Fermilab’s Strange Letter – Progress

Note to readers: I have a little more detail (including an explanation for the spelling of “BASSE”) up at Fermilab’s Strange Letter – Interlude.

Well, now we’re getting somewhere with the strange letter Fermilab received. For context, Fermilab (a theoretical physics laboratory) recieved a strange letter in code a year ago that they’ve now released to the public. It can be seen here.

Ternary Paragraph

The first paragraph is made entirely of three different symbols, I, II, and III.

If we let I=1, II=2, and III=0 we have:

020 200 001 112 102
000 201 022 120 012
111 001 102 012 200
000 212 120 210 110
011 000 010 001 110
110 000 202 022 100
201 000 112 120 100
201 012

Note that this transcription assumes that the “I” at the end of line 6 and the “II” at the start of line 7 are in fact a single “III”. Now let’s assume that since there are 27 possible combinations in these ternany units, each corresponds to a letter of the alphabet (26 total) or a space (add 1 for 27). A naive mapping would be:

Combination Mapping 1
000 A
001 B
002 C
010 D
011 E
012 F
020 G
021 H
022 I
100 J
101 K
102 L
110 M
111 N
112 O
120 P
121 Q
122 R
200 S
201 T
202 U
210 V
211 W
212 X
220 Y
221 Z
222 (space)

This gives:

G S B O L
A T I P F
N B L F S
A X P V M
E A D B M
M A U I J
T A O P J
T F

“GSBOLATIPFNBLFSAXPVMEADBMMAUIJTAOPJTF” doesn’t seem too helpful. Perhaps a different map would be more appropriate? Let’s vary the first naive mapping slightly.

Combination Mapping 1 Mapping 2
000 A (space)
001 B A
002 C B
010 D C
011 E D
012 F E
020 G F
021 H G
022 I H
100 J I
101 K J
102 L K
110 M L
111 N M
112 O N
120 P O
121 Q P
122 R Q
200 S R
201 T S
202 U T
210 V U
211 W V
212 X W
220 Y X
221 Z Y
222 (space) Z

This is a very simple mapping, we just set space to be 000 instead of 222. We get a very interesting result:

F R A N K
S H O E
M A K E R
W O U L
D C A L
L T H I
S N O I
S E

“FRANK SHOEMAKER WOULD CALL THIS NOISE”. Frank Shoemaker worked on the main ring of Fermilab. It seems very unlikely to me that this is coincidence.

Binary Paragraph

Now if we look at the last paragraph, it’s clearly different than the first in terms of notation. Only I and II are used.

However, if we assume that “II” is a separator and “I”=1 “I I”=2, and “I I I”=0, we get the following:

012 111 121 110 120
221 012 012 000 112
210 111 002 012 200
000 002 001 201 201
012 000 201 100 220
202 012 012 112

Note that this transcription assumes an error. At the end of line 2 and the beginning of line 3 there is a section “I I I I I I I I” that is assumed to mean 000 when it should read “I I I II I I I II I I I”. If we use Mapping 2 to substitute in a manner like before we get the following:

E M P L O
Y E E N
U M B E R
B A S S
E S I X
T E E N

“EMPLOYEE NUMBER BASSE SIXTEEN” – which clicks with the hexadecimal numbers and corresponding symbols in the middle! Note that the mapping is simply the first “naive” mapping offset by one.

So lets assume the single “word” in the bottom middle of the page is an employee number. If we decode it using the symbols, we get (something)FC. (something) is an undefined symbol, and the only undefined numbers are 1 and A.

So the “employee number in base 16” that “frank shoemaker would call noise” is either 1FC or AFC.

My guess? It’s AFC (employee number 2812), who works on the AFC (Absorber Focus Coil, a component of a “neutrino factory” current being studied at Fermilab) – a coincidence Frank Shoemaker would call noise. The employee number is reasonable and fits with the established pattern at Fermilab, see this Fermilab newsletter (page 5) which states “At 802, with only three digits, Matthews’ employee number reflects the length of his 25-year tenure at the Lab”.

The only thing left is rigorously figuring out the meaning of the hexadecimal section in my opinion. What does everyone else think?

