Brief Review of “On Combat”

I recently had the pleasure of finishing: OnCombat: The Psychology and Physiology of Deadly Conflict in War andPeace, by Dave Grossman and Loren W. Christensen.

 http://www.amazon.com/On-Combat-Psychology-Physiology-Conflict/dp/0964920514

Obviously, Public Invention has nothing to do with combat. In fact, I eschew the creation of weaponry. I believe mankind needs to focus on the creation of what Buckminster Fuller called “livingry”---inventions which make life better for mankind.

Nonetheless, this a great book in and of itself. However, it is also relevant to Public Invention.

Lt. Col. Grossman is creating (along with others) what he calls “warrior science”. This is simply the scientific study of the affect of combat on the warrior, and the warrior on combat. I emphasize scientific because of course since the Iliad and Mahabarata war has been a central theme of mankind's stories. Only recently has the warrior been studied scientifically, leading to insights that can help the warrior both in combat and more importantly after combat. Among the most important realizations of this science are physiological and psychological effects that were previously unexplained and therefore disbelieved, often leading to warriors being treated with shame and incredulity.

Although interesting, I will not recap these important findings here, because they are not relevant.  However I invite you to read this excellent book if you are interested in that sort of thing.

What is relevant, however, is that Grossman and others have done and are doing for a different field what I want to do for Public Invention. They have written Warrior Science 101. Perhaps only the first edition, but they have clearly amassed a valuable body of knowledge on the subject.

So, can we do the same for Public Invention? Well, invention is probably harder, because, by definition, it must be new. In 500 BC solving a triangle was a great and innovative achievement, but today it is not. In 1609 BCE a telescope was a great invention, today it is not.

However, we should not let this discourage us. The matter is simply untried at present. There have been studies of creativity. There are studies of genius. I don't think there has been a study of systematic attempts to improve the world by teams of inventors motivated by altruism rather than money.

So I remain hopeful that we can begin “Public Invention 101”, and develop a culture and technology of world changing.

As it happens, I am still waiting for you to join me---so don't be shy. Please comment or promote this blog.

No major work this weekend....

However, I have ordered the aluminum for a new set of pedals for the Merfluke.  I think I'll try riveting foot pockets on.  By building a new complete set of pedals I can do a side-by-side comparison.

I still want to work on the solar-cooker-in-the-park, but I want to give the best presentation I can at the Austin Mini-Maker Faire---and that means I need performance data---and hopefully some that is a little hopeful.

Merfluke Project Report #4: Can't keep my feet in

Today I went back to Lake Pflugerville, a very small man-made lake, and tested the Merfluke.  It was a major disappointment, although it is no worse that my previous attempts.  Basically, I was really slow.

I swam about 200 meters (across the lake) in open, choppy water, and then back.  In open water it is very difficult to tell how fast you are going (the lake was generally not clear enough for me to see the bottom, which might have been a reference point.) I suspect I could have swum it faster without fins at all, doing the freestyle crawl.

As in the past, my "downstroke" or power stroke, where I am kicking downward with my thighs, felt strong. I could feel the water rushing past my face.  Unfortunately my recovery or "upstroke" seemed to actively slow me down.  By using extreme toe flexure I could avoid this, but I couldn't sustain that for long.  I then more or less moved to a "relaxed" upstroke with relaxed feet, which tended to let my feet come off the pedals.  I definitely couldn't keep my heels on the heel stops that I created just for this purpose.

This is very disappointing, because it leaves open the question of whether good foot contact would allow me to go faster.

I suppose that the only thing I can do now to try to address this is to build a new set of pedals, going back to tight neoprene foot projects. This is a major setback.  Once I have solved it, success will still be very uncertain.

This is the way real invention works: frustration on top of impediments fertilized by setbacks based on failures. At least that is what a great, noble-hearted and persistent inventor would tell himself or herself, so I'm sticking to it.

Austin Mini Maker Faire (and draft of Merfluke paper).

I answered the "Call for presenters" of the Austin Mini Maker Faire with a proposal about my Merfluke.  This places upon me a responsibility to get some performance numbers pronto!  Luckily, Spring has sprung here in Texas, so I should be able to get in the water soon.

I am also working on a technical paper which I hope to submit to the Open Hardware Journal.

In the spirit of Public Invention, here it is in its current state of unreadiness---typos, mistakes, awkward sentences, and muddle-headed thinking all stewed together. However, a public inventor must "Tell the truth, tell the whole truth, and tell it right now" as Buckminster Fuller said---even if that means you get to see the sausage being made.

I especially apologize for the incomplete technical references---I'm relying on some technical research about dolphins that I read years ago and would like to add to the references, but I suppose it will wait---don't be offended if you think your work should be cited---better yet, contact me and tell me so.

