Spring-loaded wrist blades

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New Member
When deciding on which direction I wanted to go with my costume, I decided early on to incorporate as much action as possible. This included, for me, functional wrist blades that could spring forward as desired to give a nice impression at a costume party or convention. I had an inkling of how to build this, but adapted my design from some videos I saw on YouTube...that were pretty much worthless...but I was able to glean enough from all of them to build this.

I am working with the following materials:

* 3-tiered ball bearing drawer slide
* plate aluminum (0.032" thick)
* 8-32 bolts, nuts
* 8-32 t-nuts
* 4-40 bolts
* scrap of wood
* springs (light pull, 2" length)
* #10 wood screws (1.5" length)
* #4, #8, #10 drill bits
* Dremel or other rotary tool
* sandpaper
* hand files

So, I grabbed the ball-bearing drawer slide I had in reserve for this particular project, got rid of the third tier section, and cut down the main section and the section that retains the ball bearings. For my gauntlet, this is 10" long.

Then, I decided I needed a material to hold the claws, keep them separated a decent distance, attach the claws to the sliding mechanism, be strong, and be light weight. Hmmm...wood works. Found a chunk of scrap in the garage, cut it to proper dimension and sanded it to a finished state.


Needed to attach the wood block to the slide in a reasonable way. Drilled through the block, drilled a hole in the sliding mechanism (which would be flipped over to give clearance for the fastener). Used a couple t-nuts and a long 8-32 machine screw to bind the works together.


These are my Predator claws that a friend cut for me. He is lucky enough to have a laser table to cut acrylic and plastics. He cut these for me, as well as a few extra sets. If you want a set of these, get hold of me. Anyways, these are nice, huh?

Needed to attach the claws to the wooden block. Marked out hole locations, drilled and then transferred marks to the block. I drilled for a #10 wood screw




With that out of the way, I turned my attention to the action part of this mechanism. The idea is to spring load the blades, and have them locked in the rear position. With a downward motion of my wrist, I will disengage the lock, and the blades will spring forward with much excitement. For that, I needed to modify the crap out of the drawer slide, the ball bearing slide and find fasteners that worked.


I'm using two of these springs. Not sure on their pull rating. It's not much, but enough that the blades will shoot forward with a nice speed. Will have to have some sort of rod or something I can grip to bring the blades back to a locked position.



Marking out, drilling and tapping the drawer slide. Using 8-32 fasteners.


Drilled and tapped holes in the ball bearing slide assembly. Using 8-32 here too.


Here's the assembly so far. I will play with height on the springs, and might use some washers to allow the springs to swivel a bit while still being held firm. Want the action to be smooth.


Mock-up of the assembly as of tonight. Lots left to do, but it's coming along. I won't attach the blades until last thing, and I have some work to do on them for aesthetics. I want to simulate a ground edge to the blades, while they stay blunt and safe.


This is a simple steel rod that I bent to shape, then epoxied (JB-Weld) into a drilled hole in the wood block. This will be the catch for the latching mechanism.





This some simple plate aluminum. I am using this to make a custom latching mechanism, and a part I hadn't intended. I discovered early on that the action of this mechanism was strong enough that when it sprang forward, the ball-bearing slid portion would kick up and allow the ball bearings to go flying. Funny the first time it happened, but annoying after that. I decided to make a retainer plate that would wrap around the drawer slide and keep everything in place.


It ain't fancy, but I used my little machinist's vice and some scrap wood to make a sheet metal brake. I bent the plate a little bit at a time until it started to wrap around the slide as I wanted, then continued to shape it with a small hammer around the drawer slide. Took a lot of adjusting to make sure it was fitting tight, but not binding the mechanism. Eventually got it just right.



This is the latch cut from the plate aluminum. I have it mounted on a 8-32 screw, sitting up high enough it engages the bent rod in the wood block nicely. This also is a piece that takes a lot of finessing to get just right. It has to be shaped somewhat like this so the piece sticking out perpendicular to the drawer slide can have a cable attached to it to go to my wrist or finger to be pulled and activate the mechanism.


So far, this is what we have. It is functional at this point, even though it is not complete.


These are 4-40 socket-head cap screws that act as stops for the slide. If these are not present, when the action springs forward, there is a good chance to flip the springs and bind the whole works up. I placed these just slightly behind the forward-most position of the action.