Fermilab’s Strange Letter

Note to readers: I’ve got some very interesting progress up here.

There’s a great post over at symmetry magazine about a strange letter they received a year ago, written entirely in some sort of code. The actual letter can be seen here.

Looks to be rather interesting. At first grasp, we can see that the top “paragraph” seems to be in some sort of base-3 notation (either 1, 2, or 3 lines in a group), and the bottom paragraph in a similar manner seems to be in base-2.

The middle section seems to correspond somewhat with hexadecimal digits, and there are three letters from the code above the “last” paragraph. If we take it to be a partial code, it spells out “SFC” – the only SFC I could find in relation to Fermilab (who publish symmetry magazine) was the quasi-related Societe Francaise de Chimie. I’m thinking dead end, anyone else have any other bright ideas?

Rough work follows:

Top paragraph, grouped by line:
(3,2,3,2,3,3,3,3,1,1,1,2,1,3,2) (15 total groupings)
(3,3,3,2,3,1,3,2,2,1,2,3,3,1) (14 total groupings)
(2,1,1,1,3,3,1,1,3,2,3,1,2,2,3,3) (16 total groupings)
(3,3,3,2,1,2,1,2,3,2,1,3,1,1,3) (15 total groupings)
(3,1,1,3,3,3,3,1,3,3,3,1,1,1,1) (15 total groupings)
(2,1,1,3,3,3,3,2,3,2,3,2,2,1,1) (15 total groupings)
(2,3,2,3,1,3,3,3,1,1,2,1,2,3,1) (15 total groupings)
(3,3,2,3,1,3,1,2) (8 total groupings)

Top paragraph thoughts: total number of groupings, 113. 113 is a prime number, this may be significant. Is there any significance to the fact that the numbers on the second and third lines are 14 and 16 instead of 15 and 15? In decimal notation this would be 720113244210716512990341782103795379056660114385796527.

Middle paragraph, grouped by line, hex only:
(F,0,B,E,5,8,F,2,F,D,6,3) (12 symbols/hex digits)
(6,C,7,9,D,2,E,4,9,3,E,6) (12 symbols/hex digits)

Middle paragraph thoughts: Why are there symbols at all? This appears to be information duplicated in two codings. Hex digit frequency (digit-freq): 0-1, 1-0, 2-2, 3-2, 4-1, 5-1, 6-3, 7-1, 8-1, 9-2, A-0, B-1, C-1, D-2, E-3, F-3. In decimal notation this would be 74506518313470710988407084006.

Random line: S (unknown symbol?), F, C. Why is there a symbol there, directly after definition of symbols, that is not defined? Is it the undefined hex digit A? Is it significant that the “beginning” is defined?

Bottom paragraph, grouped by line:
(1,1,1,2,1,2,1,1,2,1,2,1,2,1,2,1,2,1,1,2,1,2,1,2,1,2,1,1,1,2,1,2,1,1,2,1) (36 groupings)
(1,1,2,1,1,2,1,1,2,1,2,1,1,1,2,1,2,1,1,2,1,1,1,2,1,2,1,1,2,1,1,1,2,1,1,1,1) (37 groupings)
(1,1,1,1,2,1,2,1,2,1,1,2,1,1,2,1,2,1,1,1,2,1,2,1,2,1,2,1,1,1,2,1,1,1,2,1,1) (37 groupings)
(2,1,1,1,2,1,2,1,1,2,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2) (37 groupings)
(1,1,1,2,1,1,2,1,1,1,2,1,1,1,2,1,2,1,1,2,1,1,1,2,1,2,2,2,1,1,1,2,1,2,1,1) (36 groupings)
(1,2,1,2,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,2,1,1,1,2,1,2,1,2,1,1,1,2,1,1,1) (37 groupings)
(2,1,1,2,1,1,2,1,1,1,2,1,1,2,1,1,1,2,1,1,2,1,1,1,2,1,2,1,1,2,1,1,1,2,1,2) (36 groupings)
(1,1,2,1,2,1,2,1,1) (9 groupings)

Bottom paragraph thoughts: 265 total groupings, prime factors are 5 and 53. In line 4, 2111 repeats 6 times, the square root of the number of groupings in the first line. 1 occurs 179 times (prime number), 2 occurs 86 times (prime factors 2 and 43). 2 never occurs more than once, and 1 occurs either as 1, 11, or 111. In decimal notation this would be 4785997412726154595979555835418260996622867313584208882680343839351760783444564.

