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droid
rocketman
Reged: 08/29/04
Posts: 4041
Loc: ohio
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I live in north east Ohio, Im looking for a 14 inch min. peice of tubing.Approx. 6 feet long.
Where does one find something this big???? home depot does not stock it, neither does Lowes.Ive looked on the net to no avail.
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12 inch Truss Reflector "John"
102mm Celestron C102HD
Tasco 7TE5 60mm Classic
Tasco 9TE5 60mm Classic
Celestron Ultima 2000 SCT
Remains of an 8 inch dob
Celestron Comet catcher(orange tube)
1960 Edscorp Space Conquerer 6inch f/8
10x50 Bushnell Binoculars.
11T 4.5 inch Tasco reflector Lunograsso?
60mm Telescope Club
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1_old_dog
sage
Reged: 09/07/07
Posts: 435
Loc: Smoky Mnts
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That's huge. Have you tried a fabrication shop that does duct work?
od
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old stuff but good stuff
http://chu65nang67.us/nam/vietnam.html
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droid
rocketman
Reged: 08/29/04
Posts: 4041
Loc: ohio
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would duct sheet metal be strong enough ?????
No I havent to be hones Id thought duct pipe to be to flimsy for such a large peice of glass with mirror cell.
Of course I have no experience in these matters so Ill take yalls word for it, 
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12 inch Truss Reflector "John"
102mm Celestron C102HD
Tasco 7TE5 60mm Classic
Tasco 9TE5 60mm Classic
Celestron Ultima 2000 SCT
Remains of an 8 inch dob
Celestron Comet catcher(orange tube)
1960 Edscorp Space Conquerer 6inch f/8
10x50 Bushnell Binoculars.
11T 4.5 inch Tasco reflector Lunograsso?
60mm Telescope Club
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1_old_dog
sage
Reged: 09/07/07
Posts: 435
Loc: Smoky Mnts
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well I was just thinking out loud but most fabrication shops have sheet aluminum in various dimensions that can be rolled. worth a try
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old stuff but good stuff
http://chu65nang67.us/nam/vietnam.html
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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Right now I'm up against the tube question myself with my first attempt at building a telescope.
I need a 6.625" OD thin wall tube (aluminum electrical conduit is too thick, as well as WAY too heavy!). It seems that my only way to go is to have a tube fabricated out of sheet aluminum... or, horror of horrors, use PVC sewer pipe!!!
I'll give you an idea of what to expect going the fabrication route... for a 38.375" long tube of .125" aluminum, with a welded seam, the three estimates I've gotten so far (in southern Wisconsin) are all in the $140 to $175 range!!! Material thickness isn't a major factor here; thick or thin, the estimates are all running about the same.
The biggie is labor on this, and all three estimates are based on estimates of about roughly 2 man / hours to produce it.
At this rate, I'm almost tempted to go down to Harbor Freight and get a machine to make it MYSELF! In the end, that would probably wind up being cheaper!!!
Mr. T.
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Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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HandyAndy
professor emeritus
Reged: 01/11/08
Posts: 650
Loc: West Midlands and around
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Hi,
The cost of having an aluminium tube made with no seam is the welding. They have to make a Jig to hold the seam in place which is labour intensive.
Get someone to roll the tube for you only.
You can join the tube using a flat bit of alloy strip inside with a few bolts and some waterproof PVA OWHY to seal the join. If you are going to flock or sawdust the inside of the tube I would put a couple of lengths of wide masking tape over the join. Once it has been left a few days it sets on. A bit of gloss paint over will seal it from moisture.
If you can only find some flimsy tube then put some wood or alloy stringers up the tube inside. Mount the mirror cell and spider to the stringers. You can get some 1" by 1/8" alloy rolled for end rings, inside supports between the stringers for the focuser, and a slipper ring if you want a rotating Newtonian OTA. Bolt the rings to the ends of the stringers.
Cheers. Andrew.
