Source for telescoping tubing stock?

[hans]

McMaster-Carr sells some brass and aluminum tubing, where, for example, inner/outer diameters differ by 0.003 inches going from one size to the next but the largest size is 5/8" (16 mm) ID and I am looking for something more like 30-40 mm. Any ideas for a source for raw tubing or something that can be purchased inexpensively and salvaged for such tubing?

I am thinking about how to mount the complete eye tube with eyepiece shown in this post a bit less crudely. I would like to have a way to adjust the height while maintaining alignment but don't really need something like a focusing helicoid for frequent, precise adjustment. The focusing helicoids I have seen are fairly expensive with short travel. Something that could be unclamped/moved/clamped for infrequent adjustment would be fine, I think.

[Element 56]

Hans,

What about a telescope focuser? An old tasco is cheap, has a rack and pinion and telescoping tubes. Could you make something like that work?

Kirby

[hans]

What about a telescope focuser?

Of course, a telescope as a source for "telescoping" tubing, now I feel dumb... but that does look like a promising option, thank you.

[Scarodactyl]

Maybe bellows?

[MichaelG.]

Telescopic sizes of ‘carbon fiber’ tubing are quite widely available, but it’s tricky to work with.

This, however, might suit your purpose: https://formufit.com/pages/telescopic-pipe-sizes
and “for your shopping convenience: https://formufit.com/pages/formufit-onl ... l-partners

MichaelG.

[apochronaut]

You would possibly therefore need a 1 1/4" focuser? I can't recall Tasco using ànything but .965, except perhaps on those Bird-Jones Catadioptric scopes they bought from Towa in the late 70's early 80's. They were red. The 3" and 4 1/2" were probably .965 but there were also some marked 114mm and 152mm. The same scopes were out in yellow too marketed by several players in the cheap telescope market and did have 1 1/4 focusers. Many have probably done double duty as concrete forms for deck posts by now.

Another possible option might be the post of a disused drummer's throne. I see these at the curb sometimes and most drum shops probably has some broken crappy thrones they have have no idea why they are keeping. That happens in those places. There are various ways they adjust for height but none have a track and only better ones would have a fairly tight fit. They are always chromed.

[hans]

Maybe bellows?

I do actually have an old, low-quality bellows laying abound but was leaning away from that for a few reasons. Since it it designed to interface with camera stuff there would still be a fair amount of fabrication/adaptation necessary to make it work between the trinocular head and eye tube. I was thinking bare tubes of the right size could actually be easier to attach. It also is not very rigid which I was worried could be a problem if I eventually decided to mount the camera on top for convenience rather than hovering over the eyepiece with a tripod. A good quality bellows with some adapters would probably work nicely but also looks fairly expensive, like ~2-4. (Using units of "old surplus AO/Reichert microscopes".)

This, however, might suit your purpose: https://formufit.com/pages/telescopic-pipe-sizes

That is the sort of thing I had in mind, but unfortunately on those the OD/ID gap is pretty large, probably excessive angular play over short distances. There is the possibility of shimming out with tape or whatever, but if the gap is that large to begin with, you wonder whether the tubing is uniform enough.

Many have probably done double duty as concrete forms for deck posts by now.

Yeah, not sure I'm prepared to buy one of those and relive the crushing childhood disappointment you get looking through it after being misled by the photos on the box.

Another possible option might be the post of a disused drummer's throne. I see these at the curb sometimes and most drum shops probably has some broken crappy thrones they have have no idea why they are keeping. That happens in those places.

Happens in my garage, also. Doesn't make sense to put it out on the curb yet, I use it once every few year as a saw horse...

[Adam Long]

I bought one of these last year for an astronomy project:

https://www.ebay.co.uk/itm/Metal-High-P ... 466b3776b8

That project didn't really work out but it had occurred to me that it could be ideal for adapting a camera to a microscope. Inner diameter is 1.25", offers 10mm adjustment with a fairly stiff helical plus lock screw so unlikely to slip.

[MichaelG.]

This, however, might suit your purpose: https://formufit.com/pages/telescopic-pipe-sizes

That is the sort of thing I had in mind, but unfortunately on those the OD/ID gap is pretty large, probably excessive angular play over short distances. There is the possibility of shimming out with tape or whatever, but if the gap is that large to begin with, you wonder whether the tubing is uniform enough.

Agreed ... the numbers are big [but ‘locally’ they are, of course, halved]

Although It doesn’t appear to be stated, I presumed that the gap would be about right for ‘solvent weld’ ... to be applied after you had experimentally determined the right length.

Not an ideal solution but [for a man with few tools] maybe worth a look.

MichaelG.