Author Topic: time for repairs (Read 17843 times)

kitestrings · « **on:** August 19, 2019, 01:12:43 PM »

The good news was brief this weekend, on the windmill front. The weather was spectacular, and I'd been wanting to attend to what I thought was more loose plating material that had started last summer on one of our magnets. Unfortunately what I found was worse. It appears that corrosion formed behind the magnet and it has now loosened from the magnet plate and is actually shifted out of its intended slot in the magnet retainer ring. This caused a minor rub on the stator, which from the ground I had thought was just a piece of plating. In hindsight, or hind-hearing, if it were, I should have recognized the sound of this magnet â€˜clapping' against the rotor plate at higher rpms. Fortunately it has been largely shut down for the summer months, so I don't think there was any permanent damage to the stator.

This the retainer, and how it should look:

Now, however, we've got a pretty sizable project. The turbine has got to come down, in whole or in pieces. I guess that is a pretty key first decision. I designed this alternator so that we could remove the blades, pull the stator, and take off alternator, leaving the head assembly and tail on the tower. This reduces the heaviest lift to about 135#, but it still is a fair challenge on the tower; probably more so putting it all back together. The easier method is to drop the whole unit, but that means a heavier gin and winch, or a craneâ€¦ urgh.

On a positive note, the turbine has been up for almost six years now and has served us pretty well. I'm thinking it is probably an opportunity to do a few other things:

1)   Check the other magnets
2)   Replace the poly carbonate stator rings, improve how they are fitted to avoid cracks
3)   Add a weather shroud of some sort to reduce rain/snow effects
4)   Refinish blades, reduce blade noise
5)   Repaint any exposed metal parts

kitestrings · « **Reply #1 on:** August 20, 2019, 10:35:25 AM »

The view nearly made up for the findings. I've calmed down a bit from Sunday's initial reaction. Could have been much worse. Perspective.

bigrockcandymountain · « **Reply #2 on:** August 20, 2019, 12:44:34 PM »

Wow. You live in a beautiful place.

Sorry to hear of your trouble. Hopefully you can get it fixed before winter. Lucky you caught it now rather than October.

phil b · « **Reply #3 on:** August 20, 2019, 04:36:00 PM »

A six year run with minor problems is excellent.

SparWeb · « **Reply #4 on:** August 21, 2019, 11:59:15 PM »

Quote from: bigrockcandymountain on August 20, 2019, 12:44:34 PM

Wow. You live in a beautiful place.

That's because he can see Canada from up there!

electrondady1 · « **Reply #5 on:** August 22, 2019, 09:05:54 AM »

kitestrings · « **Reply #6 on:** August 22, 2019, 04:32:09 PM »

Well, this is generally looking that direction (NW). The mountain in the background of the first picture is Jay Peak, a local ski pretty much on the border.

So, I've made one executive decision (as chief of my tribe), that is to take this down in pieces. Roughly in order:

1) Remove blade plates & blades
2) Remove stator
3) Remove front bearing
4) Remove magnet rotors and hub from spindle

I recently bought a small gin pole like this:

My plan is to fabricate, or modify mounts that will allow if to be secured to the head assembly of the turbine. So, behind and clamped to the spindle, and attached at the bottom just above the yaw bearing.

I think with this device, a bottom sheave, and one ground person this can all happen.

kitestrings · « **Reply #7 on:** August 26, 2019, 12:25:03 PM »

So, this arrived Friday.

I cleaned out the bearings and re-lubed. I think it will work well. I'm modifying the mounts to suit. Here's the lower mount before mod...

during...

and after...

I still have to complete the hinge/lock and fabricate a clamp for the top section. More to come.

SparWeb · « **Reply #8 on:** August 26, 2019, 11:24:38 PM »

Looks like that had to be cut with a big round shell-saw. Reallllly slowwwwwly...

kitestrings · « **Reply #9 on:** September 04, 2019, 09:46:20 AM »

A little more work on the gin pole over the weekend...

Excel-CAD plan

Parts and pieces

This thing, with original hardware is rated for about 3,800#. I want to be able to lift around 135#. I think this should work. Going to try taking down just the alternator; a test of the concept of a removable stator.

