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Ideal air-flow characteristics for a 6-shot absolver?

Absolver

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#1 UnscrupulousModefiler

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Posted 27 August 2018 - 10:04 PM

Hi gang. Looking to make the tiniest 6-shot absolver shells possible (without resorting to 3D-printing just yet...), so wanting to understand things a bit better. I've read a whole bunch of posts here on how people have made theirs but it seems there's very little discussion of the physics of ideal airflow regarding absolvers specifically. There's heaps of info on how to best to get one dart to fire at a time (pretty straight-forward that...), but things get squirrelly once you split that air-flow and present it to multiple darts. Is there a discussion out there somewhere that might be relevant or am I just stuck with trial and error?

Relevant issues/things to try to address in the build:

  • Minimising dead-space and smoothing air-flow. (Obviously the less dead-space the better, but how important is flow at this scale, especially when it comes to the flow through the expansion/splitting chamber? I can easily fit a cone-shape to the end of the "seventh" tube in the centre of the chamber, but would the shape of the rest of the chamber affect dart velocities much? )
  • Expansion-chamber - volume and relative dimensions. (Is small best here or do you want the compressed air to expand a bit to achieve some sort of "velocity" before hitting the backs of the darts? Is there some sort of ideal relative distance between the rear of the expansion-chamber and the back of the darts to allow the air some elbow room to work on the them? Should the darts be packed right down to the expansion chamber (to reduce dead-space), or would having a bit of extra room in each tube behind the dart better focus the pressure?)
  • Barrel Material, Length and Tightness. Starting with 16mm OD electrical conduit (ideal ID for Elites etc). Strating experimental length will be = (length of one dart) + (diameter of one dart). The extra length here will be reamed out in the middle of the bundle and then capped to create the expansion chamber (so a six-lobbed cylinder three conduit-diameters across by about 12.5mm high)
  • Air Tank: I've got a BBBB and Lanard Big Salvo to play with. Salvo tanks would be ideal for overall compactness, but then there's an individual trigger/pilot valve to sort for each of them. Will initially be running a small 12v compressor with a pressure-switch to fill the tank but ideally want to transition to a SpeXBZ and HPA.

All this may be moot at this tiny scale... but any pointers gratefully recieved!


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#2 jaxmeh

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Posted 28 August 2018 - 01:32 PM

17/32nds brass might make for a better barrel material, as you'll be able to pack it more closely together with its thinner outer diameter. If you're just after 6 shots out of one shell and you don't mind messing with half darts, a three barrel absolver with each barrel double loaded might be an option to experiment with.
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#3 UnscrupulousModefiler

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Posted 28 August 2018 - 03:38 PM

17/32nds brass might make for a better barrel material, as you'll be able to pack it more closely together with its thinner outer diameter. If you're just after 6 shots out of one shell and you don't mind messing with half darts, a three barrel absolver with each barrel double loaded might be an option to experiment with.

Hey thanks for the advice :) I've given brass a shot (haha) but the expense is crippling (I want to make a LOT of these...) plus there's the danger of denting a barrel if dropped. The (NZ/OZ standard size) conduit's working for me as far as overall absolver diameter goes because of the convenient "shell" I'm using to fit everything in - plus it's reeeally cheap. PTEG is my next option to try because I want to get Mega darts in as an option too. It's more the length of the whole unit that I'm trying to minimise now, so major issues I'm looking to explore will be around ideal barrel length (is a longer barrel of any benifit in an absolver??) and expansion chamber modelling. There's a super-stubby six-shot Elite/four-shot Mega half-dart shell in the pipeline... I'll post a build-log once I get cracking trying a few things out.


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#4 jaxmeh

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Posted 28 August 2018 - 06:20 PM

I'd guess that given enough volume, longer barrels in an absolver would have the same effect as in a single shot: more velocity and a straighter trajectory. A shorter barrel might actually be beneficial, giving you a wider spread as the darts fishtail all over the place. I'd be interested to see what your results from actual tests show, I'm just theorizing here.
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#5 spencerak

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Posted 06 September 2018 - 08:34 PM

If you have salvo tanks and pumping isn't a factor as you plan to use a compressor, why not just have 2 tanks operating three barrels each that fire off of a single blast button? Also, I would make the barrels the length of the dart plus however much you need to be able to have a conical shape.


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