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Logo 400 › Logo 400 vibration level on vbar5 spectrum analyser
10-12-2010 05:19 PM  8 years agoPost 1
Bugcatcher

rrApprentice

Perth, Australia

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Hi, just quickly.

Been trying to troubleshoot a vibration problem on my Logo 400 that I think may be causing my blue mini-Vbar to act weird in that it drifts left alot and has quite alot of tail wag. So much that I have to drop the gain on the tail right down to 65%.

I spooled up the heli on the bench without main or tail blades and the spectrum analyzer showed a maximum level of about 700 with a spike at the 11k or approx 200Hz mark indicating a problem with the tail.

I then spooled up again with the tail blades on and control rod disconnected as MrMel suggested in one his video's and the vibration level was off the chart at well over 4000. With the spike roughly in the same position.

I'm using Radix 72's on the tail and have since balanced and will try them again tomorrow night.

The question I have is. What Vibration level in the spectrum analyser should I be aiming for so it doesn't either affect the vbar or put undue stress on heli overall.

Is 500 or even 1000 a good level I should be aiming for while the heli is spooled up on the bench??

Thanks,

Andrew.

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10-12-2010 07:32 PM  8 years agoPost 2
MrMel

rrProfessor

Gotland

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Below 500 with tailblades, but that can be hard, below 900 and it will probably fly ok.

4000 is catastrophic.

Cracked tailcase is a common one.
Unbalanced blades too, i discarded 3 set of radix blades..

Gone fishing..or hunting..or something
My site: http://heli.dacsa.net - VBar videos and more

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10-12-2010 07:44 PM  8 years agoPost 3
Chamarro

rrApprentice

Villahermosa, Mexico

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Unbalanced blades too, i discarded 3 set of radix blades..
Me too!! Used to have big spikes on my L400 with radix, then I switched to the plastic stock tail blades and problem went away!!

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10-13-2010 02:53 AM  8 years agoPost 4
Bugcatcher

rrApprentice

Perth, Australia

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I guess I just took it for granted that buying a good quality tail blade I wouldn't have to worry about balance problems.

I actually had 3 sets of Radix at home and all three were out of balance! The new sets I had I then checked the CG which were within 1mm small enough I couldn't tell. I then paired the heaviest and lightest together and just sanded the end slightly to bring them into balance. Didn't have to take too much off and will try again tonight.

MrMel, i've just changed to the upgraded carbon tail case which may be better or causing more vibrations as it is possible to get some slight misalignment with how it's designed.

I've also used the extra gyro plate brace from custom heli parts to try and reduce the vibration levels around the vbar.

I will try a few more things and post my findings.

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10-13-2010 06:58 AM  8 years agoPost 5
whaleboy

rrApprentice

Los Angeles, CA

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I'm fighting the same. Flies fine but recently started lifting off with a major tilt. Analyzer had the exact same readings... 4000ish in the tail. Had the same trouble with the tail gain, I think I'm down around 55. I'm using the stock blades and they are identical in weight, but I haven't checked the CG.

I did notice a ticking when turning the main rotor by hand. Took the boom assembly off and the sound is coming from the front. If I loosen the belt, everything feels glassy smooth. The bearings all feel good as new, but realized that only when the front bearings had belt tension did I start to hear the clicking sound, so I can only assume the issue was a bad front bearing. I have replacements on the way. I should know later this week if I can get out, or the weekend for sure. I hope that's it... everything else seems good. The heli doesn't have a tone of flights on it and its never been crashed.

I really wish the Vbar had a way to record the flight vibrations. It would make the analyzer a lot more useful.

-David

Synergy N9; E-Aurora; Logo600se; Logo500; Logo400;Trex500;
All FBL..

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10-13-2010 08:38 AM  8 years agoPost 6
anjki

rrNovice

northants,uk

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myself and another club member have had this very same problem.

check your tail hub bearings can slide on and off the hub without force.use some wet an dry paper to reduce the diamiter if needed.
its sounds like your bearings are locking up under load.

andy k

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10-13-2010 02:59 PM  8 years agoPost 7
Paul Gleeson

rrApprentice

Bonn, Germany

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I'm in the same boat trying to chase down the vibrations at the tail rotor RPM. Apparantly this is really common with the Logo 400 / 10.

I was very careful to adjust the tail drive gear mesh, and I did this without the boom fitted, just with the belt loose not engaging.

