Fieldlines.com: The Otherpower discussion board
Newbies => Newbies => Topic started by: Menelaos on March 17, 2012, 07:27:15 AM
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Hi there, Hi Hough!
I have built many wind turbines so far but last week I visited "Fritzblitz" in Spain and we carved a set of rotor blades for a 2.4m machine. It was great fun and the blades turned out great :-)
Having them finished, I now wonder about some thinks and maybe some people here have already tried things in that fields or even Hough personally can tell me the reasons why he does thinks the way the are printed in the book.
So what did we do:
Forst we carved the windward side (Luvside) of the blades out of the blank peace of wood that we laminated togeter. Thats quite fast and easy. After that the thickness of the blades was marked on the leading and trailing edge. The blade was turned around so that the Lee-side was on top and again with a chiesel and later with a power plander the material was taken away. The next step would be to get everything to the right thickness in the 5 stations on that 1/3 line and when that works out, the shape of the profile towards leading and trailing edge is made...so far so goof and works out fine.
Now what I wonder about:
If I have a straight peace of wood with an even surface (which I can easily make with a power planer), why do I have to bother with the Lee-side so much? I could have all the 1/3 points on the same hight (level) directly on top of my plane peace of wood, only having to make the round shape on the leading edge and the "nearly straight line" towards the trailing edge.
Still this would not affect the angles on the profile on each station.
Of course, on the windward side, I would have to take off more material then but that sould not be a problem, should it?
So what is the reason to take off material from that peace off woof from both sides at the thickest point of the airfoil instead of only one side?
My guess is, that the way it is done, allows more accuracy during the carving process...
My backround is different. As I am also one of the leading people of that german discussion bord with a small webshop, we were thinking about offering cheap wood blanks.
My idea was to keep the highest point (the 1/3 mark) of the airfoil on top of the even peace of wood (on the Lee-side) and have the windward side waterjet cut. Tins would end up in high accuracy and low costs. All people have to do the is the easiest part: carving down fron that highest point of the airfils towards leading and trailing edge and no more measurements would have to be taken- the thing would be basically fool proof.
I could also have it watercut the way Hugh does it aproaching from both sides but then the peace of wood would have to be turned around on the machine and more cuts would be needed which makes it more expensive....and what we want is a cheap way of doing it.
Or would there be any aerodynamic disadvantages making it the way I suggested?
Would be nice to getting some help
Max
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höm...after reading my artice again I am not sure If I expressed myself understandable...
To make it more clearly again...what I suspect is:
The LUV side is made first up to a straight line on the leading edge beacause it is easy to rough it out by first makimng the orientation cuts with a saw and then roughing out with a chiesel or whatever power tool before planing it. I then have a straight reference area to mark out and cout down to the thickest point of the airfoil approaching from the Lee side... which is a lot easier that doing it the other way around as I would then have to watch two lines to keep level with.
If I can have the LUV-side waterjet cut with high accuracy, this would not be a problem anymore and the highest point of the airfoil that is on the Lee side can be on the same level throughout the whole profile and only the "roundings" towards the machine-precut leading and trailing edges would have to be made....
Am I confused or has it been done this way and works out without disadvantages other that accuracy problems when done without CNC technics?
Max
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There are many ways of making a blade. If you have a specific profile in mind then you need to keep the profile width thickness and shape at each station. It doesn't really matter if the leading edge is a straight line and you get the width of sections by curving the trailing edge or wether you keep things symmetrical about the centre line and end up with curved leading and trailing edges.
If you are going for a non specific hand carved profile then you have an almost infinite number of options.
There is some merit in having a thickness just sufficient at each point for the required strength, but it is easier just to fit the thickness on a straight line joining the full board thickness at the root to the chosen thickness at the tip.
Similarly you can make the width of each section correct at each station and end up with a highly curved trailing edge or curved leading and trailing edges. I find it works just as well to make a straight line joining the tip to the root again. This leaves the inner stations less than ideal width but it works as well and may be better unless you use mppt.
Similarly in the ideal world the front and back surfaces should follow a specific profile. Most people make the front face flat and that doesn't fit any known aerofoil that I have come across, but ClarkY and some of the NACA are nearly flat over most of the surface. Having made an approximation on the front, you can again make approximations on the back and as long as you have a thick part about 1/3 the way back and a sharp trailing edge it will work. ( unless you have means of plotting power curves you will never know how good or how bad it is, but blade matching will make more difference)
The old Lucas Freelite blade was cut with a flat front face of constant pitch, a chord that was a straight line from tip to root and a back surface that was part of a circle and was undoubtedly cut on a spindle moulder. It was simple and cheap to mass produce and worked well enough, especially considering that it was a very fast blade and these tend to be more critical.
If you can find ways to simplify things to suit your construction methods it will be absolutely fine. If you want to get into high tech methods of production then I would have thought it would pay to start from a specific profile known to be good for wind power rather than go to lengths of automating the production of a non existant hand cut profile.
Flux
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Hi Flux,
That helps a lot...anyway I am not new on airfoils and I know that the one describes in Piggotts book is far away from optimum. If you have time, one can start with rounding both sides of the leading edge in order to reduce stall and carve a little sagging on the front side...but those are Thinks that take time...for a few % of efficiency and for most folks it would be easier to just make the prop a few centimeters lager to compensate for that.
