Tuesday, May 31, 2016


A number of readers have noticed that posts have slowed down on DZ. I haven't put up much of anything past my last action cam stuff a month or so ago.

Don't worry.

Nothing is wrong. I am just a bit busy. I still play regularly. I just played 2 HvZ events this weekend, but lately I get home from games and don't have the energy to blog about them, just stick some usual reddit/facebrick banter in here and there. Same with superstock builds, all of those are in cryo right now. I might not even bother with the Nerf Hyperfire for now, probably just the Rival Khaos, long story.

But before we get to what is going on, let's look at what is coming up for the near future.

For a while now I have been showing up in discussions of open class equipment (high velocity, stored energy) on reddit and facebrick, and been dropping mentions here and there of something called "Prometheus".

Prometheus is an ongoing development project of mine for a "kit bash" (discrete component) automatic pneumatic primary. Like many other cases, I don't just want to make my own version of the latest cool new thing, I want to jump ahead of the game, and this is no exception. I have been looking to everything that is wrong with the "current generation" openclass guns like the Red Baron, FAAG, Uglystick, and all their kin.

What I noted on facebrick:

Reciprocating barrel, pull type ram, coaxial action spring, Humphrey Products QE-3 main and 31P 3way trigger, shooting for 300fps@150psi, Upper and front top cover are 1.5" aluminum square tubing, lower is built up as in that homemade magfed flywheel thing from years ago, mounts at front with a hook and rear with screw. Internals all locate and mount on the 3 trunnions and nothing else, the trunnions and the barrel lug are the only critical dimension parts in the whole thing. Barrel is .527x5/8 aluminum tubing and breech cover and guide sleeve are 1/2" PVC schedule 40 which fits perfectly on the tubing I have. Dump chamber will stickout the side of the receiver to get it out of the way. 2" stroke and set up for short darts and Artifact mags, ram is an off the shelf cylinder probably a 9/16" bore double action like the parker one I have, with the cap side left open, or maybe a bigger one for bolt force balancing since the action spring needs accounting for there.

The basic concept is the closed bolt ram/exhaust valve engine which has been around nerf and spudguns for years. Since that post, I have changed things:

Main valve is to be a SQE-2 Humphrey, which will be much more manageable than the clunky QE-3 and yet will flow well enough for any legal nerf application (better than the majority of paintball marker valves), particularly given the operating pressure.

I have built the dump chamber, which is primarily 3/8" steel pipe, and is itself the line connecting the ram to the valve. There are no flexible lines. The chamber as-assembled will locate the valve in the receiver and itself be placed by the front ram threads. I forgot to photograph it. Volume is about 2 ci which should be about right for 150psi operation. The potential pipe tumor on the side is being reduced to a mere bulge with a cover over it.

The ram has been changed to 3/4" bore which will give me a bit more bolt closing force to allow for better barrel tuning. The 3/4" ram also relocates some dump chamber volume into the ram for slimmer profile and offers larger 1/8" NPT ports, which mean that (given proper fittings and some mild porting work) unlike the smaller cylinders with miniscule 10-32 miniature-pneumatic fittings, the air in that volume is not becoming wasted energy on throttling losses (an issue apparent to me in i.e. the Red Baron's extensive tiny hose runs between ram and dump chamber).

The grip frame concept still holds, the 31P is still going in there, and everything else.

Mandatory mention that Google Sketchup sucks, don't bother hating on my mockups, I hate it too. I am slipping toward yet another hand fitted prototype, as I have a history of, because of the lack of working CAD. Anyone know of a good 3D noncommercial CAD package?

Okay, now as to what is going on right now.

It isn't nerf. Well, wait. It is actually nerf equipment. I drive it to every game.

1993 Suzuki Sidekick LWB 4wd:

The 4 speed Aisin transmission that is in mine is not in a good state. 23 years of deferred maintenance before my ownership of this rig has taken a toll. So I have been putting together a 5 speed for it. Countershaft section finished:

Mainshaft parts all cleaned and inspected. Still waiting on a few to arrive.

The core I started with came out of a 1997 Geo Tracker (which is a rebadged Suzuki Sidekick) and supposedly worked OK. Well, one look and I wasn't about to put it in my car. The trashed input shaft and wasted bearings were apparent from the outside. Removed shifter, saw a bunch of metal particulate, uh-oh. Tore it down, found a munchy looking 5-R slider and reverse gear. Both getting replaced. Other gears all good.

