Re: [ATM] wire spiders

["Alan Scott" <alanne1956@hotmail.com>]

I have been trying to figure out how to do a wire spider for a 16". The 
requirements are slightly different than the 12". I am going for 8 trusses, 
to allow the mirror box to be smaller. I want to also get rid of defraction 
spikes around stars, if possible. So, starting from the 3 leg spider on the 
original scope http://www.xmission.com/~alanne/DS3SecondaryCage.html (open 
up the lower, right picture), I plan to do the following. There are 4 
threaded brass rods, and 4 holes for wire attachment through each washer. 
One wire will be threaded around the top of the spider, and a different wire 
will be threaded around the bottom of the spider. Wrap the end of the wire 
around one of the brass rods, go to a center washer hole, then go back to a 
second threaded rod, back to the next center washer hole, back to a third 
threaded rod, etc. Do one set on the top, one on the bottom. The wire will 
look like a series of "V"s, with a base of a V at the brass rod, and also 
the base of a different V at the washers. Now, as I am threading the wire 
through the holes, if possible, put a wrap of wire around itself every time 
I go through a hole. Otherwise, I will try to put a dob of solder on the 
wires as they go through the holes.

The advantages are that the wire shouldn't move at all (durring columation), 
and should have absolutely no spikes around stars.  We will see if it is 
even manufacturable.

By the way, I worried about one of the wires breaking also on the 12".  
Turns out that I would have to have all three wires break at the same time 
to give me trouble.  Frankly, I am more worried about droping an eyepiece 
onto the secondary, or a bolt.  And yes - I DID drop an AA battery onto the 
mirror once (from about 6").  Didn't seem to do any damage to the mirror, 
did take the paint off of the trunk of my car from my swearing!

alan
http://www.xmission.com/~alanne/DS3Main.html
http://www.xmission.com/~alanne/DS4Main.html




>From: "Terin Lyr D'Amico" <terin.damico@verizon.net>
>
>John,
>
>
>-----Original Message-----
>From: John Sherman [mailto:atm@mail.johnspics.com]
>
>
>Hi Terin,
>
>Yes, I've seen it, thank you. He provided that link a couple of months ago
>when the wire spiders came up. I really like the way he designed and built
>that spider. I think I'm going to try to copy it. My main worry is what
>happens when a wire breaks? They say all that happens is that the secondary
>assembly sags down to the edge of the tube. At least one wire supposedly
>still prevents it from landing on the primary. But what if the secondary
>mirror gets damaged from hitting the inside of the tube? Wouldn't want 
>that!
>

_________________________________________________________________
Is your PC infected? Get a FREE online computer virus scan from McAfeeŽ 
Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963

_______________________________________________
ATM mailing list http://www.atmlist.net/