Over there in the US, people carve blades like hell. Over here they are scared of doing that as they feel it might be to complicated...Germans are strange when it comes to precission. It has to be perfect, not just close and they feel they cannot do this by hand...so they do not give it a try at all...
I personally like building props from wood, it is relatively cheap and looks nice and if something breaks, it can easily be fixed with epoxy or you just carve a new blade an thats it.
We do offer Hughs book and had it translated into german by greenstep.
Fpr people that are scared of making laser parts just like magnet discs and welding parts like the chasis, we offer cheap parts for that and also for the blades we would like to give some help. We do not want to offer completed blades. People want to have the feeling that it was them having made the blades :-) We just want to give some help on the critical parts.
A simplification by having the highest points of the airfoils on the same level (but of course keeping the angles right) and precut the the front section of the blade with a cnc machine will help those guys a lot.
I aleays remember when I made my first set of blades. I had an experienced guy teaching me and giving hints, Fritzblitz. He is also a member of this discussion bord, living in the middle of nowhere in the mountains of spain. I am not sure it would have worked out that well without his help. Some thinks you can read again and again and I would not understand it until I did it.
Precutting the with waterjet and moving the highest points of the lee side to the same level already deterines all the measurements needed. All there is left to do is to go don from that highest point towards the trailing an leading edge without having to meassure anything anymore. Everybody should be able to get a straight line done on the trailing edge and round the leading edge according to the right airfoil shape.
I feel that if precut sets were offered, many more people would give it a try.
The pre machining must not have do be complicated! In this case we would laminate the wood and precut it to the desired shape, then have it waterjet cut which is only needed on one side so that it is not nessessary to turn the piece over during process. It then can be made on a cheap 2 Axis machine.
It needs one single cut for the drop section on the front side and then the cuts that give the shape of the profile when viewed from the top. This really goes fast and should not be too expensive but it saves a lot of time and helps unexperienced guys.
Do not get me wrong here, we are not a commercial site: kleinwindanlagen.de
We are a discussion bord like this one with some specials that cost a lot of money. We opended a web shop to support these costs and the money does not go into private pockets- we do it in our free time after working to help people with their constructions.
I am saying this becaus we do not feel that we will sell hundrets of sets of blades. I already thought about building one of those machines and I have finished the plans as well....
http://www.youtube.com/watch?v=LmtMQeoKCu8&feature=related
But I the realised that the efford is enormous and that there are easier ways...
I want people to have it easy finishing the blades with a minimum option of getting someting wrong but not to get a finished product.
I now have already build some blades and for really experienced people like Fritz who have built something like 50 Blades, it takes him about 6 hours to carve a complete set of 3 blades for a 10 feet turbine that then only needs paint to be finished. It would probably take me 2 days although I have experience...but it only takes me about halve an our per blade to do what is left after having it pre machined the way I suggested with a minimum risc left to fv(k it up ;-)
Thats how I approach it...
Max
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I personally don't think it would matter at all, the thing to do would be to care a set that way and test them against a "normally" carved set.
Water jet wood carving is a new one on me I didn't know they did that.
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"Over there in the US, people carve blades like hell. Over here they are scared of doing that as they feel it might be to complicated...Germans are strange when it comes to precission. It has to be perfect, not just close and they feel they cannot do this by hand...so they do not give it a try at all..."
Max that is interesting. I suspect the same is true to some extent here in the uk ( except for the precision bit). I hadn't thought about it before but it is probably age related, I was brought up at a time when if you wanted something you had to make it, even if you could find a supplier you couldn't afford it. Now I think about ti I doubt that many younger people here would be prepared to have a go ( not without incentive from one of Hugh's courses anyway). I made my first blades when about 12 and it didn't seem difficult then apart from the lack of physical strength as a small boy ( it taught me to sharpen dad's plane and spokeshave to make life easy and that is good advice to anyone, without sharp tools woodwork is a disaster).
I am sure you can devise a basic layout that can be done simply by machine and leave the finishing to be done to the standard that makes the owner happy. Too much perfection is a waste of time, I once sent instructions to a carpenter to make a replacement prop for a freelite. He did it and was delighted, some time later i got a chance to see it and it was dreadful ,especially for one trained to work in wood, but it worked and he was happy. The main thing is to avoid complicated high lift profiles for hand construction, without precision they really are a lot worse than the basic Hugh style blades.
Flux
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Anyway, it might be a cheap or at least not extraordinary expensive way to simplify speed up the carving process. I will report on the results :-)
Max
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I see a lot of woodworkers use wood router duplicators to make airplane props.
Lots of video's on youtube and mostly with homemade duplicators.
Ive never seen or heard of anyone using this method for windturbine blades.
Seems to me a good way to to get accurate repitition (even use a commercial blades to copy from).
Ive used Hughs way and i like it, but i would uses a router next time.
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For the last weeks I really wanted to build a machine like this and I already made the plans and research for cheap material...but still, to get a unit that does not cover the whole work shop and still can be disassembled...and then still has high accuracy I would probably have to spend something line 3000-4000& for a 2 Spindle machine. Well, money is not the problem here and I would have lots of fun building a device like that....
