Vibration victim

P

PhilW

New member
Hi Guys,

My recently restored 1950 Cruisemaster (0470 installed in the 70's) has a vibration issue. The problem becomes apparent after takeoff as I bring the prop back to square-up with the m.p. As the prop becomes more coarse the vibration becomes more 'intense'.

The prop tracks O.K. and I recently had it dynamically balanced. The as-found balance level was 12.5 mm/sec (0.49 ins/sec), after balance the level was 2.6 mm/sec (0.102 ins/sec). The tech that did the analysis noted other peaks related to cylinder firing order harmonics were normal. Balancing seemed to help but did not eliminate the problem...it remains uncomfortable to fly.

The vibration does not seem to be related to speed.

Any thoughts?

Phil
 
A wild stab, but how old are your engine mounts? We did the dynamic balance thing on our -3, still had a bunch of vibration. Replaced the engine mounts (they weren't in great shape, it was time) and it got significantly better.
 
Phil did this just start or has it been an on going issue? I'm guessing that the engine install is a field approval and used the original O435 mount. Has the mount been changed and did you take a good look at all the welds? I once worked on a 172 with bad vibs and it was a cracked mount.
Lynn the crate :shock:
 
There's no way to mount an O-470 on a O-435 mount......
As the BMEP increases I think your plugs are breaking down. Even if your plugs are new, check them for resistance. They're junk if they are over 5000 ohms. Champion has been putting out marginal to bad plugs, new out of the box.
Let us know what happens.
Dan
 
If the blades are out of pitch relative to each other, one can balance 'til H freezes over - and nothing. Been there done that.

The freq of this type of vibration will be 1 cycle per rev. If your vibration tech picked up this vibration you are concerned about, he can tell you what relative freq it is. If it is the 1 cycle per rev type, pitch asymmetry might be worth looking into.

Ron Marks
 
Thanks for the suggestions.

Lynn; this is the first time I flew with this engine; it's a 0470 mount, NDT'd before installation.

Dan; I just replaced the plugs with new Champions...didn't check the resistance, but I will now.

Ron; the prop was overhauled in 2004, balanced in 2005 (suggests the original owner was having a vibration problem), inspected in 2010 (only had 7 hours since 2004). If a simpler (less expensive) solution isn't found I might have to send it to a shop.

Thanks again,

Phil
 
Phil is it possible to index the prop? Does the vibration start only when leaving fine pitch? Got to figure is it the prop or the engine causing this. Lynn the crate :?
 
Lynn, I'm quite sure the prop flange has a locating pin. Yes the vibration seems to start when leaving fine pitch and becomes more intense squaring-up.

Here are a couple pictures of the beast.

Phil

bellancamaidenvoyage030.jpg


bellancamaidenvoyage025.jpg
 
Hi Phil,
Beautiful plane!!! A couple of thoughts on the vibration, the current edition (May 2013) of "Light Plane Maintenance" has a great article about trouble shooting engine mounts. A couple of things they mention can occur with new mounts.
1) Shanked out - Insufficient shims used when installing and mounts are torqued to bottom of threads and leave play in mount/engine mating area.
2) Insufficient torque - torque was lost when backing bolt off for cotter pin
3) Mount differences - According to Lord, their mounts are designed specifically for the aircraft/engine combination and differences include things like mount hardness. Check to ensure part numbers match application.

Don't know if that helps or not. Good luck!

Jack
 
Phil, still trying to help. Going back you first mentioned recently restored but the install of the Opec 470 was in the mid 70s. Was something changed in the recent restoration such as the prop? You mentioned new mounts and they are specific Lords. Was the prop O/H? Most times it is the little things that kick your tail. This is a thought. The Crusair boys use a hoist and sling on the prop to do a retract test. You might try that trick on your beast and see if the engine and mount move as you apply pressure. Desperate men do desperate deeds! Lynn the crate :?:
 
Thanks again for all the ideas.

