Posts Tagged ‘Retractable’

Assassins Creed Revisited

Wednesday, May 20th, 2009

So It’s been a long time coming, but I thought it might be a good idea to take another look at the retractable blade from Assassins creed, especially since there has been some new art released for the sequel, Assassins Creed 2. Now I stick by my original opinion with respect to the weaknesses of the original, as well as this new but equally complex design, and say that it would really be simpler to just use a single spring loaded blade, with both the blade and the housing structurally designed to eliminate any weaknesses the simpler design might have.

For those of you who may not have run across it yet, there are quite a few places selling replicas of Altairs infamous retractable blade from the first Assassins Creed. I will be posting a link to a place you can get one at the end of the post, for those who are interested. It’s a fiarly simple design, gravity or manual operated (not automatic), but it’s still a fun toy with some neat little tricks. Sinza posted a bunch of pics over at our forum Exotic Automatic. You can pay us a visit over there to see what the inside of one of these looks like.

Assassins Creed - Altairs Retractable Extension Knife

Assassins Creed - Altairs Retractable Extension Knife

But back to the topic at hand. The new design has some interesting new mechanical components not shown in the original, that I thought were good, possibly even  necessary design changes in order for it to work as shown in game, which was a problem that the original design art appeared severely confused about. Here’s what I’m talking about:

Assassins Creed 2 - Extension Blade Schematic 1

Assassins Creed 2 - Extension Blade Schematic 1

Assassins Creed 2 - Extension Blade Schematic 2

Assassins Creed 2 - Extension Blade Schematic 2

Above are a couple of screen caps from the trailer for the new Assassins Creed game, and as you can see, the blade design has undergone a few changes. In the first pic from the trailer, we can see an exploded view of the mechanical components from the original blade. However in the second pic we see a quite different schematic, of the blade, which has a large circular section at the top (or bottom, whichever you prefer) of the housing, next to an even smaller circular bit.

Now if you look closely you can see the large circle has three spokes, which would suggest that we are looking not at the housing, but at the mechanism itself. If this were the case, and that was a gear, then we would be able to see teeth, of which the wheel is distinctly lacking, This all suggests that this is a pulley, which I thought this was an interesting departure from the purported mechanical design of the first blade. Unless you were looking at the videos instead of the multitude of schematic, in which case it would actually make more sense. But I suppose that would all be confusing. 🙂

Anyway, pulleys are fairly easy to make, simple to use, and allow you to perform very large gear reductions in a very small space. This was one of the problems with the old design. It did not adequately describe how you would translate Altairs relatively small hand motion of less than an inch into the 6 or 7 inches of translational motion we see from the blade. Using a set of different sized pulleys however, it suddenly became very plausible. Not that the old design was impossible, it was just a really unlikely design.

Anyway, from the glazed looks many of your eyes have adopted, I suspect my endless ranting about the mechanics of a fictional automatic blade may be boring you to tears, so I I’m just throw the links at you and ponder the vagaries of automatic retractable blades all by myself. My conversations are much more interesting that way anyhow.

So there.

Altairs Sleeved Extension Knife from Assassins Creed – [Museum Replicas]

Altairs Sleeved Extension Knife from Assassins Creed – [StrongBlade]

Official Assassins Creed 2 Site – [Ubisoft]

The next best thing to Adamantium implants…

Saturday, May 9th, 2009

A couple of days ago I got a post from a reader (Thanks SniperFodder!) with a link to a page on Geekologie that showed videos of a very, very interesting set of home made wolverine claws. Here is the first of the two, very intriguing videos in question, mostly of the maker wreaking wanton destruction on some nefarious box of doom for some seriously heinous crimes we are clearly all blissfully unaware of:

Yes, all kinds of cool and everything, if you are into that kind of thing… Oh, who am I kidding, I love this stuff… I probably would try a more blade worthy opponent than an old box, but that’s just me… 🙂

What really caught my attention, however, was the construction vid that accompanied the shameless *cough* display of aggression above…:

Now as a person who has spent countless man-hours thinking about this kind of thing, let me just say that what this guy did was actually very impressive. Not that there haven’t been countless wolverine claw replicas and home made diy Wolverine claw jobs, but this particular construction dealt very directly and extremely competently with two aspects of arm mounted blade design that I have always found to be weak links in your traditional back yard / junk yard wolverine claw project.

The first and most common point of failure I see is in the blade attachment and rail mechanism. I see a lot of people use sliding drawer rails for the rails of their wolverine claws, and while it works, (works very well in fact), and is good for show, frankly, so far as strength is concerned, the vast majority of them wouldn’t hold up to the repeated stresses of cutting a slice of gouda cheese. Nope. Not even some “finely aged”, moldy gouda, half ready to decompose into a pile of technicolor goo.

