Lessons Learned

[luv2weld]

One of the things I learned was----the typical yaw bearing

(pipe over pipe) without something to spread the weight and the

wear is not a good idea. I've seen other postings here that confirm

that. It doesn't take long for the end of the pipe to wear through

the flat plate that's supporting the weight of the generator head.

My solution is a 4 bolt flange bearing. Add a couple of pieces of

angle onto the bottom of the yaw so that the bearing has a flat

surface to bolt to.

Set the bearing so that there is a clearance of 1/4 to 1/2 inch

(6 to 12 mm) between the end of the pipe and the flat plate stopper.

Paint a white line around the tower stub at the point where the bottom

edge of the bearing will sit. The white line will tell you if the

bearing has slipped and the pipe is once again rubbing on the flat

plate. It's visible from the ground, so you will know without having

to lower the tower and check.

The next thing I learned was to install a grease fitting on the side

of the yaw bearing. I tried greasing the tower stub and then slipping

the yaw over it.

No matter how I tried, I always  ended up scraping half the grease off

with the end of the stub. The simple solution is to install a grease

fitting (or 2) during the building of the yaw. Put the yaw on the stub

and pump the grease gun until your arms hurt. You don't end up looking

like a greased pig! I don't have a picture of the grease fitting.

The lesson that really hurt was the one that cost me a set of blades.

The tower stub needs reinforcing where it meets the tower. My tower

is 4 inch black pipe. The stub is 1 1/2 inch  black pipe. It never

entered my little brain that it would need bracing. The end

result can be seen in these pictures.

The stub was constructed of 2 large washers and the 1 1/2 inch pipe.

One washer, welded to the bottom end of the stub, slid into the 4

inch pipe. The other washer, about 18 inches up the stub from the

first was welded to both the stub and the top of the 4 inch pipe.

I just knew that was a very secure joint!!!  Wrong!!!!!!

Here is a picture of the broken stub after it was cut from the

top of the tower.

I now know that you either need some triangle shaped braces or

another piece of pipe inside of the tower stub.

At the time mine crashed, I didn't have any 1/2 inch thick plate

to make braces, so I opted for putting a piece of 1 1/4 inch pipe

inside the 1 1/2 inch tower stub. Those 2 pieces are welded together

on each end. Then the washers are slid over the 1 1/2 inch pipe and

welded into place. Then the whole assembly is slipped into the 4 inch

tower and welded.

That way if the 1 1/2 inch stub cracks and breaks where it

meets the tower, I will have a little help from the inside pipe. It may bend, which is

my warning that something is wrong. That way I can lower the tower and fix it .

Hopefully without destroying my blades again.

I hope these things will inspire others to show the lessons that

they have learned.

Maybe  we should have a section titled "Things I Learned the Hard Way!!

Ralph

[thirteen]

At work we have bearings that are to high to reach easily so we put a platic grease line down to where it is easy to get to. No 1 grease cold weather no.2 grease warm weather. Something this might work the $$ is fairly cheap and they can be made flexible. The line won't go 360 but could come close. Just an idea.

[richhagen]

luv2weld, I think posts like this are among the most educational posts, because they show the results of things that can go wrong and propose solutions.  I would have though nothing bad of using a tower stub of the design you originaly had.  I am guessing that the heat of welding made the pipe more brittle next to the weld as well. Thanks for sharing.  Rich

[richhagen]

One other note on the bearing.  I have some similar appearing flange bearings, and if I recall correctly the rated load parallel to the axis of rotation was only 15 percent of that perpendicular to that axis.  I wonder about how long they will hold up under this type of loading.  I know DanB had some thrust bearing designed to take loading in that axis, and I had wondered about tapered roller bearings for a yaw type of application because a pair of them should be able to handle a fair bit of loading both perpendicular and parallel, although I don't recall off hand seeing anyone using any for a yaw bearing, and the cost for the sizes required might be prohibitive.  Rich

[Flux]

Radial bearings are not intended to support much in the way of axial thrust but in these conditions they should be perfectly adequate, the thrust loading is not high for the large size of bearing.

Thrust races are ok as are angular contact ( expensive solution) I tend to use taper rollers to support the weight and keep things centred ( which ball thrust bearings won,t do easily).

On the only machine I have fitted with a full set of slip rings I used taper rollers top and bottom but the lack of frictional damping makes it rather inclined to wag around in turbulent winds.

