up-feb8a.htm
Well, it's been a while since I updated this file. Over the last week I've added the upper halves of the vanes and started puttying them in. I've also started reinforcing the shroud because it was too flimsy. I picked up several small parts so I can start building the flight control surfaces. A muffler for the engine I borrowed would cost me about $50 (almost the price of a motor with muffler) so I asked my benefactor to see if he can find the tuned pipe he had been using for the engine. With domestic duties and other work things are running a bit slower than I had hoped.
I have no guesses as to my future progress rate. It's been too varied. Perhaps in 1-2 weeks I'll be doing tethered flight.
Again, it's been a while since I updated this. The latest delay has been because of domestic duties and lack of parts. Yesterday I bought a new engine complete with muffler (the engine I had borrowed required, but had no, pipe and I couldn't find one). Until I had a complete engine I couldn't mount it because it had to clock between the vanes. I also bought a Futaba 6XA transmitter system so I can start connecting that up. I also picked up a 12V starter and some extra props.
I've figured out a way to connect up the flight controls using aluminum tubing for the hinge barrel and a piano wire for the hinge pin. On the N-S and E-W controls the two will be clamped so they move together. On the rotator controls the near (to the servo) one will be driven directly one direction while the far one will be driven the opposite direction through the hinge pin.
Today I hope to run the engine to break it in and get familiar with it. The shopkeeper recommended that I keep the fuel tank just below the engine, which would require moving it. When I run the engine I'll find out just how low I can have it and still run the engine. If need be I can move the tank. I also hope to start attaching the flight control surfaces and servos. With luck I might even get started on the work stand that I'll need in the field.
Part of today will be taken up with domestic duties and a friend coming over to run his pulsejet. We got it started last week but within five seconds it got red hot and we didn't have it mounted properly to prevent fires. After almost setting my garage on fire, electrocuting myself, and partially melting the coating on my air hose, we quit for the night. Today he wants to build a more heat resistant run stand so we can verify the thrust levels and get more familiar with operating the engine.
Yesterday afternoon I clocked and mounted the engine so that the muffler points down between two vanes and the engine head is between two more. I built an engine run stand and mounted the engine so I test it. A friend recommended I perform a special break-in procedure (recommended for all new model airplane engines). He also loaned me some equipment for starting and operating the engine along with a book on breaking-in and maintaining engines. I intend to do this today and, hopefully, mount the flight control surfaces.
The same friend and I built a test stand for his Dynajet pulse-jet. We ran it twice for about 10-15 seconds and it ran well. Starting is still difficult but getting better. Based on a post-run calibration of his thrust cell (a fish scale) it appears that the engine was putting out about the advertised 4.5 lbf thrust. He's thinking of building a vertical flyer with it.
I've come up with a simplification to the flight controls. Instead of using a separate set of controls for rotation I can use the mixing feature of the transmitter and use two of the basic four for both lateral (coordinated) and rotational (asymetric) control. This eliminates two surfaces and makes the in-between vane attach points available for tether and strut attachments.
I've started mounting the flight control surfaces and ran the engine for about five minutes. It's still running very rich but is getting easier to start. A couple more days and I should have it broken in.
Continued to mount flight control surfaces. This is slow because the quick glue is not holding and I've had to go to wood glue. This means about a two hour delay between applications. Keeping everything aligned is tedius. Should have them all mounted by Saturday evening. Also set up the radio control to operate the flight controls as a v-tail and it works as advertised.
Spoke with some of the folks at work about breaking in the engine and mounting the fuel tank. I may have to move the tank higher to keep the fuel flow adequate. First I'll try adding a check valve between the muffler pressure tap and the tank. This will give me peak pressure in the tank rather than average.
The flight controls surfaces are nearing complete, possibly today. Next are the servos. Picked up some bright red satin for the emergency parachute.
Ran the engine twice. Either the tank will have to be moved upward or some other solution. There is just too much leaning out where it is currently located. The engine is starting easier and I'm getting used to it. A few more runs and it will be ready to put into the vehicle.
Ran the engine a couple more times. Had to buy a bigger starter, the one I had would not kick it over without a fight. Picked up a small fuel tank that can be mounted higher, though it will give me less flight time. Started mounting the servos in boxes and should start attaching the boxes and linkages tonight. Tomorrow I hope to pick up the fuel line check valves I ordered so I can see if they will pump the fuel higher.
This weekend I hope to build the tether rig, 8'x8'x8'. The first tethered flight should be next weekend.
Made good progress today. Attached a second servo to the vehicle and control rods. The rudders work as advertised. One control operates them together while another operates them differentially for rotation.