G15 Frame geometry anyone?

Information relating to the Matchless G15 or AJS Model 33 750cc twin. This also includes the G15 Mk II and the G15/45
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Joined: Tue Nov 13, 2012 5:22 am
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G15 Frame geometry anyone?

Postby ManxmanGP » Mon Dec 03, 2012 2:32 am

Hello I purchased a 1967 Matchless G15 MK2 basket case with a frame that has been chopped. With a diagram of the angles involved a local repair shop can make repairs and put it right again. So does anyone know of a blueprint of the G15 type frame that I can find online or perhaps purchase? Mine is a 1967 G15 frame. The angle needed is the relationship between the twin front down tubes axis and the steering stem axis in relation to the vertical. Thanks

Posts: 9
Joined: Tue Nov 13, 2012 5:22 am
Location: NV, USA

Re: G15 Frame geometry anyone?

Postby ManxmanGP » Mon Dec 03, 2012 5:28 pm

Just to be clear, what is needed is the angle that the twin down tubes make with the vertical, and/or the angle that the steering head axis makes with the vertical, either measurement /spec will do.
As an aside, I have the length of the top tube between the lugs fore and aft as 17 7/8". However my belief is that the lug ends could be an unreliable reference point for measurement. But if some good member with a G15 frame can please measure their frame top tube length (between the lugs) and let me know the distance that will be of interest too? Thanks, Steve

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Re: G15 Frame geometry anyone?

Postby mdt-son » Wed Jan 02, 2013 8:24 pm

Steve,

I have several G/N15 frames, unfortunately they are stored at a remote location. However, the front part of a frame diamond off a 1967 G15CS is readily available. I can help measuring the headstock angle on this piece if you like.
Please email me off list if you want me to help out.

-KS

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Posts: 102
Joined: Wed Feb 01, 2012 1:22 pm
Location: 5550 HORDALAND, NORWAY

Re: G15 Frame geometry anyone?

Postby mdt-son » Wed Jan 02, 2013 8:29 pm

Steve,

All Matchless frames were brazed. If you want the frame to be as strong and lasting as the factory made them, you need to seek a specialist firm brazing the old way. There will not be too many of these firms now.
Maybe a racing bicycle builder? Just a thought. There are specialist firms offering this service in the UK.

-KS

Posts: 9
Joined: Tue Nov 13, 2012 5:22 am
Location: NV, USA

Re: G15 Frame geometry anyone?

Postby ManxmanGP » Tue Jan 29, 2013 6:35 am

Good advice thanks. That brazing process was pretty elaborate no wonder the frames are so strong. I did get the frame sorted so thanks for the replies.

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