Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

Also looking for metal tube with a no slop sliding fit over it..found
1/4" OD brass thin wall....anyone know if that is gonna fly?

In message , The Natural Philosopher
writes
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

I buy 86 [1] 13" [2] lengths at a time of silver steel, it's also sold
in just over 3' lengths. You don't normally buy it in other lengths

what length are you after ?


Also looking for metal tube with a no slop sliding fit over it..found
1/4" OD brass thin wall....anyone know if that is gonna fly?


[1] don't ask why, no idea, nor do the supplier

[2] - so you can cut 1/2" off each end to get 12" without the risk of
distortion

--
geoff

"The Natural Philosopher" wrote in message
...
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

Also looking for metal tube with a no slop sliding fit over it..found 1/4"
OD brass thin wall....anyone know if that is gonna fly?


Stiffness, not a lot of difference. If you want to run it in a bearing with
minimal work, silver steel is very accurate. Whether brass thin wall tubing
is suitable depends on the speed, load, duty, lubrication....

On 1 June, 20:15, The Natural Philosopher
wrote:
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

Also looking for metal tube with a no slop sliding fit over it..found
1/4" OD brass thin wall....anyone know if that is gonna fly?

Silver steel can be hardened and tempered to suit your application.
Stainless
steel is likely to work harden and become brittle. There some
knowledgeable
metallurgists over on British Blades who might help.

geoff wrote:
In message , The Natural Philosopher
writes
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

I buy 86 [1] 13" [2] lengths at a time of silver steel, it's also sold
in just over 3' lengths. You don't normally buy it in other lengths

what length are you after ?

minimum about 9", but can cut to size. I have found it all right, in
suitable sizes.. also stainless. Just wondered which was stiffer. Needs
to take a large bending load without plastic deformation. I'd rather it
snapped..




Also looking for metal tube with a no slop sliding fit over it..found
1/4" OD brass thin wall....anyone know if that is gonna fly?


[1] don't ask why, no idea, nor do the supplier

[2] - so you can cut 1/2" off each end to get 12" without the risk of
distortion

newshound wrote:


"The Natural Philosopher" wrote in message
...
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

Also looking for metal tube with a no slop sliding fit over it..found
1/4" OD brass thin wall....anyone know if that is gonna fly?


Stiffness, not a lot of difference. If you want to run it in a bearing
with minimal work, silver steel is very accurate. Whether brass thin
wall tubing is suitable depends on the speed, load, duty, lubrication....

Its actually wing attachment cantilevers for largish model gliders.
Slide on, locate laterally, and go fly..but without the wings bouncing
up and down..tried 4mm piano wire..no good.

In message , The Natural Philosopher
writes
geoff wrote:
In message , The Natural Philosopher
writes
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?
I buy 86 [1] 13" [2] lengths at a time of silver steel, it's also
sold in just over 3' lengths. You don't normally buy it in other lengths
what length are you after ?

minimum about 9", but can cut to size. I have found it all right, in
suitable sizes.. also stainless. Just wondered which was stiffer. Needs
to take a large bending load without plastic deformation. I'd rather it
snapped..


I can send you a "foot" to play with if you want




Also looking for metal tube with a no slop sliding fit over
it..found 1/4" OD brass thin wall....anyone know if that is gonna fly?

[1] don't ask why, no idea, nor do the supplier
[2] - so you can cut 1/2" off each end to get 12" without the risk
of distortion


--
geoff

geoff wrote:
In message , The Natural Philosopher
writes
geoff wrote:
In message , The Natural Philosopher
writes
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?
I buy 86 [1] 13" [2] lengths at a time of silver steel, it's also
sold in just over 3' lengths. You don't normally buy it in other lengths
what length are you after ?

minimum about 9", but can cut to size. I have found it all right, in
suitable sizes.. also stainless. Just wondered which was stiffer.
Needs to take a large bending load without plastic deformation. I'd
rather it snapped..


I can send you a "foot" to play with if you want

Oh..no need. we will be getting a fair bit in..several models have lost
their wing joiners, and a new one needs some more. andd that's going
into production shortly.. It was just a case of which to buy really..

But thank you for the offer anyway, that is appreciated.

