Special vehicle design basic knowledge   Chapter 1 Overview
I. Design Features and Requirements for Special Purpose Vehicles (1)
1, Â The special car design uses the stereotyped car chassis for retrofit design.
2, Â The main job of special-purpose vehicle design is overall layout and dedicated working devices.
3, Â For special vehicles, many types of production characteristics of less.
4, Â For the design of self-made parts, the production characteristics of single parts or small batches should be followed, and more consideration should be given to the possibility of general equipment processing.
Special car design features and requirements.
Second, the selection of special vehicle chassis
The so-called second class vehicle chassis is based on the basic vehicle type. Remove the container.
The so-called three types of car chassis, generally based on the basic model, remove containers and driving
room.
Conventional vans, tank cars, dump trucks, etc. are usually used in the modification of the chassis of the second class vehicle.
meter.
Chassis selection should meet the following requirements:
(1) Applicability
(2) Reliability
(3) Advanced
(4) Convenience
III. Power Balance and Specific Power of Special Purpose Vehicles
1. Calculation of power balance for special vehicles
If you consider the engine power has a certain reserve, you need to determine the engine a certain load rate, the range is generally 75 % to 90 % .
When the external load varies greatly, or the estimated power required by the vehicle is inaccurate, the lower limit, ie 0.75, shall be taken .
When the external load changes little, or the required power is estimated more accurately, the upper limit is taken as 0.90 , and the general load is not greater than 0.90.
This calculates the total power P required for a dedicated car engine :
2. Calculation of bit rate
The so-called specific power Pd of the car refers to the engine power of the total mass of the vehicle. If the wind resistance is not included, the calculation formula has
      Pd = P / Ma(kw / kg)
 The approximate range of the specific power of a dedicated car ( including a car train ) is:
 Ma < 5 × 10 3 kg     Pd = 0.015 a 0.021kw / kg
 Ma ≥ 5 × 10 3 kg     Pd = 0.0075 - 0.011kw/kg
Ma > 19 × 10 3 kg   Pd = 0.00478 - 0.007kw/kg
At present, with the improvement of highway conditions, the increase in the speed of vehicle transportation, the specific power has an increasing trend. For example, some countries provide that the specific power of buses and trucks should not be less than 0.06kw / kg to prevent the lack of power of vehicles and obstruct the flow of vehicles.
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