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Forum Index : Windmills : Old Dunlite generator blades
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Darren Newbie  Joined: 13/07/2008 Location: AustraliaPosts: 20 |
Hi Guys Iam rebuilding a old Dunlite 2kw generator geared 5 to 1 with variable pitch. I need to make new blades and was wondering if I could use the PVC blades on this site or the Aiuminum blades people are using. This machine is governed to 200RPM buy variable pitch blades and they are 72" long standard. Iam concerned that new design blades are for higher RPM. Thanks Darren |
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| KarlJ Guru  Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
add pitch! they will run fine at lower speed more torque same power. blade TSR's For what my opinion is worth..... with 12degree pitch they will run much slower. we run them at 8-9 degrees as the turbines we build (F&P and AXFX) with diameters ~10' need the 500rpm to make good power. Thus I would say they would be OK. Loose the variable pitch and make the generator furl bny offsetting from the tower and a pivoting tail. Luck favours the well prepared |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
It think Karl is correct, but may not understand the gererator in question here. This generator i well suspect flew in the open air when many of us still wet our pants and the rest still wore short pants to school. I would say try to stick with the original variable pitch system as no doubt it has already seen many of testing winds and has lasted this long. You may well need to replace the dampner shocks to get correct pitch operation. I see no reason why the pvc or ally blades wont work and would think it might be a little trial and error with blade length to get the correct balance of rpm/torque. Pete. Sometimes it just works |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
You have the luxury of variable pitch, so matching is done for you for the most part. The plastic and aluminum blades will suite this application fairly well, as would most lift blades... but.. Personally I would worry about mounting 72" of them, as they have only a 25mm bore, and I believe both plastic and Al need support all the way up.... maybe alone here... this would be a bit iffy I think. If you wish, you can make the original ones using this technique from this web site:making dunlite blades More information can be found here Or chainsaw a set up from the drawings they have there. Should be very quick and simple... ..........oztules Village idiot...or... just another hack out of his depth |
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| Darren Newbie Joined: 13/07/2008 Location: AustraliaPosts: 20 |
Thanks Guys for the input, I'm in the process of reconditioning the varialbe hub I realy like to keep that working. The whole system seems very well made for their time of production. Iam reconditioning the damper shocks not much in them so easy to fix. Oztules were you trying to say not to go the full 72" long? I was thinking longer was better with the variable pitch should not see the same extreem loading as fixed pitch. I also chasing information on the bob weights I dont have them at all and need to make some. Thanks Darren |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
With variable pitch, I would be inclined to go long rather than short. Excellent profile for this application I think, Phil will be in a better position to sensibly answer the loading questions.. but for me ... I worry... probably too much. 25mm is not a lot to work with.... but would make an easy conversion. ..........oztules Village idiot...or... just another hack out of his depth |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Hi Darren , I tend to agree with Oz on this one , I would be keeping it as close to the origional design as possible even going so far to shoot myself in the foot and recomend you try to copy the origional blade design . How the aluminium GE222 airfoil will do in this situation I do not know , a few weeks back I played around with seeing how much power I could get at low RPMs by having both stators on my dual in star and loading it heavily between 100~200Rpm , @ 8deg AOA it was quite dismal so I went to 12deg AOA which was a bit better but not as good as allowing the second stator to cut in at 200~240Rpm . If you were to try the Al Blades then I would be going to the origional Dia 72" = 3.6mtr . How to attach them to the origional variable hub shafts with out seeing photos or one in front of me I could not comment on , but with out seeing close up I would be thinking of a solid machined steel adapter . Also knowing which way the variable pitch mechanism reacts to maintain 200rpm would be a point to know . I would imagine it would be at maximum pitch and turn the blades towards 0 to neg AOA . As for the blades strength @ a maxium of 200rpm , I would not think this would be off major concern at that dia or even bigger with the Aluminium blades . As I have said previous if it was me I would be putting it back to the origional design if at all possible, its been tried and tested and works , if you go down the path of modifying you could end up with something that doesn't work as it was origionally designed to do . If there is anything I can help you with then drop me an email through the link in "kits & Parts " PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
All feathering mechanisms work by driving the leading edge to face the incoming wind, thus increasing the AoA beyond stalling angle, obviously driven to the extreme they are flat with the wind rather than normal where they are almost flat against the wind. They will still windmill.... pardon the pun! Aircraft propellors hate running in feather and when we do feathering checks during maintenance, we shut down the engine at the same time and use wooden batts to pull them back. (some props like free turbine engines will run in feather but the free turbine is heavily loaded and if done for long periods can damage them. Luck favours the well prepared |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
Yeikes, read the article on making the steel blades. I'd be using the ALuminium profile over that idea any day of the week, will be light years ahead in performance. make them 60" long and use a blade extension of sorts off the original stubs Luck favours the well prepared |
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| Darren Newbie Joined: 13/07/2008 Location: AustraliaPosts: 20 |
Thanks Guys for all the information at the moment I think i will go with the aluminium blades. I agree that they should be many years ahead in performance. If they dont work well on this dunlite then I will have to use them on something else. Thanks Darren |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
Dont mean to rain on Phills parade, him shooting himself in the foot and all but if the thing only runs at 200 rpm there will be no problem whatsoever with the 1" shaft, it was only the 1000RPM scenario where "unobtanium" was required to keep it together, at only 200rpm 72" blades should last the distance. at 2m each blade its really only 500mm longer than what is tried and tested at 750rpm (in PVC) so should survive 400rpm no worries. for 200rpm you have plenty of life left in the materials and long term survival would be no problem. Good sound decision even if 'tules would have preferred you break out the chainsaw! Luck favours the well prepared |
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