It is really easy with the design of the 400 tail support to cause intentations in the main frames where the 8 bolts go, and you loose fine adjustment as they always slide back to the same place.
So I got some new frames to solve this.

Then I fit the boom (easy if you loosen the bottom rear bolts) and tail. Checking each time I add a part there is no additional vibration.

I balanced my whole tail hub a blades together using a magnetic balancer (zero friction)

This is the best I can get

I have heard the main rotor gain on V5 is higher than for V4 with the name number, so I am reducing this to 40 to start with.

Hopefully test hover tonight

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10-13-2010 04:41 PM  8 years agoPost 8
Bugcatcher

rrApprentice

Perth, Australia

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Paul, that's awesome. Really got the vibrations down to a really low level for the Logo 400.

Are you using an extra gyro plate across the sideframes as others have recommended?

Also, just a quick update. Tried spooling up the heli again with the whole tail hub/blades balanced as best I could. The heli or more importantly the tail, registered a vibration level above 4000 and was very difficult to keep hold of.

Noticed this time as well that the swash did a few weird twitches when head speed got right up there when the ESC was pushing out over 90% throttle to the motor. Will be try fitting a new tail hub and shaft while checking for binding as the next step. The move forward to the counter gear and bearings then finally the mainshaft and bearings.

Going to be a really good exercise actually to analyse what components affect the vibration rate and what signs exist for different symtoms.

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10-13-2010 07:29 PM  8 years agoPost 9
Paul Gleeson

rrApprentice

Bonn, Germany

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Yes I have the CHP plate, and I'm using Zeal tape.
Maybe overkill for an electric heli.

I think I might have nailed my problem. But it's too late / dark to hover now.

I was still getting high / extreme vibration warnings in the flight log.
I did hook up the laptop and get a spectrum with the blades on, and I had "sea grass" across the whole spectrum.

This indicates a gear mesh problem, and after taking a close look at my motor pinion it did have a slight wobble. Changed it for a different one, and it all seems much smooth than before, and my spectrum is even better now.

Fingers crossed for the test hover tomorrow.

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10-13-2010 07:47 PM  8 years agoPost 10
Paul Gleeson

rrApprentice

Bonn, Germany

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Here is my new spectrum

The total value may not be so different, but the peaks are much sharper, and other parts of the spectrum are much lower.

Hopefully this time I've nailed it.

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10-15-2010 06:01 AM  8 years agoPost 11
Bugcatcher

rrApprentice

Perth, Australia

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Okay, quick update to what i've tried without success. :-(

Last night I firstly got a reference figure of ~4094 with blades and ~600 without.

Before I go on, as I spool up the vibs seem okay up to about mid throttle at arount ~1000. Then again about ~1500 at 75%. When I crank the throttle to 90-100% the tail goes crazy at over 4000 on spectrum analyzer.

I then changed to the stock plastic tail blades and vibs were reduced down to 2100. I then put on a new tail hub that I sanded to free the bearings with the plastic tails, +1950 vib level.

Tried a new set of Edge 72 tails, back up over 4000. Which make sense as carbon's are stiffer and don't absorb any vibrations.

Then I installed a new tail shaft, A slight reduction again but nothing major. ( At this stage I was getting a little confused and frustrated.)

Next tried fitting a new counter gear/bearings and housing. No change, did play with belt tension a little, at first had it slightly on the loose side as you nearly press it together at either gear. Then tightened it and vibs were reduced overall from idle to 75% throttle with a tighter belt.

The final change last night was to replace the upgraded carbon tail box with a new original plastic one. No change, still over 4000 vibration level with carbon tail blades at 85-100% throttle.

To be continued, will now replace the main gear and one way with a new ones and install a hardened mainshaft.

Will let everyone know how I go. Should have posted a screen shot of spectrum analyser. Will do tonight before I try anything else.

Thanks,

Andrew.

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10-15-2010 07:45 AM  8 years agoPost 12
Paul Gleeson

rrApprentice

Bonn, Germany

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Do you have a magnetic balancer you can put your tail hub and blades on? I was surprised just how far out my edge tail blades were.
Took about 1 square inch of tape to balance them!
Since then I'm using the stock tail blades which are much much closer.

I now have consistent "raised vibration" messages rather than "extreme vibration" so I'm getting there.

The heli now wobbles in the hover, so I might change the Zeal tape back to normal tape as the Zeal tape is 1/4 inch thick and very flexible.

