James Harvey adapted a Fenzy escape rebreather model NSN4240
How a small 1984 Fency rebreather can be rebuild to a nice oxygen rebreather
Dear Janwillem,
Here are some pictures of my adapted Fenzy escape rebreather. It is a 1984 NSN4240 and I acquired it without its original O2 bottle. Intrigued by the little rig I set about exploring other ways to mount a cylinder, basically to see if it could perform like a latter-day DSEA or a mini ARO.
When I got the rig there was a lot of nasty old foam insulation and thirty year-old absorbent in the scrubber which had to be removed. The original overpressure valve was stuck and the O2 inlet manifold had to be sealed, so these issues were fixed as part of the upgrade. Taking inspiration from the CEDU, I opted for a field expedient O2 bottle (1ltr / 110 bar) and regulator from a home welding kit. The bottle is mounted underneath the counterlung using diving knife straps and a rod passing above the waist belt fixture. This makes it easy to ‘feather’ the valve and add gas as required.
Duration is about 1 hour under minimal workload! Scrubber holds 1.25kg of sorb. I also use a DSV from a Naubos AR88 with it (pictured). The WOB is slightly worse than the original Fenzy DSV as it has a smaller bore, but the AR88 DSV makes pre-dive purges much easier.
It is a cute little pendulum rig for lazy Sundays spent at 5m.
Happy diving and best wishes for 2014!
James
Cornwall, UK
INTERMEZZO: By using an adjustable flow regulator this rebreather is a constant injection rebreather (CIOR). The flow meter is normally used for the supply of shielding gas for MIG-MAG or TIG welding. A method that is certainly interesting but requires an exact setting to supply exactly enough oxygen. If the regulator is set to, for example, 0.8 – 1.0 liters of oxygen supply, a good balance will occur when breathing calmly. However, if you work harder, this flow may be insufficient and should be adjustable underwater.
James, thanks for sharing this information!
This page was first published 29-12-2013
Therebreathersite was founded by Jan Willem Bech in 1999. After a diving career of many years, he decided to start technical diving in 1999. He immediately noticed that at that time there was almost no website that contained the history of closed breathing systems. The start for the website led to a huge collection that offered about 1,300 pages of information until 2019. In 2019, a fresh start was made with the website now freely available online for everyone. Therebreathersite is a source of information for divers, researchers, technicians and students. I hope you enjoy browsing the content!