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Forum Index : Windmills : PVC Extruded blades feedback?
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Hi Everyone Dozens of orders for the PVC extruded blades have been sent out, mostly around Australia but a few oversea's ( freight is the killer ). So I'm wondering how they are going? Who on the forum has a set up and going? I would really like to see some pictures and overall impressions. To get the ball rolling, I have a couple of mills using the blades at the moment, a dual stator F&P windmill and a hub motor ( more on that build at a later date ) based windmill. Both windmills are making about the same power. 
Phill has a set on his F&P dual stator and his new AxFx windmill based on Gordons excellent design. Regards Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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fillm Guru  Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Hi Glenn I had 50+klm winds at my place the other day and it has all been logged , I will be back home tommorow to download the data and post up some pretty good output figures for both mills .. PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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RevUpWind Regular Member  Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Glenn, have two mills up with new PVC Ex blades and very happy with them. Both x3 blades with dual stators @ 2400 dia. Have set blades both @8 degree angle and seem to do well there. Nice thing with these blades is that they are so easy to balance and put together. A real no-brainer. And the really nice thing is these blades are quiet. I like it! Have no monitoring gear but ammeter is hitting 45-50amps in good winds, that's both mills together. Am happy and just need to get myself a decent inverter. Would be good to hear from some others and what successes they have had with them. Cheers for now Peter Excuse the format, am in Goggle Chrome. ....River Heads - Australia The wind blows wherever it wishes; you hear the sound it makes, but you do not know where it comes from or where it is going. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Thanks for that Peter, I was starting to worry that no one would reply. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| okwindpower Newbie  Joined: 21/06/2009 Location: United StatesPosts: 4 |
Hello all. I guess it's about time that I posted something on here. I have been lurking in the background for too long. I have been testing the pvc extrusions now for a month or so. I really do like the concept of the extrusion, although I can see that there is an oportunity for improvement in the spar attachment. The first problem that I had was losing the "factory installed" pop rivets at 31 mph wind indicated on the test bed. This was a 5 bladed, 8 foot diameter generator. The rivets in 3 of the blades sheared off, leaving the head still in the pvc, and the shank still in the steel tubing. Blade number 4 broke off at a weldament and left the scene, with the tube still inside of it. Blad number 5 stayed on the generator. I have seen some pictures on the forum of some blades that the pvc was starting to de-form around the rivet as well. My opinion at this point is that pop rivets are not going to stand up, and the blades should be secured to the tubing with sheet metal screws. The good news is only 1 of the 5 mentioned blades suffered any damage. It must have hit the hard ground on end, and broke about 2 inches of material off the end in a jagged break. That said, the blades are performing pretty well. I have a 3 blades with an overall diameter of 94 inches set up running on a 1KW generator (radial flux) that is producing rated power in 25 to 28 mph winds. I have found that the tower loading is different with the constant chord blades compared to a tapered blade, and that the furling calculations have to be modified to work properly. If it were my decision, the next set of extrusion dies would be fabricated so to accept square tubing instead of round. This change would make mounting the blades much easier than using U bolts, and would pre set the angle of attack so that they would all be the same. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Hi Mike, good to see you here. I should mention Mike is talking about the pre-assembled blades that come with the OEM windmill he is testing. One problem Mike has discovered is OEM used 4 tiny rivets to hold the blades on, and thats not enough. It looks like 6 5mm rivets will hold up ok in strong winds, so I would say 8 5mm rivets to be the safe minium number to be sure, or as Mike suggests, steel screws. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
HI Glenn , In my opinion with the self tapping screws holding the extrusion on would not be a good idea as it is only retained in by a thin thread in very thin material and is to open to use of wrong types of screws , eg wood, also you dont know what damage is done to the screw shank as it bites into the tube , hair line fractures etc. I would also be feeling very uneasy when the wind gets up watching the blades yaw and flex as they do when they are at high speed and thinking , are the self tapping screws starting to walk out. Adequate size pop rivets and a recomended number should be the recomended standard as they are the same wether you buy them in UK , US , India etc .. To change the extrusion to a square mount system would be a massive step backwards in my opinion PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 574 |
Hi Glenn and Fillm Worring about self tapping screw or Pop rivets so what wrong with the rubber glue , silcon glue on the tube wall use during assembly and then use wide head pop rivets and also dont use thin wall stainless tube use 1.2mm thick wall as other end of the rivet (inside) has less area like red head match stick 
