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Mikado
Other › High speed Tail Oscillation. Solved !!!
08-14-2010 11:01 PM  7 years agoPost 1
Busher

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Manchester, England

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Hi there !

Just got back from a test flight with my new logo 5003d, and I have a small problem.
When doing a turn in fast forward flight The tail oscillates in very fast small wags which is quite alarming and noisy in the air. It is as though the HH is working at too high gain, but the oscillation is there whatever the gain unless I really lower the gain value, thenit goes away but the tail will not hold in normal flight.
I have checked the usual stuff like slop etc and I have found the tail appears a bit on the sloppy side as per the pitch linkages, so there is not much I can do about that as it is how it builds.
The oscillation can also be induced when flipping the heli, but that went away when I reduced the gain a bit.

The mikado is bone stock 500 3d flybarred.
6s 5000mah lipo
scorpion 4020 910 17 tooth pinion
kontronik jive 100lv mode 11 selected
hitec 7966 cyclic
hitec 6965 tail
csm 720 gyro
spektrum dx7 ar7000 rec
hhp 550 razors
headspeed 1850 - 2000 depending on idle up condition oscillation in all modes but slightly worse at higher speeds
stock tail blades white plastic mikado's
Any pointers would be great. Other than this the heli is a peach and a definite keeper, so if there is a solution that will help I don't mind spending a bit of cash replacing parts etc, providing they are worthwile and not just bling.

Thanks

Good luck
Busher

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08-15-2010 01:20 AM  7 years agoPost 2
aviation

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Quebec Canada

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High speed Tail Oscillation.
What tail blades do you have, they may be a big problem if they are not carbon.

aviation

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08-15-2010 04:02 AM  7 years agoPost 3
NTM

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Lloydminster, Alberta, Canada

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It's definitally the tail servo, a 6965 is nowhere near suffecient.
They only work as tail servos on heavier, somewhat underpowered internal combustion helis, and even there not that well.
Get yourself a futaba bls251 and let the good times roll .

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08-15-2010 07:33 AM  7 years agoPost 4
lloyd

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Perth,Australia (South African)

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It could be the tail servo as I had the same thing but on a Align 620 on Vbar though.I lowered the gain right down to 45 and still no luck.Then lastly swopped out the servo for a BLS251 upped the gain to 85 and tail is now ROCK solid...

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08-15-2010 09:25 AM  7 years agoPost 5
Busher

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Manchester, England

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What tail blades do you have, they may be a big problem if they are not carbon.
The tail blades are the stock white plastic mikado's straight from the box.
It's definitally the tail servo, a 6965 is nowhere near suffecient.
They only work as tail servos on heavier, somewhat underpowered internal combustion helis, and even there not that well.
Its a possibility, I have used this combination on a raptor 50 and the tail was really good. will the BLS251 work with a csm 720? Are there any other servo suggestions?

Thanks for your help,

I have also now noticed the tail is quite sloppy, in general are the tails generally a problem on these heli's. The slop in the tail pitch linkages may well be causing an gyro induced wag, also there seems to be outward play on the tail blades when I pull out on them, there is the same play on both sides so I thought this was as per. Has anybody else got this sort of play on their tail blades?

Good luck
Busher

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08-15-2010 06:21 PM  7 years agoPost 6
s.kuronen

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Helsinki, Finland

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Busher, you need a CSM USB interface to choose short pulse width rate for BLS251.

I had recently a minor tail oscillation problem in my 500 3D flybar with CSM 720 gyro & JR 8900 servo. When I started to sort out possible reasons I noticed the servo got pretty warm. Then I found a bit of loose play in servo gears (must be due to a big tail hit I had), not much but apparently enough to have an impact on the gyro.

I replaced 8900 with Hyperion DS20GMD and got rid of oscillation. From my experience CSM 720 gyro doesn't mind having small linkage slops or vibrations but in order to work well it needs a very accurate servo.

BTW, have you tried flying vibration filter switched on?

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08-15-2010 08:07 PM  7 years agoPost 7
Busher

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Manchester, England

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BTW, have you tried flying vibration filter switched on?
No I haven't tried the vibration filter on as yet, I didnt think an electric heli needed one, but its worth a try.

I have flown the heli again today and the tail was performing ok, that was until I turned the headspeed up to 2100, then the oscillation could be found on FF flight. I also heard the tail blades make a noise just before the oscillation got bad. Are the stock mikado 85mm plastic blades suitable for over 2000 rev/min headspeed? Or do I need carbons, if so has anybody got any suggestions for tail blades?

I am thinking of a new bls251 on the tail, but Also upgrading to the Quick uk metal tail or the rjx set up that Jag 72 put on his, but before I invest heavily can anybody tell me if the stock tail is upto the job?

Thanks

Good luck
Busher

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08-16-2010 06:03 PM  7 years agoPost 8
Busher

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Manchester, England

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Can anybody tell me whether I can use 90mm carbon tail blades on my logo 500.
I am still struggling with the oscillation, and the only way forward is to try to replace parts one by one till I get a positive reaction from the heli.

I have at my disposal,

1 set of 85mm thunder tiger raptor 30/50 plastic stock blades which seem stiffer than the Mikado's.

1 set of 90mm Mah carbon tail blades these are pretty stiff along their length but I don't want to try them at 2100 if it will destroy my tail/heli. (if these are too big for comfort can anybody give me a pointer as to which tail blades are about the best on a 500)

After that I will move onto the tail servo, but I would like to try the blades and see if there is an improvement first. The futaba bls251 will be my choice for servo but at £90 its a bit of a hit.

Thanks for your help to date.

Good luck
Busher

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08-22-2010 07:00 PM  7 years agoPost 9
Busher

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Manchester, England

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Just got back from flying 5 packs out, and I have got a result on the tail oscillation.

It looks like a bit of quality control at the Mikado factory and possibly a bad blade.

I spent a lot of time looking at the tail and making adjustments to the tail rod and slider to eliminate as much slack as possible, this didn't help much, I went to my LHS who prescribed new gyro tape, and also gave me a set of NHP tail blades to try.

I was also not happy with the tail blade holders as they seemed to be sloppy on the hub. Whilst having a play with the blades I found I could pull them outward and inward in the holders, the slop was found on the blade bolt to blade hole, and the fit of the m3 nylock was sloppy in the blade holder socket. I re built the tail this didn't help so I decided to replace the bearings and the tail blade holders, this was quite a cost so I replaced the tail with the Quick UK tail for logo 600.

I added the NHP blades and went out to trim the gyro to the new blades and tail hub. The first flight was a good bit better and I was able to up the gain to a healthy 75% and the tail decided to behave, I put the heli into idle up 2 (2100 rev's) and blasted down the strip, all the oscillation had gone but I had a small wag from the gyro gain being a bit high, downed the gain to 70 did a quick trim reset and the tail is now behaving.

The stock plastic tail blades probably don't like being taken over 2100 revs and the slack fit on the bolt was a possible source of vibration, also the bearing fits in the tail blade holders weren't the best but probably adequate, The quick uk tail appears to be an improvement on design, but I think it also has a few probs depending on how you look at it.

Anyway I am flying now and the heli is a even smoother than before,

I like logo's

Good luck
Busher

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Other › High speed Tail Oscillation. Solved !!!
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