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If you have access to a laser or water jet cutter, you could use the zipped up DXF file below to cut a hub similar to mine shown above. PVC_extrusion_hub_Smartdrive.zip The dxf file contains the parts below, designed to fit the Smartdrive drive shaft. These should be cut from 6mm mild steel. If you dont have a Smartdrive you can replace the spline with a hole to suit your alternator.
The file also includes a offset plate shown below. Using this plate will offset the blade to the centerline, purely for cosmetic reasons, and will actually reduce the chord swept area near the turbine center so may reduce power slightly.
Click below to see a YouTube video of the PVC blades in action.
Looking for a nose cone?
Trevor has blank fibreglass nose cones for only $30AU.
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Whether you looking for a easy to build turbine, or a airfoil to experiment with, then these cheap PVC extrusions could be what you're looking for. They are available from forum member Anthony ( Jarbar ) and can be ordered below.
These blades were designed as a easy to use general all rounder windmill blade. They are based on the GOE222 airfoil, which has a proven record in wind turbines and has been used by the Windcharger wind turbines for many decades. The profile works well over a wide range of attack angles, meaning the blade has a wide power band compared to other high speed profiles. This also means the blades can be used with no twist[1]. The blades are silent in operation.
To use these extruded blades, you need to slide in a length of 25mm[2] ( 1inch ) pipe at least 80% the length of the blade. This gives the blade its strength and makes it easy to mount the blade to the hub. It also means its easy to adjust the blades angle off attack. You can use common exhaust tube for this[3]. Once in place the PVC extrusion can be pop riveted to the tube. For turbines over 3 meters in diameter, the minimum recommended number of rivets is 8 ( 4 per side ), and for turbines under 3 meters, at least 6 ( 3 per side ) rivets should be used. The rivets should have a shank ( to suit hole ) of 5mm. Stanless rivets should be used. The blades work best with a angle off attack between 8o and 10o. The angle is taken from the blades centerline ( 0o ). Note there is a 3.2o difference between the blades centerline and the bottom surface ( the side that faces the wind ). So if you want a 10o angle of attack, rotate the blade to read 13.2o from the bottom surface.
The blade will also need more strength towards the turbines center, where blade loading is at its maximum. So you need to slide a length of 22mm steel rod into the exhaust tube, for at least the first 25% of the blade. The exhaust tube and rod should be plug welded in several places to keep them together. See below. The inner shaft should have a radiused end, and the plug welds should be no closer than 50mm from the inner shafts end, and plug welds should be offset from eachother ( dont plug weld directly opposite another weld ). We recommend you do NOT use aluminium tube.
The blades come fitted with the end caps, so you need to specify the direction of your turbine rotation, either clockwise or counter clockwise, looking at the turbine face on. If you wish Anthony can leave the end caps off and just include them with the delivery, however he still needs to know which way the turbine spins so he can supply the correct end caps. In reality, with these blades, the direction of rotation is not important. However from a cosmetic point of view, if you have more than one windmill, it looks much better if all turbines rotate in the same direction. Windmills rotating in opposite directions looks weird. Additional end caps are available on request. The end caps are there to keep water out and stop the extrusion ends whistling as the turbine rotates. Early prototype end caps had a small wing let included in the mould, the current end caps do not. However they are a better fit to the PVC extrusion and you can easily attach a wing let made from plastic to the end cap if you want to experiment. Where possible, Anthony will use the postal service to send the blades. Post is much less expensive than courier, but limits the max blade length to 1m. So if possible, keep your blade length to 1 meter or less. If you want a longer blade, you have two options.
Because the blades use the steel tube for strength, its possible to join shorter lengths of blade together to make a longer blade. If you wanted 3 blades at 1.5m long, you could order 3 at 1m and 3 at 0.5m, and save a lot of money on the delivery. If you wish to inquire about ordering a set of the extruded PVC blades, please fill in the form below. Anthony will calculate the total cost and send you an email with his payment details and asking you to confirm your order and delivery address. Please allow a day or two ( longer for weekends ) for the return email. 1. There would be some small gains in twisting the blades. The PVC could be heated and twisted around the pipe, though this is something the buyer would need to experiment with. 2. The blades will "squash" down to 22mm easily, though there may be some bulging between rivets. 3. Stainless steel would be a better choice if you can source it. Also check it has a wall thickness of 1.6mm, to allow the 22mm rod to fit up the middle. 4. Lengths up to 3 meters are available, but going over 1 meters means we cant use the postal service to delivery the blade. |
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