Making it Cheaper!

One of the important things I learned from the VIUD's KickStarter was that its price was on the high end so finding a way to reduce that price is now at the top of my list of things to do. At first glance it may appear that there is little that can be done...the prices used on the KickStarter were the lowest I could get them at the time but there are a few areas we can look at and perhaps their combined effect can result in a notable price reduction.

Sales Method

Using KickStarter as the sales method introduces a not insignificant amount of overhead on the price which includes:

• KickStarter fee (5%)
• Credit card fees (3-5%)
• International shipping

If we compare the VIUD's prices from the KickStarter and without this overhead we can see a good sized difference:

Model	KickStarter Price	Base Price
Al 16GB	$199	$151
Al 32GB	$219	$164
Al 64GB	$249	$183
Al 128GB	$299	$241
Al 256GB	$419	$346
Ti 16GB	$319	$250
Ti 32GB	$349	$264
Ti 64GB	$399	$282
Ti 128GB	$449	$340
Ti 256GB	$599	$445

The effect is more significant in the more expensive models...the 256GB Ti is already over $150 cheaper! 

Technically some of this overhead, namely the credit card and shipping fees, will have to be included at some point but removing them from the VIUD's list price is an important step. 

Case Material

We can evaluate the case materials to see if any trade-offs can be made regarding price. The current two case materials, Aluminum 7068-T651 and Titanium Grade 5, were chosen as they are among the highest strength alloys of the respective material. Unfortunately, this also means they are more expensive than other alloys. 

Comparing a few common alloys:

Alloy	Tensile Strength	Cost
Al 7068-T651	95 kpsi	Low-Medium
Al 7075-T6	75 kpsi	Low
Al 6061	35 kpsi	Low
Ti Grade 5	120 kspi	High
Ti Grade 2	40 kpsi	Medium-High

For the Aluminum VIUD we can consider moving to Al 7075-T6 as this alloy is still very strong and it can make the case manufacturing price a bit cheaper. Experience has also shown that it is much easier to find a machine shop able to source and work with 7075 than 7068. For the Titanium VIUD we will stick with Grade 5 as the more common Grade 2 is significantly weaker and we can have the Titanium VIUDs be a "premium" model to match its higher price.

Case Manufacturer

The VIUD's case is the largest portion of its manufacturing cost comprising 50-80% of its total. I've already sourced a bunch of machine shops for the case production and choose the cheapest one. At least the cheapest one that was able to make the case and not screw up royally. There was one, unmentionable, shop that failed miserably but did offer much lower prices. Perhaps another search and production test will reveal a shop with a lower price but still good quality production.

To make a long story short, I found a few dozen potential shops and ordered VIUD case samples from four of them for evaluation purposes. All four shops had lower prices than my previous manufacturer and 3 of the 4 managed to supply cases with pretty decent qualities as seen in the below pictures:

Case Manufacturer A

Case Manufacturer B

Case Manufacturer C

Case Manufacturer D

Three of the manufacturers supplied pretty much identical parts with very good quality. Manufacturer A was the notable exception with completely unusable quality, literally! The threads were so bad they wouldn't screw together even after trying to fix them. You'd think you would want to do your best work when making samples for a potentially larger order.

Potentially Good News....

I still need to fully test the VIUD case samples from the newly sourced manufacturers to make sure the cases are worthy of being used in the world's toughest USB drive, but it looks promising at this point. Based on the average quoted price of the 4 suppliers I should be able to get the list price of the cheapest VIUD model (Al 16GB) well under $100 which should make it much easier to convince people to buy it. 

KickStarter: Lessons Learned

While the VIUD's KickStarter campaign was not successful it was still useful in what I learned in from the process. 

Video Making

Prior to starting the campaign I had done basically no video capturing or editing. All KS campaigns require a decent looking introduction video so I started practising by making a variety of VIUD testing and documentation videos which I put on the VIUD's YouTube channel. I quickly found a few important things about making videos:

• Lighting -- Even getting half-decent lighting for a simple video can be difficult. Partial sun in the video is no good as it ruins the video's contrast/brightness levels and stands out too much. Direct bright lighting is bad as it tends to reflect off my glasses horribly. I found that using some high-intensity halogen work lights reflecting off a wall or ceiling gave a decent effect with little effort.
• Background Sounds -- I didn't realize how loud all the various background sounds could be until I tried to make a few videos. I live near a school, busy road, and plane route and it was a challenge to record a video outside that didn't have some sort of background noise interrupting it.
• Public Speaking -- I've never been a good public speaker and that much was obvious from the first few video takes. I've since practised speaking more slowly, carefully pronouncing words and trying to keep the inevitable "ums" and "ahs" to a minimum.

