in the opposite direction i e clockwise because it is fixed to shaft 116 drive wheel 62 rotates as does the shaft 116 thus merely by changing the engagement of first gear 118 cleaner 34 may be caused to change its direction of travel from forward to reverse or vice versa in fig4 first gear 118 is shown as not engaging either second gear 126 or third gear 130 u2014 in essence in a neutral position in which drive wheel 62 is not rotating however boss 134 which surrounds shaft 116 may pivot about shaft 138 so as to translate shaft 116 to its left or right in turn causing first gear 118 to engage either second gear 126 or third gear 130 if boss 134 pivots to the left of fig4 first gear 118 engages second gear 126 pivoting of boss 134 to the right of fig4 causes first gear 118 to engage third gear 130 a cam and gearing assembly 142 may be used to cause boss 134 to pivot either left or right about shaft 138 moreover because two motive assemblies 46 preferably are used for a cleaner 34 one on each side of body 30 as mentioned earlier their cam and gearing assemblies 142 may differ somewhat consequently motion direction speed or both of one drive wheel 62 may differ at times from motion of the other drive wheel causing cleaner 34 to move in non linear manner fig9 12 illustrate alternate inlet 26 u2032.