I'm about a weekend away from having it assembled. It doesn't help that a supplier sent me an input shaft with a chip out of it from poor packing (shipping damage) and is now unreachable (never buy from American Powertrain Warehouse) so I am most likely out $62 and have to wait on a new one from another source. All changeover parts (wild geese, unobtanium Suzuki hardware) for the truck have been chased down to the last 2 dowel pins. Ahead of me is swap day, and this sort of stuff putting freshly worked-on equipment in service is always stressful as hell, but it will be a relief afterward. Thing's been going downhill for years and the thought of it cratering completely has been a constant burden.

All along has been the matter of my employment, slowing things down, nerf and otherwise. My primary hobby workshop is in a different city. I work late nights at a hard job all week, get nothing done while off work, and then have 2 free days to take another chip out of a project, then repeat. Oh and I just finished moving to a new apartment. So cut me some slack. Some of you guys on reddit who have given me heat about lack of new nerf content just joined r/nerf within the last 2 months, particularly you, you know who you are, you have attracted my unwanted attention. How about you take a look at my history before you make accusations like that; and on top of that, not to be elitist myself but you routinely take for granted stuff I helped lay the groundwork for. You have shown up, posted stuff that flat out entered the community because of me, and then flamed me for having the same answer. I am not sure if you are just too green to realize people have years of backstory in the nerf world or just egotistical and want to pick a fight, but get a grip, you little shit. I'm not your enemy.

Sunday, May 22, 2016

Misadventures with an Apollo (and PSA: those gears break pretty easily)

This post is the unfortunate result of a late-at night whim for a quick and easy mod project, and is more of a collection of miscellaneous notes and a don't-do-this guide than a mod guide - if you're looking for an Apollo mod guide, Mag212 has a pretty good one on Youtube, although there are some potential "gotchas" that he doesn't mention that I suspect lead to a gear breaking in mine. (If you'd just like to hear about that, go ahead and skip to the end.) I had an Apollo lying around, which I initially bought as part of a project to asses the effectiveness of Rival rounds. It hasn't done much since then, and it isn't the sort of blaster that I'd usually use - but it might make a decent sidearm, especially for a non-dart loadout. My line of thinking was "I'm probably going to sell this or give it away, so I may as well make a holster and mod it first."

This is a standard duck tape holster with epoxy rim re-enforcement, silver duck tape on the outside, and aluminium tape around the rim. The rigid panel at the back (not visible from this angle) was made from some disposable chopsticks, and the velcro strap comes from some scavenged scraps. The tab that you see on the end of one of the velcro strips was made by folding the end over and gluing a short section of the velcro to itself.

If you want to copy this holster, you'll want to sand off the nub on the front of the bottom of your Apollo's trigger guard - this makes drawing and re-inserting the Apollo much easier. Also, the Apollo's upper tac rain has a slope on the back, and it's slightly easier to holster if the tac rail is turned around so that this slope is on the front. This piece is designed so that it can only go in one way around, presumably to prevent accidental backwards insertion during assembly, but it only takes a little bit of careful cutting to overcome this.

The holster was a quick and easy build and, overall, it turned out very well - which makes what happened when I turned my attention to the inside of the blaster all the more frustrating. 

I tried to make this Apollo quieter by padding the plunger head. This is a piece of padding that is supposed to go under the feet of furniture, cut to shape with an Xacto knife after being stuck in place, and with the stray fibers at the edge burned away with a lighter. Subjectively, this seems to make the blaster a little bit quitter - but it's still darn loud. The thickness of the padding that I used is slightly less than the length of the four nubs that protrude from the front of the plunger head, so this allowed the plunger rod to travel slightly further. I didn't think that this was going to be a problem at the time, but this might have contributed to a gear breaking.

This air restrictor is a little odd. It seems to be designed to push the ball forwards by a small distance, where the barrel is just slightly narrower such that it seals around the ball. I don't think that this is a necessary for the blaster to fire - it only takes a very small waft of air to push the ball forwards and form a seal, so the ball will only leak a little air if it isn't pushed forwards before firing - but this might have a small impact on performance. Secondly, and perhaps more importantly, this air restrictor doesn't actually do much to restrict air. The plate at the back of the AR is full of holes and too small to completely cover the hole at the front of the plunger tube. Overall, I'm not sure what effect an AR removal has on an Apollo's performance, but I suspect that it improves things a little. I'll leave that for someone with access to a chronograph to test.

