frame thereby allowing the upper and lower drive wheels 6 and 5 to translate in a roughly vertical curvilinear path this arrangement allows for any inconsistency in the straightness and level of the horizontal drive rail 3 as the gate panel 1 fig1 translates horizontally along its path it should be noted that any number of substantially equivalent means of allowing the combination of drive wheels and motors to translate essentially vertically while still providing reaction to the horizontal force of moving the gate could be used the upper drive arm 7 and the lower drive arm 8 are held together with toggle clamp 17 and spring 18 this arrangement of the toggle clamp 17 and spring 18 provide a constant and predictable force that squeezes the upper drive wheel 6 and the toothed drive wheel 5 together thus supplying a normal force n between the upper drive wheel 6 and the horizontal drive rail 3 and between the toothed drive wheel 5 and the linear drive member 4 the toggle claim 17 and the spring 18 are coupled to the upper and lower drive arms 7 and 8 so as to effectively tie the upper drive wheel 6 to the lower toothed drive wheel 5 accordingly the drive wheels 6 and 5 will translate in unison.