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10inch F4 Serrurier Truss - Build Process

Design Concept

I Love Building things and after playing around with an 8 inch reflector, I decided it was time to move up. I love fast telescopes, so decided to get a 10inch F4 and a matching secondary from Orion Optics in the UK. 

I got the mirrors in March 2012, but had still not yet finalized the design for the OTA. 

Inspired by Rolf Olsen's 10inch F5 Serurrier truss, I set out to build my own 10inch F4 truss. 

The design principle of a Serrurier - the sag in both halves are the same, really got my attention and I set out to design it with as many carbon Fibre components as possible.

Design Principles

The primary factors were - 

Weight - Needed to work within the limits of my HEQ5 Pro Mount - Max 13Kgs. 

Rigidity - Being F4, it needs to maintain collimation at all positions

Thermally inert - Needed to have as minimal expansion or contraction as possible

I therefore decided to use 16mm carbon fibre tubes for the truss nodes, and  the mid, upper and lower sections out of 18mm Plywood.

I deviated from traditional truss OTA's in that I changed the usual square mid section to an Octagon, inspired by the Officina Stellare RC's.

The Octagon causes the trusses to form cones and these are more rigid than parallel trusses.  

As the angles were complex, I designed an elbow joint using Aluminium "U" Sections. This allowed the truss node to move freely in 3 axes.

Inspired by Rolf Olsen's wire spider, I set out to design the spider using guitar machine heads and E strings. Difference being in the central secondary holder which I completely re-designed to be a pull type rather than push, which made it completely toolless and easy to collimate.
Major adjustments are made with the strings to center the secondary, and minor corrections are made with the screws.

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