The first few videos definitely took more than a few takes to get just right than the recent ones.  I'm particularly proud of the KS campaign video (see below). It won't win any awards and is not as nice as some other KickStarter videos but represents something I couldn't do prior the quest for the VIUD.

VIUD KickStarter Campaign Video

In addition to the video creation I've also had to learn some basic video editing. For now Windows Movie Maker was sufficient to create my basic videos and I've had to learn things like joining movies, transition effects, recording and adding a voice over, sourcing and adding music, and basic credits. Nothing fancy but definitely a little learning curve there. If I had to make more videos I would definitely want to look into getting a better video editor. 

Marketing

I'll readily admin that I'm first and foremost an engineer/physicist and have little to no marketing/sales knowledge or experience. While I tried a little promotion of the VIUD shortly before I started its KickStarter campaign I quickly found out I did far too little and much too late.

I found a few companies after I launched to help promote the campaign, for a price of course, and I wish I had known about them before hand. One was BackersHub which sends out an email newsletter to inform their clients about KickStarter campaigns and offer deals to some of them. Another one, Ayudos, offered a press release and promotion on their social media accounts. In addition I spent a lot of time after the campaign started trying to contact sites and reporters who might be interested in the VIUD and its story. I also ran a Google AdWords campaign that at least resulted in a lot of traffic to the campaign and blog.

Unfortunately, my few attempts at marketing didn't yield very much. In hindsight I should have begun aggressively marketing the VIUD and its KS months before the campaign actually started. This would have given me a much larger audience and a better chance at getting the required funding. 

Price

The high price of the VIUD was definitely a significant barrier in getting people interested in purchasing it. Part the problem was that the KickStarter price includes the KS fee, credit card fee, and shipping. For example, the cheapest VIUD (Aluminum 16 GB) might have listed for $150 on an online store with a good profit margin but on KickStarter the additional fees bumped that price up to $199 or more. The $179 early bird price I was offering gave me almost no profit.

Reducing the cost of the VIUD mostly involves reducing the manufacturing cost of the case itself. On the 16 GB model the case is currently 80-90% of the overall manufacturing cost. I've already got quotes from a half-dozen different manufacturing shops and the one I've chosen was actually the cheapest by a good margin. There was a considerably cheaper one but it failed to supply anything usable by a spectacular margin.

This leaves me with the unenviable task of looking and trying out a few more case manufacturers to see if I can get a better price.

The Next Step...

After spending a solid two months almost exclusively on the VIUD and its KS campaign I took a short break for a few months in order to get caught up on all the other work I have to do (or had been ignoring in other words). I'll be looking for new suppliers for the manufacturing of the VIUD case to see if I can get the price lower for another attempt.

I've considered trying another KickStarter campaign (you can simply create a new project to try again) but I'm not so sure that KickStarter is a good choice for this type of product. I'm more leaning towards just purchasing a few hundred initial VIUDs and creating a simple web store to sell them from. Either way will take a little more consideration to decide exactly what to do.

An Interesting Question

The following question is one that I was wondering about recently:

At what height can the VIUD be dropped from and survive?

To answer this relatively simple question will take us down a variety of interesting paths which were not obvious at first. To consider how our USB drive may survive we need to first look at failure mechanisms from dropping it from a considerable height:

• Impact -- Drive fails when hitting the ground.
• Temperature -- Drive fails due to heating from travelling at high velocity in air (like a meteor).

We'll first consider the impact failure mode since if the VIUD can't survive the ground impact we won't have to worry about temperature effects at higher speeds.

Terminal Velocity

To consider whether our drive will survive impact with the ground when dropped from a given height we need to consider its terminal velocity. When an object is dropped in air it has two forces on it: the force of gravity down and the force of air in the opposite direction. The force of gravity on the object is essentially constant but as an object travels faster the the force of air resistance gets higher. At some point the force of air resistance equals the force of gravity and the object stops accelerating and reaches its terminal velocity.

