15' footer upright and turning

[kitestrings]

 

I put in a switch that if it over speeds it comes on putting extra load on it to help control it.

This is also what we do with the Classic.  The Aux ports can be configured for a variety of settings for load diversion, vent fan control, gen start up and the like.  On the PV Active High (PV voltage actually, in this case it is wind input voltage to the controller) you can set it to add load at a given voltage, and keep it on until it drops below a selected lower voltage.  Works pretty slick.

I couldn't seem to open your picture.  Can you just resize it and attach it?

SparW, I hope to put a small streamer on the end of the kite/tail vane.  It is purely aesthetics, so it is low priority, but I was reminded of it when I saw your photo with the ribbon.  Was there any concern it might tangle in the blades, or is the end of the tail beyond the blade tip?  Hard to tell from the photo.

~ks

[Bruce S]

Strangeness on the zip file, was in a continuous loop when trying to open it.
, Sorry but I had to remove it.
Bruce S

[SparWeb]

...Was there any concern it might tangle in the blades, or is the end of the tail beyond the blade tip?  Hard to tell from the photo...

Just don't make it long enough, and you can use a fragile kind of ribbon that would tear if anything did snag.  The end of my WT's tail is pretty far from the tip of the blades, even when furled.

[ontfarmer]

Thanks Bruce for your help. 

[kitestrings]

A spinner and a streamer are on the to do list, but still a ways down in priority.

ontfarmer, that works.  Good looking machine.  Have you posted any details here?

The stop on the tail is set at near 60 degrees.

And that keeps it under control even in high wind events?  There are times where a real high wind will turn ours (typically under cut-in rpm) but fully furled is within ~5% of being parallel with the plane of the blades.

~ks

[ontfarmer]

The 60% was from the shaft so that would 30% from the blades. I started with it parallel kept pushing the stop back to where it is now and in higher winds or gusty winds I can keep
it running getting maybe 2/3 to 3/4 power from it while the tail is latched. Before I had to shut it down. If the wind is to high and I have to shut it down ( shorted ) to will turn very
very slow.   Grant

[kitestrings]

Grant,

Nice looking turbine.  From a distance it looks similar to a build Chris Olsen's been using, where the alternator is offset on the other side of the yaw axis form the blades.  You can see his write up here:

http://www.fieldlines.com/index.php/topic,147278.msg1017926.html#msg1017926

If you have time try to post a story on the details of your project.  I'm sure others would be interested.  Regards, ~ks

[kitestrings]

I'll bet not too many people have had this problem...

Well, I said I share experience on this project, both good and bad - this weekend a bit of a setback I'd say.  Nothing fell down or got smoked, and no one was injured, so I guess I should keep it in perspective.  I checked out the turbine this weekend, on what's been one of the few really nice days since getting through our sugar (maple) season.  We'd had a steady, but predictable wind Saturday.  I'd stopped it a couple of times by shorting phases via the controller.  All seemed normal, so I thought I'd have a look-see and grease the tail hinge and yaw-head.

Everything looked pretty good except, as you can see, the coil sectors have shifted.  I picked out the worst one that I could see for these photos:


Torque on the stator, perhaps braking, perhaps just normal load & vibration is causing the sectors to rotate and slide along the T &G joint


I loosened the mounts and was able to tap things back into position.  Retightened and we're operating for now.  The winds are starting to drop off seasonally a bit now anyway.

Thinking about it two possible solutions; I welcome others:

1)   I could drill and add a second through bolt in each coil.  The original design had two; in hind-site I probably should have left it.  Similar to this:


2)   I wonder about the possibility of flipping the stator.  The sections are rotating about the stator bracket mounting bolts.  And, compression at the inner part of the sector seems to be causing the neighboring sector to shift outward on the unrestrained side.  I wonder , if it were reverse, if the same compression would end to tighten or bind against the next sector(s), while the arm of the bracket would be in tension.  Here's a flip photo for a visual:


Glad it made it through the winter, but got to work this out.  I welcome suggestions.  ~ks

[SparWeb]

Can you bond the sectors together?
I'm surprised they aren't.  I remember your posts last year - they stuck together with quite a bit of force.  I didn't notice you were relying on that.

