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Pulley system Bullpup style surgical tubing powered blaster

01 July 2012 - 03:53 AM

After a long absence from nerf (or at least building nerf blasters) I finally graduated from the IB, and have had some time to work on the nerf ideas I have accumulated over the past year or two.

As with my other posts, I tend to ramble on with somewhat unnecessary back stories, so skip ahead if you are just here for the pretty pictures.

The Dwarf is the result of my attempt to develop a blaster with one simple goal in mind: minimize blaster size without impacting range or rate of fire. i.e. create a relatively small and maneuverable blaster that can compete with more well established homemades like the PACs and pumpsnaps in terms of both range and rate of fire.

To accomplish this goal I split the standard spring powered nerf blaster into what I consider to be its three main components, the plunger tube, plunger rod, and barrel. By folding the three of these over each other the resulting blaster is about a third of the size of its standard equivalent in terms of range. To achieve this I replaced the standard rigid plunger rod with a high grade flexible steel wire, allowing the plunger to be reversed without reversing priming direction. This resulted in a 22" long blaster even when primed and with a barrel with a ridiculous 8" draw.

While many don't like the pulley system due to it's perceived unreliability and complexity a few simple adjustments make the system just as durable and reliable as any other spring powered blaster system. The three primary changes are the use of a large diameter pulley instead of a smooth bolt, the use of a slightly more rigid plunger cable, and the use of an extension style powerhouse, in this case surgical tubing.

At this point I think it is important to give credit to both Carbon and Kane the Mediocre, without which this blaster would not exist. Kane was the first one I saw use a pulley system for a plunger rod, giving me enough confidence in the design to move forward with the project, and carbons introduction of both the Snap catch and extension spring style blasters provided me with simple solutions to otherwise complex problems (i.e. figuring out a functional catch, and more reliable powerhouse)


Without further ado I present to you "The Dwarf", small, but still packing a major punch.

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Exploded (note that disassembly to this degree only requires the removal of a single bolt, allowing for easy repairs of the plunger head).

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You may notice the build quality is significantly better than my previous projects. I spent much more time and effort on this build, and tried to create a functional end product, rather than just another proof of concept prototype that I usually produce. The end result is a sturdy blaster which is one of the most effective "spring powered" blasters I have ever owned.

Operation of the blaster is simple. To minimize size, while still allowing the blaster to be shouldered I opted to use of "bolt action" type priming mechanism, with the priming bar on the side of the blaster. While this is slightly less intuitive to use than normal pump action setups, after a while of use it becomes equally effective. This priming system allowed the grip to be at the very front of the blaster, balancing it out better, and cutting off a few inches in length since the priming handle and plunger tube are in parallel.

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The build is roughly similar to a Snap, operating off the same style of trigger, and utilizing the same types of materials, but that is where the similarities end. As is always the case, the materials available to me here in China are very different from those in the US, so I will simply explain the operation and construction of each part without providing concrete measurements (I will also avoid providing measurements because I am lazy, and more or less just eyeballed everything anyway).

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The plunger head is fabricated around a single bolt for strength, and is composed of three parts, each of which is made of a separate PPR endcap. The catch-face is also where the steel cable anchors by means of two holes which it is looped through, and then fastened with a wire clamp (left of image). The plunger itself is a cup seal from a ball pump (center). To ensure a perfect seal the PVC body of the blaster is not actually the plunger tube, just a shell. A large diameter ball pump tube is nested in the PVC. The slight gap between the pump tube and the shell is what allows the mechanical fastening of the grip and priming handle guide rail.

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Finally, in front of the plunger itself is a pvc buffer to protect the cup seal. This is also what the surgical tubing anchors to (explained later).

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One issue people have previously had with this pulley system style of blaster is the friction from pulling the "plunger wire" around a 180 degree bend. I have not however found this to be an issue. When developing this blaster I created a similar build with a traditional plunger setup with the same draw and power system (pictured below) to experiment with the most effective setup for using surgical tubing to power a blaster. The build (see below) was very similar to Carbons Snap Revolution (with the exception of the priming system), and performed almost identically to The Dwarf. I assume this is because the reduction in the mass of the plunger rod saves an equivalent amount of energy to the friction generated by bending the wire.

