Friedlander-Keller Diagram

Overlay of normalized bow-string friction curve $R_b(v_{\Delta})/R_s$ with the bore ``load line'' $v_{\Delta}^{+}- v_{\Delta}$. The ``capture'' and ``break-away'' differential incoming velocity is denoted $v_{\Delta}^c$. Note that increasing the bow force increases $v_{\Delta}^c$ as well as enlarging the maximum force applied (at the peaks of the curve).

$$\begin{eqnarray*} \hbox{Applied Force} &=& \hbox{Friction Curve} \times \hbox{Di... ...} &=& \hbox{String Wave Impedance} \times \hbox{Velocity Change} \end{eqnarray*}$$

• Nominally, $R_b(v_{\Delta})$ is constant for $\vert v_{\Delta}\vert\leq v_{\Delta}^c$, where $v_{\Delta}^c$ is both the capture and break-away differential velocity. (static coeff. of friction)
• For $\vert v_{\Delta}\vert>v_{\Delta}^c$, $R_b(v_{\Delta})$ falls quickly to a low dynamic coefficient of friction
• Dynamic coefficient decreases with differential velocity