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Old 06-25-2012, 11:38 AM   #1
rchelijc
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Default Slow Intermittent Tail Wag AR7200BX (BeastX) YGE Gov

Solved it, so I'll just post how I did.

First, super butter smooth no binding tail slider and pitch mechanism - didn't help in my case. Wag was still there. Actually made zero difference.

Symptoms: slow intermittent tail wag, at higher Gyro gains, wag becomes a little tighter but still there, 1-2 slow wags every 5 seconds or so. Wag arc around 5-15 degrees, and raked approx 1 second per wag.

3 things from reading around are common causes:
1. Famous Protos binding somewhere in tail
2. Governor acting up
3. BeastX dreaded parameter D

The only thing that solved it was turning Parameter D to very low.

Immediate effect - zero wag. I now run very high gains. Still playing around but at 80-90%.

Setup: Stock tail blades with custom made (from 0.5mm packaging) shims to fit infinity tail thrusted grips, scorp 880kv 14t 6S, 18T tail pinion, align 425D, YGE 80 + gov store, s9254 tail, mks 9670A+ cyclic.
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Old 06-25-2012, 12:32 PM   #2
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You try 20t tail pulley? That is what solved the exact same issue for me. Param D is at default, and tail is rock solid. The 18t pulley was the source of my issue.

Unless you are running stretched.. I believe the 18t was designed for a stretch setup, yes?
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Old 06-25-2012, 04:00 PM   #3
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i might have to try the 20t pulley. im having a slow very small wag with the beastx aswell. tried everything i could think of. governor off, change gains in transmitter and beastx, super smooth tail, diff tail blades....at a lost. also have pitch up thing during FFF when i hit the collective, i bumped up the pitch up compensation to max and it still does it...sigh* =\
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Old 06-25-2012, 04:12 PM   #4
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I am by far no expert on the Protos, but I can definitely see the issues with 18t tail pulley on a non-stretch causing issues with tail authority / wagging. It was a night and day difference when I went from 18 to 20, and the 18 was only on there because it came that way when I bought it used.
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Old 06-25-2012, 05:53 PM   #5
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I thought 18T gave the tail more authority, as in it spins faster than with 20T? Reason I went this route is because I heard of authority issues at lower headspeeds on a stretch which runs at up to 2400rpm (I run 2000, 2400 and 2600, unstretched). The principles I followed when building was based purely on research only at first, and I gathered the following:

- I want a headspeed of sub-2000 all the way to 2900 governed
- Scorp 880kv on 15T pinion is too much, but people are running this configuration with 20T tail
- My scorpion is actually around 930kv, reached an unloaded no-blade headspeed at 3800 with 15T!!
- 880kv with 15T too much for 18T tail
- 880kv with 14T just nice if I want a max headspeed around 2700-2900rpm goverened. I tached my 14T setup at 3500+ without blades. I estimate around 3200-3300rpm when loaded and hovering, so just nice
- 880kv with 14T and 18T tail is perfect if flying a little harsh on collective
- Tail servo mechanical gain - ball-link around 10mm from servo arm centre for s9254. Incidentally this have me perfect throws, as in max servo travel = max travel on pitch slider

Are you guys setting up your tail like this? It seems 20T tail pulley is the default one in my 500, and 18T is optional.
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Old 06-25-2012, 06:00 PM   #6
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Quote:
Originally Posted by jaofos View Post
I am by far no expert on the Protos, but I can definitely see the issues with 18t tail pulley on a non-stretch causing issues with tail authority / wagging. It was a night and day difference when I went from 18 to 20, and the 18 was only on there because it came that way when I bought it used.
I know what a tail looks like if it's over-geared / too high gain. It'll look like the wagging of an excited puppy on pirouette stops. And if gain is even higher, it's wag rapidly even on the ground.

The wag I'm referring to is slow, and intermittent. If you can imagine your windscreen wiper on the lowest setting, it's something like that. Slow wag, wide and loose arc, and comes on every few second only.

Gains from low to 100% (on mine anyway) resulted in no other change to the wag, other than a slightly narrower arc wag. However, I can tell the gain settings are applied because I
Can go rate mode from Tx to check mechanical setup, and then all the way to 100% where hard tail stops and the tail wags like crazy... But when it settles down, the sllloooooowwww wag starts...
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Old 06-25-2012, 06:03 PM   #7
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Quote:
Originally Posted by Scured View Post
i might have to try the 20t pulley. im having a slow very small wag with the beastx aswell. tried everything i could think of. governor off, change gains in transmitter and beastx, super smooth tail, diff tail blades....at a lost. also have pitch up thing during FFF when i hit the collective, i bumped up the pitch up compensation to max and it still does it...sigh* =\
I'm assuming your setup is similar to mine...

Did you lower Parameter D to "very low"? The LED would be purple in the 7200bx.
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Old 06-25-2012, 06:27 PM   #8
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My Param D is very low too. I didnt have tail wag, but twitches during tic toc's Could not get rid of no how. Lowering gain, she would then drift a little. Raise gain and would wag mopre. Lowering param D I could raise gain a bit and she is now solid as a rock
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Old 06-25-2012, 06:35 PM   #9
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Yup I changed para d all the way to low, no difference =/. Except a slightly weaker tail

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Old 06-25-2012, 09:47 PM   #10
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I was under the impression that the 18t pulley for the stretch was to limit the rate at which the tail blades spin, as the tail is longer, the rate required to reach the optimal tail authority is lower. Thus 18t on a non-stretch may lead to wag issues?

