Last year for Christmas a friend gave me an unloaded grenade as a gift. Since getting a chance to play with it, the triggering system has fascinated me. The system is very simple. The pin holds the lever (or spoon) which holds back a spring loaded striker. When the pin is pulled and the spoon released the striker swings around to the priming charge which activates the grenade’s fuse. I have been very impressed with the amount of force supplied by the small torsional spring to the priming charge and have wondered how else this force might be applied. I decided to take on this challenge for my upcycling project. I felt it would be appropriate to turn this Christmas gift into a common Christmas decoration, a nutcracker.
Traditional nut crackers, although often beautifully crafted decorative pieces, are seldom used for or even capable of cracking nuts. Once I had decided to use my similarly decorative (non-explosive) grenade to create a nutcracker I quickly began investigating whether this could even be done effectively. This involved buying some common nuts which require a cracker and putting the unmodified grenade to the test.Before I get into that I’d like to take a moment to talk about the “design cycle.” When my team drew up what we thought the design cycle is it looked a bit like a circle with a star in the middle. If you follow the edges you can see that; although, there is an idealized cycle in the clockwise direction, in actuality you can jump from any step to any other step as necessary. This is intended to illustrate that in the iterative process of design a full iteration is not always necessary.
My design process followed the cycle drawn by my group fairly closely; although, it would be hard to deviate as all possible paths are covered. What struck me as interesting about how I designed this widget was that I essentially went once around the loop for each aspect of the design. I started with the problem of using a grenade trigger mechanism to crack a nut. I brainstormed some ideas involving modifying the striking lever to improve impact effectiveness or position. My first prototype was to simply hold a nut in the way of the lever. I tested this on pecans, peanuts, and pistachios. This was undoubtedly a sample of convenience as it is what I found at my usual grocery store. The cracker was very effective against well lined up peanuts and pistachios. Upon considering the fact that both of these nuts are easily opened by hand I decided to focus further testing on the pecan which is usually not easily opened. This resulted in simply punching holes in the shell but, with two strikes the nuts could usually be opened easily by hand. Satisfied with this result (considering the ridiculousness of my endeavor) I began to loop around a new problem.
The next issue was how to hold the nut in place without awkwardly contorting my hand as I had in the initial testing. At this point I had removed the spoon from the design entirely. After a handful of failed ideas including not holding the nut (which basically created a pecan firing device) and using rubber bands, I remembered the spoon. Holding it on the opposite side of the grenade head from its usual position allows it to create downward force on the nut while not interfering with the striking lever. I attached a small hinge to both the body of the grenade and the spoon using JB Weld. Adding the hinge allowed for the spoon to swing and made it easy to both use and understand how to use.
At this point I tested the mechanism once again and the performance actually improved. Rather than punching a small hole as it had done initially the impact was causing cracks in several directions very consistently. This weakened the shell enough to be broken by simply squeezing between a finger and thumb. This resulted in very easy to open pecans without crushing the meat inside.
Happy with the mechanism I turned to the aesthetics of the device. Initially I had planned to keep the natural grenade look to appeal to the aesthetic of repurposed military hardware. This can be seen in bottle openers made from .50 cal cartridges or pens made from hunting rifle casings or even artillery shells crafted into art by soldiers during both world wars.  While discussing our projects my teammate Chip suggested that I paint it to resemble a traditional decorative nutcracker. I really liked this idea as it would help to identify the function of this strange little gadget (hopefully detracting from the alarm most people understandably feel when they see a grenade) and because it leans towards a strange militarized Christmas aesthetic. This military Santa Claus style has surged in the last couple of decades in conjunction with the “War on Christmas” propaganda that has happened during that time frame. Once painted it was clear that Santa would be dropping these nutcrackers from his sleigh onto the naughty boys and girls of the world.
Overall I was fairly happy with the outcome of my project. Functionally the mechanism is very consistent, though not perfect. Before any testing I expected the striking lever to obliterate whatever nut I placed in its path. This turning out not to be the case was great as it resulted in a genuinely useful device that can soften the nut up for easy opening. Aesthetically I am very happy that my vision of a plain grenade was superseded by the classic nutcracker aesthetic. In addition to making the grenade a bit less threatening it also reminds me of childhood Christmases. Adding details like teeth and tonsils to the “mouth” of the nutcracker or the gold epaulets and buttons on his jacket made it look goofier in the best possible way. I had not painted in a long time so this part of the project was a lot of fun!
Despite all the successes there are some issues with the nutcracker. The mechanism is difficult to reset and, due to the naturally low cycle numbers grenade trigger mechanisms commonly see, the spring and pin are already showing some signs of wear. Similarly the paint around the impact area of the striking lever and anywhere else that sees contact with other surfaces has already mostly chipped away. It may be possible to rectify this with a primer appropriate for painting onto steel.
Going forward I may look into improving the paint job and then this will likely come out every year around Christmastime when pecans are in season. I don’t know if the grenade nutcracker is going to be the next .50 cal bottle opener but this was a very fun project and I look forward to displaying my, more functional than most, holiday nutcracker.
References: http://www.inetres.com/gp/military/infantry/grenade/hand.html  http://www.germanclocksandgifts.com/nutcrackers  http://www.copperartmuseum.com/#!military-art-room/c15a9