vibrations
Posted: Wed Aug 01, 2018 9:07 am
by 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
Re: vibrations
Posted: Wed Aug 01, 2018 4:18 pm
by 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
Re: vibrations
Posted: Wed Aug 01, 2018 5:11 pm
by Johns
Thanks Jake, good article! Seems I did wrong.
John
Re: vibrations
Posted: Wed Aug 01, 2018 8:19 pm
by 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
Re: vibrations
Posted: Thu Aug 02, 2018 5:20 am
by Johns
Good thought Keith, it is a VW 2300 with a force one prop hub. Will check!
John
Re: vibrations
Posted: Thu Aug 02, 2018 9:55 am
by 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.
Re: vibrations
Posted: Thu Aug 02, 2018 10:09 am
by Johns
Area 51% wrote: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
Re: vibrations
Posted: Thu Aug 02, 2018 10:25 am
by 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
Re: vibrations
Posted: Thu Aug 02, 2018 1:23 pm
by 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
Re: vibrations
Posted: Thu Aug 02, 2018 2:49 pm
by kmacht
Johns wrote: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
Re: vibrations
Posted: Thu Aug 02, 2018 4:49 pm
by Area 51%
If the slop you’re talking about is between the prop and hub…seek professional help. If it’s internal, it could simply be the bearing clearances, rings swapping sides of their grooves, or the flywheel-to-thrust bearing clearance (in this case, the beveled timing gears allow the crank to move fore and aft before anything else moves).
Re: vibrations
Posted: Thu Aug 02, 2018 6:50 pm
by Johns
I’m Thinking it’s between the prop and the hub. Is this something an A+P could look at?
John
Re: vibrations
Posted: Thu Aug 02, 2018 7:21 pm
by EdW
Johns wrote:I’m Thinking it’s between the prop and the hub. Is this something an A+P could look at?
John
Find one with grey hair, or an antiquer…they’d be more likely to have recent/decent knowledge of wood props..Find a Sensenich authorized prop shop and call them.
I’ve been an airplane mechanic going on sixty three years, but am not authorized to work on a prop, so all I do is look, say “OMG” and call the prop experts. I’ll say it here; call the experts!
As an aside, can you give us pics/video? The more we know the better off we are.
Ed
N???NX
Onex 209, tentatively called the Kahki Kyak
Just east of Graceland
Re: vibrations
Posted: Thu Aug 02, 2018 7:55 pm
by Johns
Ed, I’m thinking of the force one prop hub, not the prop itself. That might be part of the engine.
John
Re: vibrations
Posted: Thu Aug 02, 2018 10:27 pm
by mike.smith
Johns wrote:Checked the tracking and have about 1/4 to 3/8 inch. Instructions call for 1/8 inch.
That’s way out of limits! Fix that before you worry about much else.
Re: vibrations
Posted: Thu Aug 02, 2018 11:17 pm
by EdW
mike.smith wrote:
Johns wrote:Checked the tracking and have about 1/4 to 3/8 inch. Instructions call for 1/8 inch.
That’s way out of limits! Fix that before you worry about much else.
AGREED!
Re: vibrations
Posted: Fri Aug 03, 2018 7:06 pm
by pete 212
I have a t4 with a special crank from SCAT , the nose was left un machined from them, it was then done to match the f1 hub . I had to replace the oil seals and it took ALL of a 12ton press to break it loose, I then lapped with valve fine compound to make sure, then the crank went in the freezer the hub in the sun 120deg outside then put it all back together, I don’t expect it come off without a fight . pete212