tube / pipe fit over scaffold tube

[Richard Smith]

Hello all

I've asked on a couple of newsgroup during the last month, but not
their thing...

I want to find a tube / pipe, readily available, which will slide over
a scaffold tube. For making jigs and fittings from offcuts of
scaffold tube.

Here in the UK (don't know about elsewhere), scaffold tube has 48.3mm
outside diameter.

I did some web-searching and find, for example, that NPS 2 schedule
80, with 60.33mm outside diameter and 5.537mm wall thickness, should
give 49.256mm bore.

Weld on "fins" with holes for bolts, slit between the "fins" and
bolt-up, and the tube will contract and grip a scaffold tube???

Any knowledge on this?

Regards,
Rich S

[RD]

Post by Richard Smith
Hello all
I've asked on a couple of newsgroup during the last month, but not
their thing...
I want to find a tube / pipe, readily available, which will slide over
a scaffold tube. For making jigs and fittings from offcuts of
scaffold tube.
Here in the UK (don't know about elsewhere), scaffold tube has 48.3mm
outside diameter.
I did some web-searching and find, for example, that NPS 2 schedule
80, with 60.33mm outside diameter and 5.537mm wall thickness, should
give 49.256mm bore.
Weld on "fins" with holes for bolts, slit between the "fins" and
bolt-up, and the tube will contract and grip a scaffold tube???
Any knowledge on this?
Regards,
Rich S

Google 'scaffold tube fittings' and I think you will find what you need.



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[Richard Smith]

Post by RD

Post by Richard Smith
Hello all
I've asked on a couple of newsgroup during the last month, but not
their thing...
I want to find a tube / pipe, readily available, which will slide over
a scaffold tube. For making jigs and fittings from offcuts of
scaffold tube.
...
...
...
bolt-up, and the tube will contract and grip a scaffold tube???
Any knowledge on this?
Regards,
Rich S

Google 'scaffold tube fittings' and I think you will find what you need.

Hiya
Hope I am not missing something here, but there's stillages full of
standard scaffold tube fittings here. No problem getting any number
of those.
It's tube to make custom fittings for the application of using offcuts
of scaffold tube for purposes having nothing to do with scaffolding.
eg. making rotating welding jigs which you can attach to your trestles
for reliable neat series-run components.
Scaffold tube is a "plastic section" (it's thick enough to never
buckle in overload, only general bend) (???) so it's a very reliable
structural member for improvised purposes, as well as being abundantly
available.
Regards,
Rich Smith

[Clifford Coggin]

Post by Richard Smith
Hiya
Hope I am not missing something here, but there's stillages full of
standard scaffold tube fittings here. No problem getting any number
of those.
It's tube to make custom fittings for the application of using offcuts
of scaffold tube for purposes having nothing to do with scaffolding.
eg. making rotating welding jigs which you can attach to your trestles
for reliable neat series-run components.
Scaffold tube is a "plastic section" (it's thick enough to never
buckle in overload, only general bend) (???) so it's a very reliable
structural member for improvised purposes, as well as being abundantly
available.
Regards,
Rich Smith

I'm still not entirely clear what you are looking for. If it is simply
steel tube of a certain diameter then just search for it without
mentioning scaffold.

[Jim Wilkins]

Post by Richard Smith
...
Scaffold tube is a "plastic section" (it's thick enough to never
buckle in overload, only general bend) (???) so it's a very reliable
structural member for improvised purposes, as well as being
abundantly
available.
Regards,
Rich Smith

Whether or not a column of tubing can fail by buckling depends on its
effective length to diameter ratio, nothing including solid rod is
inherently immune regardless of the application.

https://en.wikipedia.org/wiki/Euler%27s_critical_load

"The critical load puts the column in a state of unstable
equilibrium."
I once accidentally loaded log hoisting shear legs made from 2x4's to
precisely the critical load, where the leg would remain at whatever
bowed deflection I pushed it to.

