Aluminum composite reportedly stronger, lighter than carbon

[Wayne Paul]

I just saw the following on rec.aviation.soaring and thought it might be of
interest to this group.

From the Delft University:
www.compositesworld.com/news/cwweekly/2007/October/112036

Wayne
HP-14 "6F"
http://www.soaridaho.com/Schreder

[Morgans[_2_]]

"Wayne Paul" > wrote in message
...
>I just saw the following on rec.aviation.soaring and thought it might be of
>interest to this group.
>
> From the Delft University:
> www.compositesworld.com/news/cwweekly/2007/October/112036

Interesting. Let us know if you see any more on the details of the
composite.
--
Jim in NC

[JP[_1_]]

"Morgans" > wrote in
...
>
> "Wayne Paul" > wrote in message
> ...
>>I just saw the following on rec.aviation.soaring and thought it might be
>>of interest to this group.
>>
>> From the Delft University:
>> www.compositesworld.com/news/cwweekly/2007/October/112036
>
> Interesting. Let us know if you see any more on the details of the
> composite.
> --
> Jim in NC

Here's more about it:
http://www.greencarcongress.com/2007/09/new-material-fo.html

JP

[Ron Wanttaja]

On Wed, 03 Oct 2007 16:35:43 -0700, Richard Riley >
wrote:

> "Research is continuing to look at fatigue, as well as analysis of
> damage caused by corrosion, hail storms and other weather phenomena,
> including trucks that collide with aircraft while they’re on the
> ground."
>
> That's really bad weather.

When they say, "It's raining cats and dogs," one generally ISN'T thinking
CATerpillars and DOGdges. :-)

Ron Wanttaja

[Orval Fairbairn]

In article >,
"Wayne Paul" > wrote:

> I just saw the following on rec.aviation.soaring and thought it might be of
> interest to this group.
>
> From the Delft University:
> www.compositesworld.com/news/cwweekly/2007/October/112036
>
> Wayne
> HP-14 "6F"
> http://www.soaridaho.com/Schreder


They have to get the Young's Modulus to match, otherwise either the
aluminum or the matrix material will be carrying most of the load.

Anything coming from anything labeled "Green" is automatically suspect,
in my book, until I see a second (or third) opinion.

[Darrel Toepfer]

Ron Wanttaja > wrote in
:

> On Wed, 03 Oct 2007 16:35:43 -0700, Richard Riley
> > wrote:
>
>> "Research is continuing to look at fatigue, as well as analysis of
>> damage caused by corrosion, hail storms and other weather phenomena,
>> including trucks that collide with aircraft while they’re on the
>> ground."
>>
>> That's really bad weather.
>
> When they say, "It's raining cats and dogs," one generally ISN'T
> thinking CATerpillars and DOGdges. :-)

Can "transparent aluminum" be far behind?

I like this, they don't say how much it weighs though:

http://www.greencarcongress.com/2007/01/audi_introduces.html
Audi Introduces V12 Diesel Passenger Car Concept
7 January 2007

Leveraging the work it did with its V12 TDI R10 racing car (earlier
post), Audi has applied a 6.0-liter, Euro-5 compliant 12-cylinder diesel
TDI engine the first V12 passenger car engine in a concept version of
the Audi Q7. The Audi Q7 V12 TDI study delivers 368 kW (493 hp) and a
massive 1,000 Nm (737 lb-ft) of torque.

The power of the turbocharged V12 TDI takes the SUV from 0 to 100 kph in
5.5 seconds, with fuel consumption of 11.9 liters/100km (20 mpg US).

Performance of the engine.
The Q7 V12 TDI’s cylinders actually sweep a greater volume than the
racing engine, which has a capacity of 5.5 liters. Its 5,934 cc are
produced by a bore of 83.0 millimeters and a stroke of 91.4 mm, the same
dimensions as the six-cylinder 3.0 TDI.

The two banks of cylinders are positioned opposite one another with an
offset of 17 millimeters. Measuring just 684 mm long, the V12 diesel has
an extremely compact design that enables it to fit into the Q7.

The V12 TDI features the same 90 mm spacing between cylinders as the
other models in the V engine series. However, the cylinder banks are
placed at an angle of 60 degrees to one another instead of the customary
90 degrees. This particular V12 configuration suppresses all of the
inertial forces and mass moments which would otherwise cause vibrations.

The V12 TDI’s crankcase is made from a mixture of cast iron and
vermicular graphite. Audi already uses this high-tech material, known as
GJV-450, in the manufacture of the V6 TDI and V8 TDI. GJV-450, which is
produced using a patented casting method, is around 40% more rigid than
cast iron and twice as resistant to fatigue.

Use of this material enabled the development team to make the walls
thinner, paving the way for a potential weight-saving of around 15%
compared to conventional cast iron.

The crankshaft is forged from chrome-molybdenum alloy steel and is
mounted with the aid of an extremely rigid main bearing bridge made from
nodular cast iron. The forged connecting rods are cracked, and the
pistons are made from aluminium.

The two cylinder heads each comprise three main elements. The bottom
section, incorporating the intake and exhaust ports and through which
the coolant flows, is made from a low-pressure die-cast aluminium alloy
that has a high-strength, lightweight construction. The top section,
which conducts the oil, is pressure-cast. The cylinder head is crowned
by a reinforcing ladder-type frame which holds the two camshafts.


Piston and valve system for the V12.
The valves are actuated by four camshafts acting via low-friction
roller-type cam followers, the compression ratio is 16.0:1. The map-
controlled swirl variation of the combustion air deployed in the V6 and
V8 TDI models has been retained. With this system, one of the intake
ports for each cylinder is either opened or closed by means of an
electrically operated flap, depending on the engine’s operating point.
Intermediate flap positions are also possible. This allows the swirl to
be adjusted for optimum exhaust emissions combined with high power
delivery.

As is customary on V engines from Audi, the maintenance-free chain drive
is fitted in a space-saving location on the rear face of the engine. The
developers devised a new layout for the V12 TDI, however. The
crankshaft’s sprocket wheel meshes with an intermediate gear which in
turn drives the camshafts by means of two simplex chains. Two additional
chains drive the oil pump as well as both high-pressure pumps for the
common-rail injection system.