--------------------
Monarch 8x42, Zeiss 10x50 WA
10mm F2, Pentax 60mm F5
City: 7" MN78: MK4#2, 10" F6.3: MK4#1, 16" F5 ParaCorr
Country: 8" VISAC: (GP2)
Car: 6" F5 MPCC: SP, 5" 127mm F7.5 (GP2)
TV 55mm, Paragon 40mm, UO Pretoria 28mm
B&L 32 Pl, Clave's 25, 8, 6, 2x
Hyperions 5, 8, 13, 17, 24, 31
Nagler1 9mm, Meade 14mm 4000 UWA
Antares 1.6x, 0.7x, 0.5x
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polaraligned
sage
Reged: 12/26/08
Posts: 229
Loc: P. R. of New Jersey
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Quote:
I'll give you an idea of what to expect going the fabrication route... for a 38.375" long tube of .125" aluminum, with a welded seam, the three estimates I've gotten so far (in southern Wisconsin) are all in the $140 to $175 range!!!.
1/8" aluminum is way too heavy for a 6" dia tube. You could not even get it rolled and seamed very smoothly. You need to get your tube from:
http://www.hipco-ne.com/scope.htm
They sell shorts of aluminum irrigation pipe.
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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Hello Andy!
>>> The cost of having an aluminium tube made with no seam is the welding. They have to make a Jig to hold the seam in place which is labour intensive.
Get someone to roll the tube for you only.<<<
Thanks... that's a VERY useful bit of information!
In every design, eventually there comes compromise... and the nice, neat welded seam appears to be biting the dust on this one.
Perhaps it would be helpful if I outline just exactly what I'm trying to do here.
Instead of saying I'm BUILDING a telescope (an idea I've toyed with for a very long time), it might be more accurate to say that I'm trying to REDESIGN and REBUILD a telescope; convert a sow's ear into a faux silk purse, as it were.
Enter EBAY... America's overstuffed attic!
For the last couple of weeks, the folks over at Galileo Telescopes have obviously been parting out their battered display models from the trade show circuit and scopes that got creamed in shipping, and putting the debris on EBAY.
Among the stuff that appeared was an intriguing package; the cell, mirror, spider and diagonal from one of their FS-135 telescopes (mirror is 135 MM with an 1100 MM focal length, about an F 8.1). The whole package went for the princely sum of $40.00.
At the same time, I also grabbed a so-so GEM, and a declination drive motor, also for bargain basement prices.
Armed with a copy of STANDARD HANDBOOK FOR TELESCOPE MAKING, and using the NEWT telescope design software, I think I've been able to reverse engineer this FS-135 beastie.
Galileo is, I gather, just a few cuts above the Toys-R-Us telescopes. However, the cell and spider seem to be fairly substantially made. Mirror grinding and polishing are no doubt machine mass produced; it may or may not be too bad. That remains to be seen; if testing shows that it's too outrageous, the primary is at least a rough formed hunk of glass that can be stripped of coating and refigured into something better.
I'm envisioning an El Cheapo telescope with minimal effort, and hopefully MY engineering and care in construction will cut less corners cost wise and be better than the Galileo assembly line product.
Anyway, because of the cell and spider, I'm married to a 6.625" diameter tube on this project. I haven't been able to find out for sure, but I get the impression that Galileo based their telescope on PVC sewer pipe; an offense to the soul of any engineer, but a delight that warms the cold hearts of the front office Bean Counters, who are only concerned with the unit price of every telescope going out of the door! 
In any case... for this telescope design novice, job #1 at this point is to come up with a tube design with enough rigidity to hold the optical chain in some sort of alignment, and stiff enough to make vibration from external stimulus fall into the high frequency (and small amplitude) realm.
Maybe I'm full of fecal refuse on this... but so far it's been an interesting project for a Newbie.
Mr. T.
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Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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Hello Polaraligned!
Thanks for the link... but I've been over the Hastings Pipe Co. site a number of times. It's been disappointing.
It seems that irrigation pipe is unusual, in that it's diameter is based on an OD figure instead of an ID; it doesn't conform to what seems to be an industry standard OD of 6.625".
When Hastings says "6 inch pipe", they mean 6" OD.
BTW... thanks for the tip on .125" wall thickness being excessive.
