Custom truss rods for binoviewing?

[Ships and Stars]

Hello everyone, sitting around dreaming, this time about making a second set of shorter truss rods for binoviewing without a glass path corrector / OCA so I can get the widest field / lowest mag possible with my WO binoviewers. I thought about this some time ago, but didn't chase it up much.

I simply can't afford new Binotron 27s with power switch at the moment, or some crazy Sieberts, or I'd just go for those and make life easy. Someday soon perhaps. But in the meantime...

My dob has 6 truss rods that are 1775mm long from end to end, including the ball ends (see photo).

The ball ends are a simple design, a 25mm ball end sits on a 16mm dia shaft that has a 30mm pedestal which sits atop 30mm tubing. There are flats machined on the 16mm shaft for a 14mm spanner, presumably they screw in but are on really tight, possibly glued. I haven't really tried to unscrew one yet but did briefly pop a spanner on one. They are tight.

A few questions if I may:

1 - Are the 25mm ball ends on a 30mm dia pedestal something someone could 3D print out of hard enough material? I'd need a dozen in total and there must be some threads hidden in the end of the tube where it attaches. Alternatively a machine shop might be able to turn some out of alloy, or I could find something online from some industrial application etc and use those. 

2 - If my WO binoviewers have a light path of 100mm, then presumably the new truss rods would need to be 1675mm instead of 1775mm to focus without a GPC or barlow in an f4 dob? I should be able to find 30mm alloy tubing fairly easy.

3 - Would I still lose some brightness by not capturing the full light cone from a fast dob? For instance, the Binotron 27 SS has an optional 45mm OCA which captures the 'fast' light cone from a fast dob as explained here. It seems to me the bog standard WO BV nose without a GPC would be in the same position as any 1.25" eyepiece and thus capture the full cone of light... 

4 - What detrimental effect(s) would moving the secondary closer to the primary have on reduced aperture, i.e. would the secondary mirror block more light presumably? Would a smaller secondary be the 'perfect' set-up for a truss dob modified for binoviewers? I doubt I'd ever replace mine, just curious what impact there is upon performance.

Any thoughts welcome, or if by some chance someone has some Binotron 27s with the powerswitch they want to part with, please drop me a line. 

 

Cheers.