This article is the second part of a two-part series on measuring.
The first article, "Measuring Basics" covered two-dimensional
Measuring systems have gone from total user-dependent
designs to systems that provide increased consistency, better
resolution, ease of use and 3-D capabilities. Dedicated bench
systems, universal mechanical systems, mechanical laser systems
and computerized measuring systems are all part of the evolution
of measuring systems – an evolution inspired by one word: unibody.
Still, despite all these technologically advanced
systems, there isn’t a system on the market – yet! – that can’t
be misused to introduce human error. For this reason, it’s a necessity
that technicians understand how to properly operate these systems.
Dedicated Bench Systems
In the late ’70s, as the unitized revolution
began in the United States, the need for better measuring systems
became evident. Because most vehicle makers outside North America
were already producing unitized vehicles and the repair industry
abroad was already using measuring systems unlike those common
in the United States, the introduction of the dedicated bench
system in the United States was a direct result of the systems
used in other countries. (Even today, the dedicated bench system
is the most commonly used system in many other countries.)
Dedicated bench systems offer many advantages
to the user. The "bench" generally becomes the anchoring
device to the vehicle, as well as the platform where the measuring
fixtures mount for structural dimensioning. The bench is then
anchored to the pulling system, solving many immediate problems
involving where to hold the vehicles without damaging the anchoring
In some bench systems, the pulling systems
are external, separate systems that can be used without the bench
or integrated to the bench by mounting pulling towers or hydraulic
pads to the bench. In many cases, the latter became popular due
to the mobility of the bench and pulling system.
Dedicated fixtures, measuring attachments
designed for one body type, were introduced in the United States
with great reception, and the original versions were targeted
to the newly introduced, high-volume vehicles manufactured by
U.S. automakers. The fixtures were very sturdy and not only allowed
for easy identification of structural damage, but were strong
enough to act as welding jigs during assembly of structural components.
These "fixture sets" for most bench
manufacturers were stored in large metal boxes requiring a fork
lift to move and stack. As fixture sets became available for more
vehicle types, storage, rental and availability became an issue
for many collision shops. To address this problem, some manufacturers
began to develop universal fixture bases to fit a wider range
of vehicle types and only required the ends be designed for specific
vehicle types. These fixture ends or tips could be shipped easier
than the complete set.
Another advantage of fixtures is how they
gauge the vehicle’s damage by either aligning properly in a control
point, reference hole, bolt or nut. And the room for judgment
is very minimal, which adds to consistency.
Normally, fixtures are designed to diagnose
underbody structural areas and strut tower locations (some sets
have included steering-system mounts as well). But, many times,
mechanical components, such as the suspension, steering and drivetrain,
require removal to use – one reason other systems became popular
in the early 1980s.
Today, many vehicle manufacturers still prefer
the use of dedicated bench systems for repairs, maybe because
vehicle manufacturers feel the consistency gained from these systems
is critical to their customers satisfaction.
The setup of these systems is very basic,
and low to mid technical skills are required to mount a vehicle
on a bench. While anyone can quickly verify repairs by looking
at the location and tension of each fixture pin, repair documentation
is difficult unless you manually mark each control or reference
point as "correct" on a setup or dimension sheet.
Universal Mechanical Systems and Mechanical
Universal mechanical systems became popular
in the United States in the early 1980s due to the number of different
vehicle types and models serviced by most repair facilities. Universal
refers to the ability of the measuring system to adapt to different
vehicle types and different pulling systems.
There are distinct categories of universal
mechanical systems. Some systems require a great deal of assembly
on the user’s part – using regular dimension manuals for measuring
locations – while other systems require less assembly and use
their own setup sheets.
This latter category is normally designed
with less "setting scales," and extension pieces, cones
and attachments are color or numerically coded – which generally
lessens error, again increasing consistency and speed of operation.
These systems also use special setup sheets designed for them.
In many cases, the equipment manufacturer has physically verified
the dimensions and may include notes as to their accuracy.
Universal measuring systems also introduced
the third dimension of measuring – datum length – based on the
zero line/plane. Before these systems, the datum line/plane (height)
and centerline/plane (width) were used with one- or two-dimensional
tools to identify damage, and simple "point to point"
measurements were taken for length.
The zero line/plane introduced the starting
point for length dimensions for 3-D measuring systems. These length
dimensions are the datum length dimensions that required conversion
to be used with one- or two-dimensional tools, such as tram gauges
or measuring tapes. With 3-D measuring systems, however, these
dimensions aren’t converted.
Universal mechanical systems normally allow
for multiple point measuring and usually have upper-body measuring
capabilities with the use of an overhead bridge assembly. This
bar can be used not only for referencing strut tower positions,
but also for other points on the vehicle by using the symmetry
principle (covered in "Measuring Basics").
Universal mechanical system components are
typically made of aluminum or alloy materials and can be damaged
if not stored or used properly. For this reason, a technician
will generally lower the measuring pointers during pulling to
Setup is critical when using these systems.
If the main measuring bridge isn’t properly aligned to the vehicle
in the undamaged area, the measuring accuracy is lost in the damaged
areas. Also, if during pulling the vehicle mounting moves, most
systems require the measuring system to be realigned to the vehicle.
Another variation of the universal mechanical
measuring system is the mechanical laser system. The mechanical
laser system requires the technician to install targets at control
or other reference points. By aligning the laser to the vehicle,
measuring can then be done to diagnose both under-body and upper-body
damage. Some laser systems are used in conjunction with a universal
mechanical system, and some systems also perform wheel alignments.