BUT on the other hand it is not really needed for wind turbine blades. Propeller pros are different in shape and construction and I would probably have to make hundrets of blade sets to cover the costs. Furthermore I have to watch the machine during operation and it is not really fast and also I still have to do some work afterwards. All in all this to me does not really seem effective.
One has to see what is most (cost-) effective for the purpose needed. By the time such a machine has roughed a single blade, I have probably also finished what is left to do on the waterjet precut blades and more or less sanding is still required with both versions.
The more simple carving duplicators are cheap to build and deliver good copies but they are dead slow.
For quite a long time I was running after high end airfoils and now returned to simple airfoils whicha re then made a little bigger in Diameter to compensate for what others get with more efficiency for the benefit of availability and costs
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Hi Max.
5 years ago I made a router duplicator ,making blades.
It was made with a long bed with a sort of rail wagon and a pantograph mechanism on it.
On the right side a model blade (black).
On the left side a mill and a blank following with a finger on the surface of the example model.
Unfortunatly I did not work it out further . To much leeway , slow procedure,
I think the pantograph must have made of metal. ( square tube )
Must work it out later .
Just an idea.
- Frans -
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Germans versus Americans? I thought you were about to tell a joke!
I picked NACA airfoils for my blades, which have relatively flat bottom/front sides too. NACA 3415 to be specific. I got very very fancy with my carving process. For those who would object to a complicated geometry like mine, there is a lot of benefit to your simplified approach. I have seen blades made by carving only one side, then gluing wedges to the root faces, to give them the pitch angle they need to have a correct TSR.
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There are many ways of doing it. Today I started cutting the wood for my 5m Machine, tomorrow I will glue them together...
I am not yet sure which way I will carve them, the Piggott style or the one I found on Dan Lenox page...
I like the easy way with 3 stations and the flat design that saves wood but I do not like the way the root is made for stability reasons and optics... so I will probably make a mix....
Anyway, this is not as much science as many people think. Near the root up to half way up the blade the desin and shape is not critical at all as hardly any power is produced there anyway. That leaves room for simplifications. Also Piggott found out about that. In his 2003 book the trailing edge was still curved to make a hard life for people with a power planer and belt sander ;-9
Now it is a straight line like in the "american" version.
I really tried to work out things until I got a headage and then remembered tose extrudes aluminium profiles that some guys at "the backshed" and also over here use....with constant cord and pitch- and they perform really well. The guys from that "royal blade fabrication" or whatever their name was again...also do it that way and thus make it really simple to carve...
So what is done in the books now is a straight trailling edge and it would probably also be ok to make a straight line from tip to root concerneing the thickness of the airfoil.
I have seen hundrets of different blade designs also on commercial turbines and the variaty is great...from that and also from my own experiences I concluded the following:
1. The width of the airfoil is not critical at any point. It should be less on the tip for various reasons, mostly for reducing weight to keep centrifugal forces low that pull on the root section in high winds. So a straight line from root to tip like it is done in booth books now is fine
2. The verry same thing applies to the thickness of the airfoil. Tkae a NACA 4412 for example and reduce the hight of the airfoil and you end up with a 4412 which is fine as well. So basically there is no need to make hundrets of staions in between root and tip like Piggott does. Also here a straight line indicating the thickness from root to tip would be absolutely fine...now the Dans have added a middle section...ok...why not...fair enough and helps not to get stuck with the power planer all the time when it comes to the next station where the "line of thickness" makes a downcurve again...
3. The only really important thing is to get the angles right on the side that faces the wind and again 3 stations is more than enough here as the inner half of the blade is not critical with the angles and also not really involved in power production.
and of course the tickest point of the airfoil should be somewhere at about 1/3 from the leading edge...
Doing it that way it will not be high tech but high efficiency of the working process ;-)
Any objections?
Max
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I tend to agree with your simplification approach to carving. I do the same thing: carve a flat front face (windward side) without taking material off the windward-leading edge side from the root all the way to the tip. Most of the material removed is from the back side. The cord width (at three stations) is cut with a jig saw before blades are carved and lines are drawn to allow you to carve to that profile. I have been doing 12' diameter bladesets lately and I stick with 4 degrees of pitch at the tip and carve as deep as the root will allow. Most lumber I have been using is 2"x 8" milled Doug Fir lumber and some clear cedar. The blades work fine, and are very quiet. I have set up a jig to cut these with a router and that works really well. Most important is to allow the wood to acclimate to the environment before carving to avoid warping when a lot of material is removed. Leading edge is rounded with a power planer and the back of the airfoil is measured 1/3 cord width from leading edge and also rounded down to the trailing edge with a power planer. They work fine, and I have seen no reason yet to make it more complicated than it needs to be...at least for the mean time.
RoyR
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I think in #2 you meant to write something different, such as "4415... 4412" or thereabouts. I get the point.
I would add that it is very important to make all of the blades in a set match in size, twist, and weight. This could be more important than fidelity to any chosen airfoil or width measurement. Consistency will drive you to make tools such as profile cards, to compare each blade against the same reference, and to work in stages. I chose to complete only a few carving steps at a time on all 3 blades, before moving on to other refinements, to keep them as similar as possible. Of course, automating or mechanizing the process will help a lot.
