Jump to content


Photo

Bowpup

Ultracompact Pump Action Crossbow

12 replies to this topic

#1 Daniel Beaver

Daniel Beaver

    HQRSE CQCK

  • Moderators
  • 2,062 posts
  • NerfHaven Subscription Supporter
  • Location:Minneapolis
  • State:Minnesota
  • Country:United States

Posted 16 June 2012 - 09:29 PM

Introduction

As some of you may know, I am a fan of bow-powered weapons. Nothing else performs quite like them in a war. But they all suffer from a major problem: their grotesque dimensions. The Bowpup is an attempt to make a more compact configuration, while maintaing the desirable performance characteristics of a PAC.

Posted Image


This is not exactly a "small" gun, but it is significantly more compact than a standard PAC - 28" vs 48". And while the bow arms are just as large as a regular PAC, their location relative to your body means that they should not hamper your mobility to the same degree. The blaster has 6" of draw, uses a 16" barrel, a footlong hopper, and is capable of shooting between 200-250fps depending on the tensioning.

FIRING VIDEO


Materials
(I lifted these from an earlier writeup, so there may be some mistakes)

- Required
* Optional, but recommended

Tools
- Power drill
- Drill bits to go with it (1/16", 1/4", 1/2", etc)
* Tapping bits
- Rotary tool (dremel)
- Reinforced cutting disk
- Sanding bit
* Diamond cutting wheel (better for cutting plastics)
- Pipe cutter
* Three-sided drafter's ruler

Plunger rod
- 1/2" cpvc
- 1/2" cpvc cap
- 1-1/4" OD 1/4" ID washers
- 1/4" screw
- PVC cement OR superglue

Plunger head <- don't feel obligated to follow this exact design
- 1-1/2" OD 1/4" ID (or smaller) rubber washer
- 1-1/4" OD 1/4" ID (or smaller) rubber washer
- 5/6" OD 1/4" ID (or smaller) rubber washer
- 2x 1-1/4" OD 1/4" ID washers
- Spacer (can be any size you want, as long as the nail fits)
- 1/4" bolt, 5/8" long
- 1/2" CPVC cap
- epoxy putty
- Silicone grease

Plunger tube and stock
- 1-1/4" sch40 PVC
- 1-1/4" PVC tee
- 3/4" PVC endcap
- Duct tape
- 1" PVC cross

Trigger
- Heavy-duty clothespin
- 1-3/4" roofing nail
- Metal L bracket
- zip-ties
- Epoxy putty
- Hot glue

Priming handle
- 2x 1-1/2" PVC coupler
- Tape or glue
* Tennis raquet handle tape

Handle
- Donation blaster
- 1-1/2" PVC
- 1/4" set screws,
- 4x 6-32 screws, 1/2" long (3/8" or 1/4" are be better, but sort of difficult to find)
- Epoxy putty
- Hot glue


Construction


This writeup is not as comprehensive as my previous ones. Many of the construction techniques and materials are identical. If I neglect to describe certain features (e.g., the handle, the plunger head) it is because those features were described in great detail in the Quixote writeup. You should also use the SnapBow Mk. V revised and SanchoPanza writeups as references.

A note: I will avoid giving out exact dimensions in this writeup. This is because minor deviations in construction methods can result in major cascading dimensional changes. For example, using a slightly longer grip would alter the total length of the plunger tube, the location of the trigger, etc. When building, you should first determine what features you want (e.g., draw length, grip length, the size of your clothespin) and then derive dimensions from that.

Here is an overview of the internals. The configuration is very similar to the Sancho Panza - a bullpup SNAP, where the plunger rod travels backwards.

Posted Image

The plunger head is a standard superlative plunger head. Follow the link to Rork's guide if you don't know how to build these. I use 1/4" bolts for SNAP plunger heads, and my materials list reflects that. The Quixote writeup includes some more tips and tricks. Don't feel obligated to use this design, there are all sorts of ways to build plunger heads.

At the end of the plunger rod I glued on an CPVC coupler, which I drilled holes in and fed through the bowstrings. I nested a small stub of CPVC into the rear of the coupler, just to add more material. You can also just drill a hole straight into the plunger rod, which is probably strong enough by itself.

This image is from the SanchoPanza writeup, so ignore the spring. Bow power is better.

Posted Image


Cut the slots. These need to be centered, otherwise the bow string rubs against the side during firing. You can always widen them if you screw up the initial cuts.

Posted Image


The priming handle is mostly identical to what I used in Quixote: two 1-1/2" PVC coupler connected together with tape. If you have access to 1-1/4" thinwall PVC, you can use that instead. I wrapped tennis raquet grip tape around them.

Posted Image




The handle is similar to ones I have used before. I fill the internal with epoxy putty, then attach the PVC with set screws and JB weld (very strong). Note that you cannot use thru holes to hold the handle - you would be poking holes in your plunger tube! Instead, use a snap-on handle and a ton of hot glue. Hot glue is deceptively strong when applied liberally. Zip-ties are useful here.

Posted Image


Cat!

Posted Image


The trigger is very standard. Refer to Rork's writeup for how to make these.

