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450 Class Electric Helicopters 450 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar. |
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08-12-2011, 01:09 PM | #1 (permalink) |
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Join Date: Jul 2011
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450 tail vibration help!!!
I have a hk450 belt heli. had a hard tail strike and bought a new align tail rotor shaft. I still have bad vibration!?!?! The only way to stop it is to loosen the 4 bolts on the tail boom holder on the frame. as soon as I tighten it up. Instant vibration, and really bad, like I can hardly hold the tail boom! I bought a new tail rotor setup and the same thing, I visually inspected the belt for twists and it is NOT twisted. The only other thing I did was install a carbon tail boom. I tried several blades and many combinations. But the only way to stop the vibration is to loosen the 4 bolts?
Any suggestions for me? |
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08-12-2011, 01:27 PM | #2 (permalink) |
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Join Date: May 2007
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One thing you might check would be the bearings on the shaft. The strike could have damaged them or the tail case.
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08-12-2011, 01:36 PM | #3 (permalink) |
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Join Date: Jul 2011
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changed the tail rotor. Same thing.
I also want to note that when built and flown before the heli flew great with no vibration. |
08-12-2011, 01:48 PM | #4 (permalink) |
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Sounds like something is bent... did you check all of the shafts? Just recently I mysteriously bent a main shaft without crashing or having any hard landings... so who knows man... Also, are your mains and tail's balanced?
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08-12-2011, 02:31 PM | #5 (permalink) |
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Join Date: Jul 2011
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new align tail shaft and a new main rotor, without the blades on and no rear tail rotor, I can spool up to full power with no vibration. I dont have to hold the heli at all. with the paddles ballanced the main rotor is very vibration free. What i do is spool up and use a marker on the top of the head and let the heli mark where the out of balance point is, like balancing a tire. then I just adjust the flybar untill I get near 0% vibration.
when I install the tail roto with the shaft. no issue. Then I install the tail rotor without blades and little vibration, Install the blades and crazy vibration, this is with new blades. I bought 5 sets and cant get anything to work. the carbon push rod Im using vibrates so much it looks like a base string! |
08-12-2011, 02:56 PM | #6 (permalink) |
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Join Date: Jan 2007
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I had the same problem with the HK450 with the plastic tail case assy. Replaced with a complete new tail assy, including the belt, problem gone.
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08-12-2011, 03:26 PM | #7 (permalink) |
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Balance the blades!
You should be using a measuring device (such as a ruler or caliper) to set your flybar and paddles. If you get the measurements perfect then it will be more or less perfect... unless the part itself is flawed. There are many factors here... sounds to me like your heli may not be set up properly. Have you checked out Finless's videos? Also, if it doesn’t vibe without a shaft and does with.... that's a clear indication that there is a problem with the shaft. Remember there's a thing called resonance, certain objects will amplify a vibration, if the resonant frequency of those tail blades is the same or close to the teeny tiny vibe you are seeing, then that teeny vibe will be amplified considerably. You gotta be meticulous if you want the thing to be 'perfect'.
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~SAB~ Goblin 700 ~Compass~ Warp 360 ~Blade~ mCP X (BL) AMA# 977012 **Team BOCA Bearings** |
08-12-2011, 04:11 PM | #8 (permalink) |
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Join Date: Jul 2011
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I'm sure the heli is set up correctly. This wasn't the first flight or my first 450. The paddles are set even just a tiny adjustment of the flybar weight. I have the heli sitting on a table, no main blades and can spool up to 100% with no vibration or movement. I don't even have to secure the heli. Just sits there.
I'd rather not go off on a tangent about balancing. With no tail rotor, only the shaft. It is great, smooth and no vibration. If I add the assembly without the blades,vibration starts with blades, really bad, the tail boom support rods are almost invisible from all the up and down movement. If I do this without the main rotor and only the shaft I get the same thing. I have replaced the tail unit and the tail shaft. I'm open for any suggestions. Just want to be clear on the issue. I'm thinking I'll just replace everything from the main gear back |
08-12-2011, 04:57 PM | #9 (permalink) | |
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Quote:
After about 50 flights and a few brush-ups with the grass my stock 450 Pro tail blades needed balancing too, or my tail fin and control rod was like a noodle from all the vibrations...
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~SAB~ Goblin 700 ~Compass~ Warp 360 ~Blade~ mCP X (BL) AMA# 977012 **Team BOCA Bearings** |
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08-13-2011, 05:14 PM | #10 (permalink) |
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Join Date: Mar 2009
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I've got a vib in my tail ... sounds like the que for a song ... I've concluded that it is the bearings that are causing this (I have good cause to think that they have taken a beating).
However, I do struggle to balance the tail rotor (hub, grips & blades assembled) on my durbo balancer, as they are so light that it doesn't pick up any out of balance. How are you guys doing this? (photos would really help if possible)
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08-13-2011, 05:59 PM | #11 (permalink) |
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Join Date: Nov 2009
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Bad tail blade hub, tail grip bolts bent and washers under the bolts that attatch the grips are probably bowed throwing the ballance off. Take the hub with the grips attatched, line up the arms the links attatch to and hold them while rotationg the hub, you find the grips trying to wobble around whe you spin the hub. Next take the grip bolts out and watch for them to wobble when removing them, just replace them period and use two washers under the head of the new bolt, you'll find them bowed and that throws the ballance way off and replace the grip bearings if they are notchy feeling
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08-13-2011, 06:45 PM | #12 (permalink) |
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Join Date: Apr 2009
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"when I install the tail roto with the shaft. no issue. Then I install the tail rotor without blades and little vibration, Install the blades and crazy vibration, this is with new blades."
That's not very clear, but I think I get what ur sayin, so as mentioned before; *re-check main and tail blades for balance. *Change the main shaft bearings. *Spool up with no blades again and really look closely at the tail shaft- just because it's new doesn't mean it's dead straight, And it's quite deceptive when it is bent a little because it's all blurry when it's spinning anyway, and because it's such a high frequency vibration it doesn't always show up in the heli until you put the blades on- that's when it gets amplified. |
08-13-2011, 08:29 PM | #13 (permalink) | |
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Join Date: Nov 2009
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Quote:
Tear the hub and grip assy off and check like I posted. You will find more bent parts and don't dismiss the washers being bowed outward. |
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08-13-2011, 09:31 PM | #14 (permalink) |
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Join Date: Jul 2011
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I found out it is the hub or feathering shaft for the tail rotor. Spun it an the blade holders were wobbling.
Swapped out the rotor assembly and presto. Vibration is gone! Used everything exactly except the blade holder assembly so balance wasnt the cause. Bent blade holder hub. Thanks for the info. Last edited by bobbafett; 08-14-2011 at 10:37 AM.. Reason: spelling |
08-14-2011, 11:24 AM | #16 (permalink) | |
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Quote:
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09-07-2011, 02:28 AM | #17 (permalink) |
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Join Date: Jan 2011
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It sounds like i am having exactly the some problem. After a crash I installed a carbon tail boom. On first flight the vibe started and loosened the the tail support causing an emergency landing. I then replaced the entire tail case and tail drive. Still no fix. When I spool up with no tail rotors there is no vibe. Replaced tail rotors with another set and still no fix. Tried different belt tensions still no fix. I feel your pain.
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09-08-2011, 03:35 AM | #18 (permalink) | |
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Quote:
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