Not steel Birmabrights yet again? Will this topic never end?

Tom Gaynor

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I've posted some pix of the real blade of "the steelies" on the forum. God only knows where they are. But they are interesting: the design and execution is much better suited to the Vin RFM and chainguard than my Birmabright's blade. I had thought they might be "generic guards", bought in a hurry from Pride and Clarke or the like just to fill a gap in Birmabright supply, but they look very much "designed for purpose".

Tom
 

roy the mechanic

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accordind to K T B appendix v ii birmabright consists of a low mag-alloy. where does this make it some kind of sh-t metal? Have I missed something here except the kings clothes?
 
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Tom Gaynor

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Come again?

I recognise that Birmabright is sh-t metal, but why not just say "sheet metal"? I won't be offended. I doubt anyone else will be. Birmabright is a tradename for a particular manufacturer's version of an ally alloy sheet which contains magnesium: about 7% I think. They make Landrovers from it. That, and ferrous oxide. But the point I was making is that the steel mudguards I have, fitted by the Vincent factory to my Vincent when it left the Vincent factory, in Stevenage, referred to by me as "steel Birmabrights" because they have the same section as the ally version, are much better made than the ally Birmabright mudguards, taken from (the previous owner, a friend, told me) another Vincent twin, also made in the Vincent factory, still in Stevenage, and with which the previous owner replaced the steel ones. Both sets were fitted by the Vincent factory, to Vincents, in Stevenage. Both sets were made from sheet metal, but one set was made from sheet steel, fitted by the factory, and one set from sheet Birmabright, fitted by the previous owner. My ally Birmabrights (the ones fitted by previous owner), do NOT have a flat to clear the chainguard. They've just been bent a bit. The steel (factory fitted etc, etc) ones, do have a clear flat formed. My professional opinion is that this was done at the point of manufacture. They look, as I might have said, to have been designed for purpose, i.e. fitting to a Vincent. As, indeed they were, by the factory, in Stevenage, but we've covered that. Now that, to me, is very interesting. Maybe I need to get out more. But (not even) the machine registrar knew they even existed. He knew about steel touring guards, with valances, but not that steel "sports" guards were ever fitted. So are my ally Birmabrights, without such a flat, not Vincent at all? An aftermarket bodge? Intended for some lesser breed, but, unaccountably, with exactly the right dimensions, and with exactly the right holes for Vin hinges and Vin stays? Am I alone in having Birmabrights (because that is unmistakeably what they are made from) with no clear flat formed to clear the chainguard? Everyone else has one, but I'm Billy No-Mates, and missed the cut? Or do all Birmabrights have a clearly defined flat, like the one on my pictures? (In the Gallery, somewhere.) I'd like to know. I hope that answers your question. Tom
accordind to K T B appendix v ii birmabright consists of a low mag-alloy. where does this make it some kind of sh-t metal? Have I missed something here except the kings clothes?
 
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clevtrev

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BB2, Birmetals Ltd. was their spec code for the same material, if purchased from another company, e.g. British Aluminium Co Ltd = BA21
Alcoa of Great Britain = Alcoa 510
HDA Foprgings Ltd., = Hiduminium 33
Alcan Aluminium Ltd., = B53S
and other companies supplying what today we know as 5251. or NS4. The N designates Non heat treatable.
With a make up of :- 0.40 % Silicon. 0.50 Iron. 0.15 Copper. 0.1-0.50 Manganese. 1.7 - 2.40 Magnesium. 0.15 Chromium. 0.15 Zinc. 0.15 Titanium. 0.50 Others not specified ( but probably floor sweepings :) ) Balance Aluminium.

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