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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 10:22am 26 Dec 2008
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Interesting profile on those blades at the butt. It would be a challenge for the chainsaw I think
For an axial I think it is a bit overdone, for an iron cored machine, it should help startup. The profile cutter seems to work a treat. Well done.
It all seems a bit complicated to me,so I will stick to the simple jig and chainsaw for the moment.... I think I lack your drive for perfection
..........oztulesVillage idiot...or... just another hack out of his depth
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 10:38am 26 Dec 2008
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Hi kiwijohn,
The travelling mechanisms are like the way a lathe bed and the cross traveller work. I have not made any reference to rotation of the work, if this is what you are implying. I had looked at rotating the work, but decided this was too hard, and I was not too keen on making a roller stylus and the hardware to mechanise the rotation. I am not keen on unattended operation. The linear design is good enough.
Hi phill,
Yes, this is a finished blade. I am presently reinforcing the trailing edge with carbon. This is <1mm thick, so the wood by itself, may be prone to chipping. I am using low viscosity 2pak for sealer.
The jigging system will simplify things, so all blades should end up close in weight and profiles. I will be removing gross excess timber with a table saw on future blades.
I will be using helicopter leading edge tape [polyurethane sticky tape] on the outer section of the blades, to reduce erosion. I have this on my older mill, and have no signs of wear after 2 years.
Gordon.Edited by GWatPE 2008-12-30become more energy aware
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 05:46am 27 Dec 2008
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Here are some pics of a blade so far.
This blade has a carbon fibre reinforsement,[just visible in pic 2] along the trailing edge.
The blade has a high aspect, with a thin section. There is ample thickness at the root end for strength and mounting. I was able to maintain the airfoil section all the way to the tip.
These blades are still a work in progress, so I will make one set and test, and then adjust if needed. This is the benefit of making templates, and not just copying from an existing blade.
nice blade Gordon, I could never get them that thin
PC
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:43am 29 Dec 2008
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Hi windman,
the templates allow me to cut the wood very precisely. There is no deflection in the template, so I can hold the stylus on the template with a lot of force, and this allows the carbide tool to replicate to a high accuracy.
I have made 2 blades and have decided to first cut only one side of a blade set, and then change the template and repeat for the other side of the set. This will allow me to keep the stylus setting constant and this will improve the precision of the cutting.
There was a bit of a difference in the weights of the first 2 blades. I would like to be able to replicate to within about 10g difference in weight.
I am surprised at how the blades look. If they work as well as they look, then they will be great. I have reinforced the thinnest section with carbon, and will probably continue to do so with all blades. The sealing will take some time. I am thinning the 2pak and this is soaking in well. The wood finish looks good, but I will spray finish after testing.
I hope to test fly the first set in a few days.
Gordon. become more energy aware
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 02:14pm 31 Dec 2008
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The wooden blades are coming along well. I have 6x halves made, and am starting the other sides. I have almost mastered the cutting.
I will not be taking orders yet. The novelty of the carving process is wearing OFF.
Gordon.
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 02:52pm 31 Dec 2008
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Gordon "The novelty of the carving process is wearing OFF"....Hehehe
It wears of even quicker when you have to cut the blanks out of the tree first
I found that thin epoxy paint (Luxepoxy), soaked in well to my crappy radiata pine blades. They show no sign of wear at all. Being so close to the ground, I do get massive insect strike, and the grass hoppers are getting shredded quite nicely I just wipe the smears off every now and then and they are away.
..........oztules Edited by oztules 2009-01-02Village idiot...or... just another hack out of his depth
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 12:51am 01 Jan 2009
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I didnt even get to make any blades on mine before deciding the process would be rather slow (and hence boring). So I have been thinking of a way to mechanise the process! It would not require a computer but a couple of windscreen wiper motors and some 'allthread' might be involved.
Gordon, do you make the router passes along or across the blade? Do you cut full depth in one pass?
[Mine is a great machine though for cutting weird shaped connector holes in thin aluminium panels though!]