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One of the main innovations in this build is the use of a large diameter pulley. The pulley itself is not some specialized component that you will never be able to find. It is just a replacement wheel for an office filing cabinet with a channel dremelled in it. The channel acts as a guide to keep the plunger wire in place. If you do try to replicate this build (which I sincerely hope some of you do, just so you can experience to awesomeness first hand) make sure to bevel the edges of this channel. If this is done properly even when the wire "derails" priming the blaster again will seat it back in place.

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One VERY important component is the endcap at the front of the blaster. Drilling a small centered hole for the wire to slide through keeps the plunger wire centered on the pulley. Without this component the wire will quickly slip out of position and jam the blaster. This component also helps keep the blaster primed by keeping the plunger head aligned, and keeping it from slipping it off the clothespin catch.

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The primary advantages of using a large diameter pulley are threefold. 1, since the pulley itself is larger is will rotate slower, reducing rolling friction. 2, with a correctly sized pulley the plunger wire in the plunger tube, and the wire outside in the priming system are more or less in parallel, meaning there are no angular changes in the wire as the blaster is fired or primed. This results in a significantly smoother priming motion since the vector of the force opposing the priming motion remains unchanged throughout the entire pull (i.e. no extra friction by pulling the priming handle sideways agains the guide rail). 3, especially when using steel cable, a small bend greatly increases friction, as it bends the wire past its elastic limit. A larger pulley keeps the wire under its elastic limit, allowing for a smoother drawing and firing motion.

Also note the use of the 45 degree L to mount the pulley. This allows the pulley to be mounted more precisely since its placement can be controlled in two dimensions (sideways and forwards/backwards), which in turn helps reduce friction as described above.

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The blasters power source is also fairly unique. It is similar to Carbons Snap Revolution design, in that it pulls rather than pushed the plunger. As such it possesses the same benefits:

Greatly reduced plunger friction means a weaker spring can be used. Easier to prime, equal performance.
Safety: when the system is primed, the spring is trying to pull the blaster together, rather than blow it apart.
Having the spring inside the plunger tube means no more snagging the nail on the spring.

The system is not however completely identical, namely due to the complete lack of a solid plunger rod in which to mount to spring. Instead the surgical tubing is mounted in front of the plunger head (see below), pulling the entire assembly (like in the "Ultimator" rocket launcher). While this does introduce a certain amount of dead-space, if you are worried about ranges one of the great things about working with surgical tubing is that you can simply increase the draw almost indefinitely. I currently have the blaster set up with a ridiculous 8" draw (which puts it on par with a traditional blaster with 6-7" of draw), but there is no reason you couldn't do one with more than a foot of draw if you wanted to be ridiculous (and even then the end product would probably be smaller than a +bow with its barrel on). One of the great things about working with surgical tubing as a power source is that it is MUCH more flexible than springs, both extension or otherwise. You can vary tension, draw length, and draw weight by simply using more or less tubing, and wrapping it around a different number of times.

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The system releases air vertically, while housing the surgical tubing past the outlet as illustrated below:

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It is very important to support the assembly that houses the tubing because it is under a lot of stress when primed. The stock of the blaster cups the assembly, keeping the surgical tubing from bending the assembly sideways and breaking the seal on the front of the plunger tube.

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The priming system of the blaster is also fairly unique, and to the best of my knowledge hasn't been done before. A length of PVC, the priming guide, is bolted to the side of the blaster and a PVC T slides over it.

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Note that the T is cut so that it sits against the side of the blaster, and can snap on and off for easy disassembly.

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Otherwise this system is identical of standard pump action setups. The handle slides over the guide, and a bolt goes through channels in the guide tube. Inside the plunger wire is fed through a smaller piece of PVC that telescopes inside the priming guide and anchored on the other end.

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When the handle is pulled back so is the wire.

