Spontaneous Spoke Combustion

On 12/16/2015 6:45 PM, Clive George wrote:
On 17/12/2015 00:13, John B. wrote:

One thing is that "stainless steel" is not necessarily
corrosion
proof. See http://www.estainlesssteel.com/corrosion.shtml or
http://www.bssa.org.uk/topics.php?article=95
for a discussion of how stainless works.

The other day I was reading the book "Ignition", which is
the story of liquid propellants in rockets. (can be found on
the web, it's not too long).

One of the propellants he describes is red fuming nitric
acid, ie close to 100% HNO3. They put it in steel
containers, thought it was ok, but a while later discovered
the hard way that it did attack them and the resulting
sludge is very nasty indeed.

The fix turned out to be add 5% of an even more nasty thing
- HF. The hydroflouric acid reacts with the steel to form a
flouride layer which is actually resistant to both acids,
and the entire thing is stable.


Thanks for that, very cool.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

yeah, my 544 was parked outside at https://goo.gl/EqUZGq

inside the 544 was a steel toolbox with '70's Craftsmen sockets

sockets showed rust spots....

cleaned Craftsmans then oiler with thinned linseed, resolving the dew point salt deposits.

and on the Volvo

On 12/17/2015 7:54 AM, wrote:
yeah, my 544 was parked outside at https://goo.gl/EqUZGq

inside the 544 was a steel toolbox with '70's Craftsmen sockets

sockets showed rust spots....

cleaned Craftsmans then oiler with thinned linseed, resolving the dew point salt deposits.

and on the Volvo


Right. Metals just sit around all day scheming to find a
lower energy state:

http://www.yellowjersey.org/photosfr...t/DAMPCRNK.JPG

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

1 April, 1971

aluminum oxide forms immediately on lost aluminum alloys but not solder able aluminum alloy is type 1 ?

if a slim sliver of crank alloy is sliced off, is this solderable ?

or braze able ?

that is a mess. how polish out ?

On 12/17/2015 5:30 PM, wrote:
1 April, 1971

aluminum oxide forms immediately on lost aluminum alloys but not solder able aluminum alloy is type 1 ?

if a slim sliver of crank alloy is sliced off, is this solderable ?

or braze able ?

that is a mess. how polish out ?


We often note when asked to work with corroded parts that we
can't 'make it go away'. The rust or aluminum oxide is where
you once had metal, which is gone.

An oxidized pitted crank may be smoothed with successively
finer grades of wet sandpaper and finished on a cotton
polishing wheel if time and money are not critical. That
won't help any deep pits or unseen cracks/voids some of
which may be compromised by water and/or salt penetration.
Most aluminum cranks are anodized, and so need to be
completely polished on all surfaces to get a uniform look,
which is quite tedious considering they are no longer very
expensive. Then too, a polished crank is less corrosion
resistant than an anodized crank...

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Thu, 17 Dec 2015 00:45:08 +0000, Clive George
wrote:

On 17/12/2015 00:13, John B. wrote:

One thing is that "stainless steel" is not necessarily corrosion
proof. See http://www.estainlesssteel.com/corrosion.shtml or
http://www.bssa.org.uk/topics.php?article=95
for a discussion of how stainless works.

The other day I was reading the book "Ignition", which is the story of
liquid propellants in rockets. (can be found on the web, it's not too long).

One of the propellants he describes is red fuming nitric acid, ie close
to 100% HNO3. They put it in steel containers, thought it was ok, but a
while later discovered the hard way that it did attack them and the
resulting sludge is very nasty indeed.

The fix turned out to be add 5% of an even more nasty thing - HF. The
hydroflouric acid reacts with the steel to form a flouride layer which
is actually resistant to both acids, and the entire thing is stable.

I was stationed at Edwards AFB which is the Air Forces's
"experimental" base. The "experimental" (think precision) machine shop
had made metal to metal flanges which were used by the Rocket Test
Center with nitric acid oxidizers. Apparently with the pressures
involved conventional seals were less then reliable :-)
--
cheers,

John B.

1 April, 1971

yes, advice well taken


https://www.google.com/#tbm=shop&q=m...69337098308413

On Wed, 16 Dec 2015 08:20:26 -0800 (PST), KyleBH
wrote:

Seems like a bad batch of spokes to me.
Anyone ever seen this before?

I would agree, for an odd reason. I had some DT stainless spokes rip
the holes out of a Shimano rear hub due to expansion and contraction
of the stainless with temperature. If your spokes broke from
excessive tension or temperature cycling, I would expect the hub to
fail in a similar manner, not the spokes. That leaves corrosion, as
you speculate.

Also, you might try tension testing the surviving spokes for a similar
breakage problem with a tension tester made from a screw jack and load
cell. Something like this:
https://picasaweb.google.com/113835795328994675005/SpokeTensionMeterCalibrationJig
http://www.bikeforums.net/bicycle-mechanics/699746-spoke-tension-meter-calibration-fixture.html
http://www.ebay.com/sch/i.html?_nkw=tension+load+cell

Figure about 250 lbs breaking strength:
http://www.santarosa.edu/~yataiiya/E45/PROJECTS/Metallurgy%20of%20Bicycle%20Spoke.pdf

A photo of the broken end would help assign the blame.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Thu, 17 Dec 2015 17:42:45 -0600, AMuzi wrote:

We often note when asked to work with corroded parts that we
can't 'make it go away'. The rust or aluminum oxide is where
you once had metal, which is gone.

An oxidized pitted crank may be smoothed with successively
finer grades of wet sandpaper and finished on a cotton
polishing wheel if time and money are not critical. That
won't help any deep pits or unseen cracks/voids some of
which may be compromised by water and/or salt penetration.
Most aluminum cranks are anodized, and so need to be
completely polished on all surfaces to get a uniform look,
which is quite tedious considering they are no longer very
expensive. Then too, a polished crank is less corrosion
resistant than an anodized crank...

Well, you can always fill the cracks, crevasses, holes, pits, and
gouges with stainless steel epoxy putty.
http://www.winnerindustrialsupply.com/index.php?view=product_detail&product_id=367
http://www.amazon.com/Loctite-97443-Fixmaster-Stainless-Minutes/dp/B001HWFHXU
It won't make the spoke any stronger, but it will look good... until
it breaks.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Thu, 17 Dec 2015 07:13:58 +0700, John B.
wrote:

One thing is that "stainless steel" is not necessarily corrosion
proof. See http://www.estainlesssteel.com/corrosion.shtml or
http://www.bssa.org.uk/topics.php?article=95
for a discussion of how stainless works.

Some stainless concoctions are not even galvanically compatible with
themselves. I suggest you add the comments by Dr. Barry L. Ornitz to
your collection:
http://www.yarchive.com/electr/galvanic_corrosion.html
In fact, stainless steel can be both anodic and cathodic
to ITSELF. This means that a single piece of stainless
can act as a galvanic battery and promote its own corrosion.
I've seen it happen in some marine antennas, but can't recall which
stainless was involved.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558