Nerf Rival Zeus R&D Begins - Stage 1 Upgrades

It's finally here!

Box contents.

This is the stock battery tray. Extra spring terminals in the middle of the stick for extra resistance!

Battery tray removal. You will run into these triangular drive screws securing the buttplate/battery box cover to the battery tray. Same as Stampede buttplate/battery tray assemblies, the uncommon drive is used to stop people from absentmindedly unscrewing the wrong screws trying to open the battery box.

If you do not have the proper driver for these, which I do not in this location, try household scissors. The blade tip is likely to engage the screw well enough to back it out with minimum hassle. Don't use a good pair of scissors for this, of course.

Then put your cover back together with standard screws.

Zeus vs. Tacmod 3.1

Not a small gun. Quite a chunky thing this is.

Eotech test:

See how small the 552 is in comparison to the Zeus?

The rail length works, but unfortunately, these rails (which are very sloppily made Hasbro rail that LOOKS like Picatinny) suck, and my sight has an unsettling list to it when tightened up, along with thin-plasticky flex:

That's a big nope, looks like this thing is getting picatinnied in the future. Time to order some Magpul rail sections.

Here's a weird observation:

"Rating:

...Wait, what?

9.6V?????

Speculation time: Alkaline tray is an afterthought? Nerf has rechargeable plans? 9.6 is such a specific voltage. Why?

Mag release. Spring seat is an integral part. Quick observation with this, it is reversible in the receiver. If you are having trouble releasing mags from your chosen side, try flipping this over with the spring seat arm facing the other way.

Plenty of room in this battery box after de-traying. Also, plenty more room is available if the webbing is gutted out. Betcha you could fit a double stick sub-C pack or a regular "brick" shaped lipo in there with some careful grinding. You may have to rethink the cover anchor nuts though.

Top rail is a separate part integral with the rear sight base. It is clamshell but doesn't need to be. This will be taken advantage of when installing picatinny, since I see zero reason to ever open or paint this thing later on I will likely just weld it together with a plate on top for bolting the rail.

Same old crap wire, this is the same 22AWG? or so stuff used in the nerf AEGs

The masking tape is a nice touch.

Boo.

Hiss.

PTC on that little board at left

Flywheel cage removed. The breech/feed assembly is integral. It also isn't a closed cage. This side is open through the jam port on the side. Very cool.

Flywheel comparison to RS fly. Do you get a sense of scale NOW? These flywheels are huge. No wonder they have 300 series motors on them! They are made of ABS. Balance issues are notable here. Noise and vibration are high.

Lock removal: Orange plate on the right (jam door) side of the breech assembly. It's a real Rube Goldberg mess in there - mag and jam door interlocks all interlocked! You can't rev or pull the trigger without a mag loaded and the jam door closed.

All of it can go. The plate, all the plastics, one spring, the switch, and the screw. All the gate linkage that is actually important is on the other side, the one with the motor endbells that faces out when installed.

None of this hardware latches the jam door! That is done by the rails it runs on and its associated mounting hardware in the receiver. Removing this stuff will not make it loose or change the feel at all.

Dart experiment.

Breech. You can see the raised detent at the right. You may have seen the uncontrolled feed full auto mod, and that this detent needs to be removed. This is the prime reason why that modification is not something to do lightly. The detent's function will be explained shortly.

This is at rest. The orange gate you can see closed is the front gate. There is a second gate at the rear, one round length away from the front gate.

With one ball in the breech.

Pulling the trigger. The rear gate pops out and blocks off the mag, preventing further rounds from feeding. At the same time, the front gate retracts.

This does not fire the ball, however. The ball remains held in the breech by the detent.

What gets the ball past the detent is the orange part seen at the bottom of the chamber, which will be called the ram. It is a lever that pivots about a horizontal axis.

Continuing to pull the trigger, the front cam pin on the trigger engages the ram and causes it to flip up and force the ball past the detent, where it is seized by the flywheels.

Zip!

Now here is the hopup system.