[Richard Smith]

Post by Jim Wilkins

Post by Richard Smith
...
Scaffold tube is a "plastic section" (it's thick enough to never
buckle in overload, only general bend) (???) so it's a very reliable
structural member for improvised purposes, as well as being
abundantly
available.
Regards,
Rich Smith

Whether or not a column of tubing can fail by buckling depends on its
effective length to diameter ratio, nothing including solid rod is
inherently immune regardless of the application.
https://en.wikipedia.org/wiki/Euler%27s_critical_load
"The critical load puts the column in a state of unstable
equilibrium."
I once accidentally loaded log hoisting shear legs made from 2x4's to
precisely the critical load, where the leg would remain at whatever
bowed deflection I pushed it to.

Hi Jim.

Thanks for engaging in this line of thought.

OK - I try to avoid too many words - not as find that easy :-)

I meant "local buckling" when I only said "buckling".
I know of the Euler Critical Buckling Force calculation. General
bowing-out which is a distributed buckling phenomenon. Recently used
it to propose the design of a sheerleg - same as the application where
you offer the observation. I'd get in difficulties if I made
experimental assemblies where I work - bit unimaginitive - general
problem I find here of very limited outlook and not seeing success as
only coming from venturing and building up experience bit-by-bit,
reaching ever further into unique, valuable, remunerative (!!!)
knowledge and ability.

I wondered what being on the point of the Euler critical buckling load
looks like. So you do get some visible warning?

Regards,
Rich Smith

[Jim Wilkins]

Post by Richard Smith

Post by Jim Wilkins

Post by Richard Smith
...
Scaffold tube is a "plastic section" (it's thick enough to never
buckle in overload, only general bend) (???) so it's a very
reliable
structural member for improvised purposes, as well as being
abundantly
available.
Regards,
Rich Smith

Whether or not a column of tubing can fail by buckling depends on its
effective length to diameter ratio, nothing including solid rod is
inherently immune regardless of the application.
https://en.wikipedia.org/wiki/Euler%27s_critical_load
"The critical load puts the column in a state of unstable
equilibrium."
I once accidentally loaded log hoisting shear legs made from 2x4's to
precisely the critical load, where the leg would remain at whatever
bowed deflection I pushed it to.

Hi Jim.
Thanks for engaging in this line of thought.
OK - I try to avoid too many words - not as find that easy :-)
I meant "local buckling" when I only said "buckling".
I know of the Euler Critical Buckling Force calculation. General
bowing-out which is a distributed buckling phenomenon. Recently used
it to propose the design of a sheerleg - same as the application where
you offer the observation. I'd get in difficulties if I made
experimental assemblies where I work - bit unimaginitive - general
problem I find here of very limited outlook and not seeing success as
only coming from venturing and building up experience bit-by-bit,
reaching ever further into unique, valuable, remunerative (!!!)
knowledge and ability.
I wondered what being on the point of the Euler critical buckling load
looks like. So you do get some visible warning?
Regards,
Rich Smith

The 2" x 4" x 12' shear leg that buckled was somewhat warped so it had
a cantilevered load instead of being a pure pinned-end column. It
bowed slightly as the ~280 Lb log left the ground. When I saw that I
decided to experiment without lifting the log further, and found it
was at the point of neutral stability -- the 2x4 would hold whatever
bow I pushed it to, as the equation suggests.

I switched to metal pipe whose strength I could calculate and test for
the shear legs, made ball ends and socketed baseplates for them and
bought a 1000Kg load scale.
https://www.amazon.com/Hanging-Klau-Digital-Industrial-Measuring/dp/B00VDKXJ2W

As for a warning, I suppose you could lift the load slightly off the
ground and push the column sideways to see how easily it flexes, but
only for thin columns, light loads and no safety margin. The column's
compression strain is still within the linear region when it starts to
buckle elastically. The bolts I used at the top have a bearing
strength on the column walls lower than the calculated buckling load
so they show overloads on inspection afterwards. I've tried a welded
ring as a mechanical fuse that's visible fom a safe distance.

My degree is in chemistry, I learned electrical and mechanical
engineering mostly on my own and don't trust my calculations without
testing them for my home projects, solar power and moving oak logs for
my home made sawmill. At work I wanted to recognize when to call in an
expert from another field.

