Aant Farm TPR72 | Dossier gear tooth passing frequency on the left bull gear (the larger of the two spur gears; the pinion is the other, smaller spur gear). The gearbox is a wet-sump design, meaning that the oil is contained in the gearbox housing rather than in a separate oil tank. A 2 gallons/minute gerotor oil pump is driven by one of the layshaft gears and delivers oil to the engine through a standard 3-micron filter element. “All the gearbox bearings are COTS,” Seegers says. “The axial turbine shaft runs in a pair of its own high-speed, ceramichybrid spindle bearings, and there are six more bearings inside the gearbox – two for each of the two layshafts – and a pair for the output propeller shaft. The propeller shaft runs on tapered roller bearings so that it can take the 1P cyclic loading and gyroscopic loads the propeller generates “They’re cheaper than the ceramic bearings, and they’re beefier too,” Seegers says. “Also, the layshaft bearings are radial contact bearings. Like the roller bearings they’re not high-speed, so they’re not expensive.” The oil pumps were built to Aant Farm’s specification by WireTech, a wire EDM company in Arizona. As Aant Farm wanted full integration of the pump into the gearbox, the TPR72’s pump has no COTS elements; the entire pump has been fabricated for this one application and is designed to integrate specifically into the space internal to the gearbox. “Lastly, the gearbox housing is machined as two halves, also out of aluminium billet, but as it has no non-line-of-sight parts, no brazing is needed. Again, we’ll probably switch to investment castings for series production, as it could save $400-500 per unit,” Seegers adds. Future plans Aant Farm anticipates developing an upscaled version of the TPR72 as a replacement for general aviation piston engines running on 100 octane low-lead gasoline. In the process of upscaling, it is likely that some consolidation will be done to reduce the parts count. “We’ve seen what some successful aviation turbine engine companies are doing out there, and also what is happening in general aviation, with 100 octane low-lead gasoline having a questionable future,” Seegers comments. “A 224 kW Jet-fuel burning diesel like the Continental CD300 weighs 264 kg. The Rolls Royce 300 turbine has the same maximum power rating but weighs 91 kg. That’s a difference of 173 kg, which is weight you can’t burn off, reduces payload capacity, and adds to landing loads. “We therefore think there is a market for a powerplant somewhere under 224 kW for OEM and retrofit aircraft. There are microturbines with more power than the TPR72, but given where the UAS industry and general aviation seems to be going, we might try to leapfrog the competition,” Seegers says. “All commercial aviation and light aircraft OEMs are going to find 100 octane low-lead gasoline becoming rarer and more expensive, so a heavy-fuel engine like ours with low cost over lifetime could fill a huge gap across uncrewed and crewed aircraft fleets alike.” Not enough hours in the day? Use your time effectively with a targeted, dedicated, online portal, solely for the recruitment of uncrewed & autonomous engineers. Contact teddy@uncrewedengineeringjobs.com for more information on our 1x, 5x, 10x & unlimited job packages. TPR72 Turboprop Heat recuperator Fuels: JP-4, JP-8, Jet-A, Jet-A1 (JP-5 and diesel yet to be tested) Total weight: 30 kg Maximum power output: 77 kW total (72 kW at propeller, 5 kW at alternator) Maximum prop speed: 3410 rpm Attitude limits: ±45o pitch, ±30o roll Flight ceiling: to be confirmed; 25,000 ft expected TBO: 3000 hours expected Some key suppliers Oil pumps: WireTech Alloys: High Temp Metals Investment castings: Bescast Brazing: Joined Alloys Machined titanium: Metalcraft Manufacturing and IP services: Redline Turbine Systems Microtube welding: Mezzo Technologies Specifications
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