I rather estimated it WAS, but there are a few things I'm trying to balance here, and I was going on gut instinct.
First factor: adequate amounts of both longitudinal and cross section rigidity. Longitudinal to keep the optics in alignment, and cross section to give it resistance to radial crushing forces applied by a mounting based on large diameter hose clamps.
I suppose .094, or even thinner, would be adequate on that score, with possible reinforcement bands epoxied on around the clamping areas.
Second factor: sufficient mass to tend to damp vibration induced by breezes, camera shutter tripping, etc.
Thanks again,
Mr. T.
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Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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Spoonsize
Vendor/Clothing
Reged: 08/27/04
Posts: 3296
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I've no idea how or if it would work, but how about looking up a heating and air conditioning outfit and getting a price on spiral wound ducting? I see it made with galvanized and aluminum at various diameters and understand it is now made with pvc.
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Steve Durham
www.margesmonograms.com
(Marge made me do it)
"Nobody get's in to see the WIZARD, Not Nobody, Not Nohow"
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Mirzam
super member
Reged: 04/01/08
Posts: 118
Loc: Lovettsville, VA
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Sonotube comes in larger sizes than those typically found at Home Depot. (Or at least it used to). I once had a 16 inch sonotube that I used for a 14" scope. Try to find a sonotube distributor and bring your saber saw if you don't want to carry a really BIG piece.
Jim
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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Another idea on tube fabrication. It didn't work for ME, but it might work for someone else.
I have a buddy who is at Embry Riddle down in Florida. For those who don't know, that's a school that gets people ready to take the Federal Aviation Administration's "A and P" (airframe and powerplant) mechanic's licenses. Basic aluminum fabrication is a major part of the curriculum... and the students have access to metalworking equipment we can only dream about.
He told me that shearing a sheet of aluminum and rolling the tube I have in mind would be about 15 minutes work, and throw in another half hour for welding it and cleaning up the seam by grinding.
It didn't work for my tube because he's completed the course, and now has his A&P certificate; thus he no longer has access to the shop and equipment at the school. The place where he's now working, patching up hurt airplanes, mainly replaces whole subassemblies that they get direct from the manufacturer; they do virtually no metal fabrication, and thus don't have the facilities for it.
If there's a facility near you that does major aircraft repairs, it may be worth a try as a place to get an oddball tube fabricated.
BTW, my buddy also gave me a couple of tips on how to possibly get the cost of fabricating my tube made more cheaply.
First off... when you go to a local metal shop, bring your own material for the tube. If you don't, you're giving them the opportunity to scalp you on it; the usual justification given is that for YOUR job they'll have to buy a whole sheet of aluminum, and those are pretty huge.
Next... a bit of psychological warfare here. If you want a welded seam (like I do), break up the fabrication job between more than one shop; have the tube rolled in one place, and then take it to have the welding done elsewhere. If one shop is allowed to provide a complete, finished product, they're more likely to raise the price, especially if the job requires more than one metal working discipline, in this case shearing to size / rolling, and welding.
Finally... make it as easy for the welding shop as possible. Once the tube is rolled, eliminate the need for making a jig to hold it together for welding by using some inexpensive (and expendable) stainless steel hose clamps to hold the seam shut.
We'll see how these strategies work for holding down the cost.
Mr. T., the Cheapskate!!!
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Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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BluewaterObserva
Post Laureate
Reged: 05/18/04
Posts: 4968
Loc: Zuni Mtns, NM
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Check out this stuff. I made a 3'x9' ota out of it.
http://www.aitwood.com/StoreFront.Asp?WoodType=POPLAR&CATID=10&Section=HALFCYL&wDesc=Half%20Cylinders%20(180%20degrees)
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Look up Boral (Tubeworks) in your area .... if you decide to stick with a cellulose tube.
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Don W
Postmaster
Reged: 05/19/03
Posts: 14621
Loc: Wisconsin, USA
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How big is your mirror, 12"? Why don't you consider a truss tube? A solid tube the size you are talking about is not only heavy, but bulky.
