Another old piece of kit this week. Steel case with a bakelite closure that
was a devil to separate. Metal not rusted and I'm assuming steel does not
shrink over decades.

On Apr 11, 7:10*am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure that
was a devil to separate. Metal not rusted and I'm assuming steel does not
shrink over decades.

I have found that many of the pot metal castings used for metal parts
on old radios, turntables, etc. have expanded over time.

I was astonished to learn that metal can do that in a timescale
measured in decades.

I'm sure that bakelite and other plastics can change dimension over
time too. Those I have a much easier time understanding, since the
evaporation (sublimation?) rate of the organic chemicals is always
something that I've associated with a timescale of years or decades,
and I know from my experience living in southern california that
exposure to ozone and intense sunlight can accelerate the process
incredibly.

My gut feeling is that just like different pot metal mixes exhibit the
expansion at different rates probably based on whatever they had to
throw in the pot that day, that plastics can vary based on detail of
manufacture too.

Tim.

Tim Shoppa wrote in message
...
On Apr 11, 7:10 am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure
that
was a devil to separate. Metal not rusted and I'm assuming steel does not
shrink over decades.

I have found that many of the pot metal castings used for metal parts
on old radios, turntables, etc. have expanded over time.

I was astonished to learn that metal can do that in a timescale
measured in decades.

I'm sure that bakelite and other plastics can change dimension over
time too. Those I have a much easier time understanding, since the
evaporation (sublimation?) rate of the organic chemicals is always
something that I've associated with a timescale of years or decades,
and I know from my experience living in southern california that
exposure to ozone and intense sunlight can accelerate the process
incredibly.

My gut feeling is that just like different pot metal mixes exhibit the
expansion at different rates probably based on whatever they had to
throw in the pot that day, that plastics can vary based on detail of
manufacture too.

Tim.

+++++

The one this week was where the bakelite closure, top panel, was recessed
into the steel back body, so either metal had shrunk or the bakelite had
expanded over 70 years

Bakelite typically uses wood flour as a filler, which is hygroscopic
and could swell with age.

Catalin shrinks, as the entrained water evaporates.

Alan

On 4/11/09 10:33 AM, in article ,
"Alan Douglas" adouglasatgis.net wrote:

Bakelite typically uses wood flour as a filler, which is hygroscopic
and could swell with age.

Catalin shrinks, as the entrained water evaporates.

As many of us have experienced through situations like screw holes that are
no longer aligned with the chassis, and back covers that somehow have become
larger than the opening they are covering.

On Apr 11, 10:10*am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure that
was a devil to separate. Metal not rusted and I'm assuming steel does not
shrink over decades.

Catalin shrinks as Alan suggests - for two reasons. First, the water
entrained when froming the piece dissipates - this happens pretty
quickly. Then additional water and formaldehyde starts to outgas, this
is a gradual process taht depends on climate and temperature, but is
continuous to a greater or lesser degree until ultimately the material
will crumble altogether.

Bakelite uses a much different process although it is essentially the
same material as catalin (thermosetting phenolic resin) but it is
twice-formed and uses some sort of aggregate including colorants, wood
flour (again as Alan suggests), carbon-black, glass powder and fibers
and any of many other sorts of things. *Depending on the aggregate* it
is very dimensionally stable over time and under most conditions,
hence its favor for electrical parts exposed to harsh conditions, and
so forth.

White metal will expand, crumble or crack over time depending on its
composition and environment. Most other pure metals or alloys are
diminsionally stable excepting expansion and contraction for due to
temperature - although some alloys of steel will expand under certain
kinds of radiation - which if they exist in your home to that extent,
you are dead already. Some types of glass will turn purple with age,
some say due to ultra-violet, some say due to cosmic rays as it will
turn purple whether inside or out. Pick whichever you choose.

Peter Wieck
Melrose Park, PA

wrote in message
...
On Apr 11, 10:10 am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure
that
was a devil to separate. Metal not rusted and I'm assuming steel does not
shrink over decades.

