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Plusbow Rev. 3

spring plunger homemade write-up guide

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#1 CaptainSlug

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Posted 30 June 2016 - 08:48 AM

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bow3_007.jpg

 

Plusbow Rev.3 Guide

 

Instructables Mirror

 

Design Goals

  • Reduce Part count
  • Two Options for Plunger tubes and Plungers (+bow or 2-11)
  • Omni-directional catch
  • Spring guide to remove "serpentine" behavior
  • Ease of dis-assembly
  • Limit screws to two lengths (1/2" and 1-1/2")
  • "Check Valve" Plunger head
  • Use of extension springs or rubber bands for catch (multiple configurations possible)
  • "Ultra-Compressible" O-Rings
  • NO MORE INTERNAL CUTS, that means no pilot holes, no feeding a scroll saw blade through a pilot hole. Every cut can be done with a scroll saw or a band saw.

Total Build cost: $70 (for one plunger tube type)

Sunk Cost per Plusbow: $25

 

 

Thanks to: Splitlip, Aeromech, Ryan McNumbers, Groove, CrankyMonkey, VACC, and TED


Edited by CaptainSlug, 06 July 2016 - 08:28 PM.
Write-Up Added

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#2 The2ndBluesBro

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Posted 30 June 2016 - 09:08 AM

Looks pretty good. I still prefer the rev 2 but there are definitely compelling reasons to build this now. How did you deal with the stress of the plunger hitting the front without the side plates?
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#3 xXD3V1LXx

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Posted 30 June 2016 - 09:18 AM

I have actually been working on a noobs crossbow. Looks like i was beaten to another generation of crossbow/+bow homemades. Anyways looks great cant wait for the finished product.


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#4 CaptainSlug

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Posted 30 June 2016 - 10:03 AM

Looks pretty good. I still prefer the rev 2 but there are definitely compelling reasons to build this now. How did you deal with the stress of the plunger hitting the front without the side plates?

The 2-11 style plunger tube is 1/8" wall polycarbonate and doesn't require external reinforcement.

 

The +bow style plunger tube for this revision is aluminum, which now ends up being the same price per foot as the older polycarbonate tube but with more strength. (part# 1658T18)

Splitlip used that same part number before, but the price has come down since then.


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#5 Langley

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Posted 30 June 2016 - 01:30 PM

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Looks good, can't wait for the writeup.  Any plans to add pump-action?

 

My biggest complaint with the earlier revisions is that the stock is very wobbly and easy to twist.  It could add a lot of stability to the stock if there were a third support extending diagonally from the bottom of the pistol grip to the bottom of the butt plate.  JLego's plusbow variants all have something along those lines and their stocks are solid as a rock. 


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#6 The2ndBluesBro

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Posted 30 June 2016 - 01:34 PM

Looks good, can't wait for the writeup.  Any plans to add pump-action?
 
My biggest complaint with the earlier revisions is that the stock is very wobbly and easy to twist.  It could add a lot of stability to the stock if there were a third support extending diagonally from the bottom of the pistol grip to the bottom of the butt plate.  JLego's plusbow variants all have something along those lines and their stocks are solid as a rock. 


Seconded. Mine is a Slug original with a wood thumbhole stock added which achieves the same effect, and looks really good.
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#7 CaptainSlug

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Posted 30 June 2016 - 03:37 PM

Pump-action should be a pretty easy attachment since the functional parts are narrower than both plunger tubes.

 

To strengthen the stock it may be best to break in into two pieces so that it becomes an angle bracket. That would make a third attachment out of 1/2" rod capable of reaching the heel of the grip.

bow3_003.jpg

Thoughts?


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#8 DjOnslaught

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Posted 30 June 2016 - 03:44 PM

Pump-action should be a pretty easy attachment since the functional parts are narrower than both plunger tubes.
 
To strengthen the stock it may be best to break in into two pieces so that it becomes an angle bracket. That would make a third attachment out of 1/2" rod capable of reaching the heel of the grip.
bow3_003.jpg
Thoughts?


Definitely looks very stable and even gives it my favorite type of stock.
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#9 Langley

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Posted 30 June 2016 - 03:48 PM

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Yeah, that looks great.  I'd probably want to extend that third rod all the way to the front of the grip so it can be attached to it at more than one point.


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#10 CaptainSlug

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Posted 30 June 2016 - 04:04 PM

Will do some more tweaking to this later tonight. I'll be building the second prototype this weekend.

bow3_004.jpg


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#11 Meaker VI

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Posted 30 June 2016 - 04:19 PM

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Do you even need the endcap? Wouldn't sandwich plates work just as well? Side-drilling these thin sheets is always a bear.


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#12 CaptainSlug

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Posted 30 June 2016 - 07:12 PM

Good point

bow3_005.jpg

 

Pump-Action concept based on an ABS 2" Drain Waste wye fitting.

 

bow3_006.jpg


Edited by CaptainSlug, 01 July 2016 - 08:40 PM.

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#13 CaptainSlug

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Posted 04 July 2016 - 07:33 PM

The new stock layout is EXTREMELY SOLID. So thanks to everyone for the feedback.

 

bow3_c26.jpg

 

Write-up is finished. First post has been edited to include the link. The partlist is in .xls format so that it's much easier to copy-paste the part #s and quantities into the McMaster-Carr order form.

 

http://captainslug.com/plusbow3.html

 

I'll have the optional section for the Pump-Action parts added later this week.

 

The full draw-length K26 plunger tube is performing at absolutely asinine levels and I need to do a range test for it soon.


