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Re: Update to "Ok if you were to" and the newest idea...

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  • Harold
    I thought this design let the front blades spin one direction (turning the rotor) and the back set of blades spin the opposite direction (turning the stator)..
    Message 1 of 15 , Mar 1, 2008
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      I thought this design let the front blades spin one direction
      (turning the rotor) and the back set of blades spin the opposite
      direction (turning the stator).. I thought this effectively gave you
      a little less than twice the rpm difference between the rotor and
      stator.

      Please correct me if I am wrong.

      Thanx
      Harold
      vwbiofuels.com

      --- In axialflux@yahoogroups.com, "Dan" <qazxcvb21@...> wrote:
      >
      > --- In axialflux@yahoogroups.com, "dem45133" <dmikkelson1942@>
      > wrote:
      > >
      > > Thanks Dan.. I'm looking into that too. If the multiple rotors
      are
      > on
      > > the same shaft (off-set a bit to the wind's direction to allow
      some
      > > clean air to each rotor) I'd still have trouble getting enough
      rpm
      > for
      > > direct axial at the 4.5 m/s supposed average I have wouldn't
      I?. I'd
      > > gain some torque... but not the rpms needed right?.
      >
      > First off you NEED to look at Doug Selsam's design to understand
      the
      > concept. The blades are about 5 feet in front of the alternator
      and
      > about the same didtance behind it, so when it is offset about 20
      > degrees they are in clean air.
      > Secondly flying in an offset attitude doesn't affect the
      gathering of
      > energy as much as you would think.
      > There is a very good discussion over on the AWEA group going on
      right
      > now ( http://tech.groups.yahoo.com/group/awea-wind-home/ )about
      blades
      > and their design. Larger blades are heavier and slower whereas
      smaler
      > blades are lighter and turn faster... And all that stuff!
      > Third, more torque means the blade will start sooner and turn
      faster
      > at a given wind speed.
      >
      > SO!!! You build\buy smaller thinner blades and put them on the
      ends of
      > a long pole with your alternator in the middle and fly them
      slightly
      > tilted and instead of harvesting energy in a circle you harvest it
      in
      > an oval.
      >
      > Does that help?
      >
    • dem45133
      No... Doug s is a little different dual rotor set up. For conventional contra rotating rotors you are right... but the downstream rotor only has about 1/3 the
      Message 2 of 15 , Mar 2, 2008
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        No... Doug's is a little different dual rotor set up. For
        conventional contra rotating rotors you are right... but the
        downstream rotor only has about 1/3 the available energy the front one
        had. So the concept it not as efficient in the lower wind regimes as
        higher.

        Doug's runs a pair of distanced rotors on a common shaft offset about
        20 degrees to the wind direction... both rotors run in clean air but
        at a slight angle... which evidently is still more efficient at
        gathering power than a single large for the same total rotor area...
        as it maintains the shaft speed higher. But I'd still have the 40%
        never generating problem with my distribution and where the
        conventional get usable E active... about 4.5 m/s... just under my norm.

        Since my wind averages so slow... I'm in a different regime than most.
        Most wouldn't bother, but I haven't given up yet. I've always been
        an out-of-the-box thinker... and since I'll build the unit myself, the
        money/payback time paradigm is different too.


        --- In axialflux@yahoogroups.com, "Harold" <harold@...> wrote:
        >
        > I thought this design let the front blades spin one direction
        > (turning the rotor) and the back set of blades spin the opposite
        > direction (turning the stator).. I thought this effectively gave you
        > a little less than twice the rpm difference between the rotor and
        > stator.
        >
        > Please correct me if I am wrong.
        >
        > Thanx
        > Harold
        > vwbiofuels.com
        >
        >
      • ferrand
        Harold, The arrangement you describe [contra rotation] was first put forward by Honnef in Germany, in Windkraftwerke published in 1932, researched by the 3rd
        Message 3 of 15 , Mar 3, 2008
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          Harold,
          The arrangement you describe [contra rotation] was first put forward by Honnef in Germany, in "Windkraftwerke" published in 1932, researched by the 3rd Reich Wind Energy Ministry 1935-45, and implemented in the Trimblemill 1978-82. One of the latter has been operational in Scotland for the past 17 years or so. I was the person who helped develop the Trimblemill and have all technical data available, A re-engineering of the concept is now proposed, using axial flux. The revised "geometry" has been settled, and calculations are in progresss to establish the "maximum economic diameter", the size/rating at which the cost/kg/kW starts to rise again after falling as the rotor diameter and rating increases. Following Dog Selsam's comment elsewhere given below***

