Evanix Rex reflex inserts for shroud
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Evanix Rex reflex inserts for shroud
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Topic: Evanix Rex reflex inserts for shroud (Read 3062 times))
Mr.P
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Posts: 1713
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Real Name: Marco
Evanix Rex reflex inserts for shroud
«
on:
October 31, 2022, 12:37:07 PM »
I’ve been enjoying my .357 evanix Rex, which is powerful and quiet compared to my previous foray into .357 airguns.
It still puts a hurt on my ears and I don’t like wearing protection if I can safely avoid it.
The Rex has a really large shroud with lots of volume but it is purely cosmetic and non-functional, and this pisses me off more than it should. I think it is a missed opportunity. I have a can I can put on the end but there are a few reasons I don’t like that solution either so I am going to try making the shroud into something functional, allowing air to expand back into. 3d printer makes it possible!
Problems to fix:
1) front bushing isn’t vented
2) shroud has a bunch of large holes drilled in it for looks rendering it useless
3) end cap isn’t contoured to shunt air backwards
So I am printing a vented barrel bushing, a long tube-like insert to nest in the bottom part of the shroud and block the holes, and a baffle for the small chamber at the end which I hope will strip and force air backwards.
The baffle I think can be improved - I will likely redesign that part.
Two pics attached, one of the parts in tinker cad and another of the shroud. Right now I’m just printing prototypes to test for a fit. I may try to incorporate some O-ring grooves to get better seals against the shroud in future iterations
My hope is to get more of a muffled report, not aiming for anything other than “shooter friendly”.
«
Last Edit: October 31, 2022, 12:40:14 PM by Mr.P
»
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All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
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Re: Evanix Rex reflex inserts for shroud
«
Reply #1 on:
November 01, 2022, 01:28:23 AM »
Marco,
Where does the barrel muzzle end relative to the shroud muzzle, stock?
There seems to be a lot of shroud volume ahead of the perforations. An internal sleeve to also shutter the perforations should add up to a huge reflex volume.
It looks like the shroud ID is large enough to make a smooth air stripper to reverse the air flow, and feed into the rear of the shroud.
«
Last Edit: November 01, 2022, 02:07:16 AM by subscriber
»
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Mr.P
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Posts: 1713
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Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #2 on:
November 01, 2022, 07:07:59 AM »
There is a small chamber at the end - about 33 mm between the end of the barrel and the Donnyfl end cap.
The first prototype print was effective fit well enough and my second iteration is printing. The report is greatly reduced by the reflex inserts, and the tank ping and mechanical / hammer sounds are now the most noticeable aspect of the report. Definitely did not expect it to be this effective because there is so little volume in front of the muzzle.
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All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
Mr.P
Expert
Posts: 1713
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Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #3 on:
November 01, 2022, 10:14:28 AM »
Meant to say in that last post that I am unsure of the ideal design for the baffle that sits in that 33mm space at then end.
Right now what I have is contoured / curved at the end of the baffle and the “stripper” is a short tube the pellet passes through. Not sure what the ideal design would be as there is not a lot of room.
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USA, NY
All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
Mr.P
Expert
Posts: 1713
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Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #4 on:
November 01, 2022, 01:08:12 PM »
I updated the design of the baffle and barrel bushing again to more effectively push air back into the shroud (or so I imagine). Here’s what they look like now:
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USA, NY
All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
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Re: Evanix Rex reflex inserts for shroud
«
Reply #5 on:
November 01, 2022, 05:19:44 PM »
Marco,
The initial uncorking of the projectile is what produces the sharpest "pop". Your Evanix probably has quite a significant muzzle pressure and volume. Your modification has provided room for that air to expand near the source (muzzle), and put a wall in the way of the pressure wave to reflect it back. Because the Evanix was objectionably loud, reducing the blast by half would bring noticeable relief; even if it is still very loud compared to a stock Beeman R7, or Benjamin Marauder.
The thinned out barrel support should offer better flow, but the sharp edges at the OD look flimsy. I have modelled one that maximizes flow area, without becoming too thin at the OD, because a picture is self explanatory.
As for the best configuration for an air stripper; that depends also on the rest of the system design. I have attached a cross section of a two stage reflex air stripper that is intended to smoothly guide the air in front of the barrel muzzle, round towards the rear shroud cavity. There are two stages to limit turbulence at the muzzle, yet provide lots of flow area via the second stripper. This is made possible because of the diameter of the device. For a smaller ID shroud, I would attempt only one such air stripper. The design can be FDM printed as the barrel support spokes also serve as printing "supports".
There are many configurations that all work well enough, so I would be arrogant to suggest that one approach is always better. A flat wall with a sharp edge hole works by stalling the air and converting its momentum to pressure. That pressure then feeds back into the rear of the shroud. A conical air stripper should reduce turbulence right at the baffle bore. If it is curved, it can be used to convert the air's forward momentum to rearward momentum more directly. Note that my air stripper design partitions and guides the air flow on the inside of the bend, so to speak.
