Logo 400 SE spec analysis

[galensk]

Originally Posted by Yoda DK

Hi

tested without blades. with bolts in and out. no vibes.
i'll remember your tip. wenn balancing tail rotor next time.


i haven't touched heli today.hate it already

Can understand that ! But don't give up...

So without blades you don't heave vibes ? then you should blance or investigate on the grips and bearings.
Looking at your log, besides some raised levels it doesn't look so bad. Do you have an idea where the cheksum errors come from ? VBAR points to a cabling problem or static...
/Kurt

[Yoda DK]

Originally Posted by galensk

Can understand that ! But don't give up...

So without blades you don't heave vibes ? then you should blance or investigate on the grips and bearings.
Looking at your log, besides some raised levels it doesn't look so bad. Do you have an idea where the cheksum errors come from ? VBAR points to a cabling problem or static...
/Kurt

Hi Kurt

i don't have vibes with out tail blades. i have a brand new tail rotor. i'll put it together and test again.. just not today. weather is really great and i want to fly my protos.. honestly i'm tired of using time on the logo.. mikado should have it back! think it's crasy that a costumor should use so much time on a brand new heli!!

the errors could be my fould. turned the radio of by accident

[galensk]

Any progress ?

[Kalpazan]

I've just finished building my 400SE and did some bench tests. I have the regular VBAR with sensor mounted on the bottom plate. Vibes are around 90-120 without tail blades and surprisingly to me at least, almost the same when I put the tail blades on (EDGE 72mm that came with the kit). I don't have the PRO version yet to see the graph but the max vibe level scored was around 220.

I did nothing special when built it. Didn't even used digital pitch tool to level the boom. Just pushed the boom straight and then backed off a little until that clicking sound appeared. Belt is not too tight, just like it is in the manual.

One thing I noticed is that stock gyro tape works even better if you do the Milton mod. Yet I removed it and put some cheap tape made by Henkel which made it work even better.

I tested it on 1900, 2100 and 2400 RPMs and the vibe level is best above 2000 RPM.

Btw, I have on of those tail boom support braces installed but I don't think that have any significant effect on reducing the vibe level.

[Bullfrog98]

Well here is a humdinger of an explanation of a vibe issue I was having with my 500 over the weekend. If you don't have the time/patience to read the small novel I have written below skip to the last paragraph for the short explanation.

Sunday after flying I decided to check the logs on my Logo 500 and was surprised to see a consistent hi vibration/extreme vibration warning every few seconds for the last 10 flights or so. The heli felt rock solid in flight, but you never know when it might freak out under those sorts of conditions so I decided to try see if I could at least reduce the problem.

I checked the vibes on the analyser (main blades off and the tail blades on) and found them to be around 1300 with peaks around 2000, all of this was happening around the 10000 rpm mark. With no tail blades the vibes were under 300. First thing i did was balance the KBDD blades I was running but they were fine. Tied another set of KBDD's and a set of Edge blades but always the same problem.

Next I fitted a carbon tail box I had lying around so I could fiddle with the belt tension (was running a plastic tail box). Making the belt tension looser or tighter only seemed to make the problem worse. I also tried a version of the Milton mod with no success.

Taking a closer look at the problem I noticed that everything was fine while spooling up and it was only at the last 10% or so of my intended head speed that the vibes got really bad, and it was not so much a vibration as a very high speed oscillation in the tail (almost as if the gain was too high on a very small scale) , in fact when I looked closely at the BLS251 tail servo I could see it was going berserk with very small high speed corrections.

In a last ditch effort I fitted some stock white Mikado 85mm blades and the vibes magically dropped from about 1200 to 300 and the tail servo was rock solid . Only difference I could see between the Mikado blades and the others I tried was that the Mikado blades were a bit beefier (thicker) and much heavier than the other blades.

Anyway to cut a long story short I highly suspect that the vibration problem was V-bar related and not mechanical at all. Perhaps my tail gain was just a smidge too high for the lighter blades or perhaps the dead band for the tail needed to be increased slightly but once the tail got up to full rpm it was making very small high speed oscillations that could easily be mistaken for vibrations. So if you are having vibe issues even though mechanically everything seems sound it might just be the V-bar.
I am by no means a V-bar pro so perhaps Mr Mel can give more useful input regarding this effect and what might have caused it?

[Yoda DK]

Hi Guys

i'm on hold i just switched to a new radio. and i'm wainting for a new RX for the logo. but wenn it gets here. i'll try messing with it again..

Kalpazan: i wish my build was as simple as yours. but i'm glad to hear that a logo 400se actually can get low vibes. now go fly that thing

Bull: good you got rit of the vibes. must have been your tail blades. since it was the only thing you changed

[Bullfrog98]

Well by sheer luck changing the tail blades did fix the problem, but I'd love to know what the root cause of the problem is as it definitely was not mechanical.