And, the other view. Looking toward the east, Mt Piscah and NH

Bruce S · « **Reply #10 on:** September 04, 2019, 03:49:25 PM »

Great view!!

zracer · « **Reply #11 on:** September 07, 2019, 06:52:54 PM »

Serious rig there, Kitestrings. Looking good. How much power does it generate in the winter?

wbuffetjr1 · « **Reply #12 on:** September 08, 2019, 07:49:57 AM »

Looks awesome! How tall is your tower!?!?

kitestrings · « **Reply #13 on:** September 11, 2019, 03:03:05 PM »

Sorry for the delay -

Our winter average form the wind is about 250-300 kWh a month. I'm sure it would be more if I left it unattended more. I tend to shut it down when I'm not around, and nights with screaming high winds. I sleep better.

The tower is 86' high.

I tried out the new gin on Monday. Took the blades off; alone. The kids got off the bus just in time to save me untying the last two. It worked really well. It is the right size and in an ideal location.

I thought the blades looked pretty good overall (especially having now seen Sparweb's

Next up, well next down is the stator. Cross your fingers...

SparWeb · « **Reply #14 on:** September 12, 2019, 02:06:56 AM »

They look better than my old blades!

How are they holding up?

kitestrings · « **Reply #15 on:** September 12, 2019, 08:19:08 AM »

The blade finish,and finish in general, has held up really well. There are a few sections where I applied a clear 2-part epoxy a year or so ago (without removing blades). So, those need sanding and finish at a minimum. there are also a few cracks like this one on the trailing edge to be dealt with:

I probably will take the time to take the trailing edge down a bit more on all of them and refinish. they are down and this is the time to do it I guess.

The bigger problems are:
1) the magnet that jumped the tracks. It looks to be only the one from what I can see. It may just be a case of moisture getting a foothold behind the plating on that one.
2) the stator rings. You can see the cracking. I'm thinking to replace them, this time with stainless spacers and clearance for heat-shrink to account for the dissimilar expansion rates. I'm still open to a stronger material. A bit higher modulus of E would help, and something that I knew for certain wouldn't crack would get my vote.

SparWeb · « **Reply #16 on:** September 13, 2019, 12:58:26 AM »

I think I do see the cracks in the first of your 11-September photos. Coming from the bolt so it's pretty obviously stresses at the point of concentration.
Can you confirm that it is only the plexi covering that is cracked, and nothing in the stator itself is damaged?

SparWeb · « **Reply #17 on:** September 13, 2019, 01:06:37 AM »

And just as a reminder - my own memory can fail me - this is the thread where the cracks were discussed:
https://www.fieldlines.com/index.php/topic,149818

kitestrings · « **Reply #18 on:** September 13, 2019, 08:31:57 AM »

Quote from: SparWeb on September 13, 2019, 12:58:26 AM

Can you confirm that it is only the plexi covering that is cracked, and nothing in the stator itself is damaged?

Yes, that's right...and the link you referenced is where we discussed it. To be consistent the material is Makrolon AR; not [sic] pexi.

I think many of the comments were accurate. I suspect the cracking - thru and thru - stems from:

1) over torquing the rings without spacer/stops.
2) dissimilar expansion rates between the metal connectors and the poly
3) the jack-hammering effect of the alternator, particularly when the waveform is being clipped

Unless I learn something new, I'm lining up new rings with spacers. The larger spacers will be nominal SS 5/8" OD x 1/2" ID, with ~.035" clearance for shrink wrap. The smaller holes, which are alternately between the supports, will have a 1/2" delrin (or possibly ultem) rod/insert that extends thru both the stator and the poly.

I haven't decided on the belleville washers...I will probably try them, but I'm not positive there is clearance to add these plus flat washers.

kitestrings · « **Reply #19 on:** September 13, 2019, 11:09:24 AM »

I was thinking that I may be able to use these, with washers, and shims to provide the shear fastener and the stop in one (2-piece) component:

https://www.mcmaster.com/97851a105

SparWeb · « **Reply #20 on:** September 20, 2019, 04:59:42 PM »

As long as you can get the length just right.

