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Old Dec 11, 2011, 11:36 PM
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xxxcellarator's Avatar
Toronto, Canada
Joined Nov 2009
654 Posts
Hey guys, I need a little help figuring something out.

For some reason, my motor has a very strange and annoying vibration at about 1/2 throttle. It's so bad, it almost wants to brake the motor and mount apart.

It's strange because it only happens at an exact RPM, which is about 1/2 throttle. As soon as I get past that point, the vibration completely disappears and it runs as smooth as a babies bottom. Even all the way at full throttle. I'm running 5s, so the RPMs at full throttle are incredibly high.

I have spent almost an hour balancing the prop to perfection. So I know the prop isn't the issue (which is why it spins so nicely at full throttle).

So why am i getting this horrid vibration at 1/2 throttle?

My guess is that either the motor shaft or the adapter is bent, so at 1/2 throttle it shakes, but past that, the wobble is neutralized by the increased rotational force/mass of the well balanced prop.

What do you guys thing?
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Old Dec 11, 2011, 11:56 PM
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gchrisgo34's Avatar
United States, GA, Jonesboro
Joined Nov 2010
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mine does the same with an apc 6x4 i have. i put the regular 6x4 E on, and it runs perfect. id also like to know what the dealio is, cause i like the vibrating prop better.
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Last edited by gchrisgo34; Dec 11, 2011 at 11:57 PM. Reason: wrhrwthr
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Old Dec 12, 2011, 12:32 AM
Why the dirt on the wings?
moparmyway's Avatar
New York
Joined Jan 2009
4,990 Posts
Have eithor of you 2 Dudes tried to oil your bearings ?
Boca Bearing has Lightning Lube, or try Marvel Mystery Oil ............... both work great !!
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Old Dec 12, 2011, 12:33 AM
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xxxcellarator's Avatar
Toronto, Canada
Joined Nov 2009
654 Posts
I really don't know if it's the prop though. At least in my case, I've spent a lot of time to try and get the prop balanced to perfection. And I've balanced a different sized prop also and it does the exact same thing.

I am using TGS props from Hobbyking. 4.5x4.5, 4.75x4.75 and 5x5. All props create the exact same vibration at 1/2 throttle. And I am using these props on 2 of the same motors and both do the same thing. Only difference is that some props will do it slightly less than others. But they all do it.

It's extremely annoying because even on my other motor where it doesn't do it quite so bad, I have to try and avoid that throttle range, because it sounds and runs horrible.
Almost makes me want to constantly be on full throttle LOL

I'm going to fiddle around some more with it, see if I can determine whats wrong here. My best guess right now is that I need a higher quality prop adapter than the one that came with my Turnigy motor.

But if anyone else has experienced this before and has a better idea, it would be appreciated.
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Old Dec 12, 2011, 12:37 AM
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xxxcellarator's Avatar
Toronto, Canada
Joined Nov 2009
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Quote:
Originally Posted by moparmyway View Post
Have eithor of you 2 Dudes tried to oil your bearings ?
Boca Bearing has Lightning Lube, or try Marvel Mystery Oil ............... both work great !!
Nahh, it's not the bearings. The motor runs perfect without a prop on. Plus, why would it only do it at 1/2 throttle in that case. It would get worse as the RPMs increase.

And for what it's worth, i soak my bearings in oil when i first get the motor. And the motor has not been flown yet. So still plenty of oil.
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Old Dec 12, 2011, 12:45 AM
Why the dirt on the wings?
moparmyway's Avatar
New York
Joined Jan 2009
4,990 Posts
What about ESC switching rate and ESC timing changes ?
Do they have any effect on what you are seeing ?
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Old Dec 12, 2011, 03:13 AM
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Toronto, Canada
Joined Nov 2009
654 Posts
Quote:
Originally Posted by moparmyway View Post
What about ESC switching rate and ESC timing changes ?
Do they have any effect on what you are seeing ?
Well... I'm using a Hobbyking ESC, and I thought about that, so I tried different timings. These ESCs have 4 timings. 1, 7, 15 and 30 degrees. I've tried all 4 and all do the same thing. I haven't tried changing the PWM setting. It's currently set to 16Hz. It says the 8Hz mode is only for low RPM low pole count motors, so thats why I didn't even bother. But I will try that just to make sure.