          Not only does contra rotation give you the speed increase there is an increase in energy collection per unit of rotor area, and some predicted useful electrical characteristics for multirotor units. The Solar [circular] Dish industry use a "multiunit" approach, usual max rating per unit is 25 kW.
          regards
          Ferrand


          Re: Update to "Ok if you were to" and the newest idea...
          Posted by: "Harold" harold@... vwbiofuels
          Date: Sun Mar 2, 2008 10:38 am ((PST))

          I thought this design let the front blades spin one direction
          (turning the rotor) and the back set of blades spin the opposite
          direction (turning the stator).. I thought this effectively gave you
          a little less than twice the rpm difference between the rotor and
          stator.

          Please correct me if I am wrong.

          Thanx
          Harold
          vwbiofuels.com

          *** comment from Doug Selsam:-
          Thanks for making my point: Yes the old way to sweep more area is
          to increase diameter. The problem is that doubling diameter
          quadruples swept area, but also drops RPM in half. Since power is
          proportional to RPM squared, you need 4 times as much generator for
          the increased swept area, and 4 times again for the lowered RPM,
          requiring 16x the generator size to to handle that 4x power. The
          advantage of using extra rotors is increasing swept area without
          lowering RPM. Blade weight is also a cubic function of diameter,
          while swept area is only a square function, meaning that larger
          blades sweep less area per unit blade mass. Less efficient use of
          blade material. I know you can understand this if you try. You are
          a smart guy. Making rotors larger is like spending on your credit
          card - a quick fix that will come back to bite you when the real
          numbers are realized.
        • jerry freedomev
          Hi Ferrand and All, ... While counter rotating windgens are more eff if designed right, they are always more expensive and require more maintainance per unit
          Message 4 of 15 , Mar 4, 2008
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            Hi Ferrand and All,

            --- ferrand <ferrand@...> wrote:

            > Harold,
            > The arrangement you describe [contra rotation] was
            > first put forward by Honnef in Germany, in
            > "Windkraftwerke" published in 1932, researched by
            > the 3rd Reich Wind Energy Ministry 1935-45, and
            > implemented in the Trimblemill 1978-82. One of the
            > latter has been operational in Scotland for the past
            > 17 years or so. I was the person who helped develop
            > the Trimblemill and have all technical data
            > available, A re-engineering of the concept is now
            > proposed, using axial flux. The revised "geometry"
            > has been settled, and calculations are in progresss
            > to establish the "maximum economic diameter", the
            > size/rating at which the cost/kg/kW starts to rise
            > again after falling as the rotor diameter and rating
            > increases. Following Dog Selsam's comment elsewhere
            > given below***

            While counter rotating windgens are more eff
            if designed right, they are always more expensive and
            require more maintainance per unit of output, which
            are deal killers as by increasing dia 10-15% puts out
            the same power at much less manufacturing,
            installation, lifetime costs. I was in on a working
            counter rotating windgen in the 70's. But I stopped as
            it just was not worth it.


            >
            > Not only does contra rotation give you the speed
            > increase there is an increase in energy collection
            > per unit of rotor area, and some predicted useful
            > electrical characteristics for multirotor units. The
            > Solar [circular] Dish industry use a "multiunit"
            > approach, usual max rating per unit is 25 kW.