Like I said in my post above the tail was oscillating with the lighter blades as if the tail gain was too high (but it was not).

I highly suspect that the vibe issues being experienced buy people in this thread with perfect mechanical setups can be cured with some minor v-bar tweaking, I'm just not sure what the problem could be.

[galensk]

Very interesting information indeed ! Anyhow it shouldn't be too difficult to do some minor tweaking and see how the vibes behave in the spectrum analyzer.

[Yoda DK]

i'll try and tweak the vbar. when my rx arrive. haven't touched the logo for a few days. i also need to mount the new tail rotor i bought for it. almost scared to spool it up again and to find out that the new tail rotor don't make a difference..

[maarset]

My biggest struggle with logos is the tail grips. The grips must be extremely smooth. They should spin endlessly on the tail hub when disconnected from the tail slider.

If this is not the case you will get a mean tail vibration when you put tail blades on it.


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[Yoda DK]

Originally Posted by maarset

My biggest struggle with logos is the tail grips. The grips must be extremely smooth. They should spin endlessly on the tail hub when disconnected from the tail slider.

If this is not the case you will get a mean tail vibration when you put tail blades on it.


Sent from my iPhone using Tapatalk

thanks maarset. i will make sure they are really nice and smooth. should they have a hair of play. or no play at all?

[maarset]

If you grab each blade grip and try and pull them off of the tail hub there will be some outward play.
You don’t want those tail hub bolts tight. Just snug with Loctite.

I can’t begin to tell you how many countless hours on the bench with the vbar unit plugged into the computer using the vbar software to get a low vib reading with my logo 400. It drove me insane!!!!!! I was trying EVERYTHING!

At one point I put on a Trex 600 tail hub and grips and had very low vibs. I had no problem getting that setup nice and smooth. But I really struggled getting the Mikado tail grips nice and free. If they are even slightly notchy and don’t spin like a top you get issues.

The key is to make sure the tail grip bearings are assembled correctly and those bearings are seated into the grips properly.

And again the best test I did was disconnect the tail grip from the slider and with the tail blade removed, flick the ballend on the grip with your pointer finger and see if it spins like a top. If it only rotates a couple of times you have a problem. IMO IMO IMO.

[Yoda DK]

thanks alot maarset! i think my grips are smooth. but i'm not sure they are smooth enough now. i will check them and test them before i put the new tail rotor on. maybe this could cause my nasty vibes

[egaus]

Interesting. I've taken both my tail assemblies apart and reassembled them several times, they seem pretty smooth. Spin like top? Mine aren't that smooth. What's the trick? One of mine has a tiny bit of play when you pull the blades, the other not. Both have the bolt screwed in just enough, not tight.

Just went and checked mine - they could not be smoother. Oh well.

e

[maarset]

Originally Posted by egaus

Interesting. I've taken both my tail assemblies apart and reassembled them several times, they seem pretty smooth. Spin like top? Mine aren't that smooth. What's the trick? One of mine has a tiny bit of play when you pull the blades, the other not. Both have the bolt screwed in just enough, not tight.

Just went and checked mine - they could not be smoother. Oh well.

e

You need to double make sure the inner bearing is fully seated. Not knowing any better I would sand down the copper shim to get the right spacing to get the grips super smooth. But after flying for a while the bearings seated fully and I had even extra outward movement of the grips.

[Yoda DK]

i have just pulled my tail rotor apart. they would not spin like a top. but they were smooth. i double checked that bearing were fully seated. and then i re-greased the thrust bearings. bolts are just snug. i have a tiny bit of play in one of them. but they really spin nice and free now. when spinning them i think they spin 5-10 thimes before they stop.

[maarset]

Originally Posted by Yoda DK

i have just pulled my tail rotor apart. they would not spin like a top. but they were smooth. i double checked that bearing were fully seated. and then i re-greased the thrust bearings. bolts are just snug. i have a tiny bit of play in one of them. but they really spin nice and free now. when spinning them i think they spin 5-10 thimes before they stop.

Ok that sounds good. Should be good now

[egaus]

Yoda - Did you spool up? Any difference in vibes?

e

[Yoda DK]

hi e

no not yet still waiting on the rx for my new radio.then i need to set it up in the radio to. so it will be a couple of days before i can test it

have you tried it out. or is your 400se sold?

[Yoda DK]

Originally Posted by egaus

Yeah.. But I need a flying 500 size heli or else I might go and buy another, yikes.

Here's some pics, camera sucks and everything is really straight (lens distorts some). The gear mesh shown actually has less backlash than it looks (it is more loose). I run a strip of paper through it and it looks good.

e

i was looking at your pics. only thing that i can see is missing. is the belt tensioner on top of the belt. you know the 3 bearings?