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Home✈️Aircraft🚁HelicopterSynergy R/COther › Question about head speed and wobble issue
06-03-2011 03:42 PM  9 years ago
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theviper

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Gilbert, AZ.

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Question about head speed and wobble issue
Ok, I bought my N5 used from a team Synergy pilot. The bird is AWESOME. But this is my first N5 and I have an issue I want to address..

I flew the bird for the first time last weekend. It is a flybarless bird and setup was easy.. I have my governor set up so no use on normal. ST1 is at 1850 and ST2 was at 1950. These are the head speeds I like to fly on my T600 so I figured it was a good place to start..

I popped the bird up in the air and she started to wobble left to right. (We call it the Hula dance.) Ok, figured the head speed is a little low, I have seen this before on my T600 with tight head dampeners. No problem, I land and increase the throttle curve some.. Again in the air. same dance. I punch into ST1. 1850 now. same dance.. Not looking too good. My friends are all saying there is a bent spindle.. Hmm, I punch into ST2. 1950 now. same dance.. So I land it..

We put it on the bench and pull one of the blades. Using an Allen we turn the spindle and observe the remaining blade tip.. We all look at it and decide the tip is moving up and down and therefore decide the spindle is bent.. Ok. I give the previous owner a call.. Now, let me say this, the previous owner is a REALLY nice guy. he gave me a REALLY, REALLY good deal on this bird, If I have to replace a spindle. I am in NO WAY disappointed or upset. Not a big deal at all. He has been EXTREMELY helpful in the setup process of this bird and has helped me the whole way. So I was just going to call and tell him she flies but ran into a LITTLE issue.

I talked to him and told him what we suspected. He said that was weird as he had just flown the bird a week prior with no notice of a shake. He did tell me the bird had been crashed before I bought it. but it was all repaired and had been flown several times before shipping. He said my head-speed must be too low and I need to crank it up to about 2150. He said the N5 has a very tight FBL head and is happy at high head speeds.

I decide to try it out one more time. I start up the bird and calculate what 2150 would be in ST2 and pull her into a hover. the wobble is there again at normal and ST1. But sure enough, I pop into ST2 and she is smooth as silk.. I fly the bird 2 tanks and enjoy the rest of the day with it.. The head is SCREAMING and a little scary. But killer power.

HERE IS WHERE IT GETS A LITTLE WEIRD...

After the day of flying, I clean my birds for storage. While the N5 is on the bench, I decide to pull a main blade and again test the spindle.. I place the remaining blade tip in contact with a spot I make on the wall with a sharpie. I then attach my 4mm hex bit to my cordless drill. I add a couple drops of lube to the spindle for easy turning and so I don't heat up the dampeners. I start the drill turning a little slow. and watch the tip. Sure enough, the tip goes up and down with the rotation. This is a sure indication something is not right.. So, I finish cleaning everything and go in and order a replacement spindle..

Yesterday, the new spindle arrives. I quickly pull the old spindle out and decide to do the old role test. I role the spindle across my kitchen counter top.. Weird. It does not appear to be bent at all.... Maybe I just can't see it. I go ahead and replace the spindle..As I am mounting the blades. I decide to do the drill test again. I again align the tip to the spot and turn the spindle. The blade tip STILL MOVES UP AND DOWN.. WHAT THE HECK IS THIS??

Ok, so there is my story and I am sticking to it.. Why does the blade tip still move up and down when turning the spindle.. WHAT could be causing this and why does the bird dance at lower head speed?? The tip moves about 1/4 inch or so up and down. Not a LOT. but noticeable.

Sorry for the LONG BOOK, but I want to be detailed and clear so someone can help me with this issue. Could a blade grip be bent or milled bad? Bad bearings? They all looked OK to me??

Thanks for ANY help,
Viper
Team Synergy RC.
Team Scorpion. Team Magnum Energy.
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06-03-2011 04:04 PM  9 years ago
thenewguy

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Corvallis, Oregon Where there is liquid sunshine!

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What FBL system are you running?

Thanks,
Chris
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06-03-2011 04:10 PM  9 years ago
theviper

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Gilbert, AZ.

