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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.
It can take a long time to get an up-to-date response or contact with relevant users.
I can understand you wanting to avoid changing chucks. On my lathe changing to the four jaw chuck is a "test your strength here" moment as you hold the very heavy chuck cupped in your hand while turning the spindle to thread the chuck onto it by pulling on the drive belt with the other hand. Of course once the thread is started then you can just turn the chuck by hand to tighten it up on the spindle as you are no longer supporting the weight of the chuck.

The new gun parts are looking good and I look forward to seeing the gun even if you just push it together without the body “O” rings fitted.
 

If you swap your chuck around often, it might be worth making a chuck "nest" like this:


From my fave youtube machinist:
 
popgun pete said:
[...]
The new gun parts are looking good and I look forward to seeing the gun even if you just push it together without the body “O” rings fitted.
Click to expand...

At the end of the day, there wont be that much physical evidence to show for the weeks of work. Basically just the nose cone and the bulkhead. And perhaps one small mod to the handle but I will snap some pics of all the parts when I have them
 
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A Correction
I am quoting two statements I made myself way back when in post 54 and 57 to clear up a mistake I made. It's about how the check valves are made and whether o-rings skew or not and why. In my first version, I didn't have a step/shoulder to keep the o-ring on:

Diving Gecko said:
[...]
There a few unknowns, such as will the o-ring in the valve stay put when the air rushes past it or can it move enough to get skewed. Judging from e.g. the pump inlet valves, it doesn't seem to be a real world problem.
[...]
Click to expand...

(I italicized the offending statement;-))

So, back then I thought the pump inlet valves didn't have a step to hold the o-ring captive but just relied on the strong spring force. I was wrong, the pump inlet valve does indeed have a captive o-ring design. The plastic insert protrudes all the way to the o-ring and provides the shoulder for the o-ring to sit on.
As such, both the inlet valves and the check valve in the original Mirage bulkhead have a means to keep the o-rings from being blown down the bore.

P.S.
Reading through the older posts is interesting to me - I put so much info in there as I use these threads as a kind of notebook. E.g. I can now see that I intended not to machine the bores of the check valves at all. For sure, I need to machine the shooting barrel bore in the bulkhead and the air transfer bore but back then I felt it wouldn't be necessary for the check valves. That might be so but I guess I forgot about that as I have since undersized the bores for the printing. I think that's alright, it will just cost me a little more time on the lathe.
Also, my 3D printer seems a little bit less smooth these days and doesn't produce as nice a surface as before. I think it needs a bit of a rebuild but I'd rather not do that now.
 
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Vacuum Resin Impregnation Reservoir
I have said this too many times but for a tinkerer, China is close to heaven - I spent four bucks and got myself one meter of plexiglass tube shipped to the door.
One thing that bugged me with the vacuum resin impregnation method was how much resin I would use and I couldn't find disposable cups small enough so I just made this:


There's about 2mm of space around the extremities of the nose cone. I could model and print some shaped blocks to take up even more space but for now, this is good enough.
Some of these plastics float in epoxy, hence the nut to keep the part under control.

It took about 20-30mins to model it and a bit more than an hour to print.
 
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Go Figure... (Best Print Settings So Far)
I have been wanting to test some slimmer o-rings for the main seals for the reservoir to the nose cone, bulkhead and handle. Normally, these are app. 2.15mm section width and are, as far as I know, a non-standard. I have had luck with some off-the-shellf 2.2mm ones for stock guns but even those are not that easy to get your hands on.
To work around this, my own parts have been designed to use more commonly available 2.0mm rings. But then I thought I should check out going all the way down to 1.5mm as that would help with the wall thickness issues in certain spots.

I drew and printed a very simple "nose cone" for my pressure tester:


I expected it to leak from a lot of microscopic pores but I would be OK with that as long as could tell if the o-ring seal itself was failing catastrophically.
So, I took the assembled test tank up to +30 bar and dropped it in the sink and go figure, it didn't leak...

(The black parts at the front of the nose are just spacers as the thread doesn't run that long).

