1

Topic: 100 NERF dart dual-drum magazine

I just got my NERF Hyperfire today...and was disappointed how quickly it emptied its 25 dart drum.
Since I previously looked at the benefits of making a 3D printable 35-dart drum, I have decided to try again with two 50-dart modules that combine for a total capacity of 100. With the Hyperfire (5 darts/second), that should give 20 seconds of firing time instead of 5.
Wikipedia article: https://en.wikipedia.org/wiki/Drum_magazine
Since this isn't offered by NERF (yet), it's totally reasonable to put in the effort to design this thing, even though it will be quite a challenge.
My current plan is to use a Fibonacci spiral to maximize the usage of internal drum space, thus making it as compact as possible (and therefore more compatible/faster to print). Each module will be a separate piece that will be joined to a central feeder, which will alternate intake while guiding the darts into the blaster's chamber. The shape of these pieces will be ideal for a Cartesian printer, since they are bigger in the XY coordinates than in the Z coordinate.
Besides the springs and standard metric hardware, I also plan on keeping the clear panel on the back that is found on the stock NERF drums. To do this, I will build and use a vacuum former with a 3D printed positive and a sheet of transparent plastic, which then gets cut, drilled, and screwed onto the corresponding module.
Just like the stock drums, I will also try to add a jam clearing/manual unloading mechanism, which may also include access to the spring for tensioning/replacement.
If anyone else is interested, I am open to ideas and will gladly accept any help I can get.
My printer is 240x240x170mm, so have enough print area for any reasonable prototypes.

Filastruder 2607 w/ Filawinder @1.75mm.
Dual-extruder MaxMicron Prusa Mendel: RAMPS 1.4 w/ Repetier Firmware+Full Graphic LCD Controller, stock hotends, 3Dator extruders w/ MK8 gears, insulated enclosure w/ 2 heat lamps, RPi 2B w/ Repetier Server.
0.1-0.2mm layer height, heated bed w/ PEI surface, inductive-sensor autolevel, 0.5mm to 0.2mm nozzle diameters.

2

Re: 100 NERF dart dual-drum magazine

Okay, I've been thinking about the requirements for this design to work, and I've determined them:

  • The clip must be loaded from the top, from empty to full capacity

  • All of the darts must reach the retainer at the top as the magazine is emptied

  • None of the darts should be subjected to extreme pressure or shear force during the loading/unloading cycle

  • The force pushing the darts to the retainer needs to be strong enough to push the last dart to the retainer, but weak enough to not pop out darts when the magazine is full

  • The part of the magazine that interfaces with the blaster must function like every other clip system magazine (same height, length, width, retainer, notches, etc.)

  • The center "T" must be capable of alternating feeds from the drums to make a single-file dart output at a high rate (at least 5 darts/second)

The first and second requirements can be dealt with by interlocking feeder chains: in the drums, they occupy X number of dart spaces, but in the "T" they combine to occupy the entire space of the "T" except for the retainer. Likewise, the chains also separate in the "T" during loading, and guide the alternating darts into each drum.
The third and fourth requirements are dealt with by a very specific spring tension, and a combination of a Fibonacci spiral and compartment walls to segment the force applied to each individual dart, while still guiding them into position. The result is that the maximum force applied overall is to the darts in the "T" when the magazine is full, which is much easier to manage than an entire drum of darts.
The fifth and sixth requirements simply dictate the design of the "T," which will probably contain a tapered wedge and filleted corners at the junction. The rest of it will consist of the standard magazine top and side connectors for the drums.

Filastruder 2607 w/ Filawinder @1.75mm.
Dual-extruder MaxMicron Prusa Mendel: RAMPS 1.4 w/ Repetier Firmware+Full Graphic LCD Controller, stock hotends, 3Dator extruders w/ MK8 gears, insulated enclosure w/ 2 heat lamps, RPi 2B w/ Repetier Server.
0.1-0.2mm layer height, heated bed w/ PEI surface, inductive-sensor autolevel, 0.5mm to 0.2mm nozzle diameters.

3

Re: 100 NERF dart dual-drum magazine

I just got some inspiration from the NERF 25-dart drum to fix a problem I found with the current idea.
The biggest hindrance from a Fibonacci spiral is that the darts are stored at different distances from the center of the drum. This means that whatever connects the feeder chain to the center spring needs to be able to change its length. The feeder head in the 25-dart drum has to perform a similar task: to empty the darts in the top part of the magazine, the hidden post that the head is jointed to expands to push the last darts upward. This appears to be accomplished using a spring in the "hub" of the drum.

Filastruder 2607 w/ Filawinder @1.75mm.
Dual-extruder MaxMicron Prusa Mendel: RAMPS 1.4 w/ Repetier Firmware+Full Graphic LCD Controller, stock hotends, 3Dator extruders w/ MK8 gears, insulated enclosure w/ 2 heat lamps, RPi 2B w/ Repetier Server.
0.1-0.2mm layer height, heated bed w/ PEI surface, inductive-sensor autolevel, 0.5mm to 0.2mm nozzle diameters.

4

Re: 100 NERF dart dual-drum magazine

Scrapped the Fibonacci spiral idea for a much simpler one.
The drum itself consists of 4 rings of darts and a frame with a hairspring, guides for moving darts from one ring to another, and mounting points for the rings and gears in between.
Each ring has inner and outer sets of teeth on the bottom, that mesh with the gears between the rings. The ratios are such, that the darts in the rings move in a 1:1:1:1 ratio to each other, allowing the guides to move the darts safely.
The current drawback to this design is that the drum only dispenses darts at the outermost guide, and cannot be used in a dual drum design without a pusher going into the clip.

Filastruder 2607 w/ Filawinder @1.75mm.
Dual-extruder MaxMicron Prusa Mendel: RAMPS 1.4 w/ Repetier Firmware+Full Graphic LCD Controller, stock hotends, 3Dator extruders w/ MK8 gears, insulated enclosure w/ 2 heat lamps, RPi 2B w/ Repetier Server.
0.1-0.2mm layer height, heated bed w/ PEI surface, inductive-sensor autolevel, 0.5mm to 0.2mm nozzle diameters.