Unmanned Systems Technology 009 | Ocean Aero Submaran S10 | Simulation and testing | Farnborough report | 3W-110xi b2 TS HFE FI | USVs | Data storage | Eurosatory/UGS 2016 report

57 3W-110xi b2 TS HFE FI | Dossier oil system. Regardless of fuel type, 2% lubricant is added to it, a fully synthetic blend, and 0.1% of a diesel engine valve cleaner, which has the effect in this application of extending the life of the spark plugs. The main case carries a pair of bearings flanking the crankpins/throws section, then there is a bearing at the end of the snout section and another in the generator housing section. The bearing in the generator housing is located close behind its neighbouring main bearing and has the effect of reducing run-out of the shaft, which in turn assists generator life. The crankshaft is made of five pieces: the central throw, the two pins and the two outer sections, which integrate counterbalanced throws with the respective section of shaft. The pins connect the centre throw with the outer throws, each pin passing right through the adjacent throws and the assembly pressed together with a device that generates a pressure of 10 t. First the two pins are pressed into the centre throw, then the ends are pressed on in turn, the entire assembly then being connected only by the interference fit. The journals of the forged steel crankshaft are nitrided, as are both ends of the shaft, aside from a threaded portion at each extremity (to avoid cracking); the journals are superfinished. Each con rod is one-piece, fitted at the crankshaft assembly stage. An I-section forged steel production, it runs in needle roller bearings at both big and little ends. Holes drilled through the big- and little- end enclosures allow lubricant to reach the needles. The piston pin is steel. Superfinished, it runs directly in the piston pin bores, which are likewise superfinished. It is retained by simple C-type clips, which call for a complex design of piston groove to allow installation and removal but avoid the need for ears. Ears, Wintrich notes, can represent a point of failure. The piston is cast aluminium alloy. Wintrich recounts that 3W has tested more costly forged pistons, to no advantage. It has even tested a carbon composite piston, “which cost more but showed no advantage; for example it didn’t reduce vibration. Also, it was brittle at the corners and that made assembly very tricky”. 3W pistons originally had a lead skirt and crown coating, but in view of environmental concerns that has been changed to zinc. The zinc coating does not encompass the pin bores but it does embrace the single ring groove. Schudt reports that 3W does not use a second piston ring unless the cylinder bore is 49 mm or greater (that of the 110xi is 45 mm). The single steel, square-edged, flat- faced ring is uncoated, and it runs in an uncoated bore in the linerless aluminium cylinder. Schudt says barrel-faced rings are used only for larger cylinder displacements. Unmanned Systems Technology | August/September 2016 Crankshaft of the 110xib2 TS HFE FI 3W’s110xib2 TS HFE FI uses a single ring piston