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#14 CaliforniaPants

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Posted 04 July 2016 - 07:49 PM

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the most exciting part of this is getting away from nylon rod. why the switch away from the handle with a trigger guard? was I the only one who liked that?


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#15 CaptainSlug

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Posted 04 July 2016 - 07:53 PM

the most exciting part of this is getting away from nylon rod. why the switch away from the handle with a trigger guard? was I the only one who liked that?

There's really no cost difference between Nylon and Delrin and Delrin is just easier to work with, so I moved to it the last time I made a batch of plusbows to sell. It's also possible to use fiberglass rod (which I did for the second prototype shown here because I ran out of Delrin) but it's a more fussy material to work with. It's also easy to strip out any threads you add to it if you're not careful.

 

One of the design goals was to avoid internal cutouts, so a trigger guard part would typically require such a cut. You are welcome to add any extra parts you want given that you will have a third or a fourth or a sheet of polycarbonate left over after making one of these.


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#16 The2ndBluesBro

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Posted 04 July 2016 - 09:10 PM

This is awesome and I will definitely consider building one. Could the grip pieces be HDPE?
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#17 CaptainSlug

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Posted 04 July 2016 - 09:58 PM

This is awesome and I will definitely consider building one. Could the grip pieces be HDPE?

The side panels of the grip as well as the plates for the stock can be any material really since they have nothing but through-holes. The following pieces may need to be Polycarbonate or Delrin/Acetal since you have to add a thread to them.

 

Frame1, Frame2, CatchGuide, and Pcross2(either size)

 

If you ran into any issues with other materials external reinforcement of the catch assembly could be done with a sturdier material as well.


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#18 DjOnslaught

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Posted 05 July 2016 - 08:13 AM

That new stock looks simply awesome, I like the pump action possibility also.
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#19 CaptainSlug

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Posted 05 July 2016 - 03:48 PM

It would appear that the upper stock rod is completely redundant, or at the very least structurally unimportant. This setup is still very sturdy. The other option is to do away with or trim out the middle stock rod.

bow3_008.jpg

Hooray triangles!


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#20 Draconis

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Posted 06 July 2016 - 01:27 AM

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It would appear that the upper stock rod is completely redundant, or at the very least structurally unimportant. This setup is still very sturdy.

 

Yeah, if the upper rod is removed, the middle rod simply becomes a pivot point, and the lower a tension member, thus the whole thing is a cantilevered beam.


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#21 The2ndBluesBro

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Posted 06 July 2016 - 09:25 AM

It's nice to see improvements on an old design, but it seems like this revision has forsaken the original intent of the +bow (lookalike crossbow) and even the cool + cutout on the side (always thought that was a nice touch, you should incorporate that somewhere on this blaster, although maybe in a different way to avoid internal cuts). The catch and priming mechanism are the only things this has in common with the plusbow. Great design, though. It's definitely nice to see huge leaps of progress on old designs. Maybe name it something different, though, since it comes off as such.
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#22 CaptainSlug

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Posted 06 July 2016 - 11:38 AM

The "original intent" was to achieve similar (or better) performance than a stage 3 modified Crossbow. And for it to not simply be a replica, but rather a war-serviceable and dependable primary. That was something only a few people modifying Crossbows could claim at the time Because that blaster had the ergonomics in spades, but was very lacking in structure and durability. A perfectly made "Stage 3" Crossbow goes so far beyond a modification that it borders on being a homemade. So the thought was to just start from scratch.

 

Every other criteria added or removed are things that are ancillary to that core premise of providing wider access to what an ever-increasingly rare primary afforded in terms of function. What the plusbow REALLY offered was a ridiculously overpowered spring that was widely available and the basic platform of the plusbow took advantage of that spring. It's much easier to dial performance back or compromise it than it is to edge it a little further forward. The plusbow would not have a reputation without the K26 spring, though AR-15 recoil buffer springs were an alternative that I used to develop the prototypes. They proved to be just a tad too heavy.

 

Rev.3 marries everything learned from Rev.1 and Rev.2 with a few things learned from the 2-11.

 

Rev.3 shares the same plunger, plunger tube, spring, draw length, and control layout dimensions of the prior two versions. The stronger plunger tube negates the need for the side plates, which offered some advantages (namely an integration rail) but had plenty of draw backs as well (fussiest parts to make, easiest parts to break).

 

Rev.3 isn't the only fish in the sea as there are plenty of other platforms available now. Homemades have come a very long way in the past 10 years.


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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#23 CaptainSlug

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Posted 12 July 2016 - 07:31 PM

It took a while for the fitting to show up, but the pump-action grip is done and works GREAT.

bow3_010.jpg

 

The DWV fitting fits over the plunger tube much better than expected so the polycarbonate piece doesn't have to be cut to fit as precisely. The templates for the parts are already included in the set. All you have to do is make two extra delrin rods.

bow3_011.jpg


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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#24 Snoop Doggy doge

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Posted 12 July 2016 - 08:14 PM

That looks lit as fuck, can I see it at APOC?
Also, how well do those knex darts hop? 


 


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#25 CaptainSlug

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Posted 12 July 2016 - 08:21 PM

It will be my primary at APOC, so yes.

 

The darts in the hopper are the "Men Gun" darts which I bought through Amazon. They're dirt cheap and work fine through my "Knifty" hopper if you cut them down.

They're $10.66 shipped per 200.

https://www.amazon.c...l/dp/B01GJHF2BY

 

They fly reasonably straight so far, and they hurt less than stock streamlines. I need to evaluate their accuracy a bit more in comparison with felt slugs.


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