To design and make a wind powered generator in the most efficient manner. The energy generated by the device will be determined by measuring the highest power output available from the generator as measured by the product of the generator's voltage and current.
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Step 1: Transmission - Step 1 - Materials
Materials and components
2 4mm steel rod
4 6mm threaded steel rod
54 6M nuts
3mm clear sheet acrylic (perspex)
Bought in gears 60,10,50,40 teeth
1 Electric Motor
40W Laser cutting machine
Allen Key (came with gears)
Step 2: Transmission - Step 2 - Laser Cutting
For the transmission, we need something to keep it all together. We chose to use Perspex as it is strong rigid, easy to cut and viewers of our turbine will be able to view the inner workings of it easily as it is transparent.
3 rectangles of perspex were cut using the laser cutter
- All contain 4 6mm holes at each corner and 2 4mm holes in the centre and centre top
- A large hole was made for the motor on 2 of the rectangles, size varies with motors but ours was about 35mm in diameter
The spacing of the holes was measured using the radius of the gears used.
Step 3: Transmission - Step 3 - Metal Cutting
Using a hack saw we cut:
- 4 6mm steel thread rod to approximately 250mm long (we ground down the tips so they were neat and nuts screw easily on to them)
- 2 4mm plain steel rod 300mm and 100mm
Step 4: Transmission - Step 4 - Assembly
All 3 perspex rectangles were placed 25mm – 30mm parallel to one another, the one without the large hole at the front. The small holes at the top, big hole for motor at the bottom. The threaded rod went through the holes in each corner, the motor through the 2 big holes. The small 4mm rod through the 4mm holes, the longer one through the top (filed if necessary)
Double nuts were used on the threaded rod to keep it all together.
The 40T gear was attached to the motor, the 50T gear meshes with that on the smaller 4mm rod. On the same rod is a 10T gear that meshes with the 60T gear on the longer rod, to which the blades will be attached to.
Note: Washers were used to stabilise gears after testing.
Step 5: Housing - Step 1 - Materials
Wood – mdf, plywood, pine
3mm clear sheet acrylic (perspex)
White emulsion paint
3mm screws (counter sunk heads)
Plastic bender (hot wire)
Step 6: Housing - Step 2 - Spine
The spine is the point where the transmission and housing are linked together.
It was made by sawing a rectangle of 15mm plywood to the correct dimensions
Then we drilled 6mm holes lining up from where the 6mm threaded rod sticks out from the transmission, making it so the top of the plywood is parallel and flush with the top of the perspex.
A 30mm hole was made at the centre to thread through wires from the motor.
A block of wood was drilled and screwed to the back to stand it up at an angle of 5°
Step 7: Housing - Step 3 Â Side Walls
The side wall design was mainly thought out due to aesthetic reasons and the bird or leaf like shape was a recurring design with most of our prototypes.
The top side was measured to be the same length as the plywood and perspex transmission the side perpendicular to that the same depth of the transmission the other lengths were calculated so they hid the rest of the transmission and inner parts.
The sides were the drilled and screwed on to the spine. The drilled holes were then counter sunk.
Step 8: Housing - Step 4 - Perspex Cover and Finish
A perspex rectangle was cut to size using the bandsaw and then bent around the top of the sides and spine using a hot wire, to create a neat cover.
Holes were drilled and countersunk into the perspex to secure it to the housing wood.
A small piece of pine wood was screwed as a support at the back to keep the sides from bending in.
The whole housing was then painted with 3coats of white emulsion and sanded between each coat to create a smooth finish.
Step 9: Blades - Step 1 - Materials
3 & 4mm pine dowel
4 6mm bolts
4 6M nuts
Step 10: Blades - Step 2 - Sketch Out Aerofoils
We researched the most common aerofoil used for 3 blade wind turbines and the one that kept popping up was the SG6040, http://www.worldofkrauss.com/foils/3.
It has Max L/D of 50.557, and coefficient of lift of 1.495, however as our wind generator is small we did not want something too powerful.
This image was copied using layout paper and scaled it down from 70mm long, to 60mm and 50mm long, so that the blade would have a slight point to it.
Using the image copies for each of the 3 scales, a template was made and copied on to MDF 4 times.
Foils were cut on a bandsaw then sanded down using a sanding machine to give the winglike shape.
Step 11: Blades - Step 3 - Making the Skeleton
For each blade 3 aerofoils are used (one blade made as a spare)
Drill holes for dowel, the one nearest to the head of the aerofoil 4mm and the one nearest the tail 3mm, angle the holes at each scale to be 2.5º below the last to make an overall angle of lean of 5º.
In the biggest aerofoils (70mm) a 6mm hole was drilled for bolts
The dowel was fed through the holes of the aerofoils, making each blade 150mm long, centring the middle aerofoil at 75mm.
Excess dowel was trimmed off using a craft knife or scalpel.
Some dowel was cut in half and hot glued between the tails to give shape for the silk.
Screw the bolt into the skeleton, the head of the bolt inside the blades.
Step 12: Blades - Step 4 - Covering and Doping
Silk was then cut to the shape of one side of the blades, but slightly bigger. It was then made damp just using water and squeezing out the excess water.
Cellulose dope was painted on to the wooded edges of the the blade then silk was then stretched over the blades.
Pins were used to keep the silk stretched and in place. With time the dope dried and stuck the silk to the wood.
The same process was repeated for the other side of the blade and for the other blades.
Step 13: Blades - Step 5 - General Doping and Tweaks
Then a coating of dope was painted on all of the dry silk (avoiding already doped edges). This tightens the silk on to the skeleton and creates a smooth, waterproof coating for the blades.
Leave to dry and the blades are ready to use.
Trim off excess silk for improved aerodynamics.
Add a nut to the end of each bolt for more security.
Step 14: Hub
Wood (perhaps oak )
Pair of Compasses
The hub is a perfect hexagon prism it is 40mm in diameter made out of wood.
An easy way to make a good hexagon is using http://www.wikihow.com/Draw-a-Hexagon.
The hub 30mm in depth and on each side there is a 5.5mm hole, so the 6mm bolt in the blades fits tightly in to it.
In the middle of the hub was a 4mm hole for the drive shaft to fit snuggly on to.
It was cut using a bandsaw and shaped to the correct shape using a sander.
Step 15: Final Assembly
The blades screw tightly on to the hub, and the hub squeezed neatly on to the driveshaft of the transmission.
The threaded rods of the transmission then slid onto the spine.
Secured the transmission with double nuts on each rod and wired up the motor and the wind generator is ready to go!