No thread lock. Coarse thread. Meh

kitestrings · « **Reply #21 on:** September 23, 2019, 11:02:12 AM »

One of the goals of our alternator design was to be able to remove the stator, and then the magnet rotor assembly without having to either take the whole turbine down, since the only other option would be to jack apart the rotors on the tower. This would be impractical at best; dangerous at worst.

Here are the pics of our progress over the w/e.

kitestrings · « **Reply #22 on:** September 23, 2019, 12:41:42 PM »

And, here is the reason this had to come down...

You can see why they are all covered with iron dust

SparWeb · « **Reply #23 on:** September 23, 2019, 10:22:49 PM »

Ewwww

You have identical replacements, I hope?
Hey, you previously asked about different magnet alloys. What have to settled on using?

MattM · « **Reply #24 on:** September 23, 2019, 10:40:00 PM »

If only you had some steel c-channels to spot weld into that steel ring prior to setting the magnets in. Could even have tabs to keep them from sliding out or to act as a pan for the epoxy to set up around them. Were those ferrite magnets?

kitestrings · « **Reply #25 on:** September 24, 2019, 12:31:26 PM »

So, it is odd that it seems to have only affected the one magnet; in a dire sort of way. I wonder if moisture got behind the plating perhaps thru a nick or defect in the plating.

I don't have any spares laying around, but there are a few choices:
CMS makes this size, in N42, but with a counter-sunk center mounting hole. They also make this size in a N45 which would have about 8-10# more pulling force than the others. I'm not sure I like that option.

A match is available thru another supplier; Applied Magnets.

Matt the stainless magnet rings should have held them in place, but the corrosion caused the block to expand and eventually warp the bottom surface. The finish to plating was still in tack, but the plating lifted from the magnet.

The leaves are turning fast. I gotta get cranking...

Bruce S · « **Reply #26 on:** September 24, 2019, 01:33:56 PM »

KS~
From looking at the early posted pics, if those two magnet backing plates side line up, then you might have a closer look at the stator and the backing plates the mags are mounted onto.
They almost look like there's some kind of warpage going on. Look at the mags and where the what I see as scuffing. Almost like you had some sort of point of contact. Not enough to tear the magnets off but just enough to cause scuffing that lead to the 1 mag to get as bad as it did.

It could be something a simple as the jack screws being 1 thread off.

Still great views!!!

Bruce S

kitestrings · « **Reply #27 on:** September 24, 2019, 01:51:48 PM »

I think what you're seeing is where I made a poor attempt to refinish some of the magnet faces, and ends. As this magnet started to fail, some of the plating peeled away. I initially tried sanding with emery and applying some rust inhibitor. The plates are gapped to pretty close tolerance with spacer shims. There's also some grease that mixed with the magnet dust that made a mess, but appears to clean off pretty well with gorilla tape and cleaner.

MattM · « **Reply #28 on:** September 24, 2019, 04:57:39 PM »

Ionic transition from the magnets to the stainless is likely your culprit. You need an insulator sandwiched between the dissimilar metal.

kitestrings · « **Reply #29 on:** September 25, 2019, 08:03:42 AM »

Hmm. The rotor plates were separately prep'ed, primed and finished with an epoxy paint. It seems odd that this would then occur at only one magnet out of 32.

MattM · « **Reply #30 on:** September 25, 2019, 09:45:00 AM »

The epoxy would have been an insulator unless there was some kind of blemish or crack below the magnet.

SparWeb · « **Reply #31 on:** September 26, 2019, 10:25:40 PM »

I suspect a flaw in the paint, too.
The evidence is lost now.

kitestrings · « **Reply #32 on:** September 27, 2019, 12:24:32 PM »

I thought I would re-torque the bushing that holds the stator bracket on the spindle. ?The only minor challenge was that all the socket-heads were plugged by mud-wasps.

I also bought three new magnets (so I'd have a couple spares). I went with the N42 with the center holes. I thought this would be the best match to the existing magnets, and it is the same vendor.

News:

Author Topic: time for repairs (Read 17843 times)