Each time I take a reading I loose about a bar of pressure, so here's some pics after I took a few readings over the course of a day:


Maybe this is a little mystery gift to me here on the last day of the year;-)

Mystery or not, I do have some thoughtt on why this nose cone worked out better and it has to do a bit with the part itself but also with how I have tweaked my printing settings over the last few months:
  • Walls are thicker being that the barrel is centered and there's no pumping barrel in this part so there's more meat in some critical areas of the part
  • I printed at higher temps with zero fan cooling which fuses the layers better - at the cost of fine detail and overhang printing capability
  • I turned retractions off as it's hard to find the right balance where they don't either leave blobs or, worse, unfilled spots
  • I varied the angle of the infill layers between 0, 90, 45, -45 degrees through the print which helps avoid spots in the same place that doesn't get filled in
  • I increased the overlap slightly between the infill lines and the perimeters
  • I printed with a relatively high number of perimeters giving a quite thick, unbroken "sleeve" around the barrel and on the outer wall of the part
  • I used a higher layer height than normally leading to less layers in the part - less layers should mean less opportunities for bad fusing
Now, I don't know if this would work on the "real" Evo Mirage parts as they necessarily have quite thin walls in certain areas. But for simpler parts, there might be light at the end of the 3D printing tunnel.

(I'll take it back up to 30ish bar and leave it overnight to see if anything changes).

Happy New Year
 
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It all seems to be going very well, here the New Year is about 15 minutes away, so Happy New Year to you and others at Deeper Blue as we move into 2019!
 
[QUOTE = "Diving Gecko, должность: 982649, участник: 17977"]

Мне все еще нужен пистолет для следующей поездки, но вместо 3D Mirage я потороплюсь и поработаю над чем-то намного более простым, но потенциально все еще довольно мощным.
[/ QUOTE] Это правильное решение ...
 

Via Google Translate, Vlanik told me I should go for the simple option and leave the Mirage alone for now; which I was going to do a week back-)
But I really do like these challenges so while I might be making the wrong decision I am now back to trying to finish this within the next week, haha.

That said, I am also hedging my bets. Besides bringing my polespear and possibly my optimized Pathos 100, I will be traveling with two other spearos one of whom is a speargun dealer, so I think we will have enough gear between us in case my Evo Mirage dies. Also, if it is just the Mirage loading system that craps out, I can pull it out, plug the loading barrel bore in the nose cone and use the gun as a regular Sten-type gun.
 
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Almost There
Managed a bit of progress.
Yesterday I glued together the two-part bulkhead using some very heavy duty structural epoxy glue. It's overkill but it's just so much easier to work with this glue than mix up my own little batches for every little job like this:


After the fancy glue, I used some local Loctite ripoff super glue and activator (I think they even use Loctite's product numbers) to tack the two parts in place to avoid them moving while the epoxy glue was curing.
BTW, I can't believe I never knew of super glue activators- it's a cool little thing as sometimes even super glue doesn't set right away, but with the activator it does:


Today, after letting the epoxy cure, I cleaned the glue seam up on the lathe (though the next two pics are "before pics"):


Previously, I mentioned how the retraction settings on the printer can have a huge influence on how porous the part becomes. Here's a prime example of how bad it can be:


I noticed it straight off the printer but didn't feel like printing new parts as in this location (rear of the main seal) it doesn't matter whether it leaks or not. Also, the front face is more solid and I will also be vacuum impregnating these. After all, the bulkhead can leak a little bit as I mostly just need it to hold air during the "Mirage Loading" session which is about 30 secs. Though ideally it doesn't leak because it's quite nice when you can e.g. take a low power shot before getting into the boat to change spots and then when you drop back in, the loading effort is really easy as you don't have to do the full pre-pumping procedure. I have definitely gotten fish this way - being the first to load up at a new spot, when curious species have swung by briefly to check us out.

After I finished this bulkhead I went to work on the shooting barrel. Back in post #72 I had realized how the barrel doesn't line up in the handle so I had to move the trigger 4mm forward (and chop a few mm off of the back). It is for exactly these type of operations that I got the lathe and it's super rewarding to be able to do this myself. That said, I was zoning out a bit and managed to make some of the cuts on the wrong barrel, haha (I had used my shorter Predathor 85 barrel for lining up the cuts on the lathe then forgotten to swap it out for the longer one...). Anyways, a few pics:

In the one above I am extending the cutout for the trigger sear towards the front (as the trigger sear will be moved that way).

In the next pic, I am drilling the new hole for the trigger sear pin:


The jig to hold the barrel is obviously 3D printed which worked alright since the barrel is just aluminum. I don't think this would work with a steel barrel. The other end of this long barrel is supported by a camera tripod. BTW, for drilling off center into the curved surface of the barrel, the trick is not to use a regular drill bit but instead end mills.

