TBAR Part 4

TBAR™ – Computer Design Program / CAD Shaft Laminate Schedule

Part 4

By Carter Penley

Part 3 of TBAR’s series ‘Measurement and Method Of‘’ described the analysis and design solution process required to produce the empirical data to support the “TBAR hypothesis. The next phase was to correlate the composite materials and geometric profiles to test for a more accurate and defined “TBAR” envelope.

First Penley had to analyze the design criteria and implement the materials and geometric shapes that would yield the expected butt flex and tip flex relationship.

The next requirement was to develop shaft patterns and test how closely the tip flex and butt flex deflection numbers could be controlled. This process would also indicate how close the “TBAR” flex tolerances could be held.

Once Penley generated by computer analysis of what we considered a successful base shaft pattern we would then apply this pattern to a series of computer generated geometric/shaft design combinations.

This in-house computer program was developed and written by Penley Sports to enable our engineering staff to instantly generate 90% of the shaft design and performance data by computer analysis, to include: moment of inertia, stiffness, torque curve, shaft weight, shaft balance point, shaft outer diameters, shaft wall thickness, and will generate an auto-cad drawing of all the composite patterns with wrap/overwrap, section gaps and dimensions for the complete fabrication of the prototype shaft; all before a single carbon fiber (graphite) pattern is generated.

To successfully complete this computer aided design analysis task the computer program must perform a series of calculations every tenth of an inch and will generate over 450,000 calculations for each shaft design depending on the shafts total length.

During this phase of the analysis we are able to develop flex and tolerance relationships of the shaft butt section.

This analysis process was confirmed by fabricating a number of shafts using Penley’s manufacturing processes and measuring butt flex at two specific manufacturing operations that we refer to as pre shaft data and machine-1 shaft data. After both sets of data are collected, a statistical analysis is applied and the arithmetic mean and standard deviations are calculated. The pre shaft and machine-1 data are compared, and if the tolerances and ratios stay within pre-defined boundaries, engineering will determine the design solution a success.

The same process is applied for the tip section except much more care during the manufacturing process must be exhibited.

The tip has a smaller diameter even though it has a much thicker wall thickness than the butt, it still has a lower M.O.I., EI and torque values and is much more susceptible to pattern and manufacturing process irregularities; specifically during manufacturing/fabrication and machining operations. Therefore, the engineer has a much more difficult task controlling the structural requirements of the tip section design.

The second engineering task concerning shaft patterns was to develop and test composite laminate stiffness patterns to evaluate the effects of shaft weight on the tip to butt flex ratio measurements.

This process required engineering to develop shaft patterns much like the first step, using different stiffness levels (‘E’ = modulus of elasticity) and fiber areal weight to test flexural resistance to deflection. A major design concern for light weight shafts was structural wall failure at the butt and or tip sections during field testing or play. Therefore cyclic testing exploits any possible catastrophic failure(s) that would present itself during cyclic fatigue testing (~10,000 cycles) in the test laboratory.

This step in the process was also to test how TBAR measurement/test equipment affected light weight shafts. Knowing that lighter weight shafts required the use of high modulus materials of lighter fiber areal weights we needed to develop structural damage data to test TBAR measurements at these lighter shaft weights to achieve comparative TBAR data to shafts of heavier weight.

See “TBAR DSO Incorporating Cyclic Fatigue Testing” Part 5 of 6 – Coming Soon!

Copyright © 2002, 2015 Carter Penley. All Rights Reserved
(all theories and analysis are still pertinent)


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