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DavePropst.com / Introduction /  System Preview /

The Car Building System - A Short Preview 

In the world of specialty cars, very few if any custom-built cars are ever fully and completely modeled in computer software to the degree a mass-produced car from a major auto manufacturer is. Such a high degree of modeling with such tremendously expensive software is beyond the budget of most any concern other than a major manufacturer. Even so, a great deal of affordable software is available to the individual or small business. A major stumbling block in use of that software though is its requirement for accurate full-scale 3D data. Efforts to generate full-scale 3D data without 3D equipment are either extremely labor intensive or very inaccurate or both.

Laser 3D scanners and most 3D measuring systems such as CMM's and articulated arms are designed for use in highly specialized, demanding applications. These include design and development of complex mass production items, digitizing and elaborate reverse engineering of existing items, and many other such operations. Excluding 3D digital scanners and similar devices, these measuring systems, whether digital or analog, provide only point-by-point numeric XYZ representation of 3D position. They generally utilize a single point of interface arrived at through physical or near physical contact with the workpiece. At best they visually present only one 3D coordinate point at one time. For these reasons, as a generalization it could be said they are best suited for measurement and analysis of existing objects. In contrast, the measuring system seen here, although it can certainly measure existing objects, is designed for use as an assist in actual in-the-fab-shop custom fabrication of something that does not yet exist.

This measuring and fixture system is specifically designed and optimized for use in prototyping and manual fabrication of one-off items of the size of a car. It provides both visual reference and numeric data. It generates four simultaneous, visually observable 3D coordinate points anywhere in a 7.0 ft x 7.0 ft x 18.0 ft grid using twelve line generating lasers. In fact this amounts to much more than merely four points in space. Since the lasers are line generators instead of dot generators, an elaborate real-world 3D laser grid of the size just mentioned exists in the form of intersecting points, lines and entire planes in space above the surface plate. This laser grid provides very efficient data interaction between CAD, suspension software, graphics software, high-resolution digital camera, measuring system, 3D universal fixtures, surface plate and the car being built. This entire 3D 'world' exists in the real world in the shop and, optionally, the same 3D 'world' (or more typically, small portions of it) can exist digitally in computer software. The key to data transfer between these two worlds is of course the measuring system.

While the measuring system is indeed a vital component, it is only one part of the overall system. It is not the system itself. The measuring system is just a 'tool' used in the car building system. Interaction between the measuring system and the plate/fixtures is what really makes things happen in the real-world environment in the shop. The centrally located surface plate and related structure is capable of precise full-scale 3D coordinate (XYZ) positioning in space of individual parts, assemblies or an entire car. Unlike the case with a typical surface plate and measuring system combination, components are not merely set in place. They are clamped very solidly by heavy, rigid fixtures in order to exactly replicate a car's structural components before it (the car-to-be that is) in reality has such a structure. These fixtures hold a project's components in place after those components are located to their desired position by the measuring system. The fixtures are deliberately restricted to adjustment in and only in the three axes-- X,Y, and Z. The measuring system moves in and references to those same three XYZ axes. Any motion of the measuring system and/or fixtures in any one axis is independent from any motions in the other two axes. What this means is that adjustments to the position of the rear axle housing, for example, can be made in one axis without disturbing its position in the other two axes.

Some important notes:

Beyond mere positioning of a car's components, the fixtures, table and its surface plate are strong enough to be used for correction of warping from welding during construction, controlled loading of springs and suspension members on digital weight scales, load testing of structural components etc.

Some of the fixtures, particularly those for suspension and drivetrain components, actually have 5-axis motion to aid in complex positioning required for those items. However, the additional axis movements can be locked out (usually by set-screw or adjustable stops) to restrict motion to only basic XYZ when desired.

This elaborate positioning of components is achieved without obstructing the external broadside, front, rear or three-quarter views of the project. An unobstructed view is mandatory for full-scale mock-up for photography and design work.

Real-World Uses of the System

A critically important concept to grasp is that 3D data can flow forwards or backwards. A concept, part, assembly or car can be designed in software, the data moved to the real 3D world by laser-generated coordinates and the item then created in metal. On the other hand an existing part, assembly or car can be positioned on the surface plate using the fixtures, the measuring system can be used to acquire real-world 3D data of that item, and that data can then be input to software for analysis or component alteration. Consequently, whether developing a vehicle from scratch using digital methods, reverse engineering from an existing vehicle, or anything between the two, total flexibility is available in choosing where to start a project and what sequence of operations to use in the design and construction of that project.

Since the table and fixtures can place and retain individual components in a 3D environment, there is seldom a need to possess or purchase part 'A' before part 'B'. This placement of actual components in the midst of 'phantom' components can be applied to chassis, engine, body or whatever else since the system is by no means limited strictly to chassis work. In actual practice, body panel development and/or fabrication, wheel/tire placement, and ride height determination is usually done before even procuring or building suspensions, axles, frame rails, etc. This is dramatically much more elaborate than the industry standard visual mock up. It is a full-on final placement process. This system can, for example, place and retain (in 3D) just a front fender or an entire body over both an engine placed in its actual designed location and a front wheel/tire/hub assembly placed in its suspension software determined final position. The wheel/tire/hub assembly can then be aligned by alignment gauges to the desired specs and steered through the desired steering arc to check clearance between tire and fender or tire and exhaust header. This can be done without even having on site any frame rails, frame crossmembers, body mounts, motor mounts, suspension control arms or steering rack. All of this, again, can be achieved as a mock-up without obstructing photography of or viewing of the car itself.

Carrying the above hypothetical fender/engine/suspension example even further and illustrating the concept that data can flow in either direction, the above scenario could be used to check suitability of an existing fender, or, used as a means to arrive at a modified or all-new fender shape. This latter could be done either digitally in computer software or by traditional full-scale modeling by wire form, buck, pattern, etc. Indeed, through full utilization of all of the mechanical capabilities of the measuring/fixture system, most, if not quite all, of this type of full-scale design and planning work can alternatively be done without computer software involvement. The system's capabilities therefore appeal to both traditionalists and computer oriented customers.

Presented here is a look ahead to what is in the 'TECHNICAL' section of the menu-- without being overly complex and detailed.

These comments are only a small sampling of some of the equipment's capabilities. For a general description of the full range of services provided proceed to the next stop-- the Shop Overview in the 'INTRODUCTION' section of the menu.