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Discussion Starter · #1 · (Edited)
Before we start i want to say that this build was inspired by Snakebitey and his builds, but i have to say that i also had this same idea before seeing what he was doing with his VSR =) Go check his channel and builds :cheers:

https://www.youtube.com/user/theoriginalllama/videos


BE AWARE; I CAN'T RECOMMEND TRYING THIS UNLESS YOU REALLY WANT, AS THE NATURE OF THIS BUILD IS VERY EXPERIMENTAL

Introduction



As the title says, this is a guide to converting a VSR, or any other BASR with the required space to HPA with a tight budget and some work. Note; this shouldn't be compared to a Mancraft or Bolt. They are much more efficient, they have a better performance and they are alot more compact.

Pro's
-Very easy to reload
-Adjustable FPS
-Cheap to build (if you already have the tools)
-Very little to no mechanical wear
-Loud/quiet (the latter requires a suppressor or smaller tubing)
-Fun to build (atleast for me)

Cons
-Might not be that easy to build for some people
-Could be more gas efficient
-Takes lot more space than off-the-shelf systems

Required tools & other stuff

-A cordless drill
-Drillbits of various sizes
-Hot glue gun & good amount of glue
-Heat gun
-Heat-shrink tubing of various sizes
-Soldering Iron & solder
-Electrical pliers
-Sharp knife to cut the tubing
-Zip-ties of various sizes
-Multimeter
-Adjustable power supply for testing (recommended)
-Small flathead screwdriver
-Strong glue
-Dremel or similar with a bit for sanding
-A box of random screws and stuff
-PTFE tape

The Parts

-Step-up DC-DC converter, https://goo.gl/CRkNo6
-12V NC Pneumatic solenoid valve, https://goo.gl/qSSsEU
-Off-delay timer circuit, https://goo.gl/8vA1Lu
-Small lever switch, https://goo.gl/SizxN1
-Fuse holder, https://goo.gl/FZcm5Y
-Fuses, https://goo.gl/NAFUHz
-On-off switch, https://goo.gl/mRhkhP
-Pair of connectors, https://goo.gl/8DYPTA
-6mm OD pneumatic tubing
-Pneumatic fittings, 2pcs of 6mm tube to 1/8" thread and 90 degree 6mm tube to 1/8"
-6mm tube to 4mm fitting if you plan to use the Mancraft regulator
-Some cable
-Battery (5V - 12V)
-Connector for your battery
-Front stock screw but slightly longer

The parts cost me about 37 euros so it has been really cheap! I bought the tubing, fittings and converter from Finland so that raised the price a little bit. Hopefully i didn't forget something...

The Electrical Stuff



The wiring is pretty simple. When you connect the battery the step-up converter uses about 12,4mA at idle when raising voltage from 8,4V to 12V. That's why there's an additional on-off switch.

In my build i didn't use the power switch and fuse, mainly because of space limitations and because i like to live dangerously. :pop:

It uses about 400mA of current when the solenoid is being powered.
I used a 8,4v 1100mAh NiMH China battery so it's going to last a while. I wouldn't put a battery larger than 110mm x 34mm x 17mm.

And of course everything is soldered together and heat shrink inserted over for protection. Be extra careful to not melt the trigger switch or any other stuff when soldering!

Also be careful when measuring current with your multimeter that you don't exceed the max current of you meter!

Modifying The Stock



7mm holes should be good. You want the tubing to be able to move. I forgot to mark the drill position for the solenoid, but i think you can figure it out yourself =)

I drilled the hole far back to 10mm so that the quick release fitting wouldn't release the tube when the solenoid was tightened with zip-ties.

Next you want to smooth the right side of the stock where the triggerbox is. That will allow us to install a switch to the triggerbox.



Modifying The Trigger



Drill a small hole to the trigger. Then you need to find a fuse for example, cut it, take a small screw and screw it in carefully. this will activate the triggerswitch.



In the same picture you can see where to sand the triggerbox. Also you have to sand the spring guide stopper.



Now is the time to solder some wire to the switch. Choose the normally open contacts and carefully solder about 7cm length wires on. Then take your pair of random 2-pin connectors and attach them to the other end. Now the circuit closes when you press the switch. Remove the unnecessary contact that is left for some space saving.

