Grand Bois

Remember this thread?
https://www.bikeforums.net/showthread...used-pot-metal

I finally won a 1st generation Rally. It should be here in a few days. Can someone suggest a nod-destructive test for pot metal-ness?

Shaneferd

I'd suggest a vigorous ride & much enjoyment. Your previous post sent me scrambling to confirm that my Rally mech is the reinforced version. Your thumbspring will be on it's way to back to you today, thanks for that knowledge BTW.

LeicaLad 

+1 on that suggestion. I sure do like mine.

The one suggestion from the other thread was to use chrome polish. It was suggested that pot metal wouldn't react nor turn your cloth black. I seem to remember doing a bit of cleaning on mine, and having a very black cloth.

Did the one you acquired have the small reinforcement or not? Just curious.

Either way, I'm sure you'll be fine unless you're in a big smash up. In which case, the RD would not be the biggest concern.

Best regards!

Grand Bois

What's a thumbspring?

I was never concerned about breakage. I was just curious about the material used. The one that I won is one of the later versions.

rhm

I don't know what that metal is, that Campy made various things out of. They definitely used a lot of aluminum, but some parts seemed to be made of a metal that was not aluminum. Heavier and stronger. I'm pretty sure it's not pot metal. I like the idea of using a metal polish to see what comes off. Take whatever you have, whether simichrome or brasso or whatever, and polish up some pieces of various known metals, i.e. aluminum and any pot metal things you have around the house. In my experience, brasso did absolutely nothing to Campy metal. I wonder if it's a copper-nickle type alloy.

mkeller234

Just for clarification... are you talking about bare aluminum? I know polish won't have any effect on the anodized parts such as the rear derailleurs.

rhm

Well, as I said, I don't know what the stuff is. It's been 25+ years since I tried to figure it out. What I'm talking about is definitely not bare aluminum, and I don't think it's anodized aluminum. As you said, polish does nothing to anodized aluminum.

Pot metal is not a specific term. It's basically a casting involving a lot of zinc and a bit of other stuff. There are also zinc-aluminum alloys, which can include copper and who knows what.

MrEss

I thought that virtually all of Campy's non-aluminum little "bits" were made out of chromed brass. Is that not the case?

Grand Bois

Did you follow the link that I posted above? It was a discussion of a single part on a first generation Rally derailer.

dbakl

I thought if pot metal, it was plated? If so the alumium polish test won't work.

mkeller234

I think you're right. That is why there was so much interest in the broken one.

Grand Bois

Of course he's right. It wouldn't be a problem to scrape off some of the plating from the back of the part. I was hoping for a chemical that would react to one material and not to the other.

Shaneferd

[QUOTE=Grand Bois;12658711]What's a thumbspring?

QUOTE]

The retrofriction spring for the Simplex bar end you were kind enough to PIF to me. I have acquired an NOS pair & have my own spare now.

Grand Bois

You found a NOS pair of Retrofriction bar end shifters? Good for you!

rhm

What about specific gravity? Are you willing to disassemble the thing so you can check the one piece of metal? You wouldn't need very precise measurements to tell you distinguish between aluminum/alloy and zinc/alloys.

Grand Bois

There's got to be an easier way!

mkeller234

Stay at a Holiday Inn express? Easy button?

Anyone here a metallurgist?

nlerner

Time to pull out the serious equipment:

https://www.directindustry.com/prod/t...217-56697.html

Neal

Iowegian

I've heard you can separate aluminum from titanium by testing the reaction of the metal to a caustic solution (eg lye) but I'm not sure I would recommend doing that or what it would do when applied to zinc based alloys.

Chombi

If it's big enough, stick an old matchbox car (preferrably one iwth most of it's paint off already) in your mouth for a few seconds. then the rally RD........if they kinda taste the same, then it's pot metal!
That's how Fred Flintstone would do metallurgy!
You still have a 50/50 chance of getting it right anyway

Chombi

Rabid Koala

I dug mine out of the Campy parts storage bin and saw that it is the earliest version. I don't know if I want to use it or not.

unworthy1

Try a single drop of Muriatic acid (a dilute form of hydrochloric acid used as a concrete wash and etcher): if it's zinc it will foam vigorously. Use gloves and eye protection and do this outdoors or with ample ventilation...have cold water in bucket handy for quick dunk and wash off.
Aluminum may also react with Muriatic acid but will not foam as vigorously, do a test with a scrap of AL and compare...do again with a scrap of zinc (anything galvanized, even a roofing nail) and compare again.
It's not a fool-proof test but may give you something you can use.

Grand Bois

That's more like it.

One of the first jobs I ever had was cleaning rabbit cages at a laboratory with muriatic acid.