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Have you seen the Benchmade Infidel otf. It claims that by sliding the same "button" (a considerably shorter distance than the blade moves), the blade will shoot out and back in when the button is pressed again. Where does the energy come from? Doesn't that violate the laws physics?
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I am not previously familiar with the knife, but after looking at a google photo of the infidel, it is apparent that it is a standard DA OTF (Dual action out the front).
Assuming that the infidel is using the same basic principle of any DA OTF, such as the ones you can buy in Mexico for $5, this is how it works:
The blade is attached to a set of tension springs (the ones with a pulling force, not a pushing force). The springs are opposing eachother in terms of alignment. The "button" is also attached to the springs. In both the closed and the open position, the springs are pulling on the blade with equal force (i.e. they are stretched equally). When you slide the button, you pull one spring beyond the equilibrium point, and thus compress the opposite spring into a more relaxed state. At this point (when your thumb has caused the "button" to travel to it's maximum position), the net force on the blade is positive, and the spring under tension pulls the blade out of the handle (or in, depending).
To keep the blade from stopping in its travel due to the springs once again reaching the equalibrium poing, the blade is not directly attached to the spring assembly. It is on a "track," for lack of a better word... meaning that the blade is like an arrow shot from a bow: the blade moves with the spring while the spring is propelling it; but it keeps going (due to momentum/inertia) even when the spring stops.
At this point, the blade is extended to the "stop" on the "track," and your thumb is off the "button." The springs, since they are disengaged from the blade, return to their 50/50 equilibrium position. Now the process works in reverse: you push the button in the opposite direction, so the opposite spring is stretched, and therefore the opposite motion is acheived and the blade is pulled back into the handle.
The track assembly is really the trick to the whole thing. I don't remember exactly how is worked when I took apart one of those Mexican OTF's. Also, if you think about it, I'm pretty sure you could do this with standard springs (that push, not pull).
Again, I don't think Benchmade re-invented the OTF knife.
patriqq, close but how they work has been explained in detail a few times here ( once by me)....there are one or usally two springs with no tension on them when not in use. There is a transfer plate that the slide button is a part of. There are two tabs on the bottom of the transfer plate, and a tab on the bottom of the blade. Finally there are two sping controlled pin levers (one at the top and one at the bottom of the knife)..When you push the lever forward the tab on the bottom of the blade hooks the tab ( or opening at the bottom of the spring assembly) and as you push forward the spring expands at which point it catches a lever that relases the spring controlled pin holding the blade closed and the blade shots forward. When you push it to close the reverse occurs. This is a quick 6 am explaination.....lol...hope that hepls !!!
Thanks.... its been about 15 years (I was 13) since I took apart my OTF.
Mainly, I was trying to convey to Mobius that the mechanism wasn't black magic.
More like down with turkeys who would post what you did in a knife discussion forum.
Last edited by Bastid; 09-14-2007 at 06:50 AM.
I dropped my benchmade infidel from a coffee table, and the mechanism stopped working. Of course I took it apart thinking I could "fix it," but was sadly mistaken. Does anyone know of a reassembly video or instruction document I can use to put the infidel back together?
Thanks for the help, and I apologize if this is in the wrong section.
Had he not I might have never seen this
most excellent thread from the past!
Love post #2.
"Cataloguing my virtues won't work either... I hold them to a minimum so they're easy to keep track of." -Jim Rockford
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