APD Inspiration Classic
4th Cell Holder
Please note, this version fits the Classic Inspiration only.
Before reading any further, please read & understand the following statement. Ordering items off this site indicates your acceptance of the following conditions.
I accept that:-
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This item has not passed CE marking or any other quality control standard. Using this item on a CE marked piece of equipment will probably invalidate the CE marking of that equipment.
OK that's the legal bit out of the way, on to business
After buying & using a commercially available 4th cell holder for my Inspiration, I realised that it had several limitations which affected its performance to the point where it was worse than useless.
a, Due to the placement of the 4th cell, i.e. outside of the scrubber head & out of the main gas flow, it did not track the ppo2 as accurately as the 3 main cells.
b, Calibration was nigh on impossible, despite following the manufacturers instructions to the letter.
c, It leaked!
So out of frustration I set out to devise a better alternative, the MK1 version was cobbled together in true Heath Robinson style in the shed. This at least proved that the concept was sound. I.e by placing the 4th cell inside the head, adjacent to the 3 main cells an accurate consistent reading could be achieved.
I dived the home made version throughout the 2004 season with great results. Dives were in the 10 - 80M range using air & trimix diluents. During the autumn / winter of 2004 I was approached by a friend who had taken the concept & had a CAD design drawn up. After slight modifications to the drawing we had a prototype (MK2) made up out of white Nylon. This was checked dimensionally in a scrubber & test dives were carried out early 2005. The design was "tweaked" & a production run was ordered from a contact that I have in the precision engineering industry. The production version is made from black Delrin (pom h) & is of an extremely high quality (the same fella makes parts for nuclear subs, but we can't mention that!)
On that note, should anyone be interested in small bespoke production runs of precision parts at reasonable rates in a variety of materials, please contact me here. A design service is also available, anyway I digress. One of the main design criteria was that no permanent modification should be necessary to the unit to enable fitting of the 4th cell, this was achieved by placing the cable entries in an extended portion of the cell centre tube, see photo below
Once the tube is fitted into the scrubber head, it is possible to change the cells without removing the tube, It is a little fiddly but achievable. The one piece design ensures that the installation is solid & reliable
The version shown is the "double" option. This is to allow 2 VR3s to be connected to 2 separate cells, in effect a 4th & 5th cell. All the centre tubes are drilled to take upto 5 R22 bud or similar cells. The various options with regard to cable configuration & prices are explained in the order form & disclaimer PDF or Word DOC
Fitting instructions are available here, this will give some idea of what is involved in fitting the cell holder to your Inspiration. Due to the fact that no drilling of the unit is involved, fitting is pretty straightforward, anybody can do it, honest!
If preferred, Fischer connectors can be fitted to the cell holder in lieu of cable glands, a double ended cable would then be used to connect the cell holder to the VR3. Personally I would avoid this option as it introduces additional electrical & mechanical joints into the system, it is also more expensive, considerably.
In addition to being used as a 4th / 5th cell holder for dive computers, the cell holder is ideal for use where a cable needs to enter the head for a HUD application. In fact it is perfectly feasible to use one cable entry for a VR3 4th cell & the other entry for a HUD as in Uri Barans unit, Thinking about it, add our 4th cell holder, VR3 & Uris' HUD & you've practically got a Vision unit, hmmm!
Each holder is configured to your individual requirements, with regard to type & position of cable entries. For example should you require fittings for a glanded 4th cell cable & a Fischer port for a HUD, no problem, just ask. Similarly we can fit Lumberg connectors to suit other HUD applications. This bespoke service ensures that only the necessary holes are drilled, reducing the possibility of leaks into the unit.
Our cables are professionally assembled using genuine Fischer connectors, complete with protective rubber boot. The cables are potted with epoxy at the gland end, to ensure integrity of the seal should the cable suffer external damage.
This image shows a cell holder fitted with a VR3 4th cell cable & a Fischer port for a Rebreather Guardian HUD
We now have over 50 of the units in use around the world, with no returns or reported problems. The next batch is now available for sale, delivery is usually within 2-3 days of receipt of payment. The current model will only fit the Inspiration Classic
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The cell holders are available from either of these well known dive stores Or by mail order here
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Please do not hesitate to get in touch should you have any questions whatsoever. Email
David Harrison