Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

60 Dossier | Briggs & Stratton Vanguard EFI/ETC vee twins to follow in the future – as well as in boats operating in shallow waters during near- shore hydrographic survey work. “We want all our engines to keep running regardless of how people use them, so we’ve always targeted durability of performance,” Bruener adds. “For example, some European users running unmanned mowers with these engines are operating on really steep hillsides for long stretches of time, but by replacing carburation with EFI, we can maintain fuel delivery and smooth operation.” Most recently, humanitarian aid delivery organisation Windracers has integrated two of the 23 bhp EFI engines into its Ultra UAV, which is currently in development for fire mitigation services as well as aerial aid delivery. The engines provide the desired power to carry a payload capacity of up to 100 kg over a 1000 km range. The Small Block EFI engine weighs 35 kg and fits into a 449 x 407 x 318 mm space. It operates up to a redline of 4200 rpm and has a standard idle speed of 1100 rpm. The Vanguard Big Block EFI engine “The design of the original, carburetted Big Block engine started around 2004, as part of a plan to supply an engine that leveraged the Small Block’s vee- twin design and durability but provided more horsepower,” says David Duch, Briggs & Stratton staff engineer. “That led to the development of a 993 cc air- cooled vee twin designed for use on turf management equipment and a variety of other utility applications.” The Big Block achieves its rating while running at 3600 rpm, although Briggs & Stratton engineers add that it can produce more than that when run at speeds of up to 4600 rpm. Brian Brunelli, senior manager, engineering, notes that about 10,000 hours of internal testing have been accumulated across the two engines, with a 1500-hour full-load test (at 3600 rpm) being the typical final trial carried out before they are sent out to customers, as well as a peak torque test (below 3600 rpm but still at full load) which is sometimes run for 1000 hours. “We have tens of thousands of hours of data on them, given the extra testing we’ve done on their different variants, including some on-site trials in both freezing and very hot conditions where we’ve run the engines for extended periods without issue,” he adds. In general, both engines follow the same design philosophy and use similar parts and processes, but they differ in some respects. Electronic management and control systems As mentioned, Briggs & Stratton’s initial EFI/ETC system originated from a request by Rosenbauer to use it in a fire brigade generator using the Small Block vee twin. “The output of that engine stayed at roughly the same level as before, but once our ECU and EFI had been integrated the load acceptance and reaction time were greatly improved from the previous carburetted, mechanically governed version, with additional improvements in fuel efficiency,” explains Gerhard Ihrig, the application manager of Briggs & Stratton’s Power Application Centre in Germany. “That engine also needed to be able to start even if a battery was dead or had become disconnected, so we designed it with a flywheel-mounted alternator and electronic magneto-based ignition.” Both fuel injection and throttle control are governed by the ECU, with unique configurations and suppliers used for the Small and Big Block versions. For the Small Block, the ECU was originally developed by Japanese company Kokusan-Denki (now part of Mahle) in partnership with Briggs & Stratton. Data on the engine’s operations, such as temperature, oil pressure and so on, is accessible by plugging directly into it via computer. Robert Pomeroy, senior product manager for utility engines at Briggs & Stratton, adds, “An advantage of our long history of making and supporting our engines is that we have dealers and distributors all over the world. At those dealers, Briggs & Stratton technicians April/May 2021 | Unmanned Systems Technology The Big Block version’s throttle body and EFI/ETC assembly has an integrated design for reducing the wires and connectors needed for the electronics