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R26 Black Phosphate Plating

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VintageJim
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R26 Black Phosphate Plating

Post by VintageJim »

In the Barrington manual it has an extensive list of fasteners that were black phosphate finished, but doesn't mention any of the other parts on the bike. Does anyone know the original finish of parts like the threaded studs attaching the transmission to the engine, holding the trans cover, and the rear drive studs had when new? Also the brake levers and rear brake rod?
Any knowledge would be greatly appreciated!
Jim

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caker
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Re: R26 Black Phosphate Plating

Post by caker »

Hi,

My esoteric knowledge (?) around this is mostly for pre(and post)-war plunger bikes, but for those bikes plating was: CAD, black phosphate, and "industrial chrome" (on axles), I think??

It was explained to me: if it's against aluminum it was CAD, if it was against black paint it was black phosphate. So, things like transmission studs in the motor for the transmission along with washers and nuts would be CAD. Fender hardware would be black. There are exceptions, of course...

Another way to feed this dilemma is to look at the photos from the archives - and try to discern away photos of promotional / prototype bikes that will lead you astray, from the production bikes which should be followed.

- https://bmw-grouparchiv.de/research/sea ... sult.xhtml (far upper right corner you can switch to ENglish).

Also, often the parts book indicates the plating in the description of the fastener.

Hope that helps,
-Chris

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caker
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Re: R26 Black Phosphate Plating

Post by caker »

> Also, often the parts book indicates the plating in the description of the fastener.

temp-r26.png

Stud bolt for gearbox attachment
M 8x30-5 S cad. (E)

-Chris

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Re: R26 Black Phosphate Plating

Post by jwonder »

Jim,

For the R 26 go to the parts manual in our library and you can see the finish listed for the various components.

Go to https://vintagebmw.org/library_data/Par ... 5-3R26.pdf

And for an example look at page 20 (page 27 of the PDF) at number 61 which is the clamp bolt, and that is the clamp bolt for the bar mount, it is M8 x 30mm and is in cad.

Not everything is displayed in the pictures, such as, if you are looking for the proper finish on the oil pan bolts and they are NOT shown in the picture, you will find them on page 7 (page 8 of the PDF) number 99 13 455 (listed as oil pan bolts) and they are CAD. Almost every bolt, nut and washer is listed in the manual and most have finishes.

Chris is also right, BMW followed the simple rule of bright-on-bright and dark-on-dark for almost everything, except the acorn nuts on the top of the /2 motor mounts and a few other oddities. So if the finish is NOT listed (such as the nut for the valve cover spanner) which is on page 9 (page 10 in the PDF) labeled #50, it is cad because it is mounted on a bright part.

The finishes are as follows:

CAD - That's easy, CAD plated. :D
Verchromt - Chrome
atr. - Atramentized or phosphated and blackened (both are black)
Phos. - Phosphated and blackened (you see this in some parts manuals)
Matt Verchromt - Chrome that is not polished. The /2 axle nuts are matt chrome.
I forget what Nickel plating is called out as, but I have seen it.

I hope that helps!!!
James Wonder
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York

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Re: R26 Black Phosphate Plating

Post by caker »

Nice reply - thanks James.

Can we go further?

Manganese phosphate, right?

Do "atr." and "Phos." mean the same - they just changed the lexicon?

-Chris

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Re: R26 Black Phosphate Plating

Post by jwonder »

Get two "bolt geeks" together and see what transpires.
caker wrote:
Fri Feb 03, 2023 7:40 pm
Manganese phosphate, right?
I am not sure if they used Manganese phosphate on items, its more for wear resistance than simply anti-corrosion if I understand it correctly (correct me please if I am wrong). I believe that for bolts and nuts, they were after anti-corrosion properties and that zinc phosphate (which is a dark grey) + blackening is what they did.
caker wrote:
Fri Feb 03, 2023 7:40 pm
Do "atr." and "Phos." mean the same - they just changed the lexicon?
They may be, but I am not sure. CarSpector states Atramentizing - A corrosion protection process in which steel is coated with phosphate using a zinc phosphate solution at 90° C (194° F). So, that would seem to mean they are the same, but we know the Internet can be wrong. :lol:

In the R 68 parts manual page 4 (page 5 of the PDF) they explain the parts numbering scheme they used at the time and they list 1 = CAD, 2 = atramentized or phosphated and blackened, 3 = Chrome, 4 = Black Enamel, 5 = Colored Enamel, 6 = Special treatment (whatever that means) and 7 = polished.

BMW mentioned them together for finish in the above R 68 parts manual, but seemed to outline them as two separate processes. Hmmmmmmm. Interesting......

Looking at the older pre-war and plunger manuals I only see Atr (on a quick look) and I start seeing multiple version of phosphate (pho.ge., phr.sw) and I know I have seen other abbreviations for Phosphate in newer manuals, I just cant find them now. See the 1961 parts manual pdf page 17 #45 for the black pan bolts; 1963 parts manual pdf page 19 #45 for the same bolts with a different abbreviation.

It looks like at some time they stopped the Atramentizing (sp?) process and moved to Phosphate, but I do not know that for sure. The parts book would suggest that but they could be exactly the same and simply be a nomenclature change. Not sure....

It is likely safe to say that Atr and derivatives of Pho being black in color, but not painted.
James Wonder
Vice President, Vintage BMW Motorcycle Owners
2022 BMW Friend Of the Marque
Long Island, New York

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Re: R26 Black Phosphate Plating

Post by VintageJim »

Wow, thanks for the information!

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Re: R26 Black Phosphate Plating

Post by caker »

Another great reply, James - thanks.

The remaining question: what was the "blackening" process, if it was zinc phosphate + blackening?

-Chris

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Re: R26 Black Phosphate Plating

Post by VintageJim »

After some research it looks like this process is called Parkerizing in the gun world and was use in WWI an WWII to help stop corrosion, and I have also seen it on some old cars I restored. I just ordered a kit for this seller who claims it is used around the world for restoring guns, cars, and motorcycles. They say the blackness is related to the amount of carbon in the steel and is a Manganese Phosphate. I will post results when the kit arrives (They make a point to say they don't ship quickly like Amazon!) Their web is: MG34.com You don't need a class III firearm permit to buy from this site, :lol:
Allegheny Arsenal manufactures the finest Parkerizing solution and kits. Our products are used around the world by individuals, hobbyists, professional gunsmiths and firearms manufacturers.
This is a MANGANESE kit which will parkerize three to five long guns. It will produce a dark gray to black finish. The intensity of the color is based on the carbon content of the base metal. Included in the kit is the parkerizing concentrate, a cleaner de-greaser, a neutralizing solution, two sprayers and complete instructions.
This product is reusable and can be stored in a stoppered bottle.
Antique motorcycle and vintage car restorers use our Parkerizing to duplicate the original finish.

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Re: R26 Black Phosphate Plating

Post by Daves79x »

Traditional Parkerizing as used on Harleys, for example, is a bit too gray. Just let the parts pickle longer and you will get black.

Dave
Dave

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