I removed the air restrictor, because otherwise the plate at the back of the AR would transmit the brunt of the now-flat plunger head's impact to the webbing that normally supports the AR, and I didn't want that webbing to break.

The extension spring on the trigger is easy to accidentally overextend - but it isn't a big problem if it is, as it can be replaced with an elastic band.

There are several locks under the priming bar of the Apollo. The rearmost of these prevents the blaster from starting to prime the blaster unless the plunger rod is in its foremost position. This lock looks like it might do a little to absorb some of the brunt of the impact of the plunger head. Carving down the middle tooth on the top of the lock may therefore be preferable to removing it entirely, and that's what I did.

The rack on the plunger rod that interfaces with the geartrain sits on a sled, that slides within the plunger rod. If the blaster is re-assembled with this sled in the wrong position, the blaster may be unable to prime (if it's not in contact with the geartrain), or unable to prime far enough to catch (if it's a little too far forwards) - or, worse, the blaster might end up in a situation where the geartrain takes the brunt of the impact of the plunger (if it's too far back). This is the biggest "gotcha" that I found inside the Apollo. I suspect that this could have been how I broke one of my Apollo's gears. The fact that the plunger rod could travel a little further forwards before being stopped by the front of the plunger tube could also have been a contributing factor.

After reassembling the blaster and test-firing it a few times, part of one of the teeth of the third gear from the back chipped off. Part of the tooth remained, with the result being that the gearbox would run smoothly while not under tension, but the gears would jam if under tension - meaning that it took a while to realize that a gear actually was broken!

There are a few lessons to be learned here:
  • From a modder's perspective, blasters that prime using gears suck. (We knew this already.)
  • If a blaster that primes using gears acts funny in some way that doesn't seem like a broken gear, it might mean that you have a chipped gear.
  • Padding the plunger head of an Apollo doesn't help (much), and can cause other problems if the padding isn't thick enough.
  • Take care to ensure that the sled with the rack inside an Apollo's plunger rod is properly positioned during reassembly. In particular, if it ends up too far back, the geartrain will take the brunt of the plunger's impact during firing. Keep in mind that the geartrain will be driven slightly when the piece with the priming handle is inserted into the gearbox. You might want to keep the left half of the gearbox's shell off, so that you can temporarily remove one of the gears - the gear with the flat top comes out easily - and manually adjust the position of the aforementioned sled after inserting the piece with the priming handle and before closing the gearbox.
This is probably just the sunk cost fallacy, but right now I'm sorely tempted to get another Apollo just so that I can throw its non-broken guts into this blaster and have something to go with the holster that I made - with the alternatives being to either scrap the blaster or throw on a little decoration and keep it as a wallpiece.

Thursday, April 21, 2016

An interesting data point on multi-stage flywheels

A few years ago, I wrote a post exploring the possibility of stacking flywheel cages to achieve higher velocities. This was written mostly from a theoretical perspective. At the time, there was very little actual data on how much velocity could be achieved with such systems - very few people had made multi-stage flywheel systems, and those had a pesudobarrel in the middle which dropped the velocities that could be attained well below the theoretical maximum.

As you might recall, the simple model that I used predicted that the glass ceiling velocity of such a system would be equal to the square root of the number of flywheel stages times the glass ceiling velocity of a single stage - and that the spacing between flywheels would have no effect on this velocity.

498 Nerf has obtained some very interesting results from a two-stage flywheel system with varying spacing between the stages. A video explaining these results, along with links to the chrono results, can be found here.

In summary, he obtained:
  • 140 fps with the flywheel stages jammed as close as possible together
  • 155 fps with the flywheel stages moved a bit further apart
  • 165 fps with the flywheel stages spaced such that a dart enters one just as it leaves the other
All of these results were obtained with the same motors and voltage.

This last result is pretty close to what we should expect based on my model -  but the variation in velocity with flywheel spacing demands explanation. I can say that the explanation that 498 proposes is either incorrect or incomplete. While increasing the spacing between flywheels will result in the dart spending a greater total time in contact with at least one stage, it will also decrease the time that the dart spends in contact with both stages - and, mathematically, these effects should cancel.

