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dave m
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Hong Kong
Joined: 07/18/2010
Posts: 3

Gentlemen, I live in Hong Kong and am fortunate enough to have a 1929 R57 that I bought in a parlous state (the bike not me!) when I worked as a technician for BMW Concessionaires in London in 1979, It had been found in France and had been modified with twin carburettors, a foot shifter, different exhausts and a tank cover to make it look like a more modern 'saddle tank' model. There were quite a few parts missing, such as foot brake, intake manifold, gear lever and gate, Magdyno, speedo etc, but fortunately most are common to a number of different models from the same era. I have been trying to source parts for it for the last 30+ years and with the advent of the internet and sites like this one I feel more encouraged then ever before that I might actually be able to complete the machine in a reasonable length of time. I am currently in the process of restoring 3 Norton Commandos and a 1927 BSA 500 side valve and I recognise one of the contributors 'unclviny' from the Jerry Doe Norton site.

I have looked through all of the postings in this section and was pleased to glean such knowledge as the appropriate dates when Nickel and chrome were used. Can anyone advise whether a bead blasted finish on the crankcases would be appropriate, the cases are quite dirty and I doubt that I would otherwise be able to get them up to a decent standard.

I look forward to posting many foolish questions and getting back informed answers on this site.

Regards

Dave m

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Dave M

Bruce Frey
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VBMWMO #6316
Texas Hill Country, USA
Joined: 10/27/2006
Posts: 574
Welcome, Dave! An R57 is a

Welcome, Dave! An R57 is a very cool machine!

I think a lot depends on the size of the media and the pressure. When I lived in Spain, I had a small blasting cabinet and a compressor of marginal size. It did a nice job with the bag of media that came with it, but I do not know what size it was. I was only able to use relatively low pressure. On the other hand, I have an engine case that has been seriously "over blasted". It does not look good and I am not sure what to do with it or how to fix it. I have heard that large media (keeping it fresh) and low pressure give the best results, but I don't have enough first hand experience to confirm that.

I would experiment with some small pieces.

People also report good success with baking soda, plastic beads, walnut shells. Baking soda seems like the best solution. When I get re-set up in the USA I hope to get a decent compressor and blast cabinet. I recently read on the internet about a person who made a soda blasting rig with a compressor, air gun and some plastic tubing.

Cleaning the parts afterwards is always critical....especially so with glass beads.

As you probably know, there is a reasonably good supply of reproduction parts for flat tank bikes. You can find links to them in the "Resource Links" tab. Huggett, Koni, Dreher and Oldtimer Garage are reliable sources from my experience.

My daughter spent a year in HK teaching English in the Chinese school system so we took the opportunity to visit her twice. She lived on Lamma Island..an interesting place. We really enjoyed our visits!

Bruce

dave m
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Hong Kong
Joined: 07/18/2010
Posts: 3
Bruce, Thank you for the

Bruce, Thank you for the prompt response. I have access to a blast cabinet and I am familiar with the different blast media and the subsequent results, my question was really whether a blasted finish was era-appropriate for this particular machine, I want to do as accurate a restoration as possible, given that the machine is relatively rare.

I'm glad you enjoyed your visits to Hong Kong, if you return hopefully I can steer you in the direction of some of the classic bike activities that occur, while your wife goes off and spends your money!

Dave

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Dave M

bmwmyplace
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Australia
Joined: 02/26/2007
Posts: 168
Blasting

Dave not trying to teach you to suck eggs,.... but dont be tempted to use any blast media inside the cases , in particular glass or oxide, I have seen awful results of impacted media , it gets into the micro structure of the metal..... Soda is probably ok)

.there is an excelent system desingned in the UK called vacqua Blast it is a wet system using various types of media that will clean the cases without damaging any numbers or machined sufaces, added bonas is that it will close the micro structure and prevent further dirt particles from entering the pores of the metal and keeps the engine clean... well worth looking for cheer peter

dave m
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Hong Kong
Joined: 07/18/2010
Posts: 3
Thank you for the replies, I

Thank you for the replies, I am quite familiar with the technical aspect (such as it is) of media blasting. I really want to know whether the surface finish thus obtained is historically correct (or close enough) from a restoration point of view.

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Dave M

Peter
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VBMWMO #8076
Australia
Joined: 03/04/2007
Posts: 133
Hi Dave

Hi Dave, I get your point and offer the following, when in doubt refer Willy Neutkens and how he prefered to have his bikes presented. In most photo's and especially of the R57 the cases appear with a patina and not blasted, cleaned maybe but I see no evidence of blasting. I would also suggest that as 'new assembly' the cases were not blasted, a quick finishing process after the casting maybe.

You may consider an ultrasonic cleaning first and see how that looks.

This is only my opinion I know some folk who prefer that "perfect" look however I like a bit of history about these old machines.

Cheers.

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R42, R12, R51/3, R69S

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