Frame, swingarm alingment

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Hortons Norton

Hortons Norton

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I searched and found a few post on this but was wondering how some of you guys have addressed this. My swingarm is off to the left a bit and I know this is common on the Commandos but I would like to get it a bit closer. Thanks, Chuck. :?: :?:
 
That's how Norton designed it! Whole cradle assy including engine, gearbox and swingarm are offset to the left by 3/16 to 1/4" depending which bike you measure. Rear wheel is consequently offset to the right same amount in swingarm to compensate. No-one I've ever asked seems to know why. As a further result the rear shocks don't sit vertical since the top mounts are not offset to compensate the swingarm offset.
If you want to align the wheels get the front centred in the forks and assuming nothing is bent the rear wheel has to be offset right by the amount the cradle assy is offset left. Since that depends on individual machines the easiest way is to measure the front ISO offset and assume the rear ISO is similar (but it may not be like mine). Difference between tube projecting from LH and RH is the offset. On mine I had appx .31" LH and .62" RH = 0.31" offset! On the rear it was closer to .25" so I machined the long side on the front and spaced out the short side.
Check out http://vintagenet.us/phantom/wsc.html
 
Well I guess I asked for it, Thanks a bunch guys. I think the second article gave me a headache LOL LOL. My 75 seems to handle GREAT and none of these things were done to it. As I have already painted and have the motor in the frame I think I will just continue the build and hope it handles as well as the 75. I think I will check it when I put the rear tire on and maybe space it from there. It would be nice to check all the things they talk about but I think I should have done that first and now its too late. I really don't ride my Norton hard as I have another bike to ride if I have steam to burn off (S1 Buell.) But thanks guys you are a great source of info. I need to go get some aspirins, Chuck. :cry: :cry:
 
Sorry about that! Still worth making sure the front is centred in the forks and the rear has 3/16" to 1/4" right offset in the swingarm. That will be close.
 
Thanks Keith, I will check the front and make sure it's ok. It is kinda odd how it is set up though, There must be a reason, Right? I find it hard to believe it was a mistake and they just kept building them this way. Maybe one night in a pub some engineer figured out that with the rotation of the earth as it is this would help with the handling? And the rest is history. Someone must know, Help out guys. :wink:
 
It's something that bugs me and I can see no reason but its deliberate as all the mounts including the headsteady are biased left. Interestingly they left the aircleaner centred in frame so the carb rubbers are not aligned.
Have talked to most experts, White, Emery etc. but none came up with a cast iron explanation. Someone like Bob Trigg would know since he designed the ISO system (or Peter Williams). Frank Damp on here might have a clue? One day! Never asked the club experts so I'll do that now it's in my head again.
 
There can be many reasons why the engine is offset in the frame of a bike - clearance issues, vibration dampening, torque compensation, weight distribution (centerline of the engine may not be centerline of engine mass), aesthetics, plain old screw-up, you name it.

Sometimes the reason behind a particular design becomes moot, but the design isn't changed because of cost concerns.
 
I think Cash is spot on. I looked at all kinds of clearance needs and never spotted this. It's so obvious really. With a std OEM tyre from the 70's it might have been ok but looking at my 110 section it is only 1/4" from the chainguard. Thanks.
 
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