vibrations

[Johns]

Am getting a vibration which seems to coming from the prop. This has just started within a couple hours of flight time. Prop has about 26 hours on it. I checked the motor mounts and they seem ok, I also re-torqued the bolts. Checked the tracking and have about 1/4 to 3/8 inch. Instructions call for 1/8 inch. Maybe I could remove prop, inspect hub, if none replace prop and re-torque? Thoughts?

John

[SonexN76ET]

Check out this article on propeller tracking:

http://www.ultralightnews.com/pilotslounge/propellertracking.htm

You may want to let your propeller sit untorqued for an hour for the wood to expand back to its original shape before starting the tracking process.

When you do your final torque values do not forget to add the torque for the friction of the nylon on the stop nuts (about 2 ft lbs).

Jake

[Johns]

Thanks Jake, good article! Seems I did wrong.

John

[kmacht]

You dont mention what engine but if an aerovee a quick check of the bolt that ties the prob hub to crankshaft wouldnt be a bad idea. If its a new issue that is just showing up after 26 hours it doesnt seem like it would be due to prop tracking. Look for things that might have changed, moved or loosened over time.

Keith
#554

[Johns]

Good thought Keith, it is a VW 2300 with a force one prop hub. Will check!

John

[Area 51%]

Hot and humid this summer. If you have a wooden propeller, don't leave it with the blades vertical. Moisture will migrate to the lower blade and can cause an imbalance.

[Johns]

Hot and humid this summer. If you have a wooden propeller, don't leave it with the blades vertical. Moisture will migrate to the lower blade and can cause an imbalance.

Never thought of that one. It has been very muggy here in the north east.

Is there supposed to be any wiggle room while hand turning the prop? While rotating the prop I noticed a little movement (maybe 1/8 inch) before I the insides started to move.

John

[EdW]

All good suggestions, but tracking sounds out of limits. "Real" airplanes usually max out at 1/8". Usually tracking check is first item of troubleshooting for engine vibration.

If it wiggles, it is loose...check bolt holes for wear, out of round. How was the torque on the bolts? Any quite loose? What kind of prop? Does the mfg have provisions for bushing the bolt holes?

Don't be afraid to take the prop to a prop shop. They usually aren't all that expensive, and have the experience you need. Some even work on composite and wood props.

Ed
Onex 209 in work
N???NX
Kahki Kyak (?)
Just east of Graceland

[Johns]

Ed, I agree it could be the tracking but as Keith mentioned it was fine for the first 24 hrs then I noticed it (vibration) slowly getting worse. Has anyone heard of a force one hub going bad?

John

[kmacht]

Has anyone heard of a force one hub going bad?John

The only one I am aware of on a Sonex was Jack Lockamy (N164JL) way back in 2002. He had a type 4 not a type 1 VW conversion though. Great Plains issued a service bulletin on it but it was only applicable to the type 4 crank/hub.

http://www.greatplainsas.com/service2.html

I would still highly recommend pulling the prop and taking a close look at the hub and the bolt that attaches it. Also, there shouldn't be a 1/8 of movement anywhere when turning the prop. It should be a solid connection all the way from the prop to the hub to the crank and to the pistons. If you are seeing slop anywhere in that chain you need to figure out where it is coming from.

Keith
#554