In message , The Natural Philosopher
writes
geoff wrote:
In message , The Natural Philosopher
writes
geoff wrote:
In message , The Natural
Philosopher writes
Looking for some 6mm diameter steel shafting. Primary requirement
is stiffness. Is stainless better than silver steel?
I buy 86 [1] 13" [2] lengths at a time of silver steel, it's also
sold in just over 3' lengths. You don't normally buy it in other
lengths
what length are you after ?

minimum about 9", but can cut to size. I have found it all right, in
suitable sizes.. also stainless. Just wondered which was stiffer.
Needs to take a large bending load without plastic deformation. I'd
rather it snapped..

I can send you a "foot" to play with if you want

Oh..no need. we will be getting a fair bit in..several models have lost
their wing joiners, and a new one needs some more. andd that's going
into production shortly.. It was just a case of which to buy really..

But thank you for the offer anyway, that is appreciated.

This is where I get mine from

http://www.cromwell.co.uk/

significantly cheaper than the "RS"s of this world

--
geoff

"The Natural Philosopher" wrote in message
...
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

Yes and no, depending upon the grade of stainless steel, but there won't be
a lot in it.

Also looking for metal tube with a no slop sliding fit over it..found 1/4"
OD brass thin wall....anyone know if that is gonna fly?

Not without knowing what the wall thickness actually is. Generally, I would
drill and ream something if I wanted it to be a specific fit. Silver steel
would be an advantage here as it is dimensionally more reliable than bar
stock.

Colin Bignell

"mr fuxit" wrote in message
...
On 1 June, 20:15, The Natural Philosopher
wrote:
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

Also looking for metal tube with a no slop sliding fit over it..found
1/4" OD brass thin wall....anyone know if that is gonna fly?

Silver steel can be hardened and tempered to suit your application.

So can a martinsitic stainless steel, such as 416.

Stainless
steel is likely to work harden and become brittle.

There is a huge number of different grades, with many different properties.

Colin Bignell

On 1 June, 20:15, The Natural Philosopher
wrote:
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness.

Carbon fibre, Kite spar's easy to get and cheap enough in that size.

"The Natural Philosopher" wrote in message
...
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

LOL. Don't you realise that every type of steel, hardened or otherwise has
exactly the same Young's modulus i.e. exactly the same deflection per unit
force applied? All that changes with constituents and heat treatment is the
tensile strength and hardness but the stiffness stays exactly the same.


Also looking for metal tube with a no slop sliding fit over it..found 1/4"
OD brass thin wall....anyone know if that is gonna fly?

I doubt it.
--
Dave Baker

The Natural Philosopher wrote:
I have found it all right, in
suitable sizes.. also stainless. Just wondered which was stiffer. Needs
to take a large bending load without plastic deformation. I'd rather it
snapped..


There are two different concepts getting a bit mixed up. As Dave Baker
says elsewhere, all steels have more or less the same elastic modulus,
or stiffness. What does vary is the load at which they fail, and the
mode of failure. So a "high tensile" steel will yield, i.e. deform
permanently, at a higher load than mild steel, and a brittle material
will fail such that the bits more or less fit together afterwards,
whereas a ductile material will stretch first. Heat treatment of many
materials affects these properties, but not stiffness. All a gross
simplification, but hey, it was free.

Could you make it as a hollow tube, rather than out of solid? For a
given weight, potentially much stiffer and stronger. Without being able
to do the sums, I'd also guess that a really good fit between the two
pieces is very important, not just to avoid things flapping around,
which seems OK for birds but perhaps not models, but because a loose fit
may lead to some locally high stresses at the end of the tube.

I think I'd be looking at composites (pultruded grp is good stuff) or
aluminium tubes in tubes.


--
Kevin Poole
****Use current date to reply (e.g. )****

Andy Dingley wrote:
On 1 June, 20:15, The Natural Philosopher
wrote:
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness.

Carbon fibre, Kite spar's easy to get and cheap enough in that size.

Not strong enough and too flexible.

On 2 June, 06:45, "Dave Baker" wrote:

LOL. Don't you realise that every type of steel, hardened or otherwise has
exactly the same Young's modulus

While that's broadly true on the range of workshop alloy steels,
doesn't stainless typically drop about 10%?

I presume there are also some varieties of unobtainium that go the
other way too...

