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SAB Goblin 500/570 SAB Heli Division - Goblin 500/570 Helicopters |
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03-13-2017, 05:53 AM | #1 (permalink) |
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Join Date: May 2014
Location: France
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Goblin 500S /BRAIN cyclic wobble/vibrations at the end of the flight
Hi, I have 140 flights on my G500S, doing sport flying at low HS (2200/2300), first with stock blades and recently (last 20 flights) with RAILS 516. I fly with HW100A V3 governor.
I have observed an important skids vibration when hovering at the end of the flight, just before landing. It doesn’t happen at take-off. The issue occurred both with stock blades and with the Rails. ESC is around 80% for 2200 rpm. I fly with BRAIN2 with Sport default setup, using the 430-480 mm default settings. Vibration logs in the BRAIN are well within the limits. I have seen similar issue in thread: https://www.helifreak.com/showthread.php?t=749704 What shall I try first? Blade tracking looks OK (and was OK with stock blades) and I made a complete rotor head maintenance 2 months ago, the dampers looked OK (I fly very “soft”…). I think the first try is to lower the cyclic gain in the BRAIN, correct? Shall I also try to fly without governor (or using BRAIN governor instead of the HW one)? PS: during the last session I tried to fly at 1900 and the heli was oscillating a lot (not only the skids) around the pitch axis. Maybe it is a symptom of a too high cyclic gain? Thanks in advance for your help, Luca
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Goblin 500 sport Goblin Black Thunder Sport 700 OMP M4 All with BRAIN2 and Spektrum TX |
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03-13-2017, 06:24 AM | #2 (permalink) |
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Join Date: Nov 2009
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If both mains show exact 0 mid stick. Something coming loose? One grip ball came loose on my D380. Apply pressure to the servos and check for twitching. Head balance comes to mind with the oscillations. Just had the main bearings and yes the shaft worn on my 450.
Suddenly a loose grip bolt comes to mind since you had it apart 2 months ago
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Align 450Pro 3GX, 500ESP/DFC 3GX, 500L, 550 DFC MicroBeast , Velocity 50 Vbar OS55 HZ-R, D380 DFC D420, G500 Sport Microbeast, All HW V4, X5 stretch 220 Flame Emax Bullet Force V2 VTX Last edited by bad007; 03-13-2017 at 10:31 AM.. |
03-13-2017, 02:19 PM | #3 (permalink) |
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Join Date: Dec 2011
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As per the manual, one may experience some wobbles at lower headspeeds. Raise or lower the headspeed to find improvement, but definitely try lowering the cyclic gain - it's usually the first place I start.
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Mini Protos, Voodoo 400, Protos 380, Protos Leggero 700 & 700X, Diabolo 700 |
03-13-2017, 07:40 PM | #4 (permalink) |
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Join Date: Jul 2016
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Albeit being a noob myself, I agree with Chris, I'd raise the HS, especially since you point out that the heli doesn't do it when taking off.
I'm thinking that you probably have a slightly higher HS with a fresh battery at the beginning of a flight, although the use of the HW governor "should" negate that. Increase the TC to 85%; that still leaves you a bunch of headroom on the governor, especially since your style of flying is gentle, and it will raise your HS. |
03-14-2017, 06:16 AM | #5 (permalink) |
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Join Date: Nov 2009
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I have the same G500S and it has 0 wobble no mater low I run it.
The only thing that happens if I run it low enough I loose mechanical tail gain and get a slow wag. Shaking skids just shows you have to issues in the head , tracking and or a cyclic servo failing causing cyclic shakes. Something simple like loosing wiring or gyro plate came loose. Take the head apart again and recheck the thrust bearings and balance the entire head assy. Let Tail Blades on , take mains off, disconnect the tail control rod and run up on the bench and look for servos twitching. Using HW store or FLF gov? What temps are you flying in, if cold mains will loosen up if you don't let it acclimate to the cold and recheck them, one to loose will do that. BTW been crashed?
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Align 450Pro 3GX, 500ESP/DFC 3GX, 500L, 550 DFC MicroBeast , Velocity 50 Vbar OS55 HZ-R, D380 DFC D420, G500 Sport Microbeast, All HW V4, X5 stretch 220 Flame Emax Bullet Force V2 VTX |
03-14-2017, 11:03 AM | #6 (permalink) | |
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Thread Starter
Join Date: May 2014
Location: France
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Quote:
I check the head only 20 lfights ago, but I can try to put it on the Dubro and see if it is still dead on...Ciao
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Goblin 500 sport Goblin Black Thunder Sport 700 OMP M4 All with BRAIN2 and Spektrum TX |
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03-14-2017, 03:45 PM | #7 (permalink) |
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Join Date: Nov 2009
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Got to many helis, lol just remembered a 500 that drove me nutz with cyclic wobble last summer, 2 months swapping out everything but then I found it. The tail made a slight buzzing sound just at a certain speed and the high HZ buzz drove the FBL unit crazy. On the 500S maybe the tail shaft dampers at that magic moment when the voltage drops is doing the same?
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Align 450Pro 3GX, 500ESP/DFC 3GX, 500L, 550 DFC MicroBeast , Velocity 50 Vbar OS55 HZ-R, D380 DFC D420, G500 Sport Microbeast, All HW V4, X5 stretch 220 Flame Emax Bullet Force V2 VTX |
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