Author Topic: 10' Turbine Tower Stub Questions (Read 6140 times)

arwenvaughan · « **on:** July 21, 2009, 11:09:56 PM »

I am begining to build the tower stub now for a standard 10 foot Homebrew Wind Power turbine. I am trying to figure out the best way to do this since it is not really covered in depth in the book.

The book does say to use 2-1/2 inch schedule 40 pipe for the yaw bearing and 2 inch pipe for the tower stub, but it seems like there is a lot of play (1/8 inch) between the inner diameter of the yaw bearing and the outer diameter of the tower stub. has this been a problem for anyone? I was also thinking there would be a lot of metal on metal wear at the bottom of the yaw bearing since there isn't a bushing of any kind.

I was wondering if anyone has tried somthing a little different with some sort of bushing down the length of the tower stub...

I was thinking of making the tower stub out of 2 inch tube and then sliding 2 inch PVC over it to create a bushing between the yaw bearing and the tower stub on the sides. I would still put a bronze thrust bearing over the top of yaw bearing. I guess you would then grease the entire thing up. Would PVC hold up for a while, or would bronze work better? Would axle grease cause the PVC to deteriorate for any reason? Do you see any flaws in this design?

As usual, I really appreciate any help. I promise to stop bothering everyone with silly questions as soon as this is finished....well at least for a little while

electrondady1 · « **Reply #1 on:** July 21, 2009, 06:11:08 PM »

hi arwen,

i am not that familiar with what is the standard practice .

according to your drawing, all the weight of the turbine will be resting on that small area equal to the cross sectional thickness of the blue pipe.

that could lead to a bit of wear on the bronze after a time.

if a small end cap, mimicking that which you have depicted on the black pipe, was welded to the blue pipe it would spread the load over a larger surface area.

how did your wife like the gazebo idea?

fabricator · « **Reply #2 on:** July 21, 2009, 06:39:10 PM »

I did something similar to your drawing, but I also have a tapered roller bearing at the top, your drawing should be fine, providing you can find the right size pvc to fit.

Shadow · « **Reply #3 on:** July 21, 2009, 06:42:44 PM »

Your pvc idea may work fine, I use a nylon? bushing where your bronze one is. It takes a long time to wear into the 1/4 inch thick nylon.Its either nylon or some sort of polproplyne? After 2 years it never showed any noticeable wear.

If you want to spend the money, there is a pipe that fits snug inside your 2 1/2 inch pipe, but its like $12.00 an inch or some outragous price.

bzrqmy · « **Reply #4 on:** July 21, 2009, 07:25:23 PM »

Looks good to me. I built mine per the book. It still bugs me about the steel-on-steel. It works fine as it is, but I think that the next time I take it down, I will slide a nylon or bronze thrust bearing where you have yours shown. I figure I will go 2.0" O.D, 1.125" I.D. by 1" thick.

I had a problem with my original build where the tail was fighting the blades and the whole thing was yawing back and forth. I am wondering that if there was less friction in the yaw bearing, that the problem bight be worse. I changed the angle the tail sits at unfurled to be parallel with the hub shaft and the sea-saw effect is much reduced. It's nice to see this thing stay pointed in the wind and keep producing power.

wdyasq · « **Reply #5 on:** July 21, 2009, 08:10:39 PM »

UHMW is a plastic that is inexpensive, has a low co-efficient of friction with steel and can be machined with hand tools. Many prefer it to bronze on bearings that will be difficult to lubricate. It is only a bit less 'slick' than the Teflons.

eBay will have 'chunks' for sale.... maybe even reasonable in cost.

Ron

arwenvaughan · « **Reply #6 on:** July 21, 2009, 08:14:28 PM »

Hey electrondady1..good to hear from you. The wife liked the gazebo idea about as much as she likes not being able to park her car in the garage anymore...because I use it build wind turbines

She ignored me today when I told her it would cool to turn the spinning merry-go-round at the park into a giant VAWT. Women...