But now that's moving away from your goal of simplification.
To get the "angles right" on the incidence of the blade at the tip and root stations, you are forced to have a curve in the trailing edge. If you want a straight trailing edge you must make a compromise. It's probably not a major compromise. Even the NREL published a test report (years ago) where their untwisted and twisted 12-meter blades seemed to perform equally well.
I am not convinced this is true, however there is some evidence that having a well-twisted blade will help overcome the starting torque of some generators or gearbox arrangements. My twisted blades may do me a favour in this regard, because my generator is a motor-conversion, not an axial-flux design. I think you said you are committed to building axial stators in the future, therefore the straight trailing edge will be okay, but remember that there are other generator designs that benefit from a different blade.
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You are right, I meant 4412 and 4415...misspelled somehow without noticing...
Anyway, all of this stuff is not about havin it the cheapest and easiest way...
The cheapest and esiest way probably is to use those extrudes aluminium GOE 222 airfoils that we will also soon have in our shop. They are cheap, verry robust, weather proof, do not need maintenance or any treatment ans basicall last forever...and most important: they run great.
Those "simple extrudes profiles" are not that simple at all and have great advantages over "high performace blades" in the real world, especially if the location is not perfect and some turbulances can be expected. You have to understand why they are not that simple and why they perform so well...but thats another story...
The point is: making blades from wood is not done because it is cheap or easy but because you do it yourself. You start with some peace of wood and end up with something you have created yourself, thats the point. People like us do not want to buy stuff, the want to make it themselfes and be proud of it...
Thas some kind of philosophy...and for those that wish to do so but who are scared of not having the skills, those simplifications are a great way to go...and some would be happy to have pre-manufactured peaces that they only have to finish off...
That chainsaw method is a really good approach to that...but not everybody has the equipment for that so I like they way of simlifying it for those who have to do it manually...
I am exactly that kind of guy...
At the moment I am carving a 5m diameter prop from wood. And I do it the old fashioned way... I have those extruded aluminium blades in stock that I buy for 30 Bucks/meter and which will last longer and are cheaper and more robust...but I choose to make a wooden prop because I like making it although the timer I buy is more expensive that those finished blades...and many people feel they way I do about this...I believe...
Some guys live in remote areas and only have the cance to carve their own blades...and there are others that live in Berlin city but want to pretent living in a remote area and coose doing it the way they would do it if they were at a diffferent place...
This can be compared to those people that take part in survival courses althoug they have never seen a real forest in their live...just in case...
Sounds odd...? Maybe...but its not really far from reality...
Max
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I've used both the extruded blades and hand carved blades. I tend to agree, the extruded blades perform well and are easy to use, but timber does have some advantages. If you have the tools handy, like a chainsaw or electric plan, then you cant go past Oz's blade making technique, its cheap and works well, and scales up nicely. For blade lengths over 2 meters I would not use the extruded blades, unless its extended out from the hub. By that I mean, for a 5 meter turbine, use 2 meter blades on 500mm extenders.
I think way too much attention is paid to the root area of the blade. The inner 1/3 of the turbine provides less than 10% of the power, where the outer 1.3 provides over 50%. So when carving the inner 1/3, you may as well concentrate on making it strong instead of a nice airfoil. If your concerned about loosing that 10% of power, extend the blade out an inch and you have more than recovered any power lost in the root.
Also, there is very little twist in the outer 2/3 of the blade, and virtually none in the outer 1/3.
Glenn
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you are absolutely right. Over here there is a guy working on the university in bremen. Dr. prof. Horst Crome who developed the "Kukate" wind turbine using the aluminium extrusions which is used in 3. wolrd countries ...hundrets of those were installed and keep surviving under all conditions... He uses "half bladers". The inner half of the prop is left without profile and only the outer half is used which generates 75 % of the total power. The none-existant twist is then not critical anymore and as you stated, making the blades a little longer will compensate for the inner half of the ptop anyway...but a lot more effective, also concerning torque. so for 3 4m turbine all you need is 3m of extrudes profile which is equal to about 100$. you the need the Hub and the metal pipes to put the airfol on but you end up with less the 200$....and they work great woth even high effiency...but to be honest...it lokks absolutely forbidden :-D ...horribly ugly...as I think...but the need for energy compensates for that if really needed and not just wanted for the fun of it...
Max
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I once again want to get back to those simplification option...
The chain saw method is the right way for those who do more than only one set...and I might be wrong in some way that I do not see yet but I feel that one cut would be enough, why using two jigs...?
On Dan Lenox webpage I found those pictures that in a similar way are also in the Plans:
[attach=1]
With the red lines he marked what was not clear to him in the beginning. Those red lines are congruent throughout the whole blade...
OK, what people do now is, cut the windward side and then use a band saw to make the Lee side....then on the Lee side round the leading edge and finish off the more or less straight side towards the trailling edge beginning at this about 1/3 point...
The do it the same when they use the chain saw methos, do 2 cuts....
Now what if we arrage it this way as the following picture shows. Now the blue lines are congruent:
[attach=2]
In that case, the second cut on the Lee-side is not needded anymore. and only trailling and leading edge have to be brought into shape. The windward side must be done anyway. Now it would be the windward side that is cut with the band saw to get the thickness on the leading edge end. Working from that line then will be the usual process for making the flat windward side.
