Author Topic: Piggott Blades simplification possible?  (Read 38733 times)

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Menelaos

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Re: Piggott Blades simplification possible?
« Reply #60 on: May 25, 2012, 04:04:21 AM »
Hi Hugh,

I didn't get a notice on the update on this topic...sorry for answering so late...

For the small blades I do not use a drawing knife except for the root section. For bigger blades I definitively do use both, drawing knife for the root section and roughing out the leading edge and manual plane for the lee side of the trailing edge. A power plane is a tool that just doesn't work for me, whatever I do with it, it will destroy everything but I have about 30 different manual planers to choose from ;-)
...call me mad... :-D

I have recently made a Set of Blades with 3m diameter using my method. I did make the blade thicker there, especially on the tip section where it is about 11 mm thick. The wood blank was 20x6 cm laminated wood which is an easy to get standard size over here and when you buy it, it is already plane on all 4 sides.

I do not quite get your argument about the highest point of the airfoil...
I did cut through one of my test blades to see the different sections....it all looks good.

I now have my blades drawn in a CAD program so I can choose exactly where the highest point of the airfoil has to be on the different sections. and I leave about 1mm of space to get a nice round shape when connecting leading and trailing edge an still have the right thickness.
I do not see any difference to your airfoil shape concerning that. With your way you get the 2 sides parallel, mark the 1/3 line and work down from that section. In my case that line is the highest point from the beginning on the bottom of the blank wood. In the end the angles and the shape of the airfoil are identical to yours. Of course it is not quite correct the way I did it in the video. The way I marked the 1/3 line there is not really correct. In my CAD program I now did measure that point from the windward side and corrected the distance that has to be taken on the Lee-side. This is probably what you meant and you were right with that referring to the video.
Also using your numbers for thickness and drop for my method does not exactly give the same results on the final airfoil shape. I adjusted for that for another test blade and it then worked out correctly. I now have kind of my own design.

If you like, I can post the dimensions for the marks on leading and trailing edge for my 3m diameter prop here. There everything is correct concerning the angles and the highest point of the airfoil.

In the end everybody has his own style of doing it. For me, this way of carving blades is by far faster.
I have now made stencils for marking all the lines and I do make all 3 blades the same time....step by step to increase accuracy and processing speed. This way I can make a complete set of 3 1.5 m blades in about 6-8 hours, depending on how many people come by to disturb me ;-)

ps. My nickname is menelaOs and not MenelaUs...its a little funny as a "Laus" in german language is that kind of bug that lives in peoples hair... :-D

Max


Also I now only use 3 Stations, one at the root, one in the middle and one for the tip, I feel that this is enough

oztules

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Re: Piggott Blades simplification possible?
« Reply #61 on: May 25, 2012, 07:04:18 AM »

"
Also I now only use 3 Stations, one at the root, one in the middle and one for the tip, I feel that this is enough"
Ditto!




.............oztules
Flinders Island Australia

scoraigwind

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Re: Piggott Blades simplification possible?
« Reply #62 on: May 27, 2012, 03:22:28 PM »
I haven't tried using only 3 stations so I can't say how accurate the job is like that, but you must have to keep the cuts pretty straight to make the blades come out all the same with so few stations.  I am probably too fussy with all the measurements and the stages of my method and I will look at simplifying it more in future. 

I still don't see how you can mark the thickest point on a face that is not parallel to the windward side.  By definition the thickest point must be parallel to the other one.  If it's at an angle like you make it, then you need to remove more wood to get that point to be parallel, and then after that it is less thick.  But again, this it probably just my fussy attitude, and in practice the back is close to parallel in the outer part of the blade where it matters.
Hugh Piggott scoraigwind.co.uk

Frank S

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Re: Piggott Blades simplification possible?
« Reply #63 on: May 28, 2012, 07:41:14 AM »
 Hugh; after seeing his method and the way you do yours it reminds me of when Me and my BTN commander were building his twin engine 4 prop bi- plane. we got down to the props so we sought out a couple of German wood carver guys, this was back in the mid 70s  my COl. gave them his plans for the props. since the rear props were pushers they had a different pitch angle 1 guy did the front props while the other did the rears. It was like watching a carnival act  one guy was all MR. perfection in his measurements the other reminded me of an oilfield rough neck by the way he attacked the task for his measurements. But in the end both had a finesse  in the way they each finished polishing that would have made Charles Lindbergh proud.
 It will be a year or more before I get to the point of needing blades but I suspect that I will probably do the measuring of your method and the cutting modified from his done on a table saw used more like a CNC milling machine , by making a fixture to add a 3rd axis then drawing the blanks cross ways to the blade taking fine cuts while turning the blade about its longitudinal center line   
I live so far outside of the box, when I die they will stretch my carcass over the coffin

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #64 on: May 29, 2012, 05:29:49 AM »
sounds interesting...but I cannot quite imagine your cutting process. Maybe you can make a drawing on your setup...?