This is the result and the barrel now lines up perfectly in the handle again:


I think I might be able to assemble the gun in a day or two. For that to happen, I need to epoxy impregnate the new bulkhead and nose cone, make a pumping barrel (which is more simple this time as I don't need to machine the recesses for the "sleeve valve"). Oh, I am getting ahead of myself, I still have a few more cuts to machine on the nose cone but waiting for a 13mm end mill which should arrive tomorrow.
 
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Don't bother listening to Vlanik, he is always trying to promote his gun by showing a pile of dead fish or disparaging others. Marking every corner he is now trying it here. He probably has never laid his hands on a "Mirage", or even shot one, and here he is out of his depth, unlike the pond he "rules" in Russia.

Nice job on the bulkheads and main barrel. How well do the breathing ports line up with the Cyrano handle? One of the reasons for using the Cyrano Evo handle is Mares provided four ports for a barrel tube that is set high in the handle and makes the usual top port unavailable. Just mentioning as a "refresher" for those who came in late and have not read right back to the beginning of this thread.
 
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I have met some good Russians on my travels - I don't think "blunt" covers it but mostly, it's just the tone of voice and to a Dane, it's not too far off the brutal honesty we like to say we can deal with. As for this specific one of Vlanik's comments, I think it was well meant. He certainly has a point in that often times, simpler is better - but he doesn't know my obsession as well as the rest of you guys, haha.
To me a lot of the fun is in the project itself. If it works and if I take some fish on this gun, I will be immensely satisfied.
Also, I regard these various projects as stepping stones to what will hopefully be a more scratch-built gun in the future. And they help me pass time and learn new things along the way
 
Looking at the LG-Sub they use fancy multi-axis milling machines to generate all their parts, both metal and plastic, and could probably make a "Mirage" type gun if they wanted to. Their "Revolution" is pretty simple and the most interesting thing about it is how its made rather than being anything other than an optimized design with high precision, and expensively made, parts. By the way I know plenty of Russians and Ukrainians and have been designing guns with them for years, including making changes to the "Taimen" to get around some potential corrosion problems.
 
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I certainly agree. The Mirage is not that advanced when compared to e.g. hydropneumatics and so on. Now that I have endlessly taken mine apart and measured every little nook and cranny of the parts, I think it would be quite easy to make one better from scratch and get rid of the child's deceases Mares never really fully cured. If I can make one on cheap 3D printer and a hobby lathe for sure pros with proper CNC machines can make them.

The gun I have in mind to build one day will likely have a "Mirage" system incorporated. Either with a small pump with a lever, or Mares style using the shaft. One thing to work on would be to make larger air transfer bores but that is connected to my comment about testing how much of an impact the bulkhead has on airflow and power output. In my view, the next step up from a Mirage is a hydrogun, but then we are talking a whole different ball game in terms of operating pressures and that's not something I am confident with yet, if I ever will be.
 
[QUOTE = "Diving Gecko, должность: 982776, участник: 17977"] - но он не знает моей одержимости, ребята [/ QUOTE]
Твоей одержимости можно только позавидовать...А в целом проведена огромная и полезная работа... Но всему есть конечная цена...
 
The general principle in user terms of loading via a small bore barrel and shooting via a larger bore barrel is what the Mares “Mirage” does and that was also used in the auxiliary hydropump guns such as the Aquatech "Black Sea" gun. The difference is the “Mirage” pumping action is a gas transport shuttle pumping one volume of the gun down while pumping another volume up, in the hydropneumatic guns it is incrementally moving water into the gun that will be used to push the spear out of the gun. The smaller pumping bore lowers the force required (F= P x A), but increases the number of strokes, whereas loading in the main barrel involves only one long stroke. Excluding losses due to friction in the pumps the amount of the work done is the same whichever way the gun is loaded, either by conventional muzzle loading or by pumping the small bore barrel, but the effort is spaced out in manageable chunks rather than one big effort when you use a pump. That is all there is to it, but the “Mirage “does it in a very compact design with no need for a pump handle as the “handle” is the loader and the pump rod is the spear.

In the hydropump gun world there have been many variations of where to locate the pump, but inside the grip handle has been the most common. A lot of gun ideas and developments are described in the Russian magazine “Athlete-Submariner” and I have looked at every issue of that magazine and where appropriate, read most of them. In terms of being advanced the "Mirage" is a more sophisticated gun than the hydropump guns which are not very efficient, but the "Mirage" gun's problems were trying to squeeze everything into the "Sten" envelope and have the gun pump down to zero with the pumping barrel. That required a tiny pre-chamber volume and in arranging that the designers neglected the gun’s internal airflow or breathing by using a similar length gate as is used in the “Sten”, whereas it should be nearly twice as long, but that would not have fitted in the length of handle available in reach of the user’s thumb.
 