The terminal velocity of an object is expressed in general as:

where:

V_t = Terminal Velocity in m/s

m = Object's mass in kg
g = Force of gravity in m/s²
ρ = Density of air in kg/m³
A = Projected area of the object in the direction of motion in m²
C_d = Drag coefficient

Most of these parameters should be straight forward with the exception of the drag coefficient. Depending on the shape of the object its drag will be more or less which in turns affects its terminal velocity. We can use the measured coefficients of known shapes to estimate what it will be for our VIUD:

• Long Cylinder = 0.82 (direction parallel with axis)
• Short Cylinder = 1.15 (direction parallel with axis)
• Cylinder = 1.17 (direction perpendicular with axis)
• Sphere = 0.47

Depending on how our rugged drive falls it could have a drag coefficient anywhere from 0.82 to 1.17. Since the coefficient is inversely proportional to the terminal velocity the smallest coefficient will result in the largest, or worst case, terminal velocity so we'll use C_d = 0.82 for the rest of the calculations.

Plugging in all our values (assuming worst case in everything):

m = 0.06 kg

g = 9.8 m/s²
ρ = 1.22 kg/m³
A =  0.00041 m²
C_d = 0.82
V_t = 54 m/s (195 km/hr, 121 mile/hr)

From this estimation we know that no matter how high we drop our USB drive it should hit the ground at a maximum of 54 m/s.

Terminal Velocity as a Function of Height

Our previous calculation was only interested in the VIUD's terminal velocity at ground level but for the next step we will need to know its terminal velocity at any given height above the ground. Since the density of air drops as we go higher the estimated terminal velocity will increase as higher altitudes.  

We first need to find the density of air as a function of height. We can use an analytic equation for the density of air within the troposphere, or roughly up to 15 km in height and there are also a variety of more complex air density calculations if you look for them. What we'll end up using is simply a table of measured air densities which also conveniently has the force of gravity which does decrease slightly within the first 100 km. More detailed tables are also available if you need finer altitude steps.

Using this air density table and the same VIUD parameters as before yields the following graph of the terminal velocity versus altitude:

We can assume for simplicity that above around 100 km the air density is so small that there is no effective terminal velocity.

Velocity of a Dropped Object as a Function of Height

The next step in the modelling is to figure out what the velocity profile of an object dropped at a specific height is. Assuming the object is dropped far from the surface of the earth there will be three basic areas to consider:

1. Space - No terminal velocity.
2. Upper Atmosphere - Terminal velocity begins to drop rapidly.
3. Lower Atmosphere - Object reaches a steady velocity of 54 m/s.

To determine acceleration in space we simply need to know the force due to gravity from Earth (we'll ignore all other astronomical bodies for simplicity):

where:

g_o = 9.8 m/s²

r_e = Mean radius of earth, 6371 km
h = Altitude above the mean radius of Earth in km

While the object is in space computing its velocity is relatively straightforward. The fact that the force of gravity increases as its approaches Earth makes it more complex but it can be solved with a simple numerical integration at regular intervals from the drop height to 100 km where the terminal velocity begins to take effect.

To figure out the net acceleration of the object once it hits the atmosphere we'll need to know the drag force which is where the prior terminal velocity equation was derived from:

Our net force on the falling object within the atmosphere is then expressed as:

F_net = mg_h - F_d

Since both the force of gravity and terminal velocity depends on height we'll keep doing a numerical integration solution. Graphing the velocity versus altitude for a couple of different drop heights yields the following velocity profiles:

Assuming we did everything correct in the solver the graphs appear to make sense. As the object falls in space it continuously picks up speed until it hits the atmosphere at around 80-100 km. From there its velocity begins to quickly decline as it hits more dense air. At around 10 km it reaches its final terminal velocity of 54 m/s falling at roughly a constant speed. 

We can do a quick check to make sure our model is outputting reasonable numbers. If we use the equation for the velocity of a falling object after a given distance, sqrt(2gd), and take the force of gravity at the midpoint of the 10,000 km drop height (3.1 m/s²) we find a velocity of 7700 m/s at 100 km which is reasonably close to the model's value of 8500 m/s.

Aerodynamic Heating

We're finally at a point we can find what we're looking for: the temperature of the object as it falls through the atmosphere at a high velocity, otherwise known as aerodynamic heating. While our VIUD is a relatively simple cylindrical shape it is still too complex for a simple modelling of aerodynamic heating. Realistically we would want to do some finite element modelling but this is beyond my current capabilities so we'll have to settle for some approximations.

