Fine Foam Blaster Accoutrements
Consider yourself warned, the following modification guide illustrates an irreversible modification to the Nerf Stryfe, attempt these modifications at your own risk.
The build outlined here is based on my prototype 3s full-auto Stryfe
Installing the components for the full-auto mechanism will require modifying areas of the shell to allow for proper clearance of moving parts. The shaft of most 130 motors will be too long to be correctly seated in the gearmotor and will need to be trimmed. The axle on the gearmotor is too long and must be trimmed to be flush with the face of the crankwheel.
Start by removing all the stock electronic components.
This side of the shell will require the most modification. One last warning, once these modifications are made they are irreversible, your Stryfe will no longer have portions of the shell that the semi-auto pusher arm requires to operate correctly. To create clearance for the gearmotor to seat properly remove the topmost rib just above second rib that is above the main post that the pusher slides along.
To use the revswitch mount remove the lower right portion of the existing revswitch mount and trim the screw post so it's flush with the top of the mount. The trigger switch mount just drops in on top of the existing webbing.
You may or may not encounter clearance issues in 3 places on the left side of the shell. To allow the pusher arm full range of movement shave down the side area that is furthest toward the front just on the other side of the jam door access area. Further back, opposite of the crankwheel shave down the area where the m3 screw from the crankwheel rubs against the shell. Also, opposite of the crank wheel shave down the inner-top of the shell where the top the crankwheel/connecting rod orbit rubs. If you want to be more precise close the blaster up run the pusher cycle and rub marks will appear opposite the crank wheel, the forward area should be shaved before closing up to prevent possible damage to any pusher components.
The pusher motor shaft should be trimmed to 8mm, you can use the printed motor shaft guide if you are using a 130 size motor. The motor used in the test build is an MTB Honeybadger with a 10mm shaft. When trimming, it's better to be too long, go slow and remember to chamfer the end of the shaft to aid in sliding the pinion gear on. You will need the pinion gear found on the motor that comes with the TT gearmotor. The best method I've found for removing the pinion is to pry up with a pair of wire cutters, just keep scooting the jaws of the wire cutter forward as the motor shaft slides up to maintain leverage. I've found that the pinion doesn't pop off until the shaft has been pulled really far out of the housing, removing the pinion will destroy the included motor. Gently tap the pinion on your pusher motor and check for proper alignment when seated in the gearmotor body.
The gearmotor axle is too long and must be trimmed flush with the top the crankwheel to allow for the connecting rod/crankwheel assembly to rotate. You should use the printed axle trim guide to bring its length down to 4mm. Chamfer the edges of the axle to aid in mounting the crankwheel.
If you are using the 1:90 variant remove the back of the gearmotor case to properly seat the pusher motor. For all variants, tabs on the top and bottom of the case will also need to be shaved to allow the gearmotor to lie flat in the shell and to allow for clearance of the pusher arm.
Use the stock voltage limiter mounting point to anchor the gearmotor mount to the blaster shell. Any short interior screw will be re-used to screw the gearmotor down on one side and 1 m3x20 button head screw to secure the other side of the case. Mount the crankwheel to gearmotor axle, press the bearings into the connecting rod, and drop the pusher arm in remembering to use the collet piece to hold the pusher down. Use plastic friendly lubricant on all pusher arm surfaces that will move along the ribs in the shell or ride along the main screw post. Connect the crankwheel and pusher arm to the connecting rod with m3x6mm button head screws, m3 washers should go between the rod/arm and rod/crankwheel connecting points. Wiring is similar to what is found in a Rapidstrike rewire, the microswitch is tripped by the crankwheel alternating the pusher circuit to ensure that the pusher returns when the trigger is released mid-cycle. To prevent runaway on 3s you must incorporate a buck converter to step down voltage to the pusher motor. Step the voltage down until the runaway stops. Only 3s has been tested so far, on 2s builds the use of a buck converter may be unnecessary.
Short story is it works, but needs lots of optimization. Future updates will be coming on the half length variant.
Overall I'm fairly happy with the prototype, ROF hangs somewhere between 8-9 DPS and FPS numbers are in the high 130s under sustained operation with a mid-crush flywheel cage, the crank-slide pusher should prove more reliable over spring-loaded rack and pinion style pushers. With this approach there is no spring-loaded pusher slamming into the primary pusher post continually - which eventually leads to cracking that post and a dead Stryfe - or maybe one that will need a good amount of glue to bring back into full operation. While both the 1:48 and 1:90 variants of the TT gearmotors do work, I've been able to achieve more consistent results with the all metal 1:90. With the 1:90 it was easier to tune out the runaway, with the 1:48 while it is very satisfying to crank up the DPS there was no reliable way to control runaway. I strongly suggest using the all metal or half-metal 1:90 TT gearmotor over the 1:48.
Chronograph testing results were recorded with a 3s lipo @11.8v, 18 round Nerf mags, and Adventure Force darts. I cycled 7 mags total or 126 darts.
Sustained 136FPS @ 8DPS feels like a good starting point for further optimization.