LCT AK74 NV Disassembly and Overall Review: Gearbox Disassembly

Then,Following the previous teardown review,This time, we'll be disassembling the gearbox.

Disassembling the gearbox

First, as a recap from last time, we were able to remove the gearbox.

First, remove the selector gear assembly shown in the photo above (it's already detached in the photo). It's just resting there, so it's probably already detached.

Next, remove the motor holder. There are two Phillips head bolts on the motor mounting point of the gearbox, so remove them. Note that they are tightly secured with threadlocker.

I'd like to examine each part in detail, but I'll put that off for now and proceed with the disassembly.

Next, remove the gearbox opening prevention and harness clamp located on the top of the gearbox. This was also very stiff, so I used a flathead screwdriver like a chisel and tapped it off with a plastic hammer.

This photo shows the unit already disassembled, but originally the button that holds the top cover in place is sandwiched between the gearbox.

It is in its removed state.

　

Next, remove the selector switch that runs through the gearbox from side to side. This is also tightly secured with threadlocker, so don't hesitate to turn it with a tool.

Next, remove the often-forgotten plastic cap. It's just snapped in place, so it pops right off. It's probably there to prevent dust from getting in.

The gearbox should open once you remove the four hex bolts holding it in place, but I had a lot of trouble opening it. I couldn't open it by hand at all.

I resigned myself to the possibility of damaging it and pried open the seam on the top of the gearbox by inserting a thin flathead screwdriver. Even then, it was quite a struggle.

The culprit behind this gearbox not opening problem appears to be that each gear has three bearings pressed into it on both sides.

Therefore, even if the gearbox is opened, the gears cannot be removed.

This time, I removed each gear by tapping it with a punch, bracing myself for the possibility of damaging the bearings. Fortunately, the bearings didn't break.

The remaining parts can be removed normally.

That completes the disassembly. By the way, unfortunately, the gearbox's spring guide was not a QD type.

A look at the components of the gearbox

Before getting to the individual parts, I wanted to mention the condition of the grease and shim adjustments right out of the box. I had high expectations, but to me, it was a bit disappointing.

While the gears are properly greased in sufficient quantities, the amount of silicone-based grease applied to parts like the nozzle and tappets is somewhat insufficient.

The shims aren't bad, but I adjust them so that the meshing width of each gear is maximized, but the spur and sector gears were misaligned. Needs correction.

The parts I'll be showing from here on are still in their assembled state, disassembled and not cleaned or otherwise treated.

Gearbox casing

The gearbox was made of cast aluminum. It was quite clean with no burrs or anything, which left a good impression. Also, the bearings are large 9mm ones, so durability is excellent. The bearings are properly press-fitted.

Also, the cutoff lever was plated for some reason. Probably zinc plated (zinc plating is usually for rust prevention). I wonder if it makes it smoother?

The other side was also clean and free of burrs.

Unfortunately, no measures were taken to prevent cracking at the four corners of the window. I'll have to sand them down myself.

By the way, the precision of the gearbox fit is perfect. That's amazing.

Motor area

Next, let's look at the motor. It's a plain, all-black motor. It might have some torque, but the rotation speed is too slow, making it difficult to use with 7.4V power. It needs to be replaced.

The pinion gear assembly. It's a D-type with a set screw to prevent it from coming loose on the shaft. I generally don't like D-type gears because the shaft strength decreases and play develops over time, so I'm going to replace it. Also, looking at the contact surface of the pinion, not all of the teeth of the pinion are meshing with the bevel gear, so there is room for improvement.

Next, let's look at the intake and exhaust system.

Cylinder, cylinder head

First, the cylinder and cylinder head. They were a single piece. The cylinder head is machined, and the cylinder is stainless steel? with cooling grooves. This is impressive, but since I adjust the AOE at the cylinder head, the single piece design is a bit of a problem for me. But still, it's a good product.

The underside of the cylinder head did have rubber on it. By the way, the piston head is also metal, which seems like it will make noise, so I'll have to think of something to fix that.

Tips

It's quite short, but the shape of the tip and the sealing nozzle (there's only one rubber piece) mean there isn't much resistance when using it, which is good.

Piston, piston head

The piston and piston head are stuck together and I can't remove them. The piston head is a 5-hole rear-exhaust type and is made of aluminum.

