Except theres a big difference between a key opener and a automatic out-the-front spike.
Perfect X-Files Stiletto Replica (need your help, please!)
- Thread starter Jacobson
- Start date
Jon Kelley
Active Member
Yeah. By the time I'm in a position to damage you with a can opener, I've probably already broken significant portions of your anatomy. Which is why the rule doesn't make any bloody sense.
U dont seem to read private messages, do u? :lol
EDChainsaws
New Member
I've been giving some thought to this over the weekend, had a look at how an OTF switchblade works and I think I've come up with a workable mechanism based on a forward/backward button. I might have a go at prototyping it, I've no interest in selling them, but it's just a little interesting puzzle, and I'm happy to assist anyone else in making them. I agree with an earlier poster, that having a button which is pushed in rather than moved forward/backward like an OTF is so much more complicated.
Firstly if you take a look at this youtube video to see how an OTF actually works; How Does a Double Action OTF Work? - YouTube I'm taking that design and converting it from something flat to something tubular. It's built with K&S Brass tubing in mind. At the centre you have a stainless steel/plastic/aluminium/brass (it's most important that it's non-magnetic) ice pick shaft/point fixed into a solid steel cylinder say 1" long and 1/2" wide. That slots inside a slightly larger tube and can slide up and down like a piston. Then you have loose end caps on each end maybe 1" long which slide over either end of the inner tube (one with a hole in for the ice-pick shaft). Connecting the two end caps to each other you have two tension springs, one running down each side (you night need to cut slots down the length of the central tube to allow for spring space). Finally you put this whole assembly in another outer tube and have strong shallow pot magnets at either end which will attract the central ice-pick solid steel cylinder (again one with a hole in for the ice-pick shaft). The rest works like an OTF knife, the sliding button moves the central tube up/down but the ice-pick cylinder stays stuck to the magnet at one end till the spring tension is enough to break the attraction firing the ice-pick cylinder towards the other magnet. Going for a magnet rather than a catch to hold the ice-pick cylinder in place at each end means the pick is not held as firmly in place as it would be with a catch, but it can't really break (the worst that will happen is the magnet disengages and the ice pick retracts slightly), and it's so much easier to make. I've had a quick look at shallow pot magnets around 15mm diameter and 5-8mm in height and you can get them up to around 3-4kg pull which is a fair bit.
Getting the mechanism to work right is just a matter of matching the springs to the magnet strength. If they are mismatched either moving the button all the way down will not be enough force to disengage the ice-pick cylinder from the magnet, or on the other side, the force will be too much disengaging the ice-pick cylinder from the magnet before there is enough spring force to propel it to the other end stopping the retraction mid-way. If need be, a third or fourth spring could be added to increase the spring pull, or if stronger magnetism was needed, the solid steel ice-pick cylinder could be substituted for a tube with a strong shallow pot magnet at either end, so you have a magnet on both the ice-pick cylinder and at both ends of the tube, greatly increasing the magnetic attraction. Anyway, once that's worked out, the rest is just getting the outside to look the part which is simple enough.
Anyone any thoughts on this?
Firstly if you take a look at this youtube video to see how an OTF actually works; How Does a Double Action OTF Work? - YouTube I'm taking that design and converting it from something flat to something tubular. It's built with K&S Brass tubing in mind. At the centre you have a stainless steel/plastic/aluminium/brass (it's most important that it's non-magnetic) ice pick shaft/point fixed into a solid steel cylinder say 1" long and 1/2" wide. That slots inside a slightly larger tube and can slide up and down like a piston. Then you have loose end caps on each end maybe 1" long which slide over either end of the inner tube (one with a hole in for the ice-pick shaft). Connecting the two end caps to each other you have two tension springs, one running down each side (you night need to cut slots down the length of the central tube to allow for spring space). Finally you put this whole assembly in another outer tube and have strong shallow pot magnets at either end which will attract the central ice-pick solid steel cylinder (again one with a hole in for the ice-pick shaft). The rest works like an OTF knife, the sliding button moves the central tube up/down but the ice-pick cylinder stays stuck to the magnet at one end till the spring tension is enough to break the attraction firing the ice-pick cylinder towards the other magnet. Going for a magnet rather than a catch to hold the ice-pick cylinder in place at each end means the pick is not held as firmly in place as it would be with a catch, but it can't really break (the worst that will happen is the magnet disengages and the ice pick retracts slightly), and it's so much easier to make. I've had a quick look at shallow pot magnets around 15mm diameter and 5-8mm in height and you can get them up to around 3-4kg pull which is a fair bit.
