as may best be seen in fig1 includes a housing h that has a forwardly disposed flange 34 that is secured to the web 30 by bolts 36 or other conventional means the housing h has a second electric motor j disposed therein which motor has a drive shaft 38 projecting forwardly therefrom and the drive shaft having a first gear 40 secured thereto as may be seen in fig1 the first gear 40 is located in a cavity 42 that is formed in the web 30 the first gear 40 is in toothed engagement with second and third gears 44 and 46 the second gear 44 is connected to a rearwardly disposed end of a first tubular sleeve 48 and the second gear 46 is likewise secured to a second tubular sleeve 50 as shown in fig1 the first and second tubular sleeves 48 and 50 are rotatably supported by bearings 52 and 54 located in transversely spaced first and second bores 56 and 58 formed in the web 30 the forwardly disposed end portions of the sleeves are in the form of enlarged heads as may be seen in fig1 that serve as thrust bearings and have first and second set screws 60 and 62 mounted therein for reasons that will.