Pot metal conservation

[edisonplayer]

As we know, Edison used pot metal on his post 1908 cylinder phonographs.I remember before I bought my Triumph E from Jerry Donnell the mandrel was frozen up,and he tried to unfreeze it by slathering the bearing with grease and oil.When I had Tim Fabrizio work on the Triumph for me he put in a new bearing.edisonplayer.

[jboger]

I looked at bit more into MuggyWeld. The company supplies a SuperAlloy 1 for pot metal repairs, and a SuperAlloy 5 for aluminum repairs. I only read about SuperAlloy 1 and watched some testimonial videos.

If you were to buy this product, you would be supplied with several rods of a low-temperature allow and a flux. The alloy melts at 350 F, that is, lower than the pot metal. One cleans the work area, then applies the flux. A soldering gun can be used or a propane torch.When heat is applied to the flux, the flux turns brown. This lets you know the base metal has reached 350 F. One can then simply take one of the rods and smear the alloy onto the work area, including filling cracks and holes or re-uniting broken parts. One fellow in Australia affixed a small tab to a matchbox toy carhe repaired and claimed it made a strong bond; he was surprised how strong the bond was. Other people used the alloy to repair pot metal parts on old cars. You might need to overfill the work area then file and sand the solder down to hide the repair. The company claims the solder can be plated over but not with aluminum.

I wish I had the time to investigate this but I'm afraid I have so many other things that need my attention before I could come to this. In any case I thought I'd pass this along.

[Curt A]

The main problem is the term "pot metal" and what it actually is. Modern metal auto parts referred to as pot metal are most likely zinc die cast parts which are totally different from most 100+ yr old pot metal parts.

The old parts have a variety of low melting points metal which were thrown together in a pot to produce easily castable parts. A main ingredient in old pot metal is lead, which can be melted on a stove top. I doubt that most of the parts we deal with can be heated to 350 degrees without melting, especially with a propane torch. I have heated pot metal on a tone arm with a torch, only to turn it into a puddle of gray sludge. I was trying to heat it slightly to make a joint rotate... it disintegrated. So, pot metal is made of various metals and you might not find out what, until it's too late. Heat on pot metal phono parts is not a good idea...

[jboger]

I wouldn't rule it out as a possibility, but, yes, it would require some testing. And given the metal is of variable composition with no defined melting point, one would need to proceed carefully with each sample. I've accumulated enough projects over the years that I ca't take this on, at least not now.

[MarkELynch]

A main ingredient in old pot metal is lead, which can be melted on a stove top.

Hi Curt,

In an effort to educate the group can you please cite your source for this assertion?

Thanks!
Mark

[jboger]

Lead melts at 621 F (327 C). Muggyweld SuperAlloy 1 melts at 350 F. However, what is most pertinent is the temperature of the applied heat, from a propane torch, for example. If that's too hot, then another source of heat must be used. The MuggyWeld website claims a soldering gun can be used. If one were able to control the temperature of the heat source, that would help greatly. Nonetheless, one would need to test this material on scrap pieces of pot metal before attempting an actual repair on something of more value. And suppose one were able to apply MuggyWeld to a piece, what then would be the long-term effect of the repair?

[Curt A]

“Pot metal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/pot%20metal. Accessed 20 May. 2024.
pot metal - noun
: an alloy of copper and lead used especially for making large vessels

Wikipedia:
Pot metal (or monkey metal) is an alloy of low-melting point metals that manufacturers use to make fast, inexpensive castings. The term "pot metal" came about because of automobile factories' practice in the early 20th century of gathering up non-ferrous metal scraps from the manufacturing processes and melting them in one pot to form into cast products. Pot metal is not easily glued, soldered, or welded.

There is no metallurgical standard for pot metal. Common metals in pot metal include zinc, lead, copper, tin, magnesium, aluminum, iron, and cadmium. The primary advantage of pot metal is that it is quick and easy to cast. Because of its low melting temperature, it requires no sophisticated foundry equipment or specialized molds.

In the late nineteenth century, pot metal referred specifically to a copper alloy that was primarily alloyed with lead. Mixtures of 67% copper with 29% lead and 4% antimony and another one of 80% copper with 20% lead were common formulations.[2] ( Balfour, Edward (1885), The Cyclopædia of India and of Eastern and Southern Asia, vol. 3 (3 ed.), London: Bernard Quaritch, p. 271)

Pot metal was commonly used to manufacture gramophone parts in the late 1920s and 1930s, with notable examples being the back covers on some HMV no.4 soundboxes and HMV no.5 soundboxes.

Zinc Pest:

Zinc pest (from German Zinkpest "zinc plague"), also known as zinc rot and zamak rot, is a destructive, intercrystalline corrosion process of zinc alloys containing lead impurities. While impurities of the alloy are the primary cause of the problem, environmental conditions such as high humidity (greater than 65%) may accelerate the process.

It was first discovered to be a problem in 1923, and primarily affects die-cast zinc articles that were manufactured during the 1920s through 1950s. The New Jersey Zinc Company developed zamak alloys in 1929 using 99.99% pure zinc metal to avoid the problem, and articles made after 1960 are usually considered free of the risk of zinc pest since the use of purer materials and more controlled manufacturing conditions make zinc pest degradation unlikely.

Affected objects may show surface irregularities such as small cracks and fractures, blisters or pitting. Over time, the material slowly expands, cracking, buckling and warping in an irreversible process that makes the object exceedingly brittle and prone to fracture, and can eventually shatter the object, destroying it altogether. Due to the expansion process, attached normal material may also be damaged. The occurrence and severity of zinc pest in articles made of susceptible zinc alloys depends both on the concentration of lead impurities in the metal and on the storage conditions of the article in the ensuing decades.

Hope this clears it up...

[edisonclassm]

People can discuss the minutiae of what is happening to the existing die cast pot metal parts and speculate as to what to do with them in terms of preserving and slowing down the process of deterioration, but I feel the best solution for the generations to come is to replicate those parts in aluminum or brass which are more stable materials for the long run. I applaud Mark Lynch's efforts in the preservation of the Victor changers. I fully understand what it took to accomplish this feat as I have replicated many die cast parts for phonographs over the years as well. My method uses a decent original example of a die cast part and making a mold of that part so it can be cast using the lost wax method. The process gives you a near perfect result except for a minute shrink dimensionally. Follow up machining is needed as well. One of my bucket list accomplishments in life is to replicate the entire reproducer assembly for the US phonographs. Many of you know, almost the entire unit is made up of die castings which deteriorate in varying degrees. There are many US machines out there with broken, poorly repaired, or missing reproducer units entirely, are in need of a complete reproducer unit for their machine. Personally, I admire US machines and have a desire to accomplish this feat but unfortunately the economics don't make sense. Too complex and too costly. It would definitely be an altruistic effort if it could be done properly.