Assuming “II” is a seperator, the last “paragraph” reads:

(3,1,2,1,1,1,1,2,1,1,1,3,1,2,1) (15 numbers)
(2,2,2,1,3,1,2,3,1,2,3,4) (12 numbers) (4 at end)
(4,1,1,2,2,1,3,1,1,1,3,3,2) (13 numbers) (4 at beginning)
(3,1,2,2,3,3,3,3,3,3) (10 numbers) (long streak of 3s)
(3,2,3,3,1,2,3,1,3,1,2) (11 numbers) (multiple “II”s after each other)
(1,1,2,3,3,3,2,3,1,1,3,3) (12 numbers)
(2,2,3,2,3,2,3,1,2,3,1) (11 numbers)
(2,1,1,2) (4 numbers)

88 total numbers, prime factors (2*2*2*11). New problems: the 4s. We haven’t seen this before. Also, if 2 is a seperator, why does it separate nothing near the end of line 5? I’m not sure if this is the correct approach.

How to Select a Memory Foam Bed Frame

So you’ve carefullly selected memory foam and base foam layers? All that’s left to do is find out if your current bedframe is appropriate for a memory foam mattress!

This is a very underemphasized step – if you have an inappropriate bedframe, your comfort and the life of your memory foam mattress can be significantly reduced.

What do I use?

Your bed frame needs to be a flat surface that doesn’t bend or move. This can be anything from the floor, to some box springs or platform beds.

The floor isn’t the best choice. Simple hygiene dictates that it’s going to be rather difficult to clean the carpet near the bed, plus little things like spilling a glass of water become a far larger issue than they need to be.

A box spring may work, as long as it provides a flat surface that doesn’t yield. Five points of support are the suggested minimum (posts at all four corners, and one at the center). If you can push on the middle of the boxspring and it transfers this load nicely to its supports without deflecting appreciably, it’s probably a good fit. Don’t use boxsprings with padding, that have a “spring” to them, or that clearly deflect when you apply load to them.

What I did

malm

I used a simple platform bed like the MALM bed shown on the right from IKEA. To ensure five points of support, I put a few textbooks (hey, I was on a budget) under the center beam.

There is also a choice between rigid and flexible supportive bed slats, pick the rigid ones.

The Base Foam Layer

The base foam is a critical part of your memory foam mattress. No matter how luxurious the memory foam top layer, cutting corners on the base layer will produce an unsupportive and uncomfortable bed.

There are a huge variety of foam base layers you could use. Most manufacturers use polyurethane foam in the base layer, so this discussion is limited to that product. I would be interested to hear from people who have used other foams, especially latex.

Be careful of exceptionally good deals – the foam could be low density, or a cheaper layered construction. We’re looking for one giant chunk of foam. If there is a foam supplier in your area, this is usually your best option.


Density

This was discussed extensively in differences between memory foam, so I’ll keep it short here. Typically, high end memory foam beds will use 2.2 lb/cf polyurethane open-cell foam as the base layer.

Luckily enough, this is one of the most common foams used for basic foam mattresses! So, all we need to do is buy a foam mattress which meets or exceeds these specifications. Look for a minimum of 2.2 lb/cf, and a firmness rating of at least “medium”. This is the major load bearing part of the bed. The memory foam distributes the pressure evenly, but the base layer distributes the load to the bedframe. Without a quality base layer, the mattress will sink and sag – no good!

What I Did

sultan

I used a Sultan Fangebo foam mattress from IKEA. This mattress is a solid chunk of 3.5 lb/cf foam, and is found to be medium to firm by most reviewers. There’s just one problem – IKEA appears to have discontinued this model. The newer ones use cheaper foam in layers, which isn’t really what we’re looking for at all.

The good thing is that what we’re looking for is dead simple – a roughly 6″ thick layer of 2.2 lb/ft3 polyurethane foam cut to standard mattress sizes. Check out foam distributors online if you can’t find one in your area.