Someone correct me if I'm wrong.
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Old 06-25-2012, 10:19 PM   #11
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Quote:
Originally Posted by jaofos View Post
I was under the impression that the 18t pulley for the stretch was to limit the rate at which the tail blades spin, as the tail is longer, the rate required to reach the optimal tail authority is lower. Thus 18t on a non-stretch may lead to wag issues?

Someone correct me if I'm wrong.
Smaller tail pulley = faster tail rotor speeds, so yes you are wrong. Its to compensate for the slower headspeeds most run with 470mm blades.
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Old 06-25-2012, 10:26 PM   #12
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I take it you've read the BX setup sticky in the BX forum and tried it?
http://www.helifreak.com/showthread.php?t=279967
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Old 06-25-2012, 10:28 PM   #13
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Quote:
Originally Posted by jaofos View Post
I was under the impression that the 18t pulley for the stretch was to limit the rate at which the tail blades spin, as the tail is longer, the rate required to reach the optimal tail authority is lower. Thus 18t on a non-stretch may lead to wag issues?

Someone correct me if I'm wrong.
smaller tail pulley = higher RPM. Think of it as a main gear for the drive ratio motor:tail=15t/18t (faster) vs 15t/20t (slower).

OP, I can definitely see a problem with using an 18t tail pulley at 3000+ rpm main rotor. Your tail will simply have too much authority around neutral pitch as well as experience flow separation (i.e. stall) at higher pitch angles. Perhaps counterintuitively, too much tail authority leads to decreased performance overall.
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Old 06-25-2012, 11:15 PM   #14
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Quote:
Originally Posted by Dr. M View Post
smaller tail pulley = higher RPM. Think of it as a main gear for the drive ratio motor:tail=15t/18t (faster) vs 15t/20t (slower).

OP, I can definitely see a problem with using an 18t tail pulley at 3000+ rpm main rotor. Your tail will simply have too much authority around neutral pitch as well as experience flow separation (i.e. stall) at higher pitch angles. Perhaps counterintuitively, too much tail authority leads to decreased performance overall.
Agree completely. However, it is a compromise since I now run 2600rpm at max (maybe 2800 later just for fun to see how fun it is). But I also do run around 1950 and 2200 rpm, so I feel that more authority is required?

I understand those stretched run 2400 headspeed, so the mine is right there?
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Old 06-27-2012, 10:30 AM   #15
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I just took a look at my tail...and notice I have a lot of slop in my pitch slider. The brass piece has a lot of in and out movement. This thing is pretty much brand new. I've got maybe 15 flights on this heli so far. (The first one had some issues). Could this cause the slow wag I am having? The slop seems a bit excessive to me...

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Old 06-27-2012, 12:56 PM   #16
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Quote:
Originally Posted by Scured View Post
I just took a look at my tail...and notice I have a lot of slop in my pitch slider. The brass piece has a lot of in and out movement. This thing is pretty much brand new. I've got maybe 15 flights on this heli so far. (The first one had some issues). Could this cause the slow wag I am having? The slop seems a bit excessive to me...

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I'd say more than 1mm slop is too much for the Prots tail. But slop won't cause wag, rather it manifests as a vague feeling around center, wandering or drifting. If your tail wags it's probably caused by binding (perhaps related to the slop).
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Old 06-28-2012, 11:52 AM   #17
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Check vibration for any strange wag / cyclic behavior. I nearly dumped the protos the other day.. Was flying real nicely than a couple to tictocs and suddenly the heli banked left hard.

Manged to regain level flight 20 ft off the ground and autoed, wasn't pretty but saved everything. It actually tipped to the left just in landing!!?

Checked her over could not figure out. Lift off again at 1850rpm, she's all fine. Idle up to 2400 rpm and I got a hard bank left. After a while it disappeared..? Then tried idle 2 at 2600 Rpm and hard bank left again. Immediately Dropped to 1800rpm to land.

Didn't dare risk it so I removed main blades and spooled up... Massive tail vibes.. The entire tail and tail servo was a blur! Removed tail blades.. Same thing. Dusk was approaching fast so I went home, tore the tail apart and balanced the tail grips + shaft on te balancer and completely out of balance!! On close look one f the tail feathering bolts had backed out a bit!

All fixed now, but vibes sure can cause some strange and disastrous behavior on the beastx
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Old 06-28-2012, 07:15 PM   #18
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Yeah I stuck a piece of tape on one of the tail blades. And that almost pretty much cured my slow tail wag. I'm guessing it had to do with bad vibes. The tape I used though did not stay on during flight. And the slow wag started again. So will use some better tape next time

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Old 06-28-2012, 09:27 PM   #19
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Quote:
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The tape I used though did not stay on during flight. And the slow wag started again. So will use some better tape next time
Make sure you wrap the tape over the leading edge of the tail blades, otherwise pretty much any tape is eventually going to blow off in flight.
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Old 06-28-2012, 09:42 PM   #20
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Quote:
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Make sure you wrap the tape over the leading edge of the tail blades, otherwise pretty much any tape is eventually going to blow off in flight.
+1

My align 425d blades needed 2 full stickers to balance them. They're wrapped over leading edge directly over CG point of blade, or at a point to shift CG of the lighter blade so that it matches te heavier one
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