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Zorns Lemma

Member Since 12 Dec 2008
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Topics I've Started

Optimally done Optimal-Y

10 February 2013 - 03:50 PM

I devised this wye modification to enable near flawless use of silicone dome darts with hoppers.

Carbon had a similar idea for this, using CPVC. It served a similar role to BritNerf's flute, but in the back of the wye rather than front. However both BritNerf and Carbon's version have problems with silicone domes because the domes cannot navigate any sort of steep angle.

This flute is made out of SC80 1/2" PVC lathed down to .715" OD. The angle cut into it serves no purpose except to allow room for the dart to navigate through the wye. The goal of the flute is to prevent the dart from bottoming out on the wye and thus unable to seat well into the barrel.

The sloped section is 1.14" long and dips from .715" height to .35" height. The angle of curvature is option and was chosen to make cutting on scroll scroll saw minimally dangerous/effortful.

Posted Image

View from front:
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View from top:
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View from back:
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View from top with barrel in:
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I chose to cut the flute from the main body of the SC80 PVC so that it is detachable and held completely within the wye.

Diagram of how it works:
Posted Image

Cutting the flute from the pipe is optional. I did this because this was for the FAL-3 which already has a moving stub to connect to the back of the wye. If you need a connection stub anyways, I highly recommend leaving the flute attached and securing it with a screw so that it doubles as flute and a stub to connect your wye to your blaster


Firing data, indoors, room temperature (20-25C)
7" CPVC barrel
1.5" barrel stub from wye to blaster
Fired from seated position from the FAL-2
| = 1 dart fired on attempt
M = dart did not fire on attempt
D = 2 darts fired on attempt

Trials 1-6: 5 silicone darts in a thinwall 1/2" hopper clip with check valve on end
Unmodified wye
1: ||MD|
2: ||MD|
3: |||||
4: ||MDMD
5: ||MD|
6: ||||M|
Modified wye
1: D|||
2: |||||
3: |||||
4: |||||
5: |||||
6: |||||

Trials 7-9: 9 silicone darts in a sch40 clear 1/2" hopper clip with duct tape on end
Unmodified wye
7: ||M|M||||||
8: |||||M||M||
9: M||M|MM||M||||
Modified wye
7: |||||||||
8: |||||||||
9: |||||||||

Trials 10-13: 10 silicone darts in same sch40 clip as trials 7-9, ergo overfilled hopper clip
Unmodified wye
10: MD|||MD|||
11: MD|MD||||M|M|
12: ||||||M||||
13: ||||MMMDD||
Modified wye
10: ||||||||||
11: ||||||||||
12: ||||||||||
13: ||||||||||


21 December 2012 - 07:31 PM

I rebuilt this design http://nerfhaven.com...showtopic=21567to not be completely awful. snakerbot gets at least 50% of the credit.

-1-1/4" PVC (clear makes construction easier)
-1" thinwall PVC (critical to fit around 1/2" fittings, not critical if using a breech)
-7/8" ID x 1-3/8" OD U Cups 9691K56
-1/4" aluminum rod (substitutable)
-1/2" Delrin rod (substitutable)
-9/16" ID x 5/8" OD nylon tube 8628K57 (substitutable)

The priming pump is now constructed out of 1" thinwall PVC. The seal is created by sandwiching a u-cup between 1/2" PVC and 1/2" PVC couplers. The couplers then fit inside the 1" thinwall.

Channels are cut into the priming pump to fit around a wye. The stub of 1/2" PVC that extends through the u-cup seats with the wye.

The plunger rod consists of a length of 1/4" aluminum rod. The catch notch is created by turning 1/2" rod on a lathe to create the sloped omnidirectional ramp. A 1/4" hole is bored for the rod and secured with a set screw.

The plunger head is created by the same mechanism of 1/2" PVC and u-cup. It is seated between a section of 1/2" coupler and a 1/2" x 1" bushing. The plunger head is attached to the plunger rod via reducing the 1/2" PVC to 1/4" ID through tubes and 1/2" rod and then fastened to the plunger rod.

