the aligned lower bottom castle lock slots 69 a rotation of the locked top castle lock 64 and the upper bottom castle lock 67 a under these circumstances facilitates rotation of the first sun gear 49 due to the splined connection with the corresponding splined shaft 58 lying alongside the first sun gear 49 and engaging the thrust bearing mount 59 fig1 referring now to fig9 and 17 of the drawings the planetary pinion gear assembly 70 illustrated in fig9 is designed to effect speed reduction in the 360 degree rotation of the bent section 41 and is further characterized by three sets of stacked pinion gears 71 each stack of which is individually mounted on a pinion gear shaft 72 the top array of pinion gears 71 engages the gear housing 37 at the gear housing teeth 37 a and the first sun gear 49 as illustrated in fig9 such that the top array of pinion gears 71 are rotated in concert with the rotation of the first sun gear 49 the second or middle array of pinion gears 71 also engage the ring gear or gear housing 37 at the gear housing teeth 37 a as well as a second sun gear 73 while the third and bottom array of pinion gears 71 engage the gear housing 37 at the gear housing teeth 37 a and a third sun gear 74 fig9 the third or bottom set of pinion gears 71.