Made the Rear.stl walls slightly thiccer by 0.75mm.
Spring guide in the Mag Base.stl is now taller, this will prevent the mag spring from tangling and prevent the follower from going further down than it needs to, which also tangles the spring.
Changes reflected in .STEP file.
04/02/2024
Added a new Mag Securing Block built into the Riser, this will help push mags down into the correct position and acts as a guide for mag insertion, held in place with a new Top Rail. Requires a new Compression Spring, 5.5mm OD, 35mm Length (Same one in the Mag Ejector)
Rack has been made slightly beefier, with a shorter front end to prevent it striking the turnaround extension spring as much.
1.5mm fillet added to cage to prevent extension spring sticking to the side of the cage (hand filing the side of the cage will also help clear this)
Changes reflected in .STEP file.
28/12/2023
Adjusted Dart Lock, Mag Feed and Follower magazine prints to print easier and work slightly better with 38mm long and older darts. Preferred dart is still Worker Gen 2 HEs.
30/11/2023
Added stock.stl and stock alt.stl
27/11/2023
Updated hardware list and wiring diagram with MOSFET information
25/11/2023
Published
This is my attempt at creating a top loading P90-esque Nerf blaster, the GnK-90!
GnK-90 features 2x 2004/2104 size brushless motors and 40mm wheels, hitting around 190fps from my testing on 1g Worker HE darts, solenoid control using either a generic 35mm solenoid or FTW Hyperdrive, with added select fire. There are 2 select switches located behind the foregrip for select fire or select RPM, allowing presets for how fast you want the motors to spin. Also included is a 19mm OD barrel, which allows fitment of Worker faux muzzles.
I opted to adapt Worker Talon mags to feed them at a 90 degree angle and have them turn around inside the blaster into the flywheels, so I designed a few adapter pieces that slot onto the mags, no shell cutting needed and its completely reversable. Using straight talons allows for an 18 dart capacity, and angled talons allows for 21 darts!
I chronoed this blaster to approximately 190fps, this may be higher or lower depending on your build quality and motor setup, but I managed this through the 2104 3000kv motors, fresh 1g Worker HE darts, on a fully charged 4s Lipo. This was also using the included Rifled Muzzle, which will drop FPS by about 5 or 10, but significantly improve accuracy. Default settings in the arduino sketch are for low RPM, 130FPS, and Max RPM. This may change dependent on your motor selection once again.
GnK-90 fits the lipo in the rear, there is a MASSIVE amount of battery space, I can fit in a 4500mah 4s LiHV with ease. Running on 4s is essential for the solenoid having enough power to work the turnaround mechanism, even with the FTW Hyperdrive solenoid.
Firmware is included, I will admit this is not the prettest, but it works to get the blaster working at a minimum. You are welcome to use your own firmware, different microcontroller, add a screen, whatever you like with this! I would love to see what others can do with this shell.
This project is licensed under the terms of the Creative Commons Non-Commercial Attribution Share Alike 4.0 license, which means you can print it, remix it, share it, and if you do and give myself credit. You cannot sell this without permission from myself.
1x IRFZ44N MOSFET with 10k resistor and 1N5400 diode (Or suitable MOSFET board)
1x Arduino Nano
1x Buck converter/BEC
2x 3 Pos switches (SS-23D32G6)
1x Subminiature Microswitch
1x 10A Microswitch
1x 4s Lipo/LiHV, 32x66x144mm max size
16 AWG power wires
22 AWG signal wires
Lube for moving parts
Below is also my preferred BLHeli_32 settings, this has worked for me, you can adjust as you like:
You can switch out and use your own electronics if needed, if you want to use different motors, make sure to double check the measurements on the flywheels and motor mounts to see if they will fit.
Turnaround Assembly:
The turnaround assembly may require work to get it operating smoothly, this really depends on your print settings and your willingness to troubleshoot friction points and sand down parts, be prepared!
Remember to grease/lube the moving parts well, this will significantly aid in operation.
Add loctite to any bolts so they do not come loose and ensure a consistent operation.
Not all solenoids are built the same! I have found the plunger rod is sometimes bent, if the rack.stl is rubbing, rotate the plunger slightly, and this will change how the rack sits on the cage.
You may need to adjust/cut down the extension spring, you can do this with snips, cutting down a coil and then twisting it to the desired angle so it can fit onto the spring block/turnaround bolts. Make sure it isn't too tight otherwise it will squeeze the rack inbetween the turnaround and spring block, causing it to stick.
A F683zz flanged bearing fits inside the turnaround and is mounted into place with an M3 bolt, I would recommend an M3 washer underneath the turnaround as well to ensure enough clearance.
You will need strong return springs on the solenoids, I used a cut down retaliator spring on my FTW Hyperdrive solenoid, trial and error will be needed for this.
Remeber to test each part individually before fully assembling, this will seriously aid in troubleshooting and knowing which parts may need adjustment.
Refer to the .step file for fitment, if necessary scale up/down parts for tolerances.
Other Build Notes:
I'd highly recommend printing the cage in PETG or any other heat resistant material, and the flywheels in ABS. I have tested PLA flywheels and they worked well enough, but you may have a different experience.
Loctite your bolts into the motors, or at least periodically check they are screwed in. I have found that using the M2 Washers for the motor mount bolts have helped significantly in keeping the motors secure without cracking the flywheel cage.
Some parts may need supports when printing, I will leave that up to you for support placement.
For further questions and support, please ask in my discord (Link in printables bio via Instagram).
MeinGonk
