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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.
What would you know about physics, unlike you I trained as a Physicist, with tertiary qualifications and probably have forgotten more about physics than you will ever know. So maybe you can just POQ, which means "pass on quietly" as we have absolutely nothing to learn from you. And I suspect so will your colleagues on apox.ru who are just starting to wake up to you as one who keeps his place solely by being a pal of the moderator who seems unwilling to throw you out.
 
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I would appreciate if this thread was A). kept in English and B). does not become about Vlanik guns and finally C). kept about guns that are loaded in multi stages.

That said, the more I think about it the less piston size/barrel size matters. We should talk loading force. 31-33kgf is probably the highest force that I can personally load and judging from my last trip, it just won't be enough force to power 8-9mm shafts to the max. I would certainly think that 31kgf for a 9mm shaft is underpowered. Maybe ok for 7.5, but not even enough for 8mm.


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tromic said:
It would be even more powerful with 10 mm shaft on 40 bar: 386 J, 31 m/s initial speed.
Click to expand...

Your math is probably right, the only thing I can say is that in real life use 30kgf on my gun was definitely not enough for an 8mm shaft. Far from it.


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I agree, Delrin is great for this use and machines beautifully. I just have a dream of making a C4 style reservoir in CF and the structural demands would be less if I ran lower pressures but made up for it with a bigger diameter shooting barrel.


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tromic said:
Davide, what is the working stroke of your Mirage and what is the weight of the spear?
I would like to make calculation for your speargun too, for loading effort 31 kgf.
Click to expand...

Don't have those measurements right now but can probably get them tomorrow.
Do you define working stroke as from the trigger sear to front of muzzle or from the front of the piston to the back of the shock absorber?


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Until we see some Dogtooth Tuna shot with a Vlanik gun I suggest you just ignore him. Remember his largest gun is a 70 cm and no one will be shooting Tuna with one of those. Powerful guns like the hydropumper “Black Sea” guns shoot Tuna and don’t need a table of calculated data to demonstrate their capabilities. Old saying “figures do not lie, but liars can figure”, or more succinctly distort the facts by selective use of data. The annular notch shaft can snap off as it reduces the shaft cross–section and hence its strength where the fish imposes maximum load on it.
 
Here is an illustration of why the gun capability can be misleading if you don't know the characteristics and habits of the prey. Here a big catfish has been landed with an Aquatech 250 A model gun (rear handle). The catfish weighed 21 kg and was hit in the right spot as the hunter found himself on top of it.

Now I have a 50 cm or 500 version of this gun and it will not take down a fast swimming powerful fish unless hit in exactly the right spot and up close.

I purchased this gun new from Sergiy Kravchenko in 2000 and he told me all about the Vlanik gun and its limitations when we examined the state of the art in spearfishing there at that time. That is how I started on the RPS-3 speargun and set out to make myself an expert on it as Sergiy sent me a copy of the "Athlete-Submariner" article on the gun and since them I downloaded and read all copies of that magazine.

The above is a Tuna shot by Fernando Abella who did the test shooting of the "Black Sea" gun manufactured by Sergiy Kravchenko. He shot a World Record Tuna which snapped the breakaway head and then died and sunk, only to be recovered and weighed by fishermen the next day. It was identifiable by the tip left in it and if landed would have been the record. This is a smaller Tuna shot on a follow-up trip. Somehow I don't see the Vlanik gun in this league!
 
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Here is one of Vlanik's earlier guns and you can see that there is next to nothing to it. Bar a rear pump connection and lighter parts the modern version is just the same and is no miracle gun, in fact it is a little like a rod being blown out of a pressurized bottle with a sealing cork blocking the exit hole after the rod is gone. Spear travel in the gun is guided solely by the muzzle as the interior of the gun is empty bar the gas pumped into it.

Comparing this little gun with a "Mirage" is just a flight of fantasy by lake and river shooters who never go into the "Big Blue".
 
