si {\bf j}. \\
% \nonumber {\bf p}_{{\rm R}/{\rm T}} &=& - b \cos \psi {\bf i} - b \sin \psi {\bf j}. \\
% \end{eqnarray}
% </p>
% <p>Position of axles</p>
% <p>
% \begin{eqnarray}
% \nonumber {\bf p}_{{\rm F}/{\rm O}} &=& {\bf p}_{{\rm F}/{\rm T}} + {\bf p}_{{\rm T}/{\rm O}} = \left( x + a \cos \psi \right) {\bf i} + \left( y + a \sin \psi \right) {\bf j}. \\
% \nonumber {\bf p}_{{\rm R}/{\rm O}} &=& {\bf p}_{{\rm F}/{\rm T}} + {\bf p}_{{\rm T}/{\rm O}} = \left( x - b \cos \psi \right) {\bf i} + \left( y -