--------------------
Don Wyman
Obsession 18" f/4.5 #1166
W/Argo Navis DSC and Torus Primary
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droid
rocketman
Reged: 08/29/04
Posts: 4041
Loc: ohio
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Don; actually 13 inches, but yeah after reading more and more here in the atm, forum ,Im thinking solid tube is a mistake, at my 52 years of youngness, I am not sure Im up to a water heater ,lol.
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12 inch Truss Reflector "John"
102mm Celestron C102HD
Tasco 7TE5 60mm Classic
Tasco 9TE5 60mm Classic
Celestron Ultima 2000 SCT
Remains of an 8 inch dob
Celestron Comet catcher(orange tube)
1960 Edscorp Space Conquerer 6inch f/8
10x50 Bushnell Binoculars.
11T 4.5 inch Tasco reflector Lunograsso?
60mm Telescope Club
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Don W
Postmaster
Reged: 05/19/03
Posts: 14621
Loc: Wisconsin, USA
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I mean, I saw a 14" F/8 scope in Australia made of heating duct. It performed magnificently, but took 3 men and a small boy to move. Get in touch with Dennis Steele at Dobstuff and see if that sparks an idea with you. Here's his web site:
http://www.dobstuff.com/
--------------------
Don Wyman
Obsession 18" f/4.5 #1166
W/Argo Navis DSC and Torus Primary
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HandyAndy
professor emeritus
Reged: 01/11/08
Posts: 650
Loc: West Midlands and around
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Hi,
Another source of nice short wood tubes for truss scopes are drum making supplies.
We have one in the UK who will make them up to order. Unsurprisingly they would not reveal their source of birch veneer as I would want to make long tubes.
Cheers. Andrew.
--------------------
Monarch 8x42, Zeiss 10x50 WA
10mm F2, Pentax 60mm F5
City: 7" MN78: MK4#2, 10" F6.3: MK4#1, 16" F5 ParaCorr
Country: 8" VISAC: (GP2)
Car: 6" F5 MPCC: SP, 5" 127mm F7.5 (GP2)
TV 55mm, Paragon 40mm, UO Pretoria 28mm
B&L 32 Pl, Clave's 25, 8, 6, 2x
Hyperions 5, 8, 13, 17, 24, 31
Nagler1 9mm, Meade 14mm 4000 UWA
Antares 1.6x, 0.7x, 0.5x
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BluewaterObserva
Post Laureate
Reged: 05/18/04
Posts: 4968
Loc: Zuni Mtns, NM
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The link I gave is a drum making supplier. by the way. 
Sounds like he is thinking better of it and goign truss to me.
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HandyAndy
professor emeritus
Reged: 01/11/08
Posts: 650
Loc: West Midlands and around
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Hi,
I did take a quick look.
The default page is for half shells and as they are quiet long I did not twig they were drum shells.
Just looked at the detail!
I wonder if I can get half shells over here.
The site I found in the UK only does complete shells I think so limited in length.
Cheers. Andrew.
--------------------
Monarch 8x42, Zeiss 10x50 WA
10mm F2, Pentax 60mm F5
City: 7" MN78: MK4#2, 10" F6.3: MK4#1, 16" F5 ParaCorr
Country: 8" VISAC: (GP2)
Car: 6" F5 MPCC: SP, 5" 127mm F7.5 (GP2)
TV 55mm, Paragon 40mm, UO Pretoria 28mm
B&L 32 Pl, Clave's 25, 8, 6, 2x
Hyperions 5, 8, 13, 17, 24, 31
Nagler1 9mm, Meade 14mm 4000 UWA
Antares 1.6x, 0.7x, 0.5x
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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My aluminum tube project is proceeding satisfactorily.
Courtesy of an EBAY seller, I have a sheet of .050" aluminum (6061-T6), cut to size for rolling into a tube. Now to find a friendly HVAC shop with a sheet metal roller to turn it into a tube.  )
I looked for the 6061 alloy because it's supposed to be easy to weld... but a seemingly BETTER idea has come up.
I haven't thought of this for years, but back in the Air Force we had a sort of Red Green solution to any minor problem on airplanes... it was commonly called "500 MPH Tape"!
