Author Topic: Help with 300watts design  (Read 2041 times)

0 Members and 1 Guest are viewing this topic.

flydr2

  • Newbie
  • *
  • Posts: 6
Help with 300watts design
« on: January 27, 2007, 03:21:21 PM »
I have 24x 1"x1"x.250" grade 42 magnets and wanted to know if a 200-300 watts design is possible for these small magnets...


What size rotors?

Coil turns,wire size?


Any ideas would be very helpfull...


I recently move from Canada to the Dominican Republic and now I'm stuck with no power 16hrs/day.


I do have a 1kw inverter but usually the batteries don't have time to charge. I'm using 2x 6v batteries for a 12v system.


I calculated that if I could get power from the wind (winds are 20mph 8h/day, everyday here) at 200w I would have no problems.


I may want more power later. But at this time I want to start with a small machine.


Thanks!


Marc

« Last Edit: January 27, 2007, 03:21:21 PM by (unknown) »

Flux

  • Super Hero Member Plus
  • *******
  • Posts: 6275
Re: Help with 300watts design
« Reply #1 on: January 27, 2007, 08:44:48 AM »
11" magnet rotors.


Coils 50 turns #15, try to keep coils as thin as possible, I think you should manage with coils 5/16" and not more than 3/8" thick.


 Use 9 coils star connected for 3 phase


Prop 7 ft diameter tsr 7.


Not the best compromise for very low winds but if you have 20mph then it will be fine.


If you find it stalls then open the air gap rather than add resistance.


Furl at about 400W.


If you have wind consistently at 20 mph you should do very well.


Flux

« Last Edit: January 27, 2007, 08:44:48 AM by Flux »

flydr2

  • Newbie
  • *
  • Posts: 6
Re: Help with 300watts design
« Reply #2 on: January 28, 2007, 06:20:21 AM »
Thanks for the quick reply...


Would 2 blades be enough or should I go with 3 blades?


Does anyone have info. on a furling system where the machine tilts backwards or is it better to stick to a furling system that moves sideways?


Cheers!

Marc

« Last Edit: January 28, 2007, 06:20:21 AM by flydr2 »

Flux

  • Super Hero Member Plus
  • *******
  • Posts: 6275
Re: Help with 300watts design
« Reply #3 on: January 28, 2007, 07:07:17 AM »
Your two questions are linked.


If you have good non turbulent wind then 2 blades will do, similarly a tilt back furling may work well enough.


If the wind is likely to be turbulent, then 2 blades will be a source of vibration during yaw. Similarly the tilt back schemes perform very badly in turbulent conditions.


They nearly always need a damper and what you should damp is the yaw motion but for simplicity they usually damp the vertical motion.


Everyone has their preferences, I personally would not use a vertical furling scheme.


3 blades will definitely be smoother than 2, but at 7ft on a clean site 2 blades could be perfectly satisfactory, Beyond about 8ft 2 blades are questionable with a tail steering scheme.

Flux

« Last Edit: January 28, 2007, 07:07:17 AM by Flux »

Countryboy

  • Sr. Member
  • ****
  • Posts: 269
Re: Help with 300watts design
« Reply #4 on: January 28, 2007, 10:20:27 AM »
Hi Flux,

  Why is it better to dampen the yaw motion?  I would think dampening the vertical motion would be more important.


If the yaw is not dampened, a sudden gust from the side will rotate the mill, and it will try to unfurl and return to the normal position - until the new wind direction catches the blades and corrects to the proper level of furl.  It's rough, jerky furling which is going to be harder on a machine the bigger it is.


If the yaw is dampened, if the wind quickly changes direction, the machine can't yaw fast enough.  The machine unfurls hard and rough.  It will crash back to the normal position even more harshly than if it yawed rapidly, and the new wind direction helped buffer the unfurling movement.


Dampening the vertical motion corrects this problem, regardless if yaw is dampened or not.  It makes the furl motion smoother, and eliminates the hard, rough crash landing of the machine returning to the unfurled position.


If you have gusty winds from one direction, if you get a lapse in the wind, a dampened yaw provides no benefit.  If you have vertical dampening, it will prevent the machine from crashing back into the unfurled position if there is a lapse is the wind.


I've never yet messed with tilt back furling, but I've often thought it had benefits of simplicity over a furling tail.  I suspect you have a few more years of knowledge about mills than I - so what am I overlooking on the importance of yaw dampening?

« Last Edit: January 28, 2007, 10:20:27 AM by Countryboy »

Flux

  • Super Hero Member Plus
  • *******
  • Posts: 6275
Re: Help with 300watts design
« Reply #5 on: January 28, 2007, 11:12:22 AM »
With tilt back furling, the gyroscopic force has a vertical component when the thing yaws. If it yaws one way then it flips up and when it yaws the other way it slams back down.


