Now there are more and more fire trucks on the market, the chassis is an important part of the fire truck, so a good chassis is very important. When choosing, we can compare and analyze the following aspects to choose a suitable fire truck chassis .
1. Chassis power unit
1. Selection of power unit type
Vehicle power includes diesel engine, gasoline engine, electric motor (including other new energy power) and so on. Due to the influence of factors such as battery life, electric motors have not been widely used in fire trucks (especially fire trucks driving high-power fire fighting equipment), but it is not ruled out that they will be popularized and used in the field of fire trucks with technological progress in the near future.
At this stage, the power plant of the fire truck chassis is basically still the traditional gasoline engine and diesel engine. There are often differences of opinion on whether the fire truck should prefer a gasoline engine or a diesel engine. In my opinion, we should make a decision based on the different use characteristics of gasoline engines and diesel engines, according to the purpose, use, maintenance and management conditions of different fire trucks, and comprehensive advantages and disadvantages.
First of all, when the total power required by the fire truck to drive and drive the fire fighting equipment is large, there is no doubt that a diesel engine should be selected, such as a fire truck that uses a chassis engine to drive medium and heavy fire pumps, high-power generators, and large hydraulic systems. Or fire trucks with a larger total mass basically use diesel engines, such as fire trucks with a total weight of more than 10 tons.
And fire trucks with a smaller total weight, such as those with a total weight of less than 5 tons, can use gasoline engines. In addition to driving fire trucks, the engine hardly drives fire fighting equipment, or when driving fire fighting equipment with very little power, gasoline engines can be used, such as inspection fire trucks, command fire trucks, publicity fire trucks, and community light fire trucks.
Diesel engines have a series of advantages: wide power coverage, high torque, less electrical equipment (with corresponding fewer electrical faults), and insensitivity to wading.
On the contrary, gasoline engines usually have good acceleration performance, which is especially suitable for small and medium-sized fire trucks that require quick response for the first dispatch. In addition, compared with diesel engines of the same displacement, the output power per kilowatt is lighter than the weight, but there are many electrical equipment, complicated maintenance, and are more sensitive to wading driving.
Therefore, the two have their own merits and can only be selected according to actual needs.
2. Selection of engine rated power and rated speed
As a fire engine engine, there should be a margin in terms of speed and power. According to years of experience in production, testing and use of fire trucks, as well as the recommendations of foreign classics, it is recommended that when the water pump works under rated output conditions, the power drawn by the engine accounts for about 70% of the maximum power at this speed on the external characteristics of the engine; Under rated operating conditions, the speed of the engine used shall not exceed 75-80% of the rated speed of the engine.
When choosing the engine power of the chassis, the specific power of the fire truck must also be considered.
Engine power is also related to the top speed and acceleration time of the chassis, which are all provided by chassis suppliers.
Second, the choice of the total mass of the chassis
When choosing the total mass of the chassis, it is mainly based on the loading mass of the fire truck. On the premise that the chassis is heavy and the mass is equal, the chassis with light curb weight is given priority. In particular, the tank fire truck has a large amount of liquid, and the total mass of the vehicle is basically close to the total mass allowed by the chassis. Do not forget the weight of the equipment and equipment fixtures when calculating.
3. Selection of Chassis Wheelbase
1. The wheelbase is related to the axle load
It is required that the axle load of the fire truck should not exceed the maximum axle load allowed by the chassis factory announcement, and the ratio of the axle load distribution of the fire truck should be consistent with the axle load distribution ratio specified by the chassis.
In the actual layout of the product, in addition to reasonably adjusting the various assemblies of the upper body to seek a reasonable distribution of the axle load, the reasonable choice of the chassis wheelbase is crucial to the rationality of the axle load distribution. When the total mass of the fire truck and the position of the center of mass are determined, the axle load of each axle can only be reasonably distributed by the wheelbase.
2. The wheelbase is related to the outline size of the vehicle
In addition to ensuring the relevant provisions of the axle load, the selection of the wheelbase also needs to take into account the layout of the bodywork and the outline size of the fire truck. The length of the whole vehicle is closely related to the wheelbase. The length of the whole vehicle is composed of several parts such as the front suspension, the middle wheelbase and the rear suspension. The front suspension is basically determined by the chassis (except for the front gun, traction winch, push shovel and other devices of the loading vehicle) , the longest rear overhang should not exceed 3500mm, and should be less than or equal to 65% of the wheelbase.
Fourth, the choice of chassis cab
At present, there are 9 people in a fire fighting squad in my country, including one signal soldier, one commander and one driver. Under normal circumstances, the first fire truck dispatched should have a crew room. When the driver’s cab and the crew’s cab are combined into one, it is referred to as “driver’s cab”, and other vehicles are equipped with corresponding driver’s cabs depending on the actual number of operators of fire fighting equipment.
The domestic fire trucks are all modified from the chassis of the truck. The types and structures of the crew compartments are roughly as follows:
1. The chassis comes with an original double-seat cab, which can take about 6 people.
2. Remodel by cutting and lengthening at the rear of the original single-row or one-row semi-cab. This type of crew cabin currently accounts for the majority, but the level of modification and product quality are uneven. Safety and reliability need to be further improved.
3. Make a separate crew compartment at the front of the bodywork, also known as an independent crew compartment.
At this stage, there are not many products of double-seat cabs for trucks, and the options are not very strong. The quality and craftsmanship of the double-row cab of the imported chassis is relatively high, and the overall level of the double-row cab of the domestic chassis needs to be further improved.
Under the premise of no special requirements, it is recommended to choose the original double-row cab of the chassis.
When choosing a chassis, the possibility of the vehicle should also be considered, such as the vehicle channel circle, the vehicle swing value, the approach angle, the passing angle, the minimum turning radius, and so on. Under the premise of meeting the same functions, a chassis with a short wheelbase should be selected as much as possible to achieve rapid fire response and meet the combat adaptability of rural communities, ancient cities, urban villages and other areas.
Post time: Nov-11-2022