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 02:03am 01 Jan 2009
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Hi kiwijohn,
The process is not at all boring. I enjoy the finished blade shape coming from a plank. I carved the moulds for my AxFx stator in a similar way in aluminium, on a mill. For the blades I now only use a stop depth. The roughing is done by eye and a steady hand. The waste material is cut away with the grain, so the cutter is pulling the fibres away. This makes the least noise, and removes material at the fastest rate, in big pieces, and reduces cutter wear. The last pass is mostly across the grain, where possible. The curve does not always make this the best way. Be prepared to make a lot of chips and saw dust.
I think that the motorised way with lead type screws and a roller follower with gravity to hold the stylus to the form may take much longer. Knots muck up the cutting rates a lot.
The material to be cut away is deeper than the router cutter length, so this cannot be done in 1 pass. There is up to 50mm to be removed in some places. This makes it difficult.
I find that it is really good to work without bending, and if the chippings fall away from the job. A flat work surface may not allow this.
Gordon.
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KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 02:27am 01 Jan 2009
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Gordon, I was thinking of a lead screw system making long passes the full length of the blade and being moved across a little after each pass. I had thought of the max cutter depth problem and had a notion of making two or three forms. I need to pay attention to your comments about the grain, thanks.
Probably outside my skill range but I was toying with the idea of monitoring motor current (and hence load) and reducing feed speed when the motor slowed going through a knot or a deep cut.
I built a 'tent' around my table with a sheet on the floor which sure saved on the clean up work! Edited by KiwiJohn 2009-01-02
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 07:14am 03 Jan 2009
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I have some comments to sparweb on the testing of capacitors thread, but I do not intend to dilute the cap testing aspect.
The data presented shows basically that no matter what was done, the power input plateaued at 350W input at 700rpm.
I have a recording clamp type amp/frequency meter. During my windmill testing with a single stator 100S 24V system ferrite rotor testing I have recorded 20+amps and a maximum 220Hz. This is 450 or so rpm. Something is happening with the stator and magnetic interactions, with capacitors to allow more power to be transferred by the same unit. I do not doubt that more power has been extracted from the wind and there may be losses associated with this, but at the end of the day, this alternator has been enabled to transfer double the usual power to the load at the same rpm. This is the unexplained benefit that series capacitors can give. This is more than efficiency, or power factor. even if the blades are working better, the alternator still has to convert the rotation energy to electrical energy. The gains cannot be explained by elimination of losses. There is a fundamental change to the alternator and the electro / mechanical interactions.
This may come out in future cap testing, but working out where losses are is not changing this increased power transfer fact.
Gordon.
PS Edit:
I am expecting that somehow, the capacitor is allowing the stator to operate at a reduced loading, and more magnetic field lines are able to enter the iron and induce current. The energy is simultanouusly transferred to the rectifiers and charges the capacitors. The energy across the capacitors is dumped through the rectifiers at the start of the next half cycle and this adds to the output current, before the next half cycle repeats. If you inagine that the output power does not plateau, but continues to increase with rpm [we will assume linearly]. This behaviour could explain how the stator is able to trtansfer the additional power... This is speculation, but hopefully Phill will be able to test this aspect as well.
Edited by GWatPE 2009-01-04become more energy aware
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 10:10am 03 Jan 2009
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Gordon I will put together a step by step sequence that happens as a gen takes on load .
The fp limits when te demagnetising force of the stator current is nearly equal the mmf of the rotor if caps are added the rotor flux is stronger and more output is available.
My suggestion is that you test a stator that has less turns ie ca produce power output without caps you want at highest revs you require then add caps in series to get low end performance .
I would myself rip all the windings off and wind again .
ie your 100 s is 44 *14 turns 616 you are using in delta so that would be 355 in star or per pole 25 turns
make a stator 1/2 12 turns per pole very easy to do at this stage dont worryabout neat.