Whenever it was necessary to make a quick, temporary repair to the skin of an airplane, out came the 500 MPH tape. It's essentially VERY strong duct tape made of aluminum sheet, maybe 2 mils thick, with one HELL of an adhesive on it.
It suddenly occurred to me... if my tube is made with a butt joint at the seam, why not just use two strips of this stuff (one outside, one inside) to hold the tube together?
If 500 MPH Tape will hold the wings together on a hurt C-130, why wouldn't it hold a telescope tube seam together? ;o) And do it a hell of a lot cheaper and easier than welding.
To Be Continued...
Mr. T.
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Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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DavidinFL
member
Reged: 08/28/09
Posts: 52
Loc: Navarre, FL
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I don't know how well taping a butt joint would work. I would think that the tube would end up having the cross section of a water drop because the tape wouldn't keep the two pieces of the aluminum tangent to each other. AKA you'd end up with an angle along the seam where the two pieces meet.
Another Air Force idea for you. Have you thought about overlapping the two ends and riveting them together? I'd think it'd be cheaper than welding and would keep the tube round.
Good luck,
David
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Orion XT8 - Orion StarMax 102 EQ
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
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Or using one of those cold eelding epoxy glues maybe and a couple of rivets (one each end) just to keep it all line up and square and aligned while the epoxy is curing.
Of cause 24hr high bond strength Aradite (a two part very strong adhesive) might be just the go....
If it every comes apart , then you'd just scrape it off with sharp stanley knife , and try something else.
Careful with high temp IG welding, it could distort the tube.
Edited by Ian Robinson (09/26/09 03:04 AM)
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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Good points, all.
Re. a deformed tube with a "raindrop" cross section:
As soon as the tube is rolled, some "fine tuning" along the length of the joint with a rubber mallet should make the joint tangental, or pretty close to it.
The spider and cell that I'm using here fit over the OD of the tube,and they're more than strong enough to hold the ends in a round cross section.
In addition, I'm planning on putting the focuser right on the joint; it's base and mounting screws should help hold the joint together at a point 3.5" from the aperture.
The mounting I envision for this telescope is based on two stainless steel hose clamps around the tube which will attach it to an oak rail that will mate with a GEM. The clamps will be spaced on either side of the tube's longitudinal balance point by 6 to 10 inches. The pressure of those clamps should hold the middle of the tube in a reasonably round profile.
Adding a slow setting epoxy to the joint before taping isn't a bad idea. After it's sanded down some the tape over it should sufficiently feed my vanity about good looking workmanship; the tape placed over it will give a good, smooth base for painting on the outside, and flocking on the inside.
BTW... during epoxy setting, an improvised jig to support the joint in it's final position seems expedient.
There's a lot that Newbie ATMs building the first telescope have to learn... thanks for all of the good suggestions here!
Mr. T.
--------------------
Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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BTW... more in line with the original subject of this thread:
I just ran into a possible source of a tube for a BIG (up to 20" ID) scope. Further, the say, over and over, NO
MINIMUM ORDER, and they seem to have a number of surface treatment options. Try this link:
http://www.yazoomills.com/custom-paper-tubes/packaging.aspx
This outfit also has a page to describe a product that I find just a little bit creepy; they call 'em "cremation rollers"! 
They're very high strength (1000 lbs to crush 'em) cardboard tubes that are placed under a coffin to save abrasion to the floor of the cremation retort when ya get slid thru the door!
http://www.yazoomills.com/custom-paper-tubes/cremation-rollers.aspx
An even more intriguing product... would you believe "Blast Hole Casings"?
http://www.yazoomills.com/blast-hole-casings.aspx
THESE look like they'd make a DYNAMITE Dob tube (pun intended)! 
Oh my goodness....
Mr. T.
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Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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HandyAndy
professor emeritus
Reged: 01/11/08
Posts: 650
Loc: West Midlands and around
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Hi,
I helped my friend to cut down a tube by 1" to fit in his existing OTA rings.
We used a 1" strip of alloy inside the join to bolt and glue the join to.
We put a couple of bolts at each end.