This needs to be targeted for additional testing (starting with temporary removal of the inner barrel to establish unhopped ballistics). Whether the hopups on Rival guns (commercial or DIY) are modified, adjusted, replaced, or worried over like airsoft ones to increase the consistency of the backspin and thus accuracy, are is all down to the ability of the ammo to support accuracy.
Polyurethane foam balls, a sketchy proposition in some ways.

Rev switch is a dual contact type, familiar to Stampede and Nitron users. In some ways the grip is Nitronnish as well. Typical trigger interlock here.

Trigger; front cam pin is for the ram lever, the top ramp is for operating the gates.

Microswitch mockup.

Cleaned up motor terminals. I never got a picture of it, but there are axial lead inductors, those 2 PCBs shown, and ceramic disc caps stock.

Motor clamps are plastic and are bolted down hard. They clamp the motor into what seems like a rubber lined mount, as in Stampede gearboxes. The motor can does not press fit into the cage. There is also no glue, unless some hotglue was spilled from the electrical component and solder joint reinforcing/supporting use of this stretchy hot melt goop all over the inside of these things.

Grip gutting for switch.

14AWG teflon, note green is negative, but I turned my motors around from stock to get positve on front. I find it best to send the flywheel leads upward, you want to keep wire well away from the trigger area.

While on the subject of motors - the zeus motor is a 360, confirmed to be a 3 pole motor. I have not pulled the flies or removed the motors yet and still no idea on winding data or kv. It isn't a standard metal endbell Mabuchi or a Mabuchi clone; it is nylon endbell, and may be a Johnson. It does have a bronze sleeve bearing in the endbell so shouldn't have any problems with that.

Minor wire clearance

And that's all folks!

Shoots like a beast on 2S.

While I was at it, I grabbed this top rail length (6") for proper Picatinny replacements.

Yes, I know - What about X? Where's the data? It's coming. Hold on.

Update 08-04

Preliminary chrono shots:

7.4V: 91.72, 100.3, 96.74, 94.02, 93.21, 100.3

11.1V: 115.5, 105.4, 110.3, 105.3, 107.7, 105.7

14.8V: 108, 106.9, 110

Feet per second. New ammo. Sample size is crap because I have only 12 rounds and I don't want wear affecting the data.

As you can see, 3S definitely gained something over 2S, but there is certainly some dynamic-friction action going on in the 110-115 fps band, 4S only added noise and ammo wear (observed as an increase in foam "sparks" coming out the muzzle). I would say 2S is right on the edge of criticality, probably right in the knuckle of the curve where it transitions from static friction to dynamic friction and starts approaching the ~110 fps asymptote. For that matter, the stock alkalames are probably near there as well, only much saggier and more gutless. The 2S pack (I am using my new 25R Sammy stick) makes it a lot more shootable and responsive than the stock reviewers are reporting.

The location of the criticality barrier of this system so close to stock suggests they engineered and optimized the hell out of it, in terms of shooting harder at least. Doesn't mean 15-20 fps and speed headroom is not a major, major upgrade.

This is all tested with the hop-up installed.

Next step is to work out power systems that will give more torque with similar speed to 3S with stock motors, since that seems to be right about what it wants. I suspect this will end up as a matter of matching the kv of the stock motors 1:1, as 3S batteries seem like the way forward.

3S is about the maximum voltage you would want to deal with (pack size and cost wise), and compared to 2S, higher voltage is always better if it is possible - with a higher turn count motor you get better copper fill, more torque, and more efficiency, and deliver the same power with less current, thus less brush wear and less losses over stray resistances and battery sag. Also, 3S is a convenient way to do things for the NIC because the battery requirement would not change between stock motor "stage 1" builds and aftermarket motor "stage 2" builds. Get a good pack and you are futureproofed.

Speaking of motors, the stock ones are not half bad. On 3S the response is there. For semi-auto and mechanical full auto at a reasonable rate (not 25rps uncontrolled feed...) they really ought to be good enough for anyone with a 3S battery and rewire, or even 2S.