(last updated: 10.4.99)

Description of the Rotor

Some time ago a totally new rotor could be seen at a kite festival in Berlin, all the spectators were very interested.
Its inventor and constructor is Hermann Aurich. The speciality of this Rotor is that it its idea, shape and function was taken from the machines used to produce power from water, or from the jets of an airplane.
The first versions still were doubble rings with its vanes between them and they were open in the middle. With unsufficiant wind they collapsed and had to be opened again manually.

The newer version, as the one we will build here (a slightly altered Aurich Rotor) consists of three concentric rotor units. The outer unit has 18 vanes (between the outer wall and the first partition wall), the middle unit 12 (between the first and the second partition walls) and the inner unit 6 vanes (between the second partition wall and the centre of the rotor).
All the partition walls are conic, the entrance for the air is bigger than the exit, this gives the Rotor the stable shape.

The presented Rotor has a diameter of about 80 cm, turns with a speed of about 40 up to 250 turns per minute (depending on the windspeed) and pulls quite heavely. Even if the wind stops and the rotor collapses, no problem, when the wind starts again, the rotor will get its shape automatically and will turn again.

Source of the construction Plan:

The size and the construction steps are taken from a dutch construction plan, also available on the Internet. This plan is something like a translation into english (and german). The dutch construction plan is a slightly altered plan vom the original Aurich Rotor as published in 'Vlieger' year 1992 Number 3.
Use this plan only for personal building, not commercial.

List of material

- about 2 square meter ripstop Nylon/Spinaker, also remnant from previous constructions are usable, feel free to use different colors (see also colors)
- cardboard for the stencils (I really recommend them, as you have to cut quite a lot of pieces)
- 2.6 m dacron for the enforcments
- a good turning piece which turns with ball bearing
- depending on the type of bridling between 10m and 16m flying line (single line kite line of about 50 Kg)

Size of the pieces and cutting them

It's worth to create a stencil made from cardboard or something similar, you have to build more than one of each piece.
Additional fabric is already counted in the measures at the edge C-C (about 7mm, it works also with less) and at the edge A-A (about 3 to 4 mm, not especially marked). If you want to hem everything you need to add your favorite hemsize (Be careful: not everywhere hem is needed).
I recommend to cut the pieces hot. This saves a lot of work.
The measures on the layout are in milimeters.

Piece 1 needs to be cut 18 times. This piece builds the outmost layer of the Rotor (Outmost wall and 1st set of shovels):

Piece 2 is needed 12 times. This pieces will build the middle unit ( 1st interior wall and 2nd set of shovels).
Piece 3 is needed 6 times. This pieces will build the innermost unit (2nd interior wall and 3rd set of shovels).


Choosing the colors

Feel free to choose whatever color(s) you want, the only thing you probably have to think of that one sector of the rotor is built by one innermost part, two middle parts and three outmost parts.
My rotor is built with one sector in red, the rest is white. This way one can see the pitch rate very well.

Other possibilities are to work with 2, 3 or 6 different colors:

Putting the pieces together

The area between A-A-B-B builds a part of the walls (outside/inside walls), the area between B-B-C-C builds the shovels.
All the sewing work should be done rather exact to get a even turning rotor in the end.

building the chains:
Let's start with sewing the outmost ring from the 18 pieces of Part 1 together. This is done by sewing edge A-A from the following piece onto edge B-B from the previous piece. In this way we connect all the 18 pieces together. It is important that all the shovels (area B-B-C-C) are looking onto the same side, easiest if they look to the backside as shown in the layout below. This chain will not be closed now, this will follow later, as the last step.

I recommend to put the following piece topside down onto the previous and sew them together. After folding the following piece over, the seam is inside. The layout below shows this again:

To build the chain for the middle rotor unit we do the same as mentioned above with the twelve pieces of part 2, again without closing the chain. Again: very important is that all the shovels look to the same side, the same as the shovels in the chain of part 1.