Bosch supplies a 2,000-bar injection system for the V12. The hole
diameter of the eight-hole injector nozzles has now been reduced to a
mere 0.12 millimeters. The high pressure produces an optimum spray
pattern inside the combustion chamber, which makes for a faster, more
homogeneous and, as a result, more acoustically refined ignition
process. The improved combustion efficiency increases power output while
reducing both fuel consumption and emissions.

More than 300 piezo discs are packed into each of the V12 TDI injectors,
which transmit the minimal expansion to the valve needle directly
(inline) without the need for any form of transmission mechanism between
the two. Each actuation takes just a few milliseconds.

The fuel pressure and quantity can be adjusted according to
requirements; the number of injection phases per power stroke can be
varied up to a maximum of five with the piezoelectric technology in the
V12 TDI. Main injection can be accompanied by both pilot and post-
injection phases. Pilot injection lessens the harshness of the
combustion sound, which is particularly noticeable at low engine loads.

The delayed post-injection of fuel serves to increase the temperature of
the exhaust gas. This allows any particulate residue to be burned off in
order to regenerate the two particulate filters which are included as
standard.

Two variable vane geometry turbochargers supply compressed air—each to
one bank of cylinders. The variable vane geometry ensures that the full
exhaust flow is directed through the turbine at all times. The
turbochargers offer fast response even at low rev speeds and attain a
high degree of efficiency.

Both turbochargers generate up to 2.6 bar of absolute boost pressure and
are key in achieving the peak torque of 1,000 Nm.

The temperature of the compressed air is reduced by two large
intercoolers. The V12 comes with a double-flow exhaust system featuring
two particulate filters. The intake system is similarly structured for
each bank of cylinders there is an air cleaner followed immediately by a
hot-film air mass meter. Two control units operating based on the
master-slave principle orchestrate proceedings inside the engine.


The Q7 V12 TDI study.
The Audi Q7 V12 TDI is Euro-5 compliant. At partial throttle, up to 50%
of the exhaust gases are fed back into the intake air via the Exhaust
Gas Recirculation system to reduce NOx emissions. The extensive
recirculation system incorporates a water cooler which reduces the
temperature of the exhaust gases sharply.

The V12 TDI is coupled with a new six-speed tiptronic transmission. The
quattro driveline splits the drive power 40:60 between the front and
rear wheels under normal driving conditions. This results in slightly
tail-heavy, sporty handling characteristics.

-

http://www.greencarcongress.com/2006/03/audi_diesel_win.html
Audi Diesel Wins Twelve Hours of Sebring Race
19 March 2006

The aluminum V12 TDI
Audi made racing history on Saturday as its diesel-powered Audi R10 TDI
won the Mobil 1 Twelve Hours of Sebring, becoming the first diesel car
in the world to win a major sports car race. Audi used Sebring as a test
for the 24 Hours of Le Mans race, set for June 17-18.

The new Audi R10 TDI is powered by a completely new all-aluminum, 5.5-
liter, twelve-cylinder bi-turbo TDI engine that delivers more than 485
kW (650 hp) and more than 1,100 Nm of torque.

The V12 TDI used in the R10 is the first Audi diesel engine with an
aluminium crankcase. The cylinder-bank angle is 90 degrees. The V12 TDI
has, like Audi production car engines, four valves per cylinder and twin
overhead camshafts. The common rail fuel injection system exceeds 1,600
bar, and ignition pressures reach values never previously seen in any
Audi engine. The V12 TDI is equipped with a pair of diesel particle
filters.

"This engine is the specifically most powerful diesel there is in the
world and, up until now, the biggest challenge that Audi Sport has ever
faced in its long history. There has never been anything remotely
comparable. We started development with a clean sheet of paper."

Ulrich Baretzky, Head of Engine Technology at Audi Sport
-
Audi wants to use its diesel work in motorsport to increase its
technology advantages in the commercial diesel engines. Every second
Audi sold today is delivered with a TDI diesel engine.
-
"With regard to fuel consumption, environmental friendliness, the
combustion process and other new technologies we expect an enormous push
in the coming years. We are still relatively close to the findings of
our colleagues from production since we are breaking completely new
ground in motorsport. However, this will change. I believe to be able to
share the things that we developed specifically for motorsport with
production in the future."

Ulrich Baretzky

[cavelamb himself[_4_]]

Orval Fairbairn wrote:
> In article >,
> "Wayne Paul" > wrote:
>
>
>>I just saw the following on rec.aviation.soaring and thought it might be of
>>interest to this group.
>>
>>From the Delft University:
>>www.compositesworld.com/news/cwweekly/2007/October/112036
>>
>>Wayne
>>HP-14 "6F"
>>http://www.soaridaho.com/Schreder
>
>
>
> They have to get the Young's Modulus to match, otherwise either the
> aluminum or the matrix material will be carrying most of the load.
>
> Anything coming from anything labeled "Green" is automatically suspect,
> in my book, until I see a second (or third) opinion.


Copy that. Orv.

I was a little bewildered how replacing he construction material was
going to save mega bux. Seems more like it would COST mega bux to
redesign for it...

Oh well, it's Green, therefore wonderful?

Right...


Richard

[cavelamb himself[_4_]]

Richard Riley wrote:
> On Thu, 04 Oct 2007 04:52:18 GMT, Darrel Toepfer >
> wrote:
>
>
>>Ron Wanttaja > wrote in
:
>>
>>
>>>On Wed, 03 Oct 2007 16:35:43 -0700, Richard Riley
> wrote:
>>>
>>>
>>>>"Research is continuing to look at fatigue, as well as analysis of
>>>>damage caused by corrosion, hail storms and other weather phenomena,
>>>>including trucks that collide with aircraft while they’re on the
>>>>ground."
>>>>
>>>>That's really bad weather.
>>>
>>>When they say, "It's raining cats and dogs," one generally ISN'T
>>>thinking CATerpillars and DOGdges. :-)
>>
>>Can "transparent aluminum" be far behind?
>
>
> You're behind the times. Transparent aluminum is commercially
> available, I have a sample on my desk. It's expensive - $10/sq. in -
> but more bulletproof than armored glass and half the weight. Google
> aluminum oxynitride or ALON.
>
> Star Trek 4 came out in 1986. The first patent for aluminum
> oxynitride as transparent aluminum - from Raytheon, patent 4720362 -
> was filed in 1985 and granted in 1988.

