Wobble!
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The dictionary defines it....
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Wobble (wob'el) To
move erratically from side to side;
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and unsteady motion...
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To better
understand the solutions to fixing "the big wobble",
check out the article below by Bob Loberg for the
cause, the cure and mounting
instructions. Also read what you should know before
adding a damper.
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Check out the pictures below of steering
dampers. Click to see large view.
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CAUSE:
Let's assume that your bike is properly
maintained; that is, good tires, straight and true wheels, the suspension
and steering head bearings are snug, everything is copestatic! You've
even laded up your travel gear properly. Chances are your bike will travel
down the highway straight and true, hands off!!!
Let's add the sidecar. Now the bike has
changed its habits. Especially on deceleration at 30-35 mph. It never
shook its head before, why now?
Adding a sidecar is adding a non-powered,
off-centered mass of weight. The weight very simply is trying
to pass you on deceleration and drip behind when you accelerate.
These actions also will try to turn you right (on takeoff) or
left (on breaking). Both of these actions are directly transmitted
to your front wheel and its TRAIL (see drawing). Think of trail
as a caster or the ability to center the steering when rolling.
The more trail, the more self-centering action. Road bikes generally
have more trail because they don't have to be maneuvered quickly
between trees or on a wood trail (hopefully not often!).
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More trail also makes them less sensitive
to cross winds and turbulence from trucks. Dirt bikes usually have less
trail for quicker woodsy type steering.
If you sit on your bike and turn
the bars full lock left to right, you will find that the front
rises and falls very slightly (witness some guy on a long forked
chopper sometime) - the highest when the bars are straight and
low on either side. This action, although very slight, with the
mass offset weight of the sidecar, will produce an oscillation
from side to side - the wobble.... (combined with the weight transfer
to the front wheel) on deceleration.
Very few bike/sidecar combinations are
without a low speed oscillation and usually can be overridden by a reasonably
tight grip on the bars. But what about the wife or non-strong type person
hanging there helplessly flopping from side to side? A Steering
Damper
in those anxious moments could be the most important part of the combination.
Kind of like a safety valve on your steering/suspension. Of course, there
are many other factors that also produce oscillation (loose mounts etc.),
but we've touched on the major ones.
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A CURE: |
After you have made sure all bearings are
snug etc., you can add a Steering
Damper. The best combination I've
found and I think I can speak for Doug Bingham too, is a standard Volkswagen
shimmy damper. They are readily available from the local auto parts
store. They have a long enough stroke and are made in a couple of different
mounting designs.
There are many ways we can mount a Steering
Damper. The most ideal would be to anchor the base end on the bike frame
and the rod end on the lower triple tree (Fig. A).
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As you know, in about 99% reality, this
cannot happen. Somewhere down the road we have acquired a frame mounted
fairing crashbars, driving lights, air horns, etc., etc., etc., all of
which try to occupy the same spot.
In the drawings following, I will attempt
to show some alternate methods of mounting. Some parts will be available
from your dealers, others from a local auto store or industrial supply
store.
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MOUNTING: |
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This is a typical mounting
that will not interfere with fairings
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and other add-ons.
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The
bottom of damper could be mounted in any of these places. |
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If you mount the damper anywhere on the
fork leg, it MUST move freely up and down and let you turn full lock side
to side. |
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Before
adding a damper, check:
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- The steering
head bearings
- Tire pressure
- Spokes
- Loose mounts
- Wheel bearings
- Excessive
toe-in-toe-out
- Rear suspension
bushings
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