The Memory Foam Top Layer

Now that you know what memory foam is, the differences between memory foams, and some possible issues, it’s time to select a memory foam top layer for the bed.

What We’re Looking For

All of this wouldn’t be much good if they didn’t sell memory foam by itself. Luckily enough, they do – as mattress toppers. We know we’re looking for open-cell viscoelastic polyurethane foam, with a minimum density of 5lb/ft3 (80 kg/m3) . It should be reviewed well for comfort, as well as come with a wicking cover to ensure comfort in humid or warmer conditions.

The only thing left to decide is size and thickness. Mattress size is completely up to you, but I suggest getting as much quality memory foam as you can afford. A thickness of 4 inches appears to be the sweet spot in terms of cost versus benefit. Anything beyond that provides little benefit, and cost increases drastically.


What I Did

I’ll save you the research trouble, and just tell you who I found that satisfies our conditions. That’s not to say there aren’t a ton of vendors out there with great products – this is simply one I’ve used personally and can vouch for. Finding the best deal at any given time is going to be a little bit of work – prices and products change rapidly, but at least your evaluation method will not.

In 1Q 2008 when I built my bed, Bergad Inc’s Isoform mattress division provided a very high quality, well reviewed memory foam for a very reasonable price. I purchased a 4″ queen mattress topper with a wicking (“CoolMax”) cover for approximately 215 USD. The price has increased since that time, but remains a very good value. As of the time I ordered, shipping was free to the US and Ontario. I cannot vouch for any other provinces as I live in Ontario, but to be frank I cannot believe I was not charged extra (or anything!) for cross-border shipping.

I would not recommend Ebay or other assorted sites. The deals present can be matched easily by careful shopping with more established merchants, and any deals “too good to be true” usually are. The advantage of having a company you can phone up and contact for issues such as warranty is invaluable. Here are some major manufacturers to get you started.

Manufacturer
Details
Bergad Two parts: the retail Isoform side, and the wholesale Bergad Specialty Foams and Composites Division which produces wholesale foam and unique products such as glow in the dark memory foam.
Carpenter The “largest manufacturer of comfort cushioning in the world”. Produces the Isotonic line of memory foam products for consumers, but the majority of their memory foam is sold to other manufacturers.
Essentia Canadian based memory foam manufacturer. Does not use the typical polyurethane approach, but instead has developed a process to add viscoelastic properties to latex foam.
Foamex A large manufacturer of foam products, including the Venus, Aerus, Energia, and Sensus memory foams. Currently restructured due to bankruptcy, the future of these products is uncertain.
Sleep Innovations Best known for its Novaform line, they also produce a wide range of products for private labels at retailers like Target, Sears, Kohl’s, Costco and Sam’s Club. Also produced the deeply ironic “Cuddly Comfort” pillows that were recalled for containing jagged metal bits.
Tempur The original. This is on here only for completeness and comparison’s sake – their memory foam toppers are ludicrously expensive.

There are actually very few companies manufacturing their own memory foam, and even fewer who do it domestically. Foam is rebranded and resold, and it can be very difficult to trace where your memory foam product really came from. If you’re aware of other companies that actually make their own foam as opposed to brokering it through other sources, please leave a comment!

Miscellaneous Issues

There are a few things you should be aware of. One, the thing is going to be heavy. Remember our density calculations in the differences between memory foams section? A 4″ queen topper will be almost 60 pounds! Make sure you’re home the day of delivery so you don’t have to go pick it up yourself, and let the delivery guy drop it in your bedroom, not your front door. This isn’t a major issue for younger people, but if you have difficulty lifting and moving heavy awkward objects, recruit a helper!

roll-t0

roll-t20

Additionally, memory foam, due to it’s open-cell foam structure, can be compressed quite compactly. This saves on shipping, but often causes people to get confused when they see a compressed shrinkwrapped thing that looks more like a Pilsbury roll than a mattress cover. It will take several hours for the topper to unroll itself and expand. Don’t attempt to “stretch” it back into shape, you could damage it. Just let it be. As the pictures show, it can take a while, especially if delivered in the cold which will cause the memory foam to stiffen up significantly.