Catalin shrinks as Alan suggests - for two reasons. First, the water
entrained when froming the piece dissipates - this happens pretty
quickly. Then additional water and formaldehyde starts to outgas, this
is a gradual process taht depends on climate and temperature, but is
continuous to a greater or lesser degree until ultimately the material
will crumble altogether.

Bakelite uses a much different process although it is essentially the
same material as catalin (thermosetting phenolic resin) but it is
twice-formed and uses some sort of aggregate including colorants, wood
flour (again as Alan suggests), carbon-black, glass powder and fibers
and any of many other sorts of things. *Depending on the aggregate* it
is very dimensionally stable over time and under most conditions,
hence its favor for electrical parts exposed to harsh conditions, and
so forth.

White metal will expand, crumble or crack over time depending on its
composition and environment. Most other pure metals or alloys are
diminsionally stable excepting expansion and contraction for due to
temperature - although some alloys of steel will expand under certain
kinds of radiation - which if they exist in your home to that extent,
you are dead already. Some types of glass will turn purple with age,
some say due to ultra-violet, some say due to cosmic rays as it will
turn purple whether inside or out. Pick whichever you choose.

Peter Wieck
Melrose Park, PA

++++

So wood pulp filler could lead to expansion but if a mineral was used ,as a
filler, then dimensionally stable bakelite would result ?

wrote in message
...
On Apr 11, 10:10 am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure
that
was a devil to separate. Metal not rusted and I'm assuming steel does not
shrink over decades.

Catalin shrinks as Alan suggests - for two reasons. First, the water
entrained when froming the piece dissipates - this happens pretty
quickly. Then additional water and formaldehyde starts to outgas, this
is a gradual process taht depends on climate and temperature, but is
continuous to a greater or lesser degree until ultimately the material
will crumble altogether.

Bakelite uses a much different process although it is essentially the
same material as catalin (thermosetting phenolic resin) but it is
twice-formed and uses some sort of aggregate including colorants, wood
flour (again as Alan suggests), carbon-black, glass powder and fibers
and any of many other sorts of things. *Depending on the aggregate* it
is very dimensionally stable over time and under most conditions,
hence its favor for electrical parts exposed to harsh conditions, and
so forth.

White metal will expand, crumble or crack over time depending on its
composition and environment. Most other pure metals or alloys are
diminsionally stable excepting expansion and contraction for due to
temperature - although some alloys of steel will expand under certain
kinds of radiation - which if they exist in your home to that extent,
you are dead already. Some types of glass will turn purple with age,
some say due to ultra-violet, some say due to cosmic rays as it will
turn purple whether inside or out. Pick whichever you choose.

Peter Wieck
Melrose Park, PA

At the risk of sounding gross, what is the type of plastic that smells
like......vomit?

Paul P

Paul P wrote in message
...

wrote in message
...
On Apr 11, 10:10 am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure
that
was a devil to separate. Metal not rusted and I'm assuming steel does
not
shrink over decades.

Catalin shrinks as Alan suggests - for two reasons. First, the water
entrained when froming the piece dissipates - this happens pretty
quickly. Then additional water and formaldehyde starts to outgas, this
is a gradual process taht depends on climate and temperature, but is
continuous to a greater or lesser degree until ultimately the material
will crumble altogether.

Bakelite uses a much different process although it is essentially the
same material as catalin (thermosetting phenolic resin) but it is
twice-formed and uses some sort of aggregate including colorants, wood
flour (again as Alan suggests), carbon-black, glass powder and fibers
and any of many other sorts of things. *Depending on the aggregate* it
is very dimensionally stable over time and under most conditions,
hence its favor for electrical parts exposed to harsh conditions, and
so forth.

White metal will expand, crumble or crack over time depending on its
composition and environment. Most other pure metals or alloys are
diminsionally stable excepting expansion and contraction for due to
temperature - although some alloys of steel will expand under certain
kinds of radiation - which if they exist in your home to that extent,
you are dead already. Some types of glass will turn purple with age,
some say due to ultra-violet, some say due to cosmic rays as it will
turn purple whether inside or out. Pick whichever you choose.