As for the length of the "pipe" at each air stripper. The longer that is, the more effective at holding air back. But the greater the risk of the baffle bore "steering" the projectile. The latter effect can be reduced by increasing the baffle bore diameter. But, making something so much better than you have to back off another aspect to prevent it from being worse seems silly.
I generally don't make the parallel section of a baffle bore more than a caliber long,
or
the
bearing length
of the standard projectile. I make the
radial
baffle bore to projectile diameter clearance 1 mm for close baffles, and increase the gap for forward baffles, if there is any doubt about the barrel bore to baffle bore concentricity or parallelism. Or if the vibration in the system is significant on firing. As measured baffle bore is what matters, rather than just the CAD dimension.
Your purple front air stripper looks like it should work. If I am seeing it correctly, the walls look a bit thin at the leading edge. That may be because it is in "ghost view". I find viewing "solid" parts that are sectioned easier to understand.
The slanted red lines in the bottom image represent a thread for the barrel stud.
I am pretty sure you are having fun designing your parts. Else I would offer to design some bits for you to try out. For that, I would need some key dimensions.
«
Last Edit: November 01, 2022, 05:43:39 PM by subscriber
»
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Mr.P
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Posts: 1713
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Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #6 on:
November 01, 2022, 05:43:45 PM »
Subscriber, thanks for your input - greatly appreciated.
Your bushing design seems optimal - I may try that on the next iteration because the centering was off on the fin bushing and I can’t use it… tinkercad determines the center of concave shapes like the cross section of that fin bushing in a weird and unhelpful way that i didn’t notice until I printed.
Believe it or not the fin bushing is not flimsy, though I agree it looks like it in the picture. The fin’s edge is about a mm thick and I printed at 100% infill so it’s “Lego brick solid” and I would not want to step on it in bare feet in the middle of the night.
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All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
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Re: Evanix Rex reflex inserts for shroud
«
Reply #7 on:
November 01, 2022, 05:47:14 PM »
One mm is wide enough to be sturdy because of the taper. It looked like a knife edge to me in a previous image. I made the fins 2.5 mm thick and parallel, except for a 1 mm radius either side of the root.
I edited the above post, so you might have missed some statements I added later...
If you provide the OD, ID and length, I can attach such an STL here...
«
Last Edit: November 01, 2022, 05:49:21 PM by subscriber
»
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Re: Evanix Rex reflex inserts for shroud
«
Reply #8 on:
November 01, 2022, 07:45:58 PM »
Marco,
I have integrated the forward 33 mm long section with curved air stripper into my barrel support design. To make the part 3D printable with shorter bridged sections, I doubled the number of "spokes" and made them half as wide.
I assumed a number of dimensions, including a barrel/stud diameter of 18 mm. Please provide the correct dimensions and I will update the part. You can decide if you want to print it or not at your convenience.
The red lined image shows assumed dimensions. Please let me know what dimensions should be.
The part needs to stand on the printer platen, on its muzzle end, for printing so that the barrel support spokes act as printing supports.
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Mr.P
Expert
Posts: 1713
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Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #9 on:
November 01, 2022, 09:05:30 PM »
Hey there - that looks interesting.
The barrel is 14.5 mm diameter and my parts seem to print a little undersized so the parts should be 34mm diameter to fit well in the shroud.
33 mm from muzzle end to end of chamber.
My barrel bushings are fashioned like the one that came with the Rex - there is a 14.5 mm bore that the barrel slides into but for the last 3 mm it narrows to about 11 mm so the barrel stops and catches at the shoulder where the hole narrows. The bushing is 30mm long. It is press fit, no threads.
«
Last Edit: November 01, 2022, 09:07:51 PM by Mr.P
»
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USA, NY
All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
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Posts: 6811
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Re: Evanix Rex reflex inserts for shroud
«
Reply #10 on:
November 01, 2022, 09:09:20 PM »
Thanks, Marco
What is the length of the barrel channel? See image below
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Mr.P
Expert
Posts: 1713
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Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #11 on:
November 01, 2022, 09:17:25 PM »
27 mm, total length of part is 30mm
I don’t see any reason why the part is 30 mm and not 25 or 35 as it will center the barrel either way. I just went with the same size as the original
Also as you know the particulars of the “shoulder” don’t matter as long as there is some kind of stop to seat against.
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USA, NY
All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
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Posts: 6811
yes
Re: Evanix Rex reflex inserts for shroud
«
Reply #12 on:
November 01, 2022, 11:06:53 PM »
Updated part shown below, with STL print file attached (inside ZIP).
The total combined part length is 50 mm. The barrel seat is just over one diameter deep, using the 14.5 and 11 mm diameters provided. The barrel muzzle shoulder length to front face of part measures 33 mm.