Posted Image


The rear of the plunger tube contains a standard 1" to 1/2" bushing, press fitted with packing tape and sealed with goop. There is no need to secure this with screws.

Posted Image


Two PVC elbows redirect the air up into the hopper. A 1-1/4" PVC tee encloses and supports this section. You will need to cut a slot in the top, otherwise you won't be able to fit the elbows into the tee.

Posted Image


The bow arm support is a 1" PVC cross. There are two 1" PVC stubs in the top and bottom openings which recieve the bow arms. The front and back openings are wrapped in duct tape until they fit into the 1-1/4" fittings used in the stock and the plunger tee section.


Refer to the PAC writeup for how to make bow arms - mine are 3/4" PVC, which is an inferior material (you should use 3/4" CPVC if it is availible to you). The length should be somewhere between 18"-22". I used two discrete bow arms, but you will get better performance if you use a single large bow arm fed through the cross.

Posted Image


Here is a closeup of what the rear assembly looks like. I use an L-shaped stock, but you can use whatever you want (PVC tee, a raider stock, wood, etc.)

Posted Image


Plunger tube, barrel and hopper added. You should add some goop to the connection between the PVC tee assembly and the plunger tube. You might also consider adding a dart stop somewhere behind the hopper to prevent darts from being sucked into the plunger tube.

Posted Image


Handle, trigger and priming handle added. You should use zip-ties liberally when attaching the handle and trigger. Remember: you cannot use screws to attach your handle! It is not pictured here, but you need to add a support for the barrel - it flops around otherwise. Use whatever is laying around the shop, and use a dremel grinding bit to cut a small groove in it.

Posted Image


Just a little something that is pretty important:

The bow arms and hopper are offset by about 45 degrees. If the hopper was oriented straight up, you wouldn't have any place to put your head. If the bow arms were horizontal, the left-hand bow arm would hit you in the shoulder. If the bow arms were vertical, they would smack you in the face. This configuration gives everthing clearance.

Posted Image


Lubricate the plunger head with silicone grease - accept no substitute. Run the plunger head through the blaster a few times to get it lubed up, adding a little bit each time. String up your bow - be sure not to go overboard on the pre-tension, you need less than you might think.

Done.

Posted Image


Bonus: it breaks down for easy storage

Posted Image


Fuck yeah, bitches

Posted Image
  • 0

#2 jackrabbit

jackrabbit

    Member

  • Members
  • 53 posts
  • State:Connecticut
  • Country:United States

Posted 16 June 2012 - 10:03 PM

Is the face diddle as bad as it looks? Btw great write-up!
  • 0
Like a good neighbor my dog shits in your yard.
Like a good neighbor I watch your wife bath.
Like a good neighbor plant the drugs in your car.
Like a good neighbor pick your kids up in my white van.
"Allstate Oh Hell No"
Copyright 2010-2011 Allstate Insurance Company. All rights reserved.

#3 koree

koree

    Member

  • Members
  • 311 posts
  • NerfHaven Supporter
  • Location:Philadelphia
  • State:Pennsylvania
  • Country:United States

Posted 16 June 2012 - 10:21 PM

I so need to try this. Looks great!
  • 0

#4 Bchamp22795

Bchamp22795

    Member

  • Members
  • 209 posts
  • Location:Bloomington, IL
  • State:Illinois
  • Country:United States

Posted 16 June 2012 - 10:21 PM

Is the face diddle as bad as it looks? Btw great write-up!


I think he mentioned in the picture thread (or somewhere) that the bow arms actually don't hit his face since he angles them away slightly. I feel like it would be pretty easy to slip up and get your face diddled...but I guess we'll just have to make one and see.
  • 0

#5 Daniel Beaver

Daniel Beaver

    HQRSE CQCK

  • Moderators
  • 2,062 posts
  • NerfHaven Subscription Supporter
  • Location:Minneapolis
  • State:Minnesota
  • Country:United States

Posted 16 June 2012 - 10:23 PM

I think he mentioned in the picture thread (or somewhere) that the bow arms actually don't hit his face since he angles them away slightly. I feel like it would be pretty easy to slip up and get your face diddled...but I guess we'll just have to make one and see.

You got it - the bow arms stay well away from your face. The one you have to worry about is the one at the bottom - it's the ballywacker. I still need to try this out at an actual war to determine it's utility.
  • 0

#6 Exo

Exo

    Member

  • Members
  • 391 posts
  • Location:SoCal
  • State:California
  • Country:United States

Posted 17 June 2012 - 01:03 PM

You got it - the bow arms stay well away from your face. The one you have to worry about is the one at the bottom - it's the ballywacker. I still need to try this out at an actual war to determine it's utility.

If you're worried about the whacking motion and not the sliding motion (that usually contributes to face diddle) you could install an arm limiter. Just take a piece of 1 to 1.5" PVC, cut it in half hot dog style, and place it so that it would stop the bow arms from impacting that certain area.
  • 0

#7 The Nerfaholic

The Nerfaholic

    Member

  • Members
  • 185 posts
  • Location:Jersey Shore
  • State:New Jersey
  • Country:United States

Posted 17 June 2012 - 06:43 PM

I love this thing so much. Although how sturdy is that string? I know in the Snap 7 Micro Bow Carbon used thin steel wire. I fear anything snapping with the force this thing has to put out, and face diddle.