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Using BeastXTeam Synergy RC.
Team Scorpion. Team Magnum Energy.
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06-03-2011 04:15 PM  9 years ago
Raffy

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Chicago, Illinois

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The dampners are not truely rounded.
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06-03-2011 04:25 PM  9 years ago
thenewguy

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Corvallis, Oregon Where there is liquid sunshine!

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One thing to keep in mind, just because something shows up new in a packages does not mean it straight. Also a roll test on a counter is not a good way to test for a bent spindle. The proper way to test a shaft of any type is to dial indicate it while it sets in V-blocks. You should also check the main shaft.
I decide to do the drill test again.
How do you know that the drill is spinning true and not inducing the issue you see? I would not trust this test.

Have you taken the whole head apart and inspected everything? All the bearings? Also does it have the correct shims or stock shim that come with the N5. Should be 1mm shims close to the dampeners.

I am not familiar with the BeastX, but from my understanding they are really easy to set up and use.

Wobbles or shakes can be caused by many issues. First you need to make sure your heli is mechanically sounds before moving to electronics set up.
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06-03-2011 04:35 PM  9 years ago
theviper

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Gilbert, AZ.

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I agree with everything you have pointed out. However, we use what we have to do what we can.. That being said. I am mainly looking for Ideas here which you have provided nicely. As well as anyone that has seen this issue themselves.. Also, Does the N5 require a higher head speed? Or is this a result of the head issue??

The correct spacers are present ad I have taken the head apart to inspect it to the best of my ability. The dampeners do not seem to be worn or out of round from what I can tell.

Does anyone else run a FBL N5 with head speeds around 1850?

Thanks,
Viper
Team Synergy RC.
Team Scorpion. Team Magnum Energy.
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06-03-2011 04:46 PM  9 years ago
thenewguy

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Corvallis, Oregon Where there is liquid sunshine!

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From what I have seen on my N5 and several other friends N5, when the head dampeners are new they take awhile to break in. Mine took about 3 to 4 gallons before my wobbles went away at lower RPM's. This is when my N5 had a flybar though.

I would say that the N5 likes a higher head speed. Mine are as follows

1750 1850 2000

I hardly ever fly around in the lower head speeds. When my dampeners where new I would get a little wobbling in the lower head speeds. Now that they are fully broken in I do not see the issue at all.

Pm sent.

Thanks,
Chris
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06-03-2011 06:56 PM  9 years ago
Bogdan

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Netherlands

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Hi Viper,

One way or another, this problem can be solved. Hope that it will not take you too long.

I had also some doubts on the fabrication tolerances of the blade grips or of the hub (as reported earlier). However, it turned out that my helicopter had no noticeable wobble above 1900rpm. It is a very robust and responsive head.

Non-expert ideas (steps to follow):

1) the optimum needle settings could be different from low RPM values to high ones. Just check that your carburetor is tuned properly in the range you intend to use it.

2) make sure that the 3axis gyro sensor is well insulated against engine vibrations. This might be critical depending on the sensor design. Compare how your FBL unit is mounted with others that are known as working properly. Do a search on google-images.

4) make sure that all metal components of the head are in good condition. Clean the bearings and grease them.

3) if you suspect that the dampers might be the cause of low frequency vibrations and you do not have some used ones to trust then order new ones and start from there. It can be that the dampers were hardened during the storage. It can be that the grease used for lubrication is just not compatible with the dampers material. I have seen this effect on my old raptor after 6 weeks of storage. So I would just buy new dampers. Clean all components and add grease not only to the bearing; grease the dampers too. Add grease between the dampers to lubricate during the flight. Check if any improvements can be noticed.

4) once you have the new dampers play with the thickness of the metal shims. One of the functions of these shims is to compress the dampers (stiffen). I would look for thinner shims and a little thicker too. If you see that you have lateral play while translating the blade grips the shims are too thin. If you increase the compression and the wobbling effect does not change significantly at high RPMs then there could be other parts to be considered. Check all “low frequency” rotating parts like ball bearings of the main shaft.

If you are in the mood, do a systematic check. Document and eventually take pictures. Let us know how you solved the problem.

Thanks!!!
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