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Gtblu

Joined: 18 Jul 2006
Posts: 37
Location: Australia

Posted: Sun Dec 30, 2007 4:52 pm Post subject: Engine Vibration

Hello Listers and Happy New Year.



Many users of Rotax 912 uls Engines talk of vibration between abut 4400 and 5000 revs which you get used to after a while. However the top end of that vibration is now creeping up to 5300 revs. Its incredible consistant even to the point of the vibration stopping if extra load is put on  like a turn or up elevator. It feels to me similar to bearing float of the crankshaft in a vehicle, but is more obvious in the air especially those magical early mornings with no turbulance.



This engine has been recently split and a new sprag clutch put in (100 hours ago) but bearings were checked and not replaced. The engne has done 729 hours in a Slepcev Storch and runs very sweetly above this moving revs line, currently about 5300 rpm.

It has always run with a little noticable vibration on bothe left and right when doing a mag check. ( Left and right is not entirely accurate as the plugs that operate on each switch are shared top and bottom left and right.



I will check plugs, carby sync, carby's generally, air filters, prop alignment but before I started I thought I'd put this out there for others experience on engine vibration. Its not violent, but its very noticable on a still day especially increasing revs from rough to smooth and as it is changing in nature I need to asses it a little more meticulously. 

 

Any thoughts?



all the best for 2008

regards

Geoff Bell

thilo.kind(at)gmx.net
Guest

Posted: Sun Dec 30, 2007 6:02 pm Post subject: Engine Vibration

Hi Geoff,



sounds to me like a prop issue - you should check angle on the blades. Been there myself...



Good luck



Thilo

-------- Original-Nachricht --------

 	  Quote: 	
		   Datum: Sun, 30 Dec 2007 16:52:05 -0800

 Von: "Gtblu" <gtbjbell(at)gmail.com>

 An: rotaxengines-list(at)matronics.com

 Betreff: Engine Vibration


	


 	  Quote: 	
		   

 

 Hello Listers and Happy New Year.

 

 Many users of Rotax 912 uls Engines talk of vibration between abut 4400

 and 5000 revs which you get used to after a while. However the top end of

 that vibration is now creeping up to 5300 revs. Its incredible consistant even

 to the point of the vibration stopping if extra load is put on  like a

 turn or up elevator. It feels to me similar to bearing float of the crankshaft

 in a vehicle, but is more obvious in the air especially those magical

 early mornings with no turbulance.

 

 This engine has been recently split and a new sprag clutch put in (100

 hours ago) but bearings were checked and not replaced. The engne has done 729

 hours in a Slepcev Storch and runs very sweetly above this moving revs

 line, currently about 5300 rpm.

 It has always run with a little noticable vibration on bothe left and

 right when doing a mag check. ( Left and right is not entirely accurate as the

 plugs that operate on each switch are shared top and bottom left and right.

 

 I will check plugs, carby sync, carby's generally, air filters, prop

 alignment but before I started I thought I'd put this out there for others

 experience on engine vibration. Its not violent, but its very noticable on a

 still day especially increasing revs from rough to smooth and as it is

 changing in nature I need to asses it a little more meticulously. 

  

 Any thoughts?

 

 all the best for 2008

 regards

 Geoff Bell

 

 --------

 Slepcev Storch

 912 uls 731 hours

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=155064#155064

 

 

 

 

 

 

 

 

 


	


-- 

Psssst! Schon vom neuen GMX MultiMessenger gehört?

Der kann`s mit allen: http://www.gmx.net/de/go/multimessenger?did=10

thilo.kind(at)gmx.net
Guest

Posted: Sun Dec 30, 2007 6:03 pm Post subject: Engine Vibration

Hi Geoff,



sounds to me like a prop issue - you should check angle on the blades. Been there myself...



Good luck



Thilo

-------- Original-Nachricht --------

 	  Quote: 	
		   Datum: Sun, 30 Dec 2007 16:52:05 -0800

 Von: "Gtblu" <gtbjbell(at)gmail.com>

 An: rotaxengines-list(at)matronics.com

 Betreff: Engine Vibration


	


 	  Quote: 	
		   

 

 Hello Listers and Happy New Year.

 

 Many users of Rotax 912 uls Engines talk of vibration between abut 4400

 and 5000 revs which you get used to after a while. However the top end of

 that vibration is now creeping up to 5300 revs. Its incredible consistant even

 to the point of the vibration stopping if extra load is put on  like a

 turn or up elevator. It feels to me similar to bearing float of the crankshaft

 in a vehicle, but is more obvious in the air especially those magical

 early mornings with no turbulance.

