Introduction: $30 Vertical Axis Wind Turbine From Scrap Materials
This is a Vertical Axis Wind Turbine which uses wind energy to drive things like air and water pumps for cooling, irrigation and similar, or an alternator/generator for producing electricity.
Note: this tutorial is also available at http://solarflower.org/tutorial.php?lang=en&tut=vawt with a slightly more usable layout.
The turbine uses the 35-40% mechanically efficient Lenz2 lift+drag design. It is made entirely from scrap materials except for the bolts and pop rivets, and should cost about $15-$30 for the six vane version, which can be made by two people in six hours without much effort.
The three vane version has been successfully survival tested to 80 km/h sustained winds and the six vane version to 105 km. Both will do more, but exactly how much has not yet been ascertained.
Full power curves have yet to be calculated for this particular build, but according to Mr Ed Lenz's calculator (http://windstuff.org/calc/calc.php) a six vane at 0.93 meters diameter and 1.1 meters high with a 90% efficient alternator should produce at least 135 watts of electricity in a 30 km/h wind, and 1.05 kilowatts at 60 km/h.
The materials listed in this tutorial are to make the three vane version. Double everything except the bike wheel for six vanes.
Step 1: Tools and Materials
4mm metal drill bit
Craft knife / scalpel / exacto
20mm x 20mm angle aluminium
About 1 meter long, an extra ~30cm length can also be handy. To be used for ruling and bending.
Probably 7mm, 15mm and 17mm - to fit your M4 nuts and the nuts on the bike wheel axle
Bike Cone Spanner
4 Clothes Pegs
Springy or the other kind.
A small bit of wood
For drilling into.
Computer and printer
Low quality black and white is fine.
2 pieces A4 paper
12 Aluminium lithographic offset printing plates
These are pure aluminium sheets used in a printing process fairly common with newspapers and magazines. A medium sized printing company may scrap hundreds of plates every week, so it's usually easy to pick them up cheap. Ring around any local companies offering offset printing.
This tutorial is for plates which are 67cm wide by 56cm tall. There doesn't really seem to be any size in particular which is standard, if you can only get plates which are larger than 67cm then either scale up the measurements (though that is the size which best fits a 27 inch bike wheel, which is generally the largest you can get) or trim the plates down to that size. If you can only get smaller than scale the design down and use a smaller wheel.
The 56cm length really doesn't matter at all. The taller the vanes the more energy you'll get. The relevant steps in the tutorial will tell you how to accommodate other lengths.
126 4mm diameter pop rivets
About 5mm long.
18 M4 bolts and nuts
About 15-20mm long
18 spring washers
To fit the M4 bolts
4mm inner diameter to fit the pop rivets, about 10-15mm outer
27 inch bike wheel
Exactly how bike wheels are measured is slightly complicated, basically you want one which is 64cm total outer rim diameter. You can use other sizes for smaller turbines, adjust the other dimensions accordingly.
It doesn't matter if it's a bit rusty but needs to run smoothly and not wobble. You don't need the tire or inner tube.
6 bike wheel spokes
Any length. Some kind of thickish wire or similar would also suffice.
Step 2: Construction Steps
These steps relate to the construction animation. You might want to open this in a new window to make it easier to cross-reference with the steps text.
Download (right click, 'save as') and print the two template files onto A4 paper:
Make sure they're printed at 100% and centered, the images should be 21cm by 29.7cm at 40 dpi. You may get a warning that the image is larger than the printable area of the page, you can ignore that. When printed measure the distance between the + marks, it should be 10cm on both pages.
Tape the pages together so that the + registration and circular marks overlap as closely as possible. Best way to do this is on a window pane during the day, so you can see both pages showing through.
With a craft knife and the angle aluminium as a straight edge, cut the surrounding paper off the template.
Any time you're cutting, always make sure your other hand is never in front of the knife, so if you slip you're not going to slice yourself. The angle aluminium is good for this, as the vertical bit effectively shields the hand holding it.
Take an aluminium sheet and measure a box 43cm by 48cm. Score the lines with the craftknife and straight edge. You're not trying to cut through the metal, just create a line that can then be torn out later. A good method is to score once lightly, then a second time a bit deeper.
Draw a line 24cm up the long side, halving it.
Flex the metal so that it bends at a score line, then flex back the other way. Do this a couple times and it should split. Do the same for the other score and remove the outer metal. Keep it for later.
Tape the template to the metal (from now on to be referred to as a 'former') so that the long edge of the paper sits on the middle line and the right edges of both line up. Don't worry if the other edges don't align perfectly.
With blade and straight edge, score out the template curve, including the triangles at each end. It's not essential that this be 100% perfect, but try to get the first one reasonably nice as you can then use it as a template for the rest.