Dwyer the bushman |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Hi Dwyer, 1.2mm is the thickness of thin walled stainless tube , I havn't come accross any tubing thinner than this in what I have used for mounting my the blades on my hubs , if you have, can you tell me where to get it from . Glue and rivets might be a good idea if you want peace of mind ...Phill PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 574 |
Hi Phill You will find tube size on www.atlasmetals.com.au/Stainless_Steel and pop rivet with approx 14mm head & hole size is 5mm that use for plastic bumber bar on cars as cant buy from hardware shop maybe bolt and nuts or engineering shop i hope this help Dwyer |
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| okwindpower Newbie Joined: 21/06/2009 Location: United StatesPosts: 4 |
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| okwindpower Newbie Joined: 21/06/2009 Location: United StatesPosts: 4 |
Fillm, Everyone is entitled to their own opinion. Mine are not always right, but I do have 30 + years of experience in the R.E. field. I will admit that my engineering degree is in electronics, and not mechanics, but just the same, we covered a lot of mechanical in school. The reason that I am suggesting screws is because the shear strenght of a pop rivet is much less than a steel screw. The issue is not with the rivet coming out, but in shearing the aluminum shank. In regards to your comment on a major step back in going with a square tube spar, perhaps you are right. I am just thinking that if you are going to market this blade extrusion to the home builder who has limitted machining resources, that a square tube bolted to a flat plate at the hub area is going to give a much stronger and more properly aligned mount for the blade. In doing this, the angle of the blade in relation to the hub plate would be pre set, and the spar mounting would be two or more bolts through the square tube and the hub plate. This would give fairly precise location for the 120 degree spacing of a 3 blade set up, and the bolts would be under a shear load for the centrifugal force. True that round tube is stronger than square in all directions, but in this case the main load is in holding the blade perpendicular to the wind. All in all, it realy is a moot point, as the extrusion dies are already made, and it is unlikely that the mfg. is going to make a new set of dies this early in the game. I try to never post anything that could be interperated as a flame, or in strong critisism of anyone. My post was made to inform that I have seen a problem, and to alert the community to the fact. Gizmo, I forgot to mention that the testing of the blades is now being done on my own alternator, not the OEM. I don't want anyone to think that the OEM is capable of 1KW, as it is not. |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Have two mills up with extruded blades and no problems with movement on SS tubing or the 400mm root 25mm shaft. One has joined blades and has 5mm x 10mm x5 rivets with x3 tapped screws into the 25mm x 400mm root section. Other mill is as photo shows with full length blades and only three rivets. All OK so far and have had some reasonably strong winds to test them. But will certainly keep a close eye on it. Think next time have mill down with three rivets will add two more. 
On my second mill instead of making the blade shaft adjustable I tapped a screw at approximate 8' and slightly elongated the whole in blade to make small adjustments to blade angle. These three screws have small washers to add more grip to blade. Peter ....River Heads - Australia The wind blows wherever it wishes; you hear the sound it makes, but you do not know where it comes from or where it is going. |
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montyLalor Newbie Joined: 17/12/2008 Location: AustraliaPosts: 21 |
Mike, not all home builders are limited to a battery drill and a Dremel. As I work in a machine shop running CNCs I potentially have after-hours access (depending on what is currently set up, of course) to the means with which to build quite a substantial turbine. I say potentially as I'm still in the design phase of a self-feathering hub and have, as yet, only conceptualised the turbine's head design. Anyway, so what. My reply to your post is to point out two potential issues with your proposals for i) square tubing &; ii) going away from rivets as a PVC blade mounting fastener. i) Square tubing, as you correctly pointed out, is inferior in strength to round. It is also, on average, just over 20% heavier than the equivalent length in round tube. Yes, mounting it to a fixed hub would be easier, but where in this thought process is the recommended "25% of blade length should be solid bar"? I refer to the page linked here:Extruded PVC Blades Furthermore, I expect that purchasing a section of square bar that fits straight up the inside of your proposed square tube, without needing to be dressed first, would be an impossibility. Not only would size be a concern, but straightness of the square bar would certainly be a major issue. Also, I believe, from reading many posts regarding the installation of these PVC blades, that having square section 'fix' the blade's pitch angle would severely hinder the home builder's ability to adjust the pitch easily while customising their turbines to the prevailing winds and alternator loads. ii) Sheared shanks on aluminium rivets are indeed a concern. An aluminium rivet, fastened near the end of a blade on a turbine that has a blade diameter of, say, 2.5m, doing, say, 400rpm, is travelling at roughly 185km/h. And, the poor little thing has to hold a portion of the blade to the tube, all the while with its centrifugal forces trying to rip the rivet's head off. I agree with you, Mike, but not only from a shear-strength point of view. Aluminium rivets into stainless steel tube, while they both appear to be fairly benign materials from a corrosion standpoint, I believe would just be asking for trouble, in the long term. We would all be kidding ourselves if we thought that our super-duper end-caps would prevent any moisture from entering the insides of the blades over time, not