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Old 12-22-2012, 09:36 AM   #1
Primus
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Question Please help, Logo 400 tail wag

Hi fellas,

I've purchased here on HF recently a Logo 400. It has arrived in a such a bad shape (canopy destroyed, frame melted, overall it's a mess). Will avoid for the future. I myself cannot imagine to sell an airframe in such a shape.

Long story short trying to put in the air today, and having lateral tail oscilation and some frame vibes in hover. Changed tail gain no difference.

Please take a look to my analiser photos and let me know where should I start looking for.
I'm sure that the heli was crashed quite bad, lipo in fire perhaps.

Set-up
Vbar 5.3, Haker Motor, CC 75 Esc, 3000 6S Turnigy's, Edge mains, stock plastic tails ATM.
Not using for instant the Vbar Gov.

Thanks in advance for any advice.

Here's the spektrum analiser:


With Mains and tails:



No Mains but tails:





No Mains No tails:

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Last edited by Primus; 12-26-2012 at 09:33 AM..
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Old 12-23-2012, 11:56 AM   #2
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At what RPM are you flying and what tail servo are you using?

The Logo 400 is very sensible on the tail servo type, no matter how accurate is the mechanical setup.

Salutations,

Ricci.
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Old 12-23-2012, 12:47 PM   #3
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9257 on tail, never measured the RPM as I've purchased the heli with the pinion on the motor.

Thanks for posting
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Old 12-23-2012, 02:14 PM   #4
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Are you getting a slow wag in a hover?
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Old 12-23-2012, 02:51 PM   #5
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Always check for a super super smooth tail. Really zero friction.
MrMel says a bit of slop is better than any stiffness.
It takes time to achieve this.

I think a low wag if hover, and a poor tail in pitch pumps (looking like the pre comp values are wrong) is some stiffness in the linkage. Check everything from the servo horn backwards.

Also, as the 400 sensitive to vibrations, build it *really* carefully.
It is possible to get a vib free 400. It just takes time.
This thread has my experiences on the matter.
http://www.vstabi.info/forum/read.ph...9944#msg-49944
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Old 12-23-2012, 02:56 PM   #6
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Quote:
Originally Posted by Primus View Post
9257 on tail, never measured the RPM as I've purchased the heli with the pinion on the motor.

Thanks for posting
Go with a full size tail servo.
Of course the gold standard is the Futaba BLS251.
I had a mini servo, and it just does not work out as well.

There is actually quite some force to move the tail blades in pitch with the hell running.
Disconnect your push rod from the servo and try it and see.
Be very very careful as you will be pushing the tail hard, you really need to hold it.
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Old 12-23-2012, 03:14 PM   #7
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I had the same issue with mine and I grounded the tail to the motor mount and fixed my tail wag.
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Old 12-23-2012, 04:03 PM   #8
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Quote:
Originally Posted by Primus View Post
9257 on tail, never measured the RPM as I've purchased the heli with the pinion on the motor.
Thanks for posting
Primus, I know that the 9257 "should" be good enough for the L400, but is not in my own experience.

I also began with a 9257, have tried a lot of mechanical setup variations as well as Vbar setup params with a super smooth tail pitch slider at different angles with 90° on the servo horn, could get good part of the wag off, but not completely!

I finally gave up and went to a full size Futaba BLS251 (fits with no mods) and voila, instantaneously tail rock solid, believe it or not!

Ricci.

PD: You are not the first person raising this same 9257 issue, I have seen others on Helifreak!
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Old 12-23-2012, 04:08 PM   #9
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Quote:
Originally Posted by pgleesonuk View Post
Go with a full size tail servo.
There is actually quite some force to move the tail blades in pitch with the hell running.
Disconnect your push rod from the servo and try it and see.
Be very very careful as you will be pushing the tail hard, you really need to hold it.
Don't test the Logo 400 running at ground and holding anything unless you disconnect the tail push rod. Even with the main blades off, at 2500+ RPM the tail throw gets very strong and causes real damage!

Ricci.
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Old 12-23-2012, 06:35 PM   #10
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Quote:
Originally Posted by pgleesonuk View Post
Always check for a super super smooth tail. Really zero friction.
MrMel says a bit of slop is better than any stiffness.
It takes time to achieve this.

I think a low wag if hover, and a poor tail in pitch pumps (looking like the pre comp values are wrong) is some stiffness in the linkage. Check everything from the servo horn backwards.

Also, as the 400 sensitive to vibrations, build it *really* carefully.
It is possible to get a vib free 400. It just takes time.
This thread has my experiences on the matter.
http://www.vstabi.info/forum/read.ph...9944#msg-49944
+1 !!!!!

I would also check on the balancing of both the tailblades and mainblades. Also check for bend spindle, main and tail shaft... You shouldn't have the vibration level from the first graph. Your last (without blades) looks fine, so start adding the blades one by one and see when the vibes are growing so you can solve step by step.

good luck
/ kurt
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Old 12-24-2012, 06:55 PM   #11
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Thansk guys for all the posts.

It's really scarry, on Idle 2 the wag is violent and once is started is very difficult to stop. Tried different gains, nothing. Take the tail rotor apart, everything is smooth, no bind.

I have a 9254 laying around that needs a gear replacement, will try that and see.

