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
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 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.
Altairs Sleeved Extension Knife from Assassins Creed – [Museum Replicas]
Altairs Sleeved Extension Knife from Assassins Creed – [StrongBlade]
Official Assassins Creed 2 Site – [Ubisoft]