The Merfluke: A Machine for Human Thunniform Swimming

By Robert L. Read

-- Art by Ymki van den Berg

Thunniform Swimming

Tuna and whales, the fastest creatures in the ocean, swim by driving a relatively thin plane back and forth through the water at angles which they can precisely control so that their tail or fluke describes a sinusoid. This is called thunniform swimming and is mechanically quite different than what a trout-shaped fish or a human being wearing swim fins or a monofin can do, which is called carangiform swimming. Carangiform swimming is a total body wave of amplitude increasing from the head to the tail, which is broadened and flexible. Often human swimmers wearing swim fins use them independently, and don't really use a total body wave; however, competitive swimmers and monofin swimmers have solidly established the “total body wave” approach as the most efficient swimming style. Competitive swimmers use the underwater dolphin kick as much as the rules of their sport allow without the benefit of a broadened tail. Monofin users performing the same motion are the fastest and most efficient human swimmers at present. The goal of my investigation is to build a machine that allows a human being to swim using thunniform motion. There is a scant but real possibility that such a machine would allow human being to swim better in the future than the monofin does today.

Dolphins have flukes and tuna have tails. Dolphins have a ball joint between their spine and fluke that allows them to angle it up and down. Tuna and tuna-like fish, such as mackerel, have a peduncle, which serves the same purpose of allowing them to angle the tail independently of other body motion, and to do so forcefully. Dolphins and fish are symmetric in the direction in which they oscillate.

Although it remains an interesting area of research, I would like to make some educated guesses or supported assertions about how a dolphin swims, even if these points are not completely proven:

1. Dolphins move their bodies relatively little as the drive their flukes up and down.
2. At cruise, the fluke stays within the wake, beam, or shadow of the body.
3. If we call the wake of the dolphin a “beam”, the fluke stays withing the beam and furthermore is parallel to the direction of motion when it is at the extreme edges of the beam, and is at its greatest angle to the direction of motion when it is in the center of the beam.
4. Dolphins can probably sense the edge of their own “shadow” in the water as slight difference in water turbulence as their flukes reach the extreme end of the beam.
5. The split shape of the fluke improves its vortex shaping ability. (This is also true of perch and catfish, which use a different motion to similar shed counter-rotating vortices.)
6. From videos, it appears that the fluke of a dolphin bends relatively little during normal motion.
7. Dolphins can oscillate their flukes at 10 Hz at their top speed. Human being run at 3 Hz. Champion monofinners swim at 1.8 Hz. It seems unlikely that we can comfortably operate any higher than that.

Human Anatomy

To support human thunniform swimming, we can construct a machine, called a Merfluke, that allows us to angle a fluke up or down by rotating our ankles. The fluke can be driven up or down through the water with the muscles of the upper legs and the torso. I have developed seven distinct prototypes of the Merfluke over the last five years. The latest model works, in that it allows a human being (me) to swim in a thunniform fashion for a few hundred meters. Its performance is at present much less effectively than flexible swim fins, however.

Herein lies a problem: humans are not symmnetric front-to-back. We have feet that point forward and cannot be made to point backward. Further, we can jump. Jumping exerts a tremendous momentary force on the ground. We cannot pull up with the tops of our feet with nearly the same force that we can push down with the bottoms of our feet. This is a significant problem for monofin swimming. It tends to separate the use of a floppy fin into a power stroke and recovery stroke. The recovery stroke provides very little power, but is needed to position the fin for the power stroke. This problem can perhaps be abated by skillful employment of the whole-body wave, but cannot be eliminated.

Wave Theory and Strouhal Numbers

It is clear from watching videos of dolphins that when accelerating that begin with a very large amplitude, slow frequency wave and as they move faster their fluke makes smaller, higher frequency motions. This is relatively complicated to describe mathematically, but if we imagine a streamlined body “cruising” efficiently at a constant speed, we should be able to describe it with basic mathematics. This will be more accurate for a body which has very little drag.

Definitions:

Wavelength (λ) is the distance between the same points in a cycle, such as the point at which the fluke is highest, measured in meters. Frequency (f) is the number of oscillations per second, measured in Hz. Speed (v) is measured in meters/second. The basic equation relating these three equations is:

(0) v = λ*f

Of particular interest to us is the Strouhal number[1], because it is observed that swimming and flying animals tend to cruise in a limited range for Strouhal numbers.[2]

For our purpose the Strouhal number can be defined as the dimensionless ratio of the amplitude of the fluke (its up and down travel distance, or throw, R) to the wavelength (the distance traveled in one oscillation.)

(1) 1/S = λ/R

It has been observed that inverse of the Strouhal number tends to be between 3 and 7. If we guess an inverse Strouhal number to target for the human athlete, we can combine this with (0). I made an educated guess that I wanted to swim at 2m/sec with a frequency of 1 Hz. Champion monofin swimmers swim at frequency of 1.83 Hz, but that seems quite ambitious to me. Plugging these values into (0), we can compute a wavelength of 2 meters. Rewriting (1) to compute throw: 

 

(2) R = λ/(1/S)

To achieve an inverse Strouhal number of 3, we need a throw of 2/3rds of a meter, we need a throw R of 26.25 inches. To achieve an inverse Strouhal number of 7, we need a throw of 2/7ths of a meter, or 11.25 inches. I therefore chose the length of the Merfluke extension beyond the feet to be 18 inches, which is a guess that in a normal motion for myself the throw will be 18 inches. As is typical of this kind of work, it is difficult to be precise because we are not just building a machine---we are creating a prosthesis that extends the human machine.

If we oversimplify the swimming motion and describe it as a simple lever oscillating back and forth around a pivot point located in the hips, then the throw can also be computed by equation (3).

