ENGINEERING & STRUCTURE

How Alignment Tools Establish Measurement References

The absolute measurement accuracy of a finished product cannot be judged by its appearance alone. However, by examining its structure, one can discern what serves as a reference, which errors are avoided, and what priorities guided its design. This article explains how to interpret this, using the main body structure and toe adjustment tool as examples.

01 / HOW TO READ THE STRUCTURE

Manufacturing Method Determines Controllable Shapes and Tolerances

Automotive parts are not all made using the same methods. Casting, forging, machining, sheet metal work, and welding are chosen based on the required role and geometric precision.

Alignment tools are no different. In addition to being able to support vehicle weight, they must also be able to use the hub mounting surface and angle measurement surface as measurement references.

The name of the manufacturing method alone does not determine its superiority. It is necessary to consider which surfaces are used as references, how their positional relationships are controlled during each process, and how structurally unavoidable errors are handled.

A diagram comparing how shapes are determined and joints are made for integral machining, bolt assembly using reference surfaces, and welded assembly.
Even for tools with the same purpose, the method of controlling positional relationships and the potential sources of error differ depending on the main body structure.

02 / MACHINED FROM SOLID

Monolithic Machined Structure | Dummy Wheel

The dummy wheel employs a monolithic machined structure.

Since the hub mounting surface, the mounting surface for the toe adjustment tool, and the camber angle measurement surface can all be machined from the same material, their positional relationships can be precisely controlled.

As there are no multiple parts involved, misalignment during assembly and cumulative tolerances do not affect the main body's shape. Additionally, by manufacturing from sufficiently thick material, deformation when subjected to vehicle weight is kept to a minimum.

A diagram showing the dummy wheel's hub mounting surface, toe adjustment tool mounting surface, camber angle measurement surface, and the machined surface that determines the hub center height, in front and side views.
From the hub mounting surface to each measurement surface, machining is performed on a single component without intervening joints.

Maintaining Measurement References Even Under Load

In an analysis with a design load of 500 kg and a camber angle of 10 degrees, the deformation of the body with respect to the camber angle was 0.03 degrees.

This is sufficiently smaller than the ±0.2 degree measurement accuracy typically found in digital goniometers, and in normal measurements, it is difficult to identify body deformation as an independent change.

It is designed not only to support vehicle weight but also to maintain the shape that serves as a measurement reference even when subjected to load.

500 kg

LOAD / Design Load

Analyzed body deformation under a camber angle of 10 degrees.

0.03°

Deformation in Camber Direction

Analyzed value at 500 kg design load and 10 degree camber angle.

A diagram comparing the analysis of vehicle load and ground reaction force applied to a dummy wheel under conditions of 500kg design load and 10 degrees camber angle, with the 0.03 degree deformation of the camber angle measurement surface compared to the ±0.2 degree accuracy of typical digital goniometers.
At a design load of 500kg and a camber angle of 10 degrees, the analyzed body deformation is smaller than the measurement accuracy of typical digital goniometers.

03 / BOLTED PLATE STRUCTURE

Plate-type bolted assembly structure | Hub Stand PLUS

The Hub Stand PLUS adopts a structure where a steel main plate and machined parts are assembled with bolts.

Unlike the dummy wheel, it is not structured to finish all of the hub mounting surface, toe adjustment tool mounting surface, and camber measurement surface by machining. By giving a single steel plate multiple roles, manufacturing cost and weight are reduced.

Therefore, the shape control of each measurement surface is not equivalent to that of a monolithic machined structure. Based on this, the measurement position and positioning method are designed according to the characteristics of the structure.

Measure near the hub, where deformation effects are small.

Compared to machined aluminum parts with sufficient thickness, steel plates are more prone to deflection when subjected to load.

Therefore, the camber angle is measured near the vehicle's hub, rather than at the outer edge of the plate where the effects of deformation would be greater. Considering how deformation occurs, we use a position where the impact on measurement is minimal.

Determine overall length by reference surfaces, not bolt holes.

If the position is determined solely by the clearance of the bolt holes, the main body dimensions may change with each assembly.

In the Hub Stand PLUS, the position in the overall length direction is determined by aligning the laser-cut bottom surface of the main plate and the machined bottom surface of the roller mounting part to the same horizontal reference plane. The bolts are used not to determine the position, but to hold the determined position.

In addition, since the plate attached to the hub can be replaced, it can accommodate different PCDs, number of holes, bolt diameters, etc., without having to purchase a completely new unit.

A diagram illustrating the camber measurement position of the Hub Stand PLUS, the replaceable main plate, the bolted assembly structure, and the positioning in the overall length direction by aligning two bottom surfaces to the same horizontal reference plane.
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