VFC HK416 CAG AEG High Cycle Custom Preparation

Last time, I did a disassembly review of a shop-customized VFC HK416 CAG AEG.

From now on, I'll be customizing it to my liking.

Actually, quite some time has passed since the last update, but it took a while because we encountered several problems and struggled with the process.

This was my first custom build with an FCU, and the combination of that and bad luck made it quite challenging. I'll write down the lessons I learned from the experience as a memo for myself.

First, I'll introduce the direction of the customization and the parts I initially prepared.

Customization direction and sourced parts

Regarding the direction of customization, reviewing the performance I previously described, with 0.2g BBs and no hop-up, the muzzle velocity was around 92-93 m/s, and with a 7.4V LiPo battery, the rate of fire was less than 16 rounds per second. Also, the gear noise was personally unacceptable to me.

Therefore, we will proceed with the customization in the following direction.

Since we're installing an FCU, the idea is to use electronic control to stabilize the unstable state that would cause the semi-automatic mode to overrun if assembled normally.

We'll use the same concept as the fighter jets that have long been common practice for achieving high maneuverability by deliberately making the aerodynamic balance unstable and then stabilizing it with computer control (similar to the CCV concept). Therefore, we'll proceed with a menu that wouldn't work if it were built with a normal switch.

The target image is an extremely responsive design, a rate of fire exceeding 30 rounds per second, and an initial velocity of 92-93 m/s with 0.2g BBs and no hop-up.

Based on this, the parts to be procured will be as follows:

In addition to these, we will also be using the custom parts that were originally installed.

Incidentally, not all of these parts worked perfectly, so I'll summarize the final specifications at the end of the custom build article.

First, we'll proceed with customizing the gearbox.

Preparing for a custom gearbox

First, we'll do some preliminary work before assembling the gearbox.

We will be polishing the sliding parts of the gearbox components. These are the blue parts in the photo.

We'll polish this using a rotary tool with a buffing wheel.

Using this method makes polishing easy and quick. It will look as clean as in the next picture in about 5 minutes.

Next, we will modify the part shown in the following photo to prevent cracking of the gearbox.

To avoid stress concentration, we'll round this area using a rotary tool.

This modification is applied to both sides of the gearbox.

When I temporarily assembled the gear I plan to use next into the gearbox, I found some interference, so I'll modify it. It's the tappet guide part of the gearbox shown in the photo.

Based on my experience, with VFC gearboxes, aftermarket sector gears often interfere with the ribs on the gearbox shown in the picture.

The processing is now complete, and we will now clean it.

Next, we'll prepare the gears. The gears we'll be using are SuerShooter's high-speed gears, 13:1.

What I like about this manufacturer's gears is that they have bearings, six anti-reverse latches, and the bearings in the tappet-pushing parts act as mini sector chips, which I really appreciate.

Using this gear as is will result in a piston crash 100% of the time, so we will cut the teeth off the sector gear.

Normally, a 2-tooth pull-side and 1-tooth release-side configuration would be the safest bet, but this time, relying on the FCU's control, we'll go with a 1-tooth pull-side and 2-tooth release-side configuration for better response. If this configuration were built with a standard circuit, it would likely result in overruns and double firing in semi-automatic mode.

I'll mark them to avoid making mistakes.

This is then clamped in a vise and processed using a rotary tool with a diamond cutter attached.

I'll introduce the rotary tool and cutter I use.

Dremel High-Speed ​​Rotary 4000
This is my go-to rotary tool that I always use. Having this expands the possibilities of your DIY projects. There are two popular models, the 3000 and the 4000, but I recommend the 4000 because it comes with a set of tools and has more power.

Diamond cutter　
It's inexpensive, so I think it's sufficient (please pay attention to the shank diameter of the rotary tool).

Mini vise　
It's dangerous without this.

Normally, the sector gear screws would be removed before machining, but they were too tight to remove on this product, so I had no choice but to machine it as is.

Once the processing is complete, finish it with a file, clean it, and you're done.

Next, we'll prepare the motor.

