starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: piaras]
#5266911 - 06/11/12 06:46 PM
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Every where else any bolt over 1" will not have full threads.
yes, that's what I'm finding, today I was in the US and found full threaded bolts and all metal locking nuts at a True Value Hardware store, so now I have a source 
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thinairart
professor emeritus
Reged: 11/18/09
Loc: Denver, Co
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Re: 14" Hubble Optics Project
[Re: starman345]
#5295733 - 06/30/12 01:01 AM
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A few posts back Careysub offered an example compression spring for use in your mirror cell. I've been meaning to change out my weaker springs to fix slight collimation drift near the horizon & zenith, so I gave that recommendation a try.
Here is the link to that spring: http://www.mcmaster.com/#catalog/118/1220/=i73oua
I installed the new springs this week and am happy to report they work great! The spring has a 1" diameter so it fits nicely between the steel bars of the mirror cell the & 1" box channel I used for my tailgate rungs. And my collimation drift has been solved, with no appreciable drift between about 10 - 80 degrees.
So if your looking for a good spring to support the Hubble 14" mirror, something similar should work great.
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: thinairart]
#5296271 - 06/30/12 12:04 PM
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Hi Aaron, I ordered those springs Careysub suggested and McMaster-Carr sent them and just before they were delivered they issued an intercept to return to sender. A subsequent e-mail explained they could not deliver "Due to the complexity of U.S. export regulations"....even though I had supplied my US shipping address, I thought it was a bit strange but they can choose their customers.
I've been searching other sources for compression springs but can't seem to find anything close to Careysub's recommendations.
The part number on McMaster-Carr is 9657K323. Anyone know where I can get that spring or something close to it?
Aaron, are you using a sling or did you change your cell setup?
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m. allan noah
professor emeritus
Reged: 08/14/09
Loc: Virginia, USA
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Re: 14" Hubble Optics Project
[Re: starman345]
#5296369 - 06/30/12 01:27 PM
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Walk into a locally owned transmission rebuild shop, and ask for springs. They usually throw away a couple dozen on any rebuild.
allan
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thinairart
professor emeritus
Reged: 11/18/09
Loc: Denver, Co
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Re: 14" Hubble Optics Project
[Re: m. allan noah]
#5297963 - 07/01/12 02:04 PM
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That is pretty weird regarding exporting compression springs, I never would have guessed that would be a problem.
I'm still using a sling for support, but I recently changed it out for a 2" version. I had been using a 1.5" nylon strap that I just didn't feel had enough coverage on both layers, and was drawn in a bit in the middle where the gap is. So if you are going to go the sling route as well, I'd recommend a 2" strap to ensure both layers are well supported.
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: thinairart]
#5301095 - 07/03/12 06:40 PM
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I bought a piece of 1.5" webbing a week ago but since changed my mind and now am going to go with 45 degree supports....I've changed my mind several times so that may change as well 
Pinbout(Danny) made the suggestion to use a piece of laminate with the Hubble mirrors and it sounds like a good idea. I took a look at some kitchen countertop laminate I had left over from a kitchen re-build and I think it would work very well, almost weightless and very strong. Probably need to spot glue it to each plate but it would open the possiblity of using a cable sling and wouldn't sag in the middle between the plates like you say happened with your 1.5" webbing.
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thinairart
professor emeritus
Reged: 11/18/09
Loc: Denver, Co
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Re: 14" Hubble Optics Project
[Re: starman345]
#5301624 - 07/04/12 01:03 AM
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The laminate option sounds very intriguing. I'd definitely be curious how that works out. Where are you with the dimensions for the mirror box, have you decided on a depth yet?
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: thinairart]
#5301790 - 07/04/12 06:15 AM Attachment (39 downloads)
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I haven't done any torque equations yet, I'm still working on the secondary and the mirror cell at the same time. I"ve got to stop reading here, as soon as I decide on one way to do something, I read some other great way that is more appealing and change the plan, never get anything completed that way.
