Flat Plate Axial Mill Part 4

[brianc4]

The following series details the assembly of the tail boom & stops.

I had placed a hole in the baseplate for the tail pivot pin to make an easy job of getting the pin in the right location.

Now all I need to do is get it set to 20 deg. angle and in the right centerline orientation for the 10 degree offset from the tail spindle to compensate for the 5 in. offset from the Yaw centerline.*I CAN'T THANK ENOUGH ALL THOSE WHO HAVE POSTED THE ENGINEERING RULES OF THUMB & WHAT HAS WORKED WELL FOR THEM ON THIS SITE. IT SURE HAS MADE THIS PROJECT MUCH EASIER!!  

In the picture below I show one of my favorite cad tricks to make layout easier. I print out a copy of my drawing at a 1 to 1 scale & lay the drawing on the finished part & center punch thru the paper drawing to transfer accurate reference points onto finished part.

Pictured below is the transfered centerline onto the baseplate.

Below I have the 1" dia. 4140 chrome moly shaft welded to the base plate.

Pictured Below is the DOM tube with the bronze bushings fitted in them that will be the tail boom pivot.

Below is the finished boom pivot with a wedge shaped piece of DOM tube welded to the baseplate to make up for the 20 deg. castor of the pivot shaft.

Below I am fitting up the main boom tube to the pivot.

The next pivture shows the bullet cap on the main boom tube (They are available from R.B. Wagner or KINGMETALS.COM) We use them alot on tube handrails & they make a great looking water tight terminaton for a round tube.

The next picture is of the completed tail boom.

Next is a picture of the tail. I cut it out of 11 ga. mild steel. Again I used some rules of thumb others have posted on this site 10' mill 5' tail boom length 5 sq. ft. tail area. I hope the 11 ga. isn't too heavy but with the ease that the boom pivots on the greased bronze bushings I think it will work out ok. Time will tell.

The next picture I am fitting up the tail to the boom.

The next picture shows another fabrication trick I have used extensivly in all of my flat plate artwork designs for benches & tables as well as in industrial applications. I bring all the contact area of mating parts down to weld tabs. This cuts down on the amount of weld needed reducing warpage, I dont have to lay out for stitch welds, and there are no laminated metal seams for rust to start forming in between!

The next Picture shows the completed tail & boom. Now I am ready to put on stops

Below is a good shot of the side stops & rubber bumpers that stop the tail at the unfurled position.

Next is a shot of the stops that catch the tail in the furled position.In the picture I had to pull the rubber bumpers off of the side stops & use them to set up the top stops. They are rubber suspension stops from Autozone & they only stock 1 set per store! I had to go to the next town over to get the second set that will be seen in later pictures.

Next shot is of the tail in the furled position.

Below is a picture of the completed stops & tail boom.

Since I had the magnet rotors on the spindle to test the cooling fins, I decided to put together a quick test stand to set the mill on so I could start to get an idea what the finished product is going to look like once it it up & flying!Below is a shot from the side.

Here is a shot from the front.

And from the back.

Once again I want to thank everyone who has contributed their time & knowledge to this site! I hope that my contributions & postings will help add to that knowledge base as well. I hope to get my coil winder & winding head cut today and I will post further progress as I get it done.

Brian Clark

[DanB]

It looks really nice!   I worry that the tail might weigh a lot - it may not furl.  Itd be interesting if you could tell us how much force against the spindle is required start furling.

[nunyabeezwax]

Brian,

great work!  What are your plans for getting wire down the tower?  Are you going to use a hollow spindle, slip rings and brushes or maybe I missed something?

John

[blueyonder]

 hi brian .your tail and boom are looking good.

  doing sum nice work there.

  its going to be a quality machine . and as its your very first one  your giving

it a nice bit TLC.

  i am looking forward to it flying one day soon.

   looks like your able to get sum hours on it of late.