            But modern tech allows lower speeds for less
            money so again multirotor points are a non starter.
            I was talking to Doug on the AWEA list while
            he was designing his and it has worse problems. His
            blades don't counter rotate and much of them are in
            the shadow of the forward blades, cutting their eff or
            at such angles to cut eff. Again his claim of higher
            rotor speed advantage is not a problem with axial flux
            alts now available and especially that anyone almost
            can build their own alts. Doug has to argue because
            otherwise he loses money. Just his arguments are
            either wrong, stretched or not relivent.
            For the money, mantainance and by any other
            measure that counts, a standard 3 blade unit will
            produce more power for less money than any other type.
            Feel free to use them yourself, but in good
            conscience, don't recommend them to others as better
            as that is just not true.
            I agree with Dan the second set of more
            counter rotating blades are for vibration but also for
            power reasons as they have to work in swirling , lower
            air energy from the first rotor. If your well design 3
            forward blades are working well, you have much less,
            57% less windspeed, thus power, available for them.
            It's just plain physics.


            Jerry Dycus

            > regards> Ferrand
            >
            >
            > Re: Update to "Ok if you were to" and the newest
            > idea...
            > Posted by: "Harold" harold@...
            >
            >
            > *** comment from Doug Selsam:-
            > Thanks for making my point: Yes the old way to
            > sweep more area is
            > to increase diameter. The problem is that doubling
            > diameter
            > quadruples swept area, but also drops RPM in half.
            > Since power is
            > proportional to RPM squared, you need 4 times as
            > much generator for
            > the increased swept area, and 4 times again for the
            > lowered RPM,
            > requiring 16x the generator size to to handle that
            > 4x power. The
            > advantage of using extra rotors is increasing swept
            > area without
            > lowering RPM. Blade weight is also a cubic function
            > of diameter,
            > while swept area is only a square function, meaning
            > that larger
            > blades sweep less area per unit blade mass. Less
            > efficient use of
            > blade material. I know you can understand this if
            > you try. You are
            > a smart guy. Making rotors larger is like spending
            > on your credit
            > card - a quick fix that will come back to bite you
            > when the real
            > numbers are realized.
            >
            >


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          • jerry freedomev
            Hi All, A couple months ago I saw an article in the Tampa Tribune on a guy building windgens. I though probably another off the wall nut but since it mentioned
            Message 5 of 15 , Mar 5, 2008
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              Hi All,
              A couple months ago I saw an article in the
              Tampa Tribune on a guy building windgens. I though
              probably another off the wall nut but since it
              mentioned Hugh Piggott's type of unit I figured I'd
              check it out as I've alway been interested in them and
              wanted to see one, an axial flux alt in person.
              It turned out to be a smart move as I found
              an excellent craftsman, person, building a well done
              version of Hugh's design in the 10' class. It's very
              heavy duty and will last a long time the way it's
              made, 30-50 yrs with yearly normal mantainance and at
              a reasonable price, $1200.
              Here's his website with info.

              http://www.floridawindgenerators.com/

              If you are interested in this type of
              windgen, it's a good choice if you want to buy instead
              of building your own. Tell him I sent you and you'll
              get $25 off. And he sells parts for those who want
              them.

              Jerry Dycus





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            • Dan Bartmann
              I looked at that site, it s interesting. It s quite similar I suppose to what we are all doing. We sell similar machines/kits here:
              Message 6 of 15 , Mar 9, 2008
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                I looked at that site, it's interesting. It's quite similar I suppose
                to what we are all doing. We sell similar machines/kits here:
                http://www.forcefieldmagnets.com/catalog/index.php?cPath=22_30

                Things I do not like about what I see at Florida Wind Generators....
                1000 - 1200 Watt Rating, it looks to me like the magnets used are too
                small and therefor the stator resistance too high to withstand that
                sort of output. We use the same magnets in some machines but in bench
                tests (and real life) we see burnouts with sustained output much over
                600 - 700W, such machines should furl early and they still have very
                little safety factor.

                Hopefully the magnets are pinned to the rotors, I've had trouble with
                'glued' or 'cast' magnets flying out (hitting blades etc...).

                I've had pretty bad luck in the past with sheet metal tails and metal
                fatigue, every time I try it they fall off over time.

                30 - 50 year life span seems quite optimistic, it's good for marketing
                to say such stuff but 'only time will tell'. It takes a lot of
                machines in the field and lots of time to really know where problems
                will arise. Fortunely he's starting with a fairly well proven design
                though.




