Alignment and repair systems
Jig brackets: general development
Vehicle design and manufacture have progressed
considerably over the years. The development of
crash repair systems has likewise mirrored these
changes. When cars were chassis built, the chassis
Figure 14.11Mitek system in use, with P188 Mk2 measuring system (Blackhawk Automotive Ltd )
Major accident damage 413
tended to be relatively flat, so that the repair was
mainly two dimensional. The change to lighter
monocoque construction introduced one other
dimension which demanded further consideration.
First, the height of the critical points on the
vehicle’s underside were controlled relative to an
imaginary datum line, and so height became of
vital importance. Second, accuracy became a far
more critical consideration than in the past, as
suspension systems became less adjustable and
more complex.
Jig brackets were introduced to serve as simple
go/no-go gauges, providing a continuous visual
indication of the extent of damage. During repairs
brackets were found to yield further benefits.
They provided progressive anchorage, meaning
that once a crititical point had been repaired and
locked in place with the jig bracket, it would not
be disturbed by subsequent repairs. In addition,
during building the jig brackets act as a welding
jig to ensure that new parts are correctly installed
and that the positions of important steering and
suspension pick-up points are not disturbed by
welding heat.
Concurrent with these developments, vehicle manufacturers
were concentrating on particular aspects
of car design. They were attempting to improve body
weight by the introduction of high-strength steels
and vehicle safety by incorporating strong passenger
compartments with front and back and crumple
zones to absorb impact on collision. These two
developments mean that cars are more susceptible to
damage in the crumple zone areas at the front and
rear ends as a direct result of the built-in safety characteristic
of deformation of structures. Consequently
more cars now need alignment and repair requiring
the use of jig equipment. In particular there has been
a growth in the number of cars sustaining damage
which, while not major, still requires the use of
proper diagnostic and repair systems to effect a
repair. The repairer must therefore choose the repair
system most appropriate to the degree of damage
present. Consequently there has been a growth in the
development of measuring systems which can be
used in a wide variety of repair situations with speed
and accuracy. With dual systems, which combine
both brackets and measurement, the repairer can
carry out fast and accurate repairs whatever the
degree of damage. However, with any body alignment
system, whether jig brackets or a measuring
system, it is vital that the completion of repair should
be followed by a full suspension and wheel alignment
check to make sure that the car is completely
roadworthy.
Since the early 1950s there has been considerable
progress surrounding jig brackets. On the technical
side, developments mean that the jig brackets are
now available for a wide range of vehicles, are
lighter, easier to use and more readily available. For
ease of use and to prevent possible errors, integral
brackets fit to a regular-spaced hole pattern on top of
five integral beams which are common in all integral
bracket sets. The front integral beams run longitudinally,
as do chassis legs, thus allowing first improved
access to the engine compartment, and second the
production of stronger, simpler brackets. All integral
sets incorporate a number of check brackets which
are fitted without stripping out mechanical components.
Each integral bracket carries a plate which
shows a reference number, which side of the jig it fits
to and which edge points forward.