vibration at 4000 rpm

[zoobie]

Good afternoon fellow flyers.

Am hoping one of you can assist me with a vibration issue on my aerie.

I have a Bushbaby taildragger with a Rotax 582 Blue top and E series 3.47 gearbox...both relatively new.

Prop is a wooden 2 blade DeNekker 72" x52...it was recently redone by Oom Pieter..totally refurbished and rebalanced and is 100%..tracking is also within manufacturers specifications.

I also had it balanced on the plane by someone from Rand airport using some fancy equipment.

Everything is 100% and smooth except between 4000 and 4800 RPM...at this rpm I get one hell of a shudder/vibration coming through the airframe.. Its really bad and very uncomfortable.....it feels like when you stick your head out of a car windows at high speed...you get this huge shudder.

Once above or below this RPM, it is smooth again and a real pleasure.

Oom Pieter De Nekker asked me to rotate the prop by a few degrees/ bolts..which I have done...same problem.

Carbs have been balanced using vacuum gauge, plugs changed, new rubbers fitted, etc...

Besides buying a new prop, or finding someone who will loan me a 3 blade warp or similar to compare, and see if its the prop or something else, any ideas as to what is causing this?

has anyone else experienced this with the above setup?

many thanks for your assistance

Joe

[pit bull]

joe,

I am not an expert!!!!!!
but yust thinking................ gearbox ?........... engine mounts .......?...........spinner, ?
hope you get it sorted

regards
pit bull

[nicow]

Ask the nice people at the factory at Petit to loan you a prop and test it...

[LoneRunner]

Hi Joe, did you sort the vibration you had and what was it??? Just curious on this side as it sounds rather than something like a dynamic resonance you experienced

[zoobie]

hi all

I did solve it to a certain extent.

After much frustrations, I again changed all the engine rubbers to stiffer ones.

I also made sure that absolutely nothing, not even a spark plug lead, throttle sleeve was touching the cowlings/frame. Seems to be 90% better.
thanks for all the feedback and suggestions.

safe flying

[Tumbleweed]

Is this during flight or only during warm-ups?

Reason I'm saying is at the holding point during mag checks, on certain occasions I heard a terrible noise- headsets off/ vibration and after aborting, remove cowels e.t.c, noticed that at a specific angle to the wind i.e. nose not perfectly into the the wind, the propwash blasted air through the vents into the canopy creating the 'reverberating (sp)' similar to opening a back window whilst driving.

Felt like a do@s but problem sorted.

[zoobie]

mine was very prominent at about 4000rpm

I also initially thought of that...tried everything. I think mine were the engine rubbers.

[Tumbleweed]

Next time after warm-up checks, turn aerrie cross wind, do checks and see if it happens again.

[witwillem]

I had the same problem when we fit a ebox , tried every thing til we change the big rubber donut between the engine an the geerbox , ja no problem noe with a bluegum tree or a warp drive it was there , when we put a other 3 blde it go away, when we put the newrubber cupling in even with the p prop it is gone , the rubber get old and is( verwring) weeti wat is dit innie rooi taal , maar die swaar props maak so , change the coupler an you will see witwillem

[zoobie]

ok..thanks...will give that a try.

cheers