BAD vibration!

[KFWG]

Just put my 912uls gearbox back on after a professional overhaul with a new gear set.
I’ve got a 3 blade Warp Drive taper tip prop and I think my spinner was Warp Drive made (front plate).
Zero damage to prop or spinner.
Blade pitch is within .1 degree of one another.

I’d been noticing a worsening vibration and decided to get my gearbox overhauled.

Using rented dynavibe I started testing today.

With spinner on…..get ready for it:
1.7 ips !!

Removed spinner….…
.4 ips

Removed and rotated prop 180 degrees and still .4 ips

Prop balanced statically using Buzz Master and it balanced nice and level.

Checked blade tracking and have found 1 of 3 blades is about 3/16” off.
I saw on another forum that Warp Drive says 1/2” is max!!!

I’m stumped. To boot, carb sync shows it’s perfectly synced.

Will be checking prop flange tonight.
Obviously the spinner has issues so we’ll table that for now.

Any thoughts?
First flight after gearbox overhaul was not enjoyable. No flying until this is diagnosed.

[Birdseyeview]

I just chatted with Warp Drive about run out tracking and they told me that 0.125" was the max limit. They also said that when you reassemble a prop that has been off the engine and/or blades realigned for pitch that it takes a few high speed runs to "seat" each blade in the hub. I took that to imply that it might track better after a few run ups.

Sounds like you have a spinner that is out of balance, so I'd try rotating the spinner into different locations (if it's configured to allow it) to see if any other location reduces the out of balance condition.

[jrevens]

You need to get the tracking, blade pitch and anything else like that taken care of before you use the DynaVibe and dynamically balance it... with the spinner in place of course. You will be checking and adding weight to balance that complete spinning assembly, which includes the prop and spinner. It's not unusual to have a spinner that's out of balance and causing vibration. If you have to disassemble the assembly for any reason, it's important to reinstall everything back in the same position as it was before, to help insure that the assembly remains in balance.

[KFWG]

My opinion is that prop balance/vibration should be amended before I tackle the spinner.
Even without spinner Dynavibe says it’s gnarly. I
disassembled the prop and no evidence of damage/cracks on hub and blades are COMPLETELY free of damage or bug buildup.
I further removed gearbox and confirmed crankshaft true (after replacing main gear during gearbox overhaul)
I confirmed prop flange is well within spec.
Either it is blade tracking or something else going on.
To correct a .4 ips would still take a lot of weight!
Will repitch and tighten things up in next few days and check tracking again.
As I said before, pitch was within .1 degree between blades.
This is my second Dynavibe test on plane (last in about 2013). Last time was able to get it well below .1 ips.
Hoping for just a tracking issue.

[Shadowrider]

I don’t think tracking will cause that bad of vibration. So your plane flew great and then you started to notice a vibration. Took the gearbox off and had it overhauled. Installed it and now you have severe vibration? I don’t think I would be looking at the prop, but the gear box or engine? Seems like you have something else going on. Try a friends gearbox? Do you have egts? All cylinders running fine? Leak down check? Maybe running engine with no prop. Just some brain storming ideas?

[efwd]

check your engine manual first. I believe it is ill advised to run without a prop on a Rotax? I could be wrong but it seems I read that someplace.

[Shadowrider]

Rotax can run without a prop you just have to be very careful to not over rev it. Not sure it would tell you much though?

[efwd]

Thanks Dustin. As easy as my engine exceeds 5800rpm with a cruise setting on my prop (in flight), I can imagine how easy it would be to exceed rpms without a prop at all.

[Rodney]

I'd like to jump in here and suggest the following testing.

1. Put prop on - run up to 3500 rpm - record amplitude AND phase angle.

2. Pull the prop - again run it up to 3500 and record amplitude and phase angle. (This would be with the gearbox)

3. Pull the gearbox - run it up to 3500 and record amplitude and phase angle.

Once you do these three tests you will have eliminated the prop and the gearbox. Only thing left is the engine.

If you are careful with the throttle there should be no reason to overspeed the engine.

IF after checking without the gearbox and prop - you find you still have a high level of vibration in the engine, run the test two more times, shutting down the engine
for a short time between tests. If the phase angle stays the same, whatever the problem is in the engine - the parts are not moving around. Let us see your data

Match mark the parts as they come apart so they can be reassembled in the same manner as they came apart.

Regards
Rodney