In the Dan's Plans, there are inly 3 stations anyway, tip, root and middle. Of course this is simple but it works fine.
One more advantage of the solution I suggest: When only one side is cut away and the other side is nice and flat because it might be flattened with a stationary power planer, the tolerances are a lot less when trying to get the thickness right if the stations and lines between them are marked carefully. As the windward side is a flat surface, there is hardly any chance of not getting it right and equal on every blade. Then getting the hight of the airfoil right will occur automatically...and finally I also feel it is easier to work out the windward side as the whole blade can line up on an table or workbench as the untouched leeside is still flat and even which gives more stability and less error.
and for the chainsaw guys now only one single cut for the windward side is needed anyway which spares one jig...
What do I miss...?
Max
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The twist, if the lee side is lying on a flat surface it won't lie flat because it twists, if you are making flat no twist blades I don't see a problem.
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Maybe I am really confused and lacking imagination now but I don't get it...why shouldn't there be a twist anymore???
The absolute twist is on the windward side. I do not feel that anything changes concerning that, does it? The twist will be still there...
edit: hold on, I think you got me wrong. The lee side is of course not flat, you will still have to work out towards leading and trailing edge from the highest point of the airfoil...but before you do that, you will cut the windward side and as all the highest points of the airfoil are on the same level, the lee side will plan on the table BEFORE you go towards trailling and leading edge.
I sometimes have problems making myself clear in a foreign language... :-(
As pictures are multilingual, I prepared another one and moved the stations from the picture of my last post together...that should make it clear now....
[attach=1]
So I feel that in general, this method will provide much higher accuracy whatever way (hand work or chainsaw or bandsaw) is used to get it done AND will save a lot of time...but angles will result the same...
I was about to make a CAD-drawing on that...but it is probably faster to just go to my workshop somewhen next week and make a blade sample and to take pictures of that ;-)
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OK, I see it now and you are right, I think it's a good plan.
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Ok, I am glad I didn't finally confuse myself ;-)
I am still wondering nobody came up with this before but someone has to be the first and maybe it can help others to get it done more easy and accurate. I will post pictures of how it turned out. Until then, comments are welcome... :-)
Max
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Well it certainly would simplify the chainsaw method, you only need one jig.
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Thats what I thought...so next tool I'm gonna buy will be a chainsaw ;-)
I doubt that my neighbours will be too happy about that :-D
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They will get used to it. ;D
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So today I did make 2 test blades using my new method. I did everythink with hand tools, except a power sander and the band saw for the rough part. It turned out really nice, the best blades I have ever made regarding accuracy. It just can't get wrong. I did it with 6 stations. After drawing all the lines in the beginning I didn't measure anything during the process until everything was finished. I was surprised when the thickness of the airfoil at the highest point on ALL stations turned out to be exactly what it was supposed to be, not a single milimeter off, thats great. It also looks nice. My digital camera broke so I will post pictures tomorrow when my friend is back home.
It really is a lot easier doing it "my" way...
Max
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Mad Max's simplified blade carving method (MMSBCM) pat pending. :)
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8)
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I haven't used them myself, but they do make electric chainsaws, which might placate the neighbours.
I will try your method next time I make a set. I have cut a pine tree up, and am waiting for it to cure at the moment...... then I will "Menalaos" it with a chainsaw into 4m blade sets. :) .... only 1 jig... interesting. It does mean a lot of planing on the lee for 4m blades. but I will see if it is worth it. It may prove that 2 cuts and 2 jigs still saves a lot of time, but who knows till it is done and tested.
...............oztules
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it does not need more planing on the lee side than with the other method, it just spares one cut and one jig...so half the work to be done and as we only approach from one side, accuracy is a lot higher...try it...! :-)
so on the leading edge side you mark the thickness startng from the lee-side and on the trailling edge side you mark thickness minus drop also starting from the lee side so that you have the same plane of reference. You connect those two lines with only one chainsaw cut and you end up with the correct twist of the windward side. the highest point of the airfoil will be on the reference plane. It will thus automaticalle result in the correct hight of the airfoil.
All thats then left to do is the usual thing- shape leading and trailling edge starting from the highest point of the airfoil, so on the plane lee side just mark that 1/3 line and get it started...thats really quick work anyway
Max
Max
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Hi,
This method sure looks interesting. I'm going to need to make one new blade set this spring, and originally I though of using the "traditional" chainsaw method for those.. But this thing looks even easier I think.
For the side of the blade facing away from the wind, mayby it could be rough-cut with a chainsaw manually before starting with the planer, to reduce the amount that needs to be shaved off? I did that with my last blade set, keep the chain speed high and keep the cutting bar moving (sideways..) and I actually had quite a good control over it.
I think electric saw is better for this job, it does not have as much power as a gas powered one, but it's lighter and much nicer to use especially if working indoors. That's what I've used before for roughing up blades.