The mattress topper cover can be a pain to put on too. Easiest way I found way to lay out the cover flat, put the mattress topper on one side of it, then fold the cover over and zip it up. The weight of the mattress topper makes typical approaches to zipping it up very awkward.

Remember there will be a mild odor to start. My mattress topper had no appreciable odor after 2 days.

What are Some Possible Issues With Memory Foam?

While personally I find memory foam to be an amazing sleeping surface, there are some issues that you should be aware of.

Memory Foam Feel and Personal Preference

Memory foam is a unique material. As a result, it doesn’t feel like any other bed you’ve slept on before. While many people love it, some simply can’t get over the “sinking” or “trapped” feeling. Others love it! It’s a very personal response, which is why I recommend you try out memory foam products in person before you order to make sure you’ll enjoy it.

So you’ve tried out memory foam and love it – but what about your spouse or sleeping partner? Make sure that they like it as well! One of the easiest ways to pick up a full memory foam bed on the cheap is to keep an eye on classified ads, the story always seems to be that one person loved it, the other hated it. Don’t bet on this method however, it’s a rare find but worthwhile considering if you can verify the age of the mattress (ie a few days via receipt) and condition.


Heat

Memory foams conform to your body incredibly well. While generally a good thing, if you live in a warm climate or are a hot sleeper you may have issues with a memory foam bed.

Possible solutions to this are “wicking” covers which are similar to those used in athletic uniforms, and high air flow foams. “Wicking” covers pull away sweat and moisture keeping you dry and comfortable, and are recommended for a “build your own” bed. High air flow foams have larger open-cell “bubbles” (see What is Memory Foam?) which allow increased air circulation. This approach is typically only found in more expensive multilayer beds, and is difficult to mimic yourself without
considerable expense.

Odor

There is a distinct memory foam “smell” that is given off in the first few days the new product is used. Some vendors have minimal smell, others have overwhelming odor which can cause allergic reactions. It is a result of volatile compounds (chemicals that can become gases which your nose then picks up) in the polyurethane foam mix. A certain amount of these volatiles is an unavoidable part of the manufacturing process, but a large amount is indicative of poor quality or process controls.

High quality memory foams generally have less odor issues than low quality foams. If you are mildly allergic, let the memory foam air out for 3-4 days. If you are severely allergic, you may not be able to sleep on a memory foam bed at all, or you may have to consider the new “green” memory foams which have been recently developed.

What are the Differences Between Memory Foams?

Memory foam refers only to the “viscoelastic” behaviour exhibited by the foam. Memory foams can encompass a wide range of quality, durability, comfort, and other characteristics. Here’s a few things you should look for when considering the purchase of a memory foam product.

Density

This is the most reported memory foam specification, and while it isn’t perfect, it’s the one you
should look at most.

Density refers to the weight of a given volume. For instance, higher quality memory foams weigh
approximately 5 pounds per cubic foot (80 kg/m3) of volume or more. The reason density is a relatively good indicator is for two reasons:


First, memory foam density is typically increased by increasing the amount of additives to the foam mixture. These additives usually give it it’s “memory” effect. The higher the density, the better and more obvious this “memory” effect appears. Low density memory foams will deform quickly, and rebound equally as speedily. This means they will tend to feel more like “regular” foam and less like “memory” foam.

Secondly, increased density generally correlates with improved mattress life. Higher density foams will tend to last longer, and will not “collapse” or form dents where you sleep.

Note that softness was not mentioned! Remember, styrofoam has an extremely low density but would not be comfortable to sleep on. Lower density foams may be sold as "softer" but what they really are is simply a cheaper option for the manufacturer.

Be careful! Some unscrupulous dealers will put large meaningless numbers on their product which you may mistake for the density. Others may report the density as “pounds per TWO cubic feet” which has the nice effect of doubling the final number – but is a shameless attempt to deceive you. It is easy to check this – simply calculate the volume of your mattress, multiply by the density, and it should be quite close to the shipping weight. If it’s off significantly, this is a warning sign!

