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irving2008
06-09-2013, 02:43 PM
Hi all

Trying to find aluminium (or steel if I must) in sizes where one bit fits neatly inside another and can be locked in place with simple clamp - think bike seat-tube into frame, but bigger, say outer tube 45 - 60mm dia, 4 or 5mm wall, if ally, 35 - 40mm, 3mm wall if steel.

Ideally, from an aesthetic point of view, i'd prefer oval tubing say 60mm x 30mm OD in ally but this seems like hens teeth...

My google fu isnt delivering today :(

Any ideas?

WandrinAndy
06-09-2013, 03:39 PM
How about the aluminium tube that is used for tall "portable" radio masts? Although I would imagine they might have a thinner wall size than 4-5mm.

Btw, what on earth is "google fu"?

Greeny
06-09-2013, 06:04 PM
I just came across this afew days ago , i think it's what your after

Buy Telescopic Aluminium Tube online at Metals4u (http://www.metals4u.co.uk/Telescopic-Aluminium-Tube/177/products.asp)
Edit: On second look they might not be big enough

Here does bigger but not the clamps (just jubilees)
Plain End - Antenna Engineering | Supplier of High Performance Amateur Radio Products (http://www.antennaengineering.co.uk/plain-end/)


Cheers
Greeny

irving2008
06-09-2013, 07:25 PM
Thanks both, the antenna mast stuff is on the right lines, but the 1.5mm wall thickness is too thin, even using the 60mm (2.375") size will deflect too much for my purpose, needs 3mm or more :(

'google fu' is the ancient Chinese art of getting the right search term! :D

phill05
06-09-2013, 07:37 PM
what about 25.5mm dia with a 3.175 thick wall, what length & qty are you wanting.

Phill

Greeny
06-09-2013, 09:47 PM
Cant find anything of those sizes :uncomfortableness:

All I can suggest is
2.125 + 2.250 + tube of epoxy
2.375 + 2.500 + tube of epoxy

Massive contact area, so would be a very strong bond
:cheerful:

irving2008
06-09-2013, 10:38 PM
Cant find anything of those sizes :uncomfortableness:

All I can suggest is
2.125 + 2.250 + tube of epoxy
2.375 + 2.500 + tube of epoxy

Massive contact area, so would be a very strong bond
:cheerful:

Ummm... But they do need to slide... And epoxy won't stop them bending under load!

irving2008
06-09-2013, 11:03 PM
what about 25.5mm dia with a 3.175 thick wall, what length & qty are you wanting.

Phill

Thanks, but not strong enough and I need two tubes... The need is to provide a height adjustable support for a ~15kg load with a deflection less than 4mm when the support is at a 15degree angle.

phill05
07-09-2013, 07:42 AM
What if you had a steel rod of say 19mm dia as the sliding part down the bore?

irving2008
07-09-2013, 09:36 AM
What if you had a steel rod of say 19mm dia as the sliding part down the bore?

That might work. A quick mental calc says about 4mm deflection at 1m with 600mm of rod in a 600mm tube (ie min height would be 600mm). I need to do more accurate bending calcs and torsional calcs as may allow too much rotation Weight is about 2.9kg. Only downside is a 1" pole looks aesthetically 'flimsy' lol

EddyCurrent
07-09-2013, 10:48 AM
Any use ?

Speaker Stand Heavy Duty Steel 063C Adjustable 35mm DJ PA 45KG - PAIR - EC | eBay (http://www.ebay.co.uk/itm/Speaker-Stand-Heavy-Duty-Steel-063C-Adjustable-35mm-DJ-PA-45KG-PAIR-EC-/231012797321?pt=UK_Sound_Vision_Stands_Supports&hash=item35c96f8b89)

irving2008
07-09-2013, 11:01 AM
Like your 'out of the box' thinking! The legs are of no use but the pole might be, depends on wall thickness. Supporting 45kg vertically is different to doing so at an angle.

EddyCurrent
07-09-2013, 11:18 AM
Probably not strong enough and also too expensive

Lighting Booms & Boom Stands - Lighting | Manfrotto (http://www.manfrotto.co.uk/lighting-lighting-booms-boom-stands)

Jonathan
07-09-2013, 12:26 PM
Machine a bushing on the lathe and push it in the end of a tube to get the right size?