P.S. I love your cat.
  • 0
Roses are red, And violets are blue. One day we'll cruise down Blood Gulch avenue.

#8 Daniel Beaver

Daniel Beaver

    HQRSE CQCK

  • Moderators
  • 2,062 posts
  • NerfHaven Subscription Supporter
  • Location:Minneapolis
  • State:Minnesota
  • Country:United States

Posted 17 June 2012 - 07:07 PM

Although how sturdy is that string?

It's not sturdy, I just happened to have some masonry line laying around. You should use a thicker nylon or polyester rope, and take a backup bowstring to any wars. Steel wire is way overkill, IMHO.

Edited by Daniel Beaver, 17 June 2012 - 07:08 PM.

  • 0

#9 The Nerfaholic

The Nerfaholic

    Member

  • Members
  • 185 posts
  • Location:Jersey Shore
  • State:New Jersey
  • Country:United States

Posted 20 June 2012 - 07:01 AM

Have you done a range comparison between a regular SanchoPanza with just a spring, and the bowpup?

Edited by The Nerfaholic, 20 June 2012 - 07:08 AM.

  • 0
Roses are red, And violets are blue. One day we'll cruise down Blood Gulch avenue.

#10 Daniel Beaver

Daniel Beaver

    HQRSE CQCK

  • Moderators
  • 2,062 posts
  • NerfHaven Subscription Supporter
  • Location:Minneapolis
  • State:Minnesota
  • Country:United States

Posted 20 June 2012 - 07:16 AM

Have you done a range comparison between a regular SanchoPanza with just a spring, and the bowpup?


I had measured the SanchoPanza at 230fps on the chorno, and the Bowpup at between between 200-230fps depending on the bow tension. My prototype Bowpup actually shot a little bit harder, closer to 250fps. In terms of ranges with slug darts, that ends up being between 100-130ft (about 150ft if you're using dome darts).

For reference (with slug darts):
100fps is what most springer pistols shoot, equating to about 60ft
150fps is around 80ft (a lot
200fps equates to ranges around 100-110ft (century blasters. Most PACs and hoppered springers shoot this hard)
250fps is closer 130ft (this is typical of SuperMAXX and Airtech guns. Only very powerful and well-built springers shoot this hard)
Beyond 250fps makes very little difference (this is the realm of Titans, Big Blasts and other shitcannons)

If you haven't figured it out, 200fps is a sweet spot for power - fairly easy to achieve, while shooting only slightly less far than much more powerful blasters. When I build blasters, I always try to strike a balance between ergonomics (ease of priming and size being the main factors) and power. While I CAN tension the hell out of the Bowpup to push it up into Superpowered territory, it is much more sensible to tone the tension down so that it is easy to prime.

Edited by Daniel Beaver, 20 June 2012 - 10:35 AM.

  • 0

#11 Swatsonia

Swatsonia

    Member

  • Members
  • 35 posts

Posted 20 June 2012 - 09:02 AM

Made one of these over the last few days (though it looks more like your original prototype, due to a lack of PVC crosses in Aus).

I must say, it is as enjoyable to use as my Crossbow or Snapbow, which is a surprise.
  • 0

#12 Daniel Beaver

Daniel Beaver

    HQRSE CQCK

  • Moderators
  • 2,062 posts
  • NerfHaven Subscription Supporter
  • Location:Minneapolis
  • State:Minnesota
  • Country:United States

Posted 20 June 2012 - 10:27 AM

Made one of these over the last few days (though it looks more like your original prototype, due to a lack of PVC crosses in Aus).

I saw that on OZnerf. I run into the same issues, which is actually why I used a 1" cross (I originally meant to use a 1.25" cross, but couldn't find one). You should try to add a stock to yours; there's nothing inherently wrong with my prototype design, but it really helps to have a stock. The bow arms are a little too close for comfort otherwise.

Also: are you left-handed? The blaster in the video looks like it's made for a lefty. Langley would be pleased. He gets all pissy because I make these non-ambidextrous blasters which he is incapable of operating.

Edited by Daniel Beaver, 20 June 2012 - 10:39 AM.

  • 0

#13 Swatsonia

Swatsonia

    Member

  • Members
  • 35 posts

Posted 21 June 2012 - 04:47 AM

I saw that on OZnerf. I run into the same issues, which is actually why I used a 1" cross (I originally meant to use a 1.25" cross, but couldn't find one). You should try to add a stock to yours; there's nothing inherently wrong with my prototype design, but it really helps to have a stock. The bow arms are a little too close for comfort otherwise.

Also: are you left-handed? The blaster in the video looks like it's made for a lefty. Langley would be pleased. He gets all pissy because I make these non-ambidextrous blasters which he is incapable of operating.


Nah, I'm a righty, though my dad is a lefty. It's probably just the camera on my macbook flipping the picture around. One possibility for a stock addition would be to add two tees either side of the bow arms, and then making a "U" shaped stock, which should be solid enough, though I like it the way it is now.
  • 0


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users