For the focuser board I used your method of dowels to anchor it to the rings, I don't think I'll glue it at all as it is very sturdy as is and plus I can break down the secondary cage at any future date for modifications.
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5301792 - 07/04/12 06:16 AM Attachment (37 downloads)
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Focuser board installed.
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5301793 - 07/04/12 06:16 AM Attachment (46 downloads)
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Mirror cell, a work in progress..
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5301795 - 07/04/12 06:24 AM
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Forgot to mention about the laminate idea, I was thinking a strip 1.5" wide to span the two plates and long enough to cover at least 180 degrees of the mirror perimeter. The only drawback I can see is with the laminate in place air flow will be impeded, so I don't know how that will impact cool down. I guess holes could be drilled in the laminate to help that, but that would probably weaken the laminate....for now I'm going with the supports at 45 degrees
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thinairart
professor emeritus
Reged: 11/18/09
Loc: Denver, Co
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Re: 14" Hubble Optics Project
[Re: starman345]
#5302311 - 07/04/12 02:11 PM
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Nice job on the secondary cage, looking very sturdy. I was also planning originally to avoid gluing the focuser board into place so I could also disassemble later on if needed. Unfortunately, I had some minor gaps in my measurement, so the fit was not tight enough and I had to lock everything into place with glue. Your assembly looks very tight though, so I'm sure you won't have any issues skipping the glue.
Nice triangles as well on the mirror cell, I'm interested to see your two-layer cell come together. I'm still undecided if I should rebuild my cell, or save the cell rebuild for a future scope project. Now that I have a proper 2" sling in place, I'm planning to perform some star tests near the horizon and see what kind of strain I see from the sling. With these sandwich mirrors it is kind of a mystery how well a sling performs compared to a regular mirror. The sling contacts both layers, and hopefully the average of those points is fairly close to the actual COG of the mirror. When your looking at building your edge posts, keep in mind as well that at least with the 14" I had from Hubble Optics, the layers were not exactly the same size (1/16" difference between top/bottom). So the edge post will need to be constructed in such a way where it can make contact with both halves. Ah the joys of a sandwich mirror!  Economical and lightweight, but in the area of edge support not nearly as straight forward as a typical mirror of the same size.
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: thinairart]
#5360108 - 08/09/12 03:16 PM Attachment (42 downloads)
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After a long hiatus, I'm back at it. Yesterday I received this in the mail(Thanks Ralph):
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5360113 - 08/09/12 03:18 PM
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Having sold my only telescope on Sunday, I don't have a way to try my new toy  So now I need to get back to building....
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5360118 - 08/09/12 03:21 PM Attachment (31 downloads)
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I decided on a triangle type cell, almost entirely copied from Reiner Vogel's web page..he has some excellent pictures and explanations on how things work there.
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5360125 - 08/09/12 03:24 PM Attachment (30 downloads)
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I used supports at 45 degrees. Using dowels initially posed a problem because the upper plate(mirror) is a bit larger than the lower plate. I drilled the upper dowel in the center and placed the uppper plate in contact with it. The lower dowel was drilled off-center about 1/8" and rotated into contact wtih the lower plate. Bolts and star lock washers locked each dowel in place. It seems to hold ok.
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5360130 - 08/09/12 03:25 PM Attachment (25 downloads)
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With separate dowels for each plate
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5360134 - 08/09/12 03:26 PM Attachment (31 downloads)
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Overall view
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starman345
Wait, I'm Thinking
Reged: 07/06/10
Loc: New Brunswick, Canada
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Re: 14" Hubble Optics Project
[Re: starman345]
#5360136 - 08/09/12 03:27 PM Attachment (27 downloads)
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And again
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sopticals
sage
Reged: 03/28/10
Loc: New Zealand
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Re: 14" Hubble Optics Project
[Re: starman345]
#5360513 - 08/09/12 07:13 PM
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Hi Brian, 
Your project is coming on nicely. Nice eyepieces. You will be wanting to press on to the finish mark now that you dont have a scope to try out those oculars. I cant imagine being "scopeless"  . Continuing to watch with interest.
Best regards
Stephen.
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