But I'm convinced it's not a timing issue either, because the motor runs fine with no prop on. But who knows, maybe it's the load of the prop that affects it. Will see.
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Old Dec 12, 2011, 04:08 AM
"The Judge"
sebbe's Avatar
Sweden
Joined Feb 2006
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These vibration issues can be there suddenly, its some sort of vibration you are getting even if the prop is super balanced, can be the motor itself, can be propadapter, if you have spinner it mostly likely that one..

There is a solution but its not an easy one, takes time, but often works all the time..

I think you have some unbalanced motor or adapter in some way, maybee the adapter is not 100% aligned to the shaft..

Try this:

Losen the prop and Move the propp like clockwise in sections like 45 degrees, and see if it gets better ?? if it does, then there is hope..
If you still have problems, change the prop, no matter if the prop is balanced, there can bee issues anyway, try at least 2 different props.. and also turn the prop in sections 45 degrees, and see if there is a spot that is good..

As I said I have a way that will solve it for you, but try this first, then I can tell what to do next..

I also hate the vibrations, its the worst thing when you build a plane...
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Old Dec 12, 2011, 02:31 PM
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xxxcellarator's Avatar
Toronto, Canada
Joined Nov 2009
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Quote:
Originally Posted by sebbe View Post
These vibration issues can be there suddenly, its some sort of vibration you are getting even if the prop is super balanced, can be the motor itself, can be propadapter, if you have spinner it mostly likely that one..

There is a solution but its not an easy one, takes time, but often works all the time..

I think you have some unbalanced motor or adapter in some way, maybee the adapter is not 100% aligned to the shaft..

Try this:

Losen the prop and Move the propp like clockwise in sections like 45 degrees, and see if it gets better ?? if it does, then there is hope..
If you still have problems, change the prop, no matter if the prop is balanced, there can bee issues anyway, try at least 2 different props.. and also turn the prop in sections 45 degrees, and see if there is a spot that is good..

As I said I have a way that will solve it for you, but try this first, then I can tell what to do next..

I also hate the vibrations, its the worst thing when you build a plane...
Ok, here's an update. After some fiddling around for 2 hours, i have made a few discoveries and managed to pin point the source of the vibration.

First thing I did was to take the motor apart and look at the shaft and bearings. I know the bearing on the stator side (the on that gets the stress from the prop pushing into it) comes in an out very easily on this motor. I can just tap on the motor and it'll pop out. So i put some loctite around that bearing just to make sure. I really don't know if this can have much of an affect on the way the motor runs, unless its really bad. Thought I'de mention it nevertheless. Although, I can still feel i tiny bit of play from side to side. But I think thats because the bearing inside is not very tight. It's a cheap Turnigy 2836, so i wouldn't be surprised.

2nd thing I noticed was that the shaft or bell aren't spinning perfectly true. I placed the bell into only one of the bearings (away from the stators) and spun it by hand to see how it feels. It wasn't perfectly true, however, barely noticeable. Don't know if it's the shaft being slightly bent or the hole in the bell.

3rd thing I did, I spun the motor freely without anything on it (no adapter, no prop). Despite the things i mentioned above, the motor runs silky smooth. So smooth you almost can't even feel it spinning in your hand.

4th thing I did, I put the adapter and prop back on, and spun it slowly by hand and also very slowly from the TX. Doing this, I could see the adapter CLEARLY wobbling. Just to see what happens, I tried using a cone style nut, instead of a regular nut to tighten down the prop. The wobble was even more obvious when looking at the cone, and when I spun the motor, I had to stop at about 1/3 throttle because it was getting ridiculously bad even at that point.

Now that it became more obvious what the issue was. I tried the 5th thing. I had another of the same adapter from a spare 2836 motor I had. As soon as I put that on, spinning it slowly, I could see that it was turning almost perfectly straight. The really bad wobble from the other adapter was almost completely gone. And sure enough, when I spun the motor up, the vibration at mid-throttle was almost completely gone as well. Although there is still some. By rotating the prop clockwise (as you suggested SEBBE) I can get it to spin almost perfectly, but still not quite.

I'm happy with the way it runs now. The vibration at mid-throttle is negligible. However, it's clear that the quality of those adapters leaves a lot to be desired. I have 3 of the 2836 motors, so I have 3 of those adapters that came with the motors. And all 3 do it to some extent. The one I had before, was simply so bad, that it was completely unusable. I'm surprised it didn't snap the shaft while I was testing it. The one I have on now is by far the best.