Score, flex, and remove the two triangles of metal outside the template.
Flip the paper template over so that the printed side is down on the other half of the former, keeping the long edge on the middle line. Retape so it doesn't shift too much. Check that you can see the circular marks through the paper. If you can't then punch small holes or similar so that those marks can be seen from the back.
Give the curved score a couple of flexes and tear it out. Remove the two small triangles. A video on how best to do this will be posted here soon.
You now have your first former. Repeat steps 3 through 7 so that you have a total of 6 formers. You can use the first former as a cutting template rather than the paper.
Take 3 formers and peg them together so that they are as nicely aligned as possible.
Use tape to attach them if you don't have clothes pegs.
Drill 13 4mm holes through all three formers, one for each of the circular marks on the template. Drill the center hole first, as this is the only one that needs to be reasonably accurate.
Remove the template and unpeg the formers. Peg and drill 3 more formers so that all 6 are drilled.
Place a former with the middle line slightly overhanging the edge of the table. Place the straight edge on the middle line and bend 90 degrees. Repeat with all 6, with three formers bent up and 3 bent down. A video of this will be posted here soon.
Put the formers aside.
Take a aluminium sheet and draw a line 2cm in from one of the 67cm edges.
repeat with 2 more sheets and peg all 3 together so that each drawn line is aligned to the edge of the sheet above it.
Mark the edge at 4cm, 6, 8, 10, 18, 26, 34, and then every 2cm up to and including 64cm.
Score at each mark, starting from the drawn line on the top sheet and across all 3 sheets. Keep in mind that one side has a score at 4cm from the edge, the other at 3cm.
Flip the sheets over, making sure they don't lose their alignment, draw another line 2cm in from the edge of the now top sheet.
Mark and score the same as the first edge. Make sure you start from the 4cm edge.
Tap the sheets on the table so that they are aligned on top of each other.
From the 4cm edge draw a vertical line at 19cm in, and one at 33cm.
Mark each line at 3cm and 18cm from both ends. If you're using sheets which aren't 56cm tall then mark at 3cm and divide the rest into thirds. ie if the sheet is 75cm tall then mark from each end at 3cm and 23cm. The 3cm marks need to be at least vaguely accurate, the others don't hugely matter.
Drill all 3 sheets with 4mm holes at all 8 marks.
Unpeg the sheets.
Place a sheet so that the 3cm edge is overhanging the table. Put the straight edge on the 3cm mark (if you can't make out the score marks then mark them with pen) and triangulate the edge as shown in the animation. Video coming soon.
Triangulate the 4cm edge.
Pre-bend the sheet so that it'll be easier to place in the formers.
Flip the sheet upright and insert into the curve cut into a top former (the uncut half of the former should be pointing upwards).
The best way to do this is to first place the 4cm edge triangle into its slot, then the 3cm edge, then work the rest of the sheet through the cut.
Fold down the flaps as shown in the animation. You will probably need to give the score marks a couple of flexes before tearing them.
Push up the former so that it's level with the bent flaps.
Fold over the rest of the former.
Flip the vane, place the other former, and fold down the tabs. Place 2 bike spokes or thick wire in the fold of the former and bend it closed.
Slice and remove the former's two outer corners. Cut the smaller triangle level with the edge of the other former half, but give the larger triangle a 2cm offset, so that it overlaps.
Repeat for the other former.
Take one of the offcuts left over from cutting a former. Cut out a strip which is 7cm wide and 52cm long. (This is assuming you're using a 56cm sheet, for any other size just cut off 4cm. ie For a 75cm sheet cut the strip to 71cm).
Draw lines from one edge at 2cm and 4cm, so that there are two 2cm strips and one 3cm strip.
Triangulate the strip as shown in the animation.
Mark the middle of the ends of the 3cm wide face with lines a couple of centimeters long.
Place the triangulated strut inside the vane so that the 3cm face sits on the row of drilled holes closer to the back edge. Sight the drawn lines through the top and bottom holes to check that it's centered.
Drill the strut through the holes in the vane and attach with rivets. Do the top and bottom holes first, then the two in the middle.
Take a fresh sheet and cut in half. (This is assuming a 67cm wide sheet, for any other size just cut at 33.5cm).
Remove 4cm from one of the short edges.
Repeat twice more so that you have three 33.5cm sheets. Align and peg all three together.
From one of the long edges, draw three vertical lines at 1cm, 9cm, and 19cm.
Mark these lines in from both ends at 1cm and 17cm. If you're using other than 56cm high sheets then just mark so that the lines are divided into thirds, more or less.
Drill a 4mm hole at each of the twelve marks.
Mark the sheet at 3cm and 5cm in from the opposite edge.
