Tail drift and unstable

[SgtGarand]

Well it's been at least two years since I've had reason to post here! After having a few crashes with the 400 and being unable to keep it steady in the air, I decided to rebuild it and fix the damage from the last crash, remove the stock gyro and tail servo, and keep it in it's box until I could replace the two. Last night I decided to "borrow" the GY48V gyro and Futaba S3114 servo from the BlueRay 450. I think I'm going to convert the 450 to flybarless, but that's a post for another day.

So, I set everything up mechanically centered in rate mote, flick the switch a few times to make it learn the center, and rebind the heli. I spool it up on some smooth concrete and it starts to rotate CCW, I switch to rate mode and it spins even more! I go over everything quite a few times; checking the tail blades, tension on the belt, checking center, and my tx rates(70% hh, and 40% rate just to start with). Still no go. Got home from work today and decided to be brave/dumb and get it in the air. Pucker factor was high. My biggest fear was that it'd spin out of control only to crash it again in less than 24hrs. It spins completely side in, nose 90 degrees to my left by the time I reach mid stick. I reposition myself for orientation sake and get it off the ground. Maiden flight after such a long time! It didn't spin out of control, but the tail did drift in HH and the heli itself seems really unbalanced. If not for sim time, I wouldn't have managed keeping it airborne for that long or landing smoothly back on the concrete. But while I had it going I figured to roll with it and enjoy the moment, despite fighting it.

I'm going to have to rebuild the head it would seem, unless something else could cause such an imbalance. The battery does cause it to be a little nose heavy. I do notice that the rotor and blades don't appear to be perfectly parallel with the body/ground. It looks like the blade to the rear slants lower than when it's towards the front. It stands out most when compared with the boom. Is that normal for the 400?
My other main concern is how to correct the tail drift?

Sorry for the long post

[Harbormaster]

Is the gyro correcting the right way? That is, when you look straight down on the vertical tail blade from behind, it turns to the left when you push the stick left. But does that same blade turn left when you turn the heli to the right?

Two times I got that wrong after a rebuild and was mystified why the heli kept spinning on takeoff.

[SgtGarand]

Yea it's responding and correcting as it should. I had to reverse the RUDD setting in the tx since left input was making it go right.

[Harbormaster]

It's hard to tell at a distance from your description. Tail blades on the right way? Belt turning the right way. (I have gotten both wrong before--Murphy's law and all that).

[SgtGarand]

Everything is the way it should be mechanically. Main rotors spin CW and the tail spins CCW. It just acts like the tail is pulling more than it should to counteract the torque from the rotor.

[SgtGarand]

Well I made an interesting find tonight.
I decided since I was going to re-level the head, that I would use the CNC head from my Blueray 450 because I am going to convert that to flybarless. After removing the head and leaving the swash, I checked the level using the tool and the swash/servos were as they should be. But when I spun up the motor slowly, to my shock, the tail didn't move at all. I was expecting it to spin circles without the main blades.

So now I have to wonder why it can't hold with the main blades.

[Harbormaster]

Are you saying that now the tail blades aren't rotating at all? That would seem to be be easy to troubleshoot...

[SgtGarand]

No, the tail blades are spinning just fine. All I did was remove the rotor head and blades. I spin up to mid stick and the heli stays perfectly still until I add rudder.

[Harbormaster]

Hmmm... It's hard to say what it should do exactly without the main blades. Theoretically, if you have the correct amount of anti-torque correction added (the top tail blade pointing a few degrees to the right when viewed from above and behind when in Rate mode) that would push the nose to the right if there were no main blades attached. But that effect might not be enough to push it very hard, at least compared to when you actually "add rudder," which is likely going to be a much bigger input.

So, do you think you have enough anti-torque correction added to the tail blades? (The only way to know for sure, of course, is to put it in rate mode with the main blades on...)

I went back and read your original post. It says, "flick the switch a few times to make it learn the center." I have never heard of such a function. There is no learning or programming going on (other than for the human operator) when you flip (I assume) the gyro switch. It just changes back and forth between rate and heading hold modes. If you do flip the gyro switch back and forth quickly, you can often get the gyro to reinitialize (LEDs usually blink on many gyros). Is that what you're thinking of?

Try putting it in rate mode (which on the 400 stock gyro is anything below 50% if memory serves) and then set the anti-torque as described above. Your settings should be about (hard to remember) 65 for HH(?) and 35(?) for rate mode.

Reading some more of the original post, I don't know the two(?) gyros you mentioned, but I used to have a Futaba gyro that was programmable. If so, is it possible that the programming is wrong? Really this shouldn't be difficult. Even if the tail setup is far from perfect, HH should be able to hold the tail stable. There is some fundamental problem here. Maybe shoot and post some video?

