Yet another math question

[Dave Bagwill]

Maybe it's a physics question, actually.

I've been thinking about the difference between the straight downward force from a movable bridge versus the torque load on a fixed bridge. (The Khan Academy - that free online set of courses on every subject - had some good info on torque, so I've gotten a better handle on the concept.)

Downward force, measured in psi, is not difficult to calculate or measure. Torque, not so much.
The basic torque computation is of course the combined pulling pressure of the strings, perpendicular to the bridge, multiplied by the height of the strings off the top of the guitar at the saddle. No, actually it is the length of the level, perpendicular to the bridge, times the height of the strings at the saddle.

My question: how to figure, for a given torque, the straight downward force in psi? For my testing jig to work, the downward force is what is needed, not the twisting parameter.

Are you aware of any method of correlation between torque and downward force in psi?

Maybe I'm overthinking it. That's why I'm putting out this SOS to you. :-)

[Dave Bagwill]

I meant the length of the 'lever', not the 'level'.

[Herman]

Depending or what you think is `the downforce` to the top.
On the front of the bridge you have a down direction of the force, at the back side of the bridge you find a pulling force.
Both depending on the size of the bridge (front vs backside from the saddle)
On the saddle there is downward force. The ballends of the strings cause a pulling force, in fact causing compensation to downforce of the saddle.


but Dave, WHAT ARE YOU SEARCHING FOR???
Herman

[Dave Bagwill]

Here's the hyperlink to the address in the picture -
http://www.juststrings.com/dad-ej10.htm ... escription

[Dave Bagwill]

BTW - this set comes out to 183.5 lbs of tension!!

http://www.juststrings.com/dad-ej12.htm ... escription

[Herman]

Dave, If the stringtension is exactly parallel to the top, then there is no downforce to the top in your graph. Just torque. Sorry.
Herman

EDIT: WRONG, forget this.

[Dave Bagwill]

I'm not sure that you are correct Herman, but maybe I just don't know enough. I'm reading a long paper by al Carruth on this now and will get back.

Also, here is a long discussion of related issues: http://theunofficialmartinguitarforum.y ... cEoy7XLLVQ

edit: Herman, I see what you are saying - yes, it is torque, a rotational force. However, it appears that that force has three components, a vertical, a horizontal, and an angular. I'm interested in the vertical.