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Thread: 1965 Triumph Chopper

  1. #41
    Member BusaSteve's Avatar
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    Quote Originally Posted by El Skitzo View Post
    So after some quick calculations I repositioned the bike and placed in on the same angle as it would sit if I had a 19" front wheel and 16" rear wheel with the tyres I plan I using.

    As you can see the front of the frame is now pointing upwards, in that real 1970's Chopper reach for the sky doing a wheelie while sitting still look. What this effectively does is increase the rake of the neck and pushes the front axle a lot further out. How far? Sitting like this the horizontal distance between the neck and front axle now becomes 585mm, which is 35mm longer than what is legal any where in Australia.




    So the first major challenge with this bike is to solve this problem and get that front axle back within that 550mm limit. There are some options here and the first thing we'll investigate is using a much shorter coil over shock absorber in the front end, so lower the front end and try and get the girder parallel links to sit about perpendicular to the angle of the neck, like the example shown below.

    This would lower the front of the bike and hence reduce the rake at the same time, and pull the front axle back a bit. Would it be far enough? I don't yet know and when I have a little more time I'll play around with that idea and take some more measurements.

    If that doesn't work the next option I will look into is chopping the frame and stretching the position of the neck upwards about 6 inches or so. That is a huge undertaking and will require Engineering and Transport Department approvals before going there, but I won't rule it out.

    Wouldnt the vertical distance remain the same since it is taken from two fixed points no matter the angle?
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  2. #42
    Member El Skitzo's Avatar
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    Quote Originally Posted by BusaSteve View Post
    Wouldnt the vertical distance remain the same since it is taken from two fixed points no matter the angle?
    They're worried about the horizontal distance between the neck and the axle, not the vertical. I can increase the height between the two as there is no direct limit on that (except there is a limit for handlebar height above the seat).

  3. #43
    Member BusaSteve's Avatar
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    In your pic it shows they obtain the measurement from an imaginary verticle line through the centre line of the axle to another that is throught the centre line of the steering stem. This distance would not change if the angle is higher as in your setup with the jack and whatever that is under the rigid tail.
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  4. #44
    Member Phildo's Avatar
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    Quote Originally Posted by El Skitzo View Post
    Not sure if it will pass rego not having a refractor type lens.
    There will also be a specification for minimum height off the ground (I'm assuming). It would be worth checking that one before committing to mounting, welding, etc.
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  5. #45
    Member El Skitzo's Avatar
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    Quote Originally Posted by Phildo View Post
    There will also be a specification for minimum height off the ground (I'm assuming). It would be worth checking that one before committing to mounting, welding, etc.
    That one we'll pass easily as I intend to stretch the frame upwards about 4-6 inches ;-)

    Just had a thought about the lens of the headlight having no refractor in the glass, this could be an easy fix by just having a new headlight lens made cast out of plastic and have refractor shapes cast into it at that point. I had a set of rare Mercury tail light lenses made up for me by Classic Plastic in Queensland by taking a mould off one I had, and didn't cost that much either. http://www.classicplastic.com.au/

  6. #46
    Member El Skitzo's Avatar
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    Quote Originally Posted by BusaSteve View Post
    In your pic it shows they obtain the measurement from an imaginary verticle line through the centre line of the axle to another that is throught the centre line of the steering stem. This distance would not change if the angle is higher as in your setup with the jack and whatever that is under the rigid tail.
    Actually it does.

    If you look at the first picture here where I have everything sitting with the bottom frame rails parallel to the ground


    Then compare that to the second picture where I have set everything up with the front and rear axles at about the same height from the ground, but this now causes the front of the frame to kick up and increases the effective angle of rake in the neck, and therefore pushes the front axle further away (in a horizontal plane) to the vertical line dropped from the centre of the neck.


    What I need to do is end up with the front and rear axles at about the same height from the ground (as in picture #2 ), but also have the bottom frame rails close to parallel with the ground (as in picture #1 ), which we'll achieve by stretching the length of frame front down tube upwards by 4-6 inches. I need to try and retain as close to possible the original rake of the frame neck in order to pull the front axle position back into legal limits.
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  7. #47
    Member BusaSteve's Avatar
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    Right now I get it because the rake angle increses the distance grows...I even measured it on my computer screen...grew fro 60mm to 70mm. IMO the second pic is better I know they have to have set limits but why they are so conservative is so boring.
    Smoke me a kipper...I'll be home in time for breakfast

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