If you can slow the yaw to a point where this force is negligible then most of the tendency to nodd up and down disappears. There would still be some benefit in damping the vertical axis but in normal furling operation it would be no worse than with side furling ( which could also benefit from some damping especially on the return direction)


The only one I played with worked perfectly well if the tail was tied to stop it yawing, but if left to yaw on that site it spent it's life slamming up and down.


With a side furling machine the yaw produces a force tending to bend the tower backwards or forwards and all this does is add some frictional damping to the yaw axis.


On reasonable sites it is probably fair to say that damping the vertical axis only makes something workable but much of the tilting back has more to do with the yaw component than true furling.


flux

« Last Edit: January 28, 2007, 11:12:22 AM by Flux »

Countryboy

  • Sr. Member
  • ****
  • Posts: 269
Re: Help with 300watts design
« Reply #6 on: January 28, 2007, 11:38:43 AM »
I think the most successful examples of tilt back furling would be the old Winchargers.  IMHO, if the tilt back furling had excessive problems, Wincharger would have quickly phased them out.


When looking at the old tilt back Winchargers, it's always seemed to me that they usually had undersized tails as compared to tails of side furling or windbrake mills.  Is the smaller tail a way to dampen the yawing, since the tail has less area, and would make the mill yaw slower?


Wincharger undoubtedly did a lot of research on tilt back furling.  If someone wanted to build a tilt back, I think we would be wise to see what Wincharger did, and why they did the things they did.


I find it interesting the different methods of tilt back furling Wincharger used.


Here, the pivot for the tilt back is at the rear bottom of the generator, and the generator mass is almost directly on top of the yaw bearing.  Gyroscopic forces would tend to be less by having the mass centered on the yaw bearing.  

http://www.wincharger.com/ads/Parris-Dunn-Large-2-f.jpg


Here, the pivot point for the tilt back is the center of the generator mass, rather than the end of the generator.  The generator is also offset from the yaw bearing.  It should also be noted the tail appears much larger on this model.

http://www.wincharger.com/ads/Dunn-Governingf.jpg

« Last Edit: January 28, 2007, 11:38:43 AM by Countryboy »

Flux

  • Super Hero Member Plus
  • *******
  • Posts: 6275
Re: Help with 300watts design
« Reply #7 on: January 28, 2007, 11:55:09 AM »
I think you mean the Paris -Dunn, Wincharger used a an expanding paddle brake.


For small machines you can get away with very basic things. You are right that keeping the tail small is a step in the right direction. I also made the mistake of using ball bearings for the yaw, extra friction there would have helped.


Swwp went away from vertical furling and the Wind Baron was a disaster. There seem to have been better survival results with down wind machines.


As I said previously everyone to his own choice, most things can be made to work but I don't see it as an easier way except for down wind versions.


Flux

« Last Edit: January 28, 2007, 11:55:09 AM by Flux »

Ungrounded Lightning Rod

  • SuperHero Member
  • ******
  • Posts: 2866
Re: Help with 300watts design
« Reply #8 on: January 28, 2007, 12:46:33 PM »
As was pointed out, 2 blades has an issue with vibration during yaw.


The blades have large intertia fighting yaw when horizontal, virtually none when vertical, so the resistance to the yaw force varies with the blade position.  Since there will be wind when there is yaw the blades will be spinning, and the yawing action will be jerkey and put stresses on much of the mill and its supports.


Any higher number of symmetrically-positioned blades doesn't have this problem - or doesn't have it to any significant degree.


An even number of blades also has another disadvantage over an odd number:  The wind is decellerated by friction with the ground, so it's faster as you go higher.  So drag force is greatest when the blade is straight up, least when straight down.  With an even number of blades one is straight up and its opposite straight down for part of the cycle, and a gap between is straight up and another straight down for another part.  So this produces a tilt-back torque that varies with the blade position - creating a vibration at N times the rotation rate for an N-even blade prop.  With an odd number of blades each blade is opposed by a gap, rather than another blade, and most of this cancels out.


This tilt-back vibration from drag variation is largest for a two-blade and drops drastically as the number of blades increases (because the additional blades coming out of horizontal are gaining force differentials as the ones coming out of vertical are losing them).  By the time you're up to six blades you're more balanced than a three-blader despite being even-numberd:  A six is two threes mounted so some of any remaining vibration components cancel.  Even a four isn't all that bad.  (A four-blader would be perfectly balanced for this due to the sine/cosine cancelation, as it is for yaw vibration, if the wind drag varied linearly with height.  Unfortunately it doesn't.)


So to avoid vibration issues you want either an odd number of blades or a large number.


From a power collection standpoint the number of blades doesn't matter much:  A lift-type blade which is spinning draws power from air for a significant distance upwind and downwind (mainly from downwind) and the wider the farther.  By matching the blade width to the tip speed ratio you end up with the next blade coming by just as most of the air decellerated by the previous blade has left the region from which this blade draws power.  By delibeartely erring on the side of using some slower air (making the blades "too wide" so they work deeper in the windstream) rather than letting some fast air get away, your blade won't let much escape even if it is running somewhat under its ideal speed.  (The energy lost to the current blade from the slowed part of the air it's working in is energy that was collected by the previous blade.)


