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Darren S

Well Known Member
No it's not a new app but I am having an issue with my -7 running rough. The stats: -7, IO-360, Hartzell C/S prop, 325 hours on engine and prop. Have owned since July last year. I put on 100 hours so far.

I usually cruise around at 22" MP and 2350 RPM. This give me the 65% power and the 9.3 gph that I like. She usually runs smooth at this setting. Started doing loops and rolls lately. That's about all that has changed.

I have an iPhone mounted on the panel that I use for music. It has a feature where if it is shaken the song will skip forward to the next one. It is mounted in a rubber cradle. Usually it is fine and doesn't skip. Then a week ago I detected a vibration at my usual setting. This was confirmed by the iPhone which keeps skipping at 22" and 2350 RPM.

If I run the RPM to 2450 there is less vibration, subsequently at 2250 RPM the vibration is worst.

I have read old posts on exhaust tips needing to be turned down or manifolds that could be loose or the need for rubber floor mats etc.... I have rubber floor mats and the exhaust has been checked.

Something has changed and I don't think running the prop faster (just because it is smoother) is the solution. The engine seems fine and runs within the CHT, EGT range as it always has.

HELP.

Somethings I've been thinking about. Does the prop need greasing ? I've never had the prop balanced. Can it go out of balance ? Did the Acro do something ? Do other's have a vibration in this same region ?

This issue is bugging me and kind of taking the fun out of flying at the moment.

Thanks for any help or suggestions.

Darren
 
more thoughts:

My alternator failed last month. The bracket was broken. Maybe the vibration issue has been going on longer than I thought and could have had a hand in the broken bracket ?

I have two Slick Mags. Run-up mag drop is about 100 RPM on one and 70 on the other. Could mag's cause rough running ?

Does what I've read about harmonics and certain Hartzell C/S props apply ? Is harmonics and vibration the same thing ?

Something is causing vibration when I dial the prop out (2250 RPM) and less at 2500 RPM. I don't think this is normal.

Thanks,

Darren
 
I would definitely have the prop dynamically balanced if it were me Darren - it may not fix your vibration, but it sure could - and you have to attack things one at a time. Smooth operation is better for everything, and I have been surprised how much a dynamic balance can smooth things out.

Paul
 
the prop needs greasing

well I dont know how much I can help you with the vibration issue with my limited knowledge but to answer your question if the prop needs greasing... this is what the manual says:

hartzell owners manual page 6-5
"...propellers be lubricated after the first one to two hours of operation because centrifugal loads will pack and redistribute grease, which may result in a propeller imbalance..."
probably not the issue since you have been flying for a while now, but who knows?
additionally..
also on page 6-5
lubrication intervals:
"...must be lubricated at intervals not to exceed 100 hours or at 12 calender months..." so yeah lubrication, come annual time, is a must (well according to the manual at least)
Good luck and keep us posted.

Marco
 
I took a second flight today and found that at 21.7" MP and 2380 RPM the vibrations were much less noticeable. Even the iPhone didn't skip....at least until I hit some turbulence :)

I checked into the operating limitations on the Hartzell site and all it said was to avoid extended periods of running under 2250 RPM and over 2600.

I am going to take Paul's advice and check into the Dynamic Balancing. I read a bunch of posts this afternoon and the pro's seem to outweigh the con's. I'll get the hub greased at the same time.

Didn't know about the iPhone vibration app !! Cool.

Thanks for the help.

Darren
 
The first time I flew with my iPhone wired into my intercom input, I found that I had one of the world's most expensive iPhone remote controls. Roll left, song skips to the next one. Roll right, song skips back.

Pretty cool, but of limited functionality.
 
2350 rpm

Darren, I have basicly the same set up as you and have had my prop dynamically ballanced but 2350 rpm is definitely the worst for me. Some friends have said the same thing with their 360s. I run at 2400 or 2450 where it is smoother.
 
Hey John,

Thanks for the feedback. I spoke to Hartzell today and they suggested that perhaps I should take a second look under the cowl and make sure nothing is loose and causing a vibration. They said that with an out of balance prop the vibs are worse as the RPM increases, not better. I will do so when the weather warms up.

What MP are you running ?

Thanks,

Darren
 
You should be lubing your prop annually. Be CAREFUL when you remove the grease zerk fittings. You can easily twist one off if you are not careful. Also do not overlube. My prop shop said this is one of the biggest problems they are seeing is people overlubing their props.
 
Just an update.

I pulled the cowl today after a flight. The vibes were still there. Kind of like a very fast, light, repetitive thumping in the floor board. When my feet are on the pedals I don't feel it, but when my feet are flat on the floorboards, it's there. I can also see my Zaon TCAS on the glareshield vibrating too.

So I pulled the cowl. I found that the rubber tubes that support the tailpipe were loose. The manifold is tight to the engine, no cracks, all probes are tight, all hoses etc... are tight, but BOTH tailpipes were unsupported.

I have a Superior 360 and there is rubber hose that has a hose clamp on either end. This rubber is suppose to add support to the tailpipe as well as offering some vibration protection, I figure. When it gets oily it seems that the hose slips off the rods that it is clamped to.

So I hope this is the source ? Norman in an earlier post suggested that this may be a cause. Sure hope so.

Darren
 
I have had those dam rubber hoses slip off many times before I changed the tubing and went with larger clamps.....also had the brackets crack and vetterman replaced them free....my 2Cents.
 
For the metal rods and rubber hose that support the manifold: I used the tubing flaring tool to flare the ends of the steel rods before slipping the rubber hose back on and then hose clamping. Seems to hold much better.

I'm still getting a little vibration that seems to settle out after about half an hour of flying. 2400 RPM seems better than 2350 and MP 21.5 vs. 22.

Maybe it's always been there and now that I notice it........I REALLY NOTICE IT.

Kind of like that noise your car makes, no one else hears it but you, and everytime you drive you can't NOT hear it :)

Darren
 
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