Peter Wieck
Melrose Park, PA

At the risk of sounding gross, what is the type of plastic that smells
like......vomit?

Paul P




And while at it , what glue, or whatever, breaks down over decades to give
the small of rotted horse manure, not fresh, maybe referred to as a
"caproic" (goaty) smell . You open up some kit and there is that small that
can saturate the workroom for hours before it dissipates.

On Apr 11, 1:35*pm, "N_Cook" wrote:

So wood pulp filler could lead to expansion but if a mineral was used ,as a
filler, *then dimensionally stable bakelite would result ?

Not pulp - well, OK... derived from pulp but not the same. The wood
flour that is used is very nearly pure lignin - that part of wood that
lends strength and is also hydrophobic - so that big oak tree out
there does not dissolve in the rain.

So, to the extent that the wood flour used is contaminated with other
wood components, it might expand when exposed to moisture. But the
material is heated (twice) and formed under great pressure. Most of
the water created by the initial chemical reaction is dissipated in
first heating, the last done under great pressure and greater heat
completes the thermosetting process - but most of the water is already
long-gone. And any non-lignin components remaining were mostly burnt
off in the first go as well.

The smelly plastic is Cellulose Acetate - which goes to vinegar and a
few other smellies. And there are several other materials that use
Cellulose Acetate in their formulations to a greater or lesser extent
- which decay similarly with similar smells.

Peter Wieck
Melrose Park, PA

Tim Shoppa wrote:
On Apr 11, 7:10 am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure that
was a devil to separate. Metal not rusted and I'm assuming steel does not
shrink over decades.

I have found that many of the pot metal castings used for metal parts
on old radios, turntables, etc. have expanded over time.

I was astonished to learn that metal can do that in a timescale
measured in decades.

Oh, yeah. I've got an old Philips bakelite radio that has one of those
schemes where the tuning and volume are on the same shaft. The metal
used in the construction of this gizmo has expanded enough that the
tuning only moves as far as the volume control, and turning either one
makes both of them move. I can't even extract the chassis to try to fix
this because the knob is literally fused to the shaft from the
expansion. I haven't figured out how I'm going to deal with that yet, so
the set is a shelf queen.

-Scott

Scott W. Harvey wrote in message
...
Tim Shoppa wrote:
On Apr 11, 7:10 am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a bakelite closure
that
was a devil to separate. Metal not rusted and I'm assuming steel does
not
shrink over decades.

I have found that many of the pot metal castings used for metal parts
on old radios, turntables, etc. have expanded over time.

I was astonished to learn that metal can do that in a timescale
measured in decades.

Oh, yeah. I've got an old Philips bakelite radio that has one of those
schemes where the tuning and volume are on the same shaft. The metal
used in the construction of this gizmo has expanded enough that the
tuning only moves as far as the volume control, and turning either one
makes both of them move. I can't even extract the chassis to try to fix
this because the knob is literally fused to the shaft from the
expansion. I haven't figured out how I'm going to deal with that yet, so
the set is a shelf queen.

-Scott


Faced with a similar situation some years ago and wanting to save the knob
and so knobs.
I found a piece of steel or Al round bar, drilled through axially on a
lathe, 1/8 inch hole. Mounted co-axially over the knob held there with
Jubilee / hose clip and some padding.
Then 1/8 inch drilled into the knob and into the shaft. Saved the bakelite
dust to mix with epoxy to make good afterwards. Luckily the 1/8 inch
drilling was enough to loosen the knob and filled the shaft with epoxy as
well, in the end. Otherwise it would have been a matter of drilling larger
holes until freed

And while at it , what glue, or whatever, breaks down over decades to give
the small of rotted horse manure, not fresh, maybe referred to as a
"caproic" (goaty) smell . You open up some kit and there is that small
that
can saturate the workroom for hours before it dissipates.




