View Full Version : Why 2024?
My plans call for the use of 2024 1.5mm to use in the forming of
brackets
that will hold the bellcranks. Each part is doubled, (left and right
bracket
top and bottom parts on the bellcranks), so it seems to be extremly
strong.
Now, don't get me wrong, I can make a call today and order the
material that
it calls for, but at the moment I have quite a bit of the 6061 t-6
aluminum just
sitting here. So can anyone give me good reasons why I shouldn't use
this in
place of the 2024? Although I've read the materials data sheets on the
strengths
of each, It does seem to click for me of what the reason is for the
2024.
Any help?
Lou
Michelle P
May 29th 07, 03:58 PM
Lou wrote:
> My plans call for the use of 2024 1.5mm to use in the forming of
> brackets
> that will hold the bellcranks. Each part is doubled, (left and right
> bracket
> top and bottom parts on the bellcranks), so it seems to be extremly
> strong.
> Now, don't get me wrong, I can make a call today and order the
> material that
> it calls for, but at the moment I have quite a bit of the 6061 t-6
> aluminum just
> sitting here. So can anyone give me good reasons why I shouldn't use
> this in
> place of the 2024? Although I've read the materials data sheets on the
> strengths
> of each, It does seem to click for me of what the reason is for the
> 2024.
> Any help?
> Lou
>
6061 is too brittle. 2024 is a little softer and much lees likely to
crack. 6061 is more resistant to corrosion.
Charles Vincent
May 29th 07, 06:55 PM
Lou wrote:
> My plans call for the use of 2024 1.5mm to use in the forming of
> brackets
> that will hold the bellcranks. Each part is doubled, (left and right
> bracket
> top and bottom parts on the bellcranks), so it seems to be extremly
> strong.
> Now, don't get me wrong, I can make a call today and order the
> material that
> it calls for, but at the moment I have quite a bit of the 6061 t-6
> aluminum just
> sitting here. So can anyone give me good reasons why I shouldn't use
> this in
> place of the 2024? Although I've read the materials data sheets on the
> strengths
> of each, It does seem to click for me of what the reason is for the
> 2024.
> Any help?
> Lou
>
You neglected to mention the temper of the 2024 called for. In any
event, this seems like a question appropriate to the designer- only they
know why they specified 2024 for sure. Sometimes the decision is the
result of detailed analysis, sometimes it is non critical and only
because they had a scrap the right size laying around when they built
the prototype. Anyone else commenting is just speculating with the
information available, with their accuracy at best directly proportional
to the information given. I don't have a reference near to hand, but
believe that 2024 in T3 temper is about twice as strong as 6061 in T6,
and is more amenable to bending at sharper radii without cracking, but I
could likely be mis remembering.
Charles
Bob Kuykendall
May 29th 07, 07:02 PM
Earlier, Lou > wrote:
> My plans call for the use of 2024 1.5mm to use in the forming of
> brackets that will hold the bellcranks....
>
> So can anyone give me good reasons why I shouldn't use
> this in place of the 2024?
I've made bellcrank leaves and mounts out of .063" 6061-T6 where I was
sure that the applied stresses fell within the material properties.
For forming operations, one good reference is the table of minimum
bend radii reproduced in the Aircraft Spruce catalog:
http://www.aircraftspruce.com/catalog/mepages/aluminfo.php
There's nothing magic about 2024-T3. It is stronger than 6061-T6, and
a bit more expensive, and for many or most applications the extra
strength is worth the extra money. However, it has the same stiffness
as 6061, so for stiffness-bound applications there's not much point in
using 2024. Control push-pull tubes is a good example of this - one of
my favorite Stan Hall articles points out that push-pull tubes are
pretty universally stiffness-bound by buckling properties.
Anyhow, if you've done analysis on the mechanism and surrounding
structure, if you're confident you've correctly estimated the maximum
hinge moment, and also figured in reasonable (JAR 22 or Part 23 or
other appropriate) maximum input forces, and accounted for appropriate
safety factors, if you've accounted for 6061-T6's lower ultimate and
yield stesses, and found this to be a valid substitution, I say go for
it.
If you haven't done that analysis and are just guessing, sticking with
what the plans call for will save you some sleepless nights spent
second-guessing yourself.