 

 This engine has been recently split and a new sprag clutch put in (100

 hours ago) but bearings were checked and not replaced. The engne has done 729

 hours in a Slepcev Storch and runs very sweetly above this moving revs

 line, currently about 5300 rpm.

 It has always run with a little noticable vibration on bothe left and

 right when doing a mag check. ( Left and right is not entirely accurate as the

 plugs that operate on each switch are shared top and bottom left and right.

 

 I will check plugs, carby sync, carby's generally, air filters, prop

 alignment but before I started I thought I'd put this out there for others

 experience on engine vibration. Its not violent, but its very noticable on a

 still day especially increasing revs from rough to smooth and as it is

 changing in nature I need to asses it a little more meticulously. 

  

 Any thoughts?

 

 all the best for 2008

 regards

 Geoff Bell

 

 --------

 Slepcev Storch

 912 uls 731 hours

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=155064#155064

 

 

 

 

 

 

 

 

 


	


-- 

Psssst! Schon vom neuen GMX MultiMessenger gehört?

Der kann`s mit allen: http://www.gmx.net/de/go/multimessenger?did=10

Gtblu

Joined: 18 Jul 2006
Posts: 37
Location: Australia

Posted: Sun Dec 30, 2007 6:53 pm Post subject: Re: Engine Vibration

Thanks Thilo, Yes for it to change so quickly  (within two weeks) suggests dirty prop maybe, lots of insects at the moment due to wet warm weather. 



Thanks.

regards

Gt

Johann G. Johannsson

Joined: 10 Jan 2006
Posts: 18
Location: Iceland

Posted: Sun Dec 30, 2007 7:56 pm Post subject: Engine Vibration

Hello Geoff.



Happy New Year to you. 

Do you have an IVO Prop on your Slepcev Storch?

I had this problem on my Kolb ultralight, which was caused be a faulty

prop. There was no way to adjust the propeller, it was balanced and tracked

perfectly, but nothing worked. Finally sent the prop to Ivo for

replacement. Problem solved.



Just a thought.



Best regards,

Johann G.

Iceland.

Zenith 701.



On Sun, 30 Dec 2007 16:52:05 -0800, "Gtblu" <gtbjbell(at)gmail.com> wrote:

 	  Quote: 	
		   

 

 Hello Listers and Happy New Year.

 

 Many users of Rotax 912 uls Engines talk of vibration between abut 4400

 and 5000 revs which you get used to after a while. However the top end of

 that vibration is now creeping up to 5300 revs. Its incredible consistant

 even to the point of the vibration stopping if extra load is put on  like

 a turn or up elevator. It feels to me similar to bearing float of the

 crankshaft in a vehicle, but is more obvious in the air especially those

 magical early mornings with no turbulance.

 

 This engine has been recently split and a new sprag clutch put in (100

 hours ago) but bearings were checked and not replaced. The engne has done

 729 hours in a Slepcev Storch and runs very sweetly above this moving

revs
	


 	  Quote: 	
		   line, currently about 5300 rpm.

 It has always run with a little noticable vibration on bothe left and

 right when doing a mag check. ( Left and right is not entirely accurate

as
	


 	  Quote: 	
		   the plugs that operate on each switch are shared top and bottom left and

 right.

 

 I will check plugs, carby sync, carby's generally, air filters, prop

 alignment but before I started I thought I'd put this out there for

others
	


 	  Quote: 	
		   experience on engine vibration. Its not violent, but its very noticable

on
	


 	  Quote: 	
		   a still day especially increasing revs from rough to smooth and as it is

 changing in nature I need to asses it a little more meticulously.

 

 Any thoughts?

 

 all the best for 2008

 regards

 Geoff Bell

 

 --------

 Slepcev Storch

 912 uls 731 hours

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=155064#155064

_________________
Johann G.
Iceland.
Flying Zenith 701.

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Mon Dec 31, 2007 8:56 am Post subject: Re: Engine Vibration

Hi Guys,



If you have never balanced your prop it should be done. It should be statically balanced first. This means off the plane with the hub and all. Then you should make sure it is tracking properly. This means each blade is turning in the same plane while rotating. Last, but the most important every prop on a plane should be dynamically balanced. This means using an instrument to check the vibration against its weight and balance while it is running at its cruise rpm. You should also check the blades to make sure they are the exact same pitch with a prop protractor.

