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Infinitengines "Dreamair" pneumatic speargun

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.
ECK said:
Air rifle cannot use long thin shaft

Shaft airgun must have Line RETAINER SLAIDER
Click to expand...

The slider is no longer a drag issue if you use small hydro braking ones. My sliders from Dima are so tiny I would say they have less or the same drag as three sharkfins on a bandgun shaft (I don't use notched shafts). Also, if I have a very long airgun, I go up in shaft thickness anyways. My longest gun shoots a 145cm, 8mm shaft. I also have one that shoots 125cm x 7.5mm shafts. The idea to use long thin shafts is, I suspect, predominantly a Mediterranean preference and not one I share.

The potential advantages to the DreamAir is, as I see them:
- More familiarity for bandgun users
- You can use your own favorite shaft
- A better sightline than oleos
- Possibly a progressive force on the shaft as it is launched, which may lead to more stable shaft flight
- If Andreas is smart he puts in a very good roller trigger for the best possible trigger pull which would likely give more feel than an airgun trigger

So, the potential is there for a nice hybrid, but the big question is if the drum system is tangle-proof and how much power we get. If it has less or the same power as either a double banded bandgun or a well-optimized oleo, then to me it is not interesting. The fact that Andrea has had to add a pulley loader late in the development of the gun makes me a bit hesitant.
 
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ECK said:
Charging the "Dreamair Unreal" looks very uncomfortable for a long time. This is very similar to how he charged his Mirage Diving Gecko Can he tell how good it is?
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The Mirage loading system is far from ideal but the power you get out of it can make up for it. Now, this level of power is not needed in many places but once you start hunting thick, powerful fish which sometimes keep their distance and you need the shaft to carry heavy tackle then the Mirage is worth the hassle for me. Horses for courses, my friend.
The alternative is a three banded gun or a multistage (pulley) roller which would be much, much larger to swim and dive with and take about the same effort and time to load. That said, I have a few ideas on how to make a more user-friendly Mirage type gun.
The DreamAir before the pulley loader looked alright to load, but with the pulley loader, not so much any longer.

I may have compared the DreamAir to the Mirage in the past - I can't remember as this saga is so old now. But perhaps it is fair to compare it to a regular oleo or a 1-2 banded rubber gun. Hence, why it has to out shoot those to have any interest to me as a potential buyer/user.
On the other hand, if you really need to use a pulley loader to get any meaningful power out of it, then maybe it is also fair to compare it to a Mirage or even a hydropneumatic and then I am not too positive the DreamAir will come out ahead.

That said, the comparisons here are all speculation at this point.
 
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ECK said:
Diving Gecko «My sliders from Dima are….»

What does he look like ???
Click to expand...

If you are asking what Dima looks like, then that's too much of a thread drift to answer here.
If you are asking about his superb sliders, then see below.

Top: Pathos shaft
Middle: UBL/Dima slider
Bottom: Tomba delrin slider



I tend to show this image every time someone brings up the out-dated argument that airgun shafts are slow because of the bulky sliders, rings and springs.
But let's not derail this thread any further. If you have more questions about UBL or Mirages please ask over here
 
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It is right!
But there are always off-topic questions.
Thanks for the photo. I use mine, even less.
Fish determines the requirements for what gear should be.
I support your thoughts on the justification of a long charge of high power.
But you just have to do it. And it is very difficult.
 
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Conventional pneumatic guns use a sliding linear motion to propel a spear longitudinally, but if you increase the piston diameter to raise the force level available from a certain reservoir pressure inside the gun then you will have too much water to push out of the inner barrel along with the spear. A dry vacuum barrel system may work with a large piston, but any water intrusion inside such a large bore would severely brake the gun. In the "Dreamair" the large piston is used to generate a rotational shaft output instead, so no water goes into the gun and that rotational output is then converted to linear motion by using a winching arrangement. Basically the "Dreamair" gun is a means to use a large piston without exposing the barrel to the environmental conditions outside the gun.
 