As for another poster who says that 6061-T6 is too brittle, do you
have a cite for that very general assertion? How does that reconcile
with the fact that Zenith makes entire airplanes out of the stuff?
Thanks, Bob K.
http://www.hpaircraft.com/hp-24
On May 29, 12:02 pm, Bob Kuykendall > wrote:
> As for another poster who says that 6061-T6 is too brittle, do you
> have a cite for that very general assertion? How does that reconcile
> with the fact that Zenith makes entire airplanes out of the stuff?
>
> Thanks, Bob K.http://www.hpaircraft.com/hp-24
2024T3 (not Alclad) has a tensile ultimate of 70KSI and a yield of
50KSI, with elongation of 18% and a Brinell hardness of 120.
6061T6 has an ultimate of 45KSI and a yield of 40, elongation 12%,
Brinell 95.
So the 2024T3 is a LOT stronger but a little more ductile (so
less brittle?) and at the same time, strangely, harder. I wouldn't
replace the 2024 with the 6061 in anything I don't want to break.
References from Machinery's Handbook, 24th Ed., 1992.
Dan
Thanks Guys,
I'll be ordering the 2024 tommorow.
This is what I like about this group.
Lou
cavelamb himself
May 30th 07, 01:11 AM
Michelle P wrote:
> Lou wrote:
>
>> My plans call for the use of 2024 1.5mm to use in the forming of
>> brackets
>> that will hold the bellcranks. Each part is doubled, (left and right
>> bracket
>> top and bottom parts on the bellcranks), so it seems to be extremly
>> strong.
>> Now, don't get me wrong, I can make a call today and order the
>> material that
>> it calls for, but at the moment I have quite a bit of the 6061 t-6
>> aluminum just
>> sitting here. So can anyone give me good reasons why I shouldn't use
>> this in
>> place of the 2024? Although I've read the materials data sheets on the
>> strengths
>> of each, It does seem to click for me of what the reason is for the
>> 2024.
>> Any help?
>> Lou
>>
> 6061 is too brittle. 2024 is a little softer and much lees likely to
> crack. 6061 is more resistant to corrosion.
Huh?
About the brittleness.
I thought it was the other way around...
cavelamb himself
May 30th 07, 07:33 AM
Richard Riley wrote:
> On 29 May 2007 11:02:30 -0700, Bob Kuykendall >
> wrote:
>
>
>>As for another poster who says that 6061-T6 is too brittle, do you
>>have a cite for that very general assertion? How does that reconcile
>>with the fact that Zenith makes entire airplanes out of the stuff?
>
>
> Of course, that didn't work out so well when they made the Cricket.
Uh, because it was designed for 6061-T6?
On May 30, 7:43 am, Richard Riley > wrote:
> On Wed, 30 May 2007 06:33:10 GMT, cavelamb himself
>
>
>
>
>
> > wrote:
> >Richard Riley wrote:
>
> >> On 29 May 2007 11:02:30 -0700, Bob Kuykendall >
> >> wrote:
>
> >>>As for another poster who says that 6061-T6 is too brittle, do you
> >>>have a cite for that very general assertion? How does that reconcile
> >>>with the fact that Zenith makes entire airplanes out of the stuff?
>
> >> Of course, that didn't work out so well when they made the Cricket.
>
> >Uh, because it was designed for 6061-T6?
>
> I'm not speaking from personal knowledge, but it's been on the CriCri
> mailing list several times.
>
> The Cri-Cri was designed for 2024-T3 for the spar fittings and a few
> other places. When Zenith struck a deal to sell kits in the US they
> substituted 6061 and called it the Cricket.
>
> The results were very bad. To this day the designer refuses to sell
> plans within the US. - Hide quoted text -
>
> - Show quoted text -
The Hummelbird plans show 2024T3 for the wing spar attach
fittings, but it's not really obvious and if the builder is busy
cutting 6061 for all the other stuff he might just make them out of
it. Could be bad.
Dan
For all or you that are interested. I've made the brackets out
of 2024 and the 2024 bends harder, but doesn't seem to snap
as easy.
