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Prop seal replacement and subsequent vibration
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Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Wed Sep 06, 2006 4:11 am Post subject: Re: Prop seal replacement and subsequent vibration

I'll give that a shot.  What bothers me is why this happened.  I went from zero vibration to losing-my-fillings vibration.  I'm just wondering if i'll find the answer when i overhaul the hub?

 	  dsavarese(at)elmore.rr.co wrote: 	
		  Scooter,

Why don't you try the simple test I mentioned yesterday?  Put a wrap of duct 

tape on one of the blades about 2" in from the tip and run the engine.  If 

it improves, you've got the right blade.  If it gets worse, remove the tape 

on that blade and put a wrap on the other blade and run it.  Regardless of 

which blade it is, add a wrap at a time until the vibration becomes 

acceptable.  You can add spray paint to the back side of the blade once you 

find out which blade needs additional weight.  Somewhat crude, but it works 

and it's a very simple test.

Dennis



---

ggg6(at)att.net
Guest

Posted: Wed Sep 06, 2006 4:15 am Post subject: Prop seal replacement and subsequent vibration

With the intake drain open or a broken drain tube the Engine will idle at about 36%..  Gary

 [quote]-------------- Original message from "Roger Kemp" <viperdoc(at)mindspring.com>: -------------- 

[quote] --> Yak-List message posted by: "Roger Kemp" 

 

 Mark, 

 I have left my intake drain open a couple of times. I did notice it 

 misssing but not a violent vibration. If that is what Scooter was trying to 

 relate. 

 Doc 

 

 

 > [Original Message] 

 > From: Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E 

 

 > To: 

 > Date: 9/5/2006 3:31:20 PM 

 > Subject: RE: Re: Prop seal replacement and subsequent vibration 

 > 

 > --> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, 

 MALS-14 64E" 

 > [b]>  > 

 > Not to disagree with anyone's suggestions (all good), but the first 

 > thing I would do would be to either purchase or borrow an Infra Red 

 > Temperature gun.... Run the engine for awhile and then go shoot each 

 > cylinder and check for close to the same readings on each one. It might 

 > be something so simple as a dead cylinder. Compression checks to 

 > follow. 

 > 

 > Or ... Do the following first: 

 > 

 > 

 > Take a REALLY close look at your intake drain system. A lot of these 

 > systems were installed with #4 AN fittings and soft aluminum lines. 

 > Over time theses things are prone to crack and break, leaving you with a 

 > rather large leak in the intake system, which makes the engine run rough 

 > just as you have described. The best solution here of course is to use 

 > flexible steel braided li  nes. I  ======      [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Wed Sep 06, 2006 1:52 pm Post subject: Prop seal replacement and subsequent vibration

Gary,  the actual change in idle RPM will vary from engine to engine, and also with the  location of the leak and how big it is, not to mention who's version of intake  drain kit you have.  My engine idles at 20% normally... with the throttle  full back.  With the intake drain valve open, the idle is almost exactly  the same.  With my engine, the indicators are: more backfiring in flight  with the throttle at idle, and a possible backfire on take-off if  the throttle is pushed forward too fast.  All of this changes if you  simply adjust the carb one or two clicks.  For example, when it happened to  a PF model M-14, and it was just a cracked tube, the engine was missing in  flight at full power and under full load (in the vertical).  Everywhere  else it was just fine.  

  

 It is  an insidious problem, and no two airplanes are likely to be identical with their  particular symptoms.  

