Abstract: A ground excavation shield that can include a first wall, a second wall, and a third wall, a first guide rail, and a second guide rail. The first wall can be disposed on a first side of the ground excavation shield. The second wall can be disposed on a second side of the ground excavation shield. The third wall can be disposed on a third side of the ground excavation shield and can be coupled to the first and second walls. The first guide rail can be coupled to a bottom of the first wall and the second guide rail can be coupled to a bottom of the second wall.

Abstract: A shaft driven trencher including a mobile powered base, a boom assembly, a chain digging assembly, a drive assembly and a linkage. The boom assembly includes a first boom member pivotally mounted to the base at a first pivot and a second boom member pivotally mounted to the first boom member. The chain digging assembly has a plurality of buckets. The drive assembly operably interconnects the mobile base and the chain digging assembly, with the drive assembly including a drive shaft connected to the mobile base for powered rotation of the drive shaft. The drive assembly further includes a right angle gear unit with input and output shafts, with the right angle gear unit being pivotally mounted to the boom assembly for rotation about the output shaft. The linkage interconnects the right angle gear unit with the base and pivots the right angle gear unit during rotation of the first boom member. The linkage also maintains the input shaft of the right angle gear unit facing the first pivot.