3. R = 2 * (hip-to-fluke distance) * sin (half angle of oscillation).

I am 5'10”, and have a 30” inseam. My waist is approximately one meter above the soles of my feet. Since the distance (measured along the direction of motion) from the ankle rotation point to the fluke rotation point is 15” and the fluke extends about 3” beyond the rotation point, we find:

4. 0.5 = 2 * 1.0 * sin (half anle of oscillation)
5. half angle = arcsin(1/4^th) ~= 15 degrees,
   
   which seems like an achievable degrees of oscillation. However, the pivot point might be closer to the knees than the waist. Since the swimming motion remains to some extent a total-body motion, if only because the torso must move to balance the motion of the legs, maximal angle of deflection cannot be theoretically predicted. So we have a theoretic hope that a human being of my size can cruise with the Merfluke 7 at a reasonable inverse Strouhal number. However, the combination of the human athlete and the Merfluke extension is so complicated that any theoretical result must be experimentally verified.
   Additionally, one desires a throw small enough that the Merfluke does not break the surface of the water when swimming with a snorkel.
   
   
   The diagrams in the paper are all drawn as if the dolphin or human athlete is swimming with an inverse Strouhal number of 3.

Design of the Machine

 

The basic parts of the machine are:

1. the frame and the leg braces,
2. the pedals,
3. the fluke, and
4. the connecting rod.

These our components form a 4-bar linkage. The entire linkage is driven up and down through the water over the throw R. As this happens, the swimmer rotates the ankles, thereby changing the configuration of the linkage. The purpose of the linkage is two-fold: to make the fluke move through twice the angular deflection of the ankle, and to center this deflection when the foot is held in a natural, neutral position.

Additionally, the center point of deflection is 3” lower than the rotation point of the pedals which helps to keep the fluke under water when the swimmer is swimming at the surface and breathing with a snorkel.

Drag Testing

Incontrovertibly minimizing the drag of the total human/Merfluke combination is critical to its performance.

A homemade drag test was creating using a fishing rod and reel, two pulleys, a carabiner, and scale. A heavy fishing rod and reel was strong with 80-lb monofilament line. The line was run to a pulley attached to one of the eyes, and then back to a pulley attached to scale. The other end of the scale was attached to the handle of the fishing rod. In a steady state, the scale reads twice the force in pounds that the line is being pulled away from the rod.

The remaing fishing line was strung through the remaining eyes and a carabiner tied onto the end, so that I could comfortably hold on to something in the water.

I then swam out to clear water and had my son drag me at a constant walking speed while my wife observed the average force read by the scale. The results were:

	Average drag force
Human and swimsuit only	8 pounds
Human and swimsuit and monofin	9 pounds
Human and swimsuit and Merfluke	12 pounds

These measurements are valid relative to each other, thought they have no value for actually determining the drag coefficient of the monofin or Merfluke. 

 

This unfortunately does not bode well for the Merfluke achieving the goal of besting a monofin, since even if it allows greater propulsion, it will have to overcome significantly greater drag.

However, the drag of the Merfluke can be great improved with better craft technique than I have so far been able to apply in the Merfluke 7.

Safety

Never swim alone. Never swim without someone who is capable of rescuing you.

The Merfluke 4 used tight neoprene foot pockets, similar to swim fins or a monofin. I believe this is less safe than the current design, because if the Merfluke were to snag on a cable or weed under the water, the device cannot obviously be dismounted quickly. People often feel anxious for this reason the first time they try a monofin. The Merfluke 7 improves on this design by allow the machine to be dismounted by simply spreading the legs apart. It is also easier to mount than the Merfluke 4 (though dismount remains easier than mounting in the current design.

I believe using a Merfluke has several dangers. First, there is the danger of simply panicing, inhaling water, and drowing. Secondly, the Merfluke has more opportunity to snag on stone, cable, tree, or line under the water than do smooth fin swims. A diver can then dismount the Merfluke, but then must reach the surface without it. Thirdly, it shares a risk with swim fins and monofins---that of going fast enough that you strike a solid object and knock yourself unconscious. Never swim alone.

Finally, it is unusual for large marine animals to act aggressively toward human swimmers, but there is a small chance that a human swimming with a Merfluke would be treated more aggressively than a human swimming with normal fins for reasons that would remain to us unfathomable.

Fabrication

(Please refer to the Bill of Materials that follows.)

Frame

The frame shape is relatively complex, but is easily cut with saw blades designed for cutting aluminum. Every aluminum cut should be rubbed down a bit with a file, which greatly reduces the chance of the edge slicing human skin.

The leg braces can be cut for bars of aluminum and bent with a metal brake, or, in a pinch, with a hammer and a vice. After using bolts on previous models, I now prefer to rivet the braces to the frame and to each other.

The soccer shin guards are mounted onto the braces with screws, because there is a good chance you will want to replace them later or reposition them. In general the EVA foam inside the shin guards is thick enough that a flat-headed machine screw will not protrude enough to scratch the legs. Shin guards typically come with velcro straps to strap the guards to the legs. These should be carefully cut away, as it would be unsafe to use the straps in the water and only add drag. On some shin guard models, the stitching that holds the EVA in place also holds the straps in place, so be careful to not damage the stitching of the EVA, as it is needed for padding and comfort.

