Construction of the Prometheus 100

Prometheus 100 / Ravi Raj 100

Please note that this document is a Beta Version. The technology described in this document is put in the public domain by the author and designer Eerik Wissenz. The document itself is an original artpiece licensed under Creative Commons Attribution-Noncommercial-Share Alike 2.0.

A frame is mounted on a post.
The whole structure is rotating around a mast which height is 2.80 m from ground.
Total dimensions of the machine 4.80 m x 4.10 m.

In this document P1(prototype 1) refers to the dimensions and materials of the first prototype built in Rajkot.
Please note: when a hole is described “at the end” of a piece it is 1 cm from end. Holes are 6 mm and smooth if not otherwise indicated.

Introductory Video:

(Video Url)

1. BASE
A strong cross with width at least half the lenght of the whole structure (lenght of mainbeam).

P1: 2 box tubes 40 mm x 40 mm, length 3 m.

2. ROTATING POST
a) Bar or tube welded in the center of the cross (fixed tube).
b) A second tube is attached to rotate around the first tube at height 70cm from the ground. Bearings can be used or the rotating tube can sit on a boost of the same size welded to the fixed tube.
c) The height of 70 cm is determined by the vertical drop of the mainbeam with respect to his slength.

P1: A tube of 50 mm diam. is fixed to the cross.
Bearings are attached to the base and at the top of this tube.
Inside the bearings a bar of 30 mm diam. is fitted to rotate inside the fix tube.
The top this bar has 4 cm clearance to weld a plate to hold our mainbeam.
Our slength is 10°, and mainbeam 4.4 m which give us a drop of 38 cm. To this we add a clearance from the ground determined by the ground nature and necessary minimum space to work under the machine (fix reflectors, clean, etc.).

Commentary: The use of bearings was not necessary because the leverage the main beam provides when turning the machine is very great. Also, the machine must not turn by force of wind. A pin was added for bearings.

3. MAIN BEAM
a) The main beam must be fitted to the rotating post at an inclination determined by the shadow each cross row would cast on the next if the inclination was 0; the greater the inclination the lower the sun can be in the sky without shadow obstruction.
The lenght of th main beam is determined by the space between each cros srow + the clearance on each end for our guidance system and reinforcement cables (see 6 and 7).
b) Holes must be drilled for a pin on which the cross rows can rotate. The distance between each row is determined by the circle the cross row will draw when rotated + a clearance in case of imperfectly position reflectors. Holes must also be drilled at the ens of the main beam to attach our guidance system.

P1: The distance between the holes on the main beam is 40 cm, 8 mm diam. The main beam was attached to the rotating bar by a serie of plates: 2 plates welded together with a 10° triangle in between.

4. MAST
A mast must be attached to the center of the main beam such that to be perfectly in line with the rotating post. The design of the mast will depend on the focal point height and application.

P1: To calibrate the reflectors a piece of tin on a boost suffices at 2 m. For the boiler, see section 9.
A tube of 50 mm diam. has been used.

5. CROSS ROWS
a) Holes to attach reflectors must be drilled with a span of slightly more than the reflector width (P1: 33 cm).

Commentary: the reflectors must tilt more the further they are from the center to hit the focal point. Because they are reflecting at an angle they must be further from their neighbor to avoid casting light onto their back. This does not affect the function of the machine but simply represents wasted mirror.
P1: added 1 cm every span to compensate this effect.
See program of calculation.

b) One cross row is composed of 2 halfs. Each half is connected to the main beam and attached to each other. Each cross row must rotate on the main beam.
Each half has a long horizontal box tube (P1 2m) and a vertical piece is welded on one end to create a T, with a very short and a very long end.
P1: horizontal box tube 2 m and T height 40 cm.

Commentary: We can attache the cross row to the main beam at any point on the T. This point will become the axis of rotation of the cross row. If the axis of rotation is at the same level as the box tube, then the reflectors will swing around this axis and take up more space (the reflectors must not hit the reflectors of the nearby cross rows). So, to minimize the space, we place the axis of rotation at the center of our reflectors. If our reflectors are 8 cm (as in P1) above the box tube, then we drill the whole on the T 10 cm above the box tube.
This also balances the cross row making it easier to rotate, facilitating our guidance system (see section 7).

Each T has one hole on its short side to connect with the other half of the cross row. This connection is fixed with bolts.
On the long side of each T, measuring from its base (at the meeting point with horizontal box tube), there are 4 holes.
Hole 1 = a pin of smooth rod through the main beam - the cross row rotates on this pin (P1: 8 cm, diam at least 8 mm - larger will be more stable).
Hole 2 = a bolt to connect to the other half of the cross row (P1: 15 cm).
Hole 3 = is to connect to our guidance cable and is different for each cross row (see 7).
Hole 4 = at 1 cm from the top is for wire to connect to the outside end of each T, to remove bending.

c) A box tube must be welded on the outside of each half cross row to connect the other end of the wire. By tightening the wire, the bending of our horizontal box tube can be eliminated.
Commentary: this wire can also be replaced by a thin rod welded in a jig to ensure straightness.
A whole must also be drilled at the axis of rotation same as the whole for the pin, for our steel flat stablelizer.

