KAM
Well-Known Member
Having changed the bearings and balanced the blades I am now looking at adding some vibration isolating mounts. Has anyone tried this already and did it work.
Wind turbine noise and vibration reduction
- Thread starter KAM
- Start date
jakeroyd
Well-Known Member
I know something of curing vibration having been close to it in the Automotive design discipline.
To 'cure' or reduce vibration you must either isolate it (hence the rubber mounts etc) or change the frequency/order of what is vibrating.
This means instead of fitting rubber mounts it may be of value to try changing the mass of the pole by clamping a weight to it.
This will act as a mass damper and will change the natural frequency of the whole thing.
Vobration may find it's way to the boats structure along the supporting wires also so you could try these.
It's easy and quick to experiment with this before you fit mounts.
You can't change the frequency/order of the input/excitation since that is a product of things like the number of blades and the number of segments on the commutator/brush/slip ring unit etc.
To 'cure' or reduce vibration you must either isolate it (hence the rubber mounts etc) or change the frequency/order of what is vibrating.
This means instead of fitting rubber mounts it may be of value to try changing the mass of the pole by clamping a weight to it.
This will act as a mass damper and will change the natural frequency of the whole thing.
Vobration may find it's way to the boats structure along the supporting wires also so you could try these.
It's easy and quick to experiment with this before you fit mounts.
You can't change the frequency/order of the input/excitation since that is a product of things like the number of blades and the number of segments on the commutator/brush/slip ring unit etc.
ianabc
Well-Known Member
Ampair shipped me a unit that vibrated.
Purchased new blades...
no better
THEN
a machinist who lived aboard at the dock suggested that a test on the hub would tell if the hub was warped.
On a windless day, putting a piece of chalk on the edge of the hub and rotating the hub showed that the hub was 1/4 inch or more out of alignment.
When the unit was shipped I believe the hub was not properly protected.
Purchased new blades...
no better
THEN
a machinist who lived aboard at the dock suggested that a test on the hub would tell if the hub was warped.
On a windless day, putting a piece of chalk on the edge of the hub and rotating the hub showed that the hub was 1/4 inch or more out of alignment.
When the unit was shipped I believe the hub was not properly protected.
wizard
Well-Known Member
On my Rutland 913 I used the strengthend rubber exhaust support strips (about 10mm thick by 150mm long) that hold up exhaust pipes, cut suitable lengths to go under the two pole hull brackets and did the same for the two support poles as well- stopped 90% of the vibration transmitted through the hull from the pole. Only cost a couple of quid and 6 years later they are still OK with some oxidation around the edges of the rubber.
The next thing I tried was tying rope between the pole and pushpit at varying heights and tension - bingo - last 10% cured.
Good luck
KAM
Well-Known Member
Thanks for that. I assume the bolts were not isolated and you just passed them through the bracket and deck with the rubber sandwiched between. I was thinking about doing this (after being unable to source a cheap AV mount with stainless attachments) but thought there would still be transmission through the bolts. Ill give it a try as its a nice simple solution. In the meanwhile I thought I had better look at the blade hub after ianabcs post. I found the hub loose on the shaft. Last time I checked it a few years ago I needed a big puller as the hub had welded itself to the shaft. It came off with a big bang. The LVM instructions say to grease the hub. I think that was a mistake as it's only held on the shaft with a through bolt and it obviously came loose some time ago. I am now looking for a new BREEZA hub. Anyone know where to get them they used to be very cheap at one time but can't find a supplier now.