Lou
Orval Fairbairn
June 12th 07, 04:05 AM
In article om>,
Lou > wrote:
> For all or you that are interested. I've made the brackets out
> of 2024 and the 2024 bends harder, but doesn't seem to snap
> as easy.
> Lou
Of course, 2024-T3 doesn't snap as easily as 6061-T6! It is the "T
number" that determines brittleness (and stiffness).
GeorgeB
June 12th 07, 02:16 PM
On Tue, 12 Jun 2007 03:05:30 GMT, Orval Fairbairn
> wrote:
>In article om>,
> Lou > wrote:
>
>> For all or you that are interested. I've made the brackets out
>> of 2024 and the 2024 bends harder, but doesn't seem to snap
>> as easy.
>> Lou
>
>Of course, 2024-T3 doesn't snap as easily as 6061-T6! It is the "T
>number" that determines brittleness (and stiffness).
Orval, stiffness is the same for the same alloy, and substantially the
same for all aluminum alloys, independent of heat treatment
conditions. "T-number" has nothing to do with stiffness.
Yield strengths (and tensile, but yield is the one we USUALLY care
about) vary amont alloys and heat treatments.
2024 is about 5% "stiffer" than 6061. 2024-T4 yields about 40% more
in tension than 6061-T6 before breaking.
Orval Fairbairn
June 13th 07, 08:30 PM
In article >,
GeorgeB > wrote:
> On Tue, 12 Jun 2007 03:05:30 GMT, Orval Fairbairn
> > wrote:
>
> >In article om>,
> > Lou > wrote:
> >
> >> For all or you that are interested. I've made the brackets out
> >> of 2024 and the 2024 bends harder, but doesn't seem to snap
> >> as easy.
> >> Lou
> >
> >Of course, 2024-T3 doesn't snap as easily as 6061-T6! It is the "T
> >number" that determines brittleness (and stiffness).
>
> Orval, stiffness is the same for the same alloy, and substantially the
> same for all aluminum alloys, independent of heat treatment
> conditions. "T-number" has nothing to do with stiffness.
No, it isn't! Try to bend some .025 6061-T3 and then some 6061-T6. You
will find the T2 bends more easily.
> Yield strengths (and tensile, but yield is the one we USUALLY care
> about) vary amont alloys and heat treatments.
That is why "T-number" controls stiffness, since bending is the result
of inelastic deformation. It takes more torque to bend a piece of T6 vs
T3 of the same alloy and thickness.
> 2024 is about 5% "stiffer" than 6061. 2024-T4 yields about 40% more
> in tension than 6061-T6 before breaking.
Yes.
On Jun 13, 7:30 pm, Orval Fairbairn > wrote:
> In article >,
>
>
>
> GeorgeB > wrote:
> > On Tue, 12 Jun 2007 03:05:30 GMT, Orval Fairbairn
> > > wrote:
>
> > >In article om>,
> > > Lou > wrote:
>
> > >> For all or you that are interested. I've made the brackets out
> > >> of 2024 and the 2024 bends harder, but doesn't seem to snap
> > >> as easy.
> > >> Lou
>
> > >Of course, 2024-T3 doesn't snap as easily as 6061-T6! It is the "T
> > >number" that determines brittleness (and stiffness).
>
> > Orval, stiffness is the same for the same alloy, and substantially the
> > same for all aluminum alloys, independent of heat treatment
> > conditions. "T-number" has nothing to do with stiffness.
>
> No, it isn't! Try to bend some .025 6061-T3 and then some 6061-T6. You
> will find the T2 bends more easily.
Wrong. GeorgeB was correct.
You are confusing yield strength with stiffness.
Stiffness refers only to elastic deformation.
Strength refers only to plastic deformation.
Elastic deformation is when it bends and
then springs back to exactly the same
shape it was before. Plastic deformation
is when it stays bent.
The stiffness of a material is the ratio of stress to strain.
The formal name for that material property is the spring
constant or Young's modulus.
Ignoring allotropes for the sake of simplicity, the
stiffness of a material depends only on gross
composition and is independent of temper.
Thus all low-alloy steels have the same stiffness
which is just about the same as plain old iron.
Yield strength is the minimum stress that will
result in plastic deformation (e.g. a permanent
bend.)
