Deathbox in action, Mexico- 200 feet and mixed gas! And some notes...

BP60 in Mexico.jpg

Homebuilds in action!
So- here is a little hot action from my Bp60- just returned from 10 days in the Yucatan helping UADY (university in Merida) catalog cenotes with archaeological artifacts, and check for new cave- Found a cave with more tha 3000 feet of passage- connected two huge rooms with some passage between 160 and 190 and passage that led off in two directions for a bit. Three dives in three days completed on the BP-60- each four hours long (my safe limit on my scrubber is 4 hours), doing various stuff- laying line, survey, removing line, bla bla bla. The breather clips on over my sidemount rig, which this trip consisted of weighted 80s and an offboard 40 of O2, as we couldnt figure out a way to fill the onboard 13cf O2 tank. (No proper fill adapters.) Anyway, the pic is me adding an archeo line to nearby artifacts so they could be added to the survey.


Re: My BP-60 success story!

So- an update on the Biopak 60, as a couple of people have been asking.

After returning from the Yucatan (see post pic above) the machine got a few straight weeks of use in Florida, where a friend of mine, and ADV contributing author Jon Bojar, took some photos for me. In addition, the machine got a dive at Blue Spring Resurgence, in Tennessee, one of the projects that Chrissy and I have been working on for the last couple of years.
Some things I have learned:
I still, consistently get 4 hours of burn time out of this "60 minute" scrubber. This is true in both Florida 72 degree water and Tennessee 50 degree water. I was sure that we would have to insulate the can somehow, but that has not proven to be the case. My attempt at rigging an in water self-donning harness has not been a success. In Tennessee, the cave requires that the machine be pushed approximately 150 feet into the cave before it can be donned- this was quite the pain in the ass, as it does not float level, and is quite difficult to manage through tight areas with one hand. In addition, Chrissy had to make all of the attachments for me, as I was unsure that I would be able to get to them in the cave. We got it on, and the dive continued (horrific 2 foot viz for four hours) and it worked just fine throughout the dive, but not being able to don the machine myself pretty severly limits my intent for it. More thought will go into this part. 
I still have not managed to purchase a quality gas readout and decompression computer to the machine, but that is coming- Shearwater or the new X1 system will be in hand before the end of 09.
As for other lessons learned:
1. The barbed fittings used on the connections for the orifice and pre- and post filters are inadequate. I have found that if the machine sits in the hot sun, the tubing becomes soft enough that under pressure, it will separate from the barbed fittings. Don't know how this did not happen earlier, but it finally did in Florida, and so now I know. I have a few options open for swagelock type fittings, and possibly even the push-lock fittings, to replace the barb orifice, but the price will not be anywhere near as attractive. 
2. My skills with the silver solder are not top notch- the brass tube fit to the fore banjo nut shown in the left side picture has come loose again and leaks gas. This is surely a technique issue, as there is almost 3/8" of contact area between the inner wall of the orifice and the tube, so there should be plenty of solder area available. Lessons to learn. 
3. The K1D sensors in use have a depressingly short life span. One of the sensors is already giving up the ghost, so I will have to change to a different sensor, but that will be a matter of cutting a new sensor block mount, hardly a difficult project.
4. The diluent and oxygen addition buttons are STILL the same shape. This is not acceptable at all, as the addition manifold is not within view without removing it from its bungee attachment at the right shoulder. The only saving grace is that the gas content changes so slowly it doesn't really matter what button you push, as long as you are watching the readout when you do it, you can figure it out pretty quick. It also helps that I NEVER have had to manually add diluent. I might ask why I even have the diluent button. You never know, I suppose. Anyway, easy fix- hour or two at the mill/lathe.
5. As mentioned above, attachment harness works well for surface don/doff, but hardly at all in water, and this will have to be addressed. 
6. I am not completely happy with the oxygen mounting business- There are some dives where I would like to have the tank mounted to the machine itself, to clear me of stage bottles, but the amount of gas consumed in four hours (about 2/3 of a 30, after bumping it up for deco) makes for a strange bottle configuration. Mounting the bottle on the bottom makes the whole thing very ass heavy, and if I went to put it on either side, I would probably have to use two bottles, more than I need. More thought on that later.
7. Deep. Hard to say what is up here. I have made four hour dives at 160 feet, which is as deep as this machine has been, but I would like to take it deeper and see how she works out. Antecdotal reports indicate that I may be able to use the system deeper, switching to manual oxygen addition, but we will see. I would also like to experiment with a non-fixed IP first stage and see how that works out. Stuff to play with later.

Thanks, for those that have been reading these and building their own machines- good luck with yours, hope to see you ALIVE in the water!

 The running joke on rebreatherworld at the time.

The running joke on rebreatherworld at the time.