My rebreather

The development in chronological order. For those not interested, here is the actual unit and some details.

Most details will be changed in the future, I think. But this was a fast way to get into the water. Like with my DIY-lights I try to get around with as less money as possible. But you have to buy some parts (tanks, regs), others are difficult to make or replace by something cheap (mouthpiece, corrugated hose).

the first try.

1st dive (19.3.98): without scrubber, just to see if it's dry -> it was not.
The green hose was much too stiff, it was replaced by another corrugated hose. The connections to the scrubber cannister were not sealed OK. The orange BC need a better hold.

2nd dive (26.3.98): without scrubber, just to see if it's dry -> it was.
Now I use a screw connection at the scrubber cannister, which is additionally sealed with glue. The orange BC got a better hold, but it still is bad to handle.

3rd dive (2.4.98): with scrubber, pool, nitrox 50%, 20min, about 1,6m -> OK, some small bubbles, gas exchange every 45sec one breath - about 3l. Gas deployment through the mask is OK. But buoyancy changes and you have to add fresh gas quickly. Volume change by consumed oxygene is only slightly noticeable.


4th dive (16.4.98): with scrubber, pool, nitrox 50%, 20min, about 1,6m -> OK, but some water in the scrubber cannister
I got rid of the orange BC and exchanged it with two seperated bags. No bubbles. Maybe the sealings are no good at negative pressure.

5th dive (19.4.98): 1st open water dive at the Erlaufsee, dry suit, 5°C water, 40min at 2-4.5m, gas exchange every 45 to 60sec. -> OK, some water in the hose below the scrubber cannister, buoyancy control is VERY strange, especially at this low depth with three independent buoyancy devices; I don't see much of the small fauna :-)

The scrubber cannister is additionally sealed with glue.

6th dive (21.5.98): 1st open water dive at the Erlaufsee, dry suit, 5-11°C water, nitrox 50%/21%, 40min down to 33m, below 20m with air -> OK, too much weight, so big problems with buoyancy, water in the cannister (ca. 300-500ml), though scrubber did its work, WOB is higher , new protective bow.
The water goes through the Mares inflator, which opens at negative pressure, exchanged it against standard (e.g. Zeagle) inflator.

7th dive (27.5.98): Rovinj, neoprene suit, 18°C, nitrox 42%, 40min up to 10m -> OK, changed weight from 9kg to 2kg, buoyancy control gets better, no water inside

8th dive (28.5.98): Rovinj, Valalta, 18°C, nitrox 44%, 70min up to18m -> OK

9th dive (1.6.98): Marina, 18-15°C, nitrox 48%/21%, 48min up to 40m, gas change at 20m -> OK, felt some impairement at depth, WOB OK, inflators have too less gas throughput, scrubber (3l) now at 4.7h - no colour change

Details:

Scrubber cannister:

The case is from a hardware store. It's a intermediate part for cleaning waste water tubing. The screw cap allows easy filling of the scrubber. Volume is about 3l.


The hose connectors can be screwed.

At the inside of the cap is a stainless steel water filter located, which gives relativly low breathing resistance. The sealings are also glued.

Hoses:

The hoses are from an old breathing machine from a hospital. Most connections are done with steel collars, brass parts and clear hose. This hose can be formed when warm and you can watch the gas ways. It was necessary to use teflon tape at some points. The brass parts are from water installations. The diameter of the gasflow is not large enough, but until now there have been no problems.

Mouthpiece:

I use draeger mouthpiece of a two hose regulator. Brass parts and clear hose adjust the diameters.

Counterlung:

I use two 4l outdoor drinking bags now. I drilled a hole into the O-ring sealed caps and inserted tank adaptors for boats with a flat sealing.

Mountingplate:

I mounted a 4mm stainless steel plate at my old BC, onto which the other parts are screwed. The tanks are fixed with stainless steel collars. Two snap locks hold the scrubber cannister. With scrubber the unit is slightly negativ, without slightly positiv (about 1,5kg).

Semiclosed Circuit:

I use the unit semiclosed, i.e. I put gas in (e.g. 50% nitrox), breath a certain time until the oxygen partial pressure should theoretically have sunken to 0.2bar. Then I remove one breath through the mask and add new gas. I made an excel file to calculate the different modi. When going deeper air can and must be used. FO2 may sink down to 3%, so a normal Divecomputer cannot be used. You have to plan the dive before exactly. The narcotic effect willl rise, too, because of nitrogen PP.

Plans for the future:

back to homepage | Rebreather main page | start of page