Sunday, 30 June 2002 17:00

The evolution of dimensioning

Written by Timothy W. Morgan
Rate this item
(0 votes)

Repairing a damaged frame on today's vehicle designs requires more accurate dimensioning and newer repair techniques than ever before. The "old oak tree repairs" have been gone for years. With the birth of the unibody came three-dimensional measuring systems and fixtures, which replaced tape measures, tram gauges and centerline gauges. Now as we fine-tune our facilities to improve our efficiency and work quality, we move into the age of computerized dimensioning. 

A little history
Let's start in the beginning with a tape measure. A tape measure worked to measure a straight line between two given points and was fine for vehicles with a ladder type frame. Add in the old tram gauge and again a single dimension measuring system. Add centerline gauges to the list of now antique equipment that also served the industry well in its development stages. Centerline gauges allowed the technician to see if the three sections of the vehicle were square or parallel to each other. Using a "line of sight" to match each section's centering pins together.

As measuring evolved so has the data supplied. Car manufacturers were able to supply point to point information to the repairer when the vehicles were not complicated to repair. Mild steel frame rails were relatively easy to hold and pull at the time. Then aftermarket suppliers found a need to fill by offering more than the OEM's in data information.

Then the unitized body vehicles rolled into our life. A whole different design arrived without much warning and you might as well throw your tape measure out the shop window. Crush Zones, pinch weld flanges, nothing to wrap the chain around to hold anymore!

Fixturing then became the answer to correct the dimensions of a vehicle back to factory specifications. Fixturing however was cumbersome, involving dismantling of the vehicle in order to place the fixtures in position. It was also expensive, which led to rental banks across the country to house and ship these fixtures to the shops that couldn't or wouldn't buy them. The rental banks promised to make frame repairs more economical for even the smallest body shops - unless you were the one waiting for the fixtures to arrive at your shop.

Fixtures did give the technician a simple "fit or no fit" task without the use of any tape measure. Fixtures were designed from information supplied by vehicle manufacturers and measuring of the vehicle by the fixture designer to resemble the OEM build fixture.

New designs spread damage

Ever more complex repairs evolved as new vehicle designs forced collision damage through the vehicle instead of isolating it in the rigid rail section. The unibody design absorbs damage because each panel is connected to the next and the collision energy flows through the vehicle. That's why it's not uncommon to find movement in the roof or quarter panel in a front-end collision.

With these complex unibody designs came a need for additional dimensioning of both lower and upper body. Thus the introduction of the universal bench and three-dimensional measuring system to the collision industry.

These universal measuring systems use a bridge or ladder to measure length and measuring slides for width and tubes and scales to measure height. This is all performed simultaneously on several points under the vehicle. The equipment supplier supplies data for this measuring system because it is specific to the equipment. Equipment manufacturers gather their data by measuring new vehicles so the information provided is accurate.

The universal measuring system and bench has made collision repair more efficient by maintaining accuracy without the need for acquiring new "fixtures" every time a new vehicle model is released..

Besides the ability to measure the lower body of the vehicle, upper body dimensioning is also important for structural realignment. Strut tower location is critical to suspension angles, as is proper alignment of the complete upper structure to insure proper fit and operation of motor mounts, doors, deck-lids, fenders and other components.

It should be noted that all vehicle manufacturers recommend three-dimensional measuring for all structural repairs.

Computerized laser measuring

To enhance efficiency and speed of repairs, computerized measuring systems were introduced several years ago. Laser systems send light beams to targets, sonar send sound waves to microphones, and robotic arms send information to a computer calculating the exact three- dimensional location of measuring points. Some electronic systems also offer the ability to measure point to point, or measure comparatively the undamaged side to the damaged side. Likewise, some systems allow the tech to diagnosis suspension angles or problems. The data created after measuring is stored on the computers hard drive, and can be printed for the added documentation of the repair.

Those printouts are valuable sales tools to show the customer the damage and necessary documentation that corrections were made. Some systems even offer the ability to transfer printouts to your estimating software for added documentation for insurance companies.

Another growing trend is to measure the vehicle electronically during the estimate, which allows the shop to document damage right away without the need to tear the vehicle down first. This early detection helps the shop's cycle time by identifying potential slow downs or re-inspections.

Computerized measuring systems have another important benefit -- they allow the technicians to measure the repair while it is in progress and make real-time corrections. The technician becomes more productive and the shop can monitor quality of the repairs being performed.

Timothy W. Morgan is Director of Technical Services and Training, Car-O-Liner Company.


Read 8298 times