Space SCR prototype is an homebuild selfmixing SCR

gibbogeo

Last March in Rome, at the "EUDI sohw", was presented the protoypes of a new serie of semiclosed rebreather, the "Space".

It have been developed from an homebuild machine made with cookware, bicicle innertube, plumbing pvc pipes and a draeger mouthpieces.



This machine has been built some years ago and, since then, have been dived by the coral fisher who made it three times a week in the range of 100-130m.

The idea is that if you add to a continuous flux of nitrox (actually it use ean40) a flux of pure diluent, without oxygen, increasing with the depth, you can have a mix, in the loop, that is quite stable for the PPO2 (actually it varies with the metabolism) and a FO2 variable with the depth.

The two flux, the constant flux of nitrox and the depth dependent lux of helium, are obtained using two orifices and two pressure reducer (they are not classical diving first stage regulators). The one for the fixed nitrox flux is a fixed ip pressure reducer, with a fixed pressure of 36 bar. In the homebuild it feed nitrox 40 in an orifice that give around 13 liter of gas per minute. The other pressure reducer is feeding pure helium at a pressure that is 2.2 time the ambient pressure (at surface give a pressure of 2.2 bar, at 110m it gives a pressure of 22 bar). The pressure reducer for the diluent have a different area in contact with the ambient pressure and the gas it feeds to the orifice, no spring, no regulation, only a 2.2 times bigger area in the outside surface than the internal one.

In the original homebuilt the counterlung is single and frontal, made with two pot cover (!) connected by a cut bicycle inner tube (!!). When the counterlng is squeezed by the pressure, it press a second stage leverage that is the bypass for the diluent. When the counterlung is full, there is a cable that open a triple seal valve that let the gas flow outside from the expiring hose, before passing through the scrubber.



The scrubber is under the counterlung and is made of a pvc plumbing tube, two steel cake containers and some rubber sealings.



For cleaning the mask or for bailout there is a third bottle of trimix connected to a normal OC first and second stage regulator who serves also as a bailout.

The original homebuilt has no electronic to check the PPO2.

It is incredible the light weight of this homebuild, the reduced dimensions and the fact that it is a ventral unit.

The prototypes of the Space derived from this homebuilt SCR presented at EUDI show are built in plastic and have very few metal parts (no cookware in the commercial units). There are various version, at the moment 4, the simplest one (Space 40) is working as a traditional CMF with nitrox and is limited to 40 meter without deco dive.

The other versions (Space 52, Space 72 and space 120) are versions worhing with nitrox and helium as a diluent like the homebuilt.

All the prototypes have a transparent scrubber container that will be filled with preloaded cartridge of CO2 absorbent. At both end of the scrubber container there is a water trap and one purge valve.

For the moment the loop hoses are in silicone, with a very light plastic DSV.

Are still present the triple seal purge valve connected to the front of the front of the scrubber and the second stage part that works as a ADV. The frontal single counterlung is connected to a dedicated BCD that holds the bottles (one for the space 40, three for the other models).

Actually the Space is still under testing and it is not possible to say when will be on the market.

Yankee Rebel

beautifully done!! i love it!!

shil

Bravissimo for the design.Incredibly creative.
Can you share/illustrate the gas flow schematic ?

Shill

gibbogeo

Here is the "flyer" (in Italian) that explain how does it works:



Practically there are three bottles:

The first is of nitrox 40, with a sealed pressure reducer thet feeds a fixed IP through a quick connection to an orifice that permits a continuous flow.

The second bottle contains pure helium, with a pressure reducer, connected with another quick connection, that feeds a pressure two times the ambient pressure to an orifice that give a flow of gas increasing with the ambient pressure.

The third bottle contains the bottom mix (trimix) and it is connected to a normal first stage that feeds a second stage for the clening of the mask and the bailout (I think it is a 20 liter bottle) and to the ADV (you can actionate the ADV simply pushing on the pot cover till it touch the lever of the ADV).

This is what i have been told by the men who built and use it.

Hope it helps.