I asked an industrial chemist about this and he suggested it was Caproic or
Hexanoic Acid and I would suggest it was from use of rendered down horse
bones for horse glue in plywood making or cabinet joining before PVA glues
came in.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

At the risk of sounding gross, what is the type of plastic that smells
like......vomit?

Cellulose acetate butyrate, which breaks down releasing butyric
acid (which incidentally hastens the breakdown of the remaining
plastic, so sealing the item in an airtight enclosure is a bad idea).

Alan

wrote in message
...
On Apr 11, 1:35 pm, "N_Cook" wrote:

So wood pulp filler could lead to expansion but if a
mineral was used ,as a
filler, then dimensionally stable bakelite would result ?

Not pulp - well, OK... derived from pulp but not the same.
The wood
flour that is used is very nearly pure lignin - that part of
wood that
lends strength and is also hydrophobic - so that big oak
tree out
there does not dissolve in the rain.

So, to the extent that the wood flour used is contaminated
with other
wood components, it might expand when exposed to moisture.
But the
material is heated (twice) and formed under great pressure.
Most of
the water created by the initial chemical reaction is
dissipated in
first heating, the last done under great pressure and
greater heat
completes the thermosetting process - but most of the water
is already
long-gone. And any non-lignin components remaining were
mostly burnt
off in the first go as well.

The smelly plastic is Cellulose Acetate - which goes to
vinegar and a
few other smellies. And there are several other materials
that use
Cellulose Acetate in their formulations to a greater or
lesser extent
- which decay similarly with similar smells.

Peter Wieck
Melrose Park, PA

Celluloid is either cellulose acetate or cellulose
nitrate, both were used as photographic film base and
neither is stable. The acetate smells of vinegar when its
decomposing and nitrate often smells of camphor although
other substances were used as plasticizers. Both shrink,
distort, and disintegrate with age. Acetate does not support
flame while the nitrate is nearly impossible to extinguish
once ignited since it supplies its own oxygen. The latter is
the main reason cellulose nitrate was discontinued for film
base in 1951. Probably most plastic dial windows on old
radios are cellulose acetate.


--

--
Richard Knoppow
Los Angeles
WB6KBL

Dear N_Cook:

On Apr 11, 7:10*am, "N_Cook" wrote:
Another old piece of kit this week. Steel case with a
bakelite closure that was a devil to separate. Metal
not rusted and I'm assuming steel does not shrink
over decades.

Plastics can absorb moisture (the universal solvent) over time.
Additionally, steel does in fact shrink with a shrinkage rate of about
1 part in 10^8 per year. Invar expands with about the same magnitude,
which is why such alloy rods were abandoned as length standards in the
1960s.

http://nvl.nist.gov/pub/nistpubs/jre...tml/j43bee.htm
.... what a job... measuring the same rod four times a year for
decades.

David A. Smith

I did!

Bryce wrote in news:gs0kr3$nku$2
@news.motzarella.org:

I did!

You did what?
Do you imagine that others see the same thread and posting preceding yours?

You posted on Usenet. People read Usenet using various methods. Some use
Google, some use various Usenet readers, some use other methods. FYI,
Usenet postings propagate at different speeds and some postings never
propagate along some paths. Other readers may never see the text to which
you are responding. Others may see your comment before they see the
material to which you responded.

You should ALWAYS properly 'quote' the material [proper means to give the
source AND format the quoted material so that it can not be mistaken for
your comments] and add your comments, removing extraneous [not related to
your comment] original material.




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On Apr 14, 3:20*pm, bz wrote:
Bryce wrote in news:gs0kr3$nku$2
@news.motzarella.org:

I did!

You did what? *

Oh, MY!!

He did - expand with age.

Peter Wieck
Melrose Park, PA

wrote:

On Apr 14, 3:20 pm, bz wrote:
Bryce wrote in news:gs0kr3$nku$2
@news.motzarella.org:

I did!

You did what?

Oh, MY!!

He did - expand with age.

Peter Wieck
Melrose Park, PA

Yes, I expanded. Alas, in so doing I became (more) ignorant
and neglected proper newsgroup etiquette. Sorry.