Now this dude addressed this weakness by fabricating a simple sliding plate/tongue-in-groove rail. It is a design I’ve always thought would fit the ticket perfectly, but never had the time to try. And here, you can see it in action. Now I am, by no means, saying it’s a perfect solution. It has it’s weaknesses as well. In fact, you may or may not be able to tell from watching the vids, but that plate generates a lot of friction, so while it is really strong, it is also tougher to deploy smoothly. It also looked like he used a single rail tongue for all three blades. Not really how I would have done it, but it seems to work.

But the part that I found really impressive is his bracing. Yes, it is made of bent and brazed copper tubing, which I saw lots of commenters deriding him about, however what they fail to realize is that, assuming his brazings are strong,  his design eliminates one of the biggest weak points of any wolverine claw system. The arm attachment mechanism.

I see all kinds of wolverine claws or just home made arn claws/blades/ziphoids in general, with two little straps, maybe a soft leather arm band or something. The smarter ones go for a solid plate and attach that to their arms, though, again, with more little straps. The thing is, those little itty bitty strips of fancy arm floss just won’t hold up to strong impacts. They suffer from one simple flaw: They are too flexible.

No matter how strong the system itself is, straps and soft leather allow seem to allow the whole rig,to move backwards and forwards on your arm. I’ve seen this happen even with full forearm vambraces if the leather used to make them isn’t hard enough. In contrast, this guy used a solid framework of copper tubing that will not give, and is so closely fit to the dimensions of his forearm, that he should have enough stability and control with it that he could make bacon with those blades, should he deem it necessary.

What more can I say. The whole get up may look ugly, but mechanically, it’s really a thing of beauty. Incidentally, while the page I found these videos on say they are “fully functional” I think that depends on your point of view. Our friendly niegborhood Wolvie sports a set of double action, fully automatic blades. This guy, on the other hand (or, in this case, the other claw arm) made single action blades, (manual retract, automatic deploy) as far as I can tell. So it’s certainly close to the kinds of functionality Wolverine gets from his claws, but no cigar.

And just in case there is any question about what I mean by my earlier comment regarding the bacon, let me just be clear. Bacon is *always* necessary. But you don’t always have the opportunity to make bacon using a set of wolverine claws strapped to your forearms… That is just too cool for Ginsu school.. I’m just sayin. 😀

Guy Makes Fully Functional Wolverine ClawsGeekologie

A Predatorial Shuriken

Tuesday, April 1st, 2008

OK, So i’ll admit I’m not really the April Fools type. I sat thinking about all of the incredibly evil things I could have posted as an April Fools prank and realized… I just couldn’t do it. So instead, I’m gonna post about a fictional weapon that Ive always thought was very cool looking, but entirely impractical:

The Predator Shuriken

AvP Shuriken
[view full size]

This weapon was one of the cool weapons wielded by the race of Predators in the Predator series of movies. This particular shuriken was prominently featured on the AvP (Alien vs Predator) and AVP2 movies. Now the one featured here is a non-functioning reproduction shuriken, primarily because, well, this weapon would be near impossible to make work in real life, for reasons I’ll get into shortly.

I truly love many of the design details of this weapon. But what makes it such an intriguing weapon to me is primarily the subtle physical impossibility and impracticality of it. It is a weapon that appears, on the surface, to be physically plausible, but upon closer inspection, reveals aspects that are implausible, but so tempting close to real, that you cannot help but wonder if it would be possible to duplicate in real life.

AvP Shuriken – life size prop

AvP Shuriken
[view full size]

For example, looking at the pic above, you may notice that the overall design of this shuriken vaguely follows that of the Japanese Fuuma (or Windmill) shuriken, but departs from traditional shuriken design in it’s asymmetry. The blades are all biased towards one side of the weapon. Now besides the fact this this offends my sense of symmetry, this massive weight imbalance would also make it a very impractical throwing weapon. And yet, in the movie, it is thrown just as a Fuuma shuriken would be, without exhibiting any of the idiosyncratic flight characteristics that one might expect from such a poorly balanced weapon.

