TURBINE ENGINE PROGRESS REPORT #3
Our last turbine update was about 90 days ago so it’s probably time for some new information. There’s an old cliche that goes: “We finally got our arms around it,” meaning that we no fully apprehend what we’ve gotten ourselves into and we know how much time and money it will take to finish it.
Happily this is now the case for us with the turbine project. There have been quite a few sleepless nights, but those are finally over. We are only 60-90 days behind our original delivery target and that’s completely livable now that the unknowns are all behind us.
In our last update we commented on the three phases this project entailed. At this point we are right in the middle of the heavy duty machining of Phase 2, but we have also nearly completed parts C & D of Phase 3.
We have documented the turbine progress on a 40 minute video entitled: “Kerosene Fever” and it’s available now.
When you view this video and/or finish reading this update, you’ll better understand why we’re so excited about this turbine power plant and the upstairs help we’ve had which is making it possible for us to deliver them for the price we contracted.
The gear case cover plates are now machined and almost ready for assembly. The machining on both sides of this part was completed in duel set-up on one program.
Turbine output is 3050 RPM. We use AGMA 12 ground gears in this final reduction. These parts have a tailored, computer designed pressure angle which required special tools to generate. They roll through so smoothly you can’t tell they are engaged. These parts would be right at home in any Pratt & Whitney Turbine Engine.
In our last update the turbine wheel housings were shown all disassembled and stacked. They are now all fully re-machined and ready for assembly.
Surprise! A 20 amp direct drive alternator hides behind the main drive pulley. Our own magnets are bonded into the inside diameter of the pulley using specially designed production tooling. This alternator will fully recharge the ships battery within 20-25 minutes after the turbine starts and shill have two thirds of it’s power left for instruments and avionics.
Here we are preassembling the main casings without the planetary unit so that our quality control dimensional checking process can be completed prior to final assembly.
Our 30 hp HAAS Turning Center makes it fun to machine aluminum pulleys. It chewed through 125 cu. ft. of pulleys in a little over a week even counting setup time. You can see the chips flying in the photo.
The main casings have taken considerable effort to properly machine. When you’re dealing with many critical dimensions it takes considerable time to tune in all the cutting tools. The mating surfaces on these parts are narrow to save weight and programming the contour machining paths are also a time consuming process. The good news is that the parts are now running according to our original target cycle times.
An oblique view of the turbine which shows the oil scavenge pump and it’s plumbing. The main oil pump output goes directly into the filter (small canister shown) and from there into an oil cooler (during hot weather only) and from there into two gear case in-puts.
Dynamometer testing was a satisfying part of this project for us. Everything went very smoothly. The oil scavenge system and internal passageway porting worked perfectly. There is less than half a quart of oil in the casing at any given moment. Oil pressure throughout the system meets the original Solar design specs. We employed exactly the same type of belt drive and clutching system in the dyno as we have in the helicopter. It worked perfectly allowing the turbine to start up without exceeding 650 degrees F. the T.O.T. only goes up to 850 degrees F. at our 75 cruise hp.
A turbine engine is a very different animal, and it takes some getting use to. The good part is, the better you understand it, the more you come to like it.
This view of the engine shows the starter side. Our starting system is the feature of which we are probably most proud. The total starting system weight (battery & starter) is only 20 lbs.. The battery will start the turbine 4 times without re-charge and it charges fully in less than a half hour flight, while drawing only one third of the alternators output. This is a 12 volt system which is so much simpler and far less costly than a commercial 28 volt setup.