Rail Flex Testing
The following factors were considered in the re-engineering of the Tool Trolley rails that resulted in the design of the current Duplex Rails
The flexing of a guide rail directly affects the accuracy of the cut. A number of factors had to be taken into consideration to fully address the guide rail flex issue:
• Type of material
• Shape, size, weight, density, hardness (brittleness)
• Profile distortion
• Application
The type of material chosen is the primary consideration when it comes to minimizing flexing of a rail . Aluminum is the material of choice for guide rails. It is easily machined, accepts multiple finishes, relatively lightweight, but is softer than most other materials. The approach that many Clamp-on-Guide providers use is to provide a large, bulky rail for the carriage to ride upon, resulting in a heavy and cumbersome tool. Tool Trolley chose a high tensile strength aluminum alloy that was heat treated for hardness to achieve the optimum performance.
The shape of the guide rail affects its flex characteristics. The double rolled edge rail of the Universal Trolley results in a much stiffer rail then a flat, rectangular or angle aluminum rail. The rolled edges effectively distributes the bend forces across the width and height of the rail comparable to a solid rail of the same thickness. The Universal Trolley guide rail has the flex characteristics of a much thicker rail but without excessive weight and bulkiness.
Profile distortion occurs when a guide rail is clamped to a bent or warped work piece. Unfortunately not all woodworking materials are flat, straight and square. Go to a construction job site and look at the stack of sheeting laid out on 2 x 4's on the ground. The stack takes the profile of the ground that it is resting on. Unlike a rectangular or L-shaped rail, the double tubular shaped edge design does not distort when clamped on a bent or warped work piece resulting in a non-binding-straight cut.
The application or type of operation that is being performed with a clamp-on-guide is another consideration that must be taken into account. A cabinetmaker that is joining two boards together wants no gap between the boards that would contribute to the weakness of the joint. A carpenter sheathing the side of a house can easily tolerate between 1/8" to ¼" in the accuracy of his cut. The Universal Tool Trolley flex testing results were an impressive maximum displacement of 0.027" at a 100" span between clamps and 0.003" when using a 50" section of rail or when using a rail stabilizer, satisfying both the cabinetmaker and the rough carpenter needs.
The following table and graph summarize the Duplex Rail Flex Test results: Click on the image to open Adobe PDF version of the chart or table