Has anyone experimented about how to best file the chain for this kind of job? I think I read from somewhere, that for cutting along the direction of the grain, it would be best to have a worn out chain (so the rake is quite close in height to the cutting teeth), and reduce the cutting teeth angle to 15degrees for best results..? I think I'd best try a few settings before actually cutting my precious blanks :)
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You can get a "ripping" chain... less teeth.
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For the side of the blade facing away from the wind, mayby it could be rough-cut with a chainsaw manually before starting with the planer, to reduce the amount that needs to be shaved off?
The side faciong away is not touched at all as this is on the bottom of the wood piece over all the length(!!!)
Actually a chainsaw is not even needed, it works great with a band saw as well...Today I made a complete set of 10 foot diameter prop in only 3 hours...all I need is 3 cuts with the band saw. The first one is to get the shape of the blade as usual (from root to tip on the trailling edge). I the put the marks as explained in my previous post. I then use the band saw to cut the thickness of the blade from the leading edge. This cut then is smoothed a bit as it will be reference for cut number 3.
Cut number 3 will give me the windward side with the twist. I Put a flat peace of wood (about 2mm high) next to the band of the saw to have a guide and then cut along the drop line of the trailling edge with the blade standing on the leading edge.
Those 3 steps take about 20 minutes for all three blades. I then take the power sander to get the windward side finished and form out the root section to whatever ones Eye likes. After that I turn around and make the lee side which is fairly quick work with the power sander....really fast, no jig needed, no chainsaw needed...but still I want to try that chainsaw thing and have ordered an electric one ;)
Maybe its a good idea to make a video clip of the whole process...
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The side faciong away is not touched at all as this is on the bottom of the wood piece over all the length(!!!)
Hi Max,
What I meant, is to first rough cut the trailing edge with a chainsaw (from the high point of the profile, to the trailing edge) to reduce the need for power planer time. But now thinking it again, the amount of wood removed from there is quite small, so it might not make much sense to put the chainsaw to work in there.
For the side facing the wind, I'll have to go with the chainsaw, as I don't have a band saw big enough to cut it :)
For some reason the ripping chain does not sound too good, as the goal is to make a cut as clean as possible, to reduce the need for sanding.
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there really is only little material to take off from the lee-side, nearly nothing up to half way from the root of the blade...at least for the trailling edge...its really not worth it making this with a chainsaw. If you want it quicker, I would use the power planer but for my small 10 foot blade set I used a manual planer for that and the did the fine tuning with the power sander and later by hand.
This whole method of course only works out accurately if the Lee seide of the untached wood is absolutely even. For this I do have a surface planing machnineso that I can get it nice and even and the right thickness...
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Ok...I did make a video but it still needs to be cut and in some parts I had my hand on the microphone so that needs fix as well... After easter I will post it here and I hope you will like it...
Max
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Well, here is the video:
http://www.youtube.com/watch?v=tK-83KUKC8w&feature=youtu.be (http://www.youtube.com/watch?v=tK-83KUKC8w&feature=youtu.be)
It didn't turn out well and I will make a new one somewhen but for now it' ok ;-)
Its hard to to stuff and explain things in a foreign language the same time, so please do not kill me for my english !
When my chainsaw arrives I will make a jig and see how that works out ...
Max
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I got a "This video has been removed because it is too long. "
Glenn
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oh sh...I will see what I can do about that....took me 2 hours to upload it...
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Ok, I started a new upload and changed the link in my previous post, should work in about an hour.
That video is 27 minutes long so I had to do some activation on my account first to be able to get more than 15 minutes uploaded...
Max
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I thinks its very good Max :)
Thats a scary bandsaw you have there!
It should be fairly straight foward to modify Oz's chainsaw method to use your idea Max, and that would mean only one cut.
Well done.
Glenn
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Yeah, that band saw is a monster. It was built in 1922 and has a weight of 2 tons....equiped with a 5 KW motor and if you switsch from star to delta too early it will kick all the fuses in the workshop :-(
With a chain saw and only one cut needed this could be a good way of beating the time world record in blade carving ;-)
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If a picture is worth a thousand words, this video is worth a million.
Good job, Thanks for posting it.
It makes blade carving seem much more possible for someone who was always hesitant to try.
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That's a great video.
After watching it I got a brain fart, how about mounting a electric chain saw from underneath a table with blade sticking straight up. Sort of a redneck band saw.
JLT
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I've been carving blades using Hugh's method for about five years now so I was sceptical about how much easier and quicker this method is. After watching the video I built a set of 3 blades this morning for a new 1m turbine I'm working on and wow, I'm a convert now. I had been using a band saw for rough cutting my blades before but some cuts were tricky and really slowed down the process. With your method the cutting process is now a lot easier and definitely quicker.
The lay of the blade is different to what I am use to so looks strange. Will be another two weeks before I get this turbine up in the air and connected to the data logger to see how well the new blades perform.
Thanks for sharing your work and making the video. I agree too that in the video you did a great job at explaining your method, no need to redo it.
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Thanks!
@ jlt:
That came to my mind as well but I guess that it will be quite difficult to handle as the chainsaw blade is really thick...but I didn't try it. I feel that if you want to get it accurate with a chain saw, using a jig is the best way of doing it as you have to points to guide the chain saw blade with some preassure...
The advantage on teh other side would be that building an "band saw" this way would be really cheap if you consider that you then can cur really thick blocks of would where cheap band saws can only do a few centimeters.