It's more likely the braking torque than the running torque, but either way, the torque on the stator can be broken down into # fractions of the torque, per sector.  It wouldn't be a relevant calculation if you hadn't made your turbine with the coils in separate segments, but you have, and they appear to be free to move relative to each other.  To estimate the torque isn't too hard...  I can't remember exactly so assuming there are 12 segments, max power is 2kW and it hits that power at about 300 RPM.

2 kW / 5 rev/sec = 400 Newton-meter = 295 foot-pounds
295 foot-pounds / 12 sections = 25 foot-pounds per section = 295 inch-pounds per section
Bolt offset from edge approx 1 inch
295 inch-pounds per section / 1 inch = 295 pounds per joint shear force

Yeah, they're going to slip.  Even I guessed wrong, a few % here and there will still lead to some big slipping forces.
It won't matter which way they face.

I just got thinking of a few types of woodworking joints that might work as a retro-fit, if you don't want to bond the joints.  Basically the kind of knife-edged staple that you hammer into picture frames at the corners from the back, but in this case nothing so violent.  Maybe all it would take is a 1/8" round pin drilled and inserted through the tongue-and-groove joints, then they couldn't slip.  To separate the joint, push out the pin first....
...stainless steel round pin...
...heck maybe even a wood dowel would be better...
...don't nick the wire...

[CraigM]

I like the pin / dowel idea. Perhaps use a spring pin / rolled pin to provide insurance against slipping out due to vibration.

[SparWeb]

Yes, as long as there aren't too many metallic parts introduced into the stator.  It's a tiny pin, but there are twelve of them.  Or more - I don't remember exactly how many sectors there are in his stator.

[Smithson]

KS:    You could use use stainless steel hose clamps (water hose clamps, several joined together) around the circumference of the stator if there is room where the leads come out of each coil.  The biggest I have seen are 7 inches so it would take several.   Or just use the ss strap that you used to keep the magnets from flying out.  Just a wild thought.  Arch

[Frank S]

If you were to decide to use a large SS hose lamp, these folks can help
http://www.hoseclampkings.com/Cat-52-1-38/make-a-clamp-kit-410-ss-screw.htm

 They have clamps up to 9549 inches in length

[kitestrings]

Thanks folks.  Some things to consider here.
 

Can you bond the sectors together?

Well, I hope not to.  A large part of the motivation for this was to allow the stator to be removed independent of the magnet rotors.
 
SparW, help me understand one thing if you would.  I'd run a similar torque calculation, not because of this but because I was looking at the torque on the keyless bushing and the amount of material (wall thickness) needed at the hub.  But, I'd made the overall torque at only about 140ft#.  IIRC it was (approximately) 5,000 watts/ 746 watts/hp = 6.7 hp; 6.7 hp x 5252/ 250 rpm = 140 ft-lbs.  Clearly I'm missing something, because with the numbers in your example I'd be under 50 ft#.
 
The dowels/pins might work, but there's only about 3/16" in the T& G section, so it would have to be quite small.  Oddly, I started with two fasteners on each sector, but I was trying to reduce the amount of metal near the fringe of the magnet influence.
 
If it is not clear there are two 2" wide polycarb rings on either side of the stator at the perimeter.  It would be pretty straight forward to add another 1/4-20 bolt (like every other one is now).  There are 12 sectors; six attaching to the stator bracket assy.
 
Art, Frank, the ring/bands isn't so crazy, but the terminals and bushings use up pretty much all of the available real estate on the edge of the stator.  Might be clearer here:
http://www.fieldlines.com/index.php/topic,147846.msg1024042.html#msg1024042
 
As near as I can tell they never moved until I messed around with braking, but good to know now, rather than in a high wind event.  Gotta chew on this one.  I knew there be some good input here.
 