Damit Scotty!

You know the Prime Directive specifically prohibits passing advanced
technology to primitive cultures!!

[Darrel Toepfer]

Richard Riley > wrote:

> Star Trek 4 came out in 1986. The first patent for aluminum
> oxynitride as transparent aluminum - from Raytheon, patent 4720362 -
> was filed in 1985 and granted in 1988.

D@rn, but was it formulated on an old Mac with a wired mouse?

[Fred the Red Shirt]

On Oct 4, 4:52 am, Darrel Toepfer > wrote:
> Ron Wanttaja > wrote :
> ...
>
> Can "transparent aluminum" be far behind?
>

It's here now. Aluminum Oxide is transparent which is why telescope
mirrors which have a very thin layer to minimize defects, have to be
realuminized every few years ago.

That is also why the decision to change from Gold to Aluminum for
CDs probably reduced their archival life by several decades, just
my guess.

--

FF

[Steve Hix]

In article om>,
Fred the Red Shirt > wrote:

> On Oct 4, 4:52 am, Darrel Toepfer > wrote:
> > Ron Wanttaja > wrote
> > :
> > ...
> >
> > Can "transparent aluminum" be far behind?
> >
>
> It's here now. Aluminum Oxide is transparent which is why telescope
> mirrors which have a very thin layer to minimize defects, have to be
> realuminized every few years ago.

Um, sort of, not quite.

Aluminum oxide forms quickly on pure aluminum surfaces, which is a good
thing, corrosion-wise; it's very hard, has little effect on
reflectivity, and thus makes for a good mirror coating.

The thing is, it's not so much something you do, specifically, as
something that happens when aluminum is exposed to oxygen. And if you
scratch the surface, the scratch gets an immediate re-coat. Not that
you'd want to scratch your mirror at all, if you could possibly avoid it.

Eventually, though, dust and other sources of wear damage it and the
aluminum under it, and you've got to redo the aluminum coating; it's
only a few millionths to a few thousandths thick, from glass to air, so
it's easy to damage.

Fortunately, it's an easy process, and last a *lot* longer than
silvering the mirror, even though the silvered mirror, for the first few
minutes anyway, is a couple percent better than aluminum.

Then corrosion sets in...

Could be worse, we could still be using electrum or speculum metal to
make mirrors.

[J.Kahn]

Richard Riley wrote:

> including trucks that collide with aircraft while they’re on the
> ground."
>
> That's really bad weather.

Most common type of structural repair on regional airliners by far is
damage from ground vehicles.

John

[Chris Wells]

Could be worse, we could still be using electrum or speculum metal to
make mirrors.

Or using large vats of mercury.

[Steve Hix]

In article >,
Chris Wells > wrote:

> > Could be worse, we could still be using electrum or speculum metal to
> > make mirrors.
>
> Or using large vats of mercury.

Actually, I think someone is doing just that.

A pool of mercury is spun up to form a curved surface, used as the
mirror for, I think, a solar telescope.

Lessee... Ah:

http://www.astro.ubc.ca/LMT/lm/index.html

The focal length is dependent on the rate of spin. Kewl.

The first ones were made in 1872, there are more modern ones in use now,
running up to 3m in diameter. Turns out to be several "someones", and
plans for more are being considered. Even proposals for putting some on
the moon.

Hold your breath in the observatory...

[Chris Wells]

> Or using large vats of mercury.

Actually, I think someone is doing just that.

I know, it was supposed to be a joke.

[Morgans[_2_]]

"JP" > wrote
>
> Here's more about it:
> http://www.greencarcongress.com/2007/09/new-material-fo.html

Did anyone see a thickness for the composite aluminum sandwich?
--
Jim in NC

[Fred the Red Shirt]

On Oct 5, 5:26 pm, Steve Hix > wrote:
> In article om>,
> Fred the Red Shirt > wrote:
>
> > On Oct 4, 4:52 am, Darrel Toepfer > wrote:
> > > Ron Wanttaja > wrote
> > > :
> > > ...
>
> > > Can "transparent aluminum" be far behind?
>
> > It's here now. Aluminum Oxide is transparent which is why telescope
> > mirrors which have a very thin layer to minimize defects, have to be
> > realuminized every few years ago.
>
> Um, sort of, not quite.
>
> Aluminum oxide forms quickly on pure aluminum surfaces, which is a good
> thing, corrosion-wise; it's very hard, has little effect on
> reflectivity, and thus makes for a good mirror coating.
>
> The thing is, it's not so much something you do, specifically, as
> something that happens when aluminum is exposed to oxygen. And if you
> scratch the surface, the scratch gets an immediate re-coat. Not that
> you'd want to scratch your mirror at all, if you could possibly avoid it.
>
> Eventually, though, dust and other sources of wear damage it and the
> aluminum under it, and you've got to redo the aluminum coating; it's
> only a few millionths to a few thousandths thick, from glass to air, so
> it's easy to damage.
>
> Fortunately, it's an easy process, and last a *lot* longer than
> silvering the mirror, even though the silvered mirror, for the first few
> minutes anyway, is a couple percent better than aluminum.
>

Obviously you have not seen how a telescope mirror ages over the
years. The coating gradually becomes more and more transparent
over the years.

This happens even if you never clean, and therefor never damage
your mirror. It is certainly not due to wear! Clearly (no pun
intended)
the typical coating is thin enough that as the oxide layer slowly
thickens
the transparency rises.

Were wear alone responsible, the change would be episodic, not
gradual, and would not happen at all between cleanings.

> Could be worse, we could still be using electrum or speculum metal to
> make mirrors.

Yeah.