I'm sure we will get there.

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10-15-2010 10:18 AM  8 years agoPost 13
Bugcatcher

rrApprentice

Perth, Australia

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Hi Paul,

I have balanced the hub and blades. I didn't balance the Edge tails but did balance 2 sets of Radix's as a pair on there own on a balancer and again together on the hub. Still didn't make a difference.

I have a feeling it may be the main gear which may be warped. I could have been caused by me over tightening the screws to the one way. Will be my next try. Got the head of will give it a quick try like that out of curiosity then change the gear. I have Mod 0.7 gears to try as well which could be on the cards as well.

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10-16-2010 05:39 PM  8 years agoPost 14
Paul Gleeson

rrApprentice

Bonn, Germany

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New Mikado motor pinion and the stock 2mm foam tape works a treat.
No vibration warnings at all.

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10-16-2010 08:06 PM  8 years agoPost 15
Andy from Sandy

rrElite Veteran

Bedfordshire, UK

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Bugcatcher, do you really think a figure in the 600s is really awesome? If you take the advise of anjki you might be suprised how much better you can get the tail.

I have been playing around with different bits and parts and now have the vibration figure on my Logo 500 down to 150 from a figure around 1500.

I did have a figure of less than 100 when using the stock tail and KBDD blades but it didn't last long and the figure started to climb after a short space of time.

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10-17-2010 04:36 PM  8 years agoPost 16
Bugcatcher

rrApprentice

Perth, Australia

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Andy, you can't really compare the Logo 500 to the 400. From what I have personally seen and also online. The 400 due to the mounting location and the way the frames are setup you will always get a higher vibration level than the Logo 500. If your getting 150 that is definately awesome as well. Out of curiosity, at what headspeed was that? And at what throttle?

I have been told by Mikado that anything under 1000 for the Logo 400 is acceptable with around 900 being the norm. To get down to 600 and below you are doing very well.

I have tried what anjki suggested and didn't make any difference in my case. The bearings were a little tight but were never locking up. I did sand them down even more and were sliding easy. Had 2 different complete hubs and tried them one after the other with no significant differences.

I did change the belt last night as someone did mention there was some problems with a few belts. Few it today with plastic tail blades and did fly okay. Will run it up on the bench to see what vibs there are now. The only other thing I can try is to fit new main frames as it's hard to adjust the meshing like Paul mentioned earlier. The bolts when tightened cause depressions and make it difficult to adjust the meshing after. It's about the only thing I haven't changed.

If I do I will probably take the same path as Paul in trying the spectrum analyser each step and try to get everthing at the lowest level possible.

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10-17-2010 06:45 PM  8 years agoPost 17
Andy from Sandy

rrElite Veteran

Bedfordshire, UK

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The headspeed at the time of the test was 1940. I am running a 4020-1100 and a 13 tooth pinion. The throttle percentage on a Jive 100+LV is 81%. The headspeed wasn't set to anything in particular it just happened to be that after I switched from a 14 tooth pinion.

I have not done any reading on the analyser so I have no way of knowing what is good or bad or what the figures actually mean. It just seemed logical to me that high figures were not good but then what constitutes a high figure?

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10-17-2010 06:56 PM  8 years agoPost 18
Paul Gleeson

rrApprentice

Bonn, Germany

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I think it also depends where on the spectrum it is.

What was causing me problems was the low level of vibes across the whole spectrum. Which when the motor was loaded with the blades.
You could not see this just running the tail blades with 0 pitch on the bench.

You can see most of the spectrum is below the yellow line, but right across the spectrum.

After I changed my pinion, I would run on the bench with the heli held very firmly, then rotate it pushing hard against the tail rotor.
Be careful have have a long USB cable well out of the way.

This loads the motor, and any problems may show up more

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10-17-2010 07:55 PM  8 years agoPost 19
Andy from Sandy

rrElite Veteran

Bedfordshire, UK

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On my tests there is just a single high spike around 300Hz, the rest is pretty flat at a very low level.

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10-17-2010 09:05 PM  8 years agoPost 20
Paul Gleeson

rrApprentice

Bonn, Germany

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This spectrum was with the main blades on the ground.

The repeated spikes were a sign of a gear mesh problem.
When I ran it just on the bench, I also had just a peak at about 300hz.

Putting the load of the main blades and negative collective was enough to show the problem.

If you want to at least to put some load on the motor. Push against the tail.

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