As an example on my hydro i am doing 1200rpm with 7 turns getting about 20a 24v
having less turns the demagnetising force a lot less also open cct volts less. al win win
Herb
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:33am 03 Jan 2009
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Hi herb,
I see where you are coming from. I do not have a problem with the power you get at 1200rpm. I have measured the 20+amps @ 28 or so volts from an alternator that is only spinning at 450rpm. Bryans mill certainly was spinning at less than 1200 rpm as well for around 20A output on a 24V system.
The slope of the output W vs rpm, just after cutin is what I am interested in. Is it possible that the series caps have the ability to extend this linear portion of the output? This is the only way I can see where the increased power transfer can come from. Can the caps nullify the components that cause the output to flatten off?
I am tempted to take a F&P, probably series80 rewire 7p2s, to someone with a big lathe. I would take all the caps, inverter loading, etc as is and run the unit up. If the mill can put the 20A out, then why not on a lathe. This aspect keeps bugging me as I have to wait for a decent wind for measuring, but the maximums still happen. I have seen sustained 8-10 seconds with the mill fully furled.
I do not believe that the 100S is the only candidate here.
I cannot see how series caps improve low end performance, except with a resistive load.
I found that for a battery loading, series caps reduced the power at just above cutin rpm. This is why I started testing with a doubler, in addition to series caps. The series caps increased the upper power levels. This is not theory, but just what was measured.
I can live with the additional power produced, but it would be good to quantify things.
Gordon.
Edited by GWatPE 2009-01-04become more energy aware
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 12:56pm 03 Jan 2009
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Gordon.
If my conclusion on the other thread is correct, the caps cannot increase current in any way shape or form...The synchronous impedance is the current limit for any emf. ( I think I mean I=emf/synchronous impedance sort of thing)
If we have a high resistance stator, even if we get rid of the inductive reactance and tidy up the armature reactance, the current limit is still with the stator resistance. So even if we get XI down, and get the MMF up...the extra EMF gained will still have to be worked through a high resistance stator... and XC...
My hunch is that the 100s stator is the only one (1R?) that will gain well standard. The others will all require a rewind to get R down to somewhere respectable. Only then is it really worthwhile to use caps to get the other impedances under control.... and even then at 24v and above... because of the ripple noted by Gill.
Winding for low volts and using your doubler is a different story. Looks good for a poor mans booster.
..........oztulesVillage idiot...or... just another hack out of his depth
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 06:29pm 03 Jan 2009
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Gordon Should not have mentioned 1200rpm . I was just trying to show that rewinds to the rpm wanted give best output in fact if i increase the jet size this unit has no prob over 40 a.
All the tests show me that you are limiting due to killing the rotor mmf by the large number ampere turns on the stator. Caps will not be effective with the large mismatch you have in the windings. They are only a tool in increasing excitation not reducing it. Your need to use 100s in delta phils failure on 80s all show this.
rewinds easier than reconnects then no need confusion delta or paralleled windings
Herb
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:31pm 03 Jan 2009
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Hi herb,
the energy transfer density you achieve at 1200rpm, even with 40A is less than the series caps seem to give. By eneregy density, I mean W/rpm. I would expect over 50A at 1200rpm. The rpm is a problem of course with a windmill without gearing. My F&P system is basically simultanously 48V & 24V now at the max power levels, and 24V only at the lower levels, so the 100S in delta covers this well.
In the hydro units, the optimum rpm is a narrow band. The wind is not so obliging. The wind energy range can vary a hundred fold in a minute The dynamic range is what complicates an electronic system.
The caps varying impedance with frequency and the overlapping cutins offered with the ccts I use, gives a loading curve that verey well matches the wind energy curve, for my windmill config.
I will look at a rewire 80 14p, before I strip OFF all the wire. If I get a suitable match for 24V, I may be tempted to rewire in 1.5mm wire or so. I have always said that the alternator should be sized for the maximum power levels and then another external[be it DC converter, maximiser, doubler] arrangement be used to achieve current at the lower power levels, below normal system cutin.
Gordon.
PS edit:
Sorry Oztules, I was focused on herbs post.