For greater stability I extended the thin (1 mm) section of the 34 mm OD "casing" all the way to the rear of the part.
I could make a version where the 14.5 mm barrel socket tapers down to perhaps 14.45 mm, or any dimension you deem would take the slack out, without breaking anything.
Due to file size, I had to zip the STL.
Note print direction is a must...
For interest, the barrel muzzle face to leading air stripper cone face worked out to 21.25 mm. This is probably about a projectile length, or bearing length, depending on weight. A reasonable stand off distance, for the first air stripper that has to take the brunt of the blast.
«
Last Edit: November 01, 2022, 11:30:16 PM by subscriber
»
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Re: Evanix Rex reflex inserts for shroud
«
Reply #13 on:
November 02, 2022, 04:54:58 AM »
Version 2 of this part has a lightly longer airstripper cone, with a slightly sharper leading edge. The parallel bore is slightly longer now, at 9 mm. Also, the barrel muzzle face to cone face distance is 20 mm. If you have not yet started printing the first version, I recommend this version to try out first.
The difference is subtle, but closer to my original intent.
STL attached as a zip file.
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Re: Evanix Rex reflex inserts for shroud
«
Reply #14 on:
November 02, 2022, 05:36:01 AM »
Version 3 is just like version 2, with more radial space for the air to expand just after it leaves the barrel muzzle.
Zipped STL attached
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Mr.P
Expert
Posts: 1713
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Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #15 on:
November 02, 2022, 10:10:30 AM »
These look great - will get one on the printer today!
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USA, NY
All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
Mr.P
Expert
Posts: 1713
yes
Real Name: Marco
Re: Evanix Rex reflex inserts for shroud
«
Reply #16 on:
November 02, 2022, 12:01:09 PM »
In progress. For some reason with this print the skirt didn’t really stick to the bed I guess I need to adjust my Z offset. I don’t think this will affect the print in a meaningful way.
«
Last Edit: November 02, 2022, 12:19:50 PM by Mr.P
»
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USA, NY
All kinds of shooting is fun… I don’t care if it’s a gun, if it’s got a trigger on it it’s fun.
-Bob Munden
subscriber
GTA Senior Contributor
Posts: 6811
yes
Re: Evanix Rex reflex inserts for shroud
«
Reply #17 on:
November 02, 2022, 04:54:51 PM »
I get a strange satisfaction from seeing that thing "in the plastic", Marco! Hope it performs.
Now imagine adding an integrated nose to the part that contains another one or two baffle chambers, with the appropriate thread integrated into the OD. Or, one could use the thread adaptor to add nose section by screwing it on separately.
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Clicky
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Real Name: Phil
Re: Evanix Rex reflex inserts for shroud
«
Reply #18 on:
November 02, 2022, 05:28:11 PM »
I have a Rex-P in .357, same basic issue
I had been sketching out some ideas, but before I could do serious work on this, I bought a Bulldog. So the pistol has been side-lined for a while
My idea is based on getting rid of the inner shroud, outer shroud and making adapter rings to go over the existing shroud mount at the rear, while making from scratch the entire front mount
I purchased some steel tube that's almost the exact same OD as the Ronin I bought for this and was planning on having everything designed so that with the Ronin mounted, there would be no gaps or dips anywhere in the silhouette
I'd want some venting at the rear of the new tube, but otherwise no holes on that
I'll have to dig up the sketches I drew, but I think the front mount would be best with only three ribs, shaped for airflow
I have a stock Sidewinder X2 with some black Kodak PLA+, and I'm using Fusion360 & Cura
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Re: Evanix Rex reflex inserts for shroud
«
Reply #19 on:
November 02, 2022, 06:50:47 PM »
An integrated design enables optimization, Phil.
I am amused by shrouds with vents at the rear to let air out - even if so many respected experts swear by them. Any holes in the rear of the shroud (or LDC) that reduce the noise coming off the muzzle in a meaningful way, increase noise to the rear and sides, in a potentially annoying way. Otherwise there is no way that enough air could flow out the rear fast enough to make much of a difference at the muzzle end. A handful of tiny shroud holes work like racing stripes and coffee-can exhaust tips to make Civics faster...
The above is not aimed at you Phil, but at the experts that measure sound level at the muzzle to prove their shroud holes reduced report by full 2 dB. The ones that claim more than that don't measure at the shooters ear; for good reason. Now, if the shroud had two concentric tubes, spaced perhaps 5 mm apart, with the inner tube 50% perforated with 2 mm diameter holes; then the holes would be useful. So long as they don't vent to the outside.
Do not be discouraged by my rant. Experimentation is a major route to discovery. Thanks for sharing your plan.
«
Last Edit: November 02, 2022, 07:18:59 PM by subscriber
»
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Evanix Rex reflex inserts for shroud