When you have the heli in rate mode, are the blades biased a few degrees to the right as discussed above, and then when you move the nose to the right, does the top tail blade move to the left as viewed from above, and vice versa? If you have the settings correct and the right amount of gain, you should see the tail blades move in a logical, predictable, easily visible manner in rate mode. If you're getting that response, you should be in good shape.

[SgtGarand]

The gyro is the GY48V and when viewing setup videos for it, the flipping of the switch rapidly was one of the suggested steps. Whether it does what they say or not, I'm not sure, since I'm use to using the stock gyro before now. It never seemed to keep the tail steady so that's why I wanted to replace it.

With the main blades on the heli would spin slowly CCW while HH was on. In rate mode it would spin much faster. I guess the option I have then is to adjust the linkage to give it a slight pitch to counteract the blades. I tried to set the slider in the center but maybe there's just no pitch at all where it's at? I thought that was the ideal setup, but maybe I am mistaken.

It may take awhile to get video for it since I just got finished converting it to the metal rotor assembly. The 450 it came from gave me a bit of a mishap on the workbench last week and one of the plastic ball links broke because of it. So once I get that replaced I can continue with it.

[Harbormaster]

Originally Posted by SgtGarand

The gyro is the GY48V and when viewing setup videos for it, the flipping of the switch rapidly was one of the suggested steps. Whether it does what they say or not, I'm not sure, since I'm use to using the stock gyro before now. It never seemed to keep the tail steady so that's why I wanted to replace it.

With the main blades on the heli would spin slowly CCW while HH was on. In rate mode it would spin much faster. I guess the option I have then is to adjust the linkage to give it a slight pitch to counteract the blades. I tried to set the slider in the center but maybe there's just no pitch at all where it's at? I thought that was the ideal setup, but maybe I am mistaken.

It may take awhile to get video for it since I just got finished converting it to the metal rotor assembly. The 450 it came from gave me a bit of a mishap on the workbench last week and one of the plastic ball links broke because of it. So once I get that replaced I can continue with it.

OK, now we've got it. First, the gyro switch flipping just does what I said--causes reinitialization of the the gyro. No teaching or programming or anything. A quick Google search should bring up the manual.

You definitely do need some offset as mentioned to counteract the torque of the main blades. Again, the top rear blade should be facing a little to the right when you look down on it on the bench in rate mode.

The reason your nose is going left is because you don't have enough rightward (if that's a word) correction. HH is doing all it can, but even when it is commanding maximum right turn, it still can't pitch the tail blades far enough to make the nose go right. So the solution here is simple: give the tail blades a lot more bias for nose-right. Then it will at least be able to hold the nose steady in HH. Then you can fine tune in rate mode. Congratulations! Problem solved!

[SgtGarand]

Thanks! That makes sense and should be an easy enough fix.

[SgtGarand]

I used one of the link connectors from the 450 since I have replacements on the way. Got the CNC head leveled out and took it out to try. I thought the battery still had enough charge, but it gave me about 20 seconds and started losing power. Unexpected auto practice I suppose. Used the battery I had feared was on it's way out and I flew it for a few minutes. Needed some trim to the left and forward, the tail still wasn't completely still, but getting better. Got it in and checked the battery. It was puffed and pretty hot and was quickly taken outside! Adjusted the links to correct the trim and took it back out with the 3rd battery. Only needed two clicks of cyclic trim this time and will adjust the tail slightly since I think it's overcorrecting a little to the right instead of drifting to the left like before.

Feels good to get it in the air again and start overcoming the big heli jitters.

[Harbormaster]

Originally Posted by SgtGarand

will adjust the tail slightly since I think it's overcorrecting a little to the right instead of drifting to the left like before.

Sounds like progress.

[SgtGarand]

Slowly but surely I hope!
I think the servo I'm using for the tail is slower than it needs to be. Only reason I got was because I heard it was a good combo with the GY48. It will be replaced soon either way. Looking at the emax ES9256HV or ES9257 and Hitec HSG-5083MG. Already got one Hitec on the way to use for the 450, so I'll be able to see how that one does at least.

Edit to save multiple posts: Took it out for two full battery packs this afternoon. Still had to adjust the linkages a bit on the tail and swash and fix it's CG since it's too heavy in the nose. Brought it in and went over it. Belt had gotten a bit loose, easy fix. Decided to go tighten everything else down while I was at it and noticed the ball links in the swash, that I had to change to make the aluminum head work, were coming loose and weren't tightening up like they should. Hopefully the threading inside isn't stripped, I haven't tried putting the stock balls back on to test yet. If thread is good I will just order replacement 450 ball links. If thread is bad i will have to find a way to mount a bracket on the front to use the Align 450 style swash. Either way I'll have to make an order for the ball links and wait.

I just want to fly the thing