I was thinking....about "Low Speed Wobble" in sidecar outfits and also less common on trikes.
Based on my own personal experiences, and a lot of thought, this is what I think is an accurate description of the effect.
Not to be confused with sidecar outfits turning right or left, but only moving straight ahead usually at lower speeds.
First: "Low speed wobble" is a real, and an inherent fact of traditional sidecar operation. They ALL "wobble." All that can be achieved is minimising "wobble," not elimination.
Steering Damper - Does NOT eliminate "wobble" a steering damper reduces the felt effects of "wobble" to the rider. (The pressures that cause and create the front handlebar movement are still in affect). The same goes for wider handlebars and weights on the ends of the handlebars.
So to reduce "wobble" to an acceptable level.
I think it would be helpful to relate sidecar adjustments and possible causes directly and only to "wobble." I am trying to eliminate all possibilities that do not relate!
A UK left mounted sidecar has only 3 possible conditions it might be operated under....
Consider the issue of what we call "Wobble".
What is Wobble? Wobble is the minute right to left movement of the handlebars at low speeds that goes away as speed increases and returns at a predictable speed upon de-acceleration.
Wobble is ONLY present while going straight down the road (condition 1 above) and is felt at a predictable speed.
What factors relate directly to "Wobble?".
* Factors that might influence "Wobble".
When considering operating the sidecar straight (without turning) I don’t think any relationship exists regarding sidecar length or width of the sidecar. The weight of a sidecar might have some relation based on, assisting the wobble to be amplified by increased mass pushing on the bike.
Track would not influence “Wobble.” A track of 6 feet wide should go down the road just as straight as a track of 12" wide.
Lead would not influence “Wobble.” A lead of 6 feet should glide straight down the road just as well as a lead of zero, (like some older Harley rigs).
I believe that toe-in, and bike lean out, do influence "wobble" As the motorcycle wheels drive forward, the sidecar wheel tries to push the motorcycle wheel at an angle. (due to toe-in, and bike lean out) The rear motorcycle wheel is fixed (within the swing arm). The front motorcycle wheel is fixed as best possible in the grip of the rider's hands and arms. I believe it is this struggle that creates “wobble.” This would also validate why two different people can ride the same rig and have different opinions about how bad, or good, the "wobble" appears to be. The crown of different roads might also have some relevance.
* Factors that might influence "Wobble".
When considering operating the sidecar straight (without turning) I don't think any relationship exists to Motorcycle weight, wheel base, Rake, or tire diameter. I do however feel that the mechanical integrity of the steering bearings, swing arm bearings, tire pressure, and shock stiffness, are directly related.
Conclusion: Sidecar low speed wobble is an inherent factor of operation. The wobble is created by the need for sidecar toe-in adjustment, and bike lean-out adjustment, to facilitate sidecar operations in turns. Low speed wobble cannot be eliminated but it can be minimized. To reduce low speed wobble, one should concentrate on ensuring proper steering head bearing adjustment, tire pressure adjustment, condition of the swing arm bearings, stiff shocks, and proper sidecar toe-in bike lean-out. A steering damper should only be considered after all adjustments and maintenance checks are verified.
Also since this article was written I considered the width of the handlebars. This will have some effect. Narrow handlebars will need more strength from the rider to reduce the wobble and wider handlebars will need less strength.
The rider leaning forward or moving backwards on the seat also seems to make some difference.
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Interesting & the variations will be endless type of bike type of sidecar same situation applies to trikes I would think (only my opinion).
Good point. Yes, I have experienced this more with smaller trikes although I do have a Virago 1100 trike that has 2 steering dampers fitted. Makes me think it must have been bad!
I am a retired motorcycle and car engineering lecturer, wobble also can happen when the bike hits a different camber on the road, also the rake and trail, wrong tyres not at the correct psi/bar pressure, and headstock bearings are too loose there are a lot more things that could cause wobble, small bars, no weights on bars.
I believe you are correct! One or a combination of these points can truly make a significant difference. There are also instances where every possible solution has been attempted, except for a steering damper, and ultimately, it is the damper that renders the situation manageable. It may be the one thing you did not initially desire, but it could very well be the most effective solution. This then raises the question of whether it would have been easier to start with the damper, as it could potentially save the expenses associated with other attempted solutions.