The plunger rod is cut to length so that the catch face meets with the catch at draw, thus it must be shorter than that length at rest

The catch is a standard rainbow catch, except with a 5/8" hole at the spring rest. This houses the 5/8" OD tube which fits inside the spring and yet is wide enough to allow unrestricted travel of the plunger rod and catch nub. This prevents spring buckling during compression which would cause tons of issues. I used a [k26] spring; use of a [k25] spring would enable 1/2" PVC to be used to center the spring (or some other tube of choice).

The trigger this time is mechanically linked from a rear trigger to front trigger via metal rod. This method is far superior than cutting a single large trigger. With better crafting of the rear trigger, you can use the physics of lever arms so that the trigger pull is much smoother (I was not paying attention and have a 1:1 ratio of horizontal to vertical movement. A 3:1 ratio would alleviate some of the stress on the stock trigger).

Functionally, this blaster is identical to the FAL-1. It is pump action except the pump runs coaxial and interior of the plunger tube, alleviating the need for linkages that would increase the length of the blaster.

The blaster is attached to the lower trigger housing (appropriated firefly shell) via polyethylene blocks. The blaster can be considered "unibody" except the 1-1/4" PVC body is segmented by couplers to allow for attachment points to the lower trigger housing and also to greatly ease construction and disassembly.

The barrel is held in place by a bushing at the front.

The blaster including barrel is approximately 30" long to the front bushing (the barrel in place is not the correct length). Here is a comparison shot with Ryan's newly shortened tubing blaster with vertical pump grip. Around 4" of the blaster can be cut down by rebuilding the front of the blaster more efficiently.

(Rebuilt to cut off 4" from the front)

Fallopian mk 2

11 December 2011 - 10:40 PM

The Fallopian 2 is an internal pump action platform. It was derived from looking at a PAS and the FAL-1 and trying to relocate where the floating tubes occur.

1. Easy to construct
2. Designed to seal better (with only 1 locking seal compared to 2 in the FAL-2)

1. Longer blaster (slightly longer without barrel, much longer with barrel)
2. Draw ratio limitations*

There will be a lot of similarity with the Rainfire, although this wasn't inspired or based upon it. There is just so much you can do with tubes inside tubes. A pretty crucial difference is that the catch does not move.

There is also high similarity with Beaver's plunger-prime system. The FAL-2 is also plunger-prime. However, the plunger tube is "free floating" as opposed to anchored around another pipe.

Demo blaster:
This blaster is 16" long without stock or barrel. It features a full-length plunger rod as opposed to a demi-rod, thus adding around 4" of length (with stock) that could've been removed by moving the stock and handle forward relative to the catch.
It has 10" of spring and 5.25" of draw. Obtaining 6.5" of draw would require 2.5" of compression (nb: not necessarily precompression) spacer to be added behind the spring and an elongation of the blaster by slightly over 2.5".

Plunger Rod and *draw considerations

Due to how the lip of the plunger tube must stop before hitting the catch spring, and then must also extend forward to no more than past the lip of the plunger rod seal, we have this essential equality:

[Draw] <= .5 * [Distance from back of plunger head to spring rest]

In the blaster mentioned, there is .5" of space from the seal to where the spring starts, the spring is 10", and the spring rest is precisely the front catch plate. Thus I am able to obtain 5.25" of draw, and also why moving that up to 6.5" requires the given spacer.

Once this little bit is understood, the rest of the blaster is extremely simple. Here is my plunger rod:

Notice that bit of tube between the rod and the back of the skirt seal. The rod itself is a unidirectional design consisting of 3/8" ID 1/2" OD tube over 3/8" OD aluminum rod. Since the catch surface is semicircular, the 1/8" depth catch contributes enough surface area to make the blaster immune to "drop-firing"

The markings on the rod are to help me measure where the plunger tube will end (it is the one on the left) and where the inner tube support will end (the one on the right). Notice the bit of overlap between the two: this allows the plunger tube to remain support at all times.

Finally, the length of your plunger rod should be enough to just barely pass the end of the catch. The simplest construct method is to over-estimate by a few inches and trim the excess later.


Floating the plunger tube

The best thing ever: 1" PVC nests nicely inside 1.25" PVC which nests nicely inside 1.5" thinwall PVC. The middle pipe will be our plunger tube, and the other two the inner and outer float supports.