Next take your switch and triggerbox and choose a suitable place for the switch. Note the position of the triggerbox screws.

Now you can take your glue of choice and install the switch.

Once the glue has settled and dried you can test fit the triggerbox to the stock. Dremel a bit more if needed.



Modifying The Receiver & Internals

Take your receiver, drill a fairly big hole to the position shown below.



Also smooth the edges so that when the tubing moves, the sharp edge wont harm it.

Now take your bolt assembly, open it and remove everything that's inside. Take your favourite cylinder head and either tap it to 1/8" thread or take it to a machining shop or something like that. Grab your 6mm to 1/8" fitting and PTFE tape and attach the fitting. Should look something like this:



Cut atleast 70cm length pipe and push it to the fitting, route the tube through the cylinder and the hole you just drilled to the receiver. Now assemble your rifle and route the tube out of the stock. Hold the tube and try to rack the bolt a bit. If the tube moves with no effort you can congratulate yourself. :shot: If not, you can try to sand the receiver hole a bit more or drill the stock hole to a larger diameter.

Lastly push the tube end to the stock, below the triggerguard.

Electrical Assembly

Now is the time to tune the electronics. Take your step-up converter, power supply and multimeter. Give the board the same input voltage you are going use when the rifle is finished, then measure the output voltage of the converter and with small flathead screwdriver adjust the potentiometer once the output voltage is at 12,5V.



Once the converter is tuned you can solder short input and output wires on it and cover it with hot glue. Including the potentiometer and wire terminals. This will protect the board and give the wire terminals bit more strength so the wires won't snap.

Crack open the off-delay timer case. you want to drill a hole to the top of the case roughly where the potentiometer is.



Route the cables how you want but be careful not to bend the terminal ends too much. Put the case back together and install a healthy amount of hot glue to hold the wires but don't glue the potentiometer!

Now you can go ahead and assemble the rest of the electronics. Leave some extra wire to make the final assembly easier. The trigger wire will come through the small hole behind the triggerbox.



Solenoid Valve

Now it is good time to check the airflow direction of the valve. Attach the fittings and put about 9 bars of pressure to it. If it holds, now you know which is the air input. Put the 90 degree fitting to the output and the straight fitting to the input.

The air input to the stock comes from the back of the stock and the solenoid will be sitting right above it.

Testing The Electronics

Once you have everything from above done, you can test the system when disassembled.

Plug in the battery, turn the power switch on and hopefully there is no smoke coming from the components. :shot:

Grab the good old flathead, press the trigger and you should hear an audible click from the solenoid, and see a red light from the delay unit. If the system suddenly stopped working, check the fuse. If it's shot, then replace it with slightly bigger one. if it keeps going off and the wires are warming then you have a short. Once the system is working you can adjust the delay to about 250ms for a start.

The delay unit needs power for the whole duration of the delay to stay on. As the delay is less than 1/4 seconds that doesn't really matter. Also there's a small delay until you can press the trigger again to shoot, which is completely normal.

Final Assembly



This is roughly how we want the components to be located.

First take your battery and 2 zip-ties and attach it to the top. Next route your trigger cable through the stock and plug in the connector. At the same time feed your electronics bundle to the stock from the back. We want them to be sitting at the very front. Pulling out the tube from the stock might help a bit.

Once the electronics are in, put the tube back in and connect your solenoid valve, push the tube to the output fitting and secure the valve with a zip-tie.
Cut another 70cm length tube and push it in from the bottom ( ͡° ͜ʖ ͡°) and attach the 6mm to 4mm fitting to the other end.

Lastly take the longer front stock screw and screw it in once the bolt is fully in the receiver. This longer screw will limit the bolt travel so that you don't pinch the tube accidentally.

If you feel that the solenoid on-time is bit too much you can disassemble and adjust it accordingly.

Rough FPS Measurements

Did some poor man's chronoing with the rifle. I did follow Redwolf Airsoft's chrono tutorial.

https://www.redwolfairsoft.com/redwolf/airsoft/BulletDetail?bulletID=34

Cheap Rainbow cola can was used and the gun was at 7,5bar pressure.
Straight through the both sides,
Through the bottom center and edge,
Through top centre and sometimes top corner so i guess it's at around 500fps.



