Mechanical Application Brief

Motorcycle Frames

The Solution

According to Phil Korth, a Project Engineer at Harley-Davidson, DADiSP, the graphical display and data management software by DSP Development Corporation, provides the standard platform for PC-based data acquisition and analysis required. It standardizes the analysis capabilities of the various instruments so that data from different sources may be compared.

Data Acquisition

The data acquisition instrumentation at the lab falls into three basic categories; the system provides DADiSP file formats, the system uses a PC plug-in board, or the system has a GPIB port. The optional GPIB module, a DADiSP product that supports instrumentation control and data acquisition, provide the additional flexibility to incorporate the other data acquisition systems used in the Structures Lab.

Frame Load and Deflection

In testing frame stiffness, data is collected for a torsional load and up to ten channels of displacement data. The testing procedure consists of mounting the motorcycle frame rigidly to a bed plate through a swing arm pivot. The remainder of the frame is allowed to float on a low friction surface. Linear Variable Differential Transformers are located geometrically at various points on the motorcycle frame to accurately measure the deflection of the frame when the torsional load is applied to the steering head of the frame. The load and frame deflections are measured and collected in real time.

XY Displacement vs Load

A PC-based data acquisition card is used in connection with DADiSP to read the data directly into the DADiSP worksheet. The necessary conversions are then accomplished transforming the analog voltages into ft-lbs for torque and thousands of an inch for the displacement data. The DADiSP XY functions plot the individual displacement channels vs. the torsional load. The linear regression of these XY plots is then calculated giving a stiffness parameter allowing different frame types and material to be accurately compared.

DADiSP Builds Stiffness Database

Using DADiSP enabled Harley-Davidson to build a database of the stiffness parameters of motorcycle frames. This lets them accurately evaluate how changes made in the frames affect the overall stiffness characteristics. This becomes an important characteristic in the final motorcycle, since the stiffness of the frame affects many characteristics of motorcycle design. "DADiSP provides a standard platform for laboratory instrumentation in the Structures Lab and allows the materials which compose a motorcycle to be accurately characterized," says Phil. These measurements ultimately contribute to the way a customer feels when riding a Harley-Davidson motorcycle, and thus how he or she perceives Harley-Davidson Motor Company, the leading motorcycle manufacturer.