  

 V/R, 

  

 Mark  Bitterlich 

  

 p.s.  And Doc, I agree that the intake drain leak  is not likely to give you a violent vibration.  However, it does change the  way the engine "feels" (per se) as you increase RPM.  As I have read about  this problem, it seems I did not quite understand just how severe the vibration  was.  At first I thought it was barely perceptible, but definitely  THERE.  Now I am hearing:  VIOLENT VIBRATION. So... sorry, I  misunderstood.    I agree with a lot of other peoples  recommendations... especially the one where someone suggested that the oil tube  might have gotten bent.  THAT is very likely considering that when the  seals were replaced, the tube would have had to have force applied to it to put  everything back in place again.  POOF... problem starts on next engine  start.  After all this, my bet is that it HAS to be in the hub.  But  hey... nothing wrong with checking that all cylinders are the same temp, and  that there are no induction leaks, and a compression check.  If those all  checked good, along with obvious mag checks, then that pretty much leaves  nothing else BUT the hub/prop.  

   From: owner-yak-list-server(at)matronics.com  [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of  ggg6(at)att.net

Sent: Wednesday, September 06, 2006  3:06

To: yak-list(at)matronics.com

Subject: RE: Re:  Prop seal replacement and subsequent vibration

 

 

With the intake drain open or a broken drain tube the Engine will  idle at about 36%..  Gary

 [quote]--------------    Original message from "Roger Kemp" <viperdoc(at)mindspring.com>:    -------------- 

 	  Quote: 	
		   --> Yak-List message posted by: "Roger    Kemp" 

 

 Mark, 

 I have left my    intake drain open a couple of times. I did notice it 

 misssing but not    a violent vibration. If that is what Scooter was trying to 

 relate.    

 Doc 

 

 

 > [Original Message] 

 >    From: Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E 

    

 > To: 

    > Date: 9/5/2006 3:31:20 PM 

 > Subject: RE: Re: Prop    seal replacement and subsequent vibration 

 > 

 > -->    Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, 

    MALS-14 64E" 

 > > > 

    > Not to disagree with anyone's suggestions (all good), but the first    

 > thing I would do would be to either purchase or borrow an Infra    Red 

 > Temperature gun.... Run the engine for awhile and then go    shoot each 

 > cylinder and check for close to the same readings on    each one. It might 

 > be something so simple as a dead cylinder.    Compression checks to 

 > follow. 

 > 

 > Or ...    Do the following first: 

 > 

 > 

 > Take a    REALLY close look at your intake drain system. A lot of these 

 >    systems were installed with #4 AN fittings and soft aluminum lines. 

    > Over time theses things are prone to crack and break, leaving you with a    

 > rather large leak in the intake system, which makes the engine    run rough 

 > just as you have described. The best solution here of    course is to use 

 > flexible steel braided li nes. I ======  	  Quote: 	
		  [b]


	


.com/Navigator?Yak-List



	
[/b][b]

windsorsedge(at)ozemail.c
Guest

Posted: Wed Sep 06, 2006 3:55 pm Post subject: Prop seal replacement and subsequent vibration

Guys

I have a standard Russian VHF in my 52

That receives but has stopped transmitting.Sounds like carrier wave only,

have tried reracking but still no good

Tim in Oz 

--

dsavarese(at)elmore.rr.co
Guest

Posted: Wed Sep 06, 2006 4:25 pm Post subject: Prop seal replacement and subsequent vibration

You can ship your radio back to Termikas in Lithuania and they will repair 

and test it.  That is the only company I know of that can do it that we are 

able to communicate with.  http://www.termikas.com/  No idea how much it 

will cost.  But at least you can ask.

Dennis



---

mark.bitterlich(at)navy.m
Guest

Posted: Wed Sep 06, 2006 4:31 pm Post subject: Prop seal replacement and subsequent vibration

Here are a couple of questions: 



1.  When you transmit do you have sidetone?  Excuse me, that is a

military term...   When you transmit, can you hear your own voice in the

headphones as you transmit?  Is your "sidetone" normal or very weak?  



2.  I am assuming that you listened in on another radio in another

airplane and you heard a carrier with no microphone audio?  Yes, no?  



3.  Try more than one frequency.   Make sure you try another frequency

where each knob on the frequency selector has moved.  On the receiving

radio, try moving one click to each side of the frequency that is being

transmitted on and see if you hear any audio at all.  