The plunger tube is of length

[Length PT] = [Length space before sealing point] + [Buffer space (~1/8")] + [Draw]

"Space before sealing point" in the front consists of the bushing and the space in front of the plunger head (I have a neoprene square cross-sectional o-ring to act as impact dampening). The buffer space is the gap you want to leave between the actual point of seal and where you want the plunger tube to stop moving. If this is 0, there is a chance of your seal just falling out of the plunger tube.

A large portion of "space before sealing point" is a 1"->1/2" bushing which forms the female receiver of the locking seal. It will make more sense later.

I realized there was some confusion here so this is a diagram of what I meant:

The orange parts are what I consider "space before sealing point" and the neon green is "buffer space" The orange space has no multiplicative length effects (i.e. adding 1" there will just be a flat 1" length addition to your blaster) and does not affect draw. The green space will affect draw and thus is under a 2x multiplier.


Here is the full internal mechanism:

The clear pipe is 1-1/4" PVC. The white pipe is 1" PVC, with a lip beveled to fit around the plunger head seal. The yellow section is electrical tape binding a 1/2" delrin spring rest to the 1" pvc (there is also super glue). As the is no real stress on these parts a high strength bond is not critical. The grey sections are 1/4" polycarbonate pieces finishing up the rainbow catch. The bit of brown at the back is teflon tape around a 1"->3/4" bushing.

Here is the system priming:
And primed:

Outer shell

The outer float support is the outer shell. I used a piece of leftover rainbowpump priming shroud and just reappropriated it. The cuts should be pretty obvious. The only thing left is a barrel adapter. I took two 1-1/4"->1/2" bushings and cut them down to make 1 super long bushing and then ran some 1/2" PVC halfway through. This PVC stub is the male counterpart to the female receiver on the plunger tube.

Finally, you will want to drill a hole for the rainbow catch, mount the male barrel receiver to the outer shell with adhesives or fasteners and mount the catch/spring rest/stock section of the internal mechanism.

You will also need to mount a handle and create a trigger.

The priming handle is 2" PVC attached to a section of 1.5" PVC coupler attached to 1.5" thinwall PVC attached to the female barrel receiver on the plunger tube. You may discover superior methods.


Completed blaster, priming

Completed blaster, primed

Porn shot:

New Nerf Podcast

11 September 2011 - 03:27 PM

Episode 1 - wherein we talk about random shit for 74 minutes:

Featuring: JLego, Ice9, TED, Zorn, Gears

More to come with technical development of hosting and streaming.

All offenses intentional. Listen at your own risk. Particular risk groups for being offended include, but is not limited to: Curly, SoCal nerfers, steampunkers, flux capacitor manufacturers, and Nerf commissioners that take money and do nothing with it.
The viewpoints expressed within are not representative of the Nerfhaven administration but are exactly what we think of you.
If you can't play ogg files then fuck you and get a real media player

FAL-1: The Fallopian mk 1

31 August 2011 - 09:44 PM



Design goals:
- Compact pump action springer capable of shooting dart out of at least a 12 dart hopper clip with standard priming motion
The current iteration of homemade pump action blasters of the +bow, SNAP, and rainbow variety, up to and including the shortened pumpSNAP by snakerbot are all rather lengthy and bulky. The largest immediate impacts concerning a nerf war is portability and accuracy - a lengthened barrel amplifies any angular error from the intended path. Various attempts to circumvent this with pull strings and backwards plungers (Carbon's SNAP-4bp and taerkitty's adaptation) have non-intuitive and unergonomic priming motions.
The idea was to create a springer with the same over size (including barrel) of the backwards-plunger variants while maintaining the intuitive and more ergonomic motions of the forward facing varieties.

Critical design elements:
- Coaxial pump action mechanism that travels around the barrel/hopper
- Unidirectional "rodless" rainbow catch mechanism
The two largest factors of concern here are a shortening of the plunger rod such that when primed no part of it extrudes from beyond the catch, and to relocate the pump action system coaxially and internally (as opposed to any adaptation based of external rails).

- Poor materials planning leading to sealing issues [implementation flaw]
- Forward design difficult to produce [both design and implementation flaw]
* Can be solved with better prior planning
* Circumvented using casted pieces
- Obvious further issues with ad-hoc implementation
* Prolific abuse of electrical tape
* Plunger head implementation atrocious
* Poor spring choice
* Trigger system terrifying
This blaster pictured is a prototype and made with a nonoptimal selection of materials. In particular, the plunger head is unnecessarily hefty and could be shortened by over 60%. Also, on the actual blaster I have, the barrel-sealing piece was initially beveled too much and I had to splice in a new one. The adhesive used in the splicing was insufficient to hold up and broke 4 rounds into Apocalypse 2011. Proper construction initially would obviously bypass this.