When I got my Flight Design CT I put a Warp drive on it. When it was dynamically balanced it was .33" out. That's a lot. Weight was added to one side and now it's only .01 out. Huge difference. The .33" out of balance was not felt in the stick. If you can feel a prop out of balance through the stick then it is way out. This is hard on many different parts of your engine and even the mounts. If you have never statically and dynamically balanced your prop that would be a priority if it were me. The longer a system runs out of balance to bigger the toll later.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Mon Dec 31, 2007 4:42 pm Post subject: Engine Vibration

Roger:



Tracking and setting the pitch on my three blade prop assembly is not a real

problem. I do this on my plane with the plane level and in the hanger.

However, do you have any good ideas on how to set up a three blade WoodComp

prop, Klassic 160/3/R (hub and bolts) for static balance? Seems to me one

would need a mating flange to bolt the prop/hub assembly to. This assembly

would then need to be concentrically bolted to a shaft that is in a bearing

assembly that allows free rotation of the entire setup. Then, how does one

statically balance a three blade prop?



The other question is, how on earth does one dynamically balance such a prop

assembly (three blade) while running at cruise speed?? Kind of hard to do in

the air!! The WoodComp manual that came with the three blades states " each

propeller (blades and hub) was factory assembled from blades with the same

weight and center of gravity, then carefully balanced. Make sure you insert

each blade into the appropriate opening in the center hub, blades and

openings are numbered and MUST NOT be mixed under any circumstances!" No

clarifying statement as to whether this is a static or dynamic balance. I

suspect it is a static balance, but I don't really know. If this is not

sufficient, again I ask, how does one ordinary LSA pilot dynamically balance

such an assembly??



Hugh McKay

Allegro 2000

Rotax 912UL

N661WW



--

ami(at)MCFADYEAN.FREESERV
Guest

Posted: Tue Jan 01, 2008 1:57 am Post subject: Engine Vibration

<<again I ask, how does one ordinary LSA pilot dynamically balance

 	  Quote: 	
		   such an assembly??>>


	


Try:



http://www.smartavionics.com/pb/pb.html



Duncan.

---

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Tue Jan 01, 2008 4:49 am Post subject: Re: Engine Vibration

Hugh,



The Woodcomp props are statically balanced at the factory, as you suspected. Unfortunately, over time they get nicks etc. which will affect the static balance a bit. Dynamically balancing a prop/engine requires expensive equipment and competent technician. The prop/engine combination balance check is done while running. Here is a decent FAQ on the subject.



http://www.dssmicro.com/faqs/fqprpbl.htm



As you might expect, DSSMICRO sells this equipment for doing prop balancing. 



I've not found any one in our area that does dynamic prop balancing and the equipment is too expensive unless you are going into the prop balancing business.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Tue Jan 01, 2008 6:32 am Post subject: Engine Vibration

Thom: 



What you have stated is what I suspected. I don't know how many LSAs have

had their props dynamically balanced, but I suspect little to none, and the

reason being the complexity and cost of doing so. I would imagine that good

careful assembly of the WoodComp prop (or any other prop) and hub together,

with careful setting of the pitch on each blade and good care of the blades

(barring something nicking or damaging a blade) would be sufficient for the

Sport Pilot. Unless there is some damage to the blades or a real indication

of a prop vibration problem, I would expect many hours of good flying. I

would imagine though that if one would get damage to one of the WoodComp

blades, you would need to replace all three as well as the hub because they

are factory balanced as a unit.



No, I'm not going into the prop balancing business!



Hugh



--

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Tue Jan 01, 2008 6:48 am Post subject: Re: Engine Vibration

Hugh,



I've corresponded with the Woodcomp folks and they said they can replace a single blade given the serial number of the blade you want to replace because they keep records of exact weight of each blade they manufacture, as balanced. It will be the same as the original in static balance. The serial number is the same for each of the blades on a given prop plus a blade number, which is also required for single blade replacement.



Happy New Year!

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Tue Jan 01, 2008 8:28 am Post subject: Re: Engine Vibration

Hi Hugh,



Your Woodcomp was statically balanced at the factory. Aircraft Spruce and a few other people sell a very simple static balance device that utilizes a bubble balancer on a string. This set up works well enough for those who's props weren't done or wants to check theirs once a year.