The piston is made of ABS resin with metal gears glued to it. The second-to-last gear has about half its teeth shaved down to prevent piston cracking, but it's not enough. It will probably need further shaving. The material is much better than the easily cracked polycarbonate.

Incidentally, when combined with the cylinder, the airtight seal was solid, so there were no problems, but the piston is quite heavy at 31g.

I usually use around 25g. Using the genuine product might cause problems if you don't think carefully about it.

Next, let's look at the drivetrain.

Sector gear

First, let's look at the sector gear. It's an iron sector chip. I don't really like this because it attacks the tappet. The gear itself seems to have good machining precision. The deburring of the gear end faces is excellent, but the gear shaft and bearing are press-fitted, making adjustment impossible, which makes it difficult for people who want to customize it.

Unfortunately, the shim adjustment wasn't done properly, causing it to rub against the adjacent gear. (You can see the marks in the third photo.)

Spur gear

Like the sector gear, the build quality is good, but isn't the width a bit too thin? The shaft is also press-fitted with bearings and cannot be adjusted.

Bevel gear

The build quality is generally good, but four anti-reverse latches seem insufficient. It's fine at the current cycle rate, but it becomes unreliable if the cycle rate is increased even slightly. Of course, these are also press-fitted, and in fact, they're the tightest press-fit I've ever seen.

Anti-reverse latch

This is an anti-reverse latch. I've never had any problems with it, so as long as it's sturdy, that's fine with me.

Tappet plate

The tappet appears to be made of a nylon-based resin, which seems to provide good strength and precision.

I don't really like the shape of the wings. I wish there was a curve at the base of the wings. Well, I'll probably just sand it down anyway.

The nozzle insertion point appears to have decent perpendicularity and also seems to be quite strong.

This is a tappet return spring. It has many coils and is quite strong, so I think it will provide good tappet responsiveness.

Next is the electrical system.

switch

It's a Switch, but it's just average. There's nothing particularly special about it.

The harness uses thin 0.75 sq wire, so it's definitely going to need to be rewired.

The remaining part is the trigger mechanism, but it's not particularly noteworthy, so I'll omit it.

Finally, we have the main spring and spring guide.

ス プ リ ン グ

The pins are evenly spaced, of a reasonable length, and have well-finished ends, suggesting there are dedicated parts for the 1J specification. There was no spring noise either.

Next is the spring guide. It has a thrust bearing and long lugs, which should make assembly easier. I wish it were a QD (Quick Detach) type.

That concludes the introduction of all the parts.

Overall assessment and direction for customization

In terms of exterior design, I think it's a product that will satisfy most people, except for hardcore enthusiasts. Every single part is truly made of iron or wood. It's a bit heavy (around 3.5kg), but the balance isn't too bad, and the romance and love for it more than make up for it.

However, the grip is terrible. A nicer one is available as an official option, so buying that might be a good idea.

In terms of performance, if you overlook the slow rate of fire, I think it performs reasonably well right out of the box. The initial velocity is 93-94 m/s with 0.2g BBs, and the hop-up design isn't bad, so the trajectory seems quite good.

The gearbox is basically filled with high-quality and premium components.

However, the slow cycle rate and weak spring, combined with the metal-toothed piston, create a mismatch between the parts selection and the out-of-the-box performance.

Another drawback is that all the gears are press-fitted into bearings. It makes maintenance a hassle. I understand that press-fitting the shaft into bearings has advantages in terms of noise, shaft runout, and resistance to impact, but in my experience, a minimum clearance of 0 with an H8 fit tolerance is sufficient.

I've mentioned a few points of concern within the gearbox, but from a durability standpoint, with that cycle rate under 1J or less, it's basically unlikely to break and seems quite robust.

Regarding the direction of the customization, I will use as many usable parts as possible, as usual, but the fact that I can't use the crucial gears is a real pain.

While I'm at it, I'll change the gear ratio to 16:1 to improve responsiveness, and since the air volume is large, I plan to increase the airflow velocity.

The next section will cover customization.I've ordered the parts, so I'll upload pictures once they arrive and I've assembled it.

LCT LCK74 AK74 NV AEG
I think this is one of the best electric, wooden-stocked AK74s I've ever seen.