~kitestrings

[Frank S]

OK, then how about drilling in at an angle around the perimeter you already know which way the segments are trying to shift . drill a small hole maybe .250  or what ever you think you have room for.
 go from the segment that was low @ about a 45 deg angle about 3/4 inch back from the tongue & grove joint  into the adjoining segment. If concerns about adding metal then use something like Delrin dowels  or even wood furniture dowels  being at an angle the dowel would prevent slippage unless sheared 

[midwoud1]

KS.

To avoid element shift make the second bolt in the plex. ring .
The dowels in the centre part of the stator ,like Frank S mentioned.
Straight or angle drilled.
I see in the kite shops in the Netherlands polyester round stock 3 mm,4 mm ,5 mm
diam.
Alltogether it will make it compact and avoid slip and shift.

 - F -

[Flux]

I think I would go for the extra bolt as originally planned, it seems to be fairly well outside the main field of the magnets and I see no signs of heating on the existing bolts.
I also suspect braking is the main problem, things may settle into a stable position and not cause trouble, but if things become loose I worry about individual coils vibrating and causing fretting. The total stator torque is nearly smooth but individual coils will experience the same problem as a single phase winding.

Flux

[kitestrings]

It won't matter which way they face.

I'm still not sure this is true.  I potted two spare sectors and I was playing studying things a bit more.  In the first two photos we're on the back side (downwind) of the stator.  The direction of rotation from this perspective is counter-clockwise.  When we brake, the force is in the same direction, but it is tending to swing the sector so that the unbolted opposite corner is rising up and out of the T&G keying.  If you picture it now spinning the opposite direction the arm of the stator bracket is nearly in line with the right-hand side, and resists any outward movement.  The inner most section is now pushing against the left-hand side of the next sector.  It may be an optical illusion but somehow this looks better to me.  It might help to see a single coil in place:


The rings are actually not pexi-.  They are a material called Makrolon (polycarbonate); 3/16" thick.  It is much stronger material, and applications include glazing (non-glass architectural glazing, skylights) and machine guards - like on your bench grinder (that you pull off first thing).  In shear, they are rated in the 8-10kpsi range.  I also formed the wire bends on a jig, just for consistency, so the location of the wires should be predictable.  There's nearly the same space on each side.


Frank, we are using Delrin bushings in every other coil sector to reduce form ~1/2" to the 1/4" through-bolts.  it's nice material to work with.

~ks

[SparWeb]

Oops -

2 kW / 2 / pi / 5 radians /second = 64 Newton-meter = 47 foot-pounds
47 foot-pounds / 12 sections = 3 foot-pounds per section = 47 inch-pounds per section
Bolt offset from edge approx 1 inch
47 inch-pounds per section / 1 inch / 2 sides =  24 pounds per joint shear force

Torque during normal operations much lower than I estimated at first.  What do you think the torque would be during braking?
(I won't venture a guess, since my previous estimate missed by a country mile)   

My thoughts about which way the segments point was based only on the torque.  I didn't consider the centrifugal loads because I think they're fairly small at 250 RPM and 6 inch radius, but I haven't done the calculation.  Now that I know how much trouble I can get into doing that...

Anyway, the torque during braking is in the same direction to the torque during normal operation, just greater, briefly.  If you flip the stator over I think it will do the same thing just slide the edges the opposite way, the same amount.

As for the pins, now that you've convinced me the shear forces are small, then the size of the locking pins can be made very small indeed.  They don't have to go right through, either, and they don't have to be exceptionally precise.   A 1/8" set-screw in one of the "jaws" of a segment contacting the "tongue" of the adjacent segment would do fine.  Can be fit under the clear ring around the outer edge so they won't come out - and you can inspect it, too.

It doesn't need to be a perfect bolt hole, either.  A half-moon cut-out in one part beside a half-moon cut-out in the adjacent part makes a round hole for a little pin/screw/dog/key.  The pieces can't come apart unless they separate - your mounting bolts prevent that.  Placed under your polycarbonate ring the key doesn't fall out either.

Frank's recommendation to double up the bolts is also good.  Much more beef in that approach, compared to my delicate strategies.

