Fix the IP of a s/pro mk2 1st- how?

[Woz]

I'm prepared to put virtually zero R&D into it- it's not my core business, I can make more profitable non-diving things and I'm just tinkering.

Hindsight is great. You can take other people's designs that they've spent thousands on, look at the problems with them and iterate from that, just like all your stuff does at Narked at 90, John- you've identified a need for bits to make a RB better and gone ahead and manufactured them.

Now if you could afford the time to take everyone else's work, cherry pick the best bits to save yourself all the development costs from scratch then design a RB from that then you're onto a commercial winner. At the moment the RB market in terms of commercial units is still very much in it's infancy- it's coming together but give it a few years and they will become much more mainstream as the problems with each type of unit are ironed out, cherry picked by other manufacturers then designed into new units. It's what happens with everything- cars, washing machines, bicycles.

However- I'm doing it for fun and to learn, not for money- just to dick about with it. No way am I going to start manufacturing RB- there's just no money in it. The market's too small and the development costs too high. Try reading the British Standard for RB testing- it's very arduous and would cost thousands to complete.

[Duncan Price]

Originally Posted by Woz

To be fair to Duncan, his sidemount RB is a very well put together bit of kit that can easily be repaired if you can find a B&Q. And the rocket tube is genius. It's a 5 hour scrubber cannister, tough as old boots and totally waterproof. I'd say it was actually better constructed than an Inspo scrubber and has been tested more thoroughly for ruggedness and watertightness.

Late to the party, but my name was mentioned.

Thanks - and the scrubber will soon be tested for performance when I hook my next one (identical to all the others) up to a gas line, array of thermocouples and a mass spectrometer. Because I can.

To be serious, my approach has been to use readily available, off the shelf components with a modular design which means that I could fix most things by a quick trip to the local DIY store. Just because its plumbing fittings doesn't necessarily cheapen the outcome*. To quote an apocryphal story - NASA spend $$$ on making a biro that would work in the absence of gravity, the Russians used pencils.

If I was doing the same process again, I'd buy a commercial unit except that:

1. There wasn't anythnig that I liked available when I started.
2. I'd have to get some diving certs even to do a course.
3. It wouldn't have been so much fun (but cheaper).

With 5 D5's in different users hand there has been a lot of improvements from Woz and others. The actual R+D work is not trivial.

* I'd use George-Fisher connectors next time.

[Woz]

Instead of George Fisher connectors (I think they are the industrial ones) the John Guest plumbing fittings are the ones to go for. You can get additional ferrules for them that turn each coneection into a twin O ring design- i.e., more secure than most fittings used on commercial rebreathers.

Alternatively there is always the industrial fittings route but they are pricier, more difficult to obtain "off the shelf" and dimensionally bigger. I reckon the GF stuff just might be top banana for the application.

[Duncan Price]

Originally Posted by Woz

Alternatively there is always the industrial fittings route but they are pricier, more difficult to obtain "off the shelf" and dimensionally bigger. I reckon the GF stuff just might be top banana for the application.

The GF ones are face seal though - at least Polyplumb (however naff) are barrel seal and allow rotation and a fair amount of play. Both of the rigid inlet and outlet tubs from the mouthpiece hose are clipped securely to the CL case and the whole is now very rigid.

BTW if you are making up a Delrin gas feed block you also need an isolator on the O2 line as needle vavles do not seal completely. At best you might waste O2 on the surface, at worst the ability to isolate the O2 feed without depressurising the supply line can help avoid a spike.

[Woz]

Gaaaaaargh not GF- JG. John Guest. You get a twin barrel seal on them.