Kysan 16180 motors running on 4S have a no-load speed of 22,200 RPM, and rhinos running on the same voltage have a no-load speed of 44,400 RPM, if we neglect energy lost due to air resistance on the flywheels assume a nominal voltage for the battery. These are greater by a comfortable margin than my calculated lower bounds on the critical RPM for each flywheel stage of 20,200 and 28,500 RPM for the first and second stage respectively. So, the numbers check out - it looks like 498's multi-stage flywheel system is supercritical, or at least pretty close.

However, the first flywheel stage has a free-running RPM that is less than the second-stage critical RPM - and I think that this is what explains the drop in velocity when the flywheels are spaced closely together. When the flywheels are spaced close together, the dart is accelerated by the second stage while it is still in contact with the first stage - and it is accelerated beyond the flywheel surface speed of the first stage. This results in the dart dragging the flywheels forwards instead of the flywheels dragging the dart forwards - hence the drop in velocity.

So: while these results may at first glance appear to contradict my model, they actually support it on closer examination. Given that the velocity attainable with a single flywheel stage is already pretty close to the maximum velocity that people outside of NIC wars usually want, this is largely just a matter of curiosity - but it's still nice to finally see some experimental verification.

Thursday, April 7, 2016

808 Camera Setup, Mods And Trouble

First off, a bit more information on my 808 camera.

Here is where I got it: http://www.ebay.com/itm/262162917085

After some research, I think I can conclude quite definitely that what I have is not even a proper 808 type 18 V2 camera, it is a clone of some variety.

My camera does not have the same PCB layout as the known 18 cameras. The battery did not have a connector from the factory. It ignores the s1config.bin file which HETAI (the manufacturer of the real 18) describes in their documentation, and if its firmware even HAS the usual configuration options, I do not know what the filename or format are to use them. It reads the date/time and the timestamp on/off switch from a "time.TXT" file which is described in the user manual included. This is not an 18 camera feature, and is more common among older types of 808.

Nor does my camera pay any attention to the FWDVCH.bin file for firmware reflashing (I tried in an effort to resolve my bugs). Probably a good thing, because I don't know what the hell this hardware actually is, and it might not be compatible with 18 camera firmware.

The files this produces are 1920x1080, not 1280x720 as the real 18 should generate. These are almost certainly scaled from something (960x540? 1280x720?), I am just not sure what yet. The filenames are PICTnnnn.AVI which is once again unknown among the 18 cameras (should be PTDCnnnn.AVI or DCAMnnnn.AVI if I recall correctly).

The camera does not take still images if the shutter button is pressed either on standby or during recording. Another redflag.


Shortly after receiving this I discovered a number of issues:
  • Occasionally, the camera starts itself back up repeatedly after being powered down manually or automatically.
  • The camera often will not power back up after shutting down once. The battery must be disconnected or the reset switch pressed.
  • Huge audio and video noise when battery voltage goes to around 3.6V
  • File corruption.
I want to expand on the last: The camera splits files at 10 minutes like most 808 cameras do. However, on this unit, when the first file gets near 10 minutes, it seems to reliably have missing bits and audio sync problems. Furthermore these AVI files are structurally screwed up in some way and I am unsure about my success editing them with my present tools.

I tried to dashcam my drive to work several times and the files (all <10min after startup) were mangled.

The upshot was that successive files, including one that ran the full 10 minutes and overflowed into another, appear to be OK - so I should be able to limp this along by throwing away 10 minutes of dummy video at the start.

Research is ongoing and I hope I eventually end up with a fully working and configurable firmware in this thing.


The battery was an issue that needed addressing, of course. The little stock lipo was going to die quickly even if it worked. It also didn't seem to be in that great of health and wasn't holding a charge, who would have figured for a no-brand Chinese battery. So I did what I do best: Put a pack on it.

I had 2 of these Panasonic NCR18650B (3400mAh NCA) which have had their positive terminals smashed in from the defective contact design of Convoy flashlights (fixed in my light and my father's light by a mod). I didn't trust these to make reliable contact in the lights anymore and they were gathering dust so I welded tabs on one, wired and terminated with a Deans connector, and bam I have a mega ultra super high capacity battery for the 808, at a whopping 850% improvement over stock capacity. The camera itself lost its lipo and protection circuit* and gained a cable and a male Deans.