                --- In axialflux@yahoogroups.com, jerry freedomev <freedomev@...> wrote:
                >
                >
                >
                > Hi All,
                > A couple months ago I saw an article in the
                > Tampa Tribune on a guy building windgens. I though
                > probably another off the wall nut but since it
                > mentioned Hugh Piggott's type of unit I figured I'd
                > check it out as I've alway been interested in them and
                > wanted to see one, an axial flux alt in person.
                > It turned out to be a smart move as I found
                > an excellent craftsman, person, building a well done
                > version of Hugh's design in the 10' class. It's very
                > heavy duty and will last a long time the way it's
                > made, 30-50 yrs with yearly normal mantainance and at
                > a reasonable price, $1200.
                > Here's his website with info.
                >
                > http://www.floridawindgenerators.com/
                >
                > If you are interested in this type of
                > windgen, it's a good choice if you want to buy instead
                > of building your own. Tell him I sent you and you'll
                > get $25 off. And he sells parts for those who want
                > them.
                >
                > Jerry Dycus
                >
                >
                >
                >
                >
                >
                ____________________________________________________________________________________
                > Never miss a thing. Make Yahoo your home page.
                > http://www.yahoo.com/r/hs
                >
              • jerry freedomev
                Hi Dan and All, ... http://www.forcefieldmagnets.com/catalog/index.php?cPath=22_30 Been a while since I seen the Forcefield website. It s been well improved,
                Message 7 of 15 , Mar 10, 2008
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                  Hi Dan and All,

                  --- Dan Bartmann <danb@...> wrote:

                  > I looked at that site, it's interesting. It's quite
                  > similar I suppose
                  > to what we are all doing. We sell similar
                  > machines/kits here:
                  >
                  http://www.forcefieldmagnets.com/catalog/index.php?cPath=22_30

                  Been a while since I seen the Forcefield
                  website. It's been well improved, more products.

                  >
                  > Things I do not like about what I see at Florida
                  > Wind Generators....
                  > 1000 - 1200 Watt Rating, it looks to me like the
                  > magnets used are too
                  > small and therefor the stator resistance too high to
                  > withstand that
                  > sort of output.

                  Could you explain why? He has produced much
                  more than 1200 watts, especially at 24vdc nom. I
                  assume it's amp limited, not watt/power/voltage
                  limited?


                  We use the same magnets in some
                  > machines but in bench
                  > tests (and real life) we see burnouts with sustained
                  > output much over
                  > 600 - 700W, such machines should furl early and they
                  > still have very
                  > little safety factor.

                  I've also had concerns on heat on your
                  stator/coil design. As a composites and Etech person
                  in real life, polyester, epoxy resin is not a good
                  conductor of heat and being solid resin makes it even
                  worse. I'd use FG faces and epoxy dripped over the
                  coils to solidify them, leaving cooling channels
                  between the coils so air can cool them, increasing
                  their power out by 100%+. I'm planning on using a
                  similar design with steel laminations as an EV motor
                  at much higher power levels.
                  And polyester shrinks as it ages so many done
                  with it may crack as they age. At least mix some FG
                  matt fibers in them to help stop future cracking.
                  But it's a case of almost no cooling that
                  limits it's output it seems. By cooling better, one
                  could get much more out of the same materials.


                  >
                  > Hopefully the magnets are pinned to the rotors, I've
                  > had trouble with
                  > 'glued' or 'cast' magnets flying out (hitting blades
                  > etc...).

                  Yes they are.

                  >
                  > I've had pretty bad luck in the past with sheet
                  > metal tails and metal
                  > fatigue, every time I try it they fall off over
                  > time.

                  I'm not fond of any tails as they don't work
                  well, rather use a downwind rotor which tracks much
                  better I've found in the 20 windgens I've built for
                  powering cruising sailboats. He's working on a better
                  one.


                  >
                  > 30 - 50 year life span seems quite optimistic, it's
                  > good for marketing
                  > to say such stuff but 'only time will tell'.

