Hello all, I need a bit of help with an N5C Belt Driven Tail, Flybarless.
It has a Demon 3SX, OS SHX Hyper (blue head). Bought used of course, finally got it together started flying it and breaking in the engine, leaning it out, getting the headspeed up. First session went fairly normal, engine was rich so a lot of hover, land, check temps, lean a click or two, repeat. It has a governor, a multigov, but it was not yet hooked up. For the next weekend I had put a new set of Rail 96 tail blades on it. The mains are Rail 606. Still flying on throttle curves. At some point during the first flying session we tached the head and it was in the 1800 range. I had read that the heli prefers higher speeds, in the 2100, 2150 range so working towards that. Anyway, first flight with the new tail blades I notice a vibration. Its noticable in hover, so since the tail blades are the only thing new I swap out from one of my other birds. At this point headspeed is still in the 1800 range. The vibration goes away, or calms down enough to not be obvious. Heli is behaving well, so I keep working on leaning the motor since it is obvious that it is rich and not much punchout power. Back plate is cool to the touch. Finally get the motor to a good point. However as the headspeed is increasing I notice that the vibration comes back. Feeling like the motor is ready for the governor I hook it back up. Will have to confirm the speeds, but they are in the 1850, 2000, 2100 range. At 1850 the heli is pretty calm, 2000, vibration, 2100 a lot of vibration, feel uncomfortable at that level of vibration. I have not checked the main blades for balance yet, and although the tail blades came off another machine that flies smooth I do not know at this point yet if they are 100% balanced. So that's the start of it, at this point I just know I have a vibration issue.
I pull the main blades, they both weigh the same within a gram, and both tip over a round rod at the exact point. (longitudinal balance?) So I don't think I have a main blade balance issue. I also check the Rail tail blades that I took of, no problems there. Since the heli is used, I do not know if the main shaft and tail shaft are true. Regardless,one thing I become aware of is that I am spinning my tail in the opposite direction than the manual. The manual says to rotate belt 1/4 turn clockwise. During assembly of the tail section I didnt look at that, I just turned it so that the tail turns as every other heli I have, front tail blade rotates up into downwash of main blade. The belt was not turned more than 90 degrees. In my head you should be able to turn it either way, but since the manual says to turn it the other way, and I have a vibration issue that seemed to be tail related (may not be) I decide to do it the way the manual calls for. The tail belt is a new stock belt, and it has been sprayed with 3M silicone. Spinning it the wrong way I had no issues with the belt setup. Once I corrected it, and start spinning the main head forward by hand, just within a few turns the tail belt does not want to track and actually jumps the tail idler pulley. I forget to what side now. Spinning the head backwards, (spinning the tail in the original wrong direction) has the belt tracking decently. Running it with the tail idler pulley removed to observe natural tracking tendencies shows me that the belt doesnt want to stay in center of the tail belt pulley, and will walk itself over to one side or the other depending on direction of rotation. With idler pulley on in perscribed direction of rotation it jumps the idler pulley, in wrong direction of rotation it stays on.
So thats one of my questions, any ideas what to look for to correct this tail belt tracking issue ?? The are no obvious signs of wear on tail pulley or idler pulley. Only thing possibly weird is that the tail belt leaves a residue on the face of the idler pulley. I believe this is the silicone. From what I read the 3M silicone spray is supposed to be ok to use. The rest of the vibration issues I really cant get bent out of shape over until I put new shafts in it to eliminate any of that possibility, unless all this sounds familiar to someone. Tail belt tension is probably on the tight side. During spool down, near almost stop I sometimes did hear a few pings that sounded like belt related so I never got around to loosen it up. I have tried several different tensions on the bet while trying to get the belt to track. Didn't help any. Without the tail idler on it will run in any configuration, head forward or backwards, belt clockwise or counterclockwise rotation, but the belt will pull to one side of the tail pulley. With the idler pulley on the tail the belt will only stay inside the idler pullet with the head rotating forward, and belt rotated counterclockwise resulting in backwards from manual setup.
Sorry for long post, wanted to provide detail and info. Thanks for any help !