I also noticed that the distance these adapters can slide onto the shaft varies. Some almost cover the entire shaft while others leave an additional 2-4mm gap. As well, I noticed while spinning the nut from the bad adapter, that it seems to wobble as it screws down. Wonder if it's the nut that causes the adapter to tighten down at an angle (since it's a collet style adapter). Will have to try a different nut in the future with this adapter.

To sum it all up, be careful with these cheap parts from Hobbyking. You never know what might be improperly manufactured and causing issues. I know this from past experience too. I once had a cone style nut from a Turnigy 35-42 motor that was so horribly drilled, that tightening it on the shaft just looked funny. It must've been off by about 10-15 degrees. I didn't even try running.

On my next HK order, I'm going to order a couple separate adapters and hopefully I can find some better ones. Anyone bought any of their 4mm adapters that have worked well?

Thanks for your help guys.
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Old Dec 12, 2011, 02:35 PM
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United States, NJ, Roseland
Joined Apr 2009
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where does one oil the bearings on an HET motor??
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Old Dec 12, 2011, 02:52 PM
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United States, GA, Jonesboro
Joined Nov 2010
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thats some great insight xcellerator, thanks for sharing all of your tests. i thinks the problem with mine is a couple of different varients. mine is a CHEAP $20.00 toysonics motor. if i grab the shaft and push and pull on it, it will move back and forth a mm or 2. and my prop adapter has been scuffed and ground. i believe its either the prop adapter off balance or the motor shaft is vibrating back and forth. not side to side, like its off balance, but back and forth. or its a combo of both. ive got a new prop adapter im going to try. ill also oil the bearings. ill report back to let you know how it goes.
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Old Dec 12, 2011, 04:34 PM
"The Judge"
sebbe's Avatar
Sweden
Joined Feb 2006
5,788 Posts
If you buy a "real" quality adapter, and balance your prop good, them you know if it still vibrates that its most likely a bad motor/shaft...

I always try to use quality prop adapters like MpJet or Hyperion when it comes to fast spinning motors,,, running a 950kv motor with a 10x4.7 apc slowfly propp and 3s lipo isnt that critical and you might get away with a bad adapter, but not with high rpm motors..

Im glad you almost solved your problems.... Buy a good adapter from Aircraftworld, and maybee all your problems will be fine..
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Old Dec 12, 2011, 06:11 PM
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xxxcellarator's Avatar
Toronto, Canada
Joined Nov 2009
654 Posts
Quote:
Originally Posted by gchrisgo34 View Post
thats some great insight xcellerator, thanks for sharing all of your tests. i thinks the problem with mine is a couple of different varients. mine is a CHEAP $20.00 toysonics motor. if i grab the shaft and push and pull on it, it will move back and forth a mm or 2. and my prop adapter has been scuffed and ground. i believe its either the prop adapter off balance or the motor shaft is vibrating back and forth. not side to side, like its off balance, but back and forth. or its a combo of both. ive got a new prop adapter im going to try. ill also oil the bearings. ill report back to let you know how it goes.
the back and forth movement is an easy fix. Just shim the shaft where the retaining clip is. Or if your motor uses a collet, tighten the collet tighter to the motor. However, my guess is that a back and forth movement is not going to cause vibrations, it's the side to side movement that does (like when the bearings are loose).

Quote:
Originally Posted by sebbe View Post
If you buy a "real" quality adapter, and balance your prop good, them you know if it still vibrates that its most likely a bad motor/shaft...

I always try to use quality prop adapters like MpJet or Hyperion when it comes to fast spinning motors,,, running a 950kv motor with a 10x4.7 apc slowfly propp and 3s lipo isnt that critical and you might get away with a bad adapter, but not with high rpm motors..

Im glad you almost solved your problems.... Buy a good adapter from Aircraftworld, and maybee all your problems will be fine..
Yeah, I'm definitely going to look for some higher quality adapters. Thanks for all the info.
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Old Dec 12, 2011, 07:14 PM
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Toronto, Canada
Joined Nov 2009
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hey sebbe, what was the method that you had thats not easy but works almost every time to get things balanaced?
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Old Dec 12, 2011, 07:50 PM
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United States, MI, Port Huron
Joined Jun 2006
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If your not sure if your shaft is bent....take the prop and prop adapter off, take the blunt side of a butter knife and rest it on the shaft and spin the motor up at 1/8th throttle at most. If its straight it will feel smooth, providing it does not have a flat side on the shaft. If it has any kind of bend you will feel a vibration in the knife, if its bad enough you will actually hear the knife bouncing on the shaft.
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