Some of my musings:
In my college days, we studied amplifiers, oscillators, and active filters. In the case of amplifiers, we wanted to have NEGATIVE feedback to enhance stability, while in oscillators and filters, we wanted to have POSITIVE feedback, but tuned to occur at a desired frequency -- it's frequency of resonance. The positive feedback is required to start and sustain the oscillations. The selection of resonant frequency in the filter is important to tune a desired radio station, for example.
In a system with positive feedback, the system's own response to its inputs causes the system to experience more of what's already affecting it. One common example of this is the squealing microphone/loudspeaker systems you may have heard years ago. (Modern systems can detect and eliminate the feedback before you hear it.) This is uncontrolled oscillations, due to positive feedback.
Now consider a "system" of a motorcycle, with rider, and two dissimilar spinning tires. If it's reaction to a bit of sideways/crosswise input (whether due to pavement irregularity or to crosswind/truck wash, or whatever) is to cause it to experience more of the same (whether that reaction is a compression of the suspension, flexing of windscreen, tire sidewalls, or frame, or something as complex as the air flowing around the windscreen, faring, and rider giving a bit of air blast on rider and/or the handlebars, or onto some part aft of the rider, or _whatever_), we may get the system to break into oscillation, with each cycle of oscillation feeding the next.
What we have is: Resonant oscillations.
It's interesting to me, though perhaps not significant, to note that Honda has limited the speed only of the ST1300P model to help to prevent occurrences of "the weave". We can only guess whether this has more to do with a higher regard for the health and welfare of the boys in blue, or whether they consider these two models to be different machines.
Don't overestimate the similarity in performance between the ST1300 and the ST1300P. Among the differences between a standard ST1300P in Police Service, and a "stock, civilian" ST1300 -- many of which change the way the bike interacts with the ground, and the airstream, and all of which have their own resonant frequencies:
Addition of warning/pursuit lights: front, side, and rear
(and many times in Europe, a light mast)
Siren speaker (usually on one side, only)
Fairing extenders
Rear equipment trunk
Antennas
"Cop" stuff under the covers, and/or on the body of the rider: Radios, flashlights, paperwork, manuals, flares, firearms, etc, etc.
Different switch housings, to accommodate more lights, siren, radio, etc.
Handlebar risers, to accommodate the switch housings (which also changes position of the rider, and the CG, which is itself often mentioned in relation to stability)
Different rate springs, front and rear.
Are there more differences? Do these differences make them "different enough"?
Quite a complex system to analyze.
Doug
