Over the past six months I have been working with four local KW (Kid Wind) teams and their coaches to prepare for the up coming National KW Challenge that will be held at the 2018 AWEA (American Wind Energy Association) conference in Chicago, IL on May 8 - 10. In the process I have used the stock KW equipment. This equipment is high quality and well designed to be used in the classroom with all levels of students. Simple and straight to the point. Gets the job done. No muss no fuss.
We started out learning the basics. Designing, building and testing flat blades in the one foot long range with 8:1 gear ratios. Three of the teams performed at a level high enough to be invited to compete in the National KW Challenge. The national level of competition would require a higher level of performance and we are rising to the challenge. Their first turbines were producing 20 Joules of energy and now they are producing 60 J !
In the spirit of learning and promoting KW and RE education here are some of the changes I have made to the original KW equipment that have helped the teams.
Use of 1/4" fiberglass rods for blade spars with 3 locking ring grooves for the first 6" of blade. Eliminated the problem with crushing of wooden dowels and blades not held in place.
Drilled and threaded 6 of the 12 holes in the hubs then fitted them with 6-32 threaded 5/8" long socket head screws. Provided extreme grip and holding of pitch angle set on 23" long blades.
Ground two flats on main shaft hub mount so that it can be held with a 9/16" wrench. This allowed the hub mount to be held while the hub screws were bring loosened/tightened. Also replaced the small Phillips head screw with a 6-32 socket head screw. This provided a much easier and more positive method of holding the hub in place.
Installed 5/16" O.D. brass tubing to run and support the main shaft in. Also drilled and installed a second brass tube with a 9/64 ball end driver for the second gear shaft. This allowed for building a 32:1 gear ratio. It did require the cutting of the bottom of the nacelle so that the KW generator could be mounted below as shown in the photo.
This shows a close-up of the cut that has to be made to allow the generator mounting piece to fit tight.
It will also be necessary to reduce the thickness of the 1/4 nuts to 1/8" thickness.
Grease holes were drilled in both ends of all brass tubing. The needle on a 5ml livestock syringe was ground off and silicone grease used to reduce friction on rotating shafts.
Replaced small Phillips head screws with 6 - 32 socket head screw to prevent yaw movement of nacelle during testing in wind tunnel.
Designed a hot wire cutter run by a 12 volt battery charger to cut air foil blade shape out of 1" styrofoam. This air foil shape is then sliced into 1.25" pieces and then re-assembled with a twist as shown in the photo above.
Designed the two rod system that allows you to make a twist that goes from a 45 degree pitch at the root to a 0 degree pitch at the tip of the blade. This photo shows the pieces hot glued back together with the twist. After the spar is glued in the rough edges of the air foil are sanded smooth and covered with iron on plastic lamination material.
Designed a blade pitch setting tool that can be used to set multiple blades to the same pitch using an adjustable depth screw. This is done while the blades are mounted to the hub on the nacelle. Also this allows the 6-32 socket screws to be loosened so that a 2nd, 3rd ... pitch can be made and tested at various wind velocities. The plate is only for testing and data performance collecting. The plate is removed for competition.
Designed and made Nacelle Assemble Stand. This allows students to secure their nacelle to the block and use two hands to place gears and shafts. Check clearance and fit of gears when building up a gear train and adjusting the KW generator to mesh with the gears. The vee groove supports a gear or gear plug when removing a shaft. There is also a 3/32" brass punch and large nut to be used as a hammer if needed. Try putting this all together without this stand and you will appreciate what it does!
So there you have it. I believe in sharing this to promote learning and the KW program. There is more than just watts in the power we are producing. I have all the pictures and details that go along with these changes to the equipment. Email me if you need or want more information or I can be of any help. Hope to see you at the National KW Challenge.
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