Another problem might be that the chain saw blade is really wide. This might be good for straight cuts but for getting angles it will be difficult. Furthermore with my method you will have to cut "up hill". What will then happen with the back side of the chainsaw blade, will it damage the wood that is left? I cannot tell as I have never used a chain saw in my life befor... ::)
@ Jeff:
The blades will perform the same if you used the same angles and dimensions. Basically nothing changes to the airfoil or the stations....but anyway I did not expect someone would try it only a few hours after I put the video online and I am happy that you can confirm that it makes things easier :-)
Would be nice if you can post your results here!
Max
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I've spent a lot of time running a chain saw, the chainsaw/bandsaw would scare the F out of me, that would be an imminent castastrophic injury waiting to happen.
"Here hold my beer and watch me saw my arm off"
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Menelaos, very nicely done and great video. Thank you for you for your time.
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this discussion bord is all about sharing, ricght? ;-)
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Absolutely right.
Rgds
Damon
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it would actually be nice to hear how Hugh feels about that...
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it would actually be nice to hear how Hugh feels about that...
You may send him a pm with a link to this thread. His user name here is scoraigwind
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it would actually be nice to hear how Hugh feels about that...
Max, if you put these blades on a machine and it performs as expected, to put it bluntly with NO disrespect intended what does it matter what Hugh thinks?
FAB , I knew what you meant, but wasn't where I could fix it , fat fingers & small keyboard on phone :(
Bruce S
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just because I want to let him know as my idea developed from the plans in his book. He gives those workshops around europe and he writes those books on how to do stuff and I am sure he does not mind knowing about different ways of approach and mybe adapting it...
I am not sure if I got the meaning of that last sentence right...but to make it clear: this has nothing to do with disrespect. I do not want to walk around telling everybody how great my style of doing it is and how much all the other methods suck...
I just want to share the solutions that I have found to make things the way that I feel is a lot more easy and accurate and as Hugh has a lot of experience in blade carving and I like what he is doing over there, I feel he should be updated on things like this...
Max
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Fair enough.
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it would actually be nice to hear how Hugh feels about that...
Max, if you put these blades on a machine and it performs as expected, to put it bluntly with NO disrespect intended what does it matter what Hugh thinks?
Had to change that a little, I forgot the "NO"
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ok, that makes sense now :-)
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hi guys,
It is probably a little early...but has anybody already tried to copy my approach of making blades?...it would be nice to get feedback on the procedure and of course on the results :-)
Max
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Hi guys,
Sorry for not replying sooner, but I don't get around to looking at this board very often. I am kept very busy with emails. Next time maybe somebody could send me an email and I will check in.
I agree that this is a simpler way to do it. Dan also uses this method I believe. He doesn't seem to read this board much either...
I do have a reason why I do it the way I do and I am not sure it's a good enough reason but I will explain it anyway. I like to make the airfoil from a rectangular section of wood where the back is parallel to the front. That way I know that the thickest part at 30% is actually the thickest part. If the back is angled, and the 30% line thickness is a certain value, then this cannot also be the thickest point on the back. In my way of thinking it can only be the thickest point if it is also parallel to the front, windward face. I don't like any sort of corner at the thickest point, it should just be the top of a very gradual curve and as such it must be parallel to the front face.
So that's my logic. It seems to me that the main saving in the 'Menelaus' system is that you don't have to measure and mark so much. In the end you do have to cut off the same amount of wood and you do have to make two finished faces. I know that all sorts of shapes work well, and I have seen blade sections that look awful to me and fly OK. I don't have any objection to people making blades in any way that works for them and I personally do make changes to my blade carving procedure so as to make life easier at times. I will think about modifying my instructions to reduce the number of stages and the amount of measurements that need to be made. I am not convinced it would save me much time as I am pretty quick at doing it my way but of course a simpler way is quicker to learn.
Thanks for sharing ideas!
Hugh
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OK now I have watched the video I have a couple of other comments.
Nice work! It's a quick way to make the blades. I wouldn't enjoy doing it that way very much, but I appreciate that the pleasure of using sharp tools without noise and dust is not everyone's priority. The use of the bandsaw is very ingenious. It seems to grunt a bit at times when the twist gets tight, but Max knows how to drive it. He doesnt' seem to use a plane and hardly uses a drawknife but maybe he tried that already and found it too slow.
I do have some worries about the 'thickness'. The thickness gets marked at the leading edge but then a reduced thickness gets marked at the trailing edge so there is a tapered shape where the back or 'lee' side is going to be a bit sloping relative to the windward or front side. So you lose some thickness (especially at the inner end). You also end up with an angled face at the 'thickest point" which as I pointed out in the last message is not going to be the thickest any more unless it is parallel to the front.
I am probably nitpicking here, but suggest you might want to add a bit of thickness if you want the blades to be as strong as I like to make them. Other than that I can't fault the resultant shape. What works for you is fine by me. I put the video on my blog at http://scoraigwind.co.uk/2012/05/making-wooden-blades-with-max/ (http://scoraigwind.co.uk/2012/05/making-wooden-blades-with-max/). Thanks again!
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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
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"
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
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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.
