TURBINE ENGINE PROGRESS REPORT #2
Interest in the turbine installation continues to climb, especially since our latest ads have been updated to point out that the HELICYCLE© is turbine powered.
In our last update the generator sets had just arrived at our plant. At this point they are completely disassembled, coded and almost through the decarbonization and sterile clean up required for proper N.D.T. processes. This project has been organized into three phases:
Design work and building tooling
Disassemble power plants
Order all long term lead time components
Inspect all critical components
Balance turbine assemblies
Assemble turbine section
Assemble gear box section\
Mate and test (dyno & otherwise)
Complete options and other peripheral items. (i.e. clutch, engine mounts, pulleys, etc.)
We have now completed phase 1, and as you can see from the photos are hard at work on phase 2.
Other than the design work the most time consuming portion of the work completed to date has been getting the match plates for the casting family completed. We cast the first parts at our facility in our own furnace to speed up the turn around process. The photos show machining on these parts while we are waiting to receive production parts from the foundry.
If everything goes according to schedule and it looks good at present we will have production castings by the time all programing and machining is completed on the first set of parts. These parts will be assembled the end of January into Eagles HELICYCLE. (The engine will be dynoed prior to installation.)
It’s interesting to talk with the wide spectrum of folks who are now calling in after seeing our ads and visiting our web site. In the good old Scorpion and Exec days, we seemed to attract a lot more folks who were pretty uninitiated to aviation. Now, we’re talking to many more rated fixed wing and helicopter pilots who don’t need much more education before they’re ready to buy. This makes our job so much easier and we love it.
If you’re reading this on our web site for the first time, please don’t feel we don’t want you to call, we are happy to talk with anyone who has taken the trouble to read this far.
A family of seven match plate patterns are needed to produce the turbine and drive train components. The gear box patterns were designed to be cast with out using cores, which helps to dramatically lower casting costs.
The air set molds for the gear casings weighed over 400 lbs. This made it difficult to set the copes by hand and still achieve the precise registration necessary for even wall thickness. I believe the good Lord helped us with this because all four big casings came out perfectly. (Our production foundry has special equipment to deal with these heavier molds.)
This is a cope side view of the casings just after mold shake out. The gating, risers and down sprue are visible. Exothermic sleeves are used in the risers to feed molten metal to the heavier sections of the casting for as long as possible. By so doing, the shrink problem is throughly dealt with. We previously described why these casings are so much lighter and still very strong. In fact, had we more time to spend on the patterns, we could have lightened them even more.
This is a view of the turbine exhaust and the radius segment by itself. Every commercial turbine exhaust you see has beautiful flowing bends. When we got around to the design of this part, we simply couldn’t bring ourselves to lower our sights to conventional segmented and welded bends. This meant that a special male and female die had to be produced to make this radius. The segment shown still needs to be trimmed prior to welding together with its mating half.
Cleaning and de-carburizing to sterile conditions is vital if N.D.T. processing is to be successful. We use a cleaning solution which you definitely do not want to stick your bare finger into for long.
A small booth serves as a dark room where parts are inspected with a black light. The chemicals which are used to prepare the parts for inspection require several immersion and drying sequences, before the part is ready to be viewed. The lighting unit shown here may look quite large, however it has an internal fan installed to keep it cool since it stays on all day long.
At 60,000 rpm, balance is super critical. In the good old days when we balanced crank shafts and rods, a tolerance of 5 grams was about as close as necessary. The piece of equipment shown here is capable of reading an imbalance of less than one half of one tenth of one gram. This weight is measured in bees wax. It works out to a tiny spit ball sized BB which is placed at a 1" radius on the part being balanced. (The part is not left with this imbalance, this is just the tolerated imbalance amount.) The part is actually balanced in two planes to this precise tolerance.
The turbine and shaft assembly are held in two special fixtures we had to build ourselves. The one holding the shaft is clearly visible, the other one which centers the turbine and compressor separator is not. We are quite happy to be through this part of the work as it was a pretty fussy task.
The compressor housings have had the diffusers removed and the cavity re-machined to the mil. spec. This part goes on a 4th axis fixture later to have additional weight removed and mounting holes drilled.
The gear box out put shaft starts out as a 15 lb. chunk of metal over 6" long. When a fork lift drops off three twenty foot long steel telephone poles like these on your shop floor, you know you’ve got some big work ahead. Just sawing up the slugs for these parts wears out several high quality band saw blades. Eventually we will have a forging die made for this part. There was no time or money available for it this first time around.
Our turning center peels off 3.5 lbs of chips per minute. The 30 hp motor is loaded to 75% capacity and the Valenite cutting insert is maxed out to 20 minutes into the cut. This does not mean 20 minutes per part. This insert cuts through several parts for a total of 20 minutes of cutting time before its used up. Chips hitting the inside of the machines water proof casing make it sound like you’re in a major hail storm.
A view of the target fixtures and tools used in the green machining process (first operation) on the front and rear casings. The target fixtures index the parts to a triangulated position. The accuracy of this process is such that when the two case halves are final assembled with shafts and bearings, the axial play from bearing to bearing meets the bearing manufacturers specs. Dowel pin alignment fixes the exact location.
Modern technology is wonderful, however when a part gets to fly, special handling is required. Aerospace parts are said to be “shop worn” before they even get assembled. This is due to the many times they seem to get touched by human hands during processing.
A face mill starts the machining process on the front casing. Its path is mirror imaged to the rear casing flange.