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A simple way to verify even winding of the cables on the outer drums is to colour mark the spot on the wishbone that engages on the spear shaft tab or notch. That mark will always sit on the spear shaft if the cables have not jumped a groove both at the muzzle or when the gun is cocked for shooting.
 
ECK said:
When I look at the drawings of this gun, my hair starts to move on my head. But on the gun, the drums look quite compact. Using a pneumatic motor offers many advantages over rubber. I am for pneumatics! Perhaps Andreas made the tackle difficult?
Click to expand...

I think he has to use a rolling drum as it's the only way you can seal the "engine" (air chamber) from the "transmission" (the axle of the drums). If the piston was pulling on a line which exited the air chamber, then it would be very hard to make a seal on that line but making an o-ring seal on an axle is easy. It's a very clever solution to that problem I think.
I think early on, Pete might have posted another patent exactly like that and pointed out sealing issues.
 
I agree! From your description, I finally understood how this works.
The solution to the problem of transmission from the motor to the shaft is original! But I think that this is not the only solution if you divide this type of gun into parts.
Conditionally, I called the type of this weapon “Cordgan”
"Cordgan" has a motor, transmission, housing.
We can use the "engine": pneumatic, rubber, metal spring and possibly others ... ???
Transmission: is the drums and drive cable
The case (STOCK?) Can be wooden, plastic (carbon) or metal (Al)
The design of these parts creates the main advantage of the Cordgan shotgun is very stable behavior when fired.
Very impressive video when Andreas shoots. The Shotgun has no recoil, very high accuracy.
 
"Here is a diagram estimating a gun of 110 cm wishbone draw with a piston travel about 34.375 cm based on a multiple of 3.2 with respect to the relation between piston travel and wishbone travel. Start pressure is 23 atm gauge or 24 atm absolute. post #317, page 16"

Up until now most of my diagrams have used estimates based on what the winding drum proportions look like in their profile photos when trying to put numbers on the gearing, but now Andreas has published some numbers of his own. The original is in Greek, so the auto-translator has made a few errors, but you can understand it.

In the Dreamair aluminum, the piston is 1000mm2 (ie 10Kg armature / atm pressure) with the simple armor having a maximum armature of about 8.5 atm. That is, arming starts at 85kg and ends at 60kg (CVT use). However, since the exterior with the inner winding drum does not start with a 1: 1 transmission ratio, you are arming from 75 kg to 60 kg. The piston at 8,5atm respectively starts charging at 85kg and ends up at about 130kg.

In the Dreamair Unreal the piston is 500mm2 (that is, 5Kg of armature / atm pressure) with the simple armor having a maximum armature of about 16 atm and the difference between the initial and final power being about the same as the aluminum. In the Dreamair Unreal, the inner drum is not capable of a high call because it anchors within this inner rope of the gun and for this reason you manufacture the Dreamair Unreal with three balloons (three air chambers, a central cylindrical one and two flanking chambers as per the patent drawings).
The larger the two flanking chamber volumes are then the lower the compression ratio of the gun. In such an arrangement you can use a longer piston travel than you would have in a monotube as in the latter half the tube length travel takes you to a compression ratio of 2.0.

We have not seen a cross-section of the "Dreamair Unreal" barrel tube, but the closest approximation would be the Sporasub "One Air" tank tube.
 
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It occurs to me that although not an easy thing to engineer a "Dreamair" type gun could be made using a partitioned reservoir system. The crescent shaped side tubes pose a problem, but the pre-chamber could be installed in the muzzle and the partitioned air tanks could be in the side tubes. Basically it would be like a current pneumatic turned back to front and that is not as crazy as it sounds as the pre-chamber on pneumatic guns is where you screw in the hand pump. The crescent shaped power regulator used in the Salvimar guns would obviate the need for a cylindrical transfer port, the main drawback is the controller would be up the front end of the gun. Low power shots would use only the central bore and high power shots would use all the air chambers in the gun.


