Frame Identification

[RichardS]

Hello all, this is my first post here, although I've been an AMOC member on and off since 1978!
I have a frame I'm trying to identify, I can't quite reconcile the various factors so maybe others can fill in some of the blanks.

The frame in question is a twin downtube frame, so 1960on. The rear subframe is mounted on the top lug above the swinging arm and the shape is akin to the trials version. But, my understanding is that the 16C was a single down-tube frame.

Conversely the frame is definitley not the same as a normal 1960 -CS model as I have one to compare.

Here's the unidentified frame (someone has ground off some of the lugs and drilled a few holes in what I assume is a lame attempt to lighten it)

IMG_20201206_121542.jpg

Here it is, side by side with a standard -CS frame ( I have the original 1960 green log-book to proove it!)

IMG_20201213_153536.jpg

Any insight would be most welcome
Richard

[mdt-son]

Hi RichardS,
the frame looks similar to a 1966 ISDT frame. Maybe it's a survivor? It has the 1963 on swinging arm featuring forked shock mountings, so the basis is probably a late type G80CS.
Look up the web site "Working at Associate Motor Cycles", go to "Competition Shop". You will find the ISDT bikes depicted. There is another picture in one of Roy Bacon's books. The frame could very well be an AMC Competition Shop special!

- Knut

[RichardS]

Knut,
Thanks for the useful observations and the Working AMC Link. I had noticed the swinging arm, but was not sure when it was introduced. Looks like it's a little later than I had thought.
I will give it all a closer inspection when I get to the garage again soon I hope - I've had a few family events recently and not been able to get to it

Richard

[RichardS]

Those sharp-eyed among you may have noticed the frame is missing the front tank mounts, so I need to fabricate some.

I can get the span easily from the tank, but can anyone measure a frame and tell me the dimensions A & B on the sketch here please? I need to know the height and fore & aft position. Using some known datums - the bottom front engine bolt centre & the top rear sub-frame mounting centre to the centreline of the front tank holes.

I should have taken the dim's off the other frame before I sold it - hindsight is a wonderful thing

Thanks

[SPRIDDLER]

You haven't said whether there's any number on the frame so presumably there's no frame number or you'd have identified it from that.

(O.K., I can assume there's no number, but if you don't ask the obvious.......... )

[mdt-son]

Hi Richard,
I've taken readings off a 1965 G15 frame which should be identical as fas as these dimensions are concerned.
A = 470 mm
B = 487 mm

- Knut

[RichardS]

You haven't said whether there's any number on the frame so presumably there's no frame number or you'd have identified it from that.

(O.K., I can assume there's no number, but if you don't ask the obvious.......... )

Sorry, yes, I didn't mean to tease, I've been really innundated recently

I did indeed find a number under the rust. It's been partially sanded/ground over, but is legible as C10816. It is not recorded in the register so I can't tell what it originally was. Looking at the registration process, I need to get the thing on its wheels and looking like a bike before I can move forward so I've been starting to progress the overall plan.

My intention is to build it up as a 500 scrambler, but it will be a Bitsa.
Undated pre-54 competition motor (see my other post on EngineID), AMC gearbox, Norton forks & front wheel, AJS rear wheel, alloy primary case. I do have a AMC half width hub 21" front wheel, but the forks that go with it are really sad. Getting them ground and hard-chromed is not cheap whereas the Norton forks are bigger tubes in great condition and a better brake - I will obviously put a 21" rim on it.

I'll steal the 500 top end off the '49 G3C I have and make that the 350 it should be (but never has been while I've had it). I have a 350 alloy top end, but need to rebore it as it's badly scored from an gudgeon pin end. I'd forgotten about the damage, but remembered as soon as I started inspecting parts. Sad as it is otherwise a mint standard bore, but there you go.

I've had all the major chunks stored for over 30 years - life and all that kinda got in the way, but I was recently spurred to get on with it by a friend's persistent (good humoured) needling and a realisation of one's own mortality, which rather focussed my thoughts.

[RichardS]

Hi Richard,
I've taken readings off a 1965 G15 frame which should be identical as fas as these dimensions are concerned.
A = 470 mm
B = 487 mm

- Knut

You're a gentleman sir, thank you.

[SPRIDDLER]

Sorry, yes, I didn't mean to tease, I've been really innundated recently

I did indeed find a number under the rust. It's been partially sanded/ground over, but is legible as C10816. It is not recorded in the register so I can't tell what it originally was.

It may help to look at this post with frame numbers which I put on the Forum a couple of hours ago ........

viewtopic.php?t=30061

[mdt-son]

> My intention is to build it up as a 500 scrambler, but it will be a Bitsa. .... Norton forks & front wheel

The headstock was made to accomodate Teledraulic forks. If you intend to rebuild it as a scrambler, the heavy Norton parts are a waste, and you don't need an 8" stopper. I suggest you fit proper Teledraulic forks and a '63 front hub, like it was originally. You could still improve braking by altering the brake plate into a TLS, or convert the brake plate into hydraulic operation as per Malcolm Saggers.
AMC's full width hub providing straight pull spokes is the natural choice for a scrambler.

- Knut