Max

Frank S

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Re: Piggott Blades simplification possible?
« Reply #65 on: May 29, 2012, 07:24:07 AM »
Menelaos ; here is a simplified explanation.
 First off it means you need a table saw capable of holding 3 to 5 saw blades as if you were going to cut a mortise & tenon joint some call it a square dado cut
 next you need a sine bar table with straight non tapered bars longer than the blade mounted longitudinally  to the saw blades  a fixture would slide on the sine bars with the work piece held in place the fixture needs to be so that it may be rotated and at each end and with some vertical and lateral adjustment
 a 3rd sine bar mounted above the fixture would elevate & lower at 1 end  an arm from the fixture follows this to create the rotation or angle required to scarf out a profile.
 then the blade and fixture is slid back and forth just skimming the teeth of the saw blades.
 Basically the table saw becomes a big scarfing router. anyone who has ever had to use 1 to take the place of a wood lathe for making long tapered or shaped pieces would understand I am sure.
 It works just the opposite of a panagraph and router and is probably more work than a band saw or chain saw method
and a belt sander is still needed to finish off the surface.
 The guys that made the Col's props only had 2 power tools in their shop 1 was a belt driven table saw the other a drum sander the sander had the drum mounted vertically and it osolated up and down everything else was done by draw knife chisel & leather mallet or hand planes   
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Menelaos

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Re: Piggott Blades simplification possible?
« Reply #66 on: May 29, 2012, 08:46:32 AM »
like this?

http://www.youtube.com/watch?v=g8hioldi6TY

or this?

http://www.youtube.com/watch?v=LmtMQeoKCu8

I was about to build one like I posted in the second link but then it seemed a little bit too much work and expenses for my needs...


Max

Frank S

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Re: Piggott Blades simplification possible?
« Reply #67 on: May 29, 2012, 09:55:59 AM »
Actually that second video would be a much simpler design than the concept I was thinking of. It would be pretty simple to build and could be mounted either on a table saw or a radial arm the tricky part would be with a fixed blade of a radial or table unit the rig would have to actually move up and down while the tracing arm remained solidly fixed in relation to the saw blade.
  The pattern and the blank would rotate together by  a chain & sprocket their axis would be mounted in the moving end of a double parallelogram arm set up which in turn would slide along on 2 linear bearing shafts.
 I might spend a little time and draw that up in my solidworks cad program to work on either machine 
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Menelaos

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Re: Piggott Blades simplification possible?
« Reply #68 on: May 29, 2012, 01:26:20 PM »
I did actually draw that ins Solid works 2007 as well...I will check out if I still find the file, so you can build up on that and don't have to start all over again... ;-)

For quite a wile I was really into that Idea but I am limited in space so I tried to make a construction that is very light and that can be easily disassembled. The machine has to be really stiff and accurate. Propellers are different from wind turbine blades. The sharp trailing edge is not so simple to cut accurately....if you want to get it working properly it will be quite an expensive machine. Sanding is needed anyway. I feel this is only good for a rough cut out...and it takes ages to properly set up the blank and the copy and to adjust it.

I have made quite a few blades now and I have practice with my hand- and Power tools and can get the work done quickly with those...
If I was to get some kind of automatation into the process, I would probably build something really simple similar to this:

http://www.youtube.com/watch?v=o7OH-Q2Vl6Y

I would make the windward side with the band saw as I did in my video. For 3 blades of 1.5 m length that takes about half an hour. The root part and the Lee side I would then make with that kind out router that I showed in the above link an leave about one millimeter of wood on top. It does not have to be too accurate. Again it would only be good to get the rough out of the Lee-side and the the rest done with the power sander. I feel that would be way quicker and cheaper.

I was a lille disappointed when I noticed that this great machine is way over my needs because I would as well really like to build it...but more for the fun of building it rather than for getting the processing speed up.