The laser acts as a string of light that passes
through targets. Symmetrical readings also can be used during
the repair process for areas not given in the dimension guide
– a technique that allows for easy location of A and B pillars
during pulling of a "side hit" or checking for other
"side sway" damage. Instead of installing doors to check
fit, most of the pulling can be done and checked by referencing
the light beam. (The universal mechanical system can normally
reference these same points, but it requires the movement of the
transverse bar each time a point is referenced.)
If repair documentation is required for any
of these systems, the technician must manually write the before
and after readings on a dimension sheet or a specially designed
form. Validating the repair for some systems will require going
to each point and rechecking each reading, while other systems
are designed to check repairs by locating the laser beam through
During the last 18 years, manufacturers have
introduced to collision repairers a variety of computerized systems
to aid with management and the repair process, such as job costing
and tracking, estimating, paint mixing, color verification, electronic
diagnostics, wheel alignment, material inventory – and vehicle
Computerized measuring systems have added
a new dimension to the documentation aspect of the repair process.
Many years ago, the wheel alignment industry benefited from equipment
that produced documentation of the wheel alignment performed,
and today, that same benefit can be realized by the collision
Computerized measuring systems fall into three
main categories: laser activated targeting, ultrasonic emitters
and mechanical arms. All three systems identify where the damaged
points should be in relationship to the location of three main
control points, with these three control points establishing the
vehicle’s datum line/plane, centerline/plane and zero line/plane.
From this, the computer determines where all other points should
These systems are generally very portable
and can be used with many pulling systems. The accuracy is still
dependent on user setup but is much less complex than universal
mechanical or laser systems.
The setup sheets for most computerized systems
require the technician to mount targets, adapters or emitters
to the vehicle using specially designed pieces. As with any of
today’s Windows programs, the help systems do all but actually
mount the system to the vehicle, and video and graphic support
Whether the system uses targets, emitters
or a mechanical arm, it’s important that care is taken with setup,
maintenance and storage – and be careful when welding or cutting
is done around these units.
In addition to documentation, accuracy and
the ability to monitor repairs during the pulling process are
benefits not to be overlooked. Reassuring customers their vehicles
have been restored to factory specifications and providing them
with documentation goes a long way in improving business.
While the responsibilities of repair haven’t
changed much since the early ’80s, methods and equipment available
to do them more precisely and efficiently have.
Today’s vehicles demand a high accuracy of
repairs, and 3-D measuring systems can provide that necessary
accuracy – provided technicians are trained on their proper use,
are willing to ensure their proper use and are monitored in that
Writer Tony Passwater is a long-time industry
educator and consultant who’s been a collision repair facility
owner, vocational educator and I-CAR international instructor;
and has taught seminars across the United States, Korea and China.
He can be contacted at (317) 290-0611, or e-mailed at ([email protected]).
In the future, all computerized systems in a shop will communicate
so information can be included in an electronic vehicle file for
easy access. This will create a more efficient paperwork process
and allow managers (or even customers) to monitor the repairs
without physically verifying the repairs in the production area.
A tech suggests that you shouldn’t be surprised if the specs in
the books are inaccurate – and if you’re stumped by them, ask
Q: What are your main challenges when it comes to measuring
and straightening, and how are you trying to overcome them?
A: "Measuring points are inaccessible because of exhaust
systems, underhood components, suspension, grease- or dirt-covered
undercarriage, crushed control-point areas due to poor lifting
procedures and poor or incomplete control-point data," says
Henry Netter, an ASE Master Certified Collision/Refinish Technician
at Auto Tech Collision in Philadelphia. "[We also have] difficulty
with accessing parts for removal and with old rusty hardware that
refuses to budge (real time/profit killer). [Also, sometimes]
prior repairs aren’t quite up to standards."
Q: Are shops having trouble getting paid for all the time
and work that go into the measuring and straightening processes?
A: "A good estimator/shop appraiser should be able
to rationally explain repair procedures to either a customer or
an insurance adjuster. I feel the problem is that many estimators
– shop and/or insurance – don’t have the actual hands-on experience
of a start-to-finish unibody repair. This, in turn, hinders the
actual repair tech to turn a profit on a job since he’s allowed
‘X’ amount of hours based on … what – a guess, hope, fantasy?
Then, if it takes longer – as it usually does – the tech looks
unprofessional based on an unfair standard placed upon him by
inexperienced repair writers, not doers!"
Q: How does the shop in which you work charge for this
type of work?
A: "We accept prevailing rates allowed by insurance
Q: Does any particular job stand out as being difficult
or as a learning experience?
A: "Two jobs stand out in my mind. The first one was
a Mustang hit in the front. Nothing measured up according to specs.
After hours and days of frustration, we contacted [an equipment
manufacturer], and they told us the control points in the books
were inaccurate and guided us to success.
"The second one was an older foreign car that just didn’t
follow standard crash damage direction. According to the books,
the crash caused the towers to roll out! No way, since the front
strut towers are designed to roll in on a front-end hit. Again,
total frustration until I rechecked and found the correct specs."
Q: Do you have any advice on this type of work?
A: "My tips or suggestions are to be patient and observant.
Nothing beats experience to get you through the tough ones.
"Don’t always trust the specifications in those books. If
doesn’t seem right, step back, take a deepbreath and try again.
And don’t be afraid to ask for help if you’re stumped. It really
helped in my instances."