--

FF

[Steve Hix]

In article . com>,
Fred the Red Shirt > wrote:

> On Oct 5, 5:26 pm, Steve Hix > wrote:
> > In article om>,
> > Fred the Red Shirt > wrote:
> >
> > > On Oct 4, 4:52 am, Darrel Toepfer > wrote:
> > > > Ron Wanttaja > wrote
> > > > :
> > > > ...
> >
> > > > Can "transparent aluminum" be far behind?
> >
> > > It's here now. Aluminum Oxide is transparent which is why telescope
> > > mirrors which have a very thin layer to minimize defects, have to be
> > > realuminized every few years ago.
> >
> > Um, sort of, not quite.
> >
> > Aluminum oxide forms quickly on pure aluminum surfaces, which is a good
> > thing, corrosion-wise; it's very hard, has little effect on
> > reflectivity, and thus makes for a good mirror coating.
> >
> > The thing is, it's not so much something you do, specifically, as
> > something that happens when aluminum is exposed to oxygen. And if you
> > scratch the surface, the scratch gets an immediate re-coat. Not that
> > you'd want to scratch your mirror at all, if you could possibly avoid it.
> >
> > Eventually, though, dust and other sources of wear damage it and the
> > aluminum under it, and you've got to redo the aluminum coating; it's
> > only a few millionths to a few thousandths thick, from glass to air, so
> > it's easy to damage.
> >
> > Fortunately, it's an easy process, and last a *lot* longer than
> > silvering the mirror, even though the silvered mirror, for the first few
> > minutes anyway, is a couple percent better than aluminum.
>
> Obviously you have not seen how a telescope mirror ages over the
> years.

Guess again.

It's easy to recoat the mirror, so it's not so much of a problem,
certainly less of one than dealing with silver corrosion.

> The coating gradually becomes more and more transparent
> over the years.
>
> This happens even if you never clean, and therefor never damage
> your mirror. It is certainly not due to wear! Clearly (no pun
> intended)
> the typical coating is thin enough that as the oxide layer slowly
> thickens
> the transparency rises.
>
> Were wear alone responsible, the change would be episodic, not
> gradual, and would not happen at all between cleanings.
>
> > Could be worse, we could still be using electrum or speculum metal to
> > make mirrors.
>
> Yeah.
>
> --
>
> FF

[Fred the Red Shirt]

On Oct 9, 11:53 pm, Steve Hix >
wrote:
> In article . com>,
> Fred the Red Shirt > wrote:
>
>
> ...
>
> > Obviously you have not seen how a telescope mirror ages over the
> > years.
>
> Guess again.

Well then you should have observed that the transparency increases
between cleanings.

>
> It's easy to recoat the mirror, so it's not so much of a problem,
> certainly less of one than dealing with silver corrosion.

While it is not a technologically daunting task, it is not cheap for
larger mirrors especially when you consider shipping. I have a 17.5"
mirror that will need realuminizing when I finally get around to
putting
it into a scope. It has been cleaned exactly once, but the coating
is nearly gone entirely after 30 years in storage.

Offhand, do you know anyone who recoats mirrors that size?

--

FF

[Blueskies]

"Fred the Red Shirt" > wrote in message
oups.com...
> While it is not a technologically daunting task, it is not cheap for
> larger mirrors especially when you consider shipping. I have a 17.5"
> mirror that will need realuminizing when I finally get around to
> putting
> it into a scope. It has been cleaned exactly once, but the coating
> is nearly gone entirely after 30 years in storage.
>
> Offhand, do you know anyone who recoats mirrors that size?
>
> --
>
> FF
>

Maybe these guys: http://www.newportglass.com/nigcap.htm

http://www.johndobson.org/links.html

[Roger (K8RI)]

On Wed, 10 Oct 2007 15:49:48 -0700, Fred the Red Shirt
> wrote:

>On Oct 9, 11:53 pm, Steve Hix >
>wrote:
>> In article . com>,
>> Fred the Red Shirt > wrote:
>>
>>
>> ...
>>
>> > Obviously you have not seen how a telescope mirror ages over the
>> > years.
>>
>> Guess again.
>
>Well then you should have observed that the transparency increases
>between cleanings.
>
>>
>> It's easy to recoat the mirror, so it's not so much of a problem,
>> certainly less of one than dealing with silver corrosion.
>
>While it is not a technologically daunting task, it is not cheap for

IF you have the equipment (vacuum chamber, heater for vaporizing
Aluminum) it's relatively simple. One of our Astronomy club members
does up to 10 or 12" for the locals. IIRC his favorite source of
Aluminum is peeling the foil off gum wrappers although regular
Aluminum foil works. It just takes more power.

It doesn't take a super high vacuum either. Just one high enough to
develop a plasma although that's not part of the process.

On local used the chemical process for coating which worked pretty
well, but the coating isn't nearly as even as vacuum deposition.

>larger mirrors especially when you consider shipping. I have a 17.5"
>mirror that will need realuminizing when I finally get around to
>putting
>it into a scope. It has been cleaned exactly once, but the coating
>is nearly gone entirely after 30 years in storage.
>
>Offhand, do you know anyone who recoats mirrors that size?

Not that size, but there are a number of labs that do the work and I
think I saw a couple of links listed.

Roger (K8RI).

[Roger (K8RI)]

On Thu, 04 Oct 2007 02:36:51 -0500, cavelamb himself
> wrote:

>Orval Fairbairn wrote:
>> In article >,
>> "Wayne Paul" > wrote:
>>
>>
>>>I just saw the following on rec.aviation.soaring and thought it might be of
>>>interest to this group.
>>>
>>>From the Delft University:
>>>www.compositesworld.com/news/cwweekly/2007/October/112036
>>>
>>>Wayne
>>>HP-14 "6F"
>>>http://www.soaridaho.com/Schreder
>>
>>
>>
>> They have to get the Young's Modulus to match, otherwise either the
>> aluminum or the matrix material will be carrying most of the load.
>>
>> Anything coming from anything labeled "Green" is automatically suspect,
>> in my book, until I see a second (or third) opinion.
>
>
>Copy that. Orv.
>
>I was a little bewildered how replacing he construction material was
>going to save mega bux. Seems more like it would COST mega bux to
>redesign for it...
>
>Oh well, it's Green, therefore wonderful?

I don't think I'd call Aluminum a "green" material.