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This hydropump gun by Vadim has made use of the hydropump handle as a reel mount, but while very powerful all these guns are sinkers after the shot. A "Mirage" should be nearly as powerful, but the limiting factor is the spear when used as a pump rod as the spears are relatively long. That means the spear can be bent if the pressure is too high even in the smallest ID pumping barrel that the spear can fit into. The hydropump guns use short pump rods, or if they are like the Italian Alcedo “Hydra” guns use a pump rod that is about the size of a thick needle. Hydropumps are generally water displacement pumps, same idea as sticking your finger into a brim full glass of water which makes the water overflow, only in the hydropump it is sent though a check valve into another section of the gun.

The big advantage of a "Mirage" is it is powerful (if made properly) and it floats after the shot. Hydropump guns can be made to float, but only after encasing them in lots of timber as the second gun demonstrates.



These hydropneumatic spearguns are in what I call the KABOOM class of underwater weapons, powerful spearguns which you shoot sparingly due to the long reload time, but pretty much guarantee a kill if you are on target. In the right circumstances it is like shooting fish in a barrel as the guns are deadly accurate once you get your eye in.
 
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Getting Close
We are down to the last little things before putting the gun together for the very first time.
So, here's a bit of a mixed bag update.

I had one final machining operation to do on the nose cone which was to take the pumping barrel bore up to 13mm. First, I used a reamer and just for the very end of the bore, I used an end mill to make a proper flat step for a steel or titanium washer to sit on to hold the piston in place:



Once the nose cone was done, it was time to make a pumping barrel of some 10x13mm alu tube. Originally, the Mirage uses a 10x14mm tube but I don't have room for that and I don't mind the weight reduction, either. It was a fairly easy job of just cutting some o-ring grooves at the front, cutting the tube to length and then chamfering the back:


I did a quick trial fit to make sure the pumping barrel was the right length (though the pics are of before I put the reservoir on):



The mechanics of the gun are almost done at this stage (just need o-ring grooves for the shooting barrel and a retaining ring in front of the bulkhead, but that's pretty easy work) so I went on to some epoxy work.
Normally, I kinda like working with epoxy but not when it is just using it to impregnate these parts. I guess it's because normally, I would be doing some carbon fiber composite or a handle where something more tangible comes out of it - but when it's impregnation, it's mostly just a mess...

But I had to do get it done, of course, and I took a few pics this time. Here's one of a bulkhead (I did two) sitting in the new reservoir:


I then dropped this fancy "jug" in the bigger vacuum chamber and turn the pump on for about 8 mins. The pic is from very early on as all those bubbles are not just from the voids in the bulkhead but mostly from the new printed "jug" which hasn't been resin-filled yet - and some of the bubbles are from the resin itself being degassed:


The bulkheads were only vacuum impregnated whereas the nose cone was first vac impregnated:


And then it was high pressure impregnated. First pic is from when I am taking it up to pressure - I stuck the pressure tank assembly in a small cardboard box to the left to contain the epoxy that would start seeping out:


And finally, here's a better pic showing how the high pressure pushes the epoxy through the porous nose cone:


I feel like this one leaked a bit more than the one I did a while back. Perhaps because I shaved off a lot more material to save some weight. Let's hope the epoxy will do its job and plug all the little pores, though.

After these two procedures, I spent about an hour cleaning up not only the bulkheads and nose cone but also the different tanks and reservoirs. It's a mess but with tons of tissue, frequent changing of gloves and a respirator on it's doable.

I think I will be able to assemble the gun tomorrow. I honestly don't know if I have gotten it right so I don't know what the odds are that it will work the first time, but fingers crossed.

It would be cool if there are no major hickups as I would really like to do a custom grip on the Evo handle, too and that takes 3-4 days, too.
 
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Great progress and a magnificent job, this is one of the best considered pneumatic speargun projects ever. The real pay-off will be when you use the pumping barrel and can feel the pressure progressively falling away in the rear of the gun. Transfer and insert the spear into the main barrel with very little effort, then the KABOOM moment when you pull the trigger for the first underwater shot and see the shaft rocket away in a blur of cavitation bubbles.
 
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