(* I didn't trust the protection circuit not to cause trouble, and the camera shuts down well ahead of the 2.5V cutoff voltage of the NCR cell, not to mention even the biggest supported card would fill up well before the battery was flat. So far I have run it about an hour equating to 8.5GB of files and the battery is only down to 4.06V.)

The way I run this (battery not quite properly secured in the hasty image):

It works out very well.

Stand by while I try to get some test footage of me driving up on youtube.

Edit: Test footage is up http://www.youtube.com/watch?v=fwESPiuBnk0

Edit 04-08-16: I seem to have discovered that this camera has, of all things, overtemp shutdown. Twice I tried to record dashcam videos with it today, and both times it cut out within a few minutes. I guess it didn't like being in a black plastic case attached to a black dashboard in the Florida sun. For how many things are missing or broken with this cam, that is a weird feature to have there and working. Cool?

As of right now it is recording continuously sitting indoors and will be doing so until the card is full, hopefully that is in fact what happened, and it didn't just randomly stop.

Also, a hunch that only the first file is corrupted no matter how LONG the first file is; so perhaps booting up and recording a 5 second dummy clip before filming anything will stop the initial wrecked AVI.


One, do not buy this camera. Do NOT buy this camera. Just don't. Feel free to buy an 808, but do yourself a favor and buy a genuine type 16 D-lens at around $40 - or even a genuine 18V2 from HETAI's ebay. This one I bought is a shitty clone and I regret buying it and am still concerned over whether I will be able to limp it along and get game footage out of it or if it will just fail miserably. Oh, and consider a Mobius rather than an 808, they are much more of a "real" piece of equipment. As soon as I can I will probably buy either a 16 or a Mobius.

Two, the hat mount works, and so does the battery.

Edit 04-15-16: A major update.

The planned combat test was a miserable failure and every single file generated of the entire TBNC woods game was junk. It's a shame too, although the game was a bit dysfunctional, some good moments and some chatting with players happened that would have made for a good first video.

It seems my hypothesis of first file corruption was false, something more entropic and devilish is at play here.

However I may have stumbled upon the answers from an unexpected direction, in the process of going through motions ruling out easy causes my attention turned to the flash card. A bit of digging turns up a lot about junk flash and junk SD cards that are frauds or don't meet specs. Great, I bought a cheapo "Infinitive" brand card, cheapskate I am.

So how do I verify SD card operation and performance? While researching that, I come across something from the SD group itself about specific low level formatting to ensure performance. Hmm, well when I started having power management issues, I promptly used newfs_msdos on my SD card for the same reasons, eliminate something wrong with the filesystem or fragmenting or whatever as a possible cause. That of course didn't achieve anything, but I didn't think anything of it at the time, because FAT is FAT is FAT, right? I reformatted right before the game and that was the worst it had ever been.

And now that I think of it, reformatting may have started my trouble with munched AVIs and missing data.

Now I have formatted my card with the "official" SDFormatter utility, and went through a few tests mounted on the dash of the suzuki. The files weren't mangled. All of them played, none of them was frame drop central, none of them had unsync'd audio and they obviously weren't (file length versus video runtime) missing huge data like before.

I am also keeping note of the battery voltage being near 3.8V at the time of this observation, in case I have a voltage related issue.

Fingers crossed that I managed to get a gremlin by the tail this time, because damn, the little camera works well when it works. I like it, I like it a lot. Even did some night driving with it and the footage wasn't a black abyss like some dashcam videos.

Sunday, April 3, 2016

808 Camera and Preliminary Rig Plans

I have been looking to film gameplay for years. The trouble is, I am not going to spend $300 on a GoPro. That's a used transmission for my Suzuki, or a high-end superstock gun like a Tacmod, or a HPA rig - I am not spending that on a camera.

What I wanted was something as small and cheap as possible with a wide angle lens and acceptable resolution. Bonus points for no head straps.

I came across these 808 keychain cameras from the RC community and finally just bought one:

$29.12 shipped on ebay. This seems to be a type 18 with a wide angle lens assembly, a version I have not seen documented. It also doesn't use the same configuration file as the 18 camera people have seen. Still trying to figure that out so I can get some better settings.

You get the camera, a manual in Chinese and broken English, and the nonstandard USB cable. You must supply your own microSD card.

This thing is literally the size of a car remote lock keyfob and just as light.

