Minnie Gunmetal Bronze and Brass

I am restarting my Minnie Build, after a break of several decades. In preparation For this restart I have been cruising the vatious build threads in these forums and I see a sense of the same confusion I feel, about the choice of non- ferrous materials for components in both the bearings and boiler fittings areas.

It's not so much what the differences between brass, bronzes, and the particular bronze known as gunmetal are, (browsing around I have found quite a bit of information on that topic) but I find a strange thing when I am trying to get my materials together: I have found almost no sources of non-ferrous materials in hex sizes other than brass. This makes it hard to follow the advice scatterred around about how preferable GM and bronze are, from points of view of hardening, dezincifcation, wear, and interraction with water.

OK so I should be buying bronzes, but why cant I find any?

Do others find this also, or am I looking in the wrong places?

Michael, down under

For the small amount of hex parts that are likely to need to be bronze it's easier to mill from round than have 11 of the 12" sitting around afterwards waiting to be used. As most of the fittings don't come into contact with the boiling water there is little chance of dezincification, cylinder fixings and water gauge being the main two that are best done in bronze.

M-machine have a reasonable range of various bronzes in hex. EKP also do the most likely sizes needed on Minnie

Edited By JasonB on 25/01/2021 08:05:48

GLR Kennions stock bronze hexagon in lengths down to 6"

M-Machine dont post outside UK. but I will check out EKP

GLR have only 1/4, 5/16, 7/16 and some weird size in between. Not a world of choice but useful as far as it goes. Was hoping for 3/16 and 3/8 also.

Thanks for the pointers gents.

Michael, unless things have changed recently, M-Machine shipped a lump of steel to me in France beginning of May2020.
Regards
DaveD

Macc models have a good range of bronze and brass in smaller AF sizes and available in 6" lengths

Dougie

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Thanks br (stands for?). thats right gentlemanly of you. Let me a) finalise my list of pieces first b) check Macc models out and c) get back to you if necessary to take you up on that. In the meantime you might want to email me off-forum with contact details.

Edited By JasonB on 26/01/2021 19:35:20

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OOPS. WELL I guess that cat is out of the bag. But anyway, I see I wasnt clear, or to Dougie apparently; the 3/16 and 3/8 quoted were rounds, not quuite as hard to obtain

Macc (unless I am not searching properly, quite possible) doesnt show any hex smaller than 1/4AF in PB102

Which supplier is Joe, by the way?

Michael

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Now I am lost again. How does that help me get 3/16 hex?

And am I wrong thinking fittings are unions, tees, valves, and similar?

There will be a pause in my thinking while I make a list of actual requirements, huided mainly by Len Mason's book on Minnie, since I dont really know enough to stray from his recommendations.

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OK I have read what stuff I can get my hands on, and cant see why you would say PB102 is not for fittings. Am I right in thinking fittings includes things like valves an water gauges, bypass valves, etc etc? In the Minnie book these are all marked as GM or Bronze.And PB102 is bronze, isnt it?

so why is PB102 only for bushings?

Colour me thoroughly confused at this stage, quite apart from the availability issues.

Michael

As I said in my first reply anything that is likely to come into contact with the boileng water runs the risk of dezincification so as brass contains zinc you avoid it in those areas.

Therefor boiler bushes are done with bronze or GM. Only certain "boiler fittings" would need it such as blow down valves and water gauges as they both come into contact with the boiling water. studs or screws holding cylinder and weigh shaft bracket will get a certain amount of hot water contact so they too are best done in bronze.

Bypass valve, blower valve safety valve etc only see cold water or steam so won't be affected by dezincification so are OK in brass.

The only thing it would be benificial to have hex bronze stock for is the cylinder fixings if you areopting for bolts due to the amount needed, alternatively just thread up some round stock to make bronze studs and buy or make brass nuts. There is not a lot of hex in the other parts so just use round stock and mill the hex as required.

You can use GM for bushes but its not as easy to get hold of round bar as in model engineering it tends to be used more for castings. PB 102 is also a little bit harder so more durable if things are being screwed in and out. There is nothing to stop you using PB102, SA660 etc bronzes for any of the steam or boiler fitings if you can get hold of the stock or machine to suit.

Edited By JasonB on 28/01/2021 12:30:46

Thanks, Jason I can follow that chain of thought. Except that Im reasonably sure any hex I mill from round will look more like a dog's breakfast, so I will try and get some hex

Having meanwhile listed what I need in bronze I find that it is only a few inches of sizes other than 3/16, which since it is used for the cylinder hold-down bolts, comes to nearly 2 12" lengths.

1/4, 5/16 and 3/8 all come to well within 6" lengths.

Michael

Hi Michael,

You could also check out Blackgates.co.uk. You can download their catalogue (2019 latest?).

Much of what you're after is listed (and much more), but obviously need to check stock availability. They should ship internationally.

I've been using them for 35 years and happy with them. Page 109 is the phosphor bronze bar stock etc.

Hope this helps.

Regards