Originally Posted by
Veritas44
"Head-Shake" (Steering Wobble, etc... whatever you wanna "name" it) is caused by or greatly exacerbated by the newly reformed Unit having Geometry Issues.
*when and if all other possible causes have been checked and eliminated as Causes-see the "*" below
With the Front end being the simplest, the lightest, non-powered and driven by the Powered end, and most importantly it is acting as the "Rudder" for the Unit, that is where the Results/Effects of the Geometric Shortcomings will manifest and be noticed.
What has been added to the Unit (Trike/Side Car/etc.) and its inherent Designs and how they interact/affect the existing Geometry (which was correct for the original Unit prior to mod) will determine the extent and extreme of the Issues manifestation. In this Case and discussion-The dreaded Head-Shake or Wobble. When you change the Rear and do not change the Front to match those modifications-You get Problems. Going from a Linear Unit to a Triangular (whether symmetrical Trike or asymmetrical Sidecar) one without changing the singular front point leaves the Unit in conflict with itself. Thus the "Twitch" (or mechanical "seizures" depending on how bad out-a-whack the new Unit is) as it battles itself trying to accommodate the new Forces affecting the Triangle set in motion.
In most cases, correcting/modifying the Front Geometry with a Corrected set of Triple Trees (aka "Rake Kit") will eliminate or danged near get rid of the Issue's (or the possibility thereof if done initially) manifestation by bringing the new Unit's overall geometric Dynamic inline and in concert with the Rear changes/additions. The "Wobble" can still occur every now and then when that weakest or most prone to the Effects (the Front) encounters a shock like hitting bumps, potholes, etc.
But for the most part, unless pretty severe instances, it should not and when it does the Effects should subside quickly enough as to be negligible.
IF it does not, the Geometry is still out of whack even with the Front being "mated" to the Rear as close as humanly/mechanically possible.
THEN the only thing left to do is deal with the Effects as the Cause cannot be truly eliminated.
There are some Units where this is unavoidable due to the Design shortcomings and/or the original Unit at the core not being well suited for the conversion/modification performed upon it.
'Nuff said and I won't go into that any deeper.
When the later of the above is the case the only way to best address the Issue is the addition of the Steering Damper. This is most common (about 50% of the time) in Sidecar Rigs. However, it does occur in Trikes in some situations as well.
Some more usual than others-Some very rarely if at all. Again, Nuff said bout that.
A Steering Damper is nothing more than a horizontal "shock absorber" mounted to the point of manifestation and the most solid and non-moving/static point of the Unit. Think of it as a hydraulic closing Arm on a Storm Door. That's pretty much all it is. This Damper assumes/absorbs the Forces that are inflicted upon the Front that cause the Shake/Wobble/Twitch/Seizure so they are not felt or translated on up through the Front Assembly. In this Case-The Bars and the Steering.
The Down-side or "Con" to the Steering Damper (most times when Treating Effects as opposed to solving Causes we normally get equal or worse ramifications) is that once in place, the Damper is constantly working and therefore acting at all times against the Steering/Front Assembly. In a Trike/Sidecar situation where the Bars are being pushed and pulled the Damper is always being employed as well.
This makes ALL Steering more difficult by requiring more physical input to accomplish the Steering. So, in treating the Wobble Effects of the incorrect Geometry we are also creating new Cause(s) of other Issues.
Due to the above, when evaluating the situation and deciding on Steering Damper Yes or No; you really need to weigh the Pros & Cons against the level or severity of the Need carefully.
Such as: Is it only at low speed (15-18 mph speed only)? high speed (from 45-65 mph)? All speeds?
What "window" of occurance? 3-5 mph or a 20 mph window?
Only when encountering bumps, divots, obstacles? Go away quickly or last and or increase in severity?
and so on...
*One thing to be sure is that all other Courses of Action have been checked, addressed, and implemented first. As others have already said,,,,
Check Head-Nut Torque (go a tad above "Norm" but careful not to over-tighten and become unsafe)
Check Wheel Bearings, Tire Balance and psi.
Seriously consider modified Triple Trees if not already installed or if so they may not be the correct Angle for your Unit (no "Cookie-Cutter" "One Size Fits All" angle correction for all Bikes or Trike Brands). This possible Solution also has other Positive Effects not Wobble related and well worth it.
Several more that have been discussed here and elsewhere just about as often as Tires and mounting Orientations.
Lots to consider and think about.
In the end,,,,
It Does NOT occur in All Trikes or Units.
It Does NOT always "need" to be corrected/addressed.
Steering Dampers are NOT a Panacea or End-All.