Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1985
Loc: Prescott, AZ
|
|
Today I was paging through McMaster-Carr plastics and was a bit overwhelmed by the number of choices I might have for an upper cage material.
What is the favored material these days for an Obsession-style upper cage? Is Kydex still King?
Note that I do have a large quantity of flocking paper, so I really don't need a material with a matte finish. Really, I could use anything that is somewhat rigid and not too heavy.
--------------------
Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
|
llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 12939
Loc: Amargosa Valley, NV, USA
|
|
I used two cardboard writing tablet backs taped together and painted. I attach it with velcro so it can be removed and installed easily. Works great!
Edited by llanitedave (09/04/09 02:14 PM)
|
Zoomit
sage
Reged: 12/04/06
Posts: 282
Loc: Tehachapi, CA
|
|
Me too! I'm renovating my TeleKit UTA and am in search of replacement material. Isn't the major downside of Kydex is the potential to deform when heated by the sun?
--------------------
Brandon
Newts: 18" f/4.6; 7.4" f/6.4
EPs: TV 26Nt5, 13E, 3-6NZ; Antares 2" 1.6x, Paracorr
Bino: 15x70, 12x50, 6x30
|
polaraligned
sage
Reged: 12/26/08
Posts: 228
Loc: P. R. of New Jersey
|
|
I thought the biggest complaint about Kydex was that it expanded and contracted too much. ABS is a better choice if I recall correctly.
|
artmustel
super member
Reged: 05/30/07
Posts: 128
|
|
I used Hobby Lobby Fun Foam, flat black, only $0.79 a sheet (it took like 3 sheets for my 12.5" Obsession style dob UTA). Excellent, cheap, no complaints about it. Who needs kydex???
|
jayscheuerle
Post Laureate
Reged: 01/16/06
Posts: 4070
Loc: S. Philadelphia, PA
|
|
Kydex warps in the sun and is unnecessarily heavy.
--------------------
Fight indignorance!
The Green Goblin - 12" of dobsonian excellence!
The PortaBowl-a $100 4.5" f/8 ball-scope YOU can build!
Eero2-a 6" f/5 ball-scope you probably can't. 
|
dave b
Post Laureate
Reged: 05/10/05
Posts: 3530
|
|
kydex melts in the hot car, abs cracks in the cold
aluminum is nice and lightweight, but can dent if struck sharply, formica is a little heavier but lots of cool colors
--------------------
dave bonandrini
30" f/5.2 Dobsonian
President of GCAC
Astromart Moderator
|
Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 965
|
|
I got lucky once, and bought many 8 1/2 x 11 transparent Lexan sheets. 1mm thick. I do not know their original application. Note that they are the same size as a standard sheet of typewriter or copier paper. They have solved many problems, but I have not tried it for this thread's
application. I do not have an open tube Newtonian at this time. Would such material help here? It is certainly tough, and can be cut with metal snips or the heavy duty scissors at Harbor Freight.
|
Zoomit
sage
Reged: 12/04/06
Posts: 282
Loc: Tehachapi, CA
|
|
clean Lexan--that's interesting. You could roughen up the inside and paint it black. The outside might have a glossy black appearance. That might look good!
Here's some 1/16" thick stuff available from McMaster-Carr (I love them!) Polycarbinate
--------------------
Brandon
Newts: 18" f/4.6; 7.4" f/6.4
EPs: TV 26Nt5, 13E, 3-6NZ; Antares 2" 1.6x, Paracorr
Bino: 15x70, 12x50, 6x30
|
Stefan Rostyne
Pooh-Bah
Reged: 10/19/04
Posts: 1009
Loc: Assenede, Belgium
|
|
I use thin wood veneer, and seal it with a few coats of epoxy to make it durable. I used to paint the inner side with a mix of schoolboard black paint and sawdust. Recently, I use flocking paper.
--------------------
Stefan Van de Rostijne
4.5" F4.5 newt 5°widefield/finderscope
8" f/5.6 travel dob
old 12.5" F5 dob (used to look better...)
30 cm f/30 Classic Cassegrain (polishing primary)
23" f/4 dob project
|
Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1985
Loc: Prescott, AZ
|
|
Thanks for all of the ideas! It looks like a good list:
ABS - Low density (.037 lbs/sq. ft), but can crack in cold.
Fun Foam - I need to get a look at this.
Metal - McMaster-Carr has several different metal options. Perforated, Mesh, and shim stock. I was wondering how well .005" stainless steel would hold up? Would it tear easily? A bit pricey, but interesting.
Lexan - Interesting, but the options I saw were all clear. So, without further treatment one would be looking at the adhesive backside of flocking paper. Density about .0435.
Formica - Lots of color options, easily available. A bit heavy also.
Wood Veneer - On the Aircraft Spruce website I found mahogany veneer, 1/16" for under $30. It will require more treatment, but this could be the winner. I need to think on it over the weekend.