To hold the join tight while some glue set I planed a convex surface down the length on one side of two pieces of 2"x2" pine. One clamp on each end will apply pressure all down the length as the convex sides are pulled together.
Cheers. Andrew.
--------------------
Monarch 8x42, Zeiss 10x50 WA
10mm F2, Pentax 60mm F5
City: 7" MN78: MK4#2, 10" F6.3: MK4#1, 16" F5 ParaCorr
Country: 8" VISAC: (GP2)
Car: 6" F5 MPCC: SP, 5" 127mm F7.5 (GP2)
TV 55mm, Paragon 40mm, UO Pretoria 28mm
B&L 32 Pl, Clave's 25, 8, 6, 2x
Hyperions 5, 8, 13, 17, 24, 31
Nagler1 9mm, Meade 14mm 4000 UWA
Antares 1.6x, 0.7x, 0.5x
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grendel
sage
Reged: 04/12/09
Posts: 245
Loc: Canterbury, Kent, UK
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In the UK there is this company:-
http://www.essextubes.com/
cardboard tubes up to 24" dia
Grendel
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droid
rocketman
Reged: 08/29/04
Posts: 4041
Loc: ohio
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In case anyone is interested, I jus got off the phone with yazoomills, 14inch tube is between 300 and 400 dollars without shipping and a 15 inch is over 400 dollars.
Me thinks I need to rethink this ,lol. 
--------------------
12 inch Truss Reflector "John"
102mm Celestron C102HD
Tasco 7TE5 60mm Classic
Tasco 9TE5 60mm Classic
Celestron Ultima 2000 SCT
Remains of an 8 inch dob
Celestron Comet catcher(orange tube)
1960 Edscorp Space Conquerer 6inch f/8
10x50 Bushnell Binoculars.
11T 4.5 inch Tasco reflector Lunograsso?
60mm Telescope Club
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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YOW!!!!!
--------------------
Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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Mister T.
member
Reged: 09/15/09
Posts: 22
Loc: Madison, Wisconsin
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My search for a suitable tube is coming to a satisfactory end.
I find that it's getting harder and harder to find places that can fabricate sheet metal these days.It took a lot of searching and phone calls... but I found a real, old fashioned, Honest to Gawd sheet metal shop, with a set of rollers that can handle a 40" sheet of aluminum!
After getting it rolled into a tube, I discovered that my original plan of using .125" sheet really WAS excessive! It would have been like making a rowboat out of leftover battleship armor plate!
For a 40" tube, 6.625" in diameter, a sheet of .050" is MORE than adequate for mechanical strength; rolling a curve into it makes the tube a whole lot more rigid than a flat sheet.
At the same time, I had a 3.25" wide cutoff from the original sheet rolled into a strip to bolt over the seam of the tube. I figure that a layer of epoxy and some 4-40 machine screws, tapped into the tube wall, should hold things together nicely.
BTW... I think I may have found a simple solution for tube rings for this thing.
Exploring the PVC pipe fitting realm, I found that 6" couplers are a very close fit to the projected outside diameter of the tube.
Sawing a coupler in half and adding a hinge to one cut will make a tube mounting ring. To close it up, a couple of 7" hose clamps around the outside should suffice.
Some modification of the coupler will be necessary; shave out the seperating ridge from the inside, file a cut to clear the seam closing strip, and line the ring with felt strips to keep the ring from marring the tube surface.
At the moment, the major problem is to get some self etching metal primer, and some flat white paint with a high percentage of titanium oxide in the pigment (for the fastest possible temperature equilibrium of the finished telescope).
After that... flat black painting and flocking the interior of this beast are the order of the day. Followed by fabricating a GEM that's heavy enough to handle the weight.
But... that's the FUN (???) of ATM, isn't it?
Next time... start with a mirror that's BIGGER than 5.3" ! At least make the work worthwhile!
Mister T.
--------------------
Owner & operator of the Mahon Loomis Memorial Radio Monitoring Station & Retirement Home for Ancient Irish Setters
Connoisseur of Russian motorcycles, Sports Kilts, Women's Flat Track Roller Derby, and various other eclectic ephemera
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