Recently, as a fun afternoon’s diversion, a good friend bought each of us a Nerf Stryfe.
For those of you unfamiliar with the Stryfe, it’s a foam dart gun, using a twin fly-wheel arrangement to fire the darts. When the lower trigger (located underneath the middle finger) is depressed and held on, the flywheels motors switch on and after a few seconds reach their maximum speed. The main trigger is then pulled, pushing the loaded dart into the gap between the flywheels, which grip the dart and fire it forward.
The stryfe takes 4 AA batteries, but I wanted to run it on a 9V battery, because that’s the largest battery I had laying around that wasn’t half as big as the gun itself. Below is a picture of my stryfe with a modified battery compartment cover, to allow the wider 9V battery to be installed. Note: there are plenty of posts out there about modifying the internals, but I didn’t bother going to overboard (though there are some resistors inside that you may want to remove).
I just soldered a standard 9V battery connector onto the rearmost battery terminals, as shown below. This allows me to use the 9V battery, while still allowing me to go back to 4 AA batteries if I decide to.
Note that you also have to cut out a section of the battery divider (between the two sliding orange battery restraints, see picture below), in order to make space for the 9V battery.
Original battery compartment cover, and my 3D printed cover.
For the 3D model of the batter compartment cover, refer to the design on thingiverse: http://www.thingiverse.com/thing:392664/
Note: If you’re going to run your Nerf on greater than 12V, you will need to deal with the PPTC inside (basically an auto-resetting fuse). I put up a post about that here: https://teslaandi.wordpress.com/2014/07/18/12-v-modification-for-nerf-stryfe/
Note: when modifying a Nerf, I find it handy to keep the cardboard box that it came in, and as I remove each screw, I press it into the side of the box, in the corresponding location on the picture of the gun. This way I never end up accidentally putting a short screw where a long screw should go, or vice-versa.