All the simple aerodynamic heating models I've seen have assumed a thin plate travelling with the thin edge towards the direction of motion. This isn't too far from our VIUD but since it is thicker than a plate we could assume the heating would be more severe than that of a plate (how severe is difficult to guess).

where:

T_wad = Temperature of air just beside object, K

T_∞ = Temperature of air far from object, K
r = Recovery factor, estimate for air of 0.84-0.87
M = Speed of object in Machs
 = Heat capacity ratio, 1.40

We can get the normal air temperature as a function of altitude from the same data tables we used for air density. The heat capacity ratio doesn't change far from a value of 1.4 for air until you get into temperatures above 1000^oC which is irrelevant for this model. 

From this presentation we'll use the very simple approximation to find the temperature of the USB body: 

T_net = T_air + 0.5 (T_obj - T_air) + 0.22 (T_wad - T_air)

I'm unsure exactly how they derived this but I'm assuming it is only valid for a particular model and may not be accurate at all for our case. Unfortunately, all other methods I've investigated are extremely complex and a little beyond my limited understanding of heat dynamics (we'll look at alternate temperature models in another post). Since this model depends on temperature and speed of the object we'll do a numerical integration just like for our velocity calculation which yields a graph like:

Not surprisingly there are large temperature increases when the fast moving object first begins to hit the atmosphere. While it is difficult to tell from this graph the actual amount of time spent at these temperature is relatively small: for temperatures above 1000 K only 10 seconds are spent for the object dropped at 10000 km and 19 seconds for the object dropped at 1000 km. The object dropped from further up experiences a higher temperature spike but for less time as it is moving much faster (8 km/s compared to 4 km/s).

Since the melting point of Aluminum is only 933 K (660 °C, 1220 °F) we can guess that the objects dropped above 1000 km would have significant damage, assuming they survived at all. The object dropped at 100 km experiences a much gentler temperature curve only reaching a maximum of 410 K (137 °C, 280 °F) and only being above the boiling point of water for 10 seconds. This is far below what our USB drive has survived in temperature testing so we can be reasonably sure of its survival in this case.

Although, if we were to be optimistic for the higher altitude drops, at the high altitudes the air density is very low (a million times lower than that at sea level) and the amount time experienced at high temperatures so low (temperature rating for the VIUD at 2300 K  for 40 seconds) that a more accurate temperature model could reveal the VIUD can survive drops from higher altitudes.

Conclusion (Kind Of)

Although the accuracy of our temperature results is a little suspect and unverified we have at least a reasonable guess that dropping our rugged USB drive from up to 100 km will not destroy it from temperature affects. More research into an accurate temperature and heat model needs to be done to get more accurate results, assuming we want them.

References

• Aerodynamic Heating
• Aerodynamic Heating Simulation Paper
• Aerodynamic Heating Presentation from Queen's University
• Terminal Velocity
• Drag of Cylinders and Cones
• Basic Atmosphere Data Tables
• More Detailed Atmosphere Data Tables
• Falling Bodies in the Atmosphere
• Aerodynamic Drag
• Air Density Equations
• XKCD: Steak Drop

Materials

The choice of material for our ultimate rugged USB drive is probably the second most important choice, surpassed only by the design itself. When looking for a material there are a few criterias we're interested in:

• Strong
• Light
• Cheap/easy to source
• Easy to machine
• Hard
• Low thermal conductivity

You may note that several of these are in conflict with each other. For example, "easy to machine" and "hard" are basically exact opposites as are "strong/light" and "cheap".

Wood

I only mention wood as a material since I am an experienced wood worker and love working with it. A great looking USB drive could be made out of wood but for the purpose of a rugged/indestructible drive it is a poor choice. The yield strength of wood is a complex subject but for a rough estimate it is more than ten times weaker than even a low strength Aluminum alloy (yield strength of ~5k psi).

Brass

I used Brass for the first prototype and while it is cheap and easy to machine it is also heavy (8 g/cc) and weak (yield strength of ~20 kpsi) and thus not a good candidate for our design. 

Aluminum

Aluminum seems like a good choice of a material although we'll have to look more closely at which of many alloys in particular. In general, Aluminum is light (2.7 g/cc), easy to machine, and can have yield strengths approaching 100 kpsi in some alloys. We'll look at a few of the most common alloys, particularly those with high strengths.

6063

This is a common low cost and readily available alloy but is low strength with a yield strength around 20 kpsi.  It is great for quickly testing a prototype design and I've gone through a few feet of 1" diameter 6063 rod over the design process for the VIUD including the second prototype. 

