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Old 03-20-2012, 11:05 PM   #1
SynergyAero
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Default Squeaking and slapping

I finally got my Goblin completely built, all electronics installed and configured!

I noticed a few odd things after doing a quick hovering session...

1 - When the heli spooled down, almost to a stop, I noticed a squeaking coming from the main gear area. Sounds like a creaking door. I can slowly rotate the rotor head by hand and hear the squeak at certain places along the rotation of the gear. However, once the heli cools down the squeaking goes away. Then if I warm it up again the squeaking comes back. I did put the thin (WD40-like) triflow oil on the gears to aid in break-in. Perhaps a real flight or two is necessary to break it in, then the squeaking will go away?!

2 - When I touch the main gear, I get a dark black residue on my fingers, like graphite. It is very hard to scrub off. This makes me wonder if something is causing excessive wear on the main gear. Or is this again just part of the break-in?

3 - Occasionally, I hear something that sounds like the belt slapping the inside of the boom. I notice it more when the heli is on the ground at lower RPM's. I had the tension set to where the belt tensioner was flush with the edge of the frame. I tried adding a tiny bit more tension, to where it sticks out past the frame about 1mm or so, but still get the slapping sound.

Anyone have similar experiences or recommendations?

Thanks!
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Old 03-20-2012, 11:18 PM   #2
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1- I have the same sutuation but I think my sound comes from the tail.

2- that's normal, main gear need's to breaking, after few more flights is going to be good, keep using WD-40 or synthetic grease.

3- I don't have a responce for #3
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Old 03-21-2012, 12:28 AM   #3
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Hi there

I cant say for sure what's causing your heli's squeaking,
but in the industrial world, this kind of sqeaking, being heat related,
(i.e. comes and goes with the bearing temp.)
is remaniscent of a bearing fauilure in the works.

Either no grease or some other bearing abnormality might be causing bearing wear, it will ultimately get worse (louder and more frequent) before it locks up. Ive seen this many times in small high speed motor applications.

Hopefully it is nothing, and my diagnosis is all washed up. lol

My Goblem is still on the bench waiting for parts, maybe they are all a little squeaky!

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Old 03-21-2012, 12:28 AM   #4
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Mine never squeaked..

The slapping is not normal. Did you install the tensioner pulley correctly? It should be rotated 270 degrees to be preloaded. If you have it 180, it won't indicate the right tension.
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Old 03-21-2012, 02:09 AM   #5
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Yeah mine squeaks at the end of a flight too. I'm pretty sure it is the brass bushes both sides of the one-way squeaking on the shaft. I filled my one way with triflow oil when building and after flight 5.
Either that or maybe the motor belt noise because it is warm?

Might pop the belts next session and check it out.
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Old 03-21-2012, 03:46 AM   #6
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mine makes that squeak sound also when i land the thing after hard 3D flight.

i think it's the main gear it self! becose there is no gap between it and pinion at all. i think this is designed to have that 19 tooth pinion and they just replaced it with that 20 tooth and no other modifications were made (?) and thats why its so tight. and when it's warming up in flight it expands and starts to squeak.

just my theory. i think it's not a bearing failure or anything bad. if it's the maingear it should wear and go away after few more flights. i now got 6 flights and i use lithium grease.
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Old 03-21-2012, 09:12 AM   #7
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Did you spray the belt with silicon?

I have had the belt squeak against the idler pulley flanges on several belt driven models. Spraying the belt with silicon has always cured it.

Did you lube the bearings-especially the ones in the idler pulleys?

I cannot speak to the issue of the belt slapping the inside of the boom on a Goblin, as I do not have one to examine. On models with conventional tail booms, many people are under the mistaken notion that the belt should be so tight that it does not slap the inside of the boom-which is incorrect (that is way too tight). On most machines equipped with a cog-belt driven tail, the belt should be just tight enough so that it does not skip a tooth when the tail rotor is held with one hand, while attempting to turn the rotor head with the other.

I have one machine with a belt tensioner (a 7HV). To set the belt tension on that model, I blocked the belt tensioner so that it exerted no force on the belt, set the belt tension as above (so that it would not slip under hand pressure, then relaxed the tensioner, so that it exerted force on the belt.

I do not know what the correct procedure for the Goblin is without seeing their instructions. This is how I would approach it, unless the instructions contradict this (I would follow the manufacturers instructions).
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Old 03-21-2012, 09:28 AM   #8
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Quote:
Originally Posted by Ah Clem View Post
Did you spray the belt with silicon?

