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GeckoSub Mirage Evo - And Adventures in 3D Printing Speargun Parts

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Firearm thinking transferred into speargun land does not work, the trigger pull on a pistol is working on the springs being used to drive the firing pin into a percussion cap in the cartridge case, not the full power of the gun which is going to drive the spear from the gun for a distance of several meters, maybe up to 10 meters on some “big banger” guns. Highly sensitive triggers have no place in speargun land, but light to pull triggers do, there is a difference.
 
Trigger Pull

That's very true and I noticed early on I have two very strong personal preferences; a neutral gun and a light trigger pull. On the Mirage build before this one, I had a nice and light pull but it was also short and thus a bit sensitive. I was fine with the latter - but only because I was very mindful of it and would not feel good about handing that gun over to a buddy without some explaining.

For this Evo-handled gun I could probably get used to a slightly stronger pull but the issue is if it is not consistent. Bear in mind, it is not like the pressure or spring force on a ø3mm pin - the strong pull of the Evo is caused by friction from the line release. Which probably means it will vary depending on how taught the line is - and the trigger might not break consistently.

As for whether the stock Evo trigger is very shallow I will have to backtrack a little. I remembered I don't have a stock Evo barrel in the gun nor a stock piston and while I assume the sear sits at the same height in both the stock Evo barrel and the Predathor barrel I am using the UBL piston tail has a different geometry so it was wrong of my to try to conclude on the length of the trigger pull of a stock Evo. I will let you do that;-)

In reg. to my mongrel gun, I will start working on the trigger in a day or two. Right now, it might break before letting go of the line release which would need to be rectified, too.

BTW, the new tail end on the Evo piston might not be as rounded as we fear. I snapped a pic of it and will share it later.
 
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In the short term take the side line release out and try the gun without it. Side line releases can cause many problems unless they are powered by the gun, but that can cause a whole new bunch of problems. Mares unwittingly gave out warnings when the line releases busted on their first “Cyrano Evo” guns, now to move the breakages elsewhere in the gun they made the line release lever finger out of metal!!
 
Reactions: Diving Gecko
Yeah, last minute I actually packed the magnetic Palengas line release, too. But then read through my notes from a previous trip where I concluded I didn't like it at all... I used to, for about one trip after which the magnet rusted away. I put in a new one but that one was too weak. And then I forgot all about it. I don't know if I can source any new magnets in time to use that line release as a backup (I have left China and is in Thailand now).
 
A short term fix is to place a thick rubber band on the gun with it going around the tank; a short cord tied to the gun runs under that band and passes through the line wrap loops and tucks back under the rubber band. When the gun shoots the shooting line wraps pull the cord from under the rubber band and then everything pulls away from there.

A line release explained to me by an old-timer in the sport and now passed on.
 
CamWing - 3D Printed
The very last project I managed to squeeze in before I left home on this long trip was to make a new CamWing (which is what I call the wing like contraption that holds an actioncam to my guns).

It came together quite fast and it could have been prettier, but the rendering looked like this:


For the printing, I had to really hurry it so the surface quality was not as great as I could have gotten it with more time. Also, I had to do a bit of sanding to make the wing part fit:



The wing slides into the collar on the sleeve and a retaining screw goes into a threaded bore in the middle of the collar:



The sleeve and collar were printed as separate parts but they mate very nicely and I expect the the structural epoxy glue to hold them firmly together.
The little "tube" with the angled cutback is to hold a small piece of bungee for breakaway rigging of the shooting line. The cutback is to make the front opening larger to make it easier to insert the bungee. I was waiting for some reamers that didn't arrive in time, so I will have to sand the inside of the bore.

With the underslung, dive bomber profile of the wing, the actioncam lens should end up right on the centerline of the reservoir:


All in all, not too bad for a half day job when I was busy doing a few other last minute jobs and packing for the trip, too;-)
Come to think about it - this is actually a product I would happily have bought years ago if anyone had bothered to make it, haha.

[EDIT]
Adding a few more pics:

74g in total. The wing itself could be slimmed down more as it is still quite beefy. Originally, I wanted to printed it as a totally hollow part with just a thin wall and then fill it up with the syntactic foam I make from epoxy and microballons - I can make that mix so light it floats. But I didn't have time for the extra step so decided to just print the whole thing. As it is now, it has a three perimeter wall thickness (each wall is 0.35mm so 1.05mm in total) and the internal webbing (infill) i 20%.

I am using a tripod adapter for the ActionCam instead of the regular slide on mount - the reason being that the narcissist in me, safety minded as he is, wants to be able to turn the camera to selfie mode. This should be safer than turning the gun around and having no idea where the dangerous end is pointed:

 
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Reactions: landshark sa and Nico66
Looks good, amazing what you can produce once you have the 3D model frame defined and the build-up sequences programmed for the printer. As rhe saying goes "looks like a bought one" and the slightly rough finish is not that apparent in the photos until you get in close.
 
Reactions: Diving Gecko
Trigger Pull - Part 2
Slowly getting into investigating this trigger - though I have no other gun to compare to here.
I will share some measurements here and perhaps some of it will be helpful to diagnose the trigger.

First thing I noticed is that the sheer distance the trigger itself can move in the handle before it hits plastic at either end seems to be a bit short? But as said, I can't really compare:



So, measuring at the middle of the trigger the max travel is about 3mm. I have a feeling other serially produced Italian/French guns are quite a lot more? Either way, to me it feels a tad short for a gun that is supposed to be for the "masses".

