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

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.

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

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/catalo...s/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

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...

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