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Then the handle is returned to its starting position and is ready to fire.

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The feeding system of the blaster is also hopefully a new idea. I may start a separate topic just for it if people show interest, and if it actually hasn't been done before. It is a simple "wye-less" variant of the hopper, however several small modifications allow it to reliably shoot pretty much any "nano" sized foam ammo including streamlines, gumdrop darts, slugs, dome darts, etc. It combines the reliability of the RSCB with the rate of fire of the hopper. In actuality it isn't so much a hopper as an "SRSCB", a skewed RSCB.

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Its construction is almost identical to that of the RSCB with one extra step. Using this tool:

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You bend the barrel 45 degrees, and then mount the thing at an angle. Note that I am not sure if this will work with US materials like CPVC. My go to barrel material is the metric electrical PVC that they sell here which is much thinner, softer, and easier to bend than the CPVC that I have seen.

I have fired hundreds of streamlines through this SRSCB and have not had a single misfire (except one due to the wire derailing on the blaster, which wasn't the fault of the feeding mechanism).

The reason for this systems reliability is simple (Warning: rambling mode activated), and is best described by going through how I designed the SRSCB.

As you may notice from all my previous builds, I have always avoided using hoppers both due to the difficulty of getting wyes in China, and their inability to fire stock ammo (which is what we generally use here both because buying them in bulk from the factories is actually cheaper and quicker than making darts, and because it is easier to get new people interested when they already have some stuff to get started with). Instead I always opted to use an RSCB due to its reliability and ability to feed stock darts. The issues affiliated with feeding a streamline through a hopper were twofold. 1, their soft rubber tip made it difficult to get around corners (which some got around by sticking bits of cloth in their hoppers), and 2, their length and long rubber stems made bending them around a sharp corner difficult.

To fix these two problems I thought about how to seat the darts in the barrel before bending them around a corner, and about how to smooth out the bend in a hopper. By simply bending the barrel, and introducing the air source behind the bend a critical difference is made. Because the darts are already seated in the barrel when the blaster is fired air can ONLY escape if the streamline goes through the bend (if everything else is well made and airtight). As such unlike a conventional hopper which uses the preliminary burst of air from a blaster to blow the dart into position the full force of the blaster goes into bending the dart around the corner. This greatly increases reliability, reducing misfires. As a test of this system I actually created a 6" dart, just for giggles. It fed perfectly and went a good 90'.

The SRSCB is also more pneumatically efficient than a conventional hopper in that no pressure can escape from the system until the dart leaves the barrel. While my experience with normal hoppers is limited I believe that air can initially escape around the dart in a conventional hopper, until that initial burst of air properly seats the dart (please correct me if I am wrong). While this "waste" is negligible in slow air release spring powered blasters to my understanding this is why hoppers don't work as well on quick air release air tank/ air pressure powered blasters (since a greater percentage of the total volume of air released by the tank passes the dart before it is seated).

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As a result, while a conventional hopper may still be more efficient on a spring powered blaster (since the air doesn't have to go around a bend like it does in the SRSCB) the SRSCB has the added benefit of functioning just as well as an RSCB on air pressure powered blasters (which adds a whole new dimension to my old Mirage series blasters *wink*). The SRSCB also has the added slightly less significant benefit of not requiring a wye which I'm sure people in positions like me would appreciate (people out of reach from McMaster and other specialized hardware sites).

I know people will be asking about performance so:

General stats (with a foot-long SRSCB, powered by four strands of surgical tubing, 8" of draw)

Capacity: 6 streamline darts (or 18 1" slugs) but this can be pretty much anything you want...
Range: about 110-120', but again, this is variable. Four strands of surgical tubing offers a very smooth prime, increasing the draw weight and draw length would be easy.
ROF: How fast are your hands?

Also, remember to listen to Homer and drill "Speed Holes" (you don't have to use a pickaxe). On the first test I was getting like 40' ranges, and was really disappointed. Although they may not work on your car these holes did triple my ranges.

Of course I'll let you see all of this yourselves in the VIDEOS:

Blaster overview - shows how the pulley works, and how smooth the priming motion is.