Dan, I checked the resistance of the plugs...all O.K

Gary, the plane has flown 10+ hrs since it was returned to service. In the next week or so I'll be going through it with a fine-tooth comb. I'll use that opportunity to check-out the mounting bolts. The Lord mounts are the ones specified for the 0470.

Lynn, the engine and prop have been together since the '70s. The prop was O.H. in 2004. The original owner had it balanced in 2005, and put 7 hours on it. I bought the plane in 2005 as a project and took the plane out of service...didn't even fly it. In flight the fabric on the wing would bubble up. The prop was removed and put in dry storage. In 2010 the prop was inspected. It was returned to service in 2012. I recently had it dynamically balanced as described earlier. I'm having the tech out again Wednesday to 'explore' the problem further.

Hoist the plane by the prop? Would I wrap the sling aft or forward of the tag that says 'Do not pull on propeller'? :D

Phil
 
Cruisairs are NOT hoisted by the prop, but as shown in Fig 3 of the "Handbook of Instructions". The sling method is supported aft or near the firewall, don't actually remember exactly where it is. Dan, can you help?
I have jacking points built in to my forward spar that work really well.
Larry
 
Phil,
Any hoisting should be done from the rear of the engine mount.
The lord mounts on the "K" engine installation in the Bellanca are the ones listed for the "J" engine in a Cessna 180....strange, but that's the way THIS "K" engine is installed.
The prop indexing on the crankshaft situation hasn't been addressed as far I can see.
Are the blades indexed in the hub correctly?
Did you check the spark plugs under pressure?
Dan
 
Other thing I wonder about is it a real vibration or an engine miss. Dan mentioned checking plugs under pressure, also what happens of you run on one mag? Did you check the harness too when you checked the plugs?
These kinds of problems drive you nuts chasing them. Good luck and please keep us informed. Larry
 
Trust Dan to throw the fox into the chicken coop...the table I have specifies J3804-14/15's for an 0470K in a Bellanca 14-19-2. Naturally that's what I installed. For the same engine in a C180, J6545-1's are needed. Just to confuse things more, my engine is a 0470L...???

Am I wrong thinking that the pin on the flange leaves no opportunity to rotate the prop?

Checking the indexing of the blades on the hub will come if all else fails.

The plugs were not checked under pressure...is that essential?

Larry, I don't think it's an engine miss; but of course I could be wrong. The engine starts easily and idles smoothly. On run-up the mag drop is <50 rpm both sides. I have not tested the mags in flight.

Phil
 
After a phone call, I think Phil is on the right path as far as solving the problem.
I think what happened back in '55 when Northern first investigated putting the Continental engine in the !4-19, the "J" engine was the peak of development at that time and the engine mount was designed for that engine. By the time the airplane was ready for certification and production, the "K" engine was in production. It had 5 more HP. and different mounting "legs." It was easier to swap out the mounting legs to the old style than re-engineer the mount. This is why the "K" in the Bellanca uses different Lord mounts than a Cessna 180/182 with a "K" engine. The "L" engine is the same as the "K" with a change in the induction system.
Anyone out there have any thoughts as to my reasoning on this matter?
Dan
 
Phil, as it now reads we have an O 470L with Hartzel prop installed with O 470K Lord mounts in your plane. The vibration starts as you increase pitch on the prop and gets worse as you attempt to square the numbers. Is this the correct sequence of events? Does this happen only in the air or does it happen on the ground? It would seem to be that as the prop is causing the vibration and if decreasing the pitch the vibration goes away again looks like the prop. I know this is very frustrating. I would look at trying a different prop to see if that fixes the problem. Desperate men but then you would know. Lynn the crate :?
 
Hi Lynn,

You summed it up perfectly.

I can't detect the vibration on the ground during a normal run-up. This Wednesday when the vibration tech comes by we'll do a ground run-up in fine pitch and 24 inches mp then bring the prop back to square and see if he detects anything unusual. When we did the test last time it was all in fine pitch.

Phil
 
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