Digital.Complex: [nerf] Rayven CS-18 (N-Strike Elite/Stinger) - Digital.Complex

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[nerf] Rayven CS-18 (N-Strike Elite/Stinger)

#1 User is offline   aotsukisho 

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Posted 04 December 2013 - 10:01 AM

I've always admired bullpup designs, which is the reason why I've wanted a Rayven pretty badly for a couple of weeks now. We put in an order through Amazon and got several of them and I'm liking what I'm seeing already.

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Rayven as it is straight out of the box

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space for AA batteries on the side. I actually do try out each blaster in stock form to see how they are.

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the main complaint about bullpup designs are trigger feel, and the Rayven is a mechanically linked plunger design so the pull is a bit harder than most blasters.

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There's not much going on in the front of the blaster. In fact, there's not nearly as much going on inside the shell as a whole compared to the Rapidstrike.

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Inductors sitting on top of the motors

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wiring for the magwell switch, so you can't fire unless there's a mag equipped

I took a little sidetrack for a bit, since I still have my second Rapidstrike open without wiring. I heard from forums that the Rayven and Rapidstrike have different flywheels, which makes sense since technically the RS is newer than the Rayven by a few years. I needed to personally verify these claims, so I compared the two fairly in-depth.

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side by side with the top shell off

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Interestingly the Rayven has a longer barrel. However, the RS has a rifled one while the Rayven does not.

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All of the Rayven switches were the ones on the left, with the black plunger. The RS SPDT switch is on the right for comparison, it's a little larger and with a longer plunger.

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I removed the inductors from the Rayven's cage and here's a side by side comparison with a slightly modified RS flywheel cage

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top of the cages

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top of the cages removed to expose the flywheels. kind of interesting how they're straight up complementing colors of each other.

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pulled off one flywheel each to check em out.

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Weighed both of the flywheels, the RS wheel came in at 4.0g and the Rayven at 3.3g. It kind of makes sense since the Rayven is only AA powered, where the RS has the benefit of using C cells.

Okay, comparisons done. Now for a teardown of the Rayven internals.

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might be just me but I found the accel trigger of the Rayven to be needlessly complicated

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closeup of the motor's inductors.

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I found out that they drilled out the Philips head on one of the screws for the rubber shield thing. I dunno why they did this since the screen is flexible enough that I just stretched it around the washwer and got it off anyway

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and after I pulled off the screen, there was enough free space to get my pliers' teeth around the screw and remove it.

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desoldering the motor legs from the pcb

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here's the stock brushes, unsurprisingly the metal variety. If I want to reliably put higher voltage through the motors, I'm gonna have to swap the brushes for something that can handle more punishment.

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now where have I seen carbon brushes in huge abundance before...? I quite literally have a small box full of stock Xmod/Mini-Z 130 motors, and they all come with carbon brushes.

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comparison of the two. Which one would you use?

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I took a look at the motor endbell, and found that there wasn't even a bushing on the stock motor. Time to swap endbells too.

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It's a lot easier if you put the brushes like this first

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then carefully slide the endbell on

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like so. I tested the leads to make sure the motor spins before I crimped the motor can back onto the endbell.

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Xmod gen1 endbell vs stock. The vent holes are larger too

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starting to wire up the motors. Diode connected in reverse to prevent back-EMF spikes from letting off the trigger. The carbon brushes made a big difference, as did the bushing in the endbell.

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sanded off these nubs on the main trigger and the accel trigger secondary piece to bypass the accel switch lock.

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pulled out the AA contacts so I can start work on the battery box

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view from the inside, with the spring solder contacts gone.

I'm really looking forward to finishing up the Rayven. It's a blaster with plenty of potential only limited by its relatively tiny battery tray. The biggest challenge I think will be to figure out how to mount the accel trigger switch.
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#2 User is offline   aotsukisho 

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Posted 04 December 2013 - 11:50 AM

I attached a tentative schematic of the Rayven's electrics. Being that there is not automatic gearbox like the RS, it's extremely simple.

The capacitor is there to help with the current surges whenever the motors have to spin up. It will probably be less noticeable with a lipo, but goddamn the flywheel rpm sags whenever a dart is fired. I may be able to drop it to 1000uF or so (or maybe eliminate it altogether) but bench testing will have the final say.

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#3 User is offline   aotsukisho 

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Posted 05 December 2013 - 12:13 PM

Finished up the Rayven.

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Gutted the battery compartment with a dremel.

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tentative exit point for the battery wires

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avoiding a pinch point with the magwell lip

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I was trying to figure out how to mount the switch inside, when I took the piece out and looked at it and then inspiration hit

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I melted (guess what!) an Xmod bushing to use as a sort of two-piece nut

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fucking genius

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mounted up properly. I only used the caphead in the earlier picture since it's a 3mm hex and thus more torque for tapping threads in the plastic.