With velcro:

And here's where this is going:

Tested and works great, not noticeable, doesn't make my hat fall off, not in my vision, perfectly aimed. No head straps, no mounts, no turning around my hat like basicnerf for a gopro.

The big issue with 808 cameras is that they are majorly janky. They can do the job, but the hardware is cheap, poorly assembled and usually includes low quality no-brand parts. The firmware can be buggy and half-baked. You can't expect the reliability of a GoPro.

I did already encounter some strange behavior (continually turning itself back on whenever a card was inserted) and lockups that seem to have self-resolved by simply letting it run and shut down automatically on its own, resulting in continued normal function. You have to get to know your 808 model and its quirks and how to dodge them.

When I had this open for inspection

Battery is a 400mAh lipo cell, that will need to be addressed before NvZ. In the meantime I may just strap my Miller single 18650 powerbank/charger to the back of my hat with a USB cable and a NCR18650B cell, if it works I will just keep the little lipo in there.

The video from this is decent. A bit noisy and artifactey as is the audio, but the lens is not bad at all, and it is 1280x720. Footage and more technical matters in the next post, and this setup should get field time and a youtube post next Saturday at TBNC.

Saturday, April 2, 2016

Why spin-stabilized darts whirlybird so easily

Spin stabilization is one of the ways that the accuracy of Nerf darts can be improved. A spinning dart that would otherwise curve in flight - which happens due to damage or imperfect manufacturing tolerances - will instead travel in a corkscrew. The curvature of the dart's flight path is averaged out, and the overall path of the dart is a straight line.

Dr Snikkas' flywheel cages are a well-known way to put spin on a dart while firing it, and they do seem to improve the accuracy of people's blasters tremendously. The draugr team has been working on developing a mass-manufacturable flywheel cage that does the same, and, we've discovered something odd: spin stabilized darts whirlybird more. (A whirlybird is a complete destabilization of a dart characterized by the dart spinning rapidly like a pinwheel. A whirlybird can turn a shot that should have gone 100 feet into one that lands at your feet.) Sometimes a lot more: one of the test cages causes koosh darts to whirlybird almost all of the time.

Here are my (largely speculative) thoughts on why.

Edit: There was a mistake in my math in the first version of this post - this is what I get for working in a hurry and not double-checking.  It's fixed now.

Saturday, March 12, 2016

Blaster modifications and safety in the context of HvZ

This document is intended as a reference for anyone who needs to decide what modifications to Nerf blasters (and similar toys from other brands) to permit in their game, with a focus on games of HvZ played on campuses. The purpose of this guide is to give people the knowledge that they need to make safe decisions without being overly restrictive. It was originally supposed to be short and concise, but it grew over time into, well, this. Safety is important, so I think it's worth taking the time to read. This may be of use to both moderators, who make the details of and implement a game's rules, and campus officials, who have the final say on what is permissible.

I've added pictures in an attempt to make this a little less wall-of-text-ish and to break up the sections; these images are from Steph Smith's pictures from the University of Waterloo's first invitational, this imgur album, Oklahoma State University HvZ Facebook page, more from the same facebook page, and toyland.gizmodo.com. All of the images you see here have been edited (trimmed and resized) by myself.

EDIT: Almost immediately after publishing this  post, a conversation started on reddit regarding the use and safety of Chinese LiCo batteries such as Trustfires - which has been a matter of some controversy over the years in the Nerf and other hobby electronics communities. I may have been overly generous in my assessment of the safety of these batteries, so I've edited the post to correct this.

Wednesday, September 16, 2015

I'm not mad, Hasbro . . .

. . . but I am disappointed.

This Zeus suddenly gave up the ghost when I was testing it last weekend, and this was the cause: a poorly-made solder join on the wire leading directly from the batteries to the motors had come loose.

The lemon lotto is beginning to feel a lot more like lemon Russian roulette; loose wires and misaligned parts are starting to feel almost routine. Poor QC is a minor annoyance to people with screwdrivers and soldering irons, but to the average consumer, this would have been a killer problem - especially if this had come loose during a game.

I've heard of other nerfers having similar problems with their Zeuses. This is no good. Somebody needs to fix their shit and fix it yesterday.

Testing has resumed as of last weekend, with no further problems.