Roger (K8RI)
>
>Right...
>
>
>Richard

[Fred the Red Shirt]

On Oct 15, 4:44 am, "Roger (K8RI)" > wrote:
> On Wed, 10 Oct 2007 15:49:48 -0700, Fred the Red Shirt
>
>
>
> > wrote:
> >On Oct 9, 11:53 pm, Steve Hix >
> >wrote:
> >> In article . com>,
> >> Fred the Red Shirt > wrote:
>
> >> ...
>
> >> > Obviously you have not seen how a telescope mirror ages over the
> >> > years.
>
> >> Guess again.
>
> >Well then you should have observed that the transparency increases
> >between cleanings.
>
> >> It's easy to recoat the mirror, so it's not so much of a problem,
> >> certainly less of one than dealing with silver corrosion.
>
> >While it is not a technologically daunting task, it is not cheap for
>
> IF you have the equipment (vacuum chamber, heater for vaporizing
> Aluminum) it's relatively simple. One of our Astronomy club members
> does up to 10 or 12" for the locals. IIRC his favorite source of
> Aluminum is peeling the foil off gum wrappers although regular
> Aluminum foil works. It just takes more power.

Surface Preparation (cleaning) is extremely important as traces
or organics (from handling( will prevent adhesion of the aluminum.

Texereau recommends final cleaning by electron bombardment
in the vacuum chamber.


>
> It doesn't take a super high vacuum either. Just one high enough to
> develop a plasma although that's not part of the process.
>
> On local used the chemical process for coating which worked pretty
> well, but the coating isn't nearly as even as vacuum deposition.

Described by Texereau also, assuming you mean the chemical silvering
process.

>
> >larger mirrors especially when you consider shipping. I have a 17.5"
> >mirror that will need realuminizing when I finally get around to
> >putting
> >it into a scope. It has been cleaned exactly once, but the coating
> >is nearly gone entirely after 30 years in storage.
>
> >Offhand, do you know anyone who recoats mirrors that size?
>
> Not that size, but there are a number of labs that do the work and I
> think I saw a couple of links listed.
>

The place to ask would be sci.astro.amateur. I asked
OP as it looked like maybe he might know one.

--

FF

[Roger (K8RI)]

On Fri, 26 Oct 2007 09:53:04 -0700, Fred the Red Shirt
> wrote:

>On Oct 15, 4:44 am, "Roger (K8RI)" > wrote:
>> On Wed, 10 Oct 2007 15:49:48 -0700, Fred the Red Shirt
>>
>>
>>
>> > wrote:
>> >On Oct 9, 11:53 pm, Steve Hix >
>> >wrote:
>> >> In article . com>,
>> >> Fred the Red Shirt > wrote:
>>
>> >> ...
>>
>> >> > Obviously you have not seen how a telescope mirror ages over the
>> >> > years.
>>
>> >> Guess again.
>>
>> >Well then you should have observed that the transparency increases
>> >between cleanings.
>>
>> >> It's easy to recoat the mirror, so it's not so much of a problem,
>> >> certainly less of one than dealing with silver corrosion.
>>
>> >While it is not a technologically daunting task, it is not cheap for
>>
>> IF you have the equipment (vacuum chamber, heater for vaporizing
>> Aluminum) it's relatively simple. One of our Astronomy club members
>> does up to 10 or 12" for the locals. IIRC his favorite source of
>> Aluminum is peeling the foil off gum wrappers although regular
>> Aluminum foil works. It just takes more power.
>
>Surface Preparation (cleaning) is extremely important as traces
>or organics (from handling( will prevent adhesion of the aluminum.
>
>Texereau recommends final cleaning by electron bombardment
>in the vacuum chamber.

Which reminded me, my friend uses that plasma for the final cleaning.
Thats a lot of electronic bombardment. <:-))

>
>
>>
>> It doesn't take a super high vacuum either. Just one high enough to
>> develop a plasma although that's not part of the process.
>>
>> On local used the chemical process for coating which worked pretty
>> well, but the coating isn't nearly as even as vacuum deposition.
>
>Described by Texereau also, assuming you mean the chemical silvering
>process.

I do and it was.

>
>>
>> >larger mirrors especially when you consider shipping. I have a 17.5"
>> >mirror that will need realuminizing when I finally get around to
>> >putting
>> >it into a scope. It has been cleaned exactly once, but the coating
>> >is nearly gone entirely after 30 years in storage.
>>
>> >Offhand, do you know anyone who recoats mirrors that size?
>>
>> Not that size, but there are a number of labs that do the work and I
>> think I saw a couple of links listed.
>>
>
>The place to ask would be sci.astro.amateur. I asked
>OP as it looked like maybe he might know one.

I had forgotten about that group and I used to follow it.

Roger (K8RI)

[Fred the Red Shirt]

On Oct 26, 2:04 pm, "Roger (K8RI)" > wrote:
> On Fri, 26 Oct 2007 09:53:04 -0700, Fred the Red Shirt
> ...
> >Surface Preparation (cleaning) is extremely important as traces
> >or organics (from handling( will prevent adhesion of the aluminum.
>
> >Texereau recommends final cleaning by electron bombardment
> >in the vacuum chamber.
>
> Which reminded me, my friend uses that plasma for the final cleaning.
> Thats a lot of electronic bombardment. <:-))
>
>

How big is his vacuum chamber?

What sort of vacuum pump(s) does he use?

One large enough for a 17.5" mirror is rather non-trivial. Assuming
a 20" diameter cylindrical chamber, the top and bottom would need
to support over 3000 pounds each, if the work is done at sea level.

--

FF

[Mark Hickey]

Fred the Red Shirt > wrote:

>How big is his vacuum chamber?
>
>What sort of vacuum pump(s) does he use?
>
>One large enough for a 17.5" mirror is rather non-trivial. Assuming
>a 20" diameter cylindrical chamber, the top and bottom would need
>to support over 3000 pounds each, if the work is done at sea level.

Is it really that hard to build a vacuum chamber? Seems to me that
the most pressure it'll ever experience is about 15psi (1 bar), while
it's trivial to build/buy pressure containers that can handle 10-100x
that much (positive) pressure. Certainly if building a 1 bar vessel
20" in diameter is daunting, building a submarine (or worse, a
deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
below sea level, resisting a pressure of about 1,100 bar) would be
unthinkable.

