Intro: Better Computing Through Velcro: Make Your Laptop a Dock for External HDD's
There's rarely a safe and convenient place to put a portable external hard drive when using a laptop in a mobile, non-desk situation.
Example: You're working on your laptop and want to back up some files or work on some media that you have stored on an external drive. You pull it out of your bag and look around. If you're on a plane or train, at a coffee shop with a teensy-tiny bistro table, or lounging outside on a patio, you'll quickly realize there's no convenient place to put the external drive and be assured that while in operation it will be safe from liquid spills, getting whacked, or falling off of your lap or miniature workspace.
Adhesive-backed velcro strips.
A Geek Factor of 6/10 - This isn't for the fashion-conscious or those wishing to keep their laptop un-customized.
WHAT YOU NEED TO DO THIS:
# 15 minutes
# Velco or other brand hook-and-loop adhesive-backed fastener strips. (comes in rolls or pre-cut lengths)
# Paper towel or clean cloth.
# Scissors (with which to cut the velcro to size)
# Pencil (to mark and measure the velcro)
# Isopropyl Rubbing Alcohol or other grease-removing, residue-free cleaning agent.
# Portable External Hard Drive (or WiFi / wireless dongle, CD-Rom, tethered smartphone, etc)
New Material Cost: Under $10
Step 1: Velcro Engineering (Or, Is My Hard Drive Safe?)
The first and most immediate concern: is velcro strong and reliable enough to hold an external drive and weather normal movement from the laptop without the risk of it falling off?
Short Answer: Yes.
The Long Answer: Hook-and-loop products are rated by 3 important characteristics: Pull-apart strength, shear strength, and cycle-life. The products also come in two main grades: consumer-grade and "industrial strength" or "mil-spec" (i.e. military spec, or other governing-body specified and regulated).
Pull-apart strength measures how much force per unit area of velcro it takes to separate two pieces straight apart from each other. This is usually anywhere from 0.8 - 2 psi for both versions.
Shear strength relates to how much it takes to "slide" the opposing velcro pieces apart. It typically varies from 6 - 10 psi for most.
Cycle-life determines how many times the pull-apart / stick-back-together operation can be performed before the holding strength of the velcro degrades to 50% of its initial value.
This is where there is the biggest distinction between the two types. Consumer-grade velcro that can be purchased from any number of general hardware and goods retailers usually has a cycle-life of a few hundred. Mil-spec has a cycle-life ranging into the several thousands.
Some quick numbers:
Discussed further in Steps 3 and 6, I chose to have two strips of velco on the hard-drive intersect perpendicularly with two strips on the laptop.
Thus, there are 4 points of contact between the hard-drive body and laptop, and given 5/8" wide velcro strips, the total area of velcro contact is 1.56 in^2. Taking the lowest strength values (0.8 psi pull-apart, and 6 psi shear), this amount of velcro is therefore capable of withstanding 1.25 lbs of pull-apart force, and 9.3 lbs in the vertical, shear direction.
Most 2.5" portable external hard drives weight about 0.25 lb. This means that in the pull-apart direction, the HDD could withstand 5 G's of acceleration before pulling off, and up to 37 G's before shearing off in the vertical direction.
Likely, for your HDD and laptop to experience those accelerations, it would only occur when they slammed on the floor after having been dropped from a height of several feet. Normal use and fidgeting shouldn't be nearly enough to separate them.
The Usual Disclaimer:
Use your common sense when approaching this project. I've calculated and real-world tested using the above specs; they're solid. If in your own application of this 'ible you deviate significantly from the given advice by using too little velcro or attempt to attach an abnormally heavy hard-drive or peripheral, you are responsible for what may come of it.
Step 2: Is Your Laptop Screen Up to the Task?
HINGE STIFFNESS: Laptops come in all range of sizes and designs. One thing that tends to differ between them all is how stiff the screen is to rotate open, closed, and adjust between positions
Testing is the easiest way to determine if your particular laptop screen will support the weight of the HDD without any possibility of it wanting to rotate open or close by itself.
If as is, your monitor takes a somewhat fair amount of pressure to swivel about its hinges, you should be fine, particularly if it has no problems with staying open at a 45-degree angle. If there are any doubts, get out some duct-tape or packing tape and firmly attach the drive to the back of your monitor and see if the monitor stays in position. If the monitor still requires a bit of push or pull in order to swivel it about its hinges, you should be OK.
TEMPERATURE: Feel the back of your monitor after it's been in normal use to see how warm it gets in general. If there are any particular hot spots, make note of them and do your best to avoid placing the velcro such that the HDD attaches directly over the area. The reason being twofold: 1) to prevent over-warming of either the HDD or the monitor 2) to prevent any potential heat-softening of the adhesive-backing of the velcro.