4.  Lastly... There is an adjustment on the front of the Balken 5 R/T

that adjusts transmit modulation level.  You might try cranking that up

a tad and seeing what happens.  Actually, there are TWO adjustments on

the front of the radio.  One is for the modulation level, and umm...

Darn, I forget what the other one is for! I'll have to check on the

schematics and get back to you.  



If all else fails, I have a working Balken 20 for sale.  You really need

to look for the Balken 5, which is more than likely what you have.  The

Balken 20 is a high power version of the one typically found in the 52,

and it has four times the power. Meaning, it ain't cheap.    



Try George Coy and see if he is selling any radios too... He usually has

Balken 5's for around $450 or so.  



Best of luck, 



Mark Bitterlich

--

Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Wed Sep 06, 2006 6:56 pm Post subject: Re: Prop seal replacement and subsequent vibration

This is sort of interesting.  I calculated the resonant frequency of a Yak-52 (assuming it is much like a big violin string) and came up with the following:



The resonant frequency of a yak:



fn = nv/2L

  n = harmonic (1,2,3...)

  v = speed of sound (in steel) = 16,000 ft/sec

  L = length = 25.42 ft



f1 = 314 hz

f2 = 628 hz (32% rpm)

f3 = 942 hz (49% rpm)

f4 = 1256 hz (65% rpm)

f5 = 1570 hz (80% rpm)



Note:  at 50% rpm the engine rpm is 1475.

Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Thu Sep 07, 2006 5:43 am Post subject: Re: Prop seal replacement and subsequent vibration

Thanks.  I am going to pull the blades and regrease/inspect but leave the hub rebuild for a last option.  I've checked the tube pretty thoroughly and it doesn't appear to be bent or leaking.  Does a bent tube cause an imbalance or does it somehow disrupt oil flow to the dome?



I'm still at a loss to explain why the vibration would suddenly occur after replacing the two seals in the dome.  Ideally I'd like to know what caused it before trying to fix it by rebalancing the blade.  As for flying the aircraft from the back seat - i can't imagine anyone would fly this aircraft with this amount of vibration.



 	  flir47 wrote: 	
		  Scooter,



Did you try Dennis’s suggestion of the tape first?? Also make the check for the bent tube. You took some time here to make some rather interesting calculations. Why not do some more checks before just tearing the hub down??? A hub should not need an overhaul after a simple seal change. If you need some pic’s of what to look for let me know. My prop did the same exact thing and was a bent tube. Also if you think I’m FOS.... fly it from the back seat and feel the growling drone of the resonance. It will be less from the front.

wlannon(at)cablerocket.co
Guest

Posted: Thu Sep 07, 2006 6:53 am Post subject: Prop seal replacement and subsequent vibration

Someone has probably suggested this already but just in case!!!!!! Have you 

checked the blade angles to see if one blade has moved in the clamp?

There is no way that replacing the pitch change seals could result in the 

vibration you describe. The problem is somewhere else. If the blade angles 

are OK the next thing I would suggest is a measurement of piston 

displacement to check for a bent rod. Good luck



Walt



---

dsavarese(at)elmore.rr.co
Guest

Posted: Thu Sep 07, 2006 9:16 am Post subject: Prop seal replacement and subsequent vibration

Please be aware that Aeroshell has changed their formula for #22.  It used 

to be thick and pasty.  The last batch of #22 that I bought was almost to 

the point of being runny.   Even body heat would make it runny.   It was 

horrible and Aeroshell swore they didn't change their formula.  I returned 

it and bought #5 instead.