I agree with something to take the vertical thrust and tend to use a taper roller at the top, the rest is sort of pipe on pipe but with a plastic or Tufnol ( Resin bonded linen) bush at the bottom end although most of this comes from my engineering background, as long as you keep grease in there plain pipe on pipe will last for many tears.

With any form of ball or roller bearing in these set ups it will work as long as you keep grease in and water out. If the thing starts to rust it will be no better than a steel plate sitting on the end of a pipe and may fail sooner.

Flux

[jlt]

I have  had the same problem  of not turning  very easy it worked well for 6 months. and now will not turn into wind until it's very strong.I'm trying to find a throw out bearing to fit inside a 3 1/2 inch pipe .

[Dave B]

I have a 16' and ran an 18' also with a thick bronze washer I cut to fit at the tower top. The pivot top and of course the stub top are welded steel plate with the cable hole bored, this gives the flat surface area for the large washer (bushing) to be sandwiched. Make it as close to the pipe diameter as you can and if you have a decent slip joint of pipe over pipe with minimal slop then all greased up works fine. I favor the bit of friction to yaw the machine, I'll check and grease it during the regular inspection but from what I had seen before this makes a very good thrust bearing. It actually seems to get better with time with a very smooth surface and very little sign of wear, not a concern for me with close to 250 Lbs of machine up there. Dave B.

[DanB]

Yes, I have to agree with Dave...

a thrust bushing/bearing at the top is necessary - especially on turbulent sites, although I know some folks have gone for years with nothing like that - it always fails here (its turbulent here).

A good pipe over pipe yaw bearing is OK though, so long as it's greased - Dixie posted recently about their failure with the 15' turbine, the yaw pipe did wear out, but it took 4 years with no maintenance and Im afraid the machine was built very ligtly (I'd use much bigger/longer pipe for the yaw these days).  Some friction is nice there I think.  Although - you're solution with the bearing looks workable.  I worry a bit that if the bearing fails it could prevent furling - a very simple/sturdy pipe over pipe arrangement should never seize even if it wears out badly ~ so long as there is a bushing at the very top.

Not sure if this is a 10' machine or not - but - if it is, I think also part of the problem with teh stub snapping off is that its too long.  The stub should be just about the same length as the yaw bearing itself, looks like this one is quite long, and 1.5" pipe is not strong enough to support a machine that large in my opinion.  I'd not have less than 2.5" sched 40 pipe from the top guy wires to the yaw bearing itself - then a smaller pipe for the stub would be OK.

[cdog]

I think your'e on to something!!!!

Cdog.

[Ungrounded Lightning Rod]

Two comments:

1) If you have a single yaw bearing it should be about as high as the center of effort of the turbine's drag, i.e. near the turbine axis.

This is especially true when the bearing is narrow and a press fit on the mounting pipe:  The drag of the wind is applied via a lever arm corresponding to the distance between the center of effort of the wind from the bearing.  As the wind varies the shaft wiggles back-and-forth in the bearing - eventually working its way out.

With two bearings placement is not so critical.  The leverage turns into side thrusts in opposite directions (both below or both above the center of effort) or in the same direction but at possibly different strengths (one below and one above).  The "tapered yaw bearing above the turbine axis, pipe-over-pipe below it" approach is such a two-bearing situation.

2) The narrower a pipe (or other beam), the weaker it is.  Your two-inch pipe inside the four-inch pipe is much weaker in bending than the outer pipe and prone to falilure.  And it did fail - at the maximum bending-stress point (at the upper ring).  You should have used two large pipes, not one big and one small.  Or done the reduction immediately below the yaw bearing (with the latter about the height of the turbine axis).

[cdog]

I used a piece of 2" shaft, turned the ends down and used 1-15/16 bearings, and bored a hole 1" through the center for the wire to go through.

No problems so far, been up since february,

Cdog.

[luv2weld]

Thanks to all who have taken the time to read and respond to

my ramblings.

I will attempt to answer the responses so far in this one posting.

I used what I had on hand for the tower and generator.

I had the flange bearing in the barn, so I used it.

The pipe in pipe was used because it was a quick fix and I had it on hand.

I also think the 1 1/2 inch pipe is too small.

And the stub is too long.

All these corrections are on the list of things to do. But as

most of you know, it takes time to get to these things.

Have been looking for larger pipe for a while now. I only go

to town about once a month, ( and to the big city about once

every 3 months), so it takes a while to find salvage steel and pipe.