[kitestrings]

Pheeew.  You had me scared there SparW.  Not that there isn't still a issue/challenge, but I'd feared I'd underestimated some structural considerations by nearly an order of magnitude.  Thanks for following up.

I think with a simple jig we might well do it all intact.  Caution, highly technical and detailed drawing to follow:


If you could picture the two outer-most holes being large enough to just clear the ¼” nuts on the existing thru-bolts; this would just locate us.  The jig would have a cut-out to go around the larger bolt & coupler-nut that attaches to the stator bracket.  Then welded, or press-fit at the second hole from the left would be a drill-guide that locates and guides us to drill the second set of  holes.  Clamp, drill, repeat 6x.  We're done.

Dowels are necessarily out, but we can't go under the poly- because it can't be removed independently.

~ks

[SparWeb]

I always factor up all my budget estimates by 2 PI, so it's no surprise I overshot the loads calculation by the same amount.

Are you going to add stator mount arms to reach the new holes?  Or perhaps weld arc segments between the existing stator mount arms to pick up the new holes & bolts?

[Frank S]

KS you mentioned that dowels are out , maybe I'm not seeing the whole picture or I'm possibly looking at a different avenue of relation.
Not having the segments in front of me I thought I would creat a 3d cad model from the pics of your previous thread .
 here is what i was thinking

 Note the location and angle of the dowels. Blind dowels are removable providing they are pre drilled on one end then a simple screw on a slide hammer will pull them out or the dowel could be what is termed a dowel stud with one end threaded  a simple screwdriver slot could be notched into the outer end.
 Placement in this manner will  will lock the T/G so that slippage cannot occur.
 your Idea of the 2nd hole using a drill jig for placement shows merit adding bolts to the segments like you explained will be a good thing.
 Good luck this is a most interesting build and  showing the things that could happen will help others who may follow this design 

[kitestrings]

Are you going to add stator mount arms to reach the new holes?  Or perhaps weld arc segments between the existing stator mount arms to pick up the new holes & bolts?

No, I don't think this will be necessary.  The bracket is pretty solid with the six connection points.  It may not be quite clear, but the coil sectors are all identical, with one bushing at the perimeter.  There are six 1/2" hex button-heads connecting to the stator bracket, and every other hole in the completed stator just has a Delrin busing reducing it from 1/2" to 1/4".  On these we just have a 1/4-20 SS thru-bolt sandwiching the stator joint between the poly-carb rings.  See below (downwind view, then upwind).



Frank, I'd meant to say that we haven't ruled dowels out, but drilling and removal are concerns.  Thanks for taking the time on the CAD, I follow your thinking on it.  I think this will work, just got to weigh it against the other options.

Very much appreciate the help with this.

~ks

[Frank S]

KS if you have concerns about adding more metal to the stator  You might consider using  Non ferrous bolts such as Fiberglas (isoplast) bolts.
  Isoplast (Fiberglass) urethane resins are high tensile strength, chemically resistant resins originally developed for medical use. They are available in long glass fiber-filled grades. Isoplast combines the toughness and dimensional stability of amorphous resins with the chemical resistance of crystalline materials. The long fibre reinforced grades are strong enough to replace some metals in load bearing applications. 40% long glass filled grade has tensile strengths up to 27,000 Psi. Max Service temperature is 150 deg F. Melting point is 336 deg F. Gray in color, but also available in Natural (Off white).

http://www.non-ferrousfastener.com/categories.php?cat=48

[kitestrings]

Frank,

Thanks for this link.  It is not usually a good sign when they say, "call for pricing", which translated either means they're expensive or you have to by a boat-load, or both.  Have you used any of the isoplast to know if they're pricey?

It might be an option for here, but it got me thinking that these would be an improvement over the nylon cap screw that we're using on the rectifiers.  There we've got our diodes mounted in aluminum blocks, and those blocks are separated electrically form the heat sinks using a Sil-pad (Kapton) separator.  The ideal mount is where we have lots of pressure.  this ensures the best thermal transfer.  In our case we torqued the nylon to its tensile rating, but are limited by the material.  The isoplast looks to have over 2x the rating.

