Guide: Mos-Fet in V2

[Renegade)]

Mosfet switch in a V2 SR 16, rear wired + battery bag mod:


This guide hopefully will help anyone with the installation of a mosfet unit, http://www.airsoftcanada.com/showthr...ghlight=mosfet ,into a Version 2 M4 variant. I am sure there a few already out there with this mod complete, however mine was done in a way that can support my current set up which includes a battery bag on my collapse stock. It can also work for a full stock as well, probably a lot easier.

How long did it take? 6 hours... no I know what your thinking now, how does it make it easier when it takes 6 hours? 5 of those was figuring out how to put it in so that everything fits snug, and does not A) cramp the gearbox, and B) will keep the wires and the unit itself protected from any damage. I did all the hard work and thinking for you, and hopefully this can be painless for future installations. What I did was simple, the only wires running through the mech are the trigger wires, space is limited for your wires to fit snug and not get torn up by the motor or gears. The unit itself is on the outside of my gun (see first piture) right on the rear of the mechbox and body, heat shrink’d up securely, and my motor wires actually run from the outside, through a channel I cut in the grip down to the motor, the battery wire just goes right to the stock with battery bag on it.


Note: This should be done by someone with proper mechbox experience and general wiring knowledge as it requires the use of a solder gun.

What you need:
Mechbox tools - whatever you use to take down your gun and open the mechbox up
Solder iron, solder and solder paste
Heat shrink tubing -various sizes, I used 1/8", .255" and .427"
Wire stripers, pliers, utility knife
Patience and good workspace

First of all, you follow Kos-Mos general guide, solder both of the trigger wires in place of your stock red wires on the trigger unit, does not matter which goes where. Before cutting any wires, and you will need to depending on your set up, make sure you pre wire it up, run the 2 wires through the wire channels and out of the mechbox, and put the 2 halves together and make sure the motor will clear the wires, and that you have enough left over to work with on the outside and in. Solder the wires on the trigger and reassemble the unit to make sure it all goes in correctly.




After I had the trigger all wires up and everything back in the mechbox correctly, I went to work on the unit on the outside, making sure I had enough wire after cutting it, so that the wires can feed through the body, as well as sit on the outside snug, and does not move around. Movement and to much slack can get the unit damaged or caught during play. The motor wires were my biggest problem, I finally got clever and just cut a channel in the inside of my grip that meets the first(rear) wire hold, then just enlarged that for both wires to fit through, measured them up so that they connect to the motor correctly, and voila! The tip of the G27 grip hides them perfect with barely any hanging out below the mosfet.



After every wire was measured up perfectly, I soldered all the wires together, with individual 1/8" heat shrink for insulation, then the larger .255" for the wires themselves, and a couple peices of .427 for the unit itself as I actually had to open it up, and spin the unit around so that the motor wires were on the bottom and the battery leads where at the rear.



Final Product: Well after everything was wires up, insulated and wrapped up, I was very impressed with the performance, crisper trigger response, bit of ROF, and it does not stick out that much more than the wires I had before. It sits in just behind the gun itself, the wires to the mech and the grip keep it fairly strong and supported. I run a pretty upgraded gun so this is a smart add on to my SR, and I recommend it highly!





Any comments or questiosn, feel free to leave them.

Thanks for reading, and good luck if you try this yourself!

Derek
Renegade)

[mcguyver]

I know why guys do these mods. When you want the best of all options:

Large battery
Collapsible stock that isn't 8 inches wide
FETs to decrease switch loading and improve current usage

But I do also see a few potential problems:

1) A single FET is never as reliable as 2 in parallel, no matter how big the rating. Motor loads are different from resistive loads, both in actual current draw and cemf present in the system. I have seen only 1 or 2 designs out there that are even close to what I would consider ideal for an AEG and a single FET soldered with on-line instructions is not one of them.

2) Exposed wiring on any gun is bad news. There is just far too much risk that that the wiring will be pulled, chafed or otherwise damaged during routine play. Enclosed in a solid structure like a grip or a stock is always better.

3) The joint for your FET/connections is precisely the spot that will be under the greatest strain, even with just the weight of the wire. FETs are designed to mounted to a PCB or similar rigid device. You let your battery slip on you when you're changing it and you'll have a heck of a mess.

I know you put alot of thought and work into this project and I don't mean to sound harsh, but I call'em like I see'em, and you did ask for comments......

[Renegade)]

Originally Posted by mcguyver

I know why guys do these mods. When you want the best of all options:

Large battery
Collapsible stock that isn't 8 inches wide
FETs to decrease switch loading and improve current usage

But I do also see a few potential problems:

1) A single FET is never as reliable as 2 in parallel, no matter how big the rating. Motor loads are different from resistive loads, both in actual current draw and cemf present in the system. I have seen only 1 or 2 designs out there that are even close to what I would consider ideal for an AEG and a single FET soldered with on-line instructions is not one of them.

2) Exposed wiring on any gun is bad news. There is just far too much risk that that the wiring will be pulled, chafed or otherwise damaged during routine play. Enclosed in a solid structure like a grip or a stock is always better.

3) The joint for your FET/connections is precisely the spot that will be under the greatest strain, even with just the weight of the wire. FETs are designed to mounted to a PCB or similar rigid device. You let your battery slip on you when you're changing it and you'll have a heck of a mess.

I know you put alot of thought and work into this project and I don't mean to sound harsh, but I call'em like I see'em, and you did ask for comments......

Very true on all counts mc, there are flaws in their for sure, and a full stock would be smartest, or up in the buffer tube, I havnt gone that far yet to do so, maybe later when I get the time and tools to do that. I have played 2 games so far, tough ones crawling through brush, rollwing, shooting from prone, ect, and have not had a single problem. I never said it was imune to problems, just that it was about the only place for it, and the most convinient I could do. Im sure there are a few others out there with the same battery and bag as I do, and would feel this might work for them without having to purchase 200 dollar worth of cranestock and battery. That or run miles of wire all over the gun from front to back for a large battery

I wrote the guide for that purpose, not to state the smartest way to put it in, if that were the question, I would for sure say full stock or crane. Of the people I told after I was completed weeks ago, I was asked to take some pictures and write up what I did, so there it is!