Step 3: Buying Velcro (TM) and Other Hook and Loop Fasteners
In the US, the easiest place to find consumer-grade, "sticky-back" velcro is at hardware stores such as Home Depot, Lowe's, Ace Hardware, etc. Office stores like Staples, Office Depot and Office Max will carry it too, as will general goods stores that also service towards crafts and hardware, such as Walmart, Target, etc. Craft-specific stores such as Michael's and Jo-Ann's should also sell it as well.
Internationally....I have no idea, though similar types of stores to those described above should be in most places. At the very worst, there are numerous online stores that sell velcro.
EDIT: @doctoral pointed out that velcro straps and squares can also be found at discount / dollar stores as well.
What grade to get?
If you don't plan on attaching/removing a hard-drive too often, the regular consumer grade you can find in the above retail stores should last for a while. However, if you anticipate making use of it at least once every day or two, you'll easily exceed the typical 200 cycle lifetime of consumer grade velcro within a year. In this case, you could either remove and reapply fresh regular velcro once the first application gets worn, or at the start you can get high cycle-life velcro. The latter is sometimes sold in brick-and-mortar stores as "industrial-strength" velcro, while there are also a number of online retailers who sell it and can be found via a quick Google search. For my own use I bought a 5' roll of 5/8" velcro (with a cycle life of 5,000) for about $6 at mcmaster.com
5/8" wide strips are a safe bet, and the size that I calculated for and am currently using. With this size, two strips are used on the drive itself and are placed to attach perpendicularly (rather than in parallel) with two strips on the monitor when attaching (see illustration in Step 6). You could certainly go with larger strips, and even use just one large 2" strip instead of the two smaller ones, though this may depend on whether or not you have concerns of the hard-drive getting too warm from lack of air circulation.
1/2" wide strips are about the smallest I'd recommend, and in that case would be safest in placing the velcro strips such that they face in parallel with each other so as to gain more surface contact area.
Step 4: Prepping the Surfaces
The biggest enemies of adhesives are dust, dirt. and oil/grease.
To make sure that the adhesive back of the velcro strips adhere properly, use rubbing alcohol or any other grease-removing residue-free cleaning agent to wipe off both the back of the laptop screen and the bottom of the HDD where you'll be placing the velcro strips.
Step 5: Cutting and Attaching Velcro to the Hard Drive
First things first: Does it matter which surface you use the hook or loop side of the velcro on?
Yes, I think so, reason being: the hook side of velcro loves to grab at stuff (as it should). If you're likely going to be pulling your laptop in and out of a bag frequently in day-to-day use, it will be better off if it doesn't have a few strips of grabby hooks attempting to snag the interior of the bag. Plus, the hooks aren't comfortable against skin, so if you ever carry your laptop like a book this will be annoying.
Therefore, use the hook side of the velcro on the hard drive, and the soft hoop side on the laptop itself.
* Measure out and cut an appropriate length of hook-sided velcro.
* Peel off the very end, and attach to the start point on the HDD
* Press down with your finger and continue to work down, while peeling the rest of the velcro backing
* Once all peeled and pressed, use a hard-pointed object such as a pen top to rub/roll back and forth and make sure the adhesive is firmly pressed without any air bubbles.
* Repeat for second strip.
Step 6: Attaching Velcro to the Back of the Laptop Screen
Velcro Patterning: I chose to go with two perpendicular strips for ease of use and flexibility, though a parallel pattern could be used for extra strength if desired. As it is, the perpendicular pattern is ample for keeping the drive attached.
Drive Placement: Ideally, you'll want to orient the drive so it is as low as possible down the back of the monitor, centered over the hinge. This limits the relative movement of the drive itself when adjusting screen angle or shifting the laptop. Also, placing the drive so that it is too high or far from the hinge may lead to unnecessary stress upon the plastic casing of the monitor and the hinge over the long term due to the action required to detach the velcro.
Don't forget to check where it will be in relation to your nearest USB ports and make sure your cable will reach.
* Check with the drive where you'll want it to be located on the screen back
* Mark with a pencil the end points of where the velcro strips will go
* Be sure to use the loop side of the velcro.
* As in step 5: Cutting And Attaching velcro to the HDD - peel off a bit of backing, press, unroll, and continue till done. This time, you'll probably not need to go over with a hard object, the hoop side velcro will press down pretty firmly with just your fingers.
Step 7: Done! Some Final Notes
Attach your HDD and plug it in!
Some notes about using:
Don't adjust the viewing angle of your laptop screen quickly or abruptly when the HDD is reading or writing from the drive. The velcro will act as a shock absorber to help dampen transmission of high frequency vibrations, but it has limits and extremely sharp movements could otherwise possibly lead to drive malfunction.
It *is* OK to reposition the screen in a normal, smooth manner when the HDD is not actively processing data. No additional caution is needed above and beyond that of usual when moving and positioning the laptop itself due to it's inbuilt HDD.
If you ever want to remove the velcro:
I've not done it myself personally, in theory you should only need to dowse the strips with a solvent of some sort like rubbing alcohol, nail polish remover, acetone, paint thinner, etc. It should work to loosen the adhesive enough to remove the strips, and then the remaining residue.