Even though your prop is statically balanced, everything forward of the mounting plate on the gearbox i.e. nuts, bolts, washers, spinners and the such are not and none of these are in balance when turning 5000 rpm. All props should be balanced on the plane spinning at cruise rpm. You go out to the pad and chalk the wheels and tie it down. The balancer then can measure vibration that you can not feel. There has to be someone in your area that does this for other aircraft. Just start asking around with the service shops and I'm sure someone knows of a person who can do a dynamic balance. 

Get on the web and type in prop balancing + your town.

The instrument that does this does cost $2K and up, but people who service aircraft should know of someone who has this instrument. Dynamic prop balancing is a regular aircraft maint. function. When I started to look I didn't know of anyone in my area. After a little search I found 4 people who did this. Prices were from $175-$250. Takes about an hour.



Think of a dynamic prop balance that is not done like this. 

If someone smokes cigarettes  or is a diabetic it does not take their life right now, but over a long time period it causes many other problems and an early death. A static balance only for your engine and gearbox is not enough. My Warp Drive was static balanced at the factory, but way off when mounted on the plane with hardware and running.



Gentlemen,

Keeping your engine and plane in good health makes your flying safer, but also extends the life of all your aircrafts components. Don't wait until it breaks to fix it. A little preventive medicine can go a long way in your safety and your pocketbook.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

ami(at)MCFADYEAN.FREESERV
Guest

Posted: Tue Jan 01, 2008 8:50 am Post subject: Engine Vibration

<<It will be the same as the original in static balance>>



In theory. The practice is that the blades that have been in service will 

have settled-in at the roots and, if wood or wood cored, have probably 

changed weight or shape too.



I tried this balance numbers-game replacing one blade on a 3-blade GSC; the 

imbalance present made is unserviceable before rebalancing.



Similarly, I have just reassembled an almost new Arplast 3-blade composite 

which required the equivalent of 2 grammes at one of the tips to make it 

statically balance; this is actually a lot of imbalance and would be very 

apparent on a static balancer at the factory.



Duncan McF.

---

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Tue Jan 01, 2008 9:10 am Post subject: Re: Engine Vibration

Here is a good website link that discusses dynamic prop balancing with photos of the equipment etc.



http://www.dvatp.com/aviation/maintenance/dynamic_balancing

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Tue Jan 01, 2008 9:16 am Post subject: Engine Vibration

Roger/Thom:



Thanks for all of your input on the matter of vibration and balancing of

props. I will inquire as to who may do this type of balancing in my area. 



By the way, I noticed an additional "blob" of fiberglass that was definitely

added and sanded on the inside of my Allegro 2000 fiberglass spinner. I

assumed this was intentionally done to balance the spinner. 



Roger/Thom, if one would weigh each of the attaching (6) bolts, nuts, and

washers, and assuming each item was within an ounce or less of each other,

and these items rotating concentrically on a bolt circle of 75 mm (912UL

gearbox mounting plate) at say 5000rpm, do you think 6 ounces of eccentric

mass at a radius of 37.5mm rotating at this speed could be actually

physically counterbalanced?



Hugh 



--

Mark Burton

Joined: 10 Jan 2006
Posts: 74

Posted: Tue Jan 01, 2008 9:21 am Post subject: Re: Engine Vibration

Howdy folks,



With regard to the expense of dynamic prop balancing equipment. My company, Smart Avionics, used to sell a balancer (the PB-1) that was aimed at the homebuilt aircraft market. It was cheaper and had more functionality than the low range DSS product. Quite a few PB-1 units were sold all around the world and I have had lots of good feedback and success stories from the people who used them. 



I don't make that balancer anymore but I am working on a new balancer that  I expect to be available in the first quarter of 2008. Price is not yet fixed but it will provide good value for money. If you are interested, please take a look at www.smartavionics.com in a couple of months.



Happy New Year,



Mark

trigo(at)mail.telepac.pt
Guest

Posted: Tue Jan 01, 2008 9:36 am Post subject: Engine Vibration

Hi Mark



I am one of the guys waiting for your PB-2, not only for my homebuilt but

also for my microlight



Carlos

[quote] --

hagargs(at)earthlink.net
Guest

Posted: Tue Jan 01, 2008 10:01 am Post subject: Engine Vibration

I have had my prop (airmaster on a 914) dynamically ballanced after I had

balanced my carbs out with my mercury manometers (the only way to go, nuts

to the  white suited hazmat people) no moving parts and no calibration

concerns..  After that the engine ran like a turbine from 1800 rpm up.