Dennis



---

mark.bitterlich(at)navy.m
Guest

Posted: Thu Sep 07, 2006 1:49 pm Post subject: Prop seal replacement and subsequent vibration

Walter, I agree with all your suggestions and thoughts, but I wanted to offer one comment via "bent rods".  We just had a YAK-52 here locally that had a hyd. lock that resulted in a bent rod. The aircraft was started, had no vibration what-so-ever and proceeded to take off and fly.  Within 10 minutes of flight, the rod broke, started slamming around all over the case, and pretty much trashed the engine.  The aircraft flew back to New Bern ... Obviously vibrating very badly at this point, and landed safely.  This might start a debate, but I submit that a bent rod will not cause this kind of vibration.  If a rod is bent just a tad and is still connected to the piston, that cylinder is just going to have a stroke that is slightly less than the other 8.  It will develop slightly less compression....not a LOT less, but SLIGHTLY, and it will still fire and produce energy.  At 45% power, and very little load on the engine, I doubt that even a talented mech could "feel" it.  The fact is that the pilot it happened to here never felt ANYTHING unusual ... Until it failed of course.  Of note is the fact that the bent rod in this engine did not actually bend... It twisted.  Not unusual when you consider that this rod is an I-beam and the forces involves.  



The reason I bring this up is because I have always heard people talking about bent rods and vibration on M-14's and it never made sense to me, however I never had experience with it.  I can now say from experience that a bent/twisted rod, damaged so badly that it failed 10 minutes into flight, caused no vibration on the deck or during take-off that was noticed by the pilot. 



Maybe this will start a discussion... If so good, I'd like to hear other peoples thoughts on the subject. 



Mark Bitterlich

N50YK

 



--

wlannon(at)cablerocket.co
Guest

Posted: Thu Sep 07, 2006 4:34 pm Post subject: Prop seal replacement and subsequent vibration

Hi Mark;



Never having experienced a damaged link rod from a hydraulic lock I have no 

idea what level of vibration would ensue. I would expect that to be a 

function of the bending severity.

The only two hyd. lock damaged link rods I have seen were both severely 

bent, one almost 90 deg. Whether they were also twisted I don't know, none 

was immediately evident.



The force involved would be primarily compression which one would expect to 

result in bending since the rod/piston combination has been forced to occupy 

a smaller than usual space.



There is a possible method to inspect for compression damage by measuring 

the actual piston stroke in each cylinder and comparing that to the 

specification standard. The nominal stroke is 130 mm (Huosai, AI14 & M14 

engines). Only the master rod cylinder is 130 mm. All link rod pistons have 

a slightly longer stroke due to location of the link rod pivot in relation 

to the center of the crank journal (all radials). These dimensions are given 

in the manuals. A precise measurement would require the manufacture of some 

serious tooling but a check for gross damage could be done using the TDC 

indicator or a Time-Rite.



Walt



---

Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Mon Sep 11, 2006 3:56 am Post subject: Re: Prop seal replacement and subsequent vibration

UPDATE:  I took Dennis's advice and wrapped some tape around one blade.  The vibration seemed to get a little worse so I wrapped some tape around the other blade.  Seemed to get better.  So I wrapped a little more and it was definately greatly improved.



The weight of the tape is 0.9 oz and was 43" from the center of the hub.  This seems to equate to about 7.8 oz at the point where you attach the balancing weights (assuming that's 5" from center).  Seems like quite a bit of weight.



Next step, I guess, is to pull the prop and check static balance.  I'm still at a loss to explain how this could have happened.  I pulled one of the blades (the blade that I put the tape on) and saw nothing out of the ordinairy.

dsavarese(at)elmore.rr.co
Guest

Posted: Mon Sep 11, 2006 4:13 am Post subject: Prop seal replacement and subsequent vibration

Scooter,

You're not going to be able to put 7.8 ounces of weight on the hub.  My 

suggestion is to do as you suggested and statically balance the prop.  Try 

balancing it with the counterweights slightly pulled back from full fine 

pitch and check the balance at the 45, 90, 120, 180, 225, 270, 315 and 360 

degree points.  You can also use a can of spray paint and spray the back 

side of the blade to "fine tune" the static balance.

Dennis



---

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