Al 7075-T6

7075  is the most common of the so called "aircraft Aluminum" alloys developed for its higher strengths. It is around twice as expensive than 6063 but for our VIUD it still only works out to around $4 of raw material per unit. 

The "T6" designation is the "Temper" of the alloy which are standards of how the metal is prepared and is a very important designation of the material. For example a 7075 non-tempered alloy has a yield strength of only 15 kpsi while 7075-T6 is near 80 kpsi. A temper of T6 indicates that the Aluminum is solution heat treated and artificially aged.

Al 7068-T6511

One of the stronger aircraft Aluminums with yield strengths approaching 100 kpsi for the T6511 prepared alloy. Price for 7068 is around twice that of 7075: getting higher but hopefully still acceptable. T6511 is a combination of "T6"  solution heat treated and artificially aged)  and "T511" (cooled from hot working and artificially aged at elevated temperatures with minor straightening after stretching).

Titanium

Titanium is also an obvious choice when creating something that needs to withstand a lot of abuse. It is heavier than Aluminum at 4.5 g/cc making it about half as heavy as Brass and Steel. Where Titanium excels is its strength with certain alloys reaching a yield strength of 140 kpsi. The downside, however, is that due to its hardness, especially with the higher strength alloys, it is difficult to machine which leads to higher production costs.

Another thing to note about Titanium is its lower thermal conductivity of 16.4 W/m-K compared to Aluminum's 173 W/m-K. This means that using Titanium for our VIUD design should render it much more resistant to temperature. Titanium is also much harder than even anodized Aluminum which further increases its usefulness as a"rugged" material.

There are a variety of alloys but we'll only look at the two most common ones, Grade 2 and Grade 5 (6Al-4V).

Ti Grade 2 

This is the softer and more common Titanium alloy with a yield strength of the annealed alloy near 50 kpsi. This makes it less than ideal as it is weaker than the 7075 Aluminum despite being more expensive to manufacture, although surprisingly probably not by much. The hardness of Al 7068 is B90 on the Rockwell scale while Grade 2 Titanium is around B98, larger but less than I had originally assumed.

Ti Grade 5 (Ti-6Al-4V)

This is the much stronger alloy with yield strengths nearing 130 kpsi for the annealed version and approaching 170 kpsi for surface treated alloys. The price for this strength is its machining difficulty and high material cost, about four times that of 7068-T6511 making the material cost per unit around $25.

Review

The following table summarizes the important material properties we've been discussing:

Material	Density g/cc	Yield Strength psi	Heat Conductivity W/m-K	Hardness Rockwell
Aluminum 6063	2.8	20,000	200	B30
Aluminum 7075-T6	2.8	65,000	200	B80
Aluminum 7068-T6511	2.8	95,000	200	B90
Brass 360	8.5	20,000	110	B25-B80
Titanium Grade 2 Annealed	4.5	40,000	16	B98
Titanium Grade 5 Annealed	4.5	120,000	7	C36
Wood, Maple	0.7	6,000	0.7	N/A

The obvious choice of material is the Aluminum 7068-T6511 with 7075-T6 being a close runner up. Grade 5 Titanium is great but will end up being very expensive to use and perhaps is better used for a "special edition" version with a higher price.

Resources

Some of the online resources I found useful for material property references are listed below:

• Matweb Material Reference Library
• Aluminum alloy material reference
• Titanium alloy material reference
• Titanium Grades 

Temperature Testing, Round One

So far we haven't done any temperature testing other than the failed attempt with the first prototype and a propane torch which melted the USB connector's plastic. Our investigation into being the toughest USB drive in the world showed that a good temperature rating is one thing we are currently lacking.

We will perform some initial temperature testing with the one of the third prototypes which has been destined for eventual destructive testing, although we will try to be careful and not destroy it so we can get as much data from it as possible.

Failure Modes

Before going ahead with the testing it may be useful to review exactly how our VIUD may fail at high temperatures:

• Plastic in USB connector melts
• USB flash drive fails
• O-rings Melt
• Internal epoxy melts/fails
• Body melts

The primary failure modes we're interested in would be the first two. The plastic melting in particular is the most likely failure as, depending on the exact type of plastic, it occurs at relatively low temperatures of 150-315 °C (300-600 °F)  although Wikipedia states a melting temperature for Polyethylene as low as 105 °C (220 °F).