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This thread is about a secondary barrel pumping system speargun based on a speargun developed by Mares in the 1970's. It is not an exercise in speargun efficiency and the right of any other speargun designers to push their design on other people who have no interest in it. If this were the case then the Vlanik gun would be intruding on every speargun thread. We are not your friends and neither are we your enemies, but why should we consider a gun that has never participated in Bluewater hunting when the secondary pumping barrel system guns have done so? The talk of 12 mm diameter spears is rubbish and have you ever used such a gun with a 12 mm shaft? For a 9 mm shaft speargun a 12 mm would incur a 77% increase in spear mass. For big fast fish your pistonless gun is worthless and with the exception of Carp and Catfish you have no concept or experience of Bluewater hunting where fish of entirely greater capabilities are found, an area of expertise and experience that I and my colleagues here have. If you persist in these intrusions and gratuitous advice then I will request the moderator to delete unwelcome and irrelevant posts from this thread.

There is already a thread devoted to the Vlanik gun and any posts relevant to it should go there. Remember that many here have knowledge of guns from all over the planet, including all the guns from Russia, and you have no need to regale us about a gun that is well known to this forum

I suspect that no "Mirage" gun ever made it to Russia as "Athlete-Submariner" makes no mention of such a gun.
 
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Zahar,
You are misunderstanding Tomi. He is not attacking you. He just has the viewpoint that we don't need to think about temperatures and tries to explain his point. He even said clearly that he likes to simplify things whenever possible.
Not long ago, you yourself asked that we allow and respect that we can have different viewpoints, so please adhere to your own plea.

Lastly, a lot of us do not have English as out mother tongue and that can lead to misunderstandings. On that same note, I would like to pass a little bit of respectful advice: Your frequent use of exclamations marks makes it sound like you are either angry or yelling. Maybe exclamation marks are used widely in written Russian, but it is reserved for more extreme cases in English. Just wanted to mention that as I hope you are not sitting behind your keyboard yelling.
 
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I thought I asked you nicely to post in English? I spent so many hours taking pictures and writing my many, many posts on this thread. Whether you like the gun I made or the information I shared doesn't matter but the very least you could do would be to spend 10 secs to put your posts through Google Translate before you post.
 
Please Take Your Energy Formula To a New Thread
Guys, as much as I like the exchange of ideas, I don't think the thread I started about one particular gun and its systems is the right place to talk about energy formulas in general and the many different designs they could work on.
That talk deserves its own thread and this thread deserves not be the arena for the mudslinging that might follow. And even if you manage to keep it civilized, then its still better if all that information is in its own thread.

@tromic Please do me the favor of starting a new thread and repost the formula and Excel sheet over there.
I am grateful for the offer to do the math for my particular gun but we can do that at another time.
 
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I agree, such discussions are derails unless they pertain to the topic at hand. The energy stored in the weapon does not need to be calculated to know that it is effective. Any pneumatic gun that takes a large loading effort will have a powerful shot unless it has a large throttling effect in its interval airflow (or hydraulic losses at the muzzle outlet, which here we can forget). The “Mirage Evo” has no such problems and at higher cocked to shoot pressure will have a powerful shot. As for the spreadsheet I had a quick look and it seems OK as it is basically looking at start pressure, cocked pressure (from the compression ratio of the gun) and the working course of the piston. Energy losses to friction will be negligible. The approximation of the gun’s stored energy as a calculation of the area enclosed within a truncated tip triangle is well known and I have graphically demonstrated the negligible non linearity of the pressure gradient elsewhere. Adiabatic heating and cooling of the gas is irrelevant in a gun bathed in water which keeps the gun temperature constant, if you want to discuss that make it a separate topic. As for Vlanik's withdrawal of all his posts it is welcomed as his comments were of no use to this thread and he was only being disruptive and pushing his own barrow by reference to his own, and in this situation, irrelevant gun. A word of the moderator being summoned and he was gone.
 
Too many withdrawals will make a nonsense of this thread, I see that Zahar has also removed his post about a powerful gun with a 12 mm diameter spear in a pistonless gun format which was not very smart. If people do this then I will always use "quote" as that then imprisons their comments which cannot be completely retracted.
 
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@tromic I don't mind if we talk about the energy of this particular gun and perhaps a few others but we need to keep the comparisons in check, so we don't invite back the crazy thread drifting.

The working stroke for my gun should be 1190mm and the weight of the shaft is about 570g. My gun is still pressurized and I don't feel like loading it in my hotel room. But the numbers should be correct.

