Custom fitting a steering damper

Discussion in 'Motorbike Technical Discussion' started by sean_q_, Jul 1, 2010.

  1. sean_q_

    sean_q_ Guest

    My Magna-sidecar rig needs a damper to stop a bad
    steering wobble between 10 and 60 km/hr. I bought
    a used damper with a 3" travel but am having
    trouble fitting it to the bike. There's no place
    anywhere I can find to locate it by direct attachment.

    So after futzing around a while and making measurements
    I came up with the idea of cables (like clutch cables).

    One cable for each side. They would attach to the lower
    triple clamp at a radius from the center of steering
    rotation such that the stop-to-stop distance is slightly
    less than the damper's travel.

    The cable jackets would be anchored to the frame,
    and the cables would lead to a location convenient
    for mounting the damper (such as in front, between
    the roll bars). Each cable would only pull, not push.

    Actually my 1st idea was bare flexible braided wire
    (like they use on sailboats) with pulleys. This could
    present less frictional load on the steering than
    the cables, but cables seem easier to locate around
    obstacles such as the radiator and frame members.

    ps. Another bright idea: If the cable mounting points
    on the triple clamp result in too much travel,
    I could "gear it down" with a pivoting rod
    at the damper end. The cables would attach
    to the end of the rod, with the damper fixed
    to a point on the rod closer to its rotation axis.

    Anyone have an opinion on this scheme? Especially
    drawbacks: I'd rather find out them out now than
    by accident.

    TIA, SQ
    sean_q_, Jul 1, 2010
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  2. sean_q_

    S'mee Guest

    S'mee, Jul 1, 2010
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  3. sean_q_

    Andrew Guest

    I think this is a terrible idea, and you should go about creating an actual
    mounting point on the frame.
    Why do you want something so simple to turn into something so complex?
    You're just asking for trouble.
    Andrew, Jul 1, 2010
  4. sean_q_

    sean_q_ Guest

    Other considerations aside, there would be no slop
    in the system because I would tension the cables
    such that they pulled slightly against each other.

    sean_q_, Jul 1, 2010
  5. sean_q_

    ? Guest

    I agree. He can buy a clamp for the fork end from a mail order catalog
    and fabricating an anchor point for the frame end is no big deal.

    Alternatively, there are *rotary* steering dampers that mount above
    the handlebars.
    Sometimes I think he's just trolling...
    ?, Jul 1, 2010
  6. sean_q_

    sean_q_ Guest

    Thanks for the replies everyone. Looks like the jury
    is thumbs-down unanimous except for one abstention
    (ie, the Honorable Member from Montana).

    Anyway I crawled around under the bike and had
    another look... *maybe* I can install the damper
    just above the lower triple clamp. On the left side,
    because the radiator filler cap gets in the way
    on the right.

    However, with the wheel straight ahead the damper
    shaft should be at 90 degrees to the steering,
    and in this position it wouldn't be. Therefore
    the damping force would be somewhat asymmetrical
    at the center position, which is where I need
    damping the most.

    sean_q_, Jul 1, 2010
  7. sean_q_

    Beav Guest

    I think this is going to get Very Very Interesting. Or something.
    Jesus, you're making a mountain out of a zit. Cables are (to be brutally
    honest) the most stupid fucking idea I've ever heard.

    Do some research on tank slappers and the forces "enjoyed", then work out
    how much work the cables would have to do and then ask yourself this simple
    question ... "Why the **** has no-one ever thought to do this before?"


    2 minutes in a workshop with a welder and the damper would be on and done.
    Think about it.
    Beav, Jul 2, 2010
  8. sean_q_

    sean_q_ Guest

    Thanks for your brutal honesty. At the very least I have
    the dubious honor of holding some sort of record.

    Really, the idea seemed brilliantly original at 2 in the morning.
    However, I began to get a glimmer that all was not well when
    I got called a troll by Krusty of all people.

    sean_q_, Jul 2, 2010
  9. sean_q_

    tomorrow Guest

    What was MUCH worse than that was that the technical part of the
    miserable old coot's response was dead on. That should be enough to
    make you rethink the whole idea, even if nothing else did!
    tomorrow, Jul 2, 2010
  10. sean_q_

    S'mee Guest

    That was so you could weld a mounting tab on the frame.
    S'mee, Jul 2, 2010
  11. sean_q_

    Beav Guest

    Not a record to be really proud of though, is it? I mean a little thinking
    and a touch of research would provide you with enough material to realise
    yourself that idea's need to be given consideration before they're offered
    up for "confirmation".

    Always take a pen and paper to bed, then you can write the idea down and
    read it in the morning when your brain has actually switched on. It'd save a
    lot of "odd" comments being thrown your way.
    It's not like it's the first time though, is it?
    Beav, Jul 2, 2010
  12. sean_q_

    sean_q_ Guest

    However perhaps a viable idea did come out of the dialog --
    if I can't squeeze the damper into the tiny space near the forks,
    I may be able to connect it via an all-mechanical linkage
    (ie no cables, wires or pulleys) that would give me more scope
    for adjustment. An advantage since I don't know at this point
    how much damping I'll need. Details (and pix) later.

    sean_q_, Jul 2, 2010
  13. sean_q_

    tomorrow Guest

    I'm familiar with the Honda Magna, and I've had several sidecar rigs
    in my day. I can't visualize why this space is so tiny in the case of
    your rig.
    tomorrow, Jul 2, 2010
  14. I've seen steering dampeners fastened/bolted to the side of the lower
    triple clamp and the upper front sidecar bracket. No cables. Works well.
    Beauregard T. Shagnasty, Jul 2, 2010
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