But if you really want to build that kind of machine I hope you put up plenty of pictures up and mae a video of it working :-)

Max


Radman1

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Re: Piggott Blades simplification possible?
« Reply #69 on: June 30, 2012, 10:49:21 AM »
Hi all, I built the Piggott six foot 24volt turbine this last winter, to say the least it has had it's ups and downs. I live in Oregon and we get our share of rain  in the winter. I carved the blades as described in Hugh's book. They came out OK but it took a lot of lead to balance them. I made the tower out of two 4x4x12 posts, so when it was time to raise the turbine, I drove steel fence posts about three feet into the ground. I never dreamed they could pull out, but the gooey mud let one go and it all came crashing down. Broke the blades and the tail but the turbine was OK. I had been thinking about how to make the blades a little simpler. I started with 2x6 ceder, for the root cut a 6" 15 degree angle in the end, I than cut one side out to give me a nice flat blank about 1/2 inch thick, I next made a cut from the root to the tip down too two inch's. all that was left was a little work with a sharp plane to shape the front and trailing edges. The tower is sitting in a crappy location with to many trees blocking the wind, I guess that's what happens when you live in the wood's. So can you guy's tell by looking at the picture if these blades are right? It has not spun up to enough speed to produce more than five volts.
Thanks for any help, Radman1     
« Last Edit: June 30, 2012, 02:04:22 PM by Radman1 »

jlt

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Re: Piggott Blades simplification possible?
« Reply #70 on: June 30, 2012, 11:24:10 AM »
  You need to bench test the alternator to check the cut in rpm. It should reach charging under 300 rpm.Also check out the angle on your blades from the picture it appears to have too  steep of angles. You need only about 1.5 degrees of angle at the tips.
 Getting it up above the trees will help a lot . 

Radman1

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Re: Piggott Blades simplification possible?
« Reply #71 on: June 30, 2012, 12:06:17 PM »
Hey Jlt, thanks for the reply. What is a optimum angle at the root? These blade are a snap to make on a bandsaw and I can cut any angle I want. I know it will put out the juice but a good site is a huge issue on this land. I built the tower so I can go up and down by my self, I made a steel sleeve to connect the 4x4's together and it seems to work OK but I am a little nervise about adding one or two more 4x4's to get above the tree's. As you know, when the tower is on the way up or down and is hanging out there at 30 degrees or so, it's just a lot of damn weight on the ankers and wire. I could not believe that post came out of the ground last winter.
Radman1 

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #72 on: July 22, 2012, 03:55:34 AM »
some time has passed...has anyone except me tried to male blades the "one side" way...?

Max

scoraigwind

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Re: Piggott Blades simplification possible?
« Reply #73 on: July 22, 2012, 02:21:47 PM »
hi Max,

I believe that Dan Bartmann mostly uses this approach when making smaller blades.  He has the sloping leading edge like that.  Cuts both the drop and the thickness at once.

I gave it a try last month for a small set of 2 metre diameter blades we built as part of a workshop in Ireland.  You can see photos and a video on my blog.  http://scoraigwind.co.uk/2012/06/workshop-in-leitrim-with-eirbyte/

It went pretty well.  Most of the work was done by one guy (he got hooked on it), and I did not also teach him my usual method (since it would be unfair to confuse him) so it's hard to tell whether this was easier, but it went well.  I am still a little bit uncomfortable with it still since the shape of the section is a bit different from what I usually aim for, due to starting with a wedge shaped piece, but I am pretty sure that it's only a problem for me and not a real problem so thanks for your input.

all the best,

Hugh
Hugh
Hugh Piggott scoraigwind.co.uk

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #74 on: July 23, 2012, 05:31:39 AM »
various browsers tell me that the server is down, so I cannot have a look at your block...will try again in the evening...

Max

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #75 on: July 23, 2012, 06:33:13 AM »
Was able to see it now...looks like you have had a good time :-)
I wish I was there just for the fun of it !

Are those blades flying already?

scoraigwind

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Re: Piggott Blades simplification possible?
« Reply #76 on: July 23, 2012, 03:35:28 PM »
we got a few hundred watts out of them but we had to take them down again.  It's a ferrite alternator on that one and I like it. Simple and strong. 
Hugh Piggott scoraigwind.co.uk

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #77 on: July 23, 2012, 03:42:32 PM »
Why did you have to take them down...? What happened to the blades?

With ferrets, don'T you often get runaways...?

scoraigwind

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Re: Piggott Blades simplification possible?
« Reply #78 on: July 25, 2012, 01:57:02 PM »
We only put it up to test it for the people who had built it.  This was not a permanent site.  I hope it will be tested for longer soon.  Seems like a nice machine!

I have loaded a lot of ferrites into the alternator and it has much more torque than my earlier ones, when ferrite magnets were expensive to buy.  So I don't worry about it running too fast, but it does run a bit faster than a neo one, and that is actually good for the performance.

Anyway I have a lot of neighbours with the early ferrite machines and they have run very nicely for many years with modest outputs and happy owners.
Hugh Piggott scoraigwind.co.uk

SparWeb

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Re: Piggott Blades simplification possible?
« Reply #79 on: August 16, 2012, 05:19:38 PM »
With ferrets, don't you often get runaways...?