It is difficult to determine at what temperature the flash memory will fail at although it appears to be a gradual process: the higher the temperature the more likely bits will flip by themselves. There is an interesting paper that shows results for accelerated temperature testing in the range of 170-250 °C (340-480 °F) and gives the data retention for their device at 105 °C (220 °F) as 10 years. We can assume from this that the failure temperature for the flash memory is also relatively high and not likely to occur before the connector plastic melts.

Similarly the last three failure mechanisms occur at temperatures above that of the plastic melting point. If Viton o-rings are used they are rated to 200 °C (390 °F) and probably won't completely fail somewhere above that. The epoxy used in this prototype is only rated to 125 °C (260 °F) but again won't completely fail somewhere beyond this temperature and the actual epoxy that is going to used is rated much higher (300 °C, 570 °F). The melting of Aluminum (660 °C, 1220 °F) and Titanium (1670 °C, 3030 °F)  is so high as to be mostly irrelevant.

Procedure

The procedure for temperature testing will be relatively simple:

1. Let test object return to room temperature.
2. Let test apparatus achieve desired temperature (if applicable).
3. Subject test object to the desired temperature for a set amount of time.
4. Cool object after test in water for at least 5 minutes.
5. Examine object for any obvious signs of damage.
6. Test USB for any new file blocks with errors.
7. Test USB contents for any changes in data.
8. Repeat test at slightly higher temperature and/or longer period as desired.

The test for bad blocks is done using HD Tune Pro which is a basic drive benchmark and tester. The test for changing bytes during a test is simply done by creating random files that fill the USB and using a MD5 sum to ensure their contents are identical before and after the test.

Test Results

The following table summarizes all the temperature test results so far:

Test Type	Temperature	Length of Time	Error Test	Bit Change Test	Notes
Oven	90 °C (200 °F)	5 min	Passed	Passed
Oven	120 °C (250 °F)	5 min	Passed	Passed
Oven	150 °C (300 °F)	5 min	Passed	Passed
Oven	180 °C (350 °F)	5 min	Passed	Passed
Oven	200 °C (400 °F)	5 min	Passed	Passed
Oven	230 °C (450 °F)	5 min	Passed	Passed
Oven	260 °C (500 °F)	5 min	Passed	Passed
Oven	290 °C (550 °F)	5 min	Passed	Passed	Case exterior exceeds 100 °C
Oven	290 °C (550 °F)	6 min	Passed	Passed
Oven	290 °C (550 °F)	7 min	Passed	Passed
Oven	290 °C (550 °F)	8 min	Passed	Passed
Propane Torch	1800 °C (3300 °F)	10 secs	Passed	Passed
Propane Torch	1800 °C (3300 °F)	20 secs	Passed	Passed
Propane Torch	1800 °C (3300 °F)	30 secs	Passed	Passed	Case exterior exceeds 100 °C
Propane Torch	1800 °C (3300 °F)	40 secs	Passed	Passed	Minor damage to external o-ring
Propane Torch	1800 °C (3300 °F)	2 min	Failed	Failed	Prototype #1, USB plastic melted
Oven	200 °C (400 °F)	15 min	Passed	Passed
Oven	290 °C (550 °F)	9 min	Passed	Passed
Oven	290 °C (550 °F)	10 min	Passed	Passed
Boiling Water	100 °C (212 °F)	60 min	Passed	Passed	Turned Aluminum black
Wood Fire	600 °C (1100 °F)	30 sec	Passed	Passed	Case exterior exceeds 100 °C
Wood Fire	600 °C (1100 °F)	45 sec	Passed	Passed	Damage to external o-ring
Wood Fire	600 °C (1100 °F)	60 secs	Passed	Passed	Damage to external o-ring

One interesting thing to note is that the boiling water test turned the drive a black color with tints of gold that actually looks rather nice (resembles a black anodized Aluminum). I'm assuming it is something in my water (a very hard water) that turned it this color.

Surprise...it's Black Now!

Comparing the Competition

Most USB drives don't have explicit temperature ratings but of those that do the LaCie Xtremkey has the highest:

• Operating temp.: 5 to 35°C (41 to 95°F)
• Non-operating temp.: -20 to 60°C (-4 to 140°F)
• Fire test: 30 sec. fire exposure
• Heat test: 200°C (392°F) / 3 min

Since we easily beat both of the listed tests by a considerably margin it is safe to say our VIUD would be the toughest USB drive available for temperature ratings.