Or am I missing something?

Mark "under pressure" Hickey

[Maxwell]

"Mark Hickey" > wrote in message
...
> Fred the Red Shirt > wrote:
>
>>How big is his vacuum chamber?
>>
>>What sort of vacuum pump(s) does he use?
>>
>>One large enough for a 17.5" mirror is rather non-trivial. Assuming
>>a 20" diameter cylindrical chamber, the top and bottom would need
>>to support over 3000 pounds each, if the work is done at sea level.
>
> Is it really that hard to build a vacuum chamber? Seems to me that
> the most pressure it'll ever experience is about 15psi (1 bar), while
> it's trivial to build/buy pressure containers that can handle 10-100x
> that much (positive) pressure. Certainly if building a 1 bar vessel
> 20" in diameter is daunting, building a submarine (or worse, a
> deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
> below sea level, resisting a pressure of about 1,100 bar) would be
> unthinkable.
>
> Or am I missing something?
>

Maybe, maybe not. Round pressure vessels keep their shell walls in tension,
hence the more pressure the better they hold their shape. Vacuum vessels are
just the opposite, and quite often much easier to collapse than one might
naturally assume.

I can say I once built a round vacuum chamber out of rolled 1/4" aluminum.
It was approximately 18" long and 18" in diameter. The bottom was 3/8"
aluminum, and the top was 1" clear plastic. The chamber was successful with
up to an near perfect vacuum, and used many times without failure. At
maximum vacuum, the bottom would dish approximately 1/8 to 3/16" inch, an
the plastic top would dish about 1/2".

I have a chamber I use now for another purpose, but it is only 6" in
diameter. The top for it is just 3/16" tempered glass.

Hope the number might help your estimates.

Max

[cavelamb himself[_4_]]

Maxwell wrote:

> "Mark Hickey" > wrote in message
> ...
>
>>Fred the Red Shirt > wrote:
>>
>>
>>>How big is his vacuum chamber?
>>>
>>>What sort of vacuum pump(s) does he use?
>>>
>>>One large enough for a 17.5" mirror is rather non-trivial. Assuming
>>>a 20" diameter cylindrical chamber, the top and bottom would need
>>>to support over 3000 pounds each, if the work is done at sea level.
>>
>>Is it really that hard to build a vacuum chamber? Seems to me that
>>the most pressure it'll ever experience is about 15psi (1 bar), while
>>it's trivial to build/buy pressure containers that can handle 10-100x
>>that much (positive) pressure. Certainly if building a 1 bar vessel
>>20" in diameter is daunting, building a submarine (or worse, a
>>deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
>>below sea level, resisting a pressure of about 1,100 bar) would be
>>unthinkable.
>>
>>Or am I missing something?
>>
>
>
> Maybe, maybe not. Round pressure vessels keep their shell walls in tension,
> hence the more pressure the better they hold their shape. Vacuum vessels are
> just the opposite, and quite often much easier to collapse than one might
> naturally assume.
>
> I can say I once built a round vacuum chamber out of rolled 1/4" aluminum.
> It was approximately 18" long and 18" in diameter. The bottom was 3/8"
> aluminum, and the top was 1" clear plastic. The chamber was successful with
> up to an near perfect vacuum, and used many times without failure. At
> maximum vacuum, the bottom would dish approximately 1/8 to 3/16" inch, an
> the plastic top would dish about 1/2".
>
> I have a chamber I use now for another purpose, but it is only 6" in
> diameter. The top for it is just 3/16" tempered glass.
>
> Hope the number might help your estimates.
>
> Max
>
>
>

You know, an ABSOLUTE vacuum is only 15 psi...

[Maxwell]

"cavelamb himself" > wrote in message
...
>
> You know, an ABSOLUTE vacuum is only 15 psi...

Correct, one atmosphere, what is your point?

[Fred the Red Shirt]

On Nov 1, 6:07 pm, "Maxwell" > wrote:
> "cavelamb himself" > wrote in message
>
> ...
>
>
>
> > You know, an ABSOLUTE vacuum is only 15 psi...
>
> Correct, one atmosphere, what is your point?

Wrong.

Absolute vacuum is 0 psia.

At sea level that will be about -14.7 psig.

Go to Death Valley or underwater and it will be less.

--

FF

[Fred the Red Shirt]

On Nov 1, 12:21 pm, "Maxwell" > wrote:
> "Mark Hickey" > wrote in message
>
> ...
>
>
>
> > Fred the Red Shirt > wrote:
>
> >>How big is his vacuum chamber?
>
> >>What sort of vacuum pump(s) does he use?
>
> >>One large enough for a 17.5" mirror is rather non-trivial. Assuming
> >>a 20" diameter cylindrical chamber, the top and bottom would need
> >>to support over 3000 pounds each, if the work is done at sea level.
>
> > Is it really that hard to build a vacuum chamber? Seems to me that
> > the most pressure it'll ever experience is about 15psi (1 bar), while
> > it's trivial to build/buy pressure containers that can handle 10-100x
> > that much (positive) pressure. Certainly if building a 1 bar vessel
> > 20" in diameter is daunting, building a submarine (or worse, a
> > deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
> > below sea level, resisting a pressure of about 1,100 bar) would be
> > unthinkable.
>
> > Or am I missing something?
>
> Maybe, maybe not. Round pressure vessels keep their shell walls in tension,
> hence the more pressure the better they hold their shape. Vacuum vessels are
> just the opposite, and quite often much easier to collapse than one might
> naturally assume.
>
> I can say I once built a round vacuum chamber out of rolled 1/4" aluminum.
> It was approximately 18" long and 18" in diameter. The bottom was 3/8"
> aluminum, and the top was 1" clear plastic. The chamber was successful with
> up to an near perfect vacuum, and used many times without failure. At
> maximum vacuum, the bottom would dish approximately 1/8 to 3/16" inch, an
> the plastic top would dish about 1/2".
>
> I have a chamber I use now for another purpose, but it is only 6" in
> diameter. The top for it is just 3/16" tempered glass.
>
> Hope the number might help your estimates.
>

Ok so at 18" diameter that clear plastic dish had a surface area
of about 254 square inches, so it saw a force of about 3700 lbs,
less if you were significantly above sea level.