<snip>

I do not know what the correct procedure for the Goblin is without seeing their instructions. This is how I would approach it, unless the instructions contradict this (I would follow the manufacturers instructions).
Belt tension instructions
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Old 03-21-2012, 11:02 AM   #9
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What's all this WD-40 talk... WD-40 is not a very good lubricant.... itís a Water Displacer.
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Old 03-21-2012, 11:58 AM   #10
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gww528,

Thank you! I will watch the video!

Vicovaludemero,

Agreed, WD40 is not a lubricant at all-it was developed as a Water Displacer. It works as a solvent, also.
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Old 03-21-2012, 12:05 PM   #11
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WD40 is recommended in the manual for the main gear which is why we're discussing it.
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Old 03-21-2012, 12:10 PM   #12
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"WD40 is recommended in the manual for the main gear which is why we're discussing it."

Understood, I think a couple of us are just wondering why, as it is not a lubricant.
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Old 03-21-2012, 12:21 PM   #13
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Quote:
Originally Posted by Ah Clem View Post
"WD40 is recommended in the manual for the main gear which is why we're discussing it."

Understood, I think a couple of us are just wondering why, as it is not a lubricant.
Has anyone simply asked SAB about this? Or maybe Bert can add his input on it?
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Old 03-21-2012, 03:45 PM   #14
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Ya, I noticed that it was recommended in the manual... I thought maybe that was a mistake, or perhaps their WD40 is different from the stuff we have here in the states, and does in fact work as a lube.
I didnít really bother asking since I donít have a Goblin... not yet anyway
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Old 03-21-2012, 06:23 PM   #15
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Quote:
Originally Posted by OnTheSnap View Post
WD40 is recommended in the manual for the main gear which is why we're discussing it.
It would seem that the main gear is designed to start with a very tight mesh and then to "wear in". So the WD40 is likely being used as a cutting lubricant, which being very thin it would do fairly well (a lubricant that is too effective will just slow the wear in process).

AFAIK its not really there as a lube but more to help the pinion grind the main gear down to size. This would also explain the squeaks, since the gear is not worn in yet and is still rubbing on the pinion more than it should.
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Old 03-21-2012, 07:28 PM   #16
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Quote:
Originally Posted by desertstalker View Post
It would seem that the main gear is designed to start with a very tight mesh and then to "wear in". So the WD40 is likely being used as a cutting lubricant, which being very thin it would do fairly well (a lubricant that is too effective will just slow the wear in process).

AFAIK its not really there as a lube but more to help the pinion grind the main gear down to size. This would also explain the squeaks, since the gear is not worn in yet and is still rubbing on the pinion more than it should.
This is very sound logic and is likely the reason they recommend it. After 20 flights mine is fully worn in now so I think I'll apply some Tri-flow synthetic grease.
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Old 03-21-2012, 08:46 PM   #17
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Mine had the same squeak. I have about 20 flights on it now and it is gone.
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Old 03-21-2012, 09:57 PM   #18
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Mine also squeaked the past 2 Sunday's when I was able to get several flights in. Didn't notice it today with only one flight but I used the lithium grease building it also. If I hear it again I'll switch to the wd40 I didn't think of it in that light
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Old 03-22-2012, 07:20 AM   #19
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Ok so it sounds like the squeaking is normal, considering I only have a couple flights on it so far. Plus when I turn the head very slow by hand, I can hear the squeak turn in to a creaking sound just like when you try to slowly open a squeaky door! And that sound is coming right fom where the two gears mesh.

But apparently I'm the only one with a belt slapping issue

I set the tension like in the video, then added a tiny bit more tension, but that didn't seem to help much. It will be running really smooth, then out of the blue ill hear a cracking sound from the boom area. Almost like the drivetrain got caught up or a split second and caused the belt to snap against the boom.

Perhaps this has to do with the breaking in of the gears? Any other ideas?

Will see if it goes away as the gears break in.

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Old 03-22-2012, 08:05 AM   #20
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I do recall a strange sound like u are describing on a few flights. I only noticed it when I'd make a hard turn where the heli faced me nose in right side up. Only happened a few times and one of those flights i did several turns to try to pinpoint it, maybe heard it 3 times outta ten. the entire sound experience this heli produces is foreign to me, this is my first 12s setup and most of my flights to date have been tweaking setting and getting the feel for it whilest listening too. The first time I heard it I thought it had to be the belt because there is enough slack there to touch but it takes a bit of force to get it to. Anyway my boom has been taken off twice since the last time I heard it and nothing since then. Idk what it really was or why, or if it'll come back. I'll post if it does and hopefully you will do the same. One thing I can say is there wasn't any change in the flight characteristics while this sound was being made. Those flights were also at 2000rpm. Now I'm at 2150
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