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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
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sounds interesting...but I cannot quite imagine your cutting process. Maybe you can make a drawing on your setup...?
Max
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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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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
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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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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
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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
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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 .
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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
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some time has passed...has anyone except me tried to male blades the "one side" way...?
Max
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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/ (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
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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
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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?
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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.
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Why did you have to take them down...? What happened to the blades?
With ferrets, don'T you often get runaways...?
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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.
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With ferrets, don't you often get runaways...?
Was that lost in translation, or did I miss the joke? ;D
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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.
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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.
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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
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Thanks max.
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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.
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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
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Fair comment. I forgot to mention that having been a boatbuilder I make GRP blades,but had considered using wood in my next project.
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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
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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
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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
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Hi Max.
Great work.
- Frans -
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Thanks.
It does work ok but I prefer the band saw method over this one. You can see the problem in the video as well:
If you get close to the root of the blade, you have to make several passes to get the correct twist. The blade of the chainsaw tends to lift off from the guide rail on the trailling edge. This is because on the leading edge side of the blade the chainsaw blade has an angle going upwards but has to go downwards on the trailling edge side. So you have to twist the saw blade to get that done. Using the piggot Style blade and applying the chainsaw method to that one, the problem is not that bad as the leading edge is on the same level all the time. Doing it my way it is the back side of the chainsaw blade that has to rip off the material near the root of the blade. This results in the blade becomming blond quickly and you need a lot of power as you always have to press down the tip of the saw blade. I have now mounted a handle near the tip of the chainsaw blade. This way it is possible to push the saw sideways which saves a lot of human power and helps reducing the number of passes towards the end. BUt still after a set of 3 blades the chain has to be replaced or sharpened...ok...it costs about 5 bucks so no problem but I wanted to mention.
As the band saw blade is a lot less in width, that problem is not an issue there.
But finally if you apply a handle on the saw blade it is a fast way of making a blade and having to make only one jig saves time and also space in the work shop.
Max
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when I saw the video I was going to ask you why you didn't add a handle
some guys who do a lot of chainsaw sculpture will have a special bar that they have ground supper thin allowing them to twist the bar out of shape and use bow bars for weird and special cuts
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well that would be a good solution...do you have an example for such a blade, I guess that that would be quite costy...?
Anyway, it also works with my standard blade in combination with the handle attached. With that one it is possible to get at least some flex ( you cannot get any if you do it without handle like shown in the video ) and you can push the blade down.
I can live with it. If I am planning on making 50 Sets of blades, I would have them water jet cut the same way that I use the chainsaw now, use a simple copy carver to make the leading edge side on the lee side at maybe 4 Stations and interpolate between them manually with a drawing knife and band saw...or use a 3d water jet machine to make those guide marks on that lee side...that would be the first cuts...then turn around and make the windward side. It is easy to adjust on the table as the lee side remains flat :-)
That should not even be expensive when we are talking about 150 pieces to maybe offer to people to finish themselves. But here in Germany, wooden blades are not that common and we have funny rules that make it hard to get permissions to put up turbines and expensive so it would not be worth its...and not as fun as making it the ways I showed here ;-)
Max
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No I don't have an example I only saw this one guy doing speed sculpture at a loggers competition back around 1993 His whole chain saw was homemade he looked like Edward scissor hands the way he maneuvered that thing it was driven from 2 flex shafts 1 running down each sleeve of his jacket the tools and bars were quick connect so he could switch from using 1 or 2 tools the bow or one of several bars the engine was on a back pack it looked to be a motorcycle engine of some kind hard to tell what it was
the 1 flexible bar he had was about 24 inches with a handle out near the end It looked like it would have been really tough on the chain and the bar to bow it and twist it like he did I think he lived somewhere in Oregon
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has actually anybody tried to reproduce my single side method...?
I would be interested in the results...
Max
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has actually anybody tried to reproduce my single side method...?
I would be interested in the results...
Max
i have to make a new set of blades soon so will give your method a try. i have always used windstuffnows figures before so time to try something new. i am in a high wind area so any shape will work around here. wind is mostly in the 30 to 80 mph range in the winter. i am using solar at the moment so have plenty of time to play with the blade carving.
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Fellow blade makers,
I have just finished my third blade using Max's chain saw method. It was very fast! I modified a 14" electric chain saw by cutting out the center of the bar to allow it to twist and follow the guides perfectly.[attach=1]
I allowed 1/8" extra to remove the saw marks and to get the slope perfect. I used a hand plainer, Block plain, belt sander and finished it off with a hand sander. I used the single cut for the thickness and the twist. with 3 stations. All in all total time not counting setting up the jig I have less than 2 hours in each blade. [attach=2]
I will be glad to share if anyone is interested
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Looks great!
Nice to hear it worked out for you.
I also modified my chain saw the way you did and I also placed a handle near the tip of the blade which makes it easier and more safe to guide it.
Looking forward to see your blades flying!
Max
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It will be a while before they are flying. I am starting on the mounting frame and the magnet disks next. I started with the blades first after seeing your post and the chain saw method. It was fun making them, I wish it had more blades to make! I am an R/C pilot and have made my own props on my giant scale planes. Thanks for your innovating thinking on this one. Good job