Blackhawk build part 2
After a long break from this model, I am finally back in the saddle. Tam has made me some exhausts pipes and that was what stopped work last year, but I have to confess the pipes arrived just after my trip to England in September. Now its time to use them and get this bird in the air for a test flight.
The first thing we need is one of these
I called on a couple of friends here. Firstly David, AKA redneckteddy, provided some very nice CF offcuts which made up the mounts for the fuel pump and control valves.
And another very good friend arranged a Dx9 receiver. I am going to fit the 2 external antennas to the fuselage so that the actual antennas are by the windows. The fuselage is CF and I am not sure 2.4GHz will go through CF so I am not taking any chances.
The turbine has been fitted with the Orbit Kerostart system and I will be powering it with a small LiPo. Its against my better judgement but the alternative of 10 very large nicads doesn't appeal so a 2.1AH LiPo it is. It will be fixed so it can be removed for charging. I did consider A123's but I think 4 will be too much and 3 not enough.
I made up some pushrods from 3mm rods by turning the ends down so they are exactly the right length and then threading them 2.5mm.
The pitch curve has been set up at -3, 5, 9 and its easier to do this out of the fuse. Now to mount the mechanics and look at the fuel tank situation. I also have to figure out the drive coupling between the turbine and the tail boom shaft and I am waiting for a 502 gyro to come from England and then we can see if this baby flies. I prefer the 502 to the 401 as it has a display and I can see what the gyro is doing rather than try and interpret what the Tx is trying to tell it to do, however, there are none I can find in the US.
Starting to look real
The next task was to connect the turbine output to the tail drive system. I made up this shaft. It has machined down Vario couplers on each end mounted into some 1/4" thick wall stainless steel tubing. The center bearing was from a Robbe Cuatro and was partly machined down so it could be mounted into a bulkhead. The brass sleeve was made so it could be slid into the bearing only so far and was a smooth fit on the shaft. One of the last jobs will be to add a drop of green loctitie to the sleeve to hold it in place on the shaft
Then I made up a piece of wood to support the center bearing and PFM'd it and the bearing in place.
The top support brackets shown in the instructions weren't in my kit and a quick e-mail to mario showed they weren't supposed to be! I had to make my own. I looked at the way he had done his and they looked very nice, but they went to the center of the door opening where there wasn't much strength. Having had my share of resonant fuses I decided to make some which would fit to the strongest point and that was where the undercarriage is mounted. Surprisingly this took a lot of thinking about and a whole day to make 2 brackets.
I will need to make up a similar brace to go across the back of the mechanics but that should be a lot easier.
If I make it big enough, it will act as a heat shield and I will be able to mount the gyro sensor on it.