GT-5.1 Why Is My Disk Tilting Forward at 3500 RPM

[Bladecpnitro]

I had my 450 dialled in better than ever but then it started doing things its never done before. I had it to where I could finally fly smooth as silk at 3500 head speed with very very little head wobble, almost unnoticeable. But then during my 3rd round of packs the wind picked up and something happened.

It does okay long as I don't hit IU 2 and go above 3200 head speed. When I do that and switch to 3500 RMP now the bird wants to tilt forward and take off forward on me as if there were 5 or 6 clicks of forward trim in my TX but there is none. I can bring it back but it leans back forwards quickly and I have to switch back to IU 1 to finish the flight . What could be the cause of this forward tilting?


I haven't flown in IU2 @ 3500 rpm much because I never have been able to completely get head wobble dialled out and its driving me nuts.

My gyro could possibly be about to go out on me, it was flying too good to be acting like this. For several months I've flown it booting up with a scrambled screen occasionally and sometimes a blank screen but its flown great regardless at 3200 HS.

Could the cyclic balls be out too far? Swash pitch is set to 90% and I have 13 -/+ pitch and 10 degrees of cyclic pitch with the TX Endpoints set to 100%. Servo endpoints in the GT are reduced to 200 from the stock 250 to get the cyclic pitch down to 10..

[Bladecpnitro]

I'm hoping this is solved. I've moved the cyclic balls in one hole to lower mechanical gain.

I was at 13/13 Pitch 10 cyclic, Gt servo endpoints lowered to 200, swash P gain 50, I gain 40, I D Stick 100, D sense 22 and not doing well at all at 3500 but did decent at 3200.

Now I'm at 14/14 Pitch, (wasn't happy with hard punchouts at 13/13 , 8 Cyclic Pitch, Swash Pitch 127 maxed out, GT servo endpoints stock 250, TX endpoints set 100%, TX Rudder end point 150%
Swash P Gain 70, sw I gain 60 D Sense 22. ID stick 100

I got one flight in this morning and its working the best I've ever seen it at 3500. 14/14 Pitch gave it a lot more low and mid range snap as well. It gets moving quick.

It will take more flights in windy conditions to know for certain maybe I can get the Swash P gain up some more.

[Bladecpnitro]

Nope no good, still tilting forward, now I'm hoping tail vibes are causing it. I have some kind of vibration that's shaking my rudder servo rod like crazy when spooled up. When I took the grips and blades off it stops. So hopefully I'll nail that down soon. All that stuff is brand new except the actual grips and blades. All new bearings, tail piece and shaft.

[Bladecpnitro]

It must have been vibes. Last night I rebalanced main and tail blades after narrowing bad vibes down to the tail.
Also loosened belt a little as well belt drive gear mesh. Belt gear mesh was jammed tight.

Now it is truly flying better than it ever has. It was dead calm tonight so still need to see how it handles the wind.

With 20 minutes before sunset I was able to charge and get 2 flights in. Love those 5C charge capable packs. It used to take 1.5 hours to charge one pack with my 3 S Blade SR Charger.

[gwright]

there's a vibration filter setting you can increase that usually bypasses shakes that you have difficulty diagnosing. It's like treating the symptom, not the disease, but we all get lazy sometimes and do things like that <G>

Not necessarily the issue discussed here, but thought I'd mention it. I recently changed radios. I dearly loved my 14MZ, and the features are still state of the art, but I wanted telemetry, so I bought a 14SG. I had the darndest time at first, will all my helis doing some strange things, like they were going just slightly out of trim at times. I finally realized I was pulling things offcenter here and there since the new radio had standard springs .There is a stick deadband setting in the GT5 that I increased a lot and bypassed my thumb problems, but that was treating the symptom, not the disease. The adjustment is there for transmitters that may not have good pots and don't necessarily center properly, but my stupid thumbs were creating that situation with a tx that has very good pots, so the stick deadband increase bypassed the human problem.
I like the sticks to feel like they have leaf springs off a peterbuilt and on the MZ I'd been flying the last decade, I had put really stiff springs into it, and cut a couple coils off them also to stiffen some more. I played with some different springs and got the sticks to feel like my MZ, and was able to drop the deadband back down to default levels. Was kinda eye opening that a simple thing like spring tension could make that difference. I guess age affecting dexterity, coupled with years of flying with herculean spring tension created a brain to thumb interface problem.

[Bladecpnitro]

Which Menu is that filter located? I think I had it set almost to the highest setting.

I think a fairly easy approach to tracking down vibes is to take the main blades off 1st and spool the heli up full blast and see if the vibes lessen. Then take tail blades off to see if the vibes get less, Then take the tail grips off to see if vibes get less and keep going until you find it. Chasing vibes is one of my least favorite things to do and the more RPM's you try to run, the more very tiny imbalances show up.

[sbc]

Just a quick add on to this thread. I have a similar but worst problem with my very old Trex450S. Above a certain head speed the swash will tilt 45 degree to port and crash into the ground. Without main blades everything works fine. Changing blades and complete tail assembly did not solve the problem, Out of pure luck, I cured it by reducing the speed of the tail rotor by changing the tail gears. I was using the 1st generation 109 teeth and changed it to the later 106 teeth gear.

Now that I have upgraded to the latest FW 2.02. I might try the higher tail rotor speed again to see if the problem comes back.

[Bladecpnitro]

Originally Posted by sbc

Just a quick add on to this thread. I have a similar but worst problem with my very old Trex450S. Above a certain head speed the swash will tilt 45 degree to port and crash into the ground. Without main blades everything works fine. Changing blades and complete tail assembly did not solve the problem, Out of pure luck, I cured it by reducing the speed of the tail rotor by changing the tail gears. I was using the 1st generation 109 teeth and changed it to the later 106 teeth gear.

Now that I have upgraded to the latest FW 2.02. I might try the higher tail rotor speed again to see if the problem comes back.

It has to be vibes somewhere. Bent shaft, blades or motor out of balance or bad bearings with a lot of play. Gear mesh too tight can throw some vibes in the mix as well as rob power.

My problem resurfaced just last weekend with the tilting forward in IU 2 at 3500. I found the problem to be worn tail bearings and tail shaft. Also I found my motor can to be grossly out of balance so I balanced that as well and that really smoothed things out better than I'd ever seen at high head speed.

Its a good idea to make sure your tail blade grips will teeter balance with no blades on them. Then make sure your tail grips have equal weight. Its harder to do on tail blades. Find and mark the tail blade's CG, then bolt them together and teeter them. Then add tape to the light blade at the blades CG or a dot of glue might work well until the balance perfectly.

[dhc8guru]

My Trex 500 tilted right over 3000 RPM with a ZYX. Ended up being vibes that the right aileron servo didn't like over that RPM. Replaced the servo and no longer a problem