Sunday, August 30, 2015

Nerf Rival Zeus - Lightning Link, RS390-4735 Swap, Stock Motor Info

Last time I posted about my Zeus, it was still semi-auto. Shortly after, I decided to change that, because I am strongly dissatisfied with the stock trigger's heavy pull and unreliability at higher ROF. IMO, something else needs to be done or developed aside from the standard Zeus if you want to use Rival automatics as a general-purpose (semi-auto or up to 15rps full auto with precise controllability, in my book) primary.

So my Zeus is now converted to uncontrolled feed. While it isn't the most practical with 25+ rps on a 12 round mag and awkward reload, the trigger is nice, and it is awesome.

There are 4 changes to make in order to get this functionality:

* Remove the ram lever and its torsion spring.

* Remove the rear gate and its shaft and torsion spring.

* Grind out the detent on the right feed housing half. Visible at front inside the feed path

* Grind out the detent on the front gate (the thin area above the semicircular curve). You want this gate to match the feed path seamlessly when fully open.

After doing so you will have screaming fast full auto - take a loaded mag, open the detent by hand, see the balls shoot out? That fast, except going downrange at a hundred odd fps. It's a great special weapon. Unfortunately, I can't think up a good selective fire or 2-stage trigger strategy using the stock parts.

Motor Upgrades

The search for good Zeus motors has been ongoing, and thanks to /u/farmcoffee on Reddit (member of the Draugr team) I received a free pair of this 0.47mm/35 turn 390 motor which was my first stab at it.

Specs on this are sparse as with most Chinese motors, but what is specified is 21000RPM@11.1V giving a kv of 1892 - fairly low for a 35 turn wind, but such is the expectation for a long armature with this sort of aspect ratio like the 390 "stretch" motor. You can also see this with 130 and 180 motors and their turn count versus kv.

I did encounter a snag. I was sent two motors obviously of different batches. One had stronger magnets and different color leads, and definitely revved slower as is expected from the magnets. Not exactly promising for prospective buyers of these for Zeus installs. These motors, however, have external flux rings - a steel sleeve on the outside of the can, to provide an additional magnetic path. These are removable and optional, and removing them is equivalent to weakening the magnets - adding speed, reducing stall torque slightly, and reshaping the torque curve as expected from these changes; so I ended up removing the ring from the slower motor, cutting it in half and putting it back on and bam, perfect speed match. Even with the flywheel load and the imbalance of the stock Zeus flies, they match about as well as any .50 cal gun ever would - Not shabby at all.

Stock Motors

This is also the first time I (or anyone?) has pulled the stock motors from a Zeus:

Once again confirming 360. Appears to be a Johnson clone. I don't think Hasbro ever uses genuine motors, it's all Chinese generics except those SMCs in the barricade. Also we have 24000rpm@9.6V printed on the can, and this gives a kv of 2500.

The 3160 wind is rather weird to me because it seems to be deliberately suboptimal copper fill. Note that a common AEG motor (Stampede, Swarmfire, Vulcan) is a Mabuchi clone RS360PH-3560 meaning the standard 300 series armature stack can take at least 0.35mm wire at 60 turns. In any case it is unfortunate that this motor is wound this way, although it works fine it could have had more guts with 0.35mm wire. Was this something to do with current and the C cells perhaps?

The shaft is 2.3mm (of course), 8mm protrusion from the bearing and a total stickout of 11mm from the mounting surface. It has the typical rolled splines for extra grip that a lot of 300 series shafts have. Doesn't seem that critical, the flywheels install super tight. This however is a shorter shaft than I expected. That is good, makes finding suitable motors easier as virtually ALL of the 300 series motors in existence will mount this flywheel properly.

Mod wise on the gun:

* The Zeus has rubber sleeve style mounts. Those familar with Stampede gearboxes will remember them. I had to trim about 1/4" off the top edge of mine to clear the flux rings on the 390s which needed to stay since I matched my motors by modding them.

* The stock hold-down brackets are used with longer screws. Be careful not to overtorque and break/bend the bracket since it doesn't seat against anything now. FYI, mounting the motors with screws into the can is NOT possible with the stock flywheels because the flywheel web runs SUPER close to the mount socket surface. Unless you countersunk the screw perfectly (which might make it weak) you need to clamp your motors into the socket from the outside. Similarly, you need either the stock rubber or a shim between the can and the bottom of the mount socket. The bearing snout hole in the socket will align the motors without the rubber, but the bearing snout will stick out too far into the inside of the cage and hit the flywheel.

