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Sunday, April 6, 2025

Making Slow Motion Control Brackets From Carbon Fiber Composite

This has turned out to be more difficult than I thought, at least using the dimensions I used for Delrin.  The strategy I used for Delrin needed two Delrin sheets 3/8" thick, one of which is tapped.  The CFC strategy requires through holes with hex nuts on the far side.  This extends the vertical part until it runs into the motor mount.  I cannot reduce the thickness of the vertical part much because I need to make tapped holes about .16" ID in the other dimension. 

Another strategy is to use 1/4" thick CFC with hex nuts epoxyed into hex holes.  (I still need to make an example to veridy that i can do this.  Thanks to all who helped me with the math to write a program that cuts hexagons.) This reduces interference with the motor mount.  A 1/4" thick CFC sheet weighs slightly less than Delrin (1.6 g/cc vs. 1.4 g/cc).  It is also cheaper than 3/8" thick CFC.

This strategy also removes one interface block that requires machining to dimension and through holes.

I started out planning to make this thing almost entirely of 3/8" thick CFC sheet.  This stuff is so stiff and the loads are so low that I can use 1/8" sheet for many parts.  This reduces cost and weight.  Some parts still need to be 1/2" thick to hold the hex nuts for blind hole threading.

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