Oh, about the picture. I think the bronze will be loaded mostly on the cross sectional area of the red pipe. I found some really high gauge 2 inch pipe that slides right into 2 inch PVC and it would make good contact for the bushing...I think. I'm making this all up as I go so we will see.

Ungrounded Lightning Rod · « **Reply #7 on:** July 21, 2009, 08:19:35 PM »

I'm thinking of putting a clutch throwout bearing there. Cheap at auto supply stores, intended for thrust in the right direction, has a hole down the middle for wires, etc.

arwenvaughan · « **Reply #8 on:** July 21, 2009, 08:20:35 PM »

I really like the tapered roller bearing...oh now I am jealous. That looks really nice. This looks like a big boy so it probably is really good to have a bearing. It looks like you just tacked an angled steel insert of some kind it into place for the roller bearing sit in...good idea. Where did you get that...was it something you bought or made? Also, are those nylon bushings and how are they attached there to the tower stub?

arwenvaughan · « **Reply #9 on:** July 21, 2009, 08:32:44 PM »

Ahh, I have notice you mention this stuff before and I was trying to remember what that acronym was. Cool, I'll look for this stuff. I'll check out eBay too. Does anyone else have a good source on the internet for various plastic and bronze bushings? I was going to order a bronze bushing from the Dans but I didn't see any for sale on their website.

dlenox · « **Reply #10 on:** July 21, 2009, 08:35:25 PM »

arwen,

I am using a throw-out bearing from 1932 Ford to act as thrust bearing at the top of the stub. Many others can be available that may suit your dimensions.

Also arounnd the stub you can put some .060' steel to act as a bit of a spacer. Provided you put in some grease it will rotate around the stub very easily.

My total weight of the turbine/rotors/blades/etc is easily 250lbs and the combination of the clutch thrust bearing and stub spacers work out very well. The whole unit rotates nearly effortlessly without the need for tapered roller bearings.

KISS and in the long haul it will pay off.

Dan Lenox

wdyasq · « **Reply #11 on:** July 21, 2009, 08:43:58 PM »

http://www.use-enco.com/CGI/INPDFF?PMPAGE=842&PMITEM=319-4783

I have had good luck with ENCO stuffs. Not affiliated, attached at the hip or relative of the company. MSC and McMaster will probably also have it. It is NOT listed in my KBC tools index.

Ron

prasadbodas2000 · « **Reply #12 on:** July 21, 2009, 10:27:46 PM »

I have used a steel disc/cap welded to inner pipe top and the similar cap welded to outer pipe rests on the first one. So basically 2 steel discs (with grease between them) relatively rotating on each other.

To make up for the clearance between the pipes (I used 2" NB inner pipe 60 mm OD and 3" NB outer pipe with 88 mm OD and approx 80 mm ID - that gives almost 10 mm radial clearance) I got welded a 15 mm wide 8 mm thick strip ring at the lower edge of the inner stub pipe. So the lower end of the outer pipe (so to say skirt) touches this ring while the whole thing turns.

(tried to draw a sketch but not sure how it looks)

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Dave B · « **Reply #13 on:** July 21, 2009, 11:20:41 PM »

I'll throw my 2 cents in here also. Previously I purchased plate bronze stock (oil impregnated) from McMaster, I think it was 1/2" thick and not cheap. I cut a thrust washer out of this using a 3 1/2" hole saw (that was exciting) and I think 1 1/2" saw for the ID also. A welded plate on the top of the stub and outer pipe to sandwich this in there and I was lucky to find 2 pipe sizes that fit with very little play.

Greased the whole thing up and after a year took everything apart and looked it over. The bronze bushing was as smooth as glass with very little wear, I bet this would last 30+ years easy. The only noticeable wear and this is very little bacause of my close fit of the pipes is at the base of the outer pipe on the inner stub, this is where the outer pipes inner edge rocks against the stub. With all this greased annually it's not even an issue.

My 16' machine is a good 250-300 lbs. and riding on that bushing the past year has been very smooth. Dave B.

Flux · « **Reply #14 on:** July 22, 2009, 01:04:44 AM »

If you are not an engineer and want a machine to work then the original pipe on pipe idea works perfectly well.