Peduncle

The peduncle is fundamentally two 6” disks of aluminum held apart by scrap aluminum. Pop rivets are used to rivet through the two discs and the scrap aluminum, thus forming a single secure peduncle. The peduncle is attached to the frame through a hole in its center using a 1/4” shoulder bolt. Using two nuts separated by a lock nut has proved a very reliable and convenient way to building this joint and the other three moving joints.

The peduncle has a second hole for connecting the conrod. Both the conrod and the frame fit inside the two discs of the fluke. The conrod transfers rotational force to the peduncle from the pedals.

Note that the peduncle has a slot cut into in into which the fluke is inserted, which allows for effective transfer or rotational force into the fluke.

Pedals

The pedals are the most difficult component to manufacture.

My approach has been to keep one large piece of aluminum perfectly flat. This plane will be in contact with the frame. Hopefully, and apparently from my experience, a thin layer of water will lubricate these two large planes, so in fact there is little friction between them. This only works, however, if the all bends are made away from the plane, and no rivets or screws are placed on plane in contact with the frame.

Although my design can be improved upon, the basic design is keep a large plane, bend two pieces away from the frame that can be used to rivet the foot-deck in place, and bend the bottom piece up to hold a triangular brace and to attach the pedal shroud.

Additionally, two small pocket cuts must be made to create tabs so that the top-of-foot-block can be mounted. These should be started with holes that are drilled. A band saw, saber saw, or hack saw can then be used. Generally speaking the tabs can be bent into place with a pair of pliers and some hand strength.

It is very important to leave a small piece of aluminum for the heal to brace against, as this presents the foot from pulling away from the pedal on the up-stroke.

After the pedals are riveted together, cage that generally has the correct shape and is strong enough to support the foot. 

 

The top-of-foot blocks were cut from a 4x4 in an attempt to be both comfortable and to improve the hydrodynamics of the foot. For a human being prone in the water, the feet actually represent a large area facing the direction of flow, so the idea is to streamline them by decreasing the angle of attack. More importantly, that athlete must have something to pull against with the top of the foot to recover during the upstroke and to have control of the fluke angle.

After carefully attempting to cut a plane matching the shape of the top of my foot and rounding the blocks where the toes begin and on the back side, I coated with three coats of polyurethane coating. This delayed or prevented them absorbing water.

It is then absolutely essentially that some kind of padding be applied to the blocks where the foot contacts them. The human foot is very tough on the bottom and very delicate on the top. I found that a half-inch exercise mat cut into the appropriate shape and contact-cemented on is effective.

Although the Merfluke will function with pedals made only of aluminum, in the current design it is important to cover them and fill them with a buoyant material for two reasons. First, shadow or wake of the foot is hypothesized to be one of the main sources of drag. We want to produce a hydrodynamic shape when the pedal has a foot in it and is moving through the water at 2m/s. The best shape for this is complicated by that fact that it changes position during the swimming stroke. I therefore estimated that a generally rounded shape would be best.

I had a seamstress sew the pedal shrouds in generally rounded shape out of a material called marine vinyl. She did this by trial-and-error when I loaned her the pedals, so unfortunately I have no reproducible pattern for this complex shape. I attached the shrouds to the pedals by riveting them. I then filled them Tough Stuff ™ brand expanding foam, which cures into a solid mass which further strengthens the pedals and adheres the shrouds into place.

The overall pedal assembly is then bolted to the frame using a shoulder bolt.

Note that in the pedal design the conrod is attached quite far ahead of the toes. This is not obvious and took a great deal of trial-and-error to discover. I believe this helps to center the full range of motion of the foot around the neutral point of the fluke, and to allow the most balanced match between the rotational range of the foot in a prone position and the desired rotational range of the foot.

I am somewhat disappointed in the availability of free software for synthesizing 4-bar linkages, although there seems to be plenty that will analyze a designed linkage. I chose this design through trial and error with pencil and paper.

Fluke

The fluke is a relatively simple plane that pushes the water. My current model is constructed of aluminum and polycarbonate riveted together. I'm not happy with my design put present it here anyway, although you may wish to improve on it.

My shoulders are about 24” across, so I made the fluke the same width. The fluke is braced with aluminum bars, which are necessary to strengthen it against the large forces that would bend it. However, in the future an internal frame or more hydrodynamic bracing might be better.

The lateral stiffness is provided by a plate of aluminum. The current fluke is cut into a “W” shape but I have no reason to believe that is a good shape. In general I think we should mimic a dolphin fluke until theory and experience allow us to design a better shape.

It is critical that the fluke be more flexible at the back end than at the front, so that when pushing water it can naturally conform to the shape of water flowing around it. This will minimize the turbulence produced in the water. Although a stiffer fluke may someday be used, a soft fluke is needed now to be forgiving of imperfection in the athletes motion. 

 

I conjecture that the split, dolphin-fluke shape allows a more coherent vortex to be shed when swimming. It is important to note that in a split design you have to drill out a circle of sufficient radius so that the bending forces are not concentrated in one place. Although the triangular braces prevent bending strain and polycarbonate is a wonderful tough and resilient material well suited to this purpose, it is not infinite strong---I cracked flukes on previous models.