--------------------
Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
|
Achernar
Postmaster
Reged: 02/25/06
Posts: 5024
Loc: Mobile, Alabama, USA
|
|
Very nice, I like how you did your light baffle. But I'm sure you paid a few bucks for the veneer. I made my own light baffle from beveled slats of thin, lightweight plywood and used painter's tape to hold them together. Glue was inserted between the slats, and the assembly was wrapped around a former made from the cutouts left behind when I cut out the rings for the upper cage. After sanding I painted the outside with glossy black spray paint, the inside with flat black paint mixed with fine sawdust. Yes it's heavier than many would care for, but I can attach a finder scope to it at a convenient location, which is exactly what I intend to do. The narrow board will hold a Telrad, and when the telescopes is finished the whole upper cage will go into a wooden case I'm planning to build for it.
Taras
--------------------
15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
|
Achernar
Postmaster
Reged: 02/25/06
Posts: 5024
Loc: Mobile, Alabama, USA
|
|
This is how the baffle started out.
Taras
--------------------
15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
|
Zoomit
sage
Reged: 12/04/06
Posts: 282
Loc: Tehachapi, CA
|
|
Quote:
Fun Foam - I need to get a look at this.
A few weeks ago, I bought an assortment of Fibre-Craft 12"x18" sheets of craft foam. I wanted the black, and got 2 sheets, but had to buy the 10 other sheets as well. See here to buy individual sheets. It appears relatively durable, but soft of course and not structural in any way. The surface would take a flat black paint really well, I'd think, as it has a fine cell texture.
I just measured my assortment, without packaging. It weighed 15 oz on my kitchen scale. That's 18 sq ft, or 0.052 lbs/sq ft. I haven't found it in larger sizes, which I want to use to minimize joints and since my UTA needs 13.5" high sheets.
McMaster-Carr has this stuff that might be worth a try.
Tear-Resistant Polyethylene Foam, Plain Back--Firm, Thin, 1/16"x36"x54" Only $8 for large sheet too.
--------------------
Brandon
Newts: 18" f/4.6; 7.4" f/6.4
EPs: TV 26Nt5, 13E, 3-6NZ; Antares 2" 1.6x, Paracorr
Bino: 15x70, 12x50, 6x30
|
Zoomit
sage
Reged: 12/04/06
Posts: 282
Loc: Tehachapi, CA
|
|
My math says that Polyethylene foam is 0.021 lbs/sq ft. Certainly lightweight but durable in this application? Don't know.
--------------------
Brandon
Newts: 18" f/4.6; 7.4" f/6.4
EPs: TV 26Nt5, 13E, 3-6NZ; Antares 2" 1.6x, Paracorr
Bino: 15x70, 12x50, 6x30
|
artmustel
super member
Reged: 05/30/07
Posts: 128
|
|
The fun foam is an excellent substitute, very cheap and easy to find. I sprayed the interior with flat black spray, although it is not needed actually. Of course it is soft, not structural...but you won't need that since the rings and trusses give a very solid structure. Another benefit: it is almost weightless, easy to attach with contact cement, and you can cut or shape it with scissors.
|
rboe
Reged: 03/16/02
Posts: 45330
Loc: Phx, AZ
|
|
I went the WilsonArt route (similar to Formica). The inside is pretty rough and takes the flat black very well - and a ton of colours and textures to choose from.
It will crack, a bit more difficult to work with and it's not cheap. Nor is it really expensive. 
Epoxy needs to be varnished with something that has UV inhibitors to protect it from the sunlight or it will degrade. But over wood like that it is drop dead gorgeous. Wow!
--------------------
Ron
NS11GPS
Pronto
16" dob
15X70 Obies
|
dave brock
super member
Reged: 06/06/08
Posts: 164
Loc: Hamilton, New Zealand
|
|
I went the Formica route as well. Didn't find the weight a problem and easily worked (I do work with it for a living however).
Dave
--------------------
20" homebuilt truss dob
6" watson refractor
|
Jim Moscheck
Carpal Tunnel
Reged: 01/08/07
Posts: 1619
Loc: Under the SE Michigan lightdom...
|
|
Well, in defense of Kydex my scope was fitted with some left over Kydex from my friends scope build. I left the Kydex in the cold garage overnight(it was February IIRC) and brought out the warm UTA frame from the house and used the directions in the Kreig and Berry book. After three years not a bit of a problem with it and it looks as good as the day I cut it, if it gets warm it expands a bit, but since I put it on cold it just gets tighter. It's shiny on the outside and dull on the inside. If I ever do have to replace it I have some Ebony star laminate left over from another project so even then it won't cost me anything and think it would look pretty good, too.
--------------------
Jim Moscheck
Ford Amateur Astronomy Club
ATM truss dob
Stevens 14.5" f4.3
"A mind is like a parachute. It doesn't work if it's not open." - Frank Zappa
|
Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1985
Loc: Prescott, AZ
|
|
Nice looking scope Jim! Is your focuser board Zebra wood?
--------------------
Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 