~ks

[Mary B]

Plastic bolts http://www.mcmaster.com/#nonmetallic-bolts/=s2cv0r they have ceramic too.

[kitestrings]

Mmm, yes I've bought quite a bit of hardware thru McMaster Carr with good results.  I'm still amazed when I place an order and a package appears the next day, or two, on my steps.  It appears they are limited here to nylon or PTFE (with similar tensile ratings), or ceramic.  I'm not sure what the properties of the ceramic are, but $42 for a 1/4=20 x 1.25" hex head they're pretty pricey.

I think stainless will be fine for the stator bolts.  For mounting the diodes I thought the isoplast looked like an improvement over the nylon, but I've no idea what they cost.

[Frank S]

Here is another source for the Isoplast bots
http://www.fastenercomponents.com/isoplast-hex-head-cap-screws.php

 Still wanting you to call for quote.
 Most of the fastener houses around here have gone to a $$ minimum purchase and the useless box stores don't even know what you are talking about most of the time.
 You might try a very high end Marine supply or specialty electrical/ electronics outlets
 You can look up Isoplast on Amazon and possibly Ebay
 In the past The company I was with in Kuwait, used tons of non metallic fasteners I wasn't involved in purchasing but I believe most of ours came from either Sweden, Denmark, the Ukraine, or Possibly Germany, And some from the US. For our projects we normally bought large quantities and our PA was real sharp at  getting the best bottom line 

[Mary B]

amazon http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dindustrial&field-keywords=isoplast

[kitestrings]

This is the template that I made to locate new stator holes.  It fits snuggly over the adjacent button-head hex bolts that attach the stator to the stator bracket on the upwind side.  It has an insert for a pilot hole, then once removed, it has a 1/4" drill guide.  My plan is to dill six new holes (ever other sector), then thru-bolt with 1/4"-20 SS hex bolts, flats and locknuts.  (The washer in the picture is the correct OD, but not 1/4").  I believe it can all be done in place, or before it goes on the higher tower.




I have one other task if anyone has thoughts.  The hinge bolt for my tail - well technically it is a BAB - goes into a locknut that is welded to the underside of the lower washer/flange.  If I torque it too tight it restricts the motion, so I left it maybe a flat or two from "tight".


I've noticed, however that it has loosened a bit with the normal movement; I regularly manually furl when unattended.  I'd like to add a lock of some sort.  Options might be lock-tite, safety wiring, welding a flange/tab washer under the hex-head, or ,...maybe a roll-pin?.  Anyone got a technique they swear by?

Thanks for any input, ~kitestrings

[SparWeb]

That size of nut can be obtained with a "castle" instead of the nylon friction insert.  You would also need to drill a 1/8" hole through the end of the threaded rod to line up when the nut is in place.  Then you can put a cotter pin or a roll pin through the nut and bolt together.  Won't turn.  If it's good enough for aircraft engines and props, should be good for your windmill.

Look up Military Specs MS14144 or MS17826 
http://www.aircraft-spruce.com/catalog/hapages/MS17826.php

This supplier carries them up to 1/2" only.  They do get more difficult to find, but can be found up to 1-1/4" size. 

Of course, if you're committed to drilling a hole in that threaded rod, what's to stop you from sawing a slot across the top of that nut?

If you must rely on torque to keep it in place, then loosening it until it relies only on the nylon friction is risky.  Can you replace that threaded rod with a longer one?  Then you would have extra threads to use for tightening a jam nut against the other nut.  That's not a perfect strategy either.

Most other lock-wire strategies will be undermined by the need for the hinge to turn.

[Frank S]

Either one of these would be a good solution
 

 These can be bought cheaply at most better fastener houses. Tractor Supply Co. should have one or the other
 Having a  keyed washer directly against the Thrust bearing eliminates the torque transmittal to the nut
  filing a flat on the existing thread would be easy enough, but cutting an actual key way would be more involved

[kitestrings]

The c