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Equipment Discussions >> ATM, Optics and DIY Forum

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JohnH
Carpal Tunnel
****

Reged: 10/04/05

Loc: Squamish BC Moved!!!!!
Re: Round Wooden Tubes? new [Re: ZeroID]
      #4222111 - 12/01/10 08:25 PM

I forgot I did this experiment using some off-cuts of MDF in an octagonal fashion.

I did as tim5.3 did, just taped the outside faces, spread glue on the cuts between, pulled them together and let dry.

I was also very skeptical this would support any large amount of weight.

It dryed for a few weeks and then I pushed it down on the floor and finally STOOD on it without it breaking. I actually had to jump on it to get this short section ~16" or so to fracture. The glue failed.


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Astro88
member


Reged: 08/30/09

Re: Round Wooden Tubes? new [Re: ZeroID]
      #4222245 - 12/01/10 09:25 PM

I know you asked for tips on making a wooden tube, not buying one, but there is a company called Anderson International Trading that sells them. For example:

http://www.aitwood.com/StoreFront.Asp?ItemID=37500&wdesc=Pedestals%2048%20inches%20Tall%20Paint%20Grade

Click on Millwork Components, then Plywood Cylinders to view all the sizes they make.


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Brian Reed

*****

Reged: 10/29/04

Loc: North East Illinois
Re: Round Wooden Tubes? new [Re: Astro88]
      #4222414 - 12/01/10 10:55 PM

Check out Chuck Fellows scopes. He has instructions on his web page

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tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: Brian Reed]
      #4222456 - 12/01/10 11:30 PM

Lots of neat stuff there. I'd seen Chuck Fellow's site before, but not the Japanese guy's!

I made my Cass's tube similarly, a few sides at a time. But I had longitudinal ribs (corners, really) to define the angle between sides. I did it this way to avoid having tube currents cascading off baffles inside the tube and into the light path, which was a problem I had on a prior tube for those optics: Cass thread

-Tim.


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ColoHank
Carpal Tunnel
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Reged: 06/07/07

Loc: western Colorado
Re: Round Wooden Tubes? new [Re: tim53]
      #4222486 - 12/01/10 11:59 PM Attachment (45 downloads)

I made a round tube for a Galileo scope built-up from sixteen staves of red alder. I too used blue masking tape to hold the staves together while I applied a liberal amount of plastic resin glue (that glue has a long open time, so it won't set prematurely). Then I rolled the assembly up, tightly wrapped the resulting tube with nylon monofilament fishing line to exert even pressure all around, rolled the whole assembly back and forth across a table until the staves squirmed into proper registration with one another, and then set it aside overnight to let the glue cure. Hand-sanding of the exterior removed the sixteen facets to produce a tube that was uniformly round from one end to the other.

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DarkSkys
professor emeritus
*****

Reged: 10/11/10

Loc: In the dark desert of Eastern ...
Re: Round Wooden Tubes? new [Re: ColoHank]
      #4222522 - 12/02/10 12:40 AM

Anyone know what the dementions of the boards would have to be for a 6 sided tube? I'm planning to make it out of poplar boards, useing a table saw to cut the angles, and then useing a biscut cutter and biscuts+ glue to make a tough,lightweight and good lookin tube.

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scopemankit
sage


Reged: 01/27/09

Loc: south africa
Re: Round Wooden Tubes? new [Re: ZeroID]
      #4222655 - 12/02/10 03:09 AM

I made a 127mm rich-field telescope in 1999. The tube was of strips of different color merante, wood 6mm thick and 20mm wide. I cut the strips with a small angle so the pieces would nest together. They were then glued with polyester resin inside a pair of aluminum bands (one is hidden by the base cover made of denim). They fit very tightly inside the bands and every fourth strip was pop riveted to the bands. No mounting, you simply sat down and clutch the telescope, partially suspended by the fabric strap, to your body and enjoy the skies! It is very strong and, I believe it now lives in Canada.

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scopemankit
sage


Reged: 01/27/09

Loc: south africa
Re: Round Wooden Tubes? new [Re: scopemankit]
      #4222658 - 12/02/10 03:17 AM Attachment (52 downloads)

A picture of the "Peanut" 127mm rft

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dan_h
Carpal Tunnel


Reged: 12/10/07

Re: Round Wooden Tubes? new [Re: PhotoGazer]
      #4223175 - 12/02/10 11:20 AM Attachment (44 downloads)

I made a round tube from slats for a 100mm Refractor. Finished size about 106mm outside. The dew shield was larger, about 130mm outside.

I cut 18 slats on the table saw and they went together perfectly. A quick pass with a plane over the high spots on the finished tube allowed for an easy sanding job. I used 20 slates for the dew shield. I used an on-line circle calculator to help with the arithmetic.

http://www.1728.com/circsect.htm

When cutting the slats, the angle bewteen two adjacent pieces is shared so each piece gets 1/2 the needed angle. Cut the angles just a hair large to ensure any gap at the joined pieces in on the inside. (If you need a 5 degree cut, make it 5.05 rather than 4.95)

I got my inspirations from Chuck Fellows. He does beautiful work that I cannot begin to match. Check out his telescopes on his site.

http://cfellows.com/

good luck with your project,

dan


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PhotoGazer
super member
*****

Reged: 09/26/07

Re: Round Wooden Tubes? new [Re: dan_h]
      #4224712 - 12/02/10 11:44 PM

Thanks for some really good ideas and links. I have several thought and ideas that I have developed from reading the comments here, and viewing the links. I plan to test some of them tomorrow in the wood shop. Just in case you don't know, I build guitars, but many of the techniques used in forming guitar bodies cannot be easily transferred over to the larger areas on wood used in telescope tubes. However, I have a large selection of beautiful and exotic woods at my disposal. Many of them were purchased in lots that contained the wood I wanted, but are not suitable for guitar tone woods. They are, however, terrific choices for telescope tubes. Since I started this thread, I am now more excited than ever about where I can go with this project. I plan to photograph the processes that I develop so others can take advantage of them, if they work out. Feel free to keep this thread going with more ideas and links if you have any. I think a lot of ATM'ers can take advantage of this info.