"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models have lost
their wing joiners, and a new one needs some more. andd that's going into
production shortly.. It was just a case of which to buy really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

Dave Baker wrote:
"The Natural Philosopher" wrote in message
...
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

LOL. Don't you realise that every type of steel, hardened or otherwise has
exactly the same Young's modulus i.e. exactly the same deflection per unit
force applied? All that changes with constituents and heat treatment is the
tensile strength and hardness but the stiffness stays exactly the same.

Are you sure?

Wiki seems to suggests that high carbon steel has 10% gtreater young's
modulus than stainless. And twice as much as cast iron.

However, I take your point that the variation is not great over the
range of alloys in question.


Also looking for metal tube with a no slop sliding fit over it..found 1/4"
OD brass thin wall....anyone know if that is gonna fly?

I doubt it.

Well you obvously dont know..

Kevin Poole wrote:


The Natural Philosopher wrote:
I have found it all right, in suitable sizes.. also stainless. Just
wondered which was stiffer. Needs to take a large bending load without
plastic deformation. I'd rather it snapped..


There are two different concepts getting a bit mixed up. As Dave Baker
says elsewhere, all steels have more or less the same elastic modulus,
or stiffness. What does vary is the load at which they fail, and the
mode of failure. So a "high tensile" steel will yield, i.e. deform
permanently, at a higher load than mild steel, and a brittle material
will fail such that the bits more or less fit together afterwards,
whereas a ductile material will stretch first. Heat treatment of many
materials affects these properties, but not stiffness. All a gross
simplification, but hey, it was free.

Right. I hadn't appreciated that the stiffness was almost independent of
composition. I knew the other properties varied enormously.


Could you make it as a hollow tube, rather than out of solid? For a
given weight, potentially much stiffer and stronger. Without being able
to do the sums, I'd also guess that a really good fit between the two
pieces is very important, not just to avoid things flapping around,
which seems OK for birds but perhaps not models, but because a loose fit
may lead to some locally high stresses at the end of the tube.

That's inevitable anyway. Weight is not too serious oddly enough, as a
typical sailplane needs a bit of ballast to cope with wind..increases
flying speed without having to dive.

I think I'd be looking at composites (pultruded grp is good stuff) or
aluminium tubes in tubes.

Well people can and do use those, but there is a drawback, and that's
wear as they get plugged and unplugged, and under flexure. Eventually
you have a lot of slop and black dust. If C/F is used. GRP its white
dust :-)

Aluminium is simply too easy to take beyond the plastic limit. And tube
is easy to BUCKLE. Where the tube is not sheathed inside the structure,
is where the greatest compression occurs. Dead easy to get the top of
the tube buckle inwards. Solid rod doesn't do that..


Basically the stresses at the wing root, where forces are so high you
can more or less ignore the fact that the wing is clamped to the
fuselage, are pure cantilever bending. We tried 4mm wire but under even
mild manoeuvres the wing flex was pretty high. Given that the shafts
extend several inches into fairly close fitting tubes, this had to be
pure flex in the steel rods at the place where the tubes stop.
Ultimately what is needed is great stiffness at normal loadings, and
enough strength so that even under extreme G - pullout from a dive in
emergencies, if the wings flex, they don't permanently bend the rods
either. The ultimate breaking strain then becomes the spars more or less
where the rods end, which I have stressed to about 10G. That's enough
for this model. Some high performance gliders are stressed to around
100G, which is enough to cope with pullout from dive speeds up to about
200mph or more. World record is somewhere around 300mph, but this model
isn't intended for that sort of performance, or anything like it.


Anyway, I now feel confident that either will do as well. I suspect
silver steel has the slightly greater ultimate strength, so will go for
that. It's also more available.

There is no point in making the rod stronger than the wing itself
though. That's a classic tapered I beam of hardwood with balsa webbing
and a stressed skin over the lot where the stresses are highest.

On 2 June, 08:59, The Natural Philosopher
wrote:

Carbon fibre, Kite spar's easy to get and cheap enough in that size.

Not strong enough and too flexible.

What do you mean by "strong" (with numbers), is this for axial bending
or torsion, and likewise do you need stiffness to be axial bend or
torsional? Also do you care about stiffness / volume, or stiffness /
mass, because CF will beat steel easily by mass. If you're mass
limited rather than diameter then you could go to 10mm pultruded tube
that's enormously strong and still cheap, until you go to the woven
tubes.

dennis@home wrote:


"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models have
lost their wing joiners, and a new one needs some more. andd that's
going into production shortly.. It was just a case of which to buy
really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

You are right here.

