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Commando motors in Featherbed frames or other frames

Discussion in 'Other Norton Motorcycles' started by ashman, Dec 22, 2013.

  1. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    Most featherbeds have 26 degrees - unless its been in an accident ?
     
  2. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    Stainless work hardens very rapidly, when it gets worked.

    It needs to be continually annealed (softened) as they go along.
    If they are not set up for this, they probably wouldn't want to know.
     
  3. pommie john

    pommie john

    Joined:
    Nov 18, 2005


    It's a bit tricky to measure at the moment but there appears to be about 55mm of offset on the yokes. That's as near as dammit 2 1/4" which is I believe the standard offset.

    The story is a little more complex in that when I bought the rolling chassis the yokes had a taper in the top clamp as most Norton yokes do. However at that time short roadholder stanchions were not available anywhere so I had to use Commando stanchions which were too long for the featherbed. The solution was to bore the top yoke to make it a pinch bolt type. We could have shortened the forks, but I rather liked the idea of being able to slide the forks up and down to change th e teering geometry.
     
  4. pommie john

    pommie john

    Joined:
    Nov 18, 2005

    That would be it. The guy who did it is also a racer and he made them for a very reasonable fee.
     
  5. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    I didn't measure it, I simply asked the question - my friend the triton racer is very reliable. They cannot be 26 degrees and use yokes with such little offset with 19 inch wheels, everybody would be falling off them. The replica frames made in Australia are usually 26 degrees, and use 18 inch wheels - they handle radically differently to original manx frames. If you fit 18 inch wheels to an original featherbed, it usually makes the bike tend to run wide in corners, and it becomes very heavy to ride.
     
  6. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    The factory drawings are reportedly 26 degrees - same as the road bikes.

    We had this discussion here previously.
    Did you not take note of it ...
     
  7. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    What does 'reportedly' mean ? I know for certain the manx is steeper in the front end than the TZ350 which has 26 degree rake. The Australian made replica featherbed frames have 26 degree rake, they are changed from the original to handle differently and accommodate the effect of fitting 18 inch wheels to get decent rubber. From my own memory of manx fork yokes, you probably couldn't use them safely with a 26 degree rake and 19 inch wheels, except if the motor was a lot heavier.
    Where does your info on the original manx featherbed geometry come from ? Next time I go to a race meeting, I will take my magnetic base protractor with me, and I'll find a genuine bike and measure it. I will also check with the guy who makes the replicas. This is bullshit.
     
  8. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    It is - and all of it seems to be coming from the same place...
    We'd rather back Mr Sprayson and the Norton Race Shop for what makes a winning bike.
     
  9. oldbeezer

    oldbeezer VIP MEMBER

    Joined:
    Nov 2, 2017
    Just followed the link to this in the Weak link thread. I do admire your bike, at one point in time I was thinking about a Commando in a featherbed but it never happened. I gotta ask, is that a single sided lower fender stay? I guess you came up with that before Ducati came up with the single sided swing arm. I like that too, all of the other stays with extra bends or whatever look pretty clumsy to me.
    Jim
     

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