Was that lost in translation, or did I miss the joke?   ;D
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024

bob golding

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Re: Piggott Blades simplification possible?
« Reply #80 on: August 17, 2012, 12:43:45 PM »
just been reading some of this thread while i wait for the weather to improve. serves me right servicing the turbine in august. :(
i noticed on the pics from Ireland  that Hugh posted of the one sided carving that there is a very steep angle to the root. i have always made the angle as shallow as possable. i cant see the point of having a sharp transition to the root,as there is not a lot of energy to be found  in the inner part of the blade.
any one explain the thinking behind the sharp transition?
 i am going to have to make a new set of blades at some point so am very interested in peoples thoughts on blade design.
all my blades have basically worked fine so it seems to me unless you have some way of testing your alternator on the bench it is a difficult to see if there any differences.

but that's just me if it works i am happy.
if i cant fix it i can fix it so it cant be fixed.

khloreen

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Re: Piggott Blades simplification possible?
« Reply #81 on: October 06, 2012, 12:24:11 PM »
Hi max!
I am working on a turbine of mine, I got the piggott book went through but found it a little difficult to understand the blade fabrication, I however came across your video online, and really like the work you put into the video, it was very understandable.
My question is
Have you tested that blade? And if you did was it as efficient as that of piggott?
Thank you in anticipation.

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #82 on: October 07, 2012, 04:40:52 AM »
I myself have not tried them yet but I made some sets for other people that are happy with the blades. The way I cut the blades will not effect the efficiency. All the angles and stuff are the same...
Anyway, those Piggott-blades are not on the top end of efficiency. They are easy to build, solid and run well, what more do you need. If there were differences, they would be too small to be really noticeable.

If you want an perfect blade ( whatever this means...) than you have to male a lot more effort and spend some money...

Max

khloreen

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Re: Piggott Blades simplification possible?
« Reply #83 on: October 07, 2012, 09:52:44 PM »
Thanks max.

stag

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Re: Piggott Blades simplification possible?
« Reply #84 on: February 10, 2013, 06:15:00 AM »
Back to the original question. How much simplification do you want. The ultimate in simplicity is an untwisted,untapered blade. And they work very well,given a good profile. It also has got to be much easier to get them all the same shape and weight.than hand carved twisted blades. If the outer two thirds of the blade provide 90% of the power,and outer one third 50%,with little twist in this area, then why bother with twisted blades at all. It may make aerodynamic sense to have some taper giving a higher aspect ratio nearer the tip which is travelling faster,but it's debatable how much difference this might make. The setting angle can be as small as 4 degrees for speed with ,maybe wedges glued on near the root to increase the angle and assist start up. I respect the knowledge and experience expressed in above posts,but even though I am an experienced woodworker/boatbuilder and have the neccesary tools, I can't see myself carving twisted blades any time soon.

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #85 on: February 10, 2013, 06:30:55 AM »
The problem with untwisted blades is that they are not that easy to make from wood. When it comes to Glas fiber blades I agree but with wood you then have a lot of weight on the tip section and the blades have to be quite thick and wide...too much and if you make it less in width you lack stability.

I now do my blades with the chainsaw...but also a one-cut version. I woll soon upload a video on youtube.

Max

stag

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Re: Piggott Blades simplification possible?
« Reply #86 on: February 10, 2013, 06:45:58 AM »
Fair comment. I forgot to mention that having been a boatbuilder I make  GRP blades,but had considered using wood in my next project.

mallikarjun

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Re: Piggott Blades simplification possible?
« Reply #87 on: February 14, 2013, 12:42:51 PM »
Hi This is Mallikarjun


I'm a student ,we r doing a project on axial flux permanent magnet generator for wind power

i am using magnets of trapezoidal shape magnets(NbFeB) of

with dimensions of outer diamater 60mm xinner diameter 47.5 X height 39.5mm and thickness 5mm

magnet grade 42 of NbFeB

since i m doing 8 pole rotor and stator would be star connected and i am using 12 coil for stator
 i need know about how many turns per coil should be used for 300watts capacity and the gauge of wire 
 speed would range for 350-400rpm


please help me out

JW

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Re: Piggott Blades simplification possible?
« Reply #88 on: February 14, 2013, 04:39:22 PM »
Hi All, just checking to see if this thread is posting from the newbies section.

I see Bruces logic moving this topic, its basic (the topic) good thing for new users to familiarize themselves with..

JW

Menelaos

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Re: Piggott Blades simplification possible?
« Reply #89 on: February 26, 2013, 06:56:33 AM »
As I promised, I did upload a video on making the blades with a single cut chain saw method, so here it is:

http://www.youtube.com/watch?v=aTloL-j5BSY


Max