In answer to Stu Rodgers question about a strange cambox in Roadholder 447 I submit the following.
In 1937 the new double knocker cam box failed and a single knocker was quickly made to resemble a double knocker. I have attached the stories I downloaded many years ago.
Whoops, in order to open the file you have to remove the -0 from the end of the filename. I have no idea why and it may still not work
It looks like the rockers…
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Works cambox.
Hi Bill/David,
This cambox was first used in 1935 on the works engines, and again in 1936. I have never seen a period photo of the 1937 DOHC cambox and if there were problems I guess Nortons would not want any adverse publicity. When I last visited Stu Rogers about 3 years ago he had a reproduction cambox of this design in his workshop. This was not too much of a surprise as several people have been involved in making these reproductions including the late Julian Harvey, Geoff and Ian Bain and Ian Bennett. All these engines used the usual hairpin type valve springs. The only other well known unusual Norton cambox is the one used by Jack Williams in the 1937 senior TT which had fully enclosed rockers and coil springs and had a cylinder head with provision to take the cambox to make it completely enclosed.
My best guess on the one Stu saw is that it could have been made to use in a Formula 500 race car. I think there have been at least 2 reproduction engines made over the last 60 years, excluding the more original Summerfield and Molnar DOHC Manx engines. It is a pity Stu didn't take a few photos for our perusal.
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It looks like the rockers are longer in order to give enough room for the short pushrods, so the head preserves the same valve angles. Was the head the same? And did it use coil springs?