RAK402
Veteran
Location: Alhambra, CA
| I assume that you are referring to the GMP Cobra, as opposed to the Schluter, or Kalt Cobras?
If GMP or Hirobo:
1) CG balance the blades (spanwise CG and total weight should be identical).
2)There are two needle bearings pressed into the yoke, that are (very frequently) not pressed in equally, causing the yoke to be off center. There should also be a very thin washer on each side between the bearing and the hub. Press the bearings back and forth until the gap between the yoke and the hub is identical on each side.
3)Make sure that the steel pin that for the needle bearins mentioned above is straight and smooth, and that the set screw that retains it in the hub is tight.
4)Make sure the two long pushrods which go from the swashplate to the bell/hiller mixers on the head are identical in length. All pitch changes for tracking, etc. should be made on the short links between the mixers and the blades, or differential through will be encountered.
%Balance the flybar.
6)Replace the damper. Vary the tightness of the damper. The damper is a piece of fairly soft, thick walled rubber tubing retained by the bolt and two collars under the pin mentioned above. Adjustment is made by tightening/loosening the bolt. It is a good idea to use a locknut against the threaded collor to keep the bolt from loosening (if the bolt backs out in flight, you will have a free flapping head and a fairly spectacular tail boom stike).
7)The heads on these machines, if not damaged by crash, etc. run extremely true. Make sure that the yoke is not bent. Check the blade grips as well (they are cast, and fairly resistant to damage.
That is all I can think of, at the moment. |
Looking for tips making Cobra fly better and less vibration. Thanks