Tentative Ratings

We still have to test our final design although I wouldn't expect too different results with the possible exception of the Titanium model performing a little better. We can still estimate our temperature ratings based on the tests so far:

• Operating Temperature: ? to 60 °C (? to 140 °F)
• Storage Temperature: ? to 90 °C (? to 200 °F)
• Air Storage: 290 °C (550 °F) for 5 minutes
• Boiling Water: 100 °C (212 °F) Indefinitely
• Wood Fire: 1 minute exposure (600 °C, 1100 °F)
• Propane Torch: 40 seconds exposure (1800 °C, 3300 °F)

The operating and storage temperatures may be changed by the specifications of the USB flash memory used. Next up will be testing the cold side of the temperature scale which should be interesting to see how low we can go.

Looking at the Competition

Looking at existing products in the rugged, waterproof or otherwise indestructible USB drive market is useful for a few reasons:

1. It may be that our "best" VIUD already exists.
2. Compare and possible change our design with what is available.
3. Get a better idea of prices if we wish to market our drive.

The following are a selection of better products found from searches of rugged, waterproof or indestructible USB drives.

Corsair Survivor

The Corsair Survivor looks like a relatively nice consumer level rugged and waterproof USB drive. It has a nice waterproof rating of 300 psi and its Aluminum case looks like it would take a pretty good beating. The design, in my opinion, is not ideal with a very large cap which may be easily lost. It has a relatively low price range of $30-85.

LaCie XtremKey  

The LaCie XtremKey looks like a decent candidate for a VIUD with a 300 psi waterproof and to a 10 ton pressure resistant rating. The "resistant" qualifier is suspect but with an all metal case it looks like it could handle being run over by a large car depending on the exact type of metal used (they mention a Zamac alloy but not which one). It has a large cap design like the Survivor which I dislike. Its price point is slightly higher at $85-140 but is not unreasonable for such a rugged device.

One notable specification for this drive is its large range of temperatures, particularly its high temperature limit of 200 °C. Although they again say "resistant" this is much higher than any other USB drive I've seen that actually has any temperature ratings (most don't).

Imation Ironkey Basic

The Ironkey Basic from Imation is a very nice looking drive with what looks like a basic metal case which would protect it from everyday bumps and drops but probably not larger accidents. It is rated waterproof under specification MIL-STD-810 which, as far as I can tell, is close to IP67/68 or essentially just waterproof from basic immersion and not pressure rated.

The drive's price is significantly higher than other rugged drives at $90-300 despite being less rugged. This is likely due to the Ironkey's main purpose of being an encrypted drive. Overall a great looking drive but not exactly what we're looking for our own VIUD. In theory if we wanted encryption it could be done at the software level.

Tyukalov USB Drive

The Tyukalov drive is a unique, one of a kind, custom USB drive which is interesting to compare to the consumer type drives previously found. It was made in a limited quantity of 100 at a relatively high price of $200-250 each but managed to sell out in a short period of 3 weeks. Its unique dual cavity design is not particularly convenient but it boosts the highest waterproof rating of 2000 psi of any USB drive I've seen and undoubtedly an equally high rugged rating.

Eternal Case

The Eternal Case is a product that wasn't out when I initially researched and came up with my VIUD design in the fall of 2012 but is remarkably similar. It just goes to show that if you think of a good idea there's a good chance someone else already has or soon will.

There are no explicit ratings for this custom product but from its design I would guess it should be waterproof to at least 300 psi and would easily withstand being run over by a car. Its price is amazingly low at only $40-75, even for a 32GB Titanium model. Based on what I've researched for prices I'm unsure how they can make a profit at this price. The only negative thing I can see is that the design/manufacture is relatively rough looking.

Wrapping Up...

There are other drives that are marketed as "rugged" but the majority don't actually have an explicit mechanical or waterproof specification. Most appear to be just cheap drives surrounded by a thin metal case with a "rugged" label which is not what I'm looking for my own VIUD. 

Even with this relatively small collection of existing true rugged drives it gives us a relatively good baseline on what is currently available and at what price. It also helps narrow down some of our design constraints, or at least what we would like them to be:

• >2000 psi waterproof rating
• >10 ton crush rating
• >200°C for 3 minutes temperature rating
• $40-300 (depends on capacity, quality, and ultimate rating)

Time will tell whether any of these are actually possible or not....