Heat treatment affects yield (and ultimate strength.
So if you make a spring out of annealed 4130
and another out of hardened 4130 they will both
stretch the same amount for the same applied
force, so long as you do not apply so much force
that either is permanently stretched. (e.g. the
applied stress is in the elastic range) They are
equally stiff.
However the force that leaves the annealed spring
permanently deformed (yielded) is much less than
that which leaves the hardened spring deformed.
The hardened material is stronger, and so it
remains 'springy' over a range of stress that would
leave the other spring 'sprung'.
The difference between 'spring' steel and ordinary
steel is the strength, not the stiffness.
The same is true for all alloys, not just steel.
>
> > Yield strengths (and tensile, but yield is the one we USUALLY care
> > about) vary amont alloys and heat treatments.
>
> That is why "T-number" controls stiffness, since bending is the result
> of inelastic deformation. It takes more torque to bend a piece of T6 vs
> T3 of the same alloy and thickness.
Wrong. It takes equal torque to bend each
_in the elastic rage_. It takes more torque to
_yield_ the stronger piece.
'Bend' is ambiguous. You can bend the piece
and have it spring back all the way (elastic
deformation) or you can bend it and have it stay
bent (plastic deformation).
Stiffness refers only to the elastic deformation.
Strength refers only to the plastic deformation.
>
> > 2024 is about 5% "stiffer" than 6061. 2024-T4 yields about 40% more
> > in tension than 6061-T6 before breaking.
>
> Yes.
Yes.
--
FF
GeorgeB
June 15th 07, 02:15 PM
On Wed, 13 Jun 2007 19:30:04 GMT, Orval Fairbairn
> wrote:
>> >Of course, 2024-T3 doesn't snap as easily as 6061-T6! It is the "T
>> >number" that determines brittleness (and stiffness).
>>
>> Orval, stiffness is the same for the same alloy, and substantially the
>> same for all aluminum alloys, independent of heat treatment
>> conditions. "T-number" has nothing to do with stiffness.
>
>No, it isn't! Try to bend some .025 6061-T3 and then some 6061-T6. You
>will find the T2 bends more easily.
If you want to use incorrect terminology, that is fine. Stiffness has
nothing to do with plastic deformation. If you take the same size
piece of 5052, 6061, 2024, or 7075 and load them the same BEFORE
plastic deformation, you will see virtually no (less than 10%)
difference in deflection vs load.
A socket head capscrew, US, is about 220,000 psi yield strength. A
cheap hex head bolt is about 30,000p psi yield strength. For the same
load, before plastic (inelastic as you use) deformation, both will
stretch the same and recover the same.
>> Yield strengths (and tensile, but yield is the one we USUALLY care
>> about) vary among alloys and heat treatments.
>
>That is why "T-number" controls stiffness, since bending is the result
>of inelastic deformation. It takes more torque to bend a piece of T6 vs
>T3 of the same alloy and thickness.
Stiffness and INelastic (usually referred to as "plastic") deformation
have less in common than your and my knowledge of material science.
>> 2024 is about 5% "stiffer" than 6061. 2024-T4 yields about 40% more
>> in tension than 6061-T6 before breaking.
>
>Yes.
2024-T0 is 5% stiffer than 6061-T6. 6061-T6 is 25% stronger than
2024-T0.
On Jun 15, 7:15 am, GeorgeB > wrote:
> On Wed, 13 Jun 2007 19:30:04 GMT, Orval Fairbairn
>
> > wrote:
> >> >Of course, 2024-T3 doesn't snap as easily as 6061-T6! It is the "T
> >> >number" that determines brittleness (and stiffness).
>
> >> Orval, stiffness is the same for the same alloy, and substantially the
> >> same for all aluminum alloys, independent of heat treatment
> >> conditions. "T-number" has nothing to do with stiffness.
>
> >No, it isn't! Try to bend some .025 6061-T3 and then some 6061-T6. You
> >will find the T2 bends more easily.
>
> If you want to use incorrect terminology, that is fine. Stiffness has
> nothing to do with plastic deformation. If you take the same size
> piece of 5052, 6061, 2024, or 7075 and load them the same BEFORE
> plastic deformation, you will see virtually no (less than 10%)
> difference in deflection vs load.