For instance, a 4″ thick queen mattress is 202 cm by 152 cm by 10 cm (yes, I’m from Canada). This gives us a total volume of 307,040 cubic centimeters, or ~10.8 cubic feet. If we assume it is made of 5lb/ft3 (80 kg/m3) memory foam, this means it should have a shipping weight of approximately 54 lbs (25 kg). A little bit either way shouldn’t be an issue, but significant deviations from this should be a warning sign.

I personally would not reccommend anything less than a density of five pounds per cubic foot. While this does eliminate a large number of products, it is still quite possible to obtain reasonably priced memory foam at this quality. This is a similar density to that used by high end memory foam beds (typically greater than 5lb/ft3 (80 kg/m3)).

Indentation Load Deflection

Specifications like this give engineers a bad name. While a valiant attempt at quantifying how “soft” a mattress is, the extraordinary variation in mattress composition and thickness makes it very difficult for a single number to accurately reflect a general quality like “softness” or “comfort”. Even if these numbers are produced, it then becomes difficult for the average person to say what number they prefer, and accurately compare between mattresses. It’s an extraordinary precise number that manages to be nearly useless from a consumer standpoint due to it’s precision. As such, the ILD is largely a quality control measure, more valuable to the manufacturer than the consumer.

ild

The test itself uses an “indenter”, shown on the right. This typically has a contact area of 50 square inches. The test involves pressing this indenter a specified distance into the foam, then measuring the force required to do so. A typical test is 25% deflection for a 4 inch sample, which means that the sample is compresses from 4 to 3 inches and force measured.

I don’t put much weight on this number for two main reasons. First, comparing ILD values is really only useful for foams with similar properties and manufacturing. Our entire intent is to compare between manufacturers, so this means ILD will give us little information.

This leads into my second point – it’s an extraordinarly limited test, initially designed for classic “elastic” foams. The major characteristic of memory foams is their viscoelasticity, which means that its response to load varies over time. The ILD test does not take time into account, which is fine for conventional “elastic” foams but completely misses the point of viscoelastic memory foams. As such, I do not view ILD as a useful “consumer level” metric. Choose based on comfort reviews and testimonials, not a single number.

Other Numbers

There’s a ton of different ways to measure foam, and as a result there’s a ton of numbers thrown around. They mean very little unless you are a chemical engineer dealing with the manufacture of these foams. The major measurement a consumer should pay attention to is the density, and following that reviews and testimonials on comfort.

Nerd alert: there are two valuable tests (creep and stress relaxation) typically done on viscoelastic materials that I haven’t bumped into for memory foams. If anyone has any quality data in this regard please contact me or post in the comments below.

What is Memory Foam?

Memory foam is actually a rather advanced material, and has only gone down in cost enough to be practical for personal use in the last ten years or so. More specifically, it is an open-cell foam with viscoelastic properties, typically manufactured using polyurethane. If this means nothing to you don’t worry, and read on!

Open Cell Foam

opencell

We can think of foam as a fluffy mixture of a solid (polyurethane in this case) and air. If the mixture is made up of many tiny bubbles, like in the sole of a tennis shoe, we can squeeze and compress this foam and the air will never come out as long as the bubbles don’t break. This is called closed cell foam, and is good for tennis shoes which need to protect our feet from harsh impacts again and again, but tends to be a bit stiff for beds.

Open cell foam is still a mixture of a solid and air, but in this case, all the little bubbles have even smaller holes in them! We can see this on the magnified picture on the left. This means we can squeeze and compress the foam a great deal, as the air will rush out just like water from a foam dish scrubber when you squeeze it.

This open-cell foam is soft and conforming to the body, and allows air movement through it which helps keep you cool and comfortable.

Viscoelasticity

Viscoelasticity is what makes makes memory foam have a “memory”.

A spring mattress is what engineers would call elastic. No matter how fast or how slow you put a certain load on the mattress, the spring still compresses the same amount in the end. The spring does not (or at least should not) soften or harden over time.


A memory foam mattress is what engineers would call viscoelastic. This is a combination of elastic properties (like a spring) and viscous properties (like oil or molasses). These viscous properties cause the foam to react differently depending on how fast you put weight on it. If you jump onto a memory foam bed, you can feel the foam slowly start to conform to your body as you sink in. If you get up quickly, there will be a dent in the foam in the shape of your body which will slowly disappear over time.

