What Frame is this?

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The number could be anything depending on it being cast, stamped, position, spacing.  Can be a serial number, part number, quality controller ID, build date or even frame number (1948) Give us a picture it may well trigger off some response.   Cheers

Jon

Hi Bill,

I've attached the details of the data for an  Inter to racing specs. Now you've added some photos, I'll stick my head up and make some comments.

I) The number on the top of the headstem casting looks fake as the last two numbers are of a different size to the first three.

II) The casting number on the web of the headstone is the same as on my 1948 Inter frame.

III) There is no bracket on the rear of the headstem to attach the Andre steering damper required for an Inter to racing specs.

IV) Do you have a frame number on the l.h.s. below the petrol tank mount? If you don't, this would ring alarm bells to me.

V) The rear plungers look like they are off an ohv or sv frame as they don't appear to be inclined far enough forward for an ohc frame. (angle of photograph?)

VI) The frame is not prewar so it precludes it as a frame for an Inter to racing specs as these weren't listed after the war.

VIi) The lower cradle and lower rear end look postwar Inter.

VIiI) What is the frame?  Without more detailed inspection, I think that it may be a non ohc frame converted to take an Inter engine.

Over to the experts for more comments!!

The front downtube engine mount has the scalloped opposite face. That's associated with Manx but if it's only one lug then that suggests Inter. The Andre damper wasn't used post war was it?

My prewar engine number is stamped on the left side of the front downtube engine lug (and I don't want anyone to tell me it's wrong! It's on the bike and the registration documents which is good enough for me...).

Since yours has a frame number stamped on it, and the chances of it's coming alongside another with the same number either physically or in some document trail is near zero, I'd have no hesitation (in UK) in applying for a new age related plate with that number. It's only a hard stamped mark to match your documents so it will be a tiny bit easier to recover it if someone took it away. Not a painting by Leonardo...

Is the straight top tube correct? If you search this site you'll find discussion of differences between ES2 and Inter frames. The 500cc OHC engine needs a bit more headroom that ES2 or Model 40 I believe.

If its been molested it was a long time ago, except for the seat down tube repair, a classic fail point. What is stamped on the top seat lug near side? Mine is 13166, which I have spotted on other machines and would suggest it’s a part number.  Flat behind the seat tube is right as is the straight top tube. I have a 48 and it has the Andre steering damper lug, albeit sawn off.

one window lug one not is odd but what is the distance between? Mine is 8 3/4”

My headstock lug is also stamped 144nn and on the absence of any other stamping is used as the frame number.  What is, the diameter of the headstock? Inters are larger than ES2 if you have one to compare… 

J

Fantastic to have such  expertise and response  in a  Forum.  We are lucky.

Here are some shots of ES2 and standard '48 Inter frame to show substantial differences. Your front tank mount lug takes the alloy plate to mate with the thru-bolt tank I believe.

The quickest way of learning of the frame's history is to contact the Records Officer with the frame build number and he can provide you with the original frame number and its' delivery specifications.

Hi Bill / all,

   Yes I agree with Michael that this is an un-molested circa 1948 Clubmans International. These used Manx petrol tank mounting lugs, but the tank was the same size as the standard Inter but with bolt-through fitting. This was to meet the criteria of the Clubmans TT regulations. The number stamped on the headstock is, I believe, the frame shop number. This was a similar shop reference number as used on the engines, but only used for a short period of time. Paul Watkins is the man you need to contact to search the records for the original frame number although there will be a fee for this. There is also the possibility that this could be a spare frame, which could be purchased from the factory with-out a frame/vehicle number.

"...circa 1948 Clubmans International. These used Manx petrol tank mounting lugs, but the tank was the same size as the standard Inter but with bolt-through fitting. This was to meet the criteria of the Clubmans TT regulations. "

Can you elaborate on the Clubmans' TT regulations here please?  The rigid and plunger Clubmans' Inter got bolt-through tanks.  All featherbed Inters got a bolt-through oil tank, but a strap over the petrol tank. By the mid '50s, the Inter engine was obsolescent for racing.

Paul Standeven

Hi Paul,

   The Clubmans TT races were the fore-runner of the production TT and machines had to be road legal models with a few modifications allowed. In the case of the Norton International, the fitting of a Manx petrol tank with it's extra capacity would give an unfair advantage, as they were not catalogued as an optional extra.

   Although works machines were fitted with bolt-through tanks from 1934, race spec bikes sold to the public didn't get them until 1939 and almost all of these were fitted to plunger frame bikes. Having said that, many rigid bikes have been fitted with these tanks retrospectively.

Interesting comment from Richard regarding spare frame.  My machine is originally a 37 Manx  spec Inter . The whole has been built into a plunger frame with Manx bolt through steel tank (no pie crust) and Roadholders,  but the rest is from the 37 machine. Engine, box, wheels, oil tank etc.  I would suggest the prewar power train was still of high potential after the war, but the rigid frame renowned for breakages in competition was not.  My frame has the shop number as Richard suggests and in the web there’s is a large stamped “S” .  The frames were certainly available as a spare.

 Interesting stuff

Jon

Which frames were "renowned for breakage"? I assume that the plunger frame might have been more problematical than the rigid frame which was triangulated. Just curious.

The rigid frame took all of the beating as it was all unsprung.  The TT course was not fully metalled until after the war so they were handing out quite extreme punishment.  Plunger frames also broke, as per frame in question but this is more of a design issue.  See George’s repair and explanation on Sheldon’s .  Of course this was not known straight after war and the perception after Daniel’s record breaking 38 run suggests this is the way to go. As would the then owner of my machine…

Cheers

J