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mockup of switch location

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trigger fully depressed

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mockup inside the gun. I found that if I used 1/8" thick plate, the switch was literally at the perfect height. I cut some scrap steel to add some weight to the handle of the Rayven and used a mounting screw to attach the switch to it.

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can't really tell, but this is after a run or two of hotglue.

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neutral

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fully depressed. Switch is activated without the plunger being smashed into the switch body.

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there's a reason why the space behind the switch is there, the Rayven shell has these ridges that go over each other to secure the position. The one on the top shell is larger than the one on the bottom and slides over it, so there needs to be space for it to go when the blaster is put back together.

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fully sunk in hotglue. there's about an entire stick's worth underneath the plate.

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one last look

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Wired all up. I just bought one huge roll of black wire since it's too much trouble to go color coordinating when I only do one wire at a time anyway

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completed wiring with a ziptie around the barrel to tie up the slack in the wires. Note that the support piece right at the end of the flywheel cage is mirrored on the top half of the shell, so I had to move the wires out of the way because they got pinched the first time.

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2.9A peak while shooting half of a mag to test the gun. This is much less than I expected, although I suppose the capacitor in the design does buffer a lot of the surge current out of the battery. However, the lipo I was using was extremely old (the first lipo I ever bought in fact, for a Mini-Z). The voltage sagged to 7.3v, which is definitely not good considering it was nearly fully charged. A newer, higher C lipo will definitely improve performance but as it is now, it's much better than stock.

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put back together, with a Spectre barrel extension. It looks pretty good, I think.

I just have to figure out what's the biggest lipo I can fit inside the tiny battery compartment, and we should be good. Rayven Mk.I complete!
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#4 User is offline   aotsukisho 

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Posted 08 December 2013 - 06:34 PM

raw dimensions of the Rayven's battery compartment are approximately 56x63x14mm. I was looking with Steve on ways of mounting a battery, and we realized it would be easy to mount a lipo inside of the buttstock. The dimensions of that, with a little clearing of the plastic, are 57x66x22mm. That's a lot more space to work with thickness-wise, which was the main limiting factor for 2s lipos.
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#5 User is offline   aotsukisho 

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Posted 30 December 2013 - 06:30 PM

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I got some cheap 7-segment LED voltmeters off ebay, I figure precision isn't necessary when it's just there to make sure the batteries aren't too low

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top side

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bottom side. I'm assuming the pot is there for calibrating, although checking with my multimeter it's only 0.01v off so I didn't bother.

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cutting a hole for the lipo wire

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cleaning out the internal plastic. These were where the unused trigger lock went

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there is a slight level change in the inside plastic due to the design of the blaster, so I used this thin doublestick tape to kind of level things out

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still not completely flat, as you can see from the shiny bit, but better than it was before

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lipo is stuck on. The tape was rated for 10lb holding strength, so I think it should be fine.

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eyeballed a position and mounted the voltmeter using old Traxxas pivot balls as spacers. The M3 screws are a perfect fit for the mounting hole

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mockup with everything installed. The BEC fits perfectly underneath.

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dremeling out the hole in the battery cover

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from the outside

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it can use some cleaning up

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Well shit I messed up my measurements.

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sidetracked a bit when I noticed that I had to cut the magazine release latch a little bit so it didn't rub on the lipo wires

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not using the BEC for now because I ran out of Deans lol

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lipo connected

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an almost-fixed cover reinstalled

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by carefully selecting screw length, I avoided having anything protruding into the magwell.

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it's not blindingly bright in the dark, but I think it'll still be visible in sunlight.

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finished!

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having an 850mAh 3s lipo in the butt really makes it rear-heavy, even pinching it on the back of the tactical rail it still teeters

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having a Retaliator barrel on it helps a bit.
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#6 User is offline   aotsukisho 

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Posted 21 January 2014 - 03:18 PM

I upgraded the Rayven Stinger with the intent to sell it. All of the modifications are with the intent of having it being easy to use without all of the cumbersome locks, while not having to invest in lithium chemistry batteries to keep the cost down. Before the photos, here's a list of stuff that has been done to it.

MOD: Removal of mechanical/electronic locks and motor inductors
PROS: Easier operation
CONS: Nothing, locks are just in there to avoid lawsuits
EXPLANATION: I would like to think that everyone that Nerfs with us has the brains to realize that stuff moves around inside, and maybe you shouldn't stick your finger in there when you're using the thing. It's nice to be able to view the function of the blaster without having all of the equipment installed (ie. pull the trigger without a magazine loaded). Also, being able to rev the flywheels whenever you want can be used as an intimidation tactic. The motor inductors are there for a reason the Nerf community can't really decide on, and all they do in our case is impede performance so they are removed as well.