Triangulate the edge as shown.
Place the half sheet inside the vane so that its un-triangulated edge is aligned with the vane's back tip.
Drill and rivet the row of holes closest to the back edge. Keep the half sheet as flat and unbuckled as possible. It's ok to have a small gap or bowl at either end if it doesn't fit perfectly in the vane.
Stand the vane upright. Push the half sheet's triangulated edge in and forward so that it's against the other sheet and somewhat tight over the strut.
Drill through the row of holes on which the triangle is sitting and rivet in place.
Drill through one of the middle holes in the half sheet's second row, making sure to keep the drill reasonably straight, and attach with a rivet and washer, so that the washer is on the inside of the vane.
Repeat for the other three holes.
Drill, rivet and washer the third row. The half sheet should be fairly tight across the strut.
Fold up the overlap on both formers to 90 degrees.
Drill through all the holes on the bottom former (the one which will be attached to the bike wheel). Drill into a small block of wood or similar so that the metal doesn't get pushed in and so that you don't risk drilling your hand.
Rivet each of the holes, except for the ones marked as in the animation, as these will be bolted to the wheel rim.
Drill the holes in the top former and rivet all except the center one.
Take your bike wheel. You may want to give the inside of the hub a clean, in which case use spanners to remove the axle from the hub and wipe everything down with paper tissue or similar. Be careful not to lose any ball bearings.
Set the nuts so that as much length of axle as possible is on one side of the wheel (away from the sprockets if your wheel has them) and retighten so that the wheel runs smoothly and doesn't wobble. There are various videos on Youtube on how to do all this.
Drill three 4mm holes evenly spaced around the the rim, as close to the edge as possible. Your wheel should have 36 spokes, so drill a hole every 12 spokes.
Poke an M4 bolt up through one of the holes and through the backmost unriveted hole in the bottom former of the vane. You may need to poke the former's bike spoke out of the way, make sure it's on the outside of the bolt.
Place a washer, a spring washer, and a nut. Don't fully tighten yet.
Align the vane so that the other two unriveted holes sit on the edge of the wheel rim and mark with a pen through the hole.
Rotate the vane away so that you can drill the two marks.
Move the vane back and lock down with bolts, washers, spring washers, and nuts. Fully tighten all three.
You may need to drill out a part of the rim to allow the head of the bolt to sit close. If the bolt is poking out to much it may hit on the chain you'll probably be using to drive your application.
Assemble two more vanes from your remaining formers and sheets and attach them to the wheel.
Take another sheet offcut and slice out a strip 9.5cm wide and 67cm long.
Mark with lines so that you have widths of 3.5cm, 2cm, 3cm, and 1cm. Mark the 1cm width on both sides.
Flip the strip over and bend the 1cm width to 45 degrees. Flip back and triangulate as shown.
Drill a 4mm hole 8mm in from each end of the strut on the 1cm flat area. Drill and rivet a hole at the midpoint.
Repeat twice more so you have three struts.
Place an M4 bolt up through the unriveted center hole in the top of one of the vanes, and through the end holes in two of the struts. Add a washer, spring washer, and nut.
Repeat with the other two vanes and the last strut. Lock all tight.
The top of the vanes need to not be twisted relative to their base. Place the turbine on the ground so you can look down on it, stand over one of the vanes so that you can see the long edge of both formers. Twist the top former so that it lines up with the bottom one, over correct a degree or two as it will slip back.
Drill a hole through one of the struts and the former 1-2cm from the edge. Add bolt, washer, spring washer, and nut. Recheck the alignment, drill the other strut and nut bolt etc. Tighten all three.
Repeat for for the other two vanes.
Optionally, you can add an extra three vanes to the underside of the wheel.
Step 3: Mounting and Applications
This section will be added to as I do some more pre-vis animations and videos on potential uses for the turbine, but there are essentially two main ways to attach a pump/alternator/whatever else you want.
For low to medium rpm applications:
Run a bike chain from the sprocket set of the turbine's wheel to a sprocket on the application. As in:
The good thing about this setup is you can set your gearing anywhere between about 2.5:1 up to the same down. The bad thing is that if you're using a six vane turbine your application will need to sit inside the whole thing as you won't be able to take a chain out through the spin radius.
For high rpm applications:
I'm in the process of doing up a quick animation to demonstrate this, but basically you put the chain (or rather two chains attached and trimmed for length) around the bike wheel rim itself, effectively using it as a large sprocket. It engages surprisingly well, and gives a ratio of about 12:1 with a small sprocket on your application.
This is necessary for things like car alternators, which require about 12,000 to 15,000 rpm to start. The good thing about them being that the voltage regulation and charge control is built in, so you can just attach directly to your 12v battery.