Conrod

The conrod connects the pedal to the peduncle. It is the simplest component. Note however, that you can drill several holes in the conrod to allow for slight adjustments to the action of the linkage in the field.

The 4-Bar Linkage

When the conrod connects the peduncle to the pedals, the whole system forms a 4-bar linkage that allows the angle of the fluke relative to the frame to be controlled by pointing the toes (pushing against the pedals) or flexing the toes (pushing against the pedal blocks with the top of the feet.) The fluke should be in a neutral, gliding position when the foot and pedals are at the center of their range of motion, which seems to be about a 45 degree angle when the feet are relaxed in water. Extreme pointing of flexure should allow the fluke and peduncle to move through from the down-stop to the up-stop, about 150 degrees of motion.

The Swimming Experience

It is best to be in shallow water when you mount the Merfluke 7. I generally put on my mask and snorkel and carry it out to shallow water. Although you can in theory straddle the machine and simply push your legs together, in practice they catch on the edge of the shin guards, so I generally stab my feet down through the shin guards until the sole of my foot is flat against the pedal and my heel against the heel stop. Then I turn over (belly down, back to the sun) and push myself into deep enough water that the down-stroke of the Merfluke doesn't scrape the bottom. I place my arms straight out in the direction of travel, and try to squeeze my arms together in the “underwater dolphin-kick” pose used by swimmers after their turn.

The Merfluke is comfortable on the legs, and provides good leverage for a good hard push against the water. If you just wave it up and down with your feet relaxed, you will move forward. To gain velocity, however, I think to myself the sequence “point-kick-flex-pull”. This of course ideally should not be a strict sequence, but a coordinated movement, although it takes a while to learn and no doubt I will improve with practice. This sequence means “1. Point the toes--- 2. Dick Downward with the thighs---3. Flex the Toes toward the head--- 4. Pull Upward with the hams.”

If you do this vigorously (flexing the toes is the hardest part) you will go much faster, and begin to feel the water rushing past your face and making your snorkel thrum. With less vigor you can move steadily along. It is relatively easy to dive under the water and then come up, because if you are moving you have plenty of excess power for steering by simply directing your arms upward or downward.

Turning is harder, because at present the frame resists turning to the side. At present I just scull with my arms when I need to turn. I dream of the day that I have enough skill, depth of water, and visibility to perform an “Immelman turn”.

Experimental Performance

Lessons Learned

• Never swim alone, with or without a Merfluke or fins.
• Progress comes at the intersection of theory and practice. Every time I get in the water I learn something that surprises me.
• The Merfluke 4 used cables and sheaves to articulate the fluke. This was very complicated and not as sturdy as the simpler 4-bar linkage.
• A small amount of positive buoyancy is valuable to keep the device from sinking out of sight in deep water and to keep the swimming position prone. The book Total Immersion [4] discusses the importance of prone swimming position and other aspects of human hydrodynamics.
• Perhaps not unlike designing a bicycle, the pure engineering aspects of this kind of project are constantly tempered by the fact that it is an extension of a human being that has difficult to measure strength, power, and agility.
• The soccer shin guards provide a very comfortable application of pressure to drive the fluke up and down. However, more hydrodynamic solutions may be available.
• A boogie board is a valuable safety device when using the Merfluke for the first time.
• Because the Merfluke 7 does not lock the feet into tightly fitting neoprene pockets, there is a constant danger of relatively minor bruising and blistering due to the feet rubbing against improperly padded parts of the pedals.
• Placing a handle on the Merfluke was a major design improvement which made the device much easier to work with.

Possible Improvements

• Video recording to allow analysis of the swimming motion.
• Improvements in hydrodynamics:
  • Streamlining or reduction of bolts and nuts projecting into swimming stream.
  • Shrouding the entire area from the leg braces to the pedals.
  • Reducing or eliminating the fluke brace
  • Shrouding or removing the frontal area of the leg braces.
  • Better shaping a of the pedals behind the foot.
  • A fluke design that does not have protruding rivets.
• The addition of a spring to ease the pulling motion motion of the ankle (at the expense of pushing) to create a more balanced use of the asymmetric musculature of the lower leg.

Motivation for Continued Research

• It's fun to extend the range of human-powered capability.
• The lessons learned here could allow us to build a powered vessel that might be far more efficient and maneuverable than screw-driven vessels.
• The same oscillatory, non-propeller form of locomotion might be very valuable in propelling airships.