Getting the mechanism to work right is just a matter of matching the springs to the magnet strength. If they are mismatched either moving the button all the way down will not be enough force to disengage the ice-pick cylinder from the magnet, or on the other side, the force will be too much disengaging the ice-pick cylinder from the magnet before there is enough spring force to propel it to the other end stopping the retraction mid-way. If need be, a third or fourth spring could be added to increase the spring pull, or if stronger magnetism was needed, the solid steel ice-pick cylinder could be substituted for a tube with a strong shallow pot magnet at either end, so you have a magnet on both the ice-pick cylinder and at both ends of the tube, greatly increasing the magnetic attraction. Anyway, once that's worked out, the rest is just getting the outside to look the part which is simple enough.
Anyone any thoughts on this?
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Wreckhur
Jr Member
EDChainsaws, there is no need for magnets. I am using a single expansion spring of .175 O.D. X 2" and it will drive the blade both ways the full 5 inches, internal. Other than that, it is similar to how I am building my action. Also, something that required a lot of work, was the actual locking mechanism on the blade/blade holder, to momentarily pause forward and backwards motion. Fortunately though, using aluminum and brass cuts down on the weight of the moving parts, specifically the "carriage" (the part connected to the switch) and the blade holder. This is why I can use a single spring. Though, the blade holder must be very small to move between the carriage and the base tube inside. I have also used numerous springs elsewhere, for locking plates, with tension screws set inside of the internal frame. Therein has been my single greatest struggle.
Even with a .500 I.D. that still leaves very little room for parts. I am making parts down to .050 of an inch! Sadly tools that small are very expensive and break really quick. The good news: I have a CNC mill. The bad news: I have a manual lathe. But really, using the compound to make the taper on the O.D. of this is pretty simple, just a little trig!
I am currently in production on my dual action blade and will be making static, and gravity action models. Once I have met the requirements for selling here...
I Have greatly enjoyed the mental workout this prop has given me, due to the mechanics being forced inside such a small object.
Even with a .500 I.D. that still leaves very little room for parts. I am making parts down to .050 of an inch! Sadly tools that small are very expensive and break really quick. The good news: I have a CNC mill. The bad news: I have a manual lathe. But really, using the compound to make the taper on the O.D. of this is pretty simple, just a little trig!
I am currently in production on my dual action blade and will be making static, and gravity action models. Once I have met the requirements for selling here...
I Have greatly enjoyed the mental workout this prop has given me, due to the mechanics being forced inside such a small object.
EDChainsaws
New Member
The magnets I've suggested are not to help the travel of the spike, they are to lock in in place at either end (ie fully out or in), instead of any locking catch mechanism. They will help the travel to an extent though. As you say the locking mechanism is very fiddly, getting something that small which will fit in place around the spike it not an easy job, which is why I came up with using magnets, then the locking mechanism and the spring travel mechanism are kept separate and aren't in eachother's way, keeping it simple.
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Wreckhur
Jr Member
Sorry I misunderstood. Still, I'm not sure if you can find the room inside of the tube. Though I have gone a different route, if you need help, or want to bounce ideas around, I would be more than willing to share what I have come up with and/or help. Not implying that you need help, but I know it helps to bounce ideas around. I also have made a detailed blueprint and have done all of the math, so if you are looking for numbers, I can help there too. This offer is open to anyone.
Wreckhur
Jr Member
My blueprints represent a lot of time and effort, much more than I had anticipated (140 hours so far) along with a mockup and two prototypes. I don't mind helping, but I can't let go of the whole blueprint. Especially since I am planning on selling a few of these once complete... Though I should have a video up within the next week of the finished alien shank.
Bump,
was this ever made?
was this ever made?
