Violent vibrations at ~1800 rpm and higher.

[tahustvedt]

I had a problem with wandering tracking and violent vibrations at 1800 rpm and above. Today I discovered the cause of the vibration problem and the tracking problem seems to be licked at the same time.

I removed the tail braces today to test without them and this fixed the vibration problem completely. My theory is that there is some flexibility in the main frame between the top part and the bottom where the braces are attached, and at 1800 and above RPM the small resonance frequency of the bottom of the frame is amplified by the braces and the tailboom.

It's now completely smooth at over 1800 RPM and I can fly normally without worrying about sudden vibrations appearing without warning. The vibrations once caused the canopy to fall off in flight and also caused the rear tailboom brace mount to break while I was flying and the RPM increased during descent/autorotation.

I fly with symmetrical fiberglass blades at up to 1950 rpm now.

Another alternative solution to removing the braces might be to stiffen the frame on the left side where Ikarus made a large cutout for the yaw servo for some reason. I suspect that installing a carbon fibre plate over the cutout with screws on top and bottom will eliminate the problem.

[Rotowingconvert]

Are you by chance known as Lynxman? If not then there are several people who have found out that the boom braces aren't designed for high RPM. I have had serious tracking issues with my Royal which were partly due to a faulty bearing in the washout arms. After correcting that I still have tracking problems just not as bad as before. I am going to remove the boom supports this weekend and see if it makes any difference. I don't have a tach so I don't know what RPM I'm running at now. With a basic suggested brushless outrunner motor that I'm using I doubt very seriously I am hitting 1800 RPM much less 1950.

Gary Morris

[tahustvedt]

Hehe. Yeah it's me. :)

[MartinHT]

Are you by chance known as Lynxman? If not then there are several people who have found out that the boom braces aren't designed for high RPM. I have had serious tracking issues with my Royal which were partly due to a faulty bearing in the washout arms. After correcting that I still have tracking problems just not as bad as before. I am going to remove the boom supports this weekend and see if it makes any difference. I don't have a tach so I don't know what RPM I'm running at now. With a basic suggested brushless outrunner motor that I'm using I doubt very seriously I am hitting 1800 RPM much less 1950.

Gary Morris

Hello Gary,

what is the result of your test? How did the boom braces influence the blade tracking?

Regards

Martin

[Rotowingconvert]

After removing the boom braces I had one good flight with virtually no tracking issues. The following weekend, I went flying and the tracking was off by at least and inch! There was absolutely no changes made to the helicopter during that time. I re-tracked the blades and they were within 1/4 inch in track and the same thing happened on the next flight, the blades were out of track again. This is very trying to ones patience as the blade tracking issues with the Royal have been on going for some time. The only possible solution I see is to replace the swash, head, pitch arms with metal and see if that can keep the tracking from changing in-between flights. The cost to make the upgrade is more than the cost of the entire Royal kit! :(

Gary Morris

[MartinHT]

Hello Garry,

there seems to be a solution suggested by Ikarus, see describtion on the german Questions to ikarus. Have not tested it myself yet.