Unmanned Systems Technology 023 I Milrem Multiscope I Wireless charging I Logistics insight I InterGeo, CUAV London & USA show reports I VideoRay Defender I OS Engines GR400U-FI I Ultrabeam Hydrographic Ultra-2 I IMUs

66 The propeller is attached to a drive hub at the front of the crankshaft. Drive is transferred by fastening a locknut to the drive hub, which tightens against a washer on the outside and a thrust washer on the inside. The generator is belt-driven from a toothed pulley behind the propeller drive hub, while a rotation sensor is fitted immediately behind it, located on the crankshaft by a woodruff key. At the rear of the crankshaft is a reverse-threaded crank pin stop screw that retains the con rod big end. The con rod is one-piece aluminium alloy with a roller bearing big end, a bushed little end and a rectangular section shaft. The con rod length (eye to eye) is 51.3 mm. An uncoated steel piston pin runs directly in the small end and directly in its piston bores with a round wire circlip retainer on one side and a Teflon pad on the other. The hollow pin is 28 mm long and 9 mm in diameter. The piston is of the window type and has a flat crown. It is machined from aluminium alloy and is uncoated. It carries a single barrel-faced steel ring, which has a radial height of 1.7 mm. The two valves are upright while the combustion chamber is of the bath tub type. The single spark plug enters the chamber between the valves, to one side of the chamber. The compression ratio is 9.9:1. The valve head diameters are 16.8 mm intake and 15 mm exhaust. The intake and exhaust valves both have a lift of 4 mm. The intake port takes the charge through 90 º from the rear-located entrance to the head to the valve seat area. It is designed to promote swirl of the incoming charge. The throttle body is attached to the cylinder head through an intake manifold that turns the charge through 90 º , allowing the throttle bore to be vertical. The throttle body is in turn fed by a horizontal side-facing velocity stack from which the charge is turned 90 º into it. The throttle body carries a butterfly- type throttle. The single solenoid-type injector is located in the intake manifold downstream of the throttle body. The throttle is operated by a servo located towards the base of the unit between the front and rear mounting plates, with a linkage up to the throttle body. The servo is in turn controlled either by the autopilot or PMW signals from a radio control unit, via the ECU. The exhaust port takes the exhaust gas through 90 º from the valve seat area to the exhaust exit on the side of the cylinder head. The exhaust header is attached to the head with a metal gasket at the interface, and in turn the silencer is attached to the header. Both valves are solid steel, heat treated and uncoated. There is a valve seat only on the exhaust side – uncoated, the material used for the seat is undisclosed, as is the material used for the valve guides. Also undisclosed is the material December/January 2019 | Unmanned Systems Technology OS Engines produces its own fuel pump for the GF40U-FI OS Engines GF40U-FI UAV four-stroke Single cylinder 40 mm (1.574 in) x 31.8 mm (1.251 in) = 39.96 cc (2.438 cu in) Naturally aspirated Unleaded gasoline fuel Aluminium cylinder Liner of undisclosed material Two main bearings, roller Steel crankshaft, one pin Aluminium con rod Light alloy piston, one ring Pushrod; gear-driven camshaft Two valves/cylinder, one plug Upright valves 16.8 mm intake valve, 15 mm exhaust Electronic ignition Port injection Engine management system 9.9:1 compression ratio Maximum rpm, 9000 Data sheet