[ATM] Wire Spider Vibrations

[Martin Cibulski]

Jack,

in my opinion you should use FOUR vanes instead of three.

If there are only three vanes, even if the connections of the wires are
away from the optical axis and the wire triangles are wider, rotational
vibration around the optical axis is still possible.

Regards,
Martin Cibulski
http://www.martin-cibulski.de/atm/

> From: "Jack Swaton @ Starry Host" 
> Subject: [ATM] Wire Spider Vibrations
> To: "'ATM List'" 
> Message-ID: <006e01c7189c$604f4100$0402a8c0 at dell1>
> Content-Type: text/plain; charset="us-ascii"
> 
> My scope is nearing completion but my wire spider produces very rapid
> micro-vibrations for minutes. I can't post photos at the moment, but
> the basic design is 3-vane with two support wires. That is, for each
> of the three wires, I use a piece of wire that starts around a screw
> on the secondary mount and then travels to the OTA where it feeds
> around a cup hook and then back to the same screw it started from.
> There is about an inch between the top wire and the return bottom wire
> on this screw. The whole route ends up making a long, narrow triangle
> between the spider hub and the OTA. The upper and lower portions of
> the wire is separated by a piece of plywood which is actually part of
> the secondary mount.  Each of the three wires go out at 120 degree
> angles to the OTA.
> 
> In an attempt to dampen the vibrations, I connected a single wire from
> the secondary mount to the OTA. These two wires form a 180 degree line
> across the OTA.
> 
> So I'm really asking what the basic design parameters are for a wire
> spider.
> I've studied the images I've found on the Internet, but I must be
> missing the engineering for stability and dampening.
> 
> Thanks,
> Jack