Greeny
07-09-2013, 03:27 PM
Cant find anything of those sizes :uncomfortableness:

All I can suggest is
2.125 + 2.250 + tube of epoxy
2.375 + 2.500 + tube of epoxy

Massive contact area, so would be a very strong bond
:cheerful:


Ummm... But they do need to slide... And epoxy won't stop them bending under load!

Sorry not being clear ( or more likely I'm not understanding the problem)
I meant glue two tubes 2.125 + 2.250 together to form a composite thicker stronger tube
and glue two tubes 2.375 + 2.500 together to form a composite thicker stronger tube.
these two thicker stronger tubes will now slide over each other.

Cheers greeny

irving2008
07-09-2013, 05:12 PM
Machine a bushing on the lathe and push it in the end of a tube to get the right size?

Could do, but all the load would be concentrated at that point and would lose some of the benefit of the combined bending resistance of the two parts together.


Sorry not being clear ( or more likely I'm not understanding the problem)
I meant glue two tubes 2.125 + 2.250 together to form a composite thicker stronger tube
and glue two tubes 2.375 + 2.500 together to form a composite thicker stronger tube.
these two thicker stronger tubes will now slide over each other.

Cheers greeny

Ah, I get you. Could simplify construction...

In the meantime, using Phill's suggestion of 25.5mm steel tubing/19mm rod I have come up with this:

10031

Uses two tubes with cross plates welded just below top (leaving room for locking collars, not shown) and at bottom. The T-shaped foot is made of 2 bits of 3mm wall 100 x 50 bolted together with 3mm angle and flat plate joining pieces (not shown) and the tubes are bolted into the foot from the side (2 x M8 bolts each side, not shown) and the bottom cross plate bolted into the top of the foot (4 x M8 bolts, not shown).

At the top, 2 x 19mm rods are welded to a cross plate which bolts into the underside of the upper units 10mm walls using 4 x M5 bolts and also sideways through the rods into the walls of the unit using M8 bolts.

Maybe able to shorten foot once I've checked C of G of whole assembly...

Clive S
07-09-2013, 05:56 PM
The link does not work for me. ..Clive

irving2008
07-09-2013, 06:31 PM
The link does not work for me. ..Clive

try it again.... file was uploaded ok but something went wrong and the forum software seems to have deleted it so had to reupload :(

FatFreddie
08-09-2013, 11:53 PM
Aluminium Warehouse do 2" and 2.5" 1/4" wall round tubing but only in fairly long lengths - not sure what clearances / roundness you'd get but skimming the inner should be easy enough..

Many recumbent cycles use this sort of arrangement for attaching the bottom bracket - I have a vague memory that some sizes of standard tube work well but can't find any references. ICE might be able to help you out Recumbent Trikes - ICE - Home (http://www.icetrikes.co/) - most of their manufacturing is done abroad now but they might have some bits for making prototypes.

I made a carbon outer tube for a recumbent by wrapping it round the aluminium inner tube and then wrapping that in insulating tape (to expel excess resin) - works well but not too great a finish. Cure it warm and put it in the freezer to separate (there might have been a layer of cling film in between as well - it was a while ago) - glass fibre would work ok and be cheaper.

I'd be tempted to use collars on slightly thicker tube unless you are being very weight concious.

Matals4u has aluminium tube in shorter lengths - Buy 3"od x 1/4" wall Aluminium Tube from Metals4u 0844 800 0069. (http://www.metals4u.co.uk/Aluminium-tube/3od-x-14-wall-Aluminium-Tube/22/1989/detail.asp)

irving2008
09-09-2013, 09:33 AM
@FF: Yes, I'd already looked at AW but as you say, long lengths :( I only need 600mm or so of each size. Been looking in eBay for offcuts but nothing suitable seen so far. Also there's no info on size tolerance so hard to tell if one fits inside the other or how well. Yes it would be possible to skim the outside of the inner tube, tho not many have a lathe that can do 600mm between centres on a 50mm tube. Not sure how you'd skim the inside on that length as you implied.

The steel tube/rod approach as drawn has the advantage of a simple welded/bolted construction. Large dia aluminum tube will need a 'plug' of some sort thus adding to the cost. Also there are plenty of examples of 20mm steel rod and 25mm x 2.5mm steel tube on eBay.

Now I've done the c of g calcs the foot can be reduced to 500mm long and 500mm wide (from 700 x 650 as drawn).

quickcut
12-09-2013, 07:19 AM
If you wanted oval tube , why not take round tube and squash it in a press brake?