There seems to be a lot of frettng about doing this.  The process is is

very easy and straight forward.  When I had my prop done I was taken aback.

The apparatus used was the same type used by the technicians in the plant I

work in to balance large motors.  Just substute "rotating machinery" for 

"propeller" and there are  innumerable people who  know how to do this. 

Bolt an accelerometer and a photo eye to the  engine. Put a reflective dot

on the back of one of the  prop  blades and run the  engine up to the

specified RPM.  The machine does the rest telling you where to put the

weights and how much.  Now if your spinner back plate is already

pre-drilled at 30 degree intervals and you have a 9 series engine (bolt

holes on the  gear box are in just the  right place for the photoeye and 

accelerometer) the job is a piece of cake.  The biggest hassle and most

time consuming chore is taking the spinner on and off to add another

washer/weight to the  spinnner backplate otherwise the job would have taken

about 15 minutes after the prep work is done. A gross, medium, and fine

balance is done adding  smaller amounts of  mass  at different locations

until the desired response is obtained.   The people at Phoenix Composits

did mine and I don't believe it was much away from $100.



Steve Hagar

Mesa AZ



 	  Quote: 	
		   [Original Message]

 From: Roger Lee <ssadiver1(at)yahoo.com

 To: <rotaxengines-list(at)matronics.com>

 Date: 1/1/2008 9:30:11 AM

 Subject: Re: Engine Vibration



 



 Hi Hugh,



 Your Woodcomp was statically balanced at the factory. Aircraft Spruce and

a few other people sell a very simple static balance device that utilizes a
	


bubble balancer on a string. This set up works well enough for those who's

props weren't done or wants to check theirs once a year.

 	  Quote: 	
		   Even though your prop is statically balanced, everything forward of the

mounting plate on the gearbox i.e. nuts, bolts, washers, spinners and the
	


such are not and none of these are in balance when turning 5000 rpm. All

props should be balanced on the plane spinning at cruise rpm. You go out to

the pad and chalk the wheels and tie it down. The balancer then can measure

vibration that you can not feel. There has to be someone in your area that

does this for other aircraft. Just start asking around with the service

shops and I'm sure someone knows of a person who can do a dynamic balance. 

 	  Quote: 	
		   Get on the web and type in prop balancing + your town.

 The instrument that does this does cost $2K and up, but people who

service aircraft should know of someone who has this instrument. Dynamic
	


prop balancing is a regular aircraft maint. function. When I started to

look I didn't know of anyone in my area. After a little search I found 4

people who did this. Prices were from $175-$250. Takes about an hour.

 	  Quote: 	
		  

 Think of a dynamic prop balance that is not done like this. 

 If someone smokes cigarettes  or is a diabetic it does not take their

life right now, but over a long time period it causes many other problems
	


and an early death. A static balance only for your engine and gearbox is

not enough. My Warp Drive was static balanced at the factory, but way off

when mounted on the plane with hardware and running.

 	  Quote: 	
		  

 --------

 Roger Lee

 Tucson, Az.





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=155353#155353

randy(at)romeolima.com
Guest

Posted: Wed Jan 02, 2008 7:46 am Post subject: Engine Vibration

I'm just starting to lurk here as I consider starting a Kitfox Super Sport 

with a 912. In terms of prop balancing, our EAA Chapter bought one of the 

balancers referenced below and we make extensive use of it. This can be a 

great goal/project for a chapter, see the below link for details...

http://www.eaa105.org/Programs/programs.htm#PropBalancing



Our members LOVE this program, and reducing vibration helps extend the life 

of all components on the plane, especially in the FWF area.



Randy Lervold

www.rv-3.com

www.rv-8.com

---

hgmckay

Joined: 23 May 2006
Posts: 397

Posted: Mon Jan 14, 2008 2:13 pm Post subject: Engine Vibration

Roger: 

I have tried to find some one near here (Charlotte and or Hickory, NC) that

can dynamically balance my Allegro 2000 that has a 3 blade WoodComp prop. I

have found that no one will do it for a number of reasons two of which

follows:



1. They do not balance props that have a gearbox between the engine

propeller drive.

2. There is no place on the WoodComp aluminum hub to attach balance weight.



At least one shop said they would look at my plane if I would fly it down to

their shop. I don't fully understand why the gearbox and the gears would be

a problem. Anyway, right now I have run into a dead end on this matter, and

don't fully know why.



Hugh  



--

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