Firing test - pew pew pew. Also, rockets.

Firing test of the test rig - for those who are interested.

All in all I am very happy with how this build turned out. With the introduction of only a few non standard materials (the filing cabinet wheel, cable, wire clamp, and surgical tubing), all of which should be widely available this blaster cuts standard pump action systems down by a factor of 3 in size while otherwise maintaining functionality. I am even more happy with the feeding system. One small change to the standard hopper has allowed for the use of stock streamlines in hoppers and, at least in my opinion, greatly increased reliability with only a very minor cost in range.

I am sure I haven't covered everything in this writeup, and am happy to discuss the pros and cons of pulley system, and extension powered blasters with anyone. Questions and comments both regarding the blaster and the writeup are very welcome. If anything was unclear don't hesitate to ask for clarification, I'll try my best to make myself clear.

Also, @ Taerkitty: I hope this changes your view of pulley system bullpup blasters :lol:

High Volume Springer, Easy To Make And Cheap Version Of +bows And Snap

01 March 2011 - 06:24 AM

I know I said my next project would be the Mirage 2.0, but there's been a few issues that will set me back (including a shipment of brass I waited months for from the US, only to find it crushed beyond repair on arrival :wacko: ).

The goal with this project was to create a high volume springer on par or with greater performance than +bows or SNAP's for cheaper (in the case of the plus bow), and with materials that almost any one in any country should have.

Although I thought about putting this in homemades, you really aren't making anything from scratch, just assembling some easy to find items.

This build should allow more or less anyone with some simple tools to create a powerful, war worth blaster.

One thing to consider is that I have not included specific measurements. This is not (purely) because I was lazy, but because the combination of materials I used are specific to Beijing, but the concept of the build should apply everywhere. Hopefully people will be able to replicate this with all kinds of other materials.

Without further ado, here is the Bargain:

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I DO NOT claim any sort of originality for this concept. it is little more than a plunger expanded Nitefinder that makes use of easy to find materials. Nothing is original about the firing system, what is original is how it is built, and what materials are used.

General materials:

-Ball pump
-Spring (or parts to make bow arms)
-Hot glue (optional)
-Any square rod the size of a NF plunger rod, I used aluminum U channel, but something like nylon rod would be better.
-Assorted barrel components (you can improvise)

As with any other springer this blaster is composed of three parts: Catch, plunger rod and tube, and loading system.

The catch is simple. By using a NF catch shoddy build quality is not an issue. It will be reliable. Simply butcher a NF like so (and I DID butcher it, the whole thing was done with wire cutters :blink: ):

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The loading system is completely to your preference. I used an RSCB for simplicity, and because it fits the blaster's form well.

Now the plunger assembly. This is where I think the stroke of genius is in this build. One of the biggest challenges (at least for me) has always been getting the seal right on springers. Unless you have access to precisely manufactured skirt and grommet seals, plunger seals are always a bit finicky until you get a system down.

By using a pump and the included plunger head, you ensure an absolutely perfect seal. All you have to do is reinforce everything to make sure it can take the pressure the system is under, and attach it to the rest of the blaster.

To prepare the pump cut off the BACK of the pump and remove the handle and plunger assembly. Widen the hole at the front, you can carefully remove the check valve for future use, or drill the thing to bits (you can probably do this with pliers, small wire cutters act as great reaming tools)

Simply fill any gaps in the plunger head with hot glue, and use a good deal of foam (mine is from a BBB missile) to pad the plunger head.

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Saw off the head of the pump and glue it to your plunger rod. Because the pump head was not made to take any pressure, build a spring rest behind the plunger head like so:

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This takes all pressure off the plunger head. Even if something breaks it will not be the plunger head (unless there isn't enough padding in front of it). TO prove how little stress the head is under I initially used hot glue to secure the plunger head to the plunger rod, after shooting well over 100 rounds it is still completely solid.

Then simply cut a catch notch,

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and make a priming handle.

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Assemble all the components like this.