That's all. The temperature has risen to freezing and I have roof
beams to replace before snow falls.

[Jim Wilkins]

Post by Richard Smith
Hello all
I've asked on a couple of newsgroup during the last month, but not
their thing...
I want to find a tube / pipe, readily available, which will slide over
a scaffold tube. For making jigs and fittings from offcuts of
scaffold tube.
Here in the UK (don't know about elsewhere), scaffold tube has
48.3mm
outside diameter.

Sorry, I had hoped your countrymen would be more helpful. 48.3mm
translates to 1.90", the OD of US 1-1/2" pipe and 2" chain link fence
posts, but my tabulation of commonly available (= cheap offcuts) pipe
and tubing has nothing close to that ID.

Perhaps you could bore out 1-1/2" pipe tees to support your scaffold
tubing fixtures. Pipe is made by a process that doesn't leave it very
accurately round, especially along the weld seam, compared to DOM
tubing. I chuck drawn brass pipe or a machined hydraulic fitting in
the lathe so the threads run true, then screw on the rough cast
fitting to turn its OD round and concentric enough to re-chuck the
fitting directly to bore it.

[Richard Smith]

Post by Jim Wilkins

Post by Richard Smith
Hello all
I've asked on a couple of newsgroup during the last month, but not
their thing...
I want to find a tube / pipe, readily available, which will slide over
a scaffold tube. For making jigs and fittings from offcuts of
scaffold tube.
Here in the UK (don't know about elsewhere), scaffold tube has 48.3mm
outside diameter.

Sorry, I had hoped your countrymen would be more helpful. 48.3mm
translates to 1.90", the OD of US 1-1/2" pipe and 2" chain link fence
posts, but my tabulation of commonly available (= cheap offcuts) pipe
and tubing has nothing close to that ID.
Perhaps you could bore out 1-1/2" pipe tees to support your scaffold
tubing fixtures. Pipe is made by a process that doesn't leave it very
accurately round, especially along the weld seam, compared to DOM
tubing. I chuck drawn brass pipe or a machined hydraulic fitting in
the lathe so the threads run true, then screw on the rough cast
fitting to turn its OD round and concentric enough to re-chuck the
fitting directly to bore it.

Hi Jim

Thanks for words of wisdom.

I noticed there is API NPS 2 schedule 80.
I hadn't realised "NPS 2 schedule 80" is an API spec.
That is known around the world, due to the respect for the API
(American Petroleum Institute). So some chance here...

Taking tabulated specs and doing a bit of maths, that gives 49.3mm
(1.939") bore, for intention to fit over 48.3mm OD (1.901").
Also now find the 1.939" bore tabulated.
Which seems reasonably realistic for a fit, given experienced comments
about tolerance on manufactured size and shape. Every application
would have the tube split and with two plates with aligning bolt holes
along the split to permit grip on the "scaffold tube". In these
shorter lengths for fixtures, a die-grinder could be used to remove
flash from the bore of the outer pipe, given it would be seam-welded.

Is that a common tube size as you know of?
Have I got it right?
This "schedule" business is about having tubes which will slide over
each other, for miscellaneous practically useful reasons ?

"Streetwise" advice and comment sought!

Regards,
Rich Smith

[Jim Wilkins]

...Every application
would have the tube split and with two plates with aligning bolt holes
along the split to permit grip on the "scaffold tube".

https://www.amazon.com/1-1-2-Pipe-Repair-Clamp/dp/B00EEEXQVS

[Jim Wilkins]

Post by Jim Wilkins

...Every application
would have the tube split and with two plates with aligning bolt holes
along the split to permit grip on the "scaffold tube".

https://www.amazon.com/1-1-2-Pipe-Repair-Clamp/dp/B00EEEXQVS

You could also look at pipe hangers and the fittings for joining pipe
hand rails. The wide repair clamp might be best if you want to line it
with a friction material like hi temp gasket sheet so it could be
moved with some adjustable effort, without removing gloves to loosen
and retighten the bolts.