Automotive Body Repair: Straightening Techniques & Equipment
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Tensile Shots: Deformed Part Restoration Process
The process of restoring a deformed part using tensile shots involves basic traction equipment. The principle applied is a force equal to, but opposite in direction to, the deformation.
Straightening Equipment
Repairs are performed cold, using forces counter to the deformation. This equipment is capable of:
- Applying force at the appropriate point and direction.
- Properly anchoring the bodywork.
- Allowing for precise measurement.
Benches for Vehicle Repair
These include all elements and tools useful for diagnosing and repairing car structures affected by collisions. Measuring systems can be classified as: universal or positive control.
The choice of equipment is determined by work volume, vehicle models, workshop space, budget, and the coach builder's profile.
Components of a Body Repair System
A complete system typically comprises:
- Work bench (frame)
- Anchoring system
- Traction equipment
- Fixtures
- Measurement equipment
Work Bench Types
The work bench is a rigid part that supports the vehicle and provides necessary utilities.
High-Ground Frame
A rectangular structure, typically made of T or U steel beams. It is deformable and features a mechanized top section for holding the vehicle. Its borders have anchor attachments for bed rails.
Types:
- Fixed: Anchored to the floor joists, where work is performed via anchoring.
- Mobile: Features wheels and brakes, allowing transport by workshop elevator.
- Overhead: Height can be adjusted for lower operations, located on a lift, scissor lift, or columns.
Ground-Anchored Frame
Features embedded rails in the floor, providing useful anchoring points where necessary. The advantage is that no free space is left, but it can be inconvenient for certain types of work.
Anchoring System
A set of tools useful for securing the vehicle to the frame. It includes specific items for anchoring the car to frame mechanisms. There are universal jaws for gripping sills, and tie pins are also available. Useful replacement parts are included.
Traction Equipment
This equipment uses hydraulic power for tension or compression shots, applied in the same direction but opposite to the deformation. It is powered by an oleo-hydraulic or hydropneumatic pump.
Traction Equipment Types
With Squad (L-shaped)
Features a pneumatic cylinder powered by a pump. It unites two separate arms to actuate the cylinder; one arm is anchored to the bench, and the other forms chain angles.
With Column
Includes a pump, an internal cylinder, a main column, a tower, a collar, and a pulley. The tower pulls the chain, maintaining a constant pulling direction.
For Vector Shots
An angular force system where the anchor chain is designed for pulling in polygons using only force. It features hydraulic return, an expansion jack, and a pump.
Measurement Equipment
Essential for measuring heights to ensure that, once repaired, the deformed parts conform to manufacturer specifications.
Forms of Measurement Testing
Positive Control Tools
Uses fixed calipers for each check point. Easy to use but requires a large number of tools for each brand.
Universal or Dimensional Control
Measured by direct comparison or by specific bodywork points.
Measurement by Comparison
Compares symmetric distances between points.