The original concept of this project was to use 3D printing to produce a frame without the need for a jig or fixture. I have since come to understand that it would not be possible to construct a frame to the accuracy I require in regards to the placement and alignment of the pivot hard points.
Also, the exact geometry of the frame is not published information. Seat tube angles, head tube angles, top tube lengths can be found, but important details like seat tube/BB offset, head tube height, shock droop when published data was recorded, or even HOW a standard dimension like top tube length is taken are somewhat vague and need to be found empirically. That is not to mention pivot size/location for the rear suspension.
So, I decided to make a simple and cheap frame fixture integrating extruded aluminum and 3D printed parts. The fixture would be used to verify my frame geometry to the original Rocky Mountain frame... almost like a trial&error test bed... and then hold my frame as I construct it from carbon composite.
Here shows the main spine of 80/20 style aluminum framing with the first printed tests of the frame geometry I have in CAD. This was to validate seat tube angle and offset to BB.
Closeup of the BB cups and cradle.
Is the pivot in the right place?
I used these brass threaded inserts extensively as they are cheap and easy to install in printed parts without drilling the hole. Metal threads in printed parts for repeated use.
Clamping the seat tube illuminated some error I had in the BB/pivot measurements.
First try at the pivot location in the seat tube was off.
Second try hit.
Measuring heat tube height above BB.
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