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Note the PPR (PVC looking tube) inside the spring. These pieces are very important. Cut them so that they equal the length of your spring when fully compressed. When your blaster is primed it should look something like this:

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Then just slide the pump tube on and you're almost done.

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To keep the whole thing together apply E-tape to the two places seen in the picture. You can also hot glue the plunger tube in place, but that is not necessary. As long as you're fairly generous with the tape the thing will NOT accidentally come apart, but is still easy to disassemble if required.

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The performance of these things amazed me. On the basic version, with a 7 inch RSCB, about 5 inches of draw powered by a [k25] ranges were upwards of 100 feet. What I am really proud of however is how simple these are to build well. You can have next to no materials and make a perfectly functioning one of these. I think almost every nerfer has access to Nitefinders and ball pumps. Amazingly, when building my first version of this several months ago I still had not found a source for adequate lubricant, but by just preserving what was already on the pump head the whole thing functioned perfectly.

As usual, you can see this for your self:


And I always love being able to fire rockets:


One of the greatest things about this build however is that it is very adaptive. Just like the +bow or SNAP it can be built off of and customized for different purposes. Here is the same system with pump action priming and a stock.

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Also, because my pump was not long enough to allow for a full length [k25], I made this extension with a similarly sized chunk of PVC.

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The stock is simply bolted on.

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Although I still don't use hoppers because it is difficult to get them to work with streamlines, I made up for that with a massive 15" RSCB.

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The blaster has two power settings, one notch for pump action, and a second which you can manually engage for extra power. Both achieve over 100' for every dart in the RSCB. Ideal conditions (as in first dart in barrel) with 7.5" of draw results in a ridiculous 130'.

This is all shown in the Video.

I am hoping that this system will help introduce new members to the hobby with a simple build that yields high level results.

As usual, comments and suggestions both on the build and post style are very welcome!

The Mirage-ss, Simple And Effective Semi Automatic Design

02 December 2010 - 05:26 AM

Again, skip this bit if you don't mind the details of the project, and only want to see the completed blaster.

After being a bit disappointed with the speed that the Eccentric dropped off the page I am hoping that this will generate more interest. Being the last in my 7 original projects I think it is the most innovative and practical of them all.

Often people have tried to create a semi-automatic blaster that still achieves reasonable ranges, most notably in the case of cheesypiza001 who completed a design similar, but significantly more complicated than this one, and to my knowledge never completed a practical blaster off the concept. Major props to him because it was after reading his posts that this idea formed in my head.

Interestingly, like the Eccentric this build was originally going to be put into a maverick for feeding. After the failure of the Eccentric however I decided to save myself the trouble and go with an RSCB.

This is the continuation of the Mirage series, and although it started out as just a proof of concept, this design proved so effective that even the prototype is a VERY practical and respectable blaster. I will be applying the same pneumatic setup to a more efficient loading system and a nicer shell in the final iteration of the Mirage which I am working on now!

For those of you wondering about the name, Mirage is just the series, and SS stands for small and simple.

Start here!

After some trial and error, and a lot of waiting for materials I came up with this:

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Again, its ugly but I am incredibly excited about this concept.

Three components make up the propulsion setup.

-A Magstrike pump and bladder
-A modified hornet sliding valve (NOT the blast valve)
-A Big salvo tank (any back pressure tank will work, but this was chosen because it has a good amount of volume. Enough for greater than 100' ranges, but not so much that it is ridiculous to prime)

The operation is based off of the properties of a back pressure tank. If you know about how these work skip the next paragraph, if not read on.

A back pressure tank like the one in a Drain blaster, big salvo and hornet are triggered by changes in pressure. When they are pressurized, and you let some air out of the back the lower air pressure in the back of the tank pulls the valve backwards, releasing the rest of the air out the front firing the dart.

Normally these tanks are pressurized with a pump, released, and then pressurized again. In this case all of this is done beforehand and stored in the Magstrike bladder (the green sock in the image. The sock is just to protect the bladder from the sun).