I am using a very thick ABS plastic as the top plate for my gauntlet. This is what the spring-loaded mechanism is bolted to by way of the two fasteners in the front that hold the springs, and the rear fastener that holds the latch mechanism. The whole assembly sits slightly off the surface of the plate by way of some stacked washers...because clearance is needed for the bearing retainer plate I had to fashion. After reaching this point and playing with the action, I discovered I will want to reinforce the plate with some cross-braces and probably another layer of the plastic. That's for another update.


With the claws mounted, the assembly looks like this.

For additional fun, I shot a short video to showcase the action of the system. I will continue work on this mechanism and get it reinforced. Additionally, I still need to construct the mechanism to activate the latch by way of a cable or cord attached to my wrist or hand. That will be covered in my next update.

Link to video:

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New Member
hi jon great work there mate,that is a sysyem very much like mine ,the only difference is i used high tension elastic band,the sysyem is only the 1st prototype and currently working on a better one,i myself was not happy with the slide part and latch system, your work has inspired me well doneto your work. just out of curiosity you mentioned you had spare blades,are you selling thes or what? can you pm me the cost they look cool.thanks tony.

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New Member
wow when I was watching your video and you said you went to heavy on the two springs instead of one. I thinks its even better with 2 springs because of that abrupt stop just like the celtic pred in AVP had his blades when they came out they kinda slammed and made that same noise I think the ones you made were awesome and better looking like the real gaunts.
Looks Great good Luck.
And if you ever thought about selling that would be awesome!


Well-Known Member
Excellent tut Jon, personaly love the speed the blades move, very quick

i will be watching for any further updates

WTF are you

New Member
AMAZING!!! Just seen the vid you put up and the movement seems quite like the real thing. Great huntorial. just the release mechanism to work on now and the reset. good luck


New Member
I have the thing done. Too tired tonight to mes with the photos and video, so I'll update this thread tomorrow once I finally crawl out of bed and get some coffee.

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New Member
Good looking mechanism there. I like the way they shoot out quickly -- they go more quickly than a motor will move them.

I'd like to see how you retract the blades and arm them again. Have you worked out a system for that yet?


New Member
Update time. I had actually finished last night, but was a little too tired to mess with the photos and video. Now that I have a piping hot cup of coffee next to me, I have no excuse not to update this thread.



I needed some sort of track or guide for the cable or cord to travel in that I would activate the firing mechanism with. I used a section of small diameter brass tubing for this. Ultimately, I had to bend it to a proper shape, but we'll get to that.


Nothing fancy here. Just some strips of the same thick ABS plastic I am using for the top plate to serve as guides for the brass tubing. Fitting against the tube tight, the whole assembly will be slathered in epoxy to keep things stationary.


This tightly coiled spring is actually a tubing bender. What a pain in the ass to use. Unhandy, unwieldy, and uncomfortable to use. Still, I was able to eventually bend the tubing as I needed to get this rig to work.







I needed to fashion some sort of retainers to hold the small spring in place on the rod that houses the activation cable, as well as on the firing mechanism itself. Again, ingenuity over fanciness. I threaded sections of the brass tubing, then screwed on 8-32 nuts far enough to give me a stub that I could place inside the spring. Once the tube and the firing mechanism were linked together, I also encased the spring in a small section of tubing that will keep the spring tracking in a straight line, instead of bending in half, which is it's natural tendency in this situation.

Note that the firing mechanism is bent to a different angle, and the tube for the cable is different than in previous photos. Trial and error. I had to bend a new tube with a section horizontal to the firing mechanism. In short, I had to play with this a lot to tune it so it worked the way I wanted it to. Burned a few hours doing this type of stuff.







Next, it was time to reinforce the baseplate. I used scraps of the same thick ABS. Placed in different directions, I ensure that any loads placed on the top plate will distribute evenly, and won't cause a "buckle" in the plate. I topped the reinforcement with another layer of the ABS, then marked and drilled for the location of the hole that my cable would go through to my hand or finger. I used a section of plastic tubing to serve as a guide for this, then trimmed it flush with the surface of the plate. Now it was time to make the body of the gauntlet.


I glued some angled pieces of plastic to the bottom of the top-plate assembly. This will give me a wide surface to glue the gauntlet body to.


Furthermore, I glued strips of the same angled plastic on the plastic that would be bent around to the shape of the gauntlet. This is just a plastic sign, but it works great.


Glued on one side, bent around and glued on the other. We now have a basic gauntlet. Woohoo!


This is just a split ring that I fastened the cable to to activate the gauntlet. It slips over my finger, and I need only flex my wrist downward to fire the blades.


Video link:


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