1939 Sq4 sprocket finish
1939 Sq4 sprocket finish
Hi. Can anyone tell me what the finish was on the rear sprocket for my 1939 Square Four 4G? I have seen several restored bikes and some have (black) painted sprockets, others appear to be cadmium plated. Any information would be greatly appreciated.
Ray
Ray
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Re: 1939 Sq4 sprocket finish
Rivet counting 'in extremis'. Depends on how often they have been renewed (if ever).
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Re: 1939 Sq4 sprocket finish
Plating can cause them to be brittle. Hydrogen embrittlement. I've seen one cracked. Leave it as is. Nev
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Re: 1939 Sq4 sprocket finish
Only chrome will do that and then only with certain types of steel. The originals would have been Cosletized in 1939, Cadmium cam in around 1950.
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
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Re: 1939 Sq4 sprocket finish
Respectfully I suggest you check on that. Even stripping can cause it. There's a heat treatment process that can be done just after the plating/stripping operation. Hot oil would do it but it varies on the thickness.. Nev
Re: 1939 Sq4 sprocket finish
Thanks Roger. I'm not exactly sure what cosletizing is, so I guess I still have some homework.
Ray
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Re: 1939 Sq4 sprocket finish
I think it's a good black undercoating process used by Sunbeam and Ariel just before the 30's. Chrome displaced Nickel in 1930. Nev
Re: 1939 Sq4 sprocket finish
Thanks Nev. So far I have been unable to coax an answer from Google here in Canada, so at least I now have something of a lead.
Ray
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Re: 1939 Sq4 sprocket finish
Coslettizing
Producing a black, rust-resisting surface on iron and steel by boiling for some hours in water containing phosphoric acid and iron filings.
https://www.engnetglobal.com/tips/gloss ... slettizing
Commonly used on bolts, nuts and similar cycle parts. Doesn't resist rust very much which is why bikes have so many rusty nuts and bolts!
(Trying to think of an obvious example, it's the original finish on that eye-bolt that is used to draw the gearbox backwards/forwards and all the spire-bolts on the later bikes.)
HTH
SG
Producing a black, rust-resisting surface on iron and steel by boiling for some hours in water containing phosphoric acid and iron filings.
https://www.engnetglobal.com/tips/gloss ... slettizing
Commonly used on bolts, nuts and similar cycle parts. Doesn't resist rust very much which is why bikes have so many rusty nuts and bolts!
(Trying to think of an obvious example, it's the original finish on that eye-bolt that is used to draw the gearbox backwards/forwards and all the spire-bolts on the later bikes.)
HTH
SG
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'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
Re: 1939 Sq4 sprocket finish
Thanks Simon. I guess I need look no further. Of course I'm not sure I am going to be able to reproduce that finish myself...
The online engineering dictionary appears to be a handy reference.
Ray
The online engineering dictionary appears to be a handy reference.
Ray
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