After spending 25 years in the aerospace industry, I was always told not
to make something too strong, as it would transfer extra stess to
another component that was not designed to take it.

Dave

dennis@home wrote:


"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models have
lost their wing joiners, and a new one needs some more. andd that's
going into production shortly.. It was just a case of which to buy
really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

8 ft wingspan jobbies weighing 3lb, and not wanting to 'do an airbus' in
turbulence.

IIRC the top spar is stressed to about a 1/4 ton.

You can work it out yourself. The bending moment in a 10g manouever is
about 15lbs at half the sub span - 25" acting over half the chord depth
of 1.4"..so its 15 x 25 over .7"..I make that +- 500lb force or so.

Bending moment on the joiner is basically about 30 lb foot. That's more
or less concentrated over a few mm.

And that's only at 10g. That's a quite weather sailplane. The speed
ships have definitely been recorded with accelerometers at 40g+.

"Dave Baker" wrote in message
...

"The Natural Philosopher" wrote in message
...
Looking for some 6mm diameter steel shafting. Primary requirement is
stiffness. Is stainless better than silver steel?

LOL. Don't you realise that every type of steel, hardened or otherwise has
exactly the same Young's modulus

Not exactly the same, even if the difference won't be noticable in practice.

For example, at room temperature (21C) the Young's modulus of some different
types is:

Austinitic Stainless steel = 28.3
Low carbon steel (0.3% C) = 29.5
Cr-Mo steel 5%-9% Cr = 30.9

Colin Bignell

Dave wrote:
dennis@home wrote:


"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models have
lost their wing joiners, and a new one needs some more. andd that's
going into production shortly.. It was just a case of which to buy
really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

You are right here.

After spending 25 years in the aerospace industry, I was always told not
to make something too strong, as it would transfer extra stess to
another component that was not designed to take it.

Don't worry, the rest can take it! Its stiffness we want, and not
reaching the plastic limit. If the rest of the wing snaps, that's OK.

Normally I'd build the spars straight across, but a 100" wing is too big
for most cars..it needs to be joined in the middle.

The rod is in a tube glassed into ply spars and a the interspar webbing.

Plenty of transfer that way..
Dave

Andy Dingley wrote:
On 2 June, 08:59, The Natural Philosopher
wrote:

Carbon fibre, Kite spar's easy to get and cheap enough in that size.
Not strong enough and too flexible.

What do you mean by "strong" (with numbers), is this for axial bending
or torsion,

axial bending mainly.

and likewise do you need stiffness to be axial bend or
torsional?

Axial.

Also do you care about stiffness / volume, or stiffness /
mass, because CF will beat steel easily by mass.

Volume mainly. Weight is really not an issue. Not here.

If you're mass
limited rather than diameter then you could go to 10mm pultruded tube
that's enormously strong and still cheap, until you go to the woven
tubes.

Space is limited due to the need to have a straight rod in a gull wing.
And another reason why carbon is not ideal (although I use it
elsewhere) is that it wears sloppy.

See previous post. I want a rod that I can put inside a tube, with that
'held in a vice' and put 30lb foot on without it budging much, and with
luck capable of 120ft lb without snapping or deforming. After that the
wing snaps anyway, and I don't care that much :-)

As I said, it flew with 4mm, but wing flex was unacceptable.

"The Natural Philosopher" wrote in message
...
Dave wrote:
dennis@home wrote:


"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models have lost
their wing joiners, and a new one needs some more. andd that's going
into production shortly.. It was just a case of which to buy really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

You are right here.

After spending 25 years in the aerospace industry, I was always told not
to make something too strong, as it would transfer extra stess to another
component that was not designed to take it.

Don't worry, the rest can take it! Its stiffness we want, and not reaching
the plastic limit. If the rest of the wing snaps, that's OK.

Normally I'd build the spars straight across, but a 100" wing is too big
for most cars..it needs to be joined in the middle.

Don't joint it in the middle..
have removable wing tips.
There is less stress on the smaller wing tips so its easier.

dennis@home wrote:


"The Natural Philosopher" wrote in message
...
Dave wrote:
dennis@home wrote:


"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models have
lost their wing joiners, and a new one needs some more. andd that's
going into production shortly.. It was just a case of which to buy
really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

You are right here.

