I had been considering doing a piece on retractable blades for a while, and was finally motivated to do so by a post I recently got in my suggestion box. A reader, Zach B. commented about his build of an under-hand retractable blade, similar to what the assassin Altair uses in the game Assassins Creed:

Assassins Creed Poster
[view full size]

In general, I love blogging about game weapons with real-life counterparts, but obviously, this game is pretty new out, so there are no official (or unofficially) produced rip offs… err production “replicas” of the Altairs retractable blade to be had for review.

However, since the games release, there have been numerous attempts to duplicate this weapon, and while YouTube is replete with videos of home made “Assassins Creed” blade contraptions, I noticed that, due to a lot of conflicting concept art from the developers, there is actually a lot of confusion about this blades design.

So, in typical blade nerd fashion, I thought I’d try to sort things out. Not necessarily to replicate the game blade, but rather to come up with a practical, real life design for such a weapon. Now let me preface the following by saying that, for your average dweeb, walking around with a spring loaded blade up your sleeve is an incredibly bad idea. There is a reason why these kinds of weapons were not common, even when they were legal. They are highly impractical, not to mention that they are an accident literally waiting to happen.

But, for those of us who like to live on the edge, love the aesthetics and the mechanical challenge of designing wacky weapons, and are insane enough to try, (notwithstanding the very real possibility of self impalement), I’ll go on. Proceed at your own risk. But remember, Altair has no ring finger. Think about it… People, please, do NOT try this at home…

Mounting and Placement.
For any wrist mounted blade to have the stability and strength to be used effectively, it must be properly mounted. This means a solid (inflexible, like steel, very thick/stiff leather or wood) mounting platform, preferably formed to the shape of your forearm, and a minimum of two straps to keep it in place, one at either end of this base. Your best bet would be to use the entire length of your forearm, with a minimum of two straps, one placed at the wrist and the other just before the elbow, to maximize the weapons stability. Altair has this covered quite nicely, as he used full length bracers with three straps:

Altairs Bracer
[view full size]

Now looking at this concept art for the game you’ll notice that the blade seems to come out from the spot where Altairs ring finger ought to be. In the game, this is not the case, and is entirely impractical for any real life assassin, (unless they are a mutant, like Wolverine) so we will disregard this little snafu, and assume the blade is mounted under the forearm, and not actually in his hand. Next stop, blade design.

Blade Support and Design
Now here is another area that has been thoroughly bolloxed on account of multiple conflicting concept art. In the game, Altairs blade uses a nested rail delivery system, where the blade is housed inside of a set of nested sleeves, which run on an internal guide rail. The sleeves extend sequentially, outermost rail first, then inner rail, and finally the actual blade, once both sleeves are fully extended and locked:

Assassins Creed Blade with double nested sleeves

Altairs Nested Sleeve Blade system
[view full size]

Now here is where the confusion begins. Depending on which art you are looking at, Altairs retractable blade either has two sleeves, or one sleeve:

Assassins Creed Blade with single sleeve

Altairs Single Sleeve blade system
[view full size]

Now nested sleeve systems have the advantage of being able to fit in a retracted form factor that is only a fraction as long as the weapon is when fully extended. This means a much more compact housing. However this comes at a cost. The added complexity of automating the extension and retraction of multiple nested sleeves require smaller, more delicate parts, necessarily manufactured to very close tolerances, that would make the whole mechanism more prone to failure.

In fact, in my opinion, the ideal system would actually use no sleeves whatsoever. And given that you have (and should really use) the entire length of your forearm with which to conceal both the blade and the deployment mechanism, I don’t really see the point of implementing such an elaborate system. Not to mention that a single, fixed-length blade would be stronger, faster, more reliable, and infinitely easier to automate than a shorter blade mounted in multiple sleeves. Which brings us to the our deployment system.

Automation
A very important aspect in the operation of any stealth weapon is an equally stealthy activation mechanism. Preferably one that can be activated ‘hands free”, in a manner of speaking. And Altairs got one. In the first concept picture above, we can see that there is a little harness attached to Altairs pinky from the blade housing. This is intended to be his blades activation switch:

Assassins Creed Blade – Ring/Cable Activated

Assassins Creed Blade Mechanism
[view full size]
[video here]

However, in one of the promotional vids for the game we see Altair having to press a button to release a switch that activated his blade:

Assassins Creed Blade – Button Activated

Assassins Creed Blade Switch
[view full size]
[video here]

Now truth be told, this button is probably one of the more complicated ways of doing this. Indeed, you can see that it’s actuation would be counterintuitive, as it would require you to place your fingers in the path of the out going blade in order to activate it. In any case, from the numerous videos of him in action, we can see that Altair simply flexes his hand away from the blade to activate it, so we can assume that a button based activation system is not used. A finger ring cable is a much more flexible way of doing this, and the one I’d go with.

So far as the actual deployment mechanism is concerned, if we stick with the simple, single blade (no sleeve) approach, we can actually use a very compact dual spring double action out-the-front switch blade mechanism. They are simple, reliable and fairly easy to implement. I won’t go into schematic detail here, as it would extend an already excessively long post, however, I can point you in the direction of a buddy, and fellow knife fanatic Sinza, with whom I run a forum (Exotic Automatic) with a lot of helpful diagrams, as well as a break down of some common double action OTF mechanisms. Go on over and check his site out if you have the hankering for a more technical look into the topic…

The Blade.
Finally, we come to the point (pun intended) of all this, which is the design of the actual blade itself. As I mentioned earlier, I favor a single blade approach, with no sleeves, housed in a simple, dual spring loaded guide rail, in the style of your regular OTF switchblade. So far as the blade itself is concerned, we would need to meet a few specific criteria. The blade would need to be long enough to penetrate thick clothing and still puncture vital organs, thin enough to be able to slide between a persons ribs, yet thick enough to resist bending. Throw in double edges, and a sharp point, and we have a winner.

Interestingly, these are the same basic design specifications of the contemporary Fairbairn-Sykes fighting knife design, which I will talk about in a future post. Nonetheless, this should give our assassins blade all of the required features to be a terminally effective assassination tool… And that’s all I’ve got to say about that…

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