I actually did order the Evo piston just to check it out and did some quick measurements before I left home (I didn't bring it with me as it wouldn't work in the UBL muzzle):



The measurements for my UBL piston are:



Sadly, I don't have the vertical offset of the trigger axis in the barrel - I could have measured it precisely with an indicator at home but not here (and again, I don't have a stock Evo barrel in this gun, I am assuming they use the same off set and sear as most other guns).

A while back I did measure and model a run of the mill trigger sear (a Mares one I think but as far as I can tell Seac and Salvi are exactly the same):




Perhaps if someone could measure the tail geometry on a regular Mares Sten piston and get us the vertical offset in the barrel of where the trigger sits, then @popgun pete could do a trigger analysis on the Evo? Perhaps the tail is fatter on these pistons?

P.S.
I didn't go over the shape of the Evo mushroom tail in detail when I shot those pics but reading Pete's comments, I think it's luckily not that bad. Here's a crop of the same image as above - I think the lip is not really as rounded as Mares let us believe. It looks to be as "sharp" as other pistons and I guess that' a good thing:
 
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Air Transfer Bore Sizes/Power Regulator Bulkhead - A Standard To Be Found? (updated repost)
(My previous post om the Air Transfer Bore sizes was too old to edit, so I will just edit/update the info with the latest findings in this post)

List of measured bulkheads:
  • Seac Hunter is 7mm (no pics, though)
  • Mares Mirage is 7mm (measured by inserting "mandrels")
  • Mares Sten (newest version - bought around 2014) is measured at 7mm (pics attached)
If I was to hazard a somewhat educated guess right now, I'd definitely say the old "standard" is 7mm (not 6mm like Mares claimed in their Evo promotional video).
Would be fun to have the measurement on an Cressi in there, too but I don't own any Cressi guns, and possibly an older Sten.

Here are the pics of the Sten 13mm bulkhead (note the cut out for added clearance for the plug as it retracts towards the handle):




While the bore is ø7mm there may or may not be some airflow restriction from the walls of the front of the bulkhead:
 
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I suspect that the “Cyrano Evo” (black and orange version) did have a rounded edge on the mushroom head in the fore-aft direction and once the guns started relentlessly busting plastic line release levers they hurriedly changed it to what you see now. They may have got rid of the pre-tilt on the sear lever as well because what made for a "sensitive trigger" created an unreliable one as to just when it would actually release. The move to a metal line release lever may have accompanied these detail changes as any early and unpredictable piston release from the sear lever with a metal line release lever would bust the plastic pivot support section in the grip handle molding which would be an absolute disaster.

Below you can see the diagrams that I did once I got my hands on the "Cyrano Evo" schematic parts diagram, a diagram that Mares was very reluctant to release!


 
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Reactions: Diving Gecko
I am wondering if part of the pre-tilt could a bigger tail on the Evo Pistons? Assuming the sear geometry and offset in the barrel is the same?


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Diving Gecko said:
I am wondering if part of the pre-tilt could a bigger tail on the Evo Pistons? Assuming the sear geometry and offset in the barrel is the same?


Sent from my iPhone using Tapatalk
Click to expand...
Well whatever created the tilt on what is in essence a flattened out single-piece trigger was the height of stupidity and to sell guns like that and put a trigger adjuster screw in there to compound the issue was absolutely crazy. No wonder they wanted to sit on that diagram and keep people guessing while they figured out how to save their bacon.

Another aspect that I nearly forgot was the much vaunted fore-aft adjustable trigger, Mares got rid of that in a flash once they found out that they had big problems. How-to get rid of it gracefully (?), well just introduce a new metal one instead.
 
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Here is Mares original diagram that got out and was seized upon by gun analysts, all I did here was add the English annotation.

This is my corrected version, but you can see that the piston tail shank is probably too fat for this version to latch as I left the piston unchanged, only replacing it later diagrammatically in yet another diagram.
 
A diagram is worth a thousand words!

Then angry customers start hitting their phones and complaining to the company!
 
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Trigger Pull - Part 3 (The Line Release)
I mentioned that the trigger pull in a dry test went from about 700g with no load on the line release to a whopping 2.5kg with three wraps at, what I judge to be, normal rigging loads. I find that quite silly to be honest...

A few pics of how the line release and trigger interacts:


It's amazing how much friction there can be between two (unpolished) molded, stainless parts. Also, I am not side the side pressure helps as it does press the ends of the trigger into the plastic walls of the handle (though SS to plastic probably has less friction).

I set about polishing the mating areas and the trigger sear - I brought the polishing paste with me for the same reason:


Just from feel, it seems like the trigger pull is a lot smoother already. I will try to measure it another day for better comparison but I think I might just get away with using this line release. And I will even try having the spring in because it does A). reset the line release (which I would otherwise often forget and that's frustrating as you would need to press the trigger to do, so you might have to shoot and reload if you forget) and B). add a tiny bit of force possibly reducing the friction in the trigger.
On the first dive in Indo, I will ask my friend to shoot some high speed video of how the line comes off of the release and then we can see if the spring is too strong (we have done that before in a pool with other guns).

I have a long list of tiny things I need to do and one big project; the custom grip. The latter is quite daunting and takes 3-4 days so I might just do a Polymorph/Shapelock grip for now...
 
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Then I fixed everything for the "Mirage Evo", got rid of the sear lever pre-tilt and changed the piston tail.
 
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