Now again the same with the 6 pieces of part 3: I do not repeat that it is important to .......

After that we have three chains, one of 18 pieces, one of 12 pieces and one of 6 pieces. Then next step is now to connect the three chains together. The various distances should be calculated and marked on the fabric.

Connecting the chains:
The shovels of the first chain (made of 18 pieces part 1) will be fixed on the wall of chain to (part 2 pieces). As the outmost unit has 18 shovels and the middle unit has 12 pieces on which we have to fix them evenly distributed we'll do the following:

All the shovels should have in the end the same distance to it't neighbour. This distance is depending on the amount of fabric used to chain the pieces together. You have to check/adapt it in your version.
In my case the first shovel was about 2.5 cm away from the starting (seam) of the part (measures taken at the top edge), the second shovel about 2.5 cm away from the end of the first piece. The next shovel needs to be fixed in the middle of the second part of the middle unit.

Now we have to connect the shovels from the middle unit to the chain made from part 3 (innermost unit). As we have 12 shovels to fix on 6 parts of the innermost unit, we have to fix 2 shovels on each piece of part 3. Again here all the distances from the shovels to it's neighbours need to be the same.

Now all the three chains are connected, we are ready to close the rotor.

Closing the rotor:
First of all the 6 shovels of the innermost unit need to be brought together in one seam, easiest done by sewing 3 and 3 together and then connecting those two packets with a final seam.
Now we can close the innermost ring (built from part 3 pieces) by sewing edge A-A of the first part of the innermost chain onto edge B-B of the last piece of the same chain.

Now we can close the middle and the outmost units the same way.

This gives us the finished rotor, on which we will attach the enforcments and the loops at the leading eadge in the next step.

Enforcments at the leading edge:
The shovels of the outmost unit are starting about 1.5 cm behind the leading edge of the outmost wall of the Rotor. This salient leading edge needs to be enforced now by a 3 cm Dacron ribbon.
We fold that ribbon in the middle and put it over the leading edge where it will be fixed by a seam:

Bridle Loops:
To allow an easy and proper attachment of the bridle I recommend to attach bridle loops. Another possibility would be attaching the bridle lines directly at the enformcments on the leading edge. But this makes life harder if you have to change the bridel.

The easiest is to attach 18 bridle loops, exactly onto the seams between the different pieces of the outmost part. This way you do not have to thing about the distances between the bridle loops and their position.

Another possibility would be attaching 16 bridle loops (recommende in the original dutch plan). This gives you 'some' savings in material and weight but much more work in calculating and marking the positions.

The bridle loops are built from 2 cm wide fabric. This ribbon is double folded and sewed together. I recommend to build a long enough piece and the cutting 4 cm pieces for the loops.

We need to sew this loops now onto the enforcment on the leading edge. In the end, the backend of the loops should be at one level with the backend of the enforcments.

The rotor is now finished. Only the bridle needs to be attached.

Bridle of the Rotor

The overall length of the bridle should be between 80 cm and 100 cm. It is important that all the bridle lines have exactly the same length to allow the rotor to turn evenly. The bridle should be attached to a ball bearing turning piece. If the rotor will be attached to a flying line of a kite, you should attach a strong piece of about 1m length to enlarge the distance betweend the fast turning rotor and the flying line. This reduces the probability of big knod of the rotor and the flying line.

We have different possibilities to knod the bridle, depending on the number of bridle loops chosen before:

Personally I prefer the possibility with 18 bridle loops and two parts of the bridle. For that I cut nine pieces of about 1 m for part 1 of the bridle. One end of such a piece is connected to a bride loop and the other end to the next (neighbour) bridle loop. If you attach all the nine pieces this way part one of the bridle is already finished. For part two I cut nine pieces of 0.5 m length. One end of this pieces is connected to the middle of a part one line, all the other ends are brought together in one point.

That's it, folks. Good luck and enjoy it.