* Normal clearance hole in the left shell.

* Shafts zipped to length after installation. Necessary to clear some stuff, BTW.

As an update, here is what I have done endbell cover wise:

And a little fix for the nasty sharp edge underneath as well. No paint yet.

Some other stuff:

* Flywheel installation depth is with the vertex of the V-grooved flywheel surface set just below the edge of the cage.

* You can probably remove these flywheels with a proper puller, but the easiest method for most is to suspend the cage with the motor hanging free and the flywheel sitting against the mount socket, and drive the motor shaft through with a punch smaller than 2.3mm (I used an old 130 armature).

* I found some evidence of contact of the flywheels with the cage: OD of mount socket (due to mold flash inside the fly that I removed) and face of mount socket due to install depth. This was all factory. If something seems to have friction or make a funny noise in a zeus, investigate it, there is very little clearance in these things and rubbing flywheels is a possibility.

* Pinion removal on larger motors (if you receive or scavenge a motor with a pinion on it) - use proper puller or lock pinion in vise and drive shaft through with <2.3mm punch. Don't pry against the can. You can do that with little motor stuff, not these.


As I expected, these motors wanted 4S, so I am using the same 4 cell pack I was thrashing my stock motors on. By the numbers that is 28000RPM unloaded - compare to stock motors on 3S at 27750RPM unloaded (and smaller in comparison to the static load). Chrono data incoming but it shoots nominally.

Chrono session:

Units of feet per second. Mostly dead battery!

Handling of high ROF is definitely improved, I haven't seen a visible shootdown problem yet. It definitely doesn't get droopy and inaccurate on the end of a mag dump like the stocks did.

Response is improved as well.

Speed match is improved substantially.

Stall torque is now sufficient to not be jammable by feeding a ball into stopped flywheels. The 390 motors have enough grunt to force through even the densest Rival ball from a standstill, and if you are familiar with how much crush the Zeus cage has and how damn hard it is to manually push the balls through the flywheels that is seriously impressive. The brushes aren't even broken in yet and the battery is half dead! The stock 360s didn't have a chance of recovering from that.

It is nice to be able to pin numbers on things for sure now that we have stock motor wind and kv data. Aim for 28000+ rpm and as much torque as possible.

I think next I have to explore the RS380SH-4535 and -4045 and similar winds. It is a much more common motor, and genuine Mabuchis are readily available (a good thing, so you don't end up like me hacking around with flux rings or getting lemons of sketchy Chinese motors); and also a bit shorter than the 390, simplifying the mount and cover mods.

In the end though, I think the stock motors are absolutely fine. If you are only shooting semi-auto, there is not one reason to replace them. Just wire properly and run 3S and you are good to go. Couldn't be easier to understand, and it's a nice change from the little fiddly 130s and shitty metal brushes that you have to confront in a stock .50 cal flywheeler.

Thursday, August 6, 2015

PSA - Do Not Buy - Nichibo FK-180SH-3240 = Scam! Metal Brush Junk!

I received a few comments from someone who decided to test out these Nichibo -3240 motors that Zinky86 on ebay was "able to get in" (http://www.ebay.com/itm/121624679840)...

Well, that's conclusive. 2 separate reports. I have not received that set from meishel to test but no need now.

I don't know what it is about the FK180SH-3240 that makes it so attractive for lowballers to slam metal brushes in! Hell, even the China clone variety FK motors have proper carbon brushes, and seriously, if you look at a 3240 armature and think "That will work with metal brushes for more than 5 minutes" you're an idiot, there is NO way that can have a legitimate purpose.

What's more is that the designation "FK" is a LIE. "K" specifies carbon brushes. It's very unambiguous, go look at the Mabuchi website. To put "FK" on a metal brush motor is misrepresenting the product. Same with Kysan Electronics - the Draugr team checked already and until we asked specifically they had the damn thing labeled as an FK with not a peep about metal brushes, and the specs were ripped from Mabuchi's datasheet on the real motor.

This is what Zinky86 had to say about the Nichibo -3240 motor:
This does not reflect positively on Zinky86, nor Nichibo, at all. I am going to give Zinky the benefit of the doubt and assume he was sold this motor believing it to be a clone from a reliable and experienced manufacturer, but I am still disappointed that the problem was not caught until members of our hobby bought fraudulent product.

And Nichibo, what the fuck?