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The pressurized air then equalizes the pressure in the bladder, and in the BS tank when the trigger is at rest:

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When the trigger is pulled, and the plunger in the valve slides past the port connected to the BS tank pressure is released and the tank fires:

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As the trigger is held down, it DOES NOT slide past the port which the bladder is connected to and so no air is lost other than that from the BS tank. Pressure from the bladder then pushes the plunger back to its original position and the process repeats. No return spring is needed, and this way when the pressure is too low the trigger stays compressed acting as an indicator for pressure levels. This way true semi auto is achieved. The bladder is fully pumped, and then a burst of air is released (equivalent to a normal BS firing) with each squeeze of the trigger.

The valve itself is the only modified component in the whole blaster. I simply cut it shorter and attached it to the trigger. I connected the last two connection ports. The first to the BS tank, the second to the Bladder and pump. Also, because there is actually a check valve in this valve, there was no need to plug the back of the valve (where the unconnected tubing sticks out):

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The rest of the build is purely about quickly putting together a test rig. A 12" RSCB constructed exactly like that on the Eccentric:

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This RSCB was actually developed for this build, and used on the Eccentric first. I needed an RSCB fast and efficient enough to complement the Semi automatic capabilities of this setup. See the Eccentric post for details on construction. Even the style of construction is the same. The tank is glued directly into the RSCB vertically, and the handle is Zip tied on. The trigger is equally simple. A hole drilled (by hand :cry: ) through the handle with a hex wrench going through it acts as a guide for the valve's sliding motion. The PVC scrap is just for comfort.

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The result surprised me a lot. Despite the sub-optimal barrel length the first shot clear 80 feet while the last goes about 70 (on average. Level with streamlines) and the ROF is incredible. I won't even try to put a value on it, but even with an RSCB its fast (Although the RSCB was just for testing purposes. The final Mirage will use a breech new feeding system I am developing).

The biggest surprise however was that with a full fill of the MS bladder at 20 pumps I can fire the blaster 6 times at full force. At just 15 pumps I can empty the RSCB (with 4 streamlines in it). (this goes to show just how inefficient the MS valve actually is)

It is also small and maneuverable!

Next to a BBB:

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And more:

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Of course I'll let you see all of this for yourselves:


Firing test

Overview of blaster

Humble beginnings (The very first valve test)

Feel free to ask any questions as this may be a bit confusing. Again, comment on the clarity of the writeup because there always will be more to come.

As far as I can tell this is the first semi automatic setup that is this simple and effective and I am surprised that no one has done it (or documented it) before. If anyone has and I have missed it major props to you!

The Eccentric, Airtech And Supermaxx Series Overhaul

19 November 2010 - 08:43 PM

I apologize for the lag in write-ups (for those of you who care), but now that my last writeup "Scrappy" is about to go off the page I figure I shouldn't put this off much longer.

Again, skip past this if you don't want to know about the design process:

The eccentric actually started out as my attempt at putting an Sm1.5k airtank into a maverick. After a lot of fiddling however I realized no matter what I did ranges would still be mediocre (since the barrels were more or less stock), and that you'd have to be superman, or use two fingers to overcome both the force of the release pin, and the immense friction in my less than ideal trigger design. Instead of following that train of thought, I looked into other feeding methods; finally looking into the RSCB system. Although I had had bad experiences with these in the past, with a bit more research I was able to add to the design, both incorporating the materials available to me, and making it more reliable (in my opinion).

I should also add that the name comes from this past. As it was originally designed to be a powerful "Maverick", "Eccentric" seemed like a name that would fit the bill well.

Pretty pictures, or at least important stuff starts about here:

As you may have gathered, this build is more or less putting an RSCB (Major props to those who developed it) on a pull-pin air tank (like the AT2K tank), but the difficulty was doing this in the most compact and efficient way possible. I believe that I succeeded.

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As with most of my builds, it isn't super clean, or even very nice to look at, but its functionality and ease of use are very good.

The main idea that this build was based around was to get the air tank outlet as close to the RSCB input as possible, reducing dead space (or in this case getting rid of it entirely). I did this by putting the tank in a vertical orientation, so the air flows directly into the T and doesn't have to bend around a corner increasing efficiency.