After spending 25 years in the aerospace industry, I was always told
not to make something too strong, as it would transfer extra stess to
another component that was not designed to take it.

Don't worry, the rest can take it! Its stiffness we want, and not
reaching the plastic limit. If the rest of the wing snaps, that's OK.

Normally I'd build the spars straight across, but a 100" wing is too
big for most cars..it needs to be joined in the middle.

Don't joint it in the middle..
have removable wing tips.
There is less stress on the smaller wing tips so its easier.


Then there is still the problem of removing the wing(s) from the fuselage.

Have a look at what it is. Google 'Minimoa'

I can assure you, thios was the lesser of many weevils.

"The Natural Philosopher" wrote in message
...
dennis@home wrote:


"The Natural Philosopher" wrote in message
...
Dave wrote:
dennis@home wrote:


"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models have
lost their wing joiners, and a new one needs some more. andd that's
going into production shortly.. It was just a case of which to buy
really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

You are right here.

After spending 25 years in the aerospace industry, I was always told
not to make something too strong, as it would transfer extra stess to
another component that was not designed to take it.

Don't worry, the rest can take it! Its stiffness we want, and not
reaching the plastic limit. If the rest of the wing snaps, that's OK.

Normally I'd build the spars straight across, but a 100" wing is too big
for most cars..it needs to be joined in the middle.

Don't joint it in the middle..
have removable wing tips.
There is less stress on the smaller wing tips so its easier.


Then there is still the problem of removing the wing(s) from the fuselage.

Have a look at what it is. Google 'Minimoa'

I can assure you, thios was the lesser of many weevils.

I think you are overdoing the stiffness requirement.. real planes aren't
stiff and there is no reason why a quarter scale model should be stiff.

If planes that big were made stiff they would fall out of the sky.

Its been a long time since I built a plane and never one that big but 6 mm
steel rods goes against my gut feeling.

I think I might have a go at building a quadrocopter though.

geoff wrote:

... it's also sold in just over 3' lengths.

39.3700787 inches by any chance?

--
Reentrant

dennis@home wrote:


"The Natural Philosopher" wrote in message
...
dennis@home wrote:


"The Natural Philosopher" wrote in message
...
Dave wrote:
dennis@home wrote:


"The Natural Philosopher" wrote in message
...

Oh..no need. we will be getting a fair bit in..several models
have lost their wing joiners, and a new one needs some more. andd
that's going into production shortly.. It was just a case of
which to buy really..

If you want the stuff to break on impact use wooden dowels.
How big are these wings and what are they made from?
Steel rod sounds far too strong for the job.

You are right here.

After spending 25 years in the aerospace industry, I was always
told not to make something too strong, as it would transfer extra
stess to another component that was not designed to take it.

Don't worry, the rest can take it! Its stiffness we want, and not
reaching the plastic limit. If the rest of the wing snaps, that's OK.

Normally I'd build the spars straight across, but a 100" wing is too
big for most cars..it needs to be joined in the middle.

Don't joint it in the middle..
have removable wing tips.
There is less stress on the smaller wing tips so its easier.


Then there is still the problem of removing the wing(s) from the
fuselage.

Have a look at what it is. Google 'Minimoa'

I can assure you, thios was the lesser of many weevils.

I think you are overdoing the stiffness requirement.. real planes aren't
stiff and there is no reason why a quarter scale model should be stiff.

All I want is that the wing joiner is not 3 times less stiff than the
rest of the wing.

If planes that big were made stiff they would fall out of the sky.


EEr..one just did! :-(

Its been a long time since I built a plane and never one that big but 6
mm steel rods goes against my gut feeling.

130" model we know of uses 10mm steel rod.

I think I might have a go at building a quadrocopter though.

Dont. Just buy one. The control electronics are fierce.

In message , Reentrant
writes
geoff wrote:

... it's also sold in just over 3' lengths.

39.3700787 inches by any chance?


That's a silly number of decimal places, isn't it

At what temperature would you expect a steel rod to be a metre to that
degree of accuracy

You weren't paying attention to my previous post, were you

I would expect 37 inches, the point being that you can cut the ends off
to get a 3' rod whose ends have not suffered from distortion or heating
effects from initial cutting

--
geoff