How To Make a Lenz2 turbine from recycled materials

Intro : Building a Lenz2 turbine from recycled materials

This is a short instructable showing how I built a small lenz2 turbine from recycled materials.
The Lenz turbine is a type of VAWT designed by Ed Lenz. See here for the full details. There's no generator yet, as I am converting an small induction motor to permanent magnet, this will be covered in another instructable. The turbine is 40 cm diameter and the blades are 35cm tall.

Materials :

An old oil drum
Plywood (I used 12mm, but 18mm would be much better!)
An old rear bike hub
Screws, lots of them. 10 - 12mm pan head and 25mm wood screws
Scraps of 2x6
Piece of mild steel approx 150mm x 30mm x 3mm
Washers to fit bike hub shaft, or thick sheet metal to make tour own.

First Step : Building the base and bearings

The base is made from 2x6 timber which holds the bike hub. I marked out a square piece of the 2x6 and marked the centre. Drill a hole in the centre the same size as your the middle part of your hub. Then cut the block to size and cut it in half, so that it can clamp around the bearings.

To stop the wood splitting I used a piece of mild steel as a washer under the long screws. Cut it to length and drill two holes either side. Countersink the holes, if you are using counter sunk screws. The screws I used were wood screws about 3" long.

After that I screwed two "legs" to either side. They are about a foot long. These are screwed onto a piece of plywood later on, to give the base some stability for testing.

Step 2 : Making the blade skeleton

The blades are made from the metal from the oil tin shaped around plywood cut outs with a dowel rod through the centre, to give some strength. I made a template from cardboard which I traced around to mark the plywood. You need 9 ribs like this. I cut slightly around the outside of the lines and sanded them down to the right shape using a disk sander

When you've cut and sanded the shapes out, you can drill a hole the same size as your wooden dowel. This hole should be in the centre line of the rib, and about 1.5 cm away from the curve.

Measure the useful height of the your oil drum, and cut 3 pieces of dowel to this height. By useful height, I mean the metal the will be left over after you've cut the top and bottom off the drum.

The blade shapes are screwed onto the dowel. Mark the centre of the dowels to align the central rib. With the ribs aligned you can screw them in place. Make sure you drill pilot holes for the screw in the dowels, and drill the hole in the ribs slightly larger then the screw. Countersink the holes to stop the ply splitting and don't over tighten them.

Step 3 : Cut and fit the skin for the blades

The skin of the blades is the oil drums sheet metal. You need to procure the metal from the drum by cutting the top and bottom off and cutting down the welded seam.

Once you have your metal, cut it into three pieces. You'll need to measure around the wings to get the right sizes. It's a good idea to fold the ends over so that there are no sharp edges, I didn't do this, but if you do make sure to add some extra material for that.

With the three sheets ready, I marked a line in the centre for the centre rib screws. Then I drilled holes about 30mm from the edges for the first set of screws. After those are fitted, just continue drilling and screwing the metal at 30 - 40mm intervals.

Step 4 : The central spinning arms

The centre arms are cut from the 12mm ply wood. I marked three legs at 120* apart and a centre circle of about 140mm. The arms are 40mm wide, and the ends are cut at a 9* angle.
When you've cut the shape out, you can drill a hole in the centre the same size as the shaft of the bike hub. You'll need two washers to clamp the wood to the bike shaft, I made mine out of some thick sheet metal, probably better to buy them though.

Last Step : Fitting the blades

The blades are screwed onto the arms, but first you have to cut a slot in the sheet metal. Measure and mark two lines 1.5cm from the dowel then 4 cm from there. This is to mark the width of the slot for the arms.

I used a stanley knife to cut this slot. Make sure that you cut the slots on the right side of the rib! I cut one on the wrong side... I screwed the arms onto the blades using two 1" wood screws.

It's done now! All you have to do is bolt the blade assembly onto the bike hub.
You'll see in the finished photo that it has a plywood base, I just screwed the left over ply onto the base to stabilize it.