An even more implausible feature of the weapon is the great disparity between the retracted form factor and the fully deployed form of the shuriken. Below is a picture of the center section of the weapon with the blades extended:

AvP Shuriken – Center Section

AvP Shuriken - center Section
[view full size]

And here is a picture of the blades, again fully extended:

AvP Shuriken – Blades

AvP Shuriken -  Blades
[view full size]

In the movie, the blades are shown to extend out of the center section of the weapon. From the pics, it is apparent that a considerable level of nesting can and would need to occur in order for this to be physically feasible. By my count, there are six blades, each blade consisting of 4 sections, an extension/pivot lever, an outer extension sleeve, an inner extension sleeve and the blade proper. The weapons deployment sequence is shown in the clip below:

AvP Shuriken – Deployment

AvP Shuriken - Deployment

Sweeeet…! Incidentally, the little clip above may also explain the weapons asymmetrical design. If the blades were to extend in a symmetrical fashion around the circumference of the weapon, there would be no safe place to hold it during deployment without risking the loss of a few digits. If memory serves, I think these were used primarily as throwing weapons, so if I were designing it, it would be perfectly symmetrical, and would open in mid air when thrown, so as to avoid the awkward asymmetrical design. The asymmetry seems like a pointless trade-off if you ask me, but then again, I’m not an alien weapons designer…

Anyway, during retraction, the blade would have to retract into the inner sleeve, the inner sleeve into the outer sleeve, and the whole outer sleeve assembly pivot onto the extension arm, which would then all fold neatly into the center section, completely occupying that space. Sounds good in theory, except that, given the physical dimensions of blades, sleeves, etc, there should be hardly enough room for all six blades, let alone a deployment / retraction mechanism…

Of course, given the advanced nature of Predator technology, these technical details would almost certainly only be limitations of human technology, and would be little more than niggling little technicalities to a predator engineer.

In the end, however, it is the overall aesthetic of the blades, and the deployment mechanism that makes this weapon so captivating, and while the technical challenges would be great, the design is ultimately so close to something that could be made using current technologies, it would be very tempting to try…

I wonder if DARPA would be willing to give me a research grant for this kind of stuff… 🙂

AvP Predator Shuriken – [Black Aris]

An Automatic Knife on Steroids…

Tuesday, January 22nd, 2008

A couple of months back I encountered a very interesting automatic, spring loaded, blade design from the movie SAW. Now I have never seen SAW, or any of it’s sequels, so I hadn’t been privy to the various supposedly gruesome weapons that the movies featured, but I will say, I might go see all of them, just to see weapons like this in action:

Saw Blade Gauntlet
[view full size]

Now don’t get me wrong. I’m not a big fan of people being killed. Especially not in the purportedly gruesome ways that the movie depicts. Though from what I have read, the series illustrate a complex subtext about the raw, cold hearted drive of pain and vengeance, humanity, self sacrifice and survival. As a student of the human psyche, that might be one of the main reasons I might go and see this film. To be honest, that’s not entirely true. I really just want to see the weapons… 😛 But, as usual, I digress.

We are here today because I am a huge fan of blade aesthetics and mechanics. And this blade has a healthy portion of both. I was very impressed both by the aesthetics of the blade, as well as the with the amount of work that went into the mechanical aspects of it’s construction. It incorporates a lot of ideas I have kicked about in my head for many, many years, as well as a few I had not thought of.

Now the page I found this described it as a nonworking replica prop from the movie, but to anyone with a mechanical frame of mind can see how this blade was designed to operate, and boy is it a thing of beauty. Of course, given that this was from a hollywood movie, the fabricators who originally came up with the design had the funds to build whatever they wanted, and it shows in the way it is constructed.

There are a lot of parts and fabrication that went into this design that your average garage fabricator might find difficult to duplicate unless they are excellent welders and machinists. For instance look at the deployment mechanism. The little “spidey paddle” mechanism is affixed to the gauntlet via a custom fabricated pivot point welded to a flange on blade carrier bracket. a very nice job, with the paddle custom bent to fit the contours of the wearers wrist and hand.

Not that this mechanism is terribly complex or anything like that, but the rail delivery system is unique in the world of such weapons, and overall the fit, finish and attention to detail are superb. Much better than what most of us would be able to come up with in our garages. Not that we aren’t trying.

A good knife maker friend of mine, Sinza who is probably even more inspired by these kind of weapons than I am, has a site dedicated to his knives, and a forum dedicated to the construction of weapons like these. If you fancy a peek at what can be done with common household fixtures and parts from home depot, mosey on down to the forum for a gander. He’s got a pretty cool collection automatics to boot.

Sadly, the SAW blade gauntlet got pulled from the shelves almost as soon as it was made available. Still don’t know for sure why, but my guess would be reasons related to either copyright issues or irrational fears. But in any case, things like these, Wolverines claws, glaives, multi tools, combo weapons, all the unique and wonderful gadgets James Bond ever got from Q, etc., are things that have fueled my imagination for decades. So I’m always stoked to see something this cool, that isn’t just movie magic…

Phyreblade’s guide to Altairs retractable blade (From Assassins Creed)

Thursday, December 13th, 2007

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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