainly focuses on improving the digging force, which is why excavators use low-speed and high-torque gearboxes to provide driving power for the crawler traveling system.

▼ The following picture shows the 3kW Volvo ec21b diesel engine assembly used in large excavators, which can meet the power demand of large excavators with a capacity of 3-5 tons. The power generated by it is mainly provided to the hydraulic station to drive the working components to generate excavation force, and only a small amount of power is used to drive the crawler, so the driving speed is very slow. Tank is a highly mobile combat weapon, and its maneuverability is not only related to victory or defeat on the battlefield, but also to life and death < P > As a weapon, the tank also has three parameters, namely firepower, defense and maneuverability. Since the birth of the tank, people have spared no effort to pursue the perfection of these three parameters, so that the caliber of the main gun of the modern main battle tank has reached 125mm, the thickness of the defensive armor has reached 4mm, and the driving speed reflecting the maneuverability has exceeded 7km.

It can be said that people are willing to pay any price, including the use cost, in order to improve the combat effectiveness of tanks and thus win the battle.

Take the M1A2 main battle tank made in the United States as an example (upgraded version of SEP). Its integral weight has reached 7 tons, and its engine is Lycoming gas turbine with 15 horsepower (about 11 kW). The maximum driving speed under road maneuvering conditions is 71 km/h, and the average driving speed under field conditions is 48 km/h. It is the heaviest and fastest main battle tank in the world.

such good maneuverability comes at the cost of high cost, including extremely high fuel consumption. the theoretical fuel consumption of M1A2 main battle tank is 4 liters/1 kilometers, but the actual fuel consumption in actual combat is as high as 58 liters/1 kilometers, which means that its 16-liter super-large fuel tank is only enough to travel 27 kilometers.

Moreover, the use cost caused by the abrasion of the track and the transmission system is also very alarming. In order to improve the off-road performance, the main battle tanks generally adopt glued tracks, and the track needs to be maintained every 5 kilometers on average, including the replacement of glued tracks. The hydraulic gearbox and the hydraulic suspension system of the load-bearing wheel should be maintained every 8 kilometers ...

Regardless of the expensive ammunition, the daily maintenance cost and fuel cost alone are enough to buy a new 5-ton excavator. It can be seen that the high maneuverability is actually a huge capital consumption, but this money is insignificant compared with winning the war.

The maneuverability of the tank is so important that it must meet the requirements of "running to win, catching up and hiding", otherwise the tank will be caught in a desperate situation of passive beating.

"running to win" means that when the war situation is at a disadvantage and the retreat order is received, the retreat speed of one's own tank is faster than the pursuit speed of the enemy; "Catch-up" means that when our own tanks seize the initiative in the battlefield and start to get closer to the enemy's depth, the forward speed of our own tanks is faster than the enemy's retreat speed; "Hiding within reach" means that when one's own tank is aimed, the hiding speed is faster than that of incoming ammunition.

in order to achieve this maneuverability index, the engine used in the tank must be the most powerful, the transmission system must be the top-notch, and the crawler system must also have the best performance. In short, it is at all costs.

▼ The picture below shows the MIA2 main battle tank of the U.S. Army, which is replacing its engine. The Lycoming gas turbine used in the tank has a horsepower of 1,5 horsepower, which can provide powerful power for the 7-ton tank. The biggest difference between the tank engine and the excavator engine is that the former is mainly used to drive the tracked part to run at high speed, while the latter is mainly used to drive the working components to carry out excavation work. Therefore, in order to run faster, the investment in the tracked part of the tank is very high, which has reached the level of "at all costs", while the requirements of the tracked part of the excavator are basically dynamic. To sum up, we can draw the following conclusions:

First, as both tracked vehicles, the reason why the speed of tanks is much higher than that of excavators is that tanks need high-speed maneuverability, while excavators don't, so the engine power carried by tanks is much higher than that of excavators, and the huge difference in power leads to a huge difference in driving speed.

Second, the excavator is civil engineering construction equipment, emphasizing economic applicability and reducing the use cost as much as possible on the premise of meeting the performance requirements, so it will not be equipped with high-power engines and transmission systems that exceed the performance requirements; And the tank is a combat weapon, everything is just for winning, and the use cost is not important, so it can carry all the required high-power and high-performance transmission systems, and it is understandable that the driving speed is much higher than that of the excavator.

Conclusion

When we see that the speed of tanks is much higher than that of excavators, we may overlook the huge cost difference between them. For example, the price of domestic SY485H 5-ton excavator is about 2.2 million yuan (with high allocation), which seems to be very expensive.

however, it is quite cheap compared with the same 5-ton main battle tank. For example, the domestic foreign trade version of VT-4 main battle tank, the purchase price of Thai Army is about 5.8 million US dollars, equivalent to RMB 39.44 million, and the price of a tank of this type is equivalent to 18 SY485H excavators!

imagine what would happen if the working mechanism of the excavator was grafted to the low plate of the tank? I believe that such an excavator can be as fast as a tank, but the question is-when will such an excavator have to work before it can return to its original position? In other words, if the excavator can be as cost-free as a tank, it can also run at a high speed and high maneuverability of 7 km/h.