Re: Pot metal - was something else

On 8/9/26 09:06, Carlos E.R. wrote:
> On 2026-08-09 14:20, The Natural Philosopher wrote:
>> On 09/08/2026 01:47, c186282 wrote:
>>>   The alloy does not seem very resistant to vibration.
>>>    It's soft enough you'd THINK it would be, but its not.
>>>
>> The problem is mainly that its has no fixed composition, Its random 
>> non ferrous scarp mainly. Use a magnet to get the iron and steel and 
>> melt what is left over perhaps
>>
>>
>>>    Most aluminum alloys and 300 series stainless are
>>>    not super-good with vibrations either - though
>>>    better than 'pot metal'. I've seen 'magnesium' tire
>>>    rims crack too.
>>>
>> Pot metal is heavy and brittle in my experience.
>>
>> Came across it back in the day in toys, carburettor castings, 
>> thermostat housings..valve covers..all stuff that needed shape 
>> retention but no great strength
>>
>>>    Only steel - esp nearly pure iron - seems to stand
>>>    up to vibration, but it's HEAVY. Some cast iron,
>>>    like that previously used for engine blocks, can
>>>    be pretty good but will fracture on a sharp impact.
>>>    I've seen old cracked engine blocks too.
>>>
>> Cast iron is brittle.That's why they used to use wrought iron - but it 
>> was expensive.
>> Then making steel got super cheap and that was that. Whole generation 
>> learned to treat and alloy steel to get almost whatever you want
>>
>>>    Plastics - they start 'crystalizing'/decomposing
>>>    the instant they're made.
>>
>> Not all of them. Like steel, there is a huge range. There's many a 
>> radio case made of 'Bakelite' or stuff skinned with 'Formica'  or 
>> floored with 'linoleum'....still functioning
>>
>> Epoxy and glass fibre PCBs dating from the 1970s are still OK, as are 
>> phenolic resin items
>>
>> PVC however is very short lived, In the sun
> 
> PVC is used here for window frames and blinds. I had a place with such, 
> 40 year old, and good. Yellowish, though. And more brittle.

   Either becomes more brittle - or decomposes into goo,
   depending on the exact formula. UV-blocking additives
   help but they're not "forever".

   Bakelite ... holds up for quite awhile, esp indoors,
   but still does become more brittle. If you come across
   old Bakelite table radios from the 30s and 40s it's
   very common to see cracks and chips missing.

>> Nylon is intermediate - UV ageing often gets it
>>
>> Jury is still out on polycarbonate, ABS  and ASA.

   Polycarbonate dies under UV exposure. Clear becomes
   cloudy and then brittleness sets in. On the plus it's
   fairly cheap.

>> In fact one of the eco gripes about plastics is that they *don't* 
>> degrade.
> 
> They fragment into microplastics.

   Oh no - DOOM !!!

   IMHO most of that is something LAWYERS fabricated
   so they can sue corps for diseases everyone has
   always gotten anyway.


>> Nevertheless there are plastic gobbling bugs thriving at the bottom of 
>> the sea apparently, eating all those microplastics.
>>
>> Beware the SweepingStatement...

   Many of the plastics we now use were invented way
   back in the 50s - which means both that 'exposure'
   has been VERY long and the performance is well known.

   One of my big concerns is how 'construction' plastics
   like epoxy resins are used. Remember the big tunnel
   in Boston where they hung a ridiculously heavy concrete
   panel roof from epoxy-mounted bolts ?

   (what mob-connected bunch specced a 4-inch concrete
   ceiling for a tunnel already made of concrete ?)