oid wrote: ↑Wed Nov 21, 2018 2:57 am
Increasing the height of the bridge actually decreases mechanical advantage and unbalances the system. We get the greatest mechanical advantage with the force applied at 90 degrees to the lever, the strings are the load, not part of the lever, with the spring being the load on the other side of the teeter totter. The arm of the lever the strings act upon is perpendicular to our guitars top, so for optimum mechanical advantage we would want the strings parallel to the top of the guitar, but that is not practical, we need some down force on the bridge so we accept less than perfect and dick around with the spring tension to get us as close to balanced as we can get. Increasing the height still could help, if the trem is not sitting on the pivot properly, a little upward pull from the strings may help get it seated and keep it there. Giving the part the strings anchor on a push downward or pulling up on it can solve this issue as well, it is not hard to knock the trem out of alignment with the pivot, especially when there is no string tension to balance out the spring.
The above graphic does not show the pivot at all correctly.
If you look at this one you can see the trem rests on the corner of the pivot, not the face and there is an area with a sharp bend in the tremolo that the pivot sits against. If the pivot is moved off this spot we get issues, we have unbalanced the teeter totter. Push the string end of the trem into the body and now the spring has a longer lever and more mechanical advantage pushing the front of the trem up, along with the collet, pull it out and the opposite, the front and collet dives under. Sometimes the point the pivot bears against is less than perfect and it can get knocked out very easily, sometimes the pivot wears and becomes rounded, same result and sometimes either the pivot or the bend is wrong and it never works correctly. The design of the tremolo means we can not actually pull it out to far, the curve beneath the pivot and the load will pop it back, but we can push it in and out of align. It is a complex little system.
You've got me thinking more on the mechanical advantage. But based on the usually
downward angle of the lever arm (the part that extends above the body) to the pivot, the
ideal string angle (for 90deg pull) would be down into the body, not parallel to it, ie even more impractical. Pushing down on the trem will take the lever-to-string angle even further from the ideal 90degs. Pulling up on it gets it closer to the ideal 90deg pull. So pure mechanical advantage in terms of leverage varies through the trems range, as does string tension, thus changing the balance.
The effect of the string tension is twofold: (1) to exert a torque (dependent on angle of pull) on the trem around the pivot (balanced by the spring), and (2) to exert compressive force on the pivot, increasing friction somewhat.
You are right about the pivot edge drawings from that website. The best pics I've seen of how it
should be are figure 4a in Leo's original patent (if you look very closely) and this pic of the Mastery trem's pivot .. and now your drawing.
The end of the plate is not square, as it is only supposed to ever pivot on the upper edge, which is deliberately favoured in the angled way the plate edge is cut (on the better trems) ...
http://www.offsetguitars.com/forums/vie ... t#p1507248
"I just knew I wanted to make a sound that was the complete opposite of a Les Paul, and that’s pretty much a Jaguar." Rowland S. Howard.