                  I'm versed in such problems and his
                  materials, workmanship are excellent so have no
                  problem saying they will last that long with normal
                  maintance.
                  The only doubtful parts lasting that long are
                  wooden blades and the resin used to cast the stator,
                  both of which will have to be replaced, blades after 5
                  yrs or so and stator about the same time I'd guess.
                  For the blades a vinyl film like used to
                  repair car seats from most car parts stores along the
                  leading edge can help that damage a lot.
                  I'd build figerglass blades of my design
                  instead as they are lighter, better aero, much longer
                  lasting.
                  Building the stator in a good high temp
                  epoxy with a track record like Mil spec and adding
                  cooling which we are working on should both increase
                  power out and increase life.


                  It
                  > takes a lot of
                  > machines in the field and lots of time to really
                  > know where problems
                  > will arise. Fortunely he's starting with a fairly
                  > well proven design
                  > though.

                  Yes it is a good, hardy design and as an old
                  windgen designer, builder, a good starting point for
                  an economical RE power source for the masses.
                  He does sell finished ones at a good price and
                  backs them up as he's a good, ethical person.
                  I'll use them as an example in the Fla Leg
                  which is now in session and approving RE tax credits,
                  Net metering, R+D grants, so anyone in Fla should
                  contact me, Dan at Flawindgen link below or their leg
                  rep. Comments mean a lot and on net metering in the
                  Fla PSC, they got only 2!!
                  I was going to build windgens to make some
                  cash but lots of competition out there now it seems so
                  going to build aero cabin EV MC's as useable,
                  practical art instead as no competition there, better
                  prices, profits!!

                  Jerry Dycus






                  >
                  >
                  >
                  >
                  > --- In axialflux@yahoogroups.com, jerry freedomev
                  > <freedomev@...> wrote:
                  > >
                  > >
                  > >
                  > > Hi All,
                  > > A couple months ago I saw an article in
                  > the
                  > > Tampa Tribune on a guy building windgens. I though
                  > > probably another off the wall nut but since it
                  > > mentioned Hugh Piggott's type of unit I figured
                  > I'd
                  > > check it out as I've alway been interested in them
                  > and
                  > > wanted to see one, an axial flux alt in person.
                  > > It turned out to be a smart move as I
                  > found
                  > > an excellent craftsman, person, building a well
                  > done
                  > > version of Hugh's design in the 10' class. It's
                  > very
                  > > heavy duty and will last a long time the way it's
                  > > made, 30-50 yrs with yearly normal mantainance and
                  > at
                  > > a reasonable price, $1200.
                  > > Here's his website with info.
                  > >
                  > > http://www.floridawindgenerators.com/
                  > >
                  > > If you are interested in this type of
                  > > windgen, it's a good choice if you want to buy
                  > instead
                  > > of building your own. Tell him I sent you and
                  > you'll
                  > > get $25 off. And he sells parts for those who
                  > want
                  > > them.
                  > >
                  > > Jerry Dycus
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  >


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                • Dan Bartmann
                  Hi Jerry - ... We are doing more and more with wind power all the time. ... Yes, I have no doubt one would see over 1200W at times from such alternator, but I
                  Message 8 of 15 , Mar 10, 2008
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                    Hi Jerry -

                    > Been a while since I seen the Forcefield
                    > website. It's been well improved, more products.

                    We are doing more and more with wind power all the time.

                    > > Things I do not like about what I see at Florida
                    > > Wind Generators....
                    > > 1000 - 1200 Watt Rating, it looks to me like the
                    > > magnets used are too
                    > > small and therefor the stator resistance too high to
                    > > withstand that
                    > > sort of output.
                    >
                    > Could you explain why? He has produced much
                    > more than 1200 watts, especially at 24vdc nom. I
                    > assume it's amp limited, not watt/power/voltage
                    > limited?

                    Yes, I have no doubt one would see over 1200W at times from such
                    alternator, but I cannot imagine the alternator is much better than
                    50% efficient at 600 - 700W output (because I have built many of the
                    same thing and bench tested them). That sort of stator, that size,
                    cannot dissipate much more tha 600W sustained without overheating.
                    (and yes, it is current limited - so at 24V about 25-30 amps would be
                    the limit assuming its wound similarly to one's I've built - which I
                    believe it is because yesterday I figured out who this is on our
                    discussion board and I've been following his progress)
                    >
                    >
                    > We use the same magnets in some
                    > > machines but in bench
                    > > tests (and real life) we see burnouts with sustained
                    > > output much over
                    > > 600 - 700W, such machines should furl early and they
                    > > still have very
                    > > little safety factor.
                    >
                    > I've also had concerns on heat on your
                    > stator/coil design. As a composites and Etech person
                    > in real life, polyester, epoxy resin is not a good
                    > conductor of heat and being solid resin makes it even
                    > worse.