to mention the tube's inner walls. Condensation is very cunning. It makes sense that rivets should only go into materials of same type: Buildex "Marson" Rivets. Therefore, I would source a supply of stainless rivets with stainless mandrels (although my searching to date for such rivets with large flange diameters has proven these are somewhat elusive). If worst comes to worst, and I cannot source large-flanged all-stainless rivets, I might see if I can use the mandrel from a standard-flanged all-stainless rivet and turning my own large-flanged rivets and subsequently test them. Or just use a stainless body washer under each standard-flanged all-stainless rivet. I also would be in favour of drilling and tapping (either M5 or M6) the section of blade that has the solid bar inside it, at the root of the blade. This would prove much stronger that any rivet (or metal screw) could hope for. It will require a stainless body-washer under the dome-top cap-screw, of course. Luke "So are you doin' this project to make us money or cost us money?" she asks again... |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Aluminium rivets are best used to join aluminium sheet etc. I would only use Monel rivets in steel. Stainless steel POP rivets if available are normally too hard. I used monel in aircon ducting and these are much stronger than aluminium. At the slightest hint of corrosion, aluminium rivets tent to lose the head end. Gordon. become more energy aware |
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Madog Newbie Joined: 27/01/2009 Location: AustraliaPosts: 25 |
Hi Gizmo, Not sure if I can help you but I have a commercial TNT freight account as I ship 50+ kg large items Nationally for good rates. If you Give me the Dimensions (Width x Length x Height)& Weight of the Wrapped/Boxed item I can get several city quotes online to see if I can help you. Den Small minds discuss people, Average minds discuss events, Great minds discuss ideas, Be GREAT ! See this Great engine with No Crankshaft: http://www.revetec.com |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Wow , the subject of rivets or screws has really lit up , I think one thing has been over looked in this debate and being maybe the only person who has had the pvc blades move under extreem conditions 700+ Rpm on 3.1Mtr Dia , the movement that occured was the PVC elongating and not the rivet , if you have a look at the picture at the bottom of my latest post "Ax Fx - & F&P Dual" (sorry cant work out hyper link ) You will notice the bulge in the PVC as the material is trying to push up under pressure , would a screw with its limited bonding surface cope or start to strip the thread , at least with a rivet it is expanded internally and the only way to remove it is to drill it or sheer it with a cold chisel. The rivet mearly acts as a dowel and weather it has a wide head or not I don't think really is the major concern , basicly it has to stay in the place it was put and stop the pvc from parting arround it so the more you put in the greater the load bearing capability will be . Also bearing in mind that we are securing basicly a flat surface to a small dia tube which only gives a very small contact area between the two mating surfaces really and has very little concern , the load face is approx 45% of the rivet circumfrence , so the bigger the better , the more the better PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I agree with Gordon that monel rivets are best in aluminium. On yacht masts they get severely tested for corrosion and do hold up very well. A thought about the great rivet debate; if I was to build a HAWT with those neat blade extrusions I would make the ss shaft long enough to protrude slightly at the end. The end would have a ss washer welded on with an outside diameter as big as the foil thickness, preventing the blade sliding further out. Rivets then only function to set the angle of attack and need not share centrifugal forces. Klaus |
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| montyLalor Newbie Joined: 17/12/2008 Location: AustraliaPosts: 21 |
Okay, I slouch corrected on the monel-v-stainless rivet material. I have not used monel rivets, but seeing as they excel on yacht masts, then they will no doubt perform well on a turbine blade. Klaus, I love your idea of using the inner tube to help the blade stay captured. I was thinking of using a length of 15-20mm of the 22mm OD solid bar, tapping, say, an M10 thread through its centre and tigging it to the end of the 1" tube, then screwing an M10 flat-top counter-sunk cap screw through the aluminium end cap I was gonna machine up. That way the whole end cap is the PVC blade's "elongation stop". The only issue I can see with this end cap mounting method is that the screw may twist the blade as it's torqued up, and if the rivets are in place first, then I might accidentally tear the PVC blade at the rivet holes via the cap screw and end cap. Something to work on... Luke "So are you doin' this project to make us money or cost us money?" she asks again... |
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| Jarbar Senior Member Joined: 03/02/2008 Location: AustraliaPosts: 225 |
Hello all, after considering all the issues that could erupt with blades and fixing thereof I came up with this solution.By drilling through the blade and spar with a 4.2mm drill I was then able to thread a plastic coated guy cable through the blades.This gives greater stability from blade to blade and stops the blade from potentially coming away from the mill hub/generator or spar.It seems to have little negative effect on efficiency or noise.And also tends to help keep blade twisted at the correct angle and with minimal weight.I am currently looking for a prettier tensioning joining arrangement similar to collet fixings used on balustrade. 
"Creativity is detirmined by the way you hold your tounge".My Father "Your generation will have to correct the problems made by mine".My Grandfather. |
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