Chery QQ - Inspection of Alignment - Bottom Vehicle Body; Explanation and Operation; Explanation of Datum; Forming and Perforation

Chery QQ Service Manual Body
System
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Chery Automobile Co., Ltd
2.5.3.2 Inspection of alignment – bottom vehicle body
Three dimensional methods
It is necessary for the repair equipment to measure the length, height and width of many
measuring points simultaneously, it is also necessary for it to measure 2/3 of the vehicle body to
make things convenient for comparing the structure of vehicle body accurately.
General-purpose measuring system combines the use equipment with the technique to carry out
dimensional measurement including measurement of length, width and height.
2.5.4 Explanation and operation
2.5.4.1 Explanation of datum
Datum
Datum line is parallel to the bottom vehicle body or frame, and the above-mentioned surface is
the datum for all vertical measurement. Datum line is an imaginary level surface, it locates on the
bottom vehicle body, at the same time, and it is parallel to the bottom vehicle body. The height
results from distance measured from the datum line to the certain specified measuring point or
reference point of bottom vehicle body by means of vertical measurement. Dimension of height
is based on use equipment; it decides the position of datum line. Therefore, you can set different
datum lines for the same vehicle, you can plus and subtract the same numerical value from all
height to establish a new datum you need.
Centerline
Centerline is an imaginary vertical surface; it is vertical with the length direction of datum
surface, and pass through the vehicle centre. Centerline refers to the arbitrary straight lines
passing through the datum surface center of the vehicle.
Forming and perforation
Forming and perforation is a process of manufacture, which can form a region on the metal
structure easy for you to carry out three dimensional measurements. You can perforate a hole or
groove on that region easy for dimensional measurement and join together with other parts
structurally. All measuring results can be read-out from the centerline of a formed surface and
hole.
All dimensions can be measured from the following aspects:
● Length to the zero line (1)
● Height to the datum line (2)
● Width to the centre line (3)
All dimensions are symmetrical if there are no other regulations.