--

FF

[Fred the Red Shirt]

On Nov 1, 8:53 am, Mark Hickey > wrote:
> Fred the Red Shirt > wrote:
>
> >How big is his vacuum chamber?
>
> >What sort of vacuum pump(s) does he use?
>
> >One large enough for a 17.5" mirror is rather non-trivial. Assuming
> >a 20" diameter cylindrical chamber, the top and bottom would need
> >to support over 3000 pounds each, if the work is done at sea level.
>
> Is it really that hard to build a vacuum chamber?

No, but it is much easier to build a small one than a large one.

> Seems to me that
> the most pressure it'll ever experience is about 15psi (1 bar), while
> it's trivial to build/buy pressure containers that can handle 10-100x
> that much (positive) pressure. Certainly if building a 1 bar vessel
> 20" in diameter is daunting, building a submarine (or worse, a
> deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
> below sea level, resisting a pressure of about 1,100 bar) would be
> unthinkable.
>
> Or am I missing something?

Buckling.

The skin of a pressure vessel is in almost pure tension, so they can
be thin and not buckle. Any bending moment on a flat section bows
it outward reducing the bending moment (essentially converting it to
tension) The sides of vacuum vessel see compression and bending,
and any flat sections will buckle inward which will increase the
bending
moment.

The bathyscape and similar vessels are cylindrical with hemi-spherical
ends so that their skin is in almost pure compression with very little
bending moment.

A 55-gallon drum can be cut down to make the sides of the vacuum
chamber but I'm not clear on how to make the end hemispherical.
An option is to use nested vessels, with partial vacuum between them.

There is a reason why bell jars have a hemispherical top, and it is
not esthetics.

--

FF

[Maxwell]

"Fred the Red Shirt" > wrote in message
oups.com...
>
> Ok so at 18" diameter that clear plastic dish had a surface area
> of about 254 square inches, so it saw a force of about 3700 lbs,
> less if you were significantly above sea level.
>

Yes.

Another way to consider it, is that the 18" diameter, 1/4" wall aluminum
tube has to support the approximate weight of a small SUV.

[Roger (K8RI)]

On Wed, 31 Oct 2007 20:32:08 -0700, Fred the Red Shirt
> wrote:

>On Oct 26, 2:04 pm, "Roger (K8RI)" > wrote:
>> On Fri, 26 Oct 2007 09:53:04 -0700, Fred the Red Shirt
>> ...
>> >Surface Preparation (cleaning) is extremely important as traces
>> >or organics (from handling( will prevent adhesion of the aluminum.
>>
>> >Texereau recommends final cleaning by electron bombardment
>> >in the vacuum chamber.
>>
>> Which reminded me, my friend uses that plasma for the final cleaning.
>> Thats a lot of electronic bombardment. <:-))
>>
>>
>
>How big is his vacuum chamber?
>
>What sort of vacuum pump(s) does he use?

The roughing pump is a two stage, dual vane, rotary pump with IIRC a
2.6 Liter capacity. (It's big and heavy any way and uses a 1 HP motor)

The diffusion pump is a 10" Siemens with a 3 stage chimney, but no
cold trap. The cold trap is there but only serves as a baffle without
cooling and appears to stop back gassing. It uses about 100 ml of 704
or 705 fluid (although the pump works well with anything between 50
and 150 ml).

>
>One large enough for a 17.5" mirror is rather non-trivial. Assuming
>a 20" diameter cylindrical chamber, the top and bottom would need
>to support over 3000 pounds each, if the work is done at sea level.

He has a quartz bell jar that is (again IIRC) about 18"in diameter and
close to 18" tall or a bit more. Ultimate vacuum is probably on the
order of 1.2 or 1.3 X 10^-6 or -7 Torr although it doesn't need to go
that high.

Roger (K8RI)

[Roger (K8RI)]

On Thu, 1 Nov 2007 12:21:03 -0500, "Maxwell" >
wrote:

>
>"Mark Hickey" > wrote in message
...
>> Fred the Red Shirt > wrote:
>>
>>>How big is his vacuum chamber?
>>>
>>>What sort of vacuum pump(s) does he use?
>>>
>>>One large enough for a 17.5" mirror is rather non-trivial. Assuming
>>>a 20" diameter cylindrical chamber, the top and bottom would need
>>>to support over 3000 pounds each, if the work is done at sea level.
>>
>> Is it really that hard to build a vacuum chamber? Seems to me that
>> the most pressure it'll ever experience is about 15psi (1 bar), while
>> it's trivial to build/buy pressure containers that can handle 10-100x
>> that much (positive) pressure. Certainly if building a 1 bar vessel
>> 20" in diameter is daunting, building a submarine (or worse, a
>> deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
>> below sea level, resisting a pressure of about 1,100 bar) would be
>> unthinkable.
>>
>> Or am I missing something?
>>
>
>Maybe, maybe not. Round pressure vessels keep their shell walls in tension,
>hence the more pressure the better they hold their shape. Vacuum vessels are
>just the opposite, and quite often much easier to collapse than one might
>naturally assume.
>
>I can say I once built a round vacuum chamber out of rolled 1/4" aluminum.
>It was approximately 18" long and 18" in diameter. The bottom was 3/8"
>aluminum, and the top was 1" clear plastic. The chamber was successful with
>up to an near perfect vacuum, and used many times without failure. At
>maximum vacuum, the bottom would dish approximately 1/8 to 3/16" inch, an
>the plastic top would dish about 1/2".

