An Experiment in Nerf Blaster Modification Performance

I've been dabbling in modifying Nerf dart blasters recently.  The modifications fall into two categories: appearance and performance.  Nerf "blasters" themselves fall into two broad categories: manual spring powered and electronic flywheel powered.  I've been drawn to all areas of the hobby, but have spent the most of my time with performance modifications of flywheel blasters.  I've been particularly interested in using Arduino microcontrollers to monitor and control the operation of the blaster.  You can see my published projects to date:
Most performance Nerf "mods" seem to fall into two categories: 
  • Cheap Chinese kits that are poorly documented.
  • Very cool custom builds that are complex, poorly documented, and hard to replicate.
My goal, as always, is to document inexpensive and easy to build projects geared towards a successful and rewarding "first mod" experience.  In working towards that, I've gathered quite a bit of data about what modifications provide the best performance.  Starting with the most popular modding blaster, the Nerf Stryfe, I looked at the effect of flywheel speed, motor current, and dart velocity for a number of configurations.

Batteries: The stock Stryfe is powered from 4 x AA batteries for a nominal 6V.  Upgrades to lithium polymer increases voltage (7.2 V) and significantly increases current delivering capacity.  

Wiring: The increase in current from LiPo batteries require upgrading the stock wiring to at least 18 AWG, and either replacement of the microswitches to higher rating or the use of a MOSFET control circuit.  The MOSFET control circuit lends itself well to microcotroller use, and eliminates the need to upgrade the wire to all but the short section from battery to motor.

Motors: Over-volting the stock motors would certainly be frowned upon from an engineering design standpoint, but going from 6V to 7.2V is fairly minor and I have noted no increase in motor temperatures or indication of degradation.  Given the short run-times of motors during typical use, the longevity of the motors does not appear to be an issue.  Aftermarket motors are designed for higher voltages, current, and speed.

Instrumentation: Motor speed and dart velocity are measured using infra-red emitter detector pairs monitored by Arduino.  Motor current is measure using an Adafruit INA260 breakout board attached to the Arduino.  Configuration tests are run twice, once measuring motor speed and current, and once capturing dart velocities of ten shots.  Data from the Arduino is outputted over a serial console and copied into spreadsheets.

Enough babbling.  The data!

Additionally, I was interested in the operation of the stock resetabble fuse.  This fuse limits current as it heats up, and resets itself after cooling down. This is clearly shown in a graph of current verses time for a stalled stock motor:

A lot of modders remove the fuses since the increase in current draw will trip the stock fuse quickly.  I have heard of and witnessed motor burnouts caused by stalls with removed fuses.  A novice who jams a dart on a modded blaster while continuing to hold down the rev switch with cause this in short order.  I advocating protecting your after-market motors with appropriate capacity fuses.  It is worth it if for nothing other than avoiding the smell of the magic smoke that come out!

  • It is very easy to get to 100 fps using stock motors by upgrading the battery and wiring.
  • The 2S Lipo and aftermarket motors were able to achieve near the 130 fps limit set by a number of competitions.
  • Aftermarket motors significantly decrease the motor spin up time at the cost of very high starting currents.  And noise.
  • Increase in dart speed using the aftermarket motors was only realized using aftermarket flywheels.
  • The use of 14500 Lipo batteries, while controversial in the Nerf community, appear quite compatible with the stock motor currents. These have the advantage of not requiring any shell cutting.  You will note that I did not try them with the aftermarkert motors for concern about the current draw.
  • It is interesting to note that stall current and starting current of the stock motor are nearly identical.  The listed stall current of the Meishel 2.0 motors are 18.8 A, or 37.6 A for a pair, which is close to 33 A starting current observed. This should be useful in choosing fuse size.
As in most hobbies, incremental increases in performance come at exponential increases in cost and effort.  People are spending hundreds of dollars to achieve 200+ fps blasters while experiencing diminishing, even deteriorating returns on accuracy and distance.  For now I intend to stay in the shallow end of pool while concentrating on the benefits of smart, Arduino-controlled blasters, such as ammo counting, clip capacity detection, battery monitoring, and select fire.

Stay tuned for a kit.  You may have seen a sneak peek in the first photo.

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