I think current is obtained in a round about way with the series caps, from the stored energy that appears as emf accross them at high power levels. The path of least resistance to discharge is through the rectifiers, so this adds to the output current. This is sort of a Va-vA conversion. I cannot prove this as yet though.Edited by GWatPE 2009-01-05become more energy aware
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 05:41am 04 Jan 2009
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hmm I would have thought that any discharge through the rectifiers would necessarily have to see it's way through the stator and all it's impedances.
I'm not sure you can have different currents flowing in different parts of a series circuit?.... different voltage drops yes.
..........oztulesVillage idiot...or... just another hack out of his depth
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 09:02pm 04 Jan 2009
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Hi oztules,
Yes, the same current simultanously flows through each component of a series cct.
The current increase is most likely a result of the increased emf and reduced impedance. This would explain the currents I have seen without any magic.
Gordon.become more energy aware
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 10:31am 06 Jan 2009
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Hi readers,
My new carved wooden blades are up and flying. I have them on the AxFx mill for the moment. I have to make an adapter plate for my F&P mill. I will be taking down the drone[100S] stator. I will be rewiring another series80 to a 7s2p. This rewire in star will be a close match to the 100S in delta. I will rewire with options to give delta as well. I was able to twist the poles a measured 10degrees. I had previously only managed 7.5degrees. at 10 degrees, one pole finger is entering as the next pole finger is exiting a mag field. I have heard of much larger twist, but I am not sure if this was measured.
I mentioned on another thread the similarity of output between a twisted poles and untwisted, output emf waveforms. There is no discernable difference. I had imagined the twisting would flatten the sinewave, but this does not appear to happen.
On the topic of the new blades. They are slightly longer than the carbonfibre Lakota blades. The tip speed has increased slightly, and they develop a swish/swish sound at high rpm. I have had to readjust the maximiser to increase the loading and this has increased the output in the same winds. The gain is close to that expected with the slightly larger rotor area. The mill looks different with the natural wood finish on the blades. The clear coat method of balancing the blades has worked exceptionally well. I have not needed to add any balancing weights. I just kept adding thin coats to the lighter blades, until they all weighed the same. There was 90g difference in the wood. I will paint with white after the clear coat has hardened in about a week. I will add a before and after photo when complete.
Now to make a second set.
Gordon.
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 02:00pm 11 Jan 2009
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Hi herb,
I remember you asking for some loading and rpm figs from my setup with a doubler. The wind is not so good, so the test rig will have to do.
I have set up my test with a cap doubler from my windmill. This was one with 330uF 450VDC back to back caps, as in a photo I posted a while ago. I have tested with a single phase. This gives 1/3 of total output, so I have multiplied the currents by 3 and by the battery voltage to give effective power output. This test was with a doubler and normal rectifier connected to a series80 7s2p. This is very close in specs to the 100S.
the battery voltage was 27.8V.
I have included on the graph, curves for cubic wind energy, calculated alternator output power, loaded AC voltage and unloaded AC voltage without doubler.
There are several aspects to consider. Without the doubler, there would be no output below 145rpm. With the doubler, there is power output that follows the wind energy curve quite well from approx 75rpm. This is at power levels from 1-2 to 40-50W. The exact benefit is difficult to calculate, as the mill spins faster without the doubler, but this produces little power, until the rotor is loaded, and the tsr is brought back to optimum.
There are many tests that can be done, but this test demonstrates a lower cut in with 300W achievable at 300rpm. The series80 are common, and this rewire is just as good as the series100. I doubt that any of this would be of benefit on a stator that was not decogged. My stator has the poles twisted a measured 10 degrees.
There are no switches or relays, or sensors or microprocessors. The additional top end power matching reigime of my windmill requires full AC coupling of the windmill to the loadings. I am not recommending this at present as sourcing caps seems to be a problem. I have not been able to achieve full power range alternator loading to the wind energy with a single stator and single loading, with series caps, or a doubler. The low power levels are accomodated very well though with just the doubler.
Additional complexity of mill head components, with split windings etc would probably require rectifiers and caps on the mill head.
Gordon.Edited by GWatPE 2009-01-13become more energy aware
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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I just wipe the smears off every now and then and they are away.