What I can tell you is that at 30 kgf (22 bar - about my max loading capability for a classic, single stage loading gun), there is just not enough power for an 8mm shaft. The gun feels sluggish and the shaft drop seems substantial. Judging from only hunting situations, the 8mm setup seemed to come alive around 40 kgf (28 bar) and fared even better at 45 kgf (33 bar).
I know a spearo who shoots his Predathor 100 at 34 kgf (25 bar and more than I can load) and he feels that's almost the minimum for an 8mm shaft.

Of course, rigging has a lot to say and while you can put e.g. 1.2mm mono on a gun for many Med purposes, if you are shooting doggies you start needing dyneema or cable. Actually, I am beginning to think that if you are hunting big doggies or GT, you need to turn your thinking a little upside down. Start with what rigging is needed to keep a big fish from just trashing and cutting it. That might be 1.7-1.9mm dyneema or 1.7mm coated cable. But those need a fairly substantial mass of a shaft to "carry" them without losing too much power too fast - which then leads to how powerful a gun you need to power up that shaft. You could also start with what mass of shaft is needed to ensure proper penetration on a thick bodied strong fish combined with the rigging, but again those things will drive your choice of size and power needs of the gun. This is why I am thinking my next "big" gun needs to be able to fully power an 8.5mm, 150cm shaft. I feel that will give enough mass to rig it with strong line and still have enough penetration on the bigger doggies - except for perhaps the monsters.
 
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Vlanik said:
View attachment 53806
Click to expand...

Guys, please ignore Vlanik's post as I have previously asked him to post in English so we don't have to do the translations for him. That goes for spreadsheets as well. I find it disrespectful that he can't be bothered doing his own translations so why should we keep doing them for him?

Actually, 8 years ago, the moderators even explained to him that if he doesn't post in English they can't monitor his posts and as such, they can't do their jobs and it seemed to help for a while as he did start posting in English. Since then, it seems he has decided he can't be bothered.

[EDIT] For possibly the 10th time in this thread Vlanik publishes a posts, actually two, and then deletes it all soon after. A waste of time for him and us. If you insist on having something worthwhile to add, then say it (in English). If Vlanik finally figured out that we are predominantly talking about guns that can be loaded at higher than normal pressures (multi stage loading for lack of a better term), then thanks. If he took them down to translate them, then even better.
That said, I don't mind comparing to a "normally loaded" gun like a Vlanikgun, which is exactly why I have included the 30kgf value in my previous post which is about what I can load such a gun at. But unless his posts are in English, I have decided not to read them.
 
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I suppose you already did some calculations using the excel file I attached. To me it is just a useful tool so I can make some comparationes.
Initial speed of 36 m/s for your data 1190mm/570g at 22 bar is nice, but the problem is that it decreases very soon with the distance. How soon it depends on ringing (kind and thickeners of the line, knots...) and hydrodynamic properties of the spear (cross section and shape of the slider and the tip of the spear)
I had exactly the same impression as you when for the first time shot may Cyrano 850 using original factory equipped black line and the tuna shape slider. The gun felt sluggish and the shaft drop seemed substantial. I was very disappointed! It is obvious that for your practice the initial speed of the shaft should be higher, maybe more than 40 m/s and that you need a thicker shaft, 8.5 mm.
 
Mathematical models are useful, but are only as good as the assumptions made in them and whether any significant factors have been left out. For spearguns they are not really worth worrying about as the friction elements have to be estimated or obtained from empirical experiments. If you are going to do the latter then you may as well build a gun and shoot it. Obsessing over mathematical analysis on something simple such as a speargun is not very rewarding as at the end of the day you just want to shoot fish with it. The mathematical model may produce results not in accord with reality, but may have some use in analyzing the reason for performance changes. My advice is don’t waste your time on what is a distraction. As a professional scientist and engineer I have used mathematical models, but bar the pressure effects and energy storage calculations I would not bother doing them for spearguns, particularly as spear flight and line drag also have to be considered.
 
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For me, it was just a chance to give Tromic a bit of input on how a theoretical energy value would fare in a real world hunting scenario. Also, I don't mind knowing myself.
But yeah, ideally we would have impact testing in a pool that could be correlated with the math.
But then again, once the gun is built and works the math matters less[emoji4]


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