Repair Bench and Measuring Systems: Overview
May, 1981 RESEARCH BULLETIN No. 01-81
Introduction:
The identification and repair of damage to transverse engine, front wheel drive, unitized vehicles with MacPherson Strut suspension represent a relatively new and significant challenge to the autobody repair industry. It is recognized that highly skilled autobody repair technicians can accurately repair unitized vehicles of this type, but all too frequently, these skill levels are not available. Several new bench and/or measuring systems have recently been introduced in the American marketplace and others are expected in the near future. These new systems can have the potential of increasing productivity and the quality of repair. Tech-Cor feels it has a continuing responsibility to evaluate this new technology in order to provide you with information which will aid you in evaluating your business needs.
Today's need for precision with modern unitized vehicles:
Vehicles currently in production and those scheduled for future introduction will have the features mentioned above, along with new materials, thinner steels and, in some cases, high-strength steels. Wheel alignment adjustments are often quite limited or have been totally eliminated. All welded body members are considered to be load carrying. The front and rear portions of the vehicle have been designed with crush zones to maintain passenger compartment integrity. Close tolerances are main-
tained during production of these vehicles. Failure to comply with manufacturer's specifications can result in a multitude of problems, such as: driveline vibrations, improper ride and road handling difficulties. Through the use of precision measuring methods found on benches/measuring systems these problems, in most cases, can be eliminated and damage easily identified.
Examples of vehicle damage which would benefit from a bench/measuring system repair:
Damage to suspensionmounting areas.
^ Damage to front rails/aprons that will affect front wheel alignment.
^ Damage to rear rails/innerwheel housing that will affect rear wheel alignment.
Damage to the center section of the vehicle that will affect wheel alignment.
Damage to rack and pinion mounting area if mounted to unitized structure.
Methods used to determine damage:
^ Visual inspection
Diagonal measurements/ tram gauge/measuring tape.
Frame gauges to establish datum and if twist or side sway is present.
^ Bench/measuring system.
Dimensions taken should match manufacturer's dimensions, (usually available at a dealer), frame/body specification books, or if required, dimensions taken from an undamaged vehicle.
Types of systems:
Presently there are two types of bench systems available: universal and dedicated. Their differences can be defined in the following manner:
A universal system employs the use of mechanical indicators, or a laser beam for locating specific suspension and underbody control points. Additional measuring equipment is not required to repair different makes and models of cars.
A dedicated bench employs the use of fixtures for locating specific suspension and underbody control points. Different fixtures are usually needed for repairing different makes and models of cars. These fixtures must be either purchased or rented. However, exceptions occur when the floor pan is shared by other makes and models. It should be noted that it is not usually necessary to install all the fixtures (dedicated system) or all the measuring scales (universal system) but only those necessary to align the system to the vehicle and those in the damaged area to accomplish repairs. Three undamaged or restored areas are necessary to properly align the system to the vehicle. Four undamaged areas represent the ideal situation and are most often located in the front hinge pillar and rear seat areas.
Bench/measuring system descriptions:
The Tech-Cor Research and Engineering staff has repaired
more than 50 customer and salvage vehicles in its evaluation of the following five bench/ measuring systems included in this bulletin.
A description and drawing of each bench/measuring system precedes a summary chart which presents issues affecting all five bench/measuring systems.
Setup and takedown time:
Dedicated System Setup and takedown time includes:
1. Installation and removal of four center-located fixtures and rocker-panel clamps (if applicable).
2. Installation and removal of the vehicle from the bench.
3. Storage of components.
Universal System Setup and takedown time includes:
1. Installation and removal of the measuring system and rocker-panel clamps.
2. Installation and removal of the vehicle from the bench.
3. Storage of components.