Infinitengines "Dreamair" pneumatic speargun

[popgun pete]

The "Dreamair" piston appears to have a concave, hollow rear end which I assume envelops the cone shaped nose of the rear bulkhead, or at least it did when this photo was taken. The piston's shape may have been changed since now that this shock absorbing, telescoping column has been added to the design.

 

[popgun pete]

Check out the quality of the winding drums, axle components and bearings in these recent photos. They are excellent examples of precision metalwork realizing a brilliant design and are beautiful objects in their own right.

 

[tromic]

Very nice!

 

[popgun pete]

Now we know that the winding drums are indexed to the axles by the "keys" (that fit in the milled slots or keyways in the axle) which ensure that the drums are at the correct angular orientation with respect to each other, so what about the cable end connections? These new photos show that the cable anchor positions are fixed on each drum by a mounting position which enables an end loop in the cable to be attached.

inner drum, second image has the bearing housing removed from the axle for a clearer view

outer drum, viewed from the inside, note how it is hollowed out internally

loop end in inner cable using a splice

 

[Diving Gecko]

Yeah, I noticed the splicing work in an earlier pic. Nicely done in that size

 

[tromic]

Yes, the force on the piston would be somewhat less with pneumatic shock absorber. But the influence of that would be practically negligible. After the firs turn of spiral track cone (6.6 cm wishbone move) the force would be about 0.5 kgf less. After next turns the influence becomes really negligible. Ive tried to show it on diagram but the difference can not be seen. Advantage would be less complex design but maybe would not be reliably over time, if there would be some tiny air leakage from the pneumatic shock absorber air volume.

Additional space for piston movement would be another benefit.

This earlier design seems to be like mine proposition for shock absorber...? But, maybe the strings elasticity was supposed to work as shock absorber? Here on the image the nose of the handle is hollow so pneumatic shock absorber would not be efficient (because of parasitic air).
Another thing, maybe the final pressure is 11 atm, not the starting pressure..? In that case mine calculation of forces on the diagram match quite well, but for the starting pressure 5.5 bar instead of 4 bar.

There is another detail that seems to be problematic to me. Bending radius with respect to the Dyneema OD seems to be too small what might be a significant problem both on anchor point and on the piston side!? That reduces the strength of dyneema. I had similar problem with my early Easy loader where the axle was 8 mm and the dyneema 2 mm. Very soon the dyneema started to tear and finally broke although the force was only about 30 kgf. I solved the problem after using 12 mm axle.

 

[popgun pete]

I recently found a slightly later patent from Italy which shows another approach to creating a cable speargun with an "air spring" or "pneumatic power" energy store. If you look closely then you can see the "Cyrano Evo" lurking underneath.

I don't think the above will be much competition for the "Dreamair" as it is not as sophisticated in its design because the power stroke for the spear is the same as that for the piston travel. However this one is a "rollergun" of sorts.

 

[Diving Gecko]

Interesting but I wonder what kind of line/cable that you could get obtain a seal on. Coated stainless steel wire perhaps?

 

[popgun pete]

Interesting but I wonder what kind of line/cable that you could get obtain a seal on. Coated stainless steel wire perhaps?

Well the gun may just be a "me too" idea responding to the "Dreamair" patent, to find out one really has to wade through the patent and I have only read the abstract and shuffled the diagrams around so far.

 

[popgun pete]

I have now read the patent and that aspect is not actually discussed, although I think any cable that will consistently seal cannot be a twisted yarn or wound fibre form of cable unless it was either smoothly sheathed or a fluorocarbon monofilament. The latter is strong stuff, but this cable seal is the "Achilles Heel" of the entire concept and now you can appreciate the genius of using the rotating winding drum axles instead to traverse the pressure boundary in the "Dreamair" speargun. Also its CVT aspects mean that the stroke of the piston is not limiting on the stroke of the spear, hence the "Dreamair" speargun can use a short piston stroke with a big X-sectional area piston in the "flat" initial section of the compression ratio vs piston travel graph and yet still have a long power stroke, or wishbone draw, for the spear. When you collect all these different elements together you can appreciate just how inspired the "Dreamair" concept is.

 

[tromic]

Something to think about... WLL - weight load limit

 

[foxfish]

You guys might be interested ... https://forums.deeperblue.com/threads/im-from-russia.107405/#post-962312

 

[popgun pete]

You guys might be interested ... https://forums.deeperblue.com/threads/im-from-russia.107405/#post-962312

Hi foxfish, yes, I am interested, although I have seen some of Sergey's work before. In between the arguments and bickering on some of the Russian spearfishing forums ideas and new designs do manage to get seen and discussed, although it can be a long wait! Spearguns are designed to do a job in a given fishing environment, so their attributes reflect what is required in those situations. As well as the gun it would be instructive to learn just what those conditions were. For example a "Taimen" looks to be a "string bean" of a gun which appears almost too slim for a pneumatic, that is until you are weaving your way, and the muzzle's, through a forest of stems and branches looking to spot a target hidden in the gloomy irregular network of objects, both yielding and unyielding, in order to shoot it.

 

[popgun pete]

There is a delay with the "Dreamair" as some parts of the gun are being updated for the production version, possibly one of them being an extra relief valve (in the rear tank section) which was discussed earlier on this thread. (refer post#28)

 

[tromic]

Would there be two valves, front and rear?

 

[popgun pete]

At the front end, under the muzzle, is the air inlet valve; in the piston there is a valve to allow air to squeeze into the front chamber from the rear in order to take all air out of the rear tank when the piston first moves back during initial pressurization. I suggested that a blow-off valve would be better in the rear bulkhead to do that emptying, plus it would cope with any slight piston seal leaks better. Whether the gun has all three valves I don't know, but my view is the one-way valve in the piston could be eliminated.

 

[tromic]

At the front end, under the muzzle, is the air inlet valve; in the piston there is a valve to allow air to squeeze into the front chamber from the rear in order to take all air out of the rear tank when the piston first moves back during initial pressurization. I suggested that a blow-off valve would be better in the rear bulkhead to do that emptying, plus it would cope with any slight piston seal leaks better. Whether the gun has all three valves I don't know, but my view is the one-way valve in the piston could be eliminated.

I do not see any way how could the air be squeezed, through the valve in piston, into the front chamber from the rear during initial pressurization...? The only way to push the piston deep into the barrel would be using some stick or similar device and then pressurize the gun. Better solution is as you advised, using a valve at the back of the barrel instead at the piston.

 

[ECK]

I am here because I saw "Dreamair" project. Such a project in my head for a long time. But I see that the author has made everything very difficult. Very beautiful and expensive work. I wonder can you tell me how many guns did the author?

Я здесь потому что увидел проект "Dreamair". Такой проект у меня в голове очень давно. Но я вижу что автор сделал все очень сложно. Очень красивая и дорогая работа. Интересно вы можете мне сказать сколько ружей сделал автор?

 

[popgun pete]

You would have to ask him as we don't know. Everything has been thought out, it is an unlikely operating system for a speargun, but when you look at the Mares concept the sealing of a cable is very difficult and therefore the sealing at the axles is the more practical solution. Then everything else follows as to maintain a pressure isolated inner cable system the wishbone outer cable must logically be a separate cable.

 

[popgun pete]

I have received an update from Andreas, it appears that the valve was never in the piston, but in the rear bulkhead after all. Now we can see photos of the piston and the rear bulkhead. You can also envisage that the piston and rear bulkhead would appear similar from their rear views, but this is the first time that I have seen either of them.