I have been thinking about the thrust bearing concept as mentioned

by DaveB and DanB. What I was thinking was using a thick piece

of HDPE (1/2 inch or so) as the washer instead of brass. Our

Canadian friends call this puckboard.

Has anyone already tried this?

Ralph

[electronbaby]

Ive never used HDPE, but I have used a 1/2" thick teflon bushing and it works great. I use it on all my machines now. I grease it as well. I welded up an insert out of stainless that fits into the top of the tower stub snuggly, and the upper surface is machined and polished. Then I lay on the teflon bushing and slip the yaw tube down over it. There are 1" holes bored through the stainless insert, the teflon bushing, and the top of the yaw tube where the feed line passes through.

Ive never had a problem. Teflon can take the compression that a heavy machine will give you. HDPE will not. Its too soft in my opinion.

[tmcmurran]

The fracture could have been excelerated by the heat from the weld at the collar.  I have done pretty much the same, but placed a good three to four feet inside the larger section filled with cement.  Makes for a very heavy tower, but has removed all vibrations.  I am in the process of moving this tower, and once I head back out to the house will take a few photos.

But I do agree that extra support from the upper and lower portions can never hurt.  The stonger your support, the less problems you will face. :-)

[harrie]

Rich. My 22 foot duelrotor has had the taper roller bearings in it now for over a year. The turbine weighs in at over 500 lbs and has never had a problem, and I dont expect one. Photo below is had to see, but has a bearing at the top, and another one at about 16 inches down. The only thing is that it turns so freely that the turbine will yaw back and forth with turbulance which i wasnt too fond of, so I installed a spring loaded pin with a hole flange to hold it into the wind. the pin is operated with a 1/8" cable from the bottom of the tower. Those of you having trouble with furling may want to try this, cause it will not let the turbine yaw while furling. A picture of this is also below.

[SparWeb]

Sorry I didn't get this posted sooner.  I must have hit "preview" instead of "post".

Here is a drawing of the yaw mount I built last year.  I actually don't know what tapered bearing part number I did use, but the FAG part number was handy.  I'm sure you can find a cheaper bearing that would work fine!

At this point, I think the compression fitting would work, instead of the series of pipe fittings I actually used.  I think an even better third option would be to use the cable relief straps - neat things but I haven't got a picture handy.

Using one tapered roller bearing, instead of a mounted ball bearing on the stub, you have a lot less heavy hardware up there, too.

One limitation with this design is that the grease going through the roller bearing flows into the stub, and falls to the bottom.  Probably not a big deal, but you can't just pump the grease gun until is comes out the buffers at the bottom.  It will never happen!  I guess I haven't completely solved the grease monkey problem.

[luv2weld]

Not only are you a generator builder, you're an artist too!!

Nice drawing.

Thanks for posting. I think I'll be using your idea.

Ralph

[SparWeb]

Actually, my original background was as a draftsman.  Have 1000's of hours at AutoCAD by now.  Moving toward Solidworks now.

Reminds me that the career counsellor at school gave me a written aptitude tests and informed me that I was best suited to become a sculptor...

[frackers]

Here is another one - took it down yesterday when I noticed it wasn't yawing properly as the wind got up.

This is a picture of the stub mast that goes up into the yaw bearing, the top thrust plate of the bearing has a groove about 1/16 deep in it after only 6 months of flying but it too deep in to get a clear picture of it! You can clearly see the steel filings stuck into the grease making a thick paste that stopped it from turning.

I guess I'll be looking for Teflon sheet now...

[Ungrounded Lightning Rod]

Ever seen how a "fifth wheel" trailer mounts into a pickup truck bed?  There's a hitch system mounted into the pickup bed that's much like the one on a semi-tractor, only smaller.  (About a foot across.)  This is a plate on a bearing that lets it rock for-and-aft, with a little pie section cut out of it and a latch below it for the hitch pin.  The trailer has a hitch with a down-pointing pin (about an inch across) and a matching plate.  The truck plate is covered with thick grease.

Downside is that, when the trailer is not hooked up, you have this plate covered with grease in the truck bed.  Imagine what happens if you tether a dog back there...

There is a product to solve this problem:  A thick (maybe half-inch) Teflon washer that goes where the grease would go.  It has fingers in the inner hole that makes it hang onto the trailer pin when they're not connected.

One of those would provide all the heavy teflon sheet you'd need for several top-of-the-pipe-on-pipe teflon bushings.