MOD: Motor armature replacement
PROS: Longer shooting distance, louder noise
CONS: Shorter battery life, louder noise
EXPLANATION: The stock armatures have more turns than the Xmod ones, which means they produce more torque but don't spin as fast. By increasing the idle RPM of the flywheels, we can force the darts through with more velocity. The capacitor bank modification helps with this one, it's a package deal. The noise is listed under both pros and cons because most people would consider more noise a drawback but like I said earlier it can be used as an intimidation tactic. When you hear your opponent's motors rev up the first thing you're concerned about isn't usually whether or not they have ammo. The con is of course decreased battery life, because you don't get increased range for free.

MOD: Kickback diodes
PROS: Lower wear and tear on the acceleration trigger switch
CONS: None
EXPLANATION: I'm not sure why these aren't already there from the factory but whatever. When power to the motor is disconnected, the coils in the motor will attempt to push an extremely high voltage backwards which usually ends up arcing on the switch contacts (it's the same principle if you've ever pulled the plug on a vacuum cleaner that's still running). This arcing (voltage kickback) will pit the switch contacts, and eventually it will leave the switch unusable because it will have a high amount of resistance. What the diodes do is essentially short circuit this kickback and render it harmless.

MOD: Capacitor bank
PROS: Less motor RPM drop
CONS: Marginally heavier
EXPLANATION: Because the Xmod armatures draw more power than the stock armatures, the AA batteries will be undergoing more abuse as the current spikes will be higher. The capacitors minimize the voltage drop by being able to dump current a lot faster than the AAs can. The motors will recover their RPMs faster, whether it be from shooting a dart or revving from a standstill.

MOD: 18AWG wire replacement
PROS: Maximize electrical efficiency
CONS: Marginally heavier
EXPLANATION: The larger diameter the conductor the lower the resistance which means less power is wasted traveling from the batteries to the motor. The stock wire is somewhere in the 24+AWG size, which is tiny for how much current these motors actually consume. This combined with removing the interlock switches and thermistor means the circuit has a lower resistance. 18AWG has roughly 25% the resistance of 24AWG, and 16% the resistance of 26AWG and that's assuming the factory wiring is of high quality.

I am asking $40 for this blaster if anyone is interested. With that said, enjoy the photo log of the modification process.

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Rayven out of the box

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cracking open the shell

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quick shot of the side with most of the electronics

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and the one random switch in the rear that isn't even necessary

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pulling out the accel trigger assembly

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pulling out the rear trigger locks

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removing the flywheel cage

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those armatures are from Xmod gen1 Stage 1 motors, which are rated by Radio Shack at 24krpm @ 6v. The fact that they will be spinning a load, plus the fact that they are going into the stock Nerf motor cans which have stronger magnets, means that they will not be spinning near that fast.

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comparison of the armatures. The Xmod-supplied one is on the left, the Nerf-supplied one is on the right.

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frontal view

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both armatures replaced

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kickback diodes installed, soldering on the wires

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side view

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dart curtain thing reinstalled

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I used four capacitors out of a broken Xbox360 to make a capacitor bank. This one in particular is a 6000uF 16v setup that I will use in parallel with the batteries in order to minimize current draw out of the AA's and help the motors recover after firing darts.

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crappy photo of hotglue treatment to minimize physical fatigue on the caps

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these two holes on the pcb will line up with the old lock mounts that aren't in use anymore

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starting to wire up the blaster

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finished wiring

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setup of the switch, with a dab of lithium grease to help the mechanism slide smoother

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guts reassembled

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ready to put back together

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finished product.

As I said before, I'm asking $40 for this blaster; it comes with the 12 round magazine and the unopened package of darts. It was a technical exercise for me balancing modifications with cost, and the largest barrier to 'serious' performance has been the cost of buying lithium chemistry batteries and their corresponding chargers. You can still use AAs in this blaster (rechargeables will work better but alkalines still work), and I will be posting videos of their performance whenever the weather cooperates.

ps. The Rayven Stinger color scheme is very similar to the old N-Strike line, so you can get older blasters' barrel extensions that match nicely. The Recon barrel goes nicely since it's basically the yellow version of the Retaliator barrel we use on our NSE Rayvens, and also the Longshot has a large but yellow barrel attachment. Recon barrels pop up on ebay for under $10 all the time.
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#7 User is offline   aotsukisho 

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Posted 27 January 2014 - 02:45 AM

I finished editing the videos to compare the before and after performance of the Stinger.



The stock one shot 18-21 paces while the modified one shot 26-31 paces, with one strangely going much further but I'm considering it an anomaly.

Pay attention to the sound of the motors in the first segment compared to the second, the recovery time of the RPM is slightly faster which is good considering those motors draw a lot more current. The range is increased, and the fire rate capability is faster due to the RPM not stalling for as long.
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