                    Exactly - which is why I prefer to use larger magnets, and a stator
                    with much lower resistance.

                    I'd use FG faces and epoxy dripped over the
                    > coils to solidify them, leaving cooling channels
                    > between the coils so air can cool them, increasing
                    > their power out by 100%+.

                    I doubt you'd see that much improvement but can't say for sure. It's
                    really quite simple to just build a more robust alternator at slightly
                    increased cost in magnetic material. If it stalls the blades (which
                    is often the case) it's a simple matter to add resistance to the
                    line/get the blades out of stall.


                    > And polyester shrinks as it ages so many done
                    > with it may crack as they age. At least mix some FG
                    > matt fibers in them to help stop future cracking.

                    Yes, polyester is not my favorite resin. I've not had problems with
                    stators cracking and polyester seems to work OK, but I do prefer Vinyl
                    Ester these days. It withstands much higher temps, shrinks less - and
                    costs slightly more. While I don't normally use chopped fiberglass in
                    stators (except in much larger machines) I do use it in magnet rotors.

                    > But it's a case of almost no cooling that
                    > limits it's output it seems.

                    Well... the stator of that size will disipate about 600 W before it
                    burns out - and - with those magnets that's about 50% efficiency. You
                    could improve cooling... but it gets a bit sad to be running much
                    below 50% efficiency anyhow. So rather than trying to cool an
                    alternator thats borderline too small to begin with/get more power, I
                    think the simple solution is to build a more powerful alternator with
                    lower resistance.

                    By cooling better, one
                    > could get much more out of the same materials.

                    Perhaps a bit - but with I^2 R losses a small improvement in cooling
                    wont get you much safety factor. Cutting resistance in half though -
                    by using larger magnets, thicker wire and less distance of wire per
                    coil goes a long ways.
                    >
                    >
                    > >
                    > > Hopefully the magnets are pinned to the rotors, I've
                    > > had trouble with
                    > > 'glued' or 'cast' magnets flying out (hitting blades
                    > > etc...).
                    >
                    > Yes they are.

                    That's good... I've often thought of going that route but I usually
                    heat shrink a stainless steel band around the rotors instead. Not
                    much advantage to that... it looks nice though ;-)

                    >
                    > I'm not fond of any tails as they don't work
                    > well, rather use a downwind rotor which tracks much
                    > better I've found in the 20 windgens I've built for
                    > powering cruising sailboats. He's working on a better
                    > one.

                    There are pros and cons to both. Upwind machines with tails tend to
                    track a bit more nicely I think, the furling system is simple/reliable
                    and to my eye... wind turbines with tails look nicer. Its a matter of
                    opinion -both ways can work out well. I can imagine on a sail boat
                    you might want to keep things more compact.
                    >
                    >
                    > >
                    > > 30 - 50 year life span seems quite optimistic, it's
                    > > good for marketing
                    > > to say such stuff but 'only time will tell'.
                    >
                    > I'm versed in such problems and his
                    > materials, workmanship are excellent so have no
                    > problem saying they will last that long with normal
                    > maintance.
                    > The only doubtful parts lasting that long are
                    > wooden blades and the resin used to cast the stator,
                    > both of which will have to be replaced, blades after 5
                    > yrs or so and stator about the same time I'd guess.

                    Yes, I suppose. And depending on climate/maintenance - wooden blades
                    can last well over 50 years. I think wood wins over anything else
                    when it comes to fatigue.

                    > For the blades a vinyl film like used to
                    > repair car seats from most car parts stores along the
                    > leading edge can help that damage a lot.

                    Yes, or epoxy... or copper flashing stapled on there! (I kind of like
                    that, it worked well on the old jacobs and winchargers)

                    > I'd build figerglass blades of my design
                    > instead as they are lighter, better aero, much longer
                    > lasting.