A quick and dirty diagram for a partitioned "Dreamair".
curved segment type power controller and one-way valve combined.

Note that as there are two side tanks the power controller would have to plug and unplug each of them simultaneously as the power reduction only works if you shoot from a small pre-chamber. A remote controller back at the rear handle could be used to operate a link to the front mounted power regulator block either by a solid rod or a hydraulic line as used in a vehicle braking system.

P.S. The reason why this dual power idea was not used in the earlier alloy tank "Dreamair" is because as produced it used an oval tank which could not be partitioned with all the cables running inside it. In the tri-chamber form the cables only run inside the central barrel and this lends itself to partitioning of the central column from the side tanks by making a muzzle that is both the bulkhead with controllable ports and the axle carrier for the winding drums. The "Dreamair" inlet port is located under the muzzle for pumping it up from time to time and hence this section of the gun can serve as a pre-chamber.
 
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Not a bad idea at all. But I guess for some reduction in power, though probably not as much, you can always just load to the rest tab on the shaft. Though of course that’s not as readily changeable as a power regulator. And if you loaded to the most rear tab using the pulley loader then of course you can’t just move the wishbone forward “by hand”.


Sent from my iPhone using Tapatalk
 
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The power regulator could allow progressive loading just like in a regular pneumatic, so you could arm the gun with successive pulls on the wishbone as each time the one-way valves would trap compressed air from your loading effort in the side tanks. As this partitioned reservoir system has been in use in pneumatic spearguns for about 55 years any patent will have run out. The terms vary, but 25 years would be about the maximum for a patent, if that.

The only difference, bar being back to front, is that a pneumatic speargun is totally surrounded by its tank, whereas a "Dreamair" type gun has its tank on either side in two separate "pipes". The two pipes could be joined if the barrel was raised in the gun and the separate pipes were connected at the bottom. However such a shape may be difficult to produce and the rigidity would be different than a fully integrated central pipe top and bottom.
 
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Using such a set-up you may be able to avoid using the "Dreamloader", however if you put a lot of pressure in your gun then I think the 2 to 1 advantage using the pulley hooks would still be useful as when you near the wishbone drop in point on the shaft the pressure in the gun approaches the cocked pressure regardless of there being a partitioning system.
 
The only spoiler for a partitioning system is any pre-chamber needs to be relatively small. Once I suggested a partitioning system for a Vlanik gun, but because there was not enough difference in the volumes with the isolating means open or closed the power reduction was not that great, from memory only about 10 per cent which was not worth doing. Ideally you want about 1/3 or 1/2 power with the pre-chamber isolated and it doing all the shooting while gas under pressure is held captive in the main tank.
 
Back in post #87, Mares design which has yet to proceed, if it ever does. Everything depends on the seal in figure 5b.
 
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Making barrel Andreas is not very difficult as it seems, but you need experience with carbon. This form is optimal for pressure distribution.

A very long time ago, on the "Harpoon" website, the idea of 2 barrels was discussed, but so far, no one has brought it to life. Although it is very tempting - it allows you to have two powers. And barrel Andreas can give 3 forces.
 
After the publication of the ideas of Andreas, Mares design looks outdated ....

The main problem is the Drive cable fig 5b seal. Such a decision has a short life.
 
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For strength the cable used would have to be a twisted multifilament cord, yet such a cord would be impossible to pressure seal, so this cable gun patent is probably more about staking out an idea and denying its use to anyone else just in case they can find a way to do it. A tough monofilament cable might work, but the surface finish degrading would soon put the gun out of action, plus the piston is not very large in diameter in this imaginative effort from Mares.
 
A coated SS wire could possibly work in terms of sealing, too. The thinner ones are surprisingly supple (I guess the more strands the better). Trick would possibly be to increase the PU coating thickness a little as the thinner coatings still have some of the "weavey" surface of the cable bleed through to the surface. But... still doesn't solve the overall issue with reliability.
 
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