We used to use this on glass plates to grind the corrector for a
schmidt casagrain. Warp the glass with the vacuum, grind to a
parabola, and then release the vacuum. In this case it took a lot
more work than to explain. <:-))

Roger (K8RI)

>
>I have a chamber I use now for another purpose, but it is only 6" in
>diameter. The top for it is just 3/16" tempered glass.
>
>Hope the number might help your estimates.
>
>Max
>
>

[Roger (K8RI)]

On Thu, 01 Nov 2007 17:38:59 -0500, cavelamb himself
> wrote:

>Maxwell wrote:
>
>> "Mark Hickey" > wrote in message
>> ...
>>
>>>Fred the Red Shirt > wrote:
>>>
>>>
>>>>How big is his vacuum chamber?
>>>>
>>>>What sort of vacuum pump(s) does he use?
>>>>
>>>>One large enough for a 17.5" mirror is rather non-trivial. Assuming
>>>>a 20" diameter cylindrical chamber, the top and bottom would need
>>>>to support over 3000 pounds each, if the work is done at sea level.
>>>
>>>Is it really that hard to build a vacuum chamber? Seems to me that
>>>the most pressure it'll ever experience is about 15psi (1 bar), while
>>>it's trivial to build/buy pressure containers that can handle 10-100x
>>>that much (positive) pressure. Certainly if building a 1 bar vessel
>>>20" in diameter is daunting, building a submarine (or worse, a
>>>deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
>>>below sea level, resisting a pressure of about 1,100 bar) would be
>>>unthinkable.
>>>
>>>Or am I missing something?
>>>
>>
>>
>> Maybe, maybe not. Round pressure vessels keep their shell walls in tension,
>> hence the more pressure the better they hold their shape. Vacuum vessels are
>> just the opposite, and quite often much easier to collapse than one might
>> naturally assume.
>>
>> I can say I once built a round vacuum chamber out of rolled 1/4" aluminum.
>> It was approximately 18" long and 18" in diameter. The bottom was 3/8"
>> aluminum, and the top was 1" clear plastic. The chamber was successful with
>> up to an near perfect vacuum, and used many times without failure. At
>> maximum vacuum, the bottom would dish approximately 1/8 to 3/16" inch, an
>> the plastic top would dish about 1/2".
>>
>> I have a chamber I use now for another purpose, but it is only 6" in
>> diameter. The top for it is just 3/16" tempered glass.
>>
>> Hope the number might help your estimates.
>>
>> Max
>>
>>
>>
>
>You know, an ABSOLUTE vacuum is only 15 psi...
But an 18" diameter hemisphere has how many square inches? ( forgot
the formula for the surface area of a sphere) The sides of the
chamber being 18" tall and 18" in diameter would have over 2000 sq
inches X 15 or by my calculator 30,536# Add to that the area of the
half sphere that comprises the top dome and it's quite a bit of
pressure. There's a reason these things are covered with a heavy SS
mesh.

In all my years of working around that kind of equipment I've only
seen one chamber let go, but that was memorable. <:-))

Roger (K8RI)

[Fred the Red Shirt]

On Nov 2, 5:08 am, "Roger (K8RI)" > wrote:
> On Thu, 01 Nov 2007 17:38:59 -0500, cavelamb himself
>
>
>
> > wrote:
> >Maxwell wrote:
>
> >> "Mark Hickey" > wrote in message
> ...
>
> >>>Fred the Red Shirt > wrote:
>
> >>>>How big is his vacuum chamber?
>
> >>>>What sort of vacuum pump(s) does he use?
>
> >>>>One large enough for a 17.5" mirror is rather non-trivial. Assuming
> >>>>a 20" diameter cylindrical chamber, the top and bottom would need
> >>>>to support over 3000 pounds each, if the work is done at sea level.
>
> >>>Is it really that hard to build a vacuum chamber? Seems to me that
> >>>the most pressure it'll ever experience is about 15psi (1 bar), while
> >>>it's trivial to build/buy pressure containers that can handle 10-100x
> >>>that much (positive) pressure. Certainly if building a 1 bar vessel
> >>>20" in diameter is daunting, building a submarine (or worse, a
> >>>deep-sea bathyscaphe, which have reached depths of almost 36,000 feet
> >>>below sea level, resisting a pressure of about 1,100 bar) would be
> >>>unthinkable.
>
> >>>Or am I missing something?
>
> >> Maybe, maybe not. Round pressure vessels keep their shell walls in tension,
> >> hence the more pressure the better they hold their shape. Vacuum vessels are
> >> just the opposite, and quite often much easier to collapse than one might
> >> naturally assume.
>
> >> I can say I once built a round vacuum chamber out of rolled 1/4" aluminum.
> >> It was approximately 18" long and 18" in diameter. The bottom was 3/8"
> >> aluminum, and the top was 1" clear plastic. The chamber was successful with
> >> up to an near perfect vacuum, and used many times without failure. At
> >> maximum vacuum, the bottom would dish approximately 1/8 to 3/16" inch, an
> >> the plastic top would dish about 1/2".
>
> >> I have a chamber I use now for another purpose, but it is only 6" in
> >> diameter. The top for it is just 3/16" tempered glass.
>
> >> Hope the number might help your estimates.
>
> >> Max
>
> >You know, an ABSOLUTE vacuum is only 15 psi...
>
> But an 18" diameter hemisphere has how many square inches? ( forgot
> the formula for the surface area of a sphere)

To estimate the compressive force (imposed by pressure on the
top) on the cylindrical sides of the bell-jar use the cross sectional
area, not the surface area. The lateral component is carried by
the top, only the vertical component is carried to the sides.

> The sides of the
> chamber being 18" tall and 18" in diameter would have over 2000 sq
> inches X 15 or by my calculator 30,536# Add to that the area of the
> half sphere that comprises the top dome and it's quite a bit of
> pressure. There's a reason these things are covered with a heavy SS
> mesh.
>
> In all my years of working around that kind of equipment I've only
> seen one chamber let go, but that was memorable. <:-))
>

--

FF

[Fred the Red Shirt]

On Nov 2, 4:59 am, "Roger (K8RI)" > wrote:
> On Wed, 31 Oct 2007 20:32:08 -0700, Fred the Red Shirt
> ...
> He has a quartz bell jar that is (again IIRC) about 18"in diameter and
> close to 18" tall or a bit more. Ultimate vacuum is probably on the
> order of 1.2 or 1.3 X 10^-6 or -7 Torr although it doesn't need to go
> that high.
>
>

That sounds like several thousand dollars of equipment.

I think I'll look for someone else to do it for me. They usually
overcoat them too, though if I were doing my own, more frequent
recoating would be plausible.

--

FF