Wait, i have another idea!
Ordered a new kit from Readyheli!
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Last edited by Primus; 12-26-2012 at 09:34 AM..
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Old 12-26-2012, 09:20 AM   #12
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Hi again

Comming back to you guys with more details.

Checked for binding on tail. No frictions, tail shaft not bent, control rod and control assembly moves freely.

Redid the gear mesh on both pinion/maingear and maingear/tail with some piece of paper.

Tested again today.
Noticed that the wag is now starting only when loading the disc or left rudder input.

Arrgh!!
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Old 12-26-2012, 05:19 PM   #13
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Hi,
I had similar behaviour with my 400... at least if I understand you correct...
I found my 400 stable at a certain headspeed so you can play a little with headspeeds maybe ?
Another question , does the heli wobbles a bit on its own when you hoover, I mean can you confirm it is not the heli which is wobbling causing the tail to wag ? Consequently which swash servo's do you use ? I use savox servo's and had to eliminate slop between the potentiometer and output gear (very small piece of plastic) to stop the wobble/wag...

I hope you can solve it soon...

Kurt
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Old 12-27-2012, 02:06 AM   #14
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Hi Kurt

It may be linked to a too high speed as the first owner afirmed that it was running at 2800rpm. will try a lower HS today.
Will verify also the pinion tooth count.

When take off and hover the heli is not woble, no or very little wag. Then if want to flip it , or rapid collective input or any disc loading, or left rudder input the heli is starting to wag like hell !

Using 3xDS510/9257

Thanks!
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Old 12-27-2012, 04:21 AM   #15
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Hello , Bonjour ,

1/ 2800 HS is high but a lot of L400 are running in the 2200 - 2500 range. I run a 17T with a scorpion 3026-1400. At those HS maybe it is worth checking the motor bearings. If it was at 2800 you might check the O-rings of the head dampening.

2/ The DS510 is the same as SAVOX and a few issues have been reported with both servo's. Please check again for slop on the servo's. Put a plastic shim in the output gear to fix the potmetershaft ( strange but worked for me ) (see picture)

3/ You can aslo check the bearings of the tail gear ( see picture )

If this doesn't solve the problem :

- Remove Head and TAIL and run body on the bench --> check vibrations
- Mount tail , without head, without tail grips and run the heli on the bench --> check vibrations
- Mount main head, run on the bench --> check vibrations
- Mount tail grips --> check vibrations

The idea is to isolate the place where you should look for an issue step by step...

Bonne chance,
Kurt
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Old 12-27-2012, 08:30 AM   #16
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Default Testing for vibes

Testing as I speak

Take the both rotors off, and the entire tail assembly.

Checked the tail pulley, is moving free, no notchy feel on the bearings.

Main rotor ant tail rotors seems ok, I have not unmounted the grips but they are moving freely, no bind or slop.

When put everything in place put the boom at 90 deg with the main shaft.

I do have some slop on the servos too. Will be a PITA to unmount the 3 sevos for eliminating this. Good tip with the smal plastic piece, thanks so much!

Will try to change the tail rotor hub maybe, as the vibes leves is about 300 with tail rotor on.


Spektrum analyser:


No main rotor, no tail at all (boom, tail rotor):




Now with main rotor on, no tail at all (no boom or tail rotor)




Now with the main rotor, and the tail with belt and tail rotor shaft, but not tail rotor (grips and hub)




And finaly put the tail rotor on (no blades) and let the tail control rod disconected.

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Old 12-27-2012, 09:37 AM   #17
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Hi, 230 looks acceptable with everything mounted besides the blades. Before you change the tail hub, you may try to check if all bearings are properly seated and greased... as HF member "Maarset" mentioned, it is extremely important to have the tailblade grips moving freely...

Balance your blades, both tail and main...

The vibepeak around 3000 rpm isn't that big but you may want to check the one way bearing or pinion to maingear "backlash" to improve this. Set the backlash on the high spot of the maingear also...

Might be a lot of work but it will be worth it if you fly the 400 , and it isn't good weather to fly anyway, at least not 700 km North of you

/Kurt
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Old 12-27-2012, 10:35 AM   #18
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Thanks Kurt,

No flying time today here .

Both mains and tail grips are moving freely. Checked again.

Will redo the mesh gear, and will check my oneway bearing also.
In the vbar software I have noticed that my tail optimiser is at 92 and 10.

Ordered a set of the three axes, a 17T pinion and a complete tail rotor ( Mikado 3052); The good thing is that the tail is compatible with both 400 and 500.

Will let you know

Bonnes fêtes de fin d'année!
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Old 12-27-2012, 10:52 AM   #19
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One more thing i've forgot to mension.

When running without main rotor, saw the swashplate oscillating a little at full TH(due to a slop on the DS510 servos i think)
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Old 12-27-2012, 11:10 AM   #20
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Quote:
Originally Posted by Primus View Post
One more thing i've forgot to mension.

When running without main rotor, saw the swashplate oscillating a little at full TH(due to a slop on the DS510 servos i think)
I had same thing here and resolved that by eliminating the slop. The LOGO400 pilots who use the Futaba swash servo's don't seem to suffer from this.

You can lube the oneway with very fine machine oil or ATF ( transmission oil )

Let me know how it goes and I can readout some values from my L400 if you need it. btw I don't use tail optimizer in the VBAR...

Bonne chance et bonne fêtes !

Kurt
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