                    I doubt that...
                    Fiberglass blades are not necessarily light weight, I have never seen
                    a set that weighed less than wooden blades we make. fiberglass is
                    also prone to fatigue over time. I think manufacturers go to
                    fiberglass because it's cheaper and more consistant when you're
                    building lots of machines. I'm not sure what you mean by 'better
                    aero' - perhaps you're suggesting they're more efficient. That
                    doesn't need to be the case though...


                    > Building the stator in a good high temp
                    > epoxy with a track record like Mil spec and adding
                    > cooling which we are working on should both increase
                    > power out and increase life.

                    Yes, I agree. Polyester is not the best choice of materials. I use
                    Vinyl Ester with a good bit of alumina trihydrate as filler (which
                    helps some with heat conductivity).
                    >
                    >
                    > It
                    > > takes a lot of
                    > > machines in the field and lots of time to really
                    > > know where problems
                    > > will arise. Fortunely he's starting with a fairly
                    > > well proven design
                    > > though.
                    >
                    > Yes it is a good, hardy design and as an old
                    > windgen designer, builder, a good starting point for
                    > an economical RE power source for the masses.
                    > He does sell finished ones at a good price and
                    > backs them up as he's a good, ethical person.

                    Yes, I know he is because now I remember who he is on our discussion
                    forum (fieldlines.com). In my last reply I failed to realize that.
                  • jerry freedomev
                    Hi Dan and All, Thanks for Forcefield as they have lead the way in this field. I ll be a customer soon as I learn just what parts I need for several alts,
                    Message 9 of 15 , Mar 10, 2008
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                      Hi Dan and All,

                      Thanks for Forcefield as they have lead
                      the way in this field. I'll be a customer soon as I
                      learn just what parts I need for several alts, motors
                      I'll be building.

                      built- which I
                      > believe it is because yesterday I figured out who
                      > this is on our
                      > discussion board and I've been following his
                      > progress)

                      Not sure his web but in person Dan is a great
                      guy and craftsman. Not many I can say that about.



                      > > I've also had concerns on heat on your
                      > > stator/coil design. As a composites and Etech
                      > person
                      > > in real life, polyester, epoxy resin is not a good
                      > > conductor of heat and being solid resin makes it
                      > even
                      > > worse.
                      >
                      > Exactly - which is why I prefer to use larger
                      > magnets, and a stator
                      > with much lower resistance.
                      >
                      > I'd use FG faces and epoxy dripped over the
                      > > coils to solidify them, leaving cooling channels
                      > > between the coils so air can cool them, increasing
                      > > their power out by 100%+.
                      >
                      > I doubt you'd see that much improvement but can't
                      > say for sure. It's
                      > really quite simple to just build a more robust
                      > alternator at slightly
                      > increased cost in magnetic material. If it stalls
                      > the blades (which
                      > is often the case) it's a simple matter to add
                      > resistance to the
                      > line/get the blades out of stall.
                      > >
                      > > But it's a case of almost no cooling that
                      > > limits it's output it seems.
                      >
                      > Well... the stator of that size will disipate about
                      > 600 W before it
                      > burns out - and - with those magnets that's about
                      > 50% efficiency. You
                      > could improve cooling... but it gets a bit sad to be
                      > running much
                      > below 50% efficiency anyhow.

                      I'm just learning motors, alts and trying to
                      figure them out. I do understand reluctance,
                      inductance, resistance, ect.
                      I'm a little surprised at such low eff. Is it
                      because you need more turns, thus resistance in the
                      coils for low rpm? no lams??
                      If so, how would bigger magnets help?
                      Overcome the high reluctance of the air gap? It would
                      seem that would just cut output? Not more heat.


                      So rather than trying
                      > to cool an
                      > alternator thats borderline too small to begin
                      > with/get more power, I
                      > think the simple solution is to build a more
                      > powerful alternator with
                      > lower resistance.
                      >
                      > By cooling better, one
                      > > could get much more out of the same materials.
                      >
                      > Perhaps a bit - but with I^2 R losses a small
                      > improvement in cooling
                      > wont get you much safety factor.