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FlashJohnson
member
*****

Reged: 10/14/10

Loc: Southern tip of Lake Michigan
Re: Round Wooden Tubes? new [Re: DarkSkys]
      #4228586 - 12/04/10 06:30 PM

To create a six sided cylinder, divide 360 degrees (the quantity of degrees in a circle) by the quantity of boards (a.k.a. "staves") you will use...(360/6=60).

Next, divide THAT number (in this case 60 degrees) by "two" (60/2=30) since each of the six boards has two ends each that need beveled... requiring a thirty degree bevel on each of the two ends of the "staves".

Write back if you need any more info, as I just recently completed making a series of wooden cylinders and found much information on websites that cater to wooden drum makers, of all people (yes Lucy, Rickey WILL BE HOME after tonight's show at de club! )

And by the way, C. Fellows' website (mentioned elsewhere in this thread) instructions are so incredibly well done, they've given me MORE REASONS to build my next scope......

Sheeeshhh... does it EVER end??? ;-)


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FlashJohnson
member
*****

Reged: 10/14/10

Loc: Southern tip of Lake Michigan
Re: Round Wooden Tubes? new [Re: FlashJohnson]
      #4228592 - 12/04/10 06:33 PM

Ooooops... my reply may be redundant, now that I have read more of the thread ... hope I didn't confuse things..... as is my usual "M.O."!

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tim53
Postmaster
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: FlashJohnson]
      #4230854 - 12/05/10 08:18 PM Attachment (43 downloads)

Here's one I tossed together for a short-focus 3" lens I have:

Dark Lauan Mahogany. 13 staves, just cause it worked out that way. I don't like working with such narrow and thick pieces on the table saw. Freaked me out somewhat. And I've got a couple wide joints that'll need filling, probably with epoxy.

Here it is on the lathe for turning the OD:

-tim.


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tim53
Postmaster
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4230859 - 12/05/10 08:20 PM Attachment (38 downloads)

And here it is now. I tured a step in the end for mounting a ring to adapt the focuser to. I'm planning on using an old Jaegers focuser, but I might spring for a Crawmach if the lens is a good one (haven't ever looked through it).

-Tim.


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tim53
Postmaster
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4230862 - 12/05/10 08:21 PM

I hate that my Mac's "Preview" software will rotate the image from the iPhone as I took it, but it won't save it that way. sorry if looking at those makes you feel like you're going to fall over!

-Tim.


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Dane Lance
journeyman


Reged: 12/04/10

Re: Round Wooden Tubes? new [Re: tim53]
      #4231012 - 12/05/10 09:42 PM

I can only think of one question here...why on earth would you want to make the tube for a telescope out of a material so susceptible to movement with changes in humidity?

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cloudmagnet
sage


Reged: 12/04/08

Loc: Georgetown, Texas
Re: Round Wooden Tubes? new [Re: Dane Lance]
      #4231095 - 12/05/10 10:31 PM

Here's a link to building round sailboat masts....just like telescope tubes, only loooonger!!!
http://www.duckworksmagazine.com/06/howto/birdsmouth/index.htm


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tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? [Re: Dane Lance]
      #4231265 - 12/06/10 12:24 AM

Quote:

I can only think of one question here...why on earth would you want to make the tube for a telescope out of a material so susceptible to movement with changes in humidity?




The trick is to stabilize it so moisture doesn't affect it. Epoxy or polyurethane.

...and don't forget materials that are susceptible to movement with changes in temperature or flexure - like aluminum, graphite-epoxy, fiberglass... the list does indeed go on.

-Tim.


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plyscope
Pooh-Bah


Reged: 11/23/06

Loc: Perth, West Australia
Re: Round Wooden Tubes? [Re: Dane Lance]
      #4231353 - 12/06/10 02:10 AM

If it's good enough for Mr Fraunhofer then why not use wood?
Dorpat Refractor
Tim is correct, it is not so much the material you need to worry about, more the design and application. Wood is fine if the right type is chosen and it is protected with paint, sealer or varnish of some sort. I must admit I am biased.

Andy


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Dane Lance
journeyman


Reged: 12/04/10

Re: Round Wooden Tubes? [Re: plyscope]
      #4231513 - 12/06/10 06:42 AM

Sorry guys, I didn't mean that to come across as any kind of put down. I've been woodworking for over 20 years, but I'm a total newbie to telescopes and astronomy and you guys certainly know way, way more than I do when it comes to scopes.

I just know how much wood moves, and how unevenly, even when it is sealed. You can never completely seal wood, even with epoxies, etc.

However, since I have a desire to try to contribute, I will say, if you can get it in the lengths you need, mesquite wood moves very little in comparison to most woods. It's also beautiful and strong, albeit pricey. It is hard on cutters though as it is very salicious.

I turn it "green" on the lathe, and even very thin walled bowls or hollow vessels rarely warp or crack when drying.


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