Logo 400 SE spec analysis

[JohnDoe.]

The tail drive gear I take it you have the shims on it ? if so how much vertical play does it have ? Again it's a long shot but now we have to rule it as something small since you did everything. how old is the kit and did you ever crash it ? I know you probably answered these questions

[egaus]

I have the shims on. I've replaced the entire assembly. Vertical play is almost none.

Summary:

Built the Logo 400SE, did not purchase pro Vbar. Flew the Logo 400SE approx 5 times. Last flight, it flew itself, I hard auto'd into grass. Not much damage. Bought some parts, moving parts, non-moving parts. Started to rebuild, bought Vbar Pro, saw bad vibration events in the log, spun it up the the bench with spek analysis and saw a bad spike, felt a bad vibe with my hand on the boom (have used two new booms). Started this thread. I feel bad it has gone on this long.

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[egaus]

Hi, took some photos, thought it could help.

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[Bullfrog98]

Mmmm.... I see you are not running an idler bearing over the top of the tail pulley, any reason for that?
I don't know if that would affect the vibes at all, but it should still be there, it might add a little extra rigidity/stability to the rear part of the tail assembly.

[Kalpazan]

I noticed the idle pulley actually induce more vibes although not much. It however allows a bit more loose belt which is better for the tail bearings.

[egaus]

Idler bearing no longer comes with the carbon tail, RH site says it is not needed.

http://www.readyheli.com/MIK3062-Car...0_p_35262.html

It is pictured, but noted at the bottom of the page.

Tightened up the belt, will run a test to see if that offers any improvement. It was not 'loose' but the manual says 'belt should be tight' so tight it is.

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[maarset]

Originally Posted by egaus

Idler bearing no longer comes with the carbon tail, RH site says it is not needed.

http://www.readyheli.com/MIK3062-Car...0_p_35262.html

It is pictured, but noted at the bottom of the page.

Tightened up the belt, will run a test to see if that offers any improvement. It was not 'loose' but the manual says 'belt should be tight' so tight it is.

e

Do you think maybe the belt is rubbing on the boom every once in a while and causing vibrations? Belt looks awfully close to the boom.

Also is the CF tail unit perfectly parallel and the tail output shaft not binding?

I found with my CF case I would put slack in the belt and then re-tighten the CF case and check to make sure the tail output shaft is bind free. Just a thought

[egaus]

At this time I think that the belt is rubbing either itself or the boom. At work presently, but will test later. CF tail looks spot on, tail output shaft/slider is smooooth. Thanks!

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[egaus]

Tighten belt = no better, maybe worse.

I'll try checking the output shaft by putting some slack in so the belt is free.

Since the problem has existed with both CF tail and stock, I'll stick w/ the CF for now.

Does the freq. and RPM in the spektrum pic below really seem to indicate motor? I would think that ~10,000 RPM would correspond directly to the tail as the tail spins 1:5 ?

spektrum pic: https://www.helifreak.com/attachment...7&d=1336843412

Vibration is loud and dull/low, don't even like spooling it up. Quick UK tail does not stay centered on its own, tail pushes hard CW. I have to hold the boom. (Tail control rod disconnected).

Also, I have the boom all the way in the forward block, adjusting belt tension at the rear.

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[Kalpazan]

I played a lot with the belt tension and I know for some it works tight but I prefer it loose as much as possible. If it is too loose it will warm the boom. If it is too tight the tail bearings will get hot real quick. Same if the output shaft is not exactly parallel btw.

One test I do is, when you mount the boom, back off the motor and spool the main shaft by one hand while holding the boom with the other. You will feel if there is any excess tension or something that is may be rubbing here and there. Even if it happens rarely it will be amplified once it is running at full speed.

Then, try to play a bit with the RPM. Sometimes that may reduce the vibes a lot.

[agagescu]

That looks like TR to me. Was that with tail blades on? Does anyone know of another way to determine between resonant vibrations?

Like kalpazan suggested, vary the the RPM to see what effect that has. But since you're holding the tail boom that will provide some dampening and change the resonating frequency anyway.

Rather than leaving the tail pitch control disconnected, you can remove power from the tail servo and it should hold the position. Careful though it can still get away from you. Ask me how I know

What HAVEN'T you changed on that heli? The motor, pinion, OWB?

It would be nice if someone from Mikado hung out on these forums and chimed in on this!

[Bullfrog98]

Have you checked the drive gear end of the boom.

I had a bad crash once that not only striped the main gear but also messed up a few teeth on the tail belt drive gear.

The damage was fairly minor and not that easy to see but man did it create a lot of vibes.

[maarset]

Originally Posted by egaus

Vibration is loud and dull/low, don't even like spooling it up. Quick UK tail does not stay centered on its own, tail pushes hard CW. I have to hold the boom. (Tail control rod disconnected).
e

When I used the UK tail on my logo 400 it would want to pull CW hard with tail push rod disconnected.

Have you balanced the whole tail unit with a magnet prop balancer?

Are you just getting a max vib of 700 on the bench? If so that is borderline ok for a logo 400.

[maarset]

The only other thing I can think of is send me the bird and I can take a look at it. LOL!

[egaus]

Thanks for all the input guys, I'll give it a go with the suggestions above.

All the gears are new, tail unit is balanced as a whole.

I've replaced just about everything except OWB, Motor. Pinion is new 17T. Maybe try a different one so I can run my throttle curve further up, 52% is not the best.

Maarset, PM me your address, I'll send it. No joke.

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[agagescu]

I've got a 22T mod 5 pinion and a scorpion 4015-1070 you can borrow to try. I can even send you my OWB but it's not new. At least you'll have changed everything on it at that point.

I flew a buddy's L400se. He's having the same issues you and I are. He's changed just about everything and then gave up. Now he flies it with zeal below and above the sensor strapped down with Velcro. Yikes! It flew but it just didn't feel right.

[agagescu]

And a BNIB belt too.

[egaus]

Ha! Wel'll see... Anyway, can I spool up the motor with no load on it w/o harming it? All the way? (equates to about 52-60% TH)

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[maarset]

Originally Posted by egaus

Ha! Wel'll see... Anyway, can I spool up the motor with no load on it w/o harming it? All the way? (equates to about 52-60% TH)

e

That won't hurt the motor. Spool it up to idle2. Take a screen shot for each test if you can.


Sent from my iPhone using Tapatalk

[egaus]

Motor only, spooled up to IU2. Vibration is virtually non-existent. I will do next with pinion and main gear spinning, no tail. This is a good idea.

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