6. STABLELIZATION
The ends of the cross rows must not sway into each other. So their space between them can be fixed at their ends with a steel flat with holes corresponding to the holes on the main beam.
The holes can be threaded and then attached to the end of the cross row at the axis of rotation with a bolt (as in P1) or a loose bolt with double nuts on the outside can also be used. The cross rows are free to rotate but the distance between them is fixed.
Commentary: to remove swaying of the entire machine, this steel flat can be itself stablelized with cables or rods from each end to the post. Also, a reinforced box tube could be attached from the center to our steel flat.

7. GUIDANCE SYSTEM
Relative to each other, each cross row must be inclined at a different angle to hit the focal point. But all cross rows must rotate at the same rate to adjust the machine; so the distance between each T must remain the same and rotate together.
We accomplish this by running a cable (or rod) the length of the main beam where each T can be attached. However, since the T must rotate, the attachment to the cable must also rotate, accomplished by a small steel flat with a threaded whole in the center that can rotate on a bolt fixed to the T.
The cable can be then attached to this small flat (P1: 2 holes on each end of the small flat each with a cable clamp).

Since each row is at a different angle, but we want our cable to be straight, the hole on the T for the cable attachment will be different for each cross row.
To calculate see program.

8. REFLECTORS

a) Each of our final reflectors is a very slight paraboloid approximation made of 9 flat mirrors, 10 cm x 10 cm each.
Every position is different but many are similar enough in distance to focal point to use the same reflector.

For each focal distance a first reflector has to be calibrate at the beginning of the process. These first reflectors will not be on the final machine but used to make plaster molds which in turn will be used to form our final reflectors.

To build these first reflectors (primary), you need a square wood of 30 cm x 30 cm, then 9 squares are drawn for each mirror, with 3 screws underneath each square.
The paraboloid will be calibrated empirically on the machine itself, by observing the reflection of each mirrors and adjusting screws one by one to have all the 9 reflections on the focal point.
Commentary: only the central mirror is fixed at the start and will serve as our reference. The others mirrors cannot be fixed since then cannot be adjusted and no calibration can take place, they must be held on the screws by hand and calibrated one by one until all the positions of the screws until all the positions are correct (since all our mirror are the same thickness, we can use any other mirror for the next step).

P1: has 100 reflectors. 6 focal distances were chosen to have paraboloid molds made. So we will require 9 x 100 mirrors for our reflectors and 9 x 6 mirrors for our primary reflectors (total 956 mirrors 10 cm x 10 cm, 2 mm thick). The more precise is the mirror cut, the easier the work will be.

For positions of these first reflectors, see program.

Our result is a piece of wood with one mirror in the center and screws all around. 8 mirrors can now be glued in place around the central mirror. Our primary reflectors are face up. They can be tested again on the machine to ensure good calibration. Each primary reflector is given a number and an arrow to indicate the its orientation with respect to the machine. The primary reflector is convex.

Then build a fram around each primary reflector and pour plaster of Paris. Commentary: any bump above our mirror surface will become a whole in our mold, which is the inverse, and so not a problem if the majority of the surface is true. However any whole in our primary reflector will be filled with plaster and cause a bump, changing the angle of the mirror placed upon it; to avoid this tape is placed on the junctions lines between the mirrors and along the base of the frame. As much perfection is needed in the calibration and mold casting since any error will be multiplied on every copied reflector, which can even be for more machines of the same type!

P1: plaster of Paris has been mixed with fiber glass for more strength.

Once the plaster of Paris is dry, it can be demolded and the number and orientation of the corresponding primary reflector must be written on the plaster. The mold is concave.

New mirrors are now placed face down on the mold and fixed together with polyurethane or resine and fiberglass or some other extremely strong method allowing no change in angle whatsoever. The “hand” (see bellow) is glued in the center. When the glue is dry, we take off a copy of our original convex primary reflector.

b) To connect the reflectors to the cross rows we require 2 pivots: one giving us vertical movement and the other horizontal. With this control it is possible to fix each reflector to reflect sunlight on the focal point.
Our first piece is a “hand” that is simply a piece of angle (or flat bent at 90°) and a whole drilled on one side at least 1 cm from the corner; the other side is glued to the reflector (see step above).
Our second piece is an “arm” of straight flat twisted at 90° in the center with 1 smooth whole at one end and 1 threaded whole at the other. This threaded whole attaches to the hand with avoides using a nut, making fixing on the cross rows easier.

P1. Hand 2 cm x 2 cm angle. Arm 10 cm x 5 mm.

9. APPLICATIONS
Anything placed in the focal point we call an application. Our first one is simply a piece of tin horizontal at the focal point to allow us to calibrate the primary reflectors. Our desired applications must be built so that the focal point is not obstructed by the mast. So, a structure avoiding the focal point must be created and fixed to the top of the mast (the mast must be correspondingly shortened so the focal point remains true). If we do not want the application to rotate with respect to the ground we can make it rotate with respect to the machine; cables can then attach the application to the ground, fixing it in place and providing further stability. For this method the upper mast must be perfectly centered with the lower mast.
Another method would be to remove the upper part of the mast and hang the application from an exterior structure; for example a thick cable between two walls or columns.
Applications possible: steam production, oil circulation, pasteurization...

10. PROGRAM
To calculate the focal distances, distance to the guidance connection for each cross-row, and the angles of all the reflectors, The Prometheus System Calculator was created in Spreadsheet (Linux), available for Excell (Windows).

Eerik Wissenz - 28 October 2009 - Rajkot (Gujarat)