Bill of Materials

Tools

• Rotary drill with 1/8” and 1/4” bits
• (Optional, but helps) power saw with blade capable of cutting aluminum
• Hack saw
• Hand-powered pop riveter
• Aluminum pop-rivets with 1/8” diameter and 1/8” grab
• Aluminum pop-rivets with 1/8” diameter and 1/4” grab
• Metal File
• (Optional) Grinder
• Metal brake capable of bending aluminum at right angles (bigger is better but I use a cheap portable model that clamps to a table)
• Sewing machine
• Sand paper
• Disposable brushes

Frame

• (1) 4' x 1' sheet of aluminum ~1/8^th inch thick
  
• (2) Pairs of soccer shin guards with no fabric and EVA-style foam
• (6) feet of 1” x 1/8” inch aluminum bar
• (4) shoulder-bolts in 1/4” diameter
• (8) 1/2” machine screws with washers and nuts

Peduncle/foil

• (1) 3/32” thick aluminum sheet, 2' long and 1' wide (for fluke frame)
• (2) 1/16” right-angle aluminum pieces 1” wide and thick (for fluke outer rails)
• (1) Sheet of polycarbonate in a thin grade (1mm), 2' feet long and 1' wide
• (2) 1/8” aluminum bars
• (2) 3/32” aluminum sheet, 1' x 1' (for peduncle circles)
• scrap aluminum for spacing inside peduncle
• aluminum pop -rivets and hand-powered riveter

Pedals

• (1) sheet aluminum, between 1/32” and 1/16” or less in 1' width, about 8', for pedals
• (1) Marine vinyl, more than a foot wide, several yards
• (1) Sprayable polyurethane foam
• (2) feet of pine 4”x4” (or 3.5” x 3.5”) lumber
• (1) Brush-on polyurethane coating
• (4) Self-tapping screws
• (1) Contact cement
• (1) square foot of heavy foam, such as from a 1/2” thick yoga/exercise mat

Suppliers

• Online metals
• Metal brake
• Stanley Pop-riveter

References

[1] http://style.org/strouhalflight/

[2] http://www.nature.com/nature/journal/v425/n6959/images/nature02000-f2.2.jpg

[4] Total Immersion. Terry Laughlin, John Delves. Fireside, 1996. ISBN-10: 068481885X

Additional

I previously wrote about my disappointment in the solar cooker challenge to store energy at night to help deforestation in Rajistan, India.

I'd like to add some additional thoughts to that.

Looking at the photos  that were part of the E4C challenge, there are two photos of people cooking. It seems that they cook on what I would describe as an “half-open barbecue pit”. It appears to be about a foot square, and have about 8 inches of room for the fuel. Iron griddles and large earthen pots are propped up on the bricks directly over the flames. (http://www.flickr.com/photos/44221799@N08/6768398249/in/set-72157629047928423)

Following Kent Beck's motto “Do the simplest thing that could possibly work” it seems that trying to address this with a solar cooker is a mistake. What these people need is simple a wood-burning stove. I do not mean a large free-standingstove, but more like a camp-stove. On YouTube you can find plenty of videos about two stove technologies, the “rocket stove”  and the “gasifier” . I suspect both of these approaches, or perhaps extant stoves, would use the fuel twice as efficiently. This is the simplest way to decrease deforestation: give these people stoves.

Why was this not part of the solution? For two reasons. First, it isn't fun to try to raise $100,000,000 dollars to buy a lot of existing technology. That is not a problem that appeals to engineers like myself. However, we can't let this blind us to the truth: sometimes the best way to help people and improve the world is NOT to invent something, it is just to share more.

Secondly, it is embarrassing to say to poor people “You are harming the earth (though much less than I, who flew here in a jet), so please take this stove and burn less wood.” Worse, it is a violation of their free will, but not even in a way that aligns with any social compact. I don't mind if mankind chooses to tax carbon, and makes even the very poor pay the tax, as long as the rich must also pay the tax.

But I do not want to give a $200 iron stove to someone who might say to me “Thanks, but I don't want a stove, at least not know. You see, what I really want is to send my daughter to school, so I will sell this stove and pay for her to go to school for 2 years.” I think the poor people should just be given money, and allowed the freedom to decide what to do with it.

I am in inventor. I have always been an inventor. I knew when I was very young boy that is what I am supposed to be. If you like, you can say that is what God put me on Earth to do. (Granted, I am not a good one---I haven't invented much---but, obviously, I'm working on it.) If I spent my time raising money for poor people, I would not be a happy or fulfilled.

Therefore I am sticking to my original idea for a solar cooker to be used by people that I know and understand, here close to home, where I have some hope of success. Building a solar barbecue grill for use in Austin, Texas, is perhaps too humble a project but if successful it will improve the world, at least a little.

“Think globally, Act locally.” – Buckminster Fuller.

Some friends recently pointed me to slashdot article about a challenge on Engineering for Change.

https://www.engineeringforchange.org/workspace/view/22/1#tabs=/workspace/activities/22/1.

I was delighted to find E4C, as it is very similar to what I want to do with the organization I am trying to start, Public Invention for All Mankind (PIFAM). I have now joined E4C. Following Buckminster Fuller's dictum of non-competition, I would certainly prefer my energy to strengthen E4C than to run PIFAM just for the purpose of self-aggrandizement.

However, after some time reading on the site, I think it may be too soon to assert that PIFAM is completely irrelevant. The recent solar cooker idea that I proposed demonstrates some differences with E4C. Firstly, that particularidea, of placing a cooker in a public park in Austin, Texas, doesn't really help anyone in the third world, or even the part of the third world that we have here in the back-alleys of America. Secondly, I don't want to design for a low-cost solution, I want to design for an effective solution. Although I applaud E4C's design principles, there is room for projects that don't follow them. If we can successfully construct the public park solar cooker, we will not have achieved the benefit that E4C aims for of changing the whole world, but surely we will have made the world a better place. As Buckminster Fuller said, “Think Globally, Act Locally.”

