Measuring for a PROPER FIT

Jan. 1, 2020
The interesting thing about setup on a dedicated bench is the fact that doing so also is considered to be part of measuring the vehicle. You may be able to charge for this time (it's something to think about).

One more repair area where guesswork only creates more work

How many of you remember that mid 70s Chevy Nova you saw from the rear, "dog tracking" so badly that you could clearly see the front fender and maybe even the front bumper end? I remember that scenario vividly, indicating a poorly repaired unibody vehicle. How many times have you seen poorly fitting sheet metal panels and elongated bolt-holes when you've lifted the hood of a customer's car?

These issues used to be commonplace back when most collision shops did not have the knowledge or the proper equipment to repair a vehicle that had sustained structural damage. It is not as common now as it used to be, but unfortunately, it is still occurs in the industry even today. This should be alarming, but I doubt that it is. Why do some technicians still have the mentality that close is good enough? Ever see that veteran frame tech using his thumb to eyeball a pull? It amazes me every time I see it, and I see it much more than I should.

The importance of measuring

The easiest way I have found to convince techs and managers about the importance of measuring is to site examples of its use in other common industries and how not measuring properly affects them. For example, what if a carpenter were to eyeball all the cuts and angles when building a new house? Or if the foundation walls were poured "by eye?" What if your doctor guessed at the location of his incision during an operation without consideration for the location of the vital organs in the surrounding area? What would happen if he did not use modern equipment like cat scans or x-rays to locate the tumor of a patient, and just started cutting away, hoping to find it "in there somewhere."

I know these sound ridiculous, and they should, because no one in their right mind would allow any one to perform any of the described operations that way. Yet some of us think it is OK to pull a unibody close enough, and then use a sheet metal panel as a ruler and trial-fit it several times to get the right pull dimension.

Think about how dangerous it can be to put an improperly repaired vehicle on our roads. The dimensions of the structure, the position of the sheet metal and the bumper mounting, the strength of the welds and the tensile strength of the steel itself are all taken into consideration when designing a car to be safe. Not one of us in the repair industry has the capacity to re-engineer these vehicles and alter the way they perform when involved in an impact. Yet this is precisely what we do by not following protocol during the repair.

What we can, and must do, is repair it back to the standards set by the manufacturer. The only way to do so accurately is to measure.

Tools and methods

There are a variety of measuring tools available today to utilize when looking to accurately measure a vehicle during the repair process.

Dedicated fixture bench

On a dedicated fixture bench, the jigs or "fixtures" are not intended just to rigidly mount and hold the vehicle during the pulling process. They also provide a method of measuring specific control points as well. Since many unibody vehicles are built this way, it is an extremely accurate method of measuring and repairing damaged structures.

Some of the older fixture benches were limited in their measuring capacity, allowing for measurements only on the underbody and strut towers. Calling this measuring may be misleading because when using a dedicated bench, typically the user is pulling the damaged vehicle to a reference point, or jigged point, rather than measuring a specific distance (the jig is set at the required point). I do not believe there is a system in use today as accurate as a dedicated bench.

Repairers generally believe that setting up a dedicated bench system is extremely time consuming and difficult. However, with the consistent improvements made in these systems over the years, they actually are as easy to set up as a standard frame bench in some cases. The interesting thing about set up on a dedicated bench is the fact that doing so is also considered part of measuring the vehicle. You may be able to charge for this time (it's something to think about).

Additionally, with its recent resurgence in popularity, the fixture bench has been improved and adapted to provide measuring capability with upper body points and door apertures as well. Although these have become more popular in North America in recent years, they are not the mainstay in the United States that they are in the European automotive market.

Sonar and laser measuring equipment

These are the most common types of measuring equipment in use today. They are very accurate and easy to use, once a tech is properly trained. They are all connected to a computer and can print an overview of the vehicle before and after the repairs have been performed. This is a requirement of most DRP programs and should be your requirement as a repair professional. It provides documentation that the structural damage has been repaired, at least dimensionally, to a specific standard.

Both systems work in a similar fashion, by taking measurements from control points located on the vehicle. During the pulling process, targets are located in points on the car specified by the manufacturer. As the damage is pulled, sound waves or laser beams are bounced off the targets, and a measurement is taken by the length of time those beams take to reach a reference point from the target. That time is calculated by the computer in distance, and compared to the pre stored vehicle data regarding that specific vehicle's spec.

The measurements are constantly being calculated during the pulls. The operator can watch on the computer screen as the damage is moved back to its correct pre-accident dimensions. Proper equipment calibration, target location and angle, and current updated vehicle data are imperative when utilizing these systems. Properly used and maintained, these units are extremely accurate.

There are many different applications available today, including the most common systems used in conjunction with a frame rack. There also is the portable laser, used specifically for door aperture, roof and windshield opening measurements, and the touch systems that allow the user to merely touch a pointer to an area designated on the vehicle to obtain a measurement in seconds.

Mechanical measuring tools

These are old standby tools, the tram gauge and the tape measure. They will work in a pinch, and are amazingly accurate, but will not provide the all-important documentation needed for most repairs today. I have seen shops take pictures of measurements on a tram gauge, but this will not be acceptable as documentation to any insurance companies that I am aware of. A tram gauge is a long bar, with basically a precise tape measure built into its face. Attached to the bar are pointers that can slide up and down the length of the bar and be locked at a point with a set screw or spring-loaded locking pin. A tram gauge can be used to reference measurements on a damaged vehicle using printed manufacturers specifications available through several companies or directly from the OEM.

The correct measurement is noted and set up on the tram gauge. The vehicle is repaired, placing one end of the tram on a specific point, and pulled until the other pointer is resting on the correct reference point on the other end. Again, this method will work but is not very accurate and can be manipulated, even by mistake, by incorrect placement of the pointers on the vehicle or on the tram itself.

A tape measure is pretty self explanatory

Since the most common method is the sonar and laser type of equipment, let's run through a typical setup and measure operation. Initially the damaged vehicle is placed on the rack and centered on it. The user then logs into the computerized measuring system and utilizing "user friendly" icons picks the vehicle that is going to be measured from the system database.

Once the vehicle is selected, the system guides the user through the measuring process. The system designates the location of the clamping devices and the type of device needed for the vehicle. Once the vehicle is clamped, the user is directed to diagrams that outline specific target locations and types to use when measuring. This is an area where skill and experience come into play. Understanding the dynamics of the damage and the subsequent necessary pulls helps determine the correct target location. The user also must make sure the computer knows which attaching fixture and target are used before the measurement is taken since they can vary in size and cause incorrect readings during a measurement.

Once the targets are properly hung, the system is activated, and using the center or datum line formed during setup, it measures the vehicle at the specific control points the user has set up. A comparison is formulated systematically between the current measurements and the pre-stored factory measurements. Screen shots of the before, during, and after measurements can be printed at any time. When the pulling is started, the user can watch the changes on the screen in real time as the damage is worked out.

Obviously, this is the simplified version. A great deal more detail goes into an actual measuring and pulling operation. You'll need to keep this in mind.

Final word: No reason not to measure

Considering the tolerances used when building a modern vehicle, it is impossible to properly repair one today without measuring the damage before and after the pulling operation. I cannot think of one good reason not to properly measure for fit but can think of many why you should.

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