Unfortunately, many of LONEX's motor pinions don't work well with bevel gears, so I'll be replacing them. First up is the LONEX A1+ motor I'll be using.

The pinion gear in question

First, we'll remove the pinion using a pinion remover.

Eagle Model's pinion remover

Now, we'll set the motor in place and remove the pinion gear.

An important point to remember here is to remove the pinion gear little by little. Trying to remove it all at once will damage either the pinion gear or the remover.

I'll compare the pinion I removed with the pinion from OPTION No.1 that I plan to replace it with.

It's a bit hard to see, but the design of the gear teeth is completely different.

Normally, gears are machined using a gear shaper, but LONEX gears are smaller and have a deeper machining depth, resulting in larger and deeper tooth surfaces. I believe this larger tooth surface size is the reason for the incompatibility with many bevel gears. To put it in technical terms, the gear cutting tool and the balance of the addendum and dedendum in the machining conditions must be slightly different.

Next, since we'll be using the motor brake frequently, we'll replace the motor brushes. Remove the springs that hold the brushes in place. Be careful not to let them fly away.

You can remove the brush by unscrewing the spring and the screw that holds the brush in place.

Let's compare the removed brush with the silver brush that will be used as a replacement.

Replacing the brushes with silver brushes doesn't significantly change performance, but it greatly improves durability, so it's a good idea to replace them if you're subjecting the motor brake or other heavy-duty applications to this purpose.

Simply reverse the removal process to install it, and you're done.

Next, we'll install the new pinion, but that's where the problem occurs.

Trouble #1

To be honest, I'm too embarrassed to write about this, but I'm writing it down as a warning to myself and to prevent it from happening again.

Embarrassingly, I made a mistake when installing the pinion gear, causing the motor shaft to buckle.

Furthermore, the tools were also damaged.

It's a big shock.

There are several possible causes, including the following factors:

These are some possible contributing factors.

Since it's already broken, I can't say for sure what the cause was, but the force I used to insert the pinion was quite strong, so I should have stopped midway and checked the dimensions instead of forcing it. Also, I couldn't remove the motor tower from the motor after taking out the pinion, so I suspect the motor shaft might have been bent.

Incidentally, to give you an idea of ​​how much force was needed, it was so strong that it couldn't be turned without using a lever, which was abnormal. Normally, it can be pressed in with a little force, so in cases like this, it's best to stop the installation and check it.

Since both the motor and the tools are now unusable, I have to order them again (I was very disappointed).

I ordered it in a hurry from Amazon, and since I was a little hesitant to reuse the pinion gear, I went with the EG Hard Pinion Gear from Laylax. As expected from Amazon, the package arrived in just one day, and I was able to resume work.

First, remove the pinion gear and replace the brushes in the same way.

Let's compare the pinions.

The size of the tooth surface is completely different.

Before pressing in the pinion, we measure each dimension and carefully press it in.

Turn the handle carefully, paying attention to the press-fitting load. This time, it turns with a little force.

The press-fitting was successful.

By the way, I chose the pinion remover from Eagle Models, the same company that makes the tool. This product seems to have relatively high rigidity.

Eagle Model Pinion Remover
There are similar products that are cheaper, but this one seems to have the highest rigidity.

Just to be sure, I'll compare the overall length of the turntable to that of the original part.

The total length of the assembled motor

A Ronex motor with a reassembled pinion.

The numbers are almost the same, so it should be fine. A difference of about 0.11mm can easily be covered by adjusting the motor's position.

The biggest lesson learned so far is that "the workThe most dangerous time is when you become complacent."That's the point."

To be honest, I've replaced the pinions of many motors before without any problems, so I've been doing it in a very routine, assembly-line fashion without checking anything.

However, I learned the hard way that having that kind of mindset will eventually lead to trouble.

It's probably rare, but everyone should be careful even with familiar tasks.

We'll end this discussion here, focusing on this lesson learned.

Next time, we'll finally start assembling the gearbox. Please join me if you're interested.

Actually, the emotional damage I suffered at this stage led to a series of further problems. I was quite exhausted.