I want to be perfectly clear that I applaud the challenge that was proposed and all the attempted solutions. Good work, engineers! However, I'd like to express some critical thoughts---but a critique rather than a criticism.

The challenge was carefully crafted to make cooking work for the people in India, without asking them to change their habits. This is great. Often I find myself playing what I call the “'Fonly” game. 'Fonly those people in India would learn to cook in the middle of the day! 'Fonly Americans would start riding their bikes to work! 'Fonly people would invest the 100 hours it takes to learn Esperanto! There are worse games in the world---cockfighting comes to mind---but the 'Fonly game doesn't lead anywhere.

However, I just don't believe this particular challenge is really possible. (I've looked over about half the 10 papers that were selected as solutions to the challenge.) I think, and many of the papers point out, that sensible heat is just too hard to store for a long time for one to be able to collect heat energy at noon and then cook in the morning with it. Some of the papers use either a battery or, somewhat exotically, molten salt, to store energy. But this seems to be counter-productive to me. If I am going to pay the price of converting sunlight to electricity (by which I mean both the cost of the photovoltaic arrays and the fact that only 10% of the energy will be converted), then I have simply created an electrified village. The idea of using a phase change material for storing heat could work---but the particular design seems so complex that again it would be easier to just electrify the village, or put the same resources into something else.

I have read some of these papers, particularly the one for University of Iowa. I would like to suggest a different approach, although I don't want to take anything away from those students. I wish I could have been on their team. They were constrained by the fact that they were working within a semester. However, reading their paper, I think they did too much design, and not enough building. Since I wasn't there, I can't really be sure what they did or why they chose to do it, but I'd like to describe the approach that I would take---and will take, on my own solar cooker project, if I can get anyone to join me. A lot of this design methodology I owe to Kent Beck and the other creators of the Agile software design methodology, which I personally believe can be applied to physical inventions as well.

• Nobody is likely to change the world in one semester. We have have to think in terms of multi-year projects.
• You go fast by taking small steps as rapidly as you can. No “Big Design Up Front”. If we are honest, none of us are likely to succeed in a challenge like this based on a single design. If you are skeptical of this, read the history of the Wright brothers and note all the baby steps they took before the Wright Flyer flew on its own power. It is an inspiring testament not to brilliance, but to persistence.
• You cycle from theory to test to theory to test as quickly as you can. The Iowa team does not appear to have done this---their paper makes no mention of intermediate results. For that matter, it makes no mention of final results either. I suspect their device simply doesn't even come close to satisfying the challenge---I hope I am proved wrong by them soon.
• You don't invest in building a giant collector when you can test a design be building a tiny collector.
• In the case of the system, they had independently tested systems, and they modeled them theoretically, but made no mention of an attempt to test them. For example, they do not mention testing there heat-storage system independently of a the solar collector. But surely this could have been done by just putting a heater inside the system, raising the temperature to an expected level, and seeing how hot it was hours later.

What does this mean for Project Idea #5, the Public Park solar cooker? Here is what I want to do. (Please, somebody, join me!)

• I will build a miniature model of the Compound parabolic collector with cardboard and aluminum foil. We will test the ability of this to collect light by direct measurement of both light and heat at the exit pupil. If we can't build a tiny CPC that will get an insulated box up to 500 degrees (F), then we should abandon the project. First you melt chocolate. Then you melt cheese. Then you toast bread. Then you cook an egg. If we can't make a little thing that will cook a thimble full of egg-white, we have no business building a big collector.
• If we can past that test, we can build a big collector out of sheet aluminum and rivets and test that.
• If that seems to work well, we will first build a properly scaled non-functional insulated box with a glass window and see that we can make it hot enough. If we can't do that, we need not waste time designing a convenient cooking surface.
• If we get past those steps, including an evaluation of how hard or easy it is to manage aiming it at the sun, we can design the insulated cooking chamber in miniature. If that seems to function, we can build a life-size model.
• We can then build the mounting post, spindles and counter-weights needed to make it truly function at a convenient cooking height.
• Then we get other people to test it and carefully note the problems and successes they have. We make improvements based on this information.
• We then test it in a real-world setting. This means we fill it up with pigeon crap and see how that affects it. We drop leaves in it and see if there is a danger of spontaneous ignition. We figure out if there is any way someone could be blinded by it or burned by it.

I'm forced to write this in a linear fashion---but it isn't really a linear approach. It's more a loop, or a helix: one step on the drawing boards, one step in a real world test, and repeat. Hopefully real progress is constantly being made, but APPARENT progress comes in fits and starts as you complete a test.

Most importantly, we do this PUBLICLY. That is why I call this “public invention”. That means that we post copiously, richly, voluminously. That means we publish our failures. We publish every step along the way---even when this exposes us to embarrassment and the possibility of ridicule.

As of right now, this blog has a tiny number of readers---three, on a good day. But I am trying to put the energy into these posts as if was widely-read, in hopes that content will eventually lead to readers. Please, if you have a related blog or some other venue, help me publicize this blog.

However, I soon hope to begin trying to recruit people here in Austin to help me directly---I don't intend this blog to be my only approach to getting PIFAM started---but it, and other web-related materials, will remain very important.