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To make this setup possible I used a clothes pin to construct a lever trigger setup. This also makes the trigger pull exceptionally easy. To make this all you have to do is drill a hole in the clothes pin (as in a SNAP), and bend the tanks firing pin so it moves with the clothes pin. The rest is then assembled exactly like a SNAP trigger (with L brackets etc).

This way when the trigger is pulled the release valve is also pulled:

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Securing this on is easy. I simply hot glued and Zip tied it on, and after several months of messing with it it is still rock solid.

I also used a bit of scrap to keep the trigger aligned properly with the SM1.5K tank I used:

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Everything else on the build is simply logistics to get the thing to work. What makes this blaster so sturdy is that the RSCB is the main component that everything is attached to. This means that a shell, or brackets are entirely unnecessary as everything is anchored to one central component.

The handle was an interesting part of this build. Much like my homemade handles of the past, this handle is made out of a coat hanger (as explained in my PASnapbow-s writeup). It is securely attached to the RSCB with zip ties, and then slightly reinforced with hot glue:

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The difference between this and earlier handles however is that the pump is incorporated into it. This means that to prime to blaster you automatically tilt it forwards to pump (as seen in the video) reloading the RSCB at the same time.

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The pump is the same type that I used in my Tiny Tim build, however this time it is not cut short, and instead is fully reinforced with a nice pump handle made from scraps at the bottom:

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The only difficulty with the pressure system in the blaster was reliably connecting the pump to the tank (I still haven't found barbed connectors anywhere). In the end I settled for using a smaller section of tube rammed into both sides, and then used zip ties as mini pipe clamps (sorry for the repeat image):

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The RSCB was a fairly new thing for me, and after failing an RSCB'ed HAMP as my very first build (sad I know...) I went overboard on ensuring that this RSCB would never fail. Besides the normal practice of reaming out the dart entrance to the barrel I found what seems to be a foreign PVC T, and nested a section of electrical PVC that slides smoothly over by electrical PVC barrel material. I then drilled a hole SMALLER that the head of a dart in the large diameter electrical PVC to serve as an passage for air from the tank. With the barrel removed it looks like this:

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The small hole in front of the dart leads to the tank. This way the dart slides smoothly past the hole, and nothing more than a mild tilt is required to put the next dart into firing position.

Then things were finished off with a simple breech for the RSCB:

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And it was done.

This is the most effective and practical sidearm I have made. the 7 inch RSCB allows 3 streamlines to be held (with one in the barrel), or about 9 1" stephans (or 18 "Nano-stephans" :blink: ). It even gets better ranges than my standard overhauled SM1.5k (in the mods and PJ's thread) because there are absolutely no leaks, and there are no annoying turrets or moving parts to mess with (like in the original design with the maverick). It can fire off three darts just as fast as my speed loader'ed nitefinder, but each shot goes to around 100feet (it is tough to tell with streamlines, my bad stephans go to about 90 feet, but they don't fit the barrel or RSCB properly)

...And it does all this at less than 1/3 of the size of the original SM1.5K

Here it is next to a BBB

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And just another picture for good measure:

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It may not look so nice, but it works very well, mainly because it is so simple (unlike the complicated mess that Scrappy was)

And of course I wouldn't leave everyone without a Video!

This is the 6th out of my 7 part release... the next one is the prototype for the new Mirage!

Also, just as a final note, I'd like to mention the DCIT made by Split and Koree (I believe). I find it to be a very under appreciated homemade, and although I didn't come across it until after this project, I do think the two projects are fairly similar in concept (although theirs looks significantly nicer), and that the Eccentric is basically an air pressure powered blaster based off the same concept.

Again, please give me any feedback to improve these write-ups as after the first 7 I already have another backlog of projects...

Scrappy, A Hornet Reborn

31 October 2010 - 12:17 AM

If you're lazy and don't like long intro's scroll down for some incredibly ugly (but interesting :o ) pictures.

