Eury
Elite Veteran
Location: Ankeny, IA, USA.
| Top Frame, tail transmissionI've moved on to the top frames, which includes installing the servos. I'm using JR 8301 servos, they won't be familiar to guys in the US, as they aren't sold here, but overseas they are a well regarded servo. Not too fast (.19 @ 4.8, .15 @ 6v), but extremely precise and smooth, great servos for FAI and sport, and light 3d, about what this gasser should be good for. The instructions show all of the servos installed from inside the frames, however, if the front 2 servos (pitch and ail) are installed inside, the linkages will have a pretty good angle to them, and the servo wires fouled on the frames. Installing them from the outside results in a straight shot to the bell cranks, and saves the wires.
 
The rear servo (elev) pretty much has to be installed inside the frames for the linkages to be straight. Installing from the outside and putting the balls on the inside of the horn is better, but it still results in a pretty extreme angle. This leaves us with the problem of the servo wire exit on the servo case being almost exactly in line with the opposite side frame. Not good. If I owned this heli, I'd trim the CF frame where pictured below to create the clearance I need. However, since I'm not sure I will buy it, I've left it as is. I've wrapped the wire completely with expandable sleeving, and the wire exit grommet is sitting on the frame. This is not a problem due to my servo choice, this servo is exactly the same size as a standard JR servo, with the wire exit in the same place, so any JR servo (and most likely any other brand) would have the same issue. Left the way it is, that wire will be worn through and shorted out in a short period of time, causing a crash. If I decide to fly this after building it, I may move the servo to the outside and put the balls on the inside to improve the geometry, but it won't be correct. The only way to make the rods have a straight shot that I can see is to install it per the instructions, and break out the dremel.
 
Moving on, the next assembly is the tail drive pulley and gear. As it came, this was already assembled, however, the gear was hard to turn, and there was a significant amount of play with the top gear on the shaft. Upon pulling it out, my first impression is that it's a nice solid assembly, but on further inspection, there's some issues here. First, the top bearing block appears to have the bearing recess machined off center (there's a picture, I'm not sure how apparent it is in the pic, but looking down at it, the bearing is off by a fraction of a MM.) It may be that the flange is machined wrong, or the whole block is, I don't know, but if it is off center, it explains one reason why the tail shaft was difficult to turn installed in the frame, but not on the bench, as it would never align and cause the friction. Next, if assembled as the instructions picture with the holes in the pulley facing up, the pulley fouls the top of the (mismachined) bearing block. The instructions show the shaft as having both a hole and a flat, however, the shaft I have only has a hole. if it had a flat, I could adjust the pulley up a touch to create the clearance it needs, however, seating the setscrew in the hole (actually a very nice way of doing it, it's extremely secure) locks the pulley into place. If I flip the pulley upside down and tighten the setscrew, it sits just a touch higher and moves freely, so that is how I assembled it. I have attached pics of the assembly along with the diagram from the instructions, and will be contacting QWW for their input on this issue and will report back.
   
Nick Crego
As I wind on down the road... |