>
> A socket head capscrew, US, is about 220,000 psi yield strength. A
> cheap hex head bolt is about 30,000p psi yield strength. For the same
> load, before plastic (inelastic as you use) deformation, both will
> stretch the same and recover the same.
>
> >> Yield strengths (and tensile, but yield is the one we USUALLY care
> >> about) vary among alloys and heat treatments.
>
> >That is why "T-number" controls stiffness, since bending is the result
> >of inelastic deformation. It takes more torque to bend a piece of T6 vs
> >T3 of the same alloy and thickness.
>
> Stiffness and INelastic (usually referred to as "plastic") deformation
> have less in common than your and my knowledge of material science.
>
> >> 2024 is about 5% "stiffer" than 6061. 2024-T4 yields about 40% more
> >> in tension than 6061-T6 before breaking.
>
> >Yes.
>
> 2024-T0 is 5% stiffer than 6061-T6. 6061-T6 is 25% stronger than
> 2024-T0.
You're not confusing 2024T4 with 2024T0, I hope?
Dan
clare at snyder.on.ca
June 15th 07, 10:07 PM
On Fri, 15 Jun 2007 11:43:05 -0700, wrote:
>On Jun 15, 7:15 am, GeorgeB > wrote:
>> On Wed, 13 Jun 2007 19:30:04 GMT, Orval Fairbairn
..
>>
>> If you want to use incorrect terminology, that is fine. Stiffness has
>> nothing to do with plastic deformation. If you take the same size
>> piece of 5052, 6061, 2024, or 7075 and load them the same BEFORE
>> plastic deformation, you will see virtually no (less than 10%)
>> difference in deflection vs load.
10% in my world is hardly "virtually no"
>>
--
Posted via a free Usenet account from http://www.teranews.com
Bob Kuykendall
June 15th 07, 11:18 PM
> 10% in my world is hardly "virtually no"
Ah, and where does "less than 10%" fall?
Craig[_2_]
June 16th 07, 12:21 AM
On Jun 15, 3:18 pm, Bob Kuykendall > wrote:
> > 10% in my world is hardly "virtually no"
>
> Ah, and where does "less than 10%" fall?
For those with the time and interest, MIL-HDBK-5H has just about
everything you might want to know about use of aluminum in aircraft
structures (see chapter 3). Other metals are covered too. It's
freely available on the web courtesy of our tax dollars.
"MILITARY HANDBOOK, METALLIC MATERIALS AND ELEMENTS FOR AEROSPACE
VEHICLE STRUCTURES"
http://snap.lbl.gov/pub/nj_bscw.cgi/d87465/MIL-HDBK-5H%20Design%20with%20Metals.pdf
Enjoy,
Craig
On Jun 15, 9:07 pm, clare at snyder.on.ca wrote:
> On Fri, 15 Jun 2007 11:43:05 -0700, wrote:
> >On Jun 15, 7:15 am, GeorgeB > wrote:
> >> On Wed, 13 Jun 2007 19:30:04 GMT, Orval Fairbairn
> .
>
> >> If you want to use incorrect terminology, that is fine. Stiffness has
> >> nothing to do with plastic deformation. If you take the same size
> >> piece of 5052, 6061, 2024, or 7075 and load them the same BEFORE
> >> plastic deformation, you will see virtually no (less than 10%)
> >> difference in deflection vs load.
>
> 10% in my world is hardly "virtually no"
>
>
Regardless, the reason 2024 than 6061 for
shop bent brackets is because it is stronger,
not because it is stiffer.
--
FF
GeorgeB
June 17th 07, 02:00 AM
On Fri, 15 Jun 2007 11:43:05 -0700, wrote:
>> 2024-T0 is 5% stiffer than 6061-T6. 6061-T6 is 25% stronger than
>> 2024-T0.
>
> You're not confusing 2024T4 with 2024T0, I hope?
>
> Dan
No, just pointing out that STIFFNESS, Youngs modulus, is independent
of "heat treat" condition. Yes, T4 is a heat treat condition, it just
takes place at room temperature. Strentgh and stiffness have very
little in common.
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