So who cares? Is a memory foam mattress just an expensive way to leave a cool handprint? Well, there’s more to it. Sleep comfort can be correlated with how pressure varies along the body during sleep. If the pressure changes rapidly with many individual pressure points (like sleeping on gravel, or that one spring that pokes out of the mattress), we’ll be very uncomfortable.

Memory foam does a very good job of reducing these “stress gradients”. Over a short period of time, the foam remolds to reduce these pressure points, something a typical elastic material cannot do. The resulting smooth pressure distribution provides a very comfortable sleeping surface.

Polyurethane

polyurethane

Without getting into too much chemistry, polyurethane is a polymer. This means it consists of very long chains of urethane molocules, which then become tangled together like spaghetti to produce a solid. To produce basic polyurethane foam, a reaction occurs where urethane is chained together into these long strings while water reacts with another compound to produce carbon dioxide. This combination of solid and gas gives us polyurethane foam.

One important advantage of polyurethane is that its properties are readily modifiable by adding different compounds to the mix. Typical polyurethane foam is not “memory” foam unless certain additives are incorporated which give it these “memory” effects.

Make Your Own Memory Foam Bed

High quality memory foam beds such as the Tempur line are incredibly comfortable, with a price tag of thousands of dollars to match. The construction of these beds is relatively simple however, evidenced by the number of “clone” beds on the market today. Unfortunately, some of these mass-produced “clones” have cut corners in quality, which can make selection challenging.

This page will tell you the typical components of memory foam beds, with instructions on how you can mimic each of these components with high quality substitutes. The cost savings can be significant.

For instance, I currently sleep on a queen size memory foam bed constructed in this manner. It cost me approximately $500, versus a memory foam mattress with comparable specifications which would have put me back over $1500.

It’s a lot easier than you might think – you need three layers. The major issue is quality control and determining the appropriate products which are the best value for each layer.

main-memory-foam


sub-memoryfoam Memory Foam Layer
This contouring soft upper layer is what gives memory foam mattress their unique “feel”.

sub-foam Base Foam Layer
This layer provides a supportive base which distributes your weight evenly across the bed.

sub-base Platform Layer
A sturdy flat base supports the memory foam mattress and prevents a “hammock” effect.

The Black Beauty

As the summer progressed, I felt like I needed to improve my initial design. Luckily enough the science department had just thrown away an old freeze drying machine which had a perfect radiator. A few minutes crouched by the dumpster with some hand tools, some minor adjustments, and the Black Beauty was born.

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Here’s the overall view of the unit. A high speed fan pushes the air through the perfectly sized radiator, and water flow rate is controlled by a small hand valve.

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The radiator itself was horribly filthy when I first took it off, but a quick soak in some warm water and light detergent took care of it. The copper tubing inside the radiator is the exact same diameter as the copper tubing I used when I first built my original homemade air conditioner, so no need to change up the vinyl tubing.

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I placed the fan fairly close to the radiator itself, and it works great. I typically put the fan on the medium or low setting, as I notice little benefit from the high speed setting other than increased noise.

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The radiator was almost perfect, it only needed to be raised by a centimeter or so to align with the fan. Turns out old original Nintendo cartridges do the trick just fine. (For the record, that’s Teenage Mutant Ninja Turtles and Marble Madness. Don’t worry, I have other copies.)

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Cold water is supplied from an outside garden hose. More detail can be found in the water supply section.


To calibrate the valves, the small hand valve inside is first opened wide and the garden hose opened or closed to find an appropriate upper flowrate. Then the hand valve may be used to vary the water flow or turn it off entirely.

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The nice thing about this new setup is that all control is now done from inside the room. Starting and stopping the unit is far more convenient, which leads to more efficient water usage. The performance of the unit is drastically improved over the old design. Less water is needed, and the room cools quicker.

Homemade Air Conditioning Plans and Pictures
Original Design
Geoff’s Homemade Air Conditioner
Heat Exchanger Improvements
Water Supply Improvements
Technical Notes
Other Designs
Pete’s Homemade Air Conditioner
Anonymous’ Homemade Air Conditioner
Spencer’s Homemade Air Conditioner
Final Design
The Black Beauty