                      We get several times more continous power out
                      of motors we improve cooling on in EV's. It's really
                      the most important factor in how much power you can
                      get from a given motor. For instance we get 200hp from
                      a 20 hp series motor peak and 40 hp cont with better
                      cooling and blueprinting for lack of a better word.
                      One guy gets that much from a 12hp motor and
                      does 8.1sec in the 1/4 mile in the EV drag bike
                      Killicycle. I'm using one of those motors in my EV.
                      But eventually want to build an axial motor for it.


                      Cutting resistance
                      > in half though -
                      > by using larger magnets, thicker wire and less
                      > distance of wire per
                      > coil goes a long ways.

                      So which magnets are you talking about?
                      With the larger magnets you get more V/turn?
                      thus less turns needs, less wire resistance, more
                      eff??
                      Lams would give you even more V/t?

                      > >
                      >
                      > That's good... I've often thought of going that
                      > route but I usually
                      > heat shrink a stainless steel band around the rotors
                      > instead. Not
                      > much advantage to that... it looks nice though ;-)

                      Works and looks sells. I'd use a composite
                      band myself and/or a lip, bolt, ect.

                      >
                      > >
                      > > I'm not fond of any tails as they don't
                      > work
                      > > well, rather use a downwind rotor which tracks
                      > much
                      > > better I've found in the 20 windgens I've built
                      > for
                      > > powering cruising sailboats. He's working on a
                      > better
                      > > one.
                      >
                      > There are pros and cons to both. Upwind machines
                      > with tails tend to
                      > track a bit more nicely I think, the furling system
                      > is simple/reliable
                      > and to my eye... wind turbines with tails look
                      > nicer. Its a matter of
                      > opinion -both ways can work out well. I can imagine
                      > on a sail boat
                      > you might want to keep things more compact.

                      It did help as they were usually taken down for
                      sailing or when leaving the boat for a while. 2 blades
                      instead of 3 helped a lot especially as low rpm gens
                      were very rare then. But the same gens, blades on
                      upwind and downwind units on boats next to each other,
                      the downwind tracked better, put out slightly more
                      power.

                      >
                      > > The only doubtful parts lasting that long
                      > are
                      > > wooden blades and the resin used to cast the
                      > stator,
                      > > both of which will have to be replaced, blades
                      > after 5
                      > > yrs or so and stator about the same time I'd
                      > guess.
                      >
                      > Yes, I suppose. And depending on
                      > climate/maintenance - wooden blades
                      > can last well over 50 years.

                      As a wood/epoxy boat, car builder, I love wood.
                      But here in Fla and on boats, maybe from water spray,
                      wood rotors erode rather fast, having to fill in holes
                      every 6 months or so.

                      I think wood wins over
                      > anything else
                      > when it comes to fatigue.

                      That was certainly the case in early large
                      windgens as wood was the only material that they could
                      get to survive. The same was true in early cars,
                      trucks, aircraft. And still a great material for them.


                      >
                      > > For the blades a vinyl film like used to
                      > > repair car seats from most car parts stores along
                      > the
                      > > leading edge can help that damage a lot.
                      >
                      > Yes, or epoxy... or copper flashing stapled on
                      > there! (I kind of like
                      > that, it worked well on the old jacobs and
                      > winchargers)

                      Epoxy wouldn't work in boats. The vinyl was best
                      by far. If metal on adhesive backed SS you can find at
                      some car parts places used as stripping and muffler
                      repair tape.
                      Copper flashing, ect tacked on kills a lot of
                      power by ruining the airfoil.
                      As for wood vs FG, while what you say is true
                      about most FG/composite blades, mine are a much finer
                      shape, foil thus get better tip speed ratios and by
                      strand, COEffort placement, I get variable pitch to
                      the point of not needing other furling. These have
                      regularly hit by 90+ mph winds and survived well. And
                      they wear well, never had to repair one.
                      As a safety note, because the way they were
                      designed, not as likely to hurt you fit hit by it as
                      it bends if the forward edge strikes something,
                      important on a sailboat where it's close to people,
                      lines.

                      Thanks,
                      Jerry Dycus

                      >
                      >
                      === message truncated ===



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