Improving Design and Manufacturing

Drag racing is a fast and vicious sport. Thousands of horsepower are released in the blink of an eye and must be used safely on the track in a matter of a few seconds. In comparison, the average road car might have one or two hundred horsepower and take about 20 seconds to cover that distance. Needless to say, some smart engineering and manufacturing technology is needed to achieve a reliable drag racing car.

Drag racer Paul Carey of AERO Racing drives a Mazda RX-7 in the ‘Supercharged Outlaw’ class of ANDRA’s National Drag racing series. The AERO Racing team have been using an advanced quad-cam Toyota V8 engine to power the RX-7 down the 400m drag strip. Not only has this given them a point of interest, as it is unique to have a Toyota V8 among the legions of American V8’s, but also enables them to be running sub 8 second 400m times.

During the 2008 season, reliability problems with the engine were not letting Paul and his team achieve the best performance from the car. The extreme pressures from the big PSI supercharger were frequently splitting cylinder bores in the steel block, leading to expensive and time consuming engine rebuilds – not to mention the loss of points in the competitive series.

The solution was to develop a completely new engine block from a billet of Alumec 89 which could withstand the rigors of competition. But without starting from scratch and re-inventing the wheel, or engine even. The next best thing was to manufacture a better version of the standard block, stronger and more durable and at the same time retain the ancillary systems that were already developed for it, such as the PSI blower, heads, camshafts and bell housings. One of the aspects to improve on was to remove un-necessary water coolant passageways in the block, which are not required when runs are typically less than 10 seconds and using Methanol fuel.

The need for some reverse engineering was obviously there. Reverse engineering is a process where a physical part or complex shape is digitised to create a CAD (Computer Aided Design) model on sophisticated computer software. Ultimately using this CAD model to re-engineer, update or add to the original design.

Other uses of reverse engineering are in cases where the CAD models or manufacturing drawings for the original parts may not exist and need to be re-created, such as re-creating parts for historic cars or machinery or additional parts to accurately interface to existing parts. All the automotive manufacturers and even top motorsport teams utilise such technology to speed up the design process.

There are several ways to reverse engineer a part, including measuring it with a ruler by hand. But more sophisticated methods are available; these are called CMM, (Coordinate Measuring Machines). More specifically a portable CMM, which is in essence an articulated arm with a probe, was required in the case of the engine block. A high precision rotary encoder (a high precision position sensor) for all 6 or 7 axis enables the part to be measured to an accuracy of within 0.02mm. You can measure any point on the part in full three dimensions (X, Y and Z) by simply touching the probe to it. Otherwise laser scanning attachments are available which enable the full three dimensional surface to be digitised. This is more useful for non geometric shapes and contours like the dashboard of a car for example.

In all cases, an experienced technician is needed to operate such a high precision machine, as even the movement of an operators breathing can give vastly varying results. There are techniques to help against this happening, such as taking more data points and averaging the results.

A full survey of the existing engine block’s features was performed and then used to produce an initial CAD model or point cloud model. The tool enables the user to create surfaces, circles, points and lines in the 3D model representing the real part’s surfaces, cylinder bores and bolt holes. Generally this won’t be ready to send to the machinist straight away as a whole host of post-processing is required to create a finished CAD model. This is where an experienced engineer is required to take the measured features and produce a finished solid model with all the dimensions accurately specified and tolerances set out. This whole process requires a large degree of precision and attention to detail to maintain the critical geometric tolerances required by this 1500 HP engine.

The model can then be forwarded to the machine shop for manufacturing. High precision machining is another article, but it goes without saying that CNC (Computer Numerically Controlled) machines are used in all manufacturing industries to produce components with very high accuracy, praising CMM accuracy quite well.