Project Idea #5: A Sturdy Solar Cooker for Public Use

There is a rich technology of solar cooking. I don't claim to be an expert on it, however my basic opinion is that it works, but is inconvenient.

I would like to try to change that by presenting a specific challenge. Here in Austin, Texas, we have recently been a severe drought so severe that charcoal fires in public parks have been disallowed due to fire hazard. In Austin's large central park, Zilker Park, there are normally large groups and families picnicing, complete with grilling hotdogs, fajitas, and, of course, veggie burgers.  The same outings are happening now without the grilling.

I would like to try to build a sturdy solar cooker that is so convenient that people would be just as happy to use it as a charcoal grill. This is, I think, quite a challenge. In general solar cooking requires a lot of attention, adjustment, waiting, and modifications of cooking practices. For example, when I was working with some wonderful people who were trying to do it in the ramshackle colonias of South Texas, they had an oven that worked for cooking beans and other slow-cooked foods, but was not terribly convenient.

There is a good reason for not focusing on convenience; the people who have worked on solar cookers so far have been coming from two angles: how can we help the poor who can't afford fuel for cooking, and how can we help the backpacker who can't carry fuel for cooking?

These are both noble goals. However, I am proposing something slightly different: a luxury cooker, in which we do not worry about money or weight, but focus on convenience.

One might attack this project by saying “What is the point of having rich people cook with solar energy? They will burn more fossil fuel driving to the park than you could ever save cooking.” This is, of course, true enough. However, as Dave and Pearl, my friends who tried to work with the people in the colonias, it can be a powerful symbol to start with a luxury good, because people want to emulate it. Although PIFAM is trying to be altruistic, I hope we will not be slavishly so. I am sure that succeeding in the challenge will help the next project that aims for a low-cost cooker.

So here is the challenge:

Let's build an installed cooker at Zilker park (how we get permission to do this, I don't know---don't bother me with details!) that:

• lets you cook at the same working height as the existing charcoal grills,
• cooks 6 hot dogs at least as fast as a charcoal grill,
• is safer to cook on than a charcoal grill,
• is less likely to ignite a fire,
• is wind-proof and vandal-proof,
• is fun to use.

This will be a significant challenge, but that is what we are here for.

If I can get a serious volunteer to assist me with this project, I will fund the project it up to $20,000.

What I really want is a team of workers, perhaps with someone else ready to lead the project, although I will be available to lead it until someone else comes along who wants to take charge. I think it would be really fun to have a number of people working on this project. Here are the kinds of help we could use:

• A team leader (I am a professional manager, but will bow out as soon as someone steps up to this),
• A test-cook (Enthusiasm counts more than skill---we're talking hot-dogs here!)
• An artist/designer to make sure it is beautiful (my weakest skill).
• A CAD designer to help us make computer designers (I can do this, but am no expert.)
• A heat/optics/mechanical engineer to design the collector and do the calculations to assure that on a sunny day we can beat a charcoal grill in cooking time.
• A metal-worker/fabricator to help us build the thing (I am pretty good with aluminum and pop-rivets, but I don't know how to weld, for instance.)
• A secretary/web designer/writer/videographer to document our progress.
• An electronics/microcontroller expert to apply temperature sensors, timers, and perhaps other control mechanisms to make the cooker more convenient.

I can do all of the these things myself, if I have to, but I know from experience that is a lonely business, and I need other people to keep my motivation going, and to help me tell a crazy idea from a good one.

If you think this would be a fun project, please contact me at the email above (read.robert at gmail.com), and let's get to work!

Here is an initial design that I would like to work from, though of course the reader may be able to think of improvements and elaborations:

* * *

This is just a short addendum to explain my relevant experience to this project. About 8 years ago I worked with a group of Gifted and Talented kids at Zilker Elementary building box-style solar ovens. It was not very successful, in terms of cooking, but the kids had fun and some of the parents thought it was a good project. Just for fun I built a circular compound parabolic collector out of cardstock and silver paint, which concentrated light sufficiently to burn the skin of your hand.

I own a patent http://www.google.com/patents/US6966661 of my own invention related to solar energy collection (though not directly related to solar cookery), and in developing that invention I learned a great deal about solar energy that will be relevant to this project. For example, I understand Roland Winston's compound parabolic concentrator (http://en.wikipedia.org/wiki/Nonimaging_optics#Compound_parabolic_concentrator) very well, and also understand the theoretical use of waveguides and fiber optics.

Basic physics of heat and energy do not elude me; I have a certain judgment about what will function and am capable of doing the math to work out the actual expected performance of a particular system, to a first order approximation (reality tends to be more complicated than theory, which is why engineering is interesting.)

I can build computer simulations of almost anything including a solar oven/cooker like I would like to build or that others may suggest. I have a PhD in Computer Science, and am a professional programmer including a solar oven/cooker like I would like to build or that others may suggest. I am pretty good at working with aluminum (due to my experience with the Mefluke, mentioned previously in the blog.)

I enjoy teamwork and cooperation, and motivating a team, although I don't claim to be a master of it.

Significantly, I'm willing to pay for whatever we need within reason.

Finally, I bring the most important and scarce resource to the table: energy and enthusiasm.