I will be doing some measurements with a real chronograph once i get a chance and i will update this post accordingly. Also i'm planning to do a video about this gun.

But that's it for now and hopefully this post helped someone! :cheers:
 

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There is a consensus(Airsoft community), that having a single solenoid controlling a direct line, is too slow.
But there was always intended for low pressure setups, so it will be interesting to see how it performs.
 

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If you find a 5/3 valve, you can set it up (if you switch the pilot from 1 to 2) to run a resovoir on port 1, air in port 2, 3 plugged, 4 to cylinder, 5 vented. Pull trigger, shuttle moves, air in gets blocked, resovoir dumps to cylinder until empty/trigger let go. Let go and air in fills resovoir, cylinder vents

(I figured it out for a smp kuba 1000t system)
 

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Discussion Starter · #6 ·
There is a consensus(Airsoft community), that having a single solenoid controlling a direct line, is too slow.
But there was always intended for low pressure setups, so it will be interesting to see how it performs.
Yeah, i think this definitely has high fps potential but i don't know about consistency. But then again once i get my hands on regulated air supply i don't know why wouldn't it have
 

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Discussion Starter · #7 ·
If you find a 5/3 valve, you can set it up (if you switch the pilot from 1 to 2) to run a resovoir on port 1, air in port 2, 3 plugged, 4 to cylinder, 5 vented. Pull trigger, shuttle moves, air in gets blocked, resovoir dumps to cylinder until empty/trigger let go. Let go and air in fills resovoir, cylinder vents

(I figured it out for a smp kuba 1000t system)
That's actually quite genius. And simple.
Although it probably wouldn't fit in a VSR body.

But how the kuba system chambers the bb's?
 

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The kuba is an open bolt setup. It chambers as you fire. I have a 5/3 in 1/4"npt port size, non solenoid that's actually like playing card pack size, so it could fit vsr stock. And use mechanical valve pilot, and it's now non electric

Kuba cutaway:
 

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Discussion Starter · #9 ·
The kuba is an open bolt setup. It chambers as you fire. I have a 5/3 in 1/4"npt port size, non solenoid that's actually like playing card pack size, so it could fit vsr stock. And use mechanical valve pilot, and it's now non electric

Kuba cutaway:
Well that explains
 

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Discussion Starter · #10 ·
Small update on the build;
-No wear on the PUR tubing going to the cylinderhead despite rubbing on to the receiver
-Delay circuitry may jam, slightly adjusting the potentiometer fixes it. Everything else is working as they should.
-Haven't had the need to recharge the 1100mAh battery.
-Pressing on the cylinder end cap seems to help with airseal
-Haven't got an opportunity to properly chrono it as i don't have regulator nor bottle.

Once i took an air compressor with me to the game area 100km away. First i had the gun setup for HPA before the game start but the chrono was at the opposite corner of the field so back to spring i went.

Lunchbreak came and i converted my VSR from spring to HPA in rainy forest. Walked back to the car with the fellow organizer, i got 12v from cigarette lighter and compressor was in the trunk. Circuit jam happened and needless to say i was slightly pissed. The chrono man was cool about it so cheers to him! left the gun in the car since i didn't know what was wrong and at that point i had no motivation or interest to deal with it.
 

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Discussion Starter · #14 · (Edited)
Hey i just found this site and thread and didn't even realize that someone had done this while i was doing the same thing.... Only real difference in variation was solenoid placement
What kind of performance are you getting?

Btw to people watching this thread, the project has ended for now because of problems with performance. I think a valve with bigger Cv rating would help to get this efficient enough to actually use it. Also a buffer tank would be needed to have gas ready to be dumped into the barrel, since my regulator (Mancraft M.A.R.S) doesn't seem to have that ability to supply large amounts of gas fast.

Because of this the project won't continue in VSR form since the system will be simply too large. I already have improved wiring loom ready to use for future experimentation.

Thanks for your interest, i will be back once i have some spare money and time for this project!
:cheers:
 
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