   11 ga mild steel for the tail fin.  be better if that was alloy sheet.

   you also need think how the wires will get down the pipe.

  will you run dc to the battery room or box.  or will you fit the bridge recs

  on the mill.

   its great building a wind gen  . you get into problem solving at every stage.

    i have had no spare time to do any work on my mill.

   i feel guilty coming on here and posting comments .while all my bits are laying in my  workshop doing nothing.

   just catching up with so many other bits.

   every day i come on this forum looking to see what new.

  i wish there was a magazine to go with this hobby.  

   but this is just as good and its got great pics and all for free.

  i cant wait for your next update.   don't rush things .but i need more pics.plz.

   cheers john.

[GeeMac]

I must say the your knowledge of design shows when you employ the right tools for the job.  I too put my square and compass, among other tools of a craftsman, to good use and have a small urban mill in the back yard. You do good work and I hope to see the result here soon.

[jlt]

thats a great looking mill that you are building. I have a few  concerns about it.it should work. but would be better if you heed some advice given by others in the know.but experience is the best teacher. My advice is add some bracing to your tail.and make it have adjustable offset angle i think you will need .more . it will be easy now before it is up on the tower,and painted.

[brianc4]

Dan B,

 I have a good friend with a pull type fish weighing scale that goes to a 110 lbs. that I borrowed to set the furling on the PMG mill I built. As soon as I can borrow it again I will test to see how many pounds it takes to begin to lift the tail. If it is too heavy I figure I can trim down the tail or hole saw some holes in it to loose weight.

I used a figure of 99 lbs. of force against a 10' rotor at 15 mph. wind  to set the balance point on the PMG mill which was a direct blade furl design. It worked out real well. Does that figure sound about right for a furling tail design?

Thanks: Brian Clark

[brianc4]

John,

 I will bring the cord down the outside of the tower a few feet and enter the pipe tower just above the guy points. I have some good strain relief fittings & holders with a spring on them to support the cord. I will put a steel saftey cable that comes tight before the cord does just in case it winds up more than a turn and a half. I am taking out several acres of trees at my cabin and with a 40' tower I hope to be in clear air with very little turbulence.

 Brian Clark

[brianc4]

Blueyonder,

I understand completly about the difficulty in finding time to work on projects! I have to squeeze in a couple of hours here & there in between working on customers projects.

I have been trying to work with materials I have on hand for my first prototype mill in order to control costs. On future mills (I plan on building at lest 3 for myself) I may change the tail to a bolt on 3003 aluminum design if weight & balance is a problem or I may go with 4130 annealed chrome moly for the tail.

I plan on bringing the ac output to the battery shed & rectify it there.

Brian Clark

[brianc4]

Gee Mac,

Glad to hear that there are other "Crafstmen" with the wind bug! If you are ever in the Salem Indiana area stop by for a visit.

Brian Clark

[brianc4]

jlt,

Thanks for the input. This is my first attempt at a furling tail design and I realize some adjustment may be necessary. The rubber bumpers are a little over an inch thick and have plenty of room to be trimmed down if I need more offset or put some shims behind them if it needs less ofset.

Before the mill goes on its permanent 40' tower at my cabin I will put it up at my shop on a 25' test tower until all the bugs are worked out.

Brian Clark

[jmk]

 If you have your wires hanging outside for the first few feet and then entering the tower it will twist all up. How do you intend to keep them from getting wrapped around the upper part of the tower as the machine yaws in the wind?

[brianc4]

jmk,

I plan on using the law of averages! It will wind up until the saftey cable catches and sooner or later the wind will blow the other way! Not a whole lot different than running down the center of the tower except I will be able to tell at a glance how bad the cord is wound up.

Brian Clark

[kurt]

only problem with that method is there is a distinct possibility that the mill will end up stuck against its pendant at least partly facing the wind and unable to furl out of the wind during a high wind event. that would lead to catastrophic failure of the turbine.....

[jmk]

 It won't hardly spin counter clockwise at all. The low pressure systems will make it do one spin clockwise every time a low pressure system passes by. Will your wires be wrapping around the tower as it yaws? That will eat up any slack real fast and stop it from yawing, or rip your wires. That's why it's nice to send them down the top of the tower. Then they only twist together.  