Scrappy was an entirely unintentional project. After taking parts from my hornet for Tiny tim and the mirage I was left with 5 unused tanks, 2 release valves, and a bunch of other scrap. Not liking waste, the only option was to hook up several tanks to a single trigger for a kind of "shotgun" blast, and use up the parts sitting around gathering dust. The result was one of the most effective secondaries I own (yup, better than Tiny Tim). This is part 5 of my 7 part writeup of all the stuff I have done, and so in my opinion is the third most impressive / unconventional project I have worked on.

Welcome to the most image intensive of my posts so far. Read on from here (see? that wasn't too bad compared to my other long winded intros).

Here it is:

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Ugly, but very functional. Imagine 4 Tiny Tim's strapped together. The whole thing is only about a foot long (with barrels), and is surprisingly comfortable to hold

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The entire build consists of 4 major components:

-4 hornet tanks
-2 hornet blast valves
-1 cheap pump (the same type used in all of my builds, taken from a cheap water pistol, but the original hornet pump can also be used)
-1 hornet check valve (from where it is supposed to attach to the titan)

its function is simple, but the construction wasn't really so I'll try to explain this with pictures. Bear with me.

The pump output is split two ways in a homemade Vinyl T

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one feeds directly into one of the blast valves

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which then is connected to the bottom two air tanks, completing one of the blast systems:

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while the other goes to the check valve, which has an output that is split two ways

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one feeds to the blast valve

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and the other to set of tanks on the bottom of the blaster

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Although this may seem complicated at first, it is actually quite simple. The pump first pressurizes the whole system, priming all of the tanks. Then the first two tanks are fired with the blast valve that is on the non-return side of the check valve. Then the first set of tanks is not pressurized, but the second two remain pressurized because the check valve keeps air from escaping back into the de-pressurized tanks. The merit in this system is that you can keep the top two tanks primed and filled, and still be able to prime and fire the bottom two tanks multiple times.

In terms of actual loading, this works exactly the same way as Tiny Tim. Megas can be rammed down the acrylic coupler

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or micros can be loaded into the barrels

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The concept is simple, however this uses up much of the junk that people have left over from hornet mods or integrations, and is very effective as a secondary. also, besides the blasts of two darts, multiple darts can be loaded in each barrel to launch clouds of foam into the air (made all the cooler by the fact that you can do it again immediately afterwards).

The main difficulty in this build was down to materials for me. With proper tubing connectors, and perhaps some machined spacers this would be both much easier to make, and look at.

In my case, the whole thing is arranged and held together (quite solidly) with E-Tape. My greatest challenge however had to do with connecting the actual tubing. Using vinyl tube that could be forced inside the stock hornet tubing for an airtight seal, I fashioned multiple connectors by jamming these in place. For the T's and connections to the blast valves I drilled or cut holes in the tubing or valves, and epoxied everything in place. It was a lot of work, but well worth it for the result. When I have more time I may revisit this design and make it cleaner.

in terms of performance however there is little to be gained. Because of the dead space between the tanks of blast valves the ranges aren't as good as those of Tiny Tim, but the 80 foot ranges are certainly respectable for a shotgun type blaster of this size. It takes just 15 full pumps from the reinforced water pistol pump to bring this to pressure:

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and the function of everything is very smooth. The handle of the pump is the actual grip meaning that you're hands don't have to move to prime the system. Although the location of the blast valves are unconventional for a trigger, using you're thumb to activate this blaster feels right, and the hornet tanks themselves make a great foregrip. The valves are even numbered. If I release them in order everything works fine. If I hit "2" everything goes off, because the check valve will let the pressure spill out of system "1".

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Overall the whole thing is quite comfortable to hold:

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And yes, of course there is a video; or two:

Micros (Oops! the barrel fell off. That one must have been made out of my thinwall barrel material :lol: )


And the damage after the two videos:

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I realize this is probably very confusing, so again, feel free to ask any questions, and please mention anything I can do better in these writeups, because the top two out of the 7 writeups are coming soon!