If you come from an engineering background you will find it hard to tolerate the crudity and you will want to introduce various changes.

If you keep the basic pipe on pipe then I would at least think about something to take the weight, the bronze disc is fine but it is certainly a good idea to increase the bearing area beyond that of the pipe end, a steel washer welded on the end to increase area will prolong the life. The tapered roller or a clutch thrust bearing will also work perfectly well.

A bit of clearance between the pipes doesn't really matter but again you may wish to introduce some form of bush. PVC is far from the ideal material but again will be good enough. In various machines I have used loaded nylon " nylatron" ( Polypenco) and also phenolic bonded fabric ( in UK usually known by the trade name "Tufnol"). most other bearing plastics will do just as well.

Don't bother with any of these mods unless you have suitable facilities, the basic scheme is good enough and will last for quite a few years, it also provides significant frictional damping. If you do clever mods you loose this damping. On a good clean site it will make little difference but on a more turbulent site it will do far more tail wagging than the simple damped machine.

Coming at this from an engineering point of view I was very doubtful about this simple pipe on pipe yaw scheme but I have gradually realised that it has some advantages and for those without full engineering facilities or knowledge it has much in its favour.

Flux

frackers · « **Reply #15 on:** July 22, 2009, 05:27:58 AM »

I had a metal on metal bearing as per the book but after 6 months the top of my stub mast looked like this and there was a 1/8 deep groove in the top plate it was bearing on - yes, thats iron filings embedded in the grease.

I'm using a material like the Tufnol that Flux mentioned but 'tuffer' and its been turned into an inverted top-hat shape so that its an interference fit in the stub mast and the bearing surface is about 1/2 inch wide onto the flat plate of the yaw bearing.

imsmooth · « **Reply #16 on:** July 22, 2009, 08:29:32 AM »

I used the Yaesu GS-050 Thrust bearing. It is about $45.

SparWeb · « **Reply #17 on:** July 22, 2009, 02:16:23 PM »

Here is a diagram of my tower yaw mount:

SparWeb · « **Reply #18 on:** July 22, 2009, 02:22:04 PM »

Oh, and you can find cheap bearings for this job - much cheaper than the FAG part I just put on the drawing. Next step down it Timken, next step down from that is made in China. Any one would work.

I don't think anybody mentioned it, but putting a bearing in there reduces friction so much, that you may find the windmill twitching about left and right all the time. Maybe it won't matter with some high-inertia props like the 10' from Otherpower. It was fine with my 8' last year.

arwenvaughan · « **Reply #19 on:** July 22, 2009, 04:36:21 PM »

Very nice!! Wow you guys have done this in a lot of different ways. I am not sure which way to go now. I'll probably try it out with a plastic bushing and see how that goes. If it looks like there is still a lot of wear and tear then I will add a actual bearing. Thanks again for all the good ideas. I hope this thread helps some other people out too.

Thanks!!!

fabricator · « **Reply #20 on:** July 22, 2009, 07:52:57 PM »

The bushings are delrin, I rolled up the bearing holder, the bearing is 1" ID, the bushings are held in place by small stainless tabs welded to the stub.

scoraigwind · « **Reply #21 on:** July 24, 2009, 03:47:38 PM »

It's a good idea to put some greasy washers in there because a thin pipe will certainly wear a groove in the top plate over the years and tend to jam up. Bronze, brass, plastic, all good so long as it doesn't disintegrate and jam up. When you start with roller bearings, be much more careful. These things need protection from moisture and they also need very precise machined alignments. Under sloppy installation conditions they will fail and break up and jam solid.

A well engineered roller bearing yaw (machined and sealed) will last OK but you will have a lot of untwisting to do to your wires and the machine will yaw idly around a lot in light winds. If you go high tech then why not do sliprings too. But why bother doing all of this if some greasy washers work fine? When you do it the low tech way there is also no need to worry about large gaps and rattling fits. Why worry? It works, and that is what matters. If it rattles then balance the blades.

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Author Topic: 10' Turbine Tower Stub Questions (Read 6140 times)