There will be no materials list as anyone who understands how the blaster functions could come up with a better one. This is also not a true writeup as anyone who understands how the blaster functions could implement the design in more optimal (suboptimal?) fashion.

Priming Pump

I started with a section of failed RBP plunger tube and cut channels on both the top and bottom. In hindsight I shouldn't have cut the top channel all the way through. Originally I did so to facilitate addition of the wye, but discovered you could actually just "pop" it in.

The priming arm free floats in a piece of tube of exact ID (ID > 1.66", the OD of 1-1/4" PVC). The priming arm is then connected to a piece of tube of exact OD (OD = ID of previous tube, OD > 1.66"). To join the two, I used some internal coupler and some electrical tape.
The tubes in question are I believe 2"x1.6875" and 1.675"x1.5" This is probably wrong. It doesn't matter.

Thus, the priming pump now has a mechanism by which to seal with the inside of the plunger tube, by way of the aforementioned tubes of exact ID and OD.

To seal with the barrel, simply add a section of 1/2" PVC coupler.

In these steps you can see why you should have left a ridge on the pump tube so it gets better grip on the internal coupler. Also not picture, a lot of set screws.


Stick some PVC into the back of your wye. Then fit some more pipe/tube over it to stabilize it inside the 1-1/4" PVC.
I used 3/4" thinwall. And duct tape. This is clearly not the best way.

Take some scrap from the channels you cut in the 1-1/4" PVC and put it over the aforementioned pipe/tube to create a rail along which the pump can stabilize. Superglue is sufficient for this stage.

Now grab the tube of specific ID and work some magic. I used electrical tape. I probably could've used sections of internal coupler and then the tube of specific OD to achieve this way better.

Not pictured: a lot of set screws

Pictured: how the sealing mechanism works*
*see that brass? Yea that's from splicing new SCH80 in. I forgot brass sucks donkey nuts.


To achieve the unidirectional catch notch I went with something inspired by the 2-11 but prefabricated. McMaster sells these security nuts that double as awesome beveled washers: http://www.mcmaster....lnord/90013a200

I took this and put it on the end of some appropriate threaded rod. I then found some vinyl tubing to prevent the rod's thread from destroying everything.

The plunger head is an abomination and we shall not speak of it. I was lazy.

Catch and Spring Rest

Make a rainbow catch that fits the plunger tube you are using (2" PVC). Make the holes however large to accommodate your catch "notch." Make sure that when you cut the sliding piece that it isn't so short that at rest it goes past the halfway point. I kept it 1/8" above the center axis and beveled the inside lip so the plunger rod would have no issues catching.

In terms of the spring rest (front piece of the catch system), you also want to creatively attach some tube to support the spring. I did it by nesting tubes in tubes for a flat surface, a lot of MEK, and then set screws from the back of the catch. A smarter way would be to drill the front hole larger and then slide the tube in and secure it with normal-oriented screws rather than coaxial-oriented screws.

[ some magic happens here ]


Handle and Trigger

I used SNAP-style demicouplers to grip the plunger tube. Then I countersunk in wood screws to attach blocks (visually a SNAP handle, but the handle is 3/4" long. Using these blocks as attachment points, I added some polyethylene sheet. Then I screwed everything else in. The mechanism is a tiny lever trigger in the back, using a non-threaded spacer as a fulcrum. This then attaches to a horrendously long slide trigger that goes in front of the handle. You pull the visible trigger and the bar pushes back the lever which pushes up the catch. A all contact points (trigger bar, both sides of secondary lever trigger) to prevent wood getting destroyed, I added some teflon tape.

Final Product

With a barrel on, this is the same length as a rev 2 Rainbowpump without barrel. This would be shorter if your plunger head wasn't retardedly 2" longer than necessary. Further optimization in the front (using resin cast pieces?) could reduce another inch or so. Shortening the draw (5.5" on a 2" plunger tube is excessive) could also optimize the design.