[Flux]

Short loops of cable at the top of a tower don't work very well. I tried once and it was a pain. I ended up with a long loop a pulley and counterweight and that allowed about 10 turns but it was never a success.

Unless you can drop the cables down the centre you ought to think about sliprings.

Anything that prevents rotation about the yaw axis defeats your furling and so does a broken cable in that it results in overspeed with loss of control and braking.

[brianc4]

Flux,

I appreciate your & others input on the cable problem. That is the one part of the design I was not very happy with!

I had originally thought about slip rings & that is still a possibility. Another possibility is a hollow spindle that would let me drop down the center of the tower.

I really like the idea of slip rings so that there is no chance of cable wind up period. But I have seen alot of negative info about the use of slip rings due to high resitance & brush wear or breakage.

Any good ideas on slip ring design or better yet an available slip ring setup that can be adapted to a wind turbine?

I have made alot of single slip rings (in the 400 Amp range) for rotary grounds on welding turntables I have built for myself. They are a pain to build but I can build them from scratch if necessary. Any Input or ideas about slip rings would be greatly appreciated.

Brian Clark

[Flux]

Slip rings are something of a pain and best avoided for most people but they can be satisfactory if well designed and built.

You have the ability to build things properly so you should be ok especially as you have experience of welding slip rings. The duty is similar and if you can get things to survive for welding you should be ok.

You need good thick rings running concentric with reasonable bearings, the brushes need to be low resistance grade ( copper/graphite or similar) and they need good pressure ( higher than machine rings that rotate continuously). The best type of brush holders seem to be the ones where the brushes are fixed to the arms and spring loaded against the ring. Holders with brushes sliding in boxes are not well suited to non rotational applications with reversal of direction.

Try to use 2 brushes per ring and you will need good weather protection, they will fail without it. Failure usually starts as a poor contact due to corrosion of part of the ring in a wind direction where the thing rarely sits. This starts arcing and the destruction is cumulative with the  ring going out of round. You will no doubt have found the same trouble with welding turntables.

For normal machine applications oil is a disaster and must be avoided at all costs. For wind turbines there may be some case for a thin film of lubricant to act as a corrosion inhibitor but contact pressure must be high enough or you start a spark erosion process.

A hollow shaft with wires passing through may avoid the need for rings but they can be done satisfactorily. For the average person with limited facilities they are best avoided.

Flux

[brianc4]

Flux,

I will have to do some research on the arm type brush holders. I think I know the type you are talking about. If you could point me to any examples it would be a great help!

On the three welding turntables I have built over the years I used a 1" diameter graphite rod inside a 1" id. heavy wall tube. I isolated the tube with a phenolic mount & bushing and hooked the ground lead to the back of the tube. I had to use a very heavy spring as it was a part of the circut & had to conduct 400 amps as well. That might not be the best design with the spring in the circut but at the time I did not have an easy way to connect the wire direct to the graphite rod.

Let me know if tou think that design would be feasible for a wind turbine slip ring?

I had very good luck on the turntables using dielectric grease, the brand I use is from Trucklite and is used on electric connections on tractor trailers. I use it on all DC electrical connections on batteries & crimp connections.

Brian Clark

[Flux]

http://www.engineeringcarbonproducts.com/Brush_Holders.php

I hope this link works. If so it shows one of the common brush holders used for this sort of job.

Having the brush directly connected to the holder arm with no intervening sliding contacts or springs makes them much better for this application. If you build your own I would use carbon graphite brushes from starter motors or other low voltage motors rather than plain graphite, although at 48v graphite would be ok

I would try the rings dry but if you get tarnishing from the weather then try a thin film of the grease that you mention. At these low speeds it doesn't normally lift the brushes on a hydrodynamic film and the tarnish prevention may be better than not having it.

Flux

[Flux]

No significance in those italics, I did something and upset Scoop I think.

[brianc4]

Flux,

Linked worked fine. Thanks for the help.

Brian Clark