But when you're fabricating blades, it's more work to make and mount more blades - even if they can be narrower.  Thus mill builders tend to gravitate to three-blade mills on large projects: the minimum number for low vibration.


With small units the component strength tends to be great in proportion to load, making yaw vibration acceptable, and the short blades mean little vertical drag variation if it's mounted high enough for drag to be a major issue.  Also it's easy to fabricate two blades from a single piece of wood (avoiding the joint, simplifying the hub, and gaining additional strength where it's needed) and a straight blade simplifies storage and transport.  So you'll see some small two bladers - especially for portable applications like Wolf's truck camper.


I've occasionally thought of doing a middle-sized four blader from two continuous pieces of wood, to try to get that hub strength advangage.  But you'd have to cut away half the wood for the crossover - right where you need strength the most - or end up with the two blade-pairs in different planes - perhaps requiring a tweak to their profiles for efficiency.  (If you do four blades separately you lose the hub strength and simplicity advantage, so why not just do three?)

« Last Edit: January 28, 2007, 12:46:33 PM by Ungrounded Lightning Rod »

snuffy

  • Jr. Member
  • **
  • Posts: 58
Re: Help with 300watts design
« Reply #9 on: January 30, 2007, 08:15:07 PM »
ULR


I enjoyed your blade presentation.


Here is my 4 bladed 9'9" (3 meter) using the method you described.  These are laminations, that are 8.5 inches wide at the root and 5" wide at the tip.  The two blades are epoxied together at the hub.  I think they will be quite strong.  However I haven't flown it yet.  Scheduled for erection this spring.


Snufy




« Last Edit: January 30, 2007, 08:15:07 PM by snuffy »

flydr2

  • Newbie
  • *
  • Posts: 6
Re: Help with 300watts design
« Reply #10 on: August 15, 2009, 07:25:50 AM »
Hi all, I finally (Years later) got my machine flying...


I may be having a power issue...


1st I went to 24v not 12v so I made the coils 105 turns (about 5/16" think)

    the stator ended up being a bit over 3/8" think (I had made a previous one which was too think (1/2"))


I seem to be getting 2-4 amps in 20mph wind and 2 days ago we had 40-50mph which got the thing to 15amps.


everything was built as per directions from Flux except for the coil turns. Using 7' dia magnets4less blades.


I suspect that my coils are to big/thick.


Being 24v what is the smallest size wire/turns I could be using to make the coils smaller.


Thanks

« Last Edit: August 15, 2009, 07:25:50 AM by flydr2 »

ghurd

  • Super Hero Member Plus
  • *******
  • Posts: 8059
Re: Help with 300watts design
« Reply #11 on: August 15, 2009, 11:54:49 AM »
It sounds like you are stalled.

The high winds broke it free from stall.

Try opening the air gap, just a little bit.

G-
« Last Edit: August 15, 2009, 11:54:49 AM by ghurd »
www.ghurd.info<<<-----Information on my Controller

flydr2

  • Newbie
  • *
  • Posts: 6
Re: Help with 300watts design
« Reply #12 on: August 15, 2009, 01:03:01 PM »
Did that but it's only worst. I think I'm not loading the prop enough.
« Last Edit: August 15, 2009, 01:03:01 PM by flydr2 »

flydr2

  • Newbie
  • *
  • Posts: 6
Re: Help with 300watts design
« Reply #13 on: August 15, 2009, 03:29:46 PM »
update: I just made an 85 turns #20 wire stator 3/16" thick. Will wait till tomorrow to de-mold it and post the results.


so far in 20 mph wind:


 1st stator 1/2" thick 103 turns #15 gave me 1-2 amps @24v dc (peek @ 7amps 50mph)(air gap was about 9/16)


 2nd stator 5/16" thick 105 turns #15 gave me 2-5 amps (peek @ 15 amps 50mph)(1/2" air gap)


 3rd stator TBA


My next project is a 10' to 12' machine, I have 2"x1"x1/2" magnets and 1/4" thick wedged magnets... Which ones should I use???

« Last Edit: August 15, 2009, 03:29:46 PM by flydr2 »

flydr2

  • Newbie
  • *
  • Posts: 6
Re: Help with 300watts design
« Reply #14 on: August 18, 2009, 06:05:31 AM »
3rd stator 85 turns #20 wire is slightly better than the 2nd. 5-6amps @24v 20mph wind.


I've taken the mill down again and will build a bigger 10' one.


Getting only 100-150 watts is not quite enough for what I need.

« Last Edit: August 18, 2009, 06:05:31 AM by flydr2 »