Max Tank Size in BMR500 or BP240 shell

S. Marc

Hi,

Anyone know the max tank size and manufacture that will fit into either a BMR 500 of Biopak 240 shell?

I plan on having the 1st stages stick outside the shell, one on each side, but do not want to totally butcher the shell for the actual tank size.

Thanks,

Marc

decoweenie

IIRC, the tanks on my BMR-500 was 13cf with just the tank valves stuck outside, and the first stages inside the case. Can't remember the brand of the tanks since it was too long ago. Sorry...

IMHO, even if you let the first stages hanging outside, 21cf/3L tanks might be too long.

Skipbreather

Hi Marc

The original cylinders used in the BMR500 were short, fat 13 cf DOT 3AL3000/ TC3ALM207 aluminum tanks. They had a convoluted parentage. They were made by Catalina, but not the major division on the west coast that normally manufactures cylinders. They were made by Catalina’s Cliff Impact division, on the east coast. They are 9 ¾ inches tall and 5 ¼ inches diameter and have a tank thread of .625-18 (5/8 by 18 threads per inch). Cliff Impact’s part number was HPC 9063. Tank was originally manufactured for a Drager rebreather. They are black.

There was also another tank used that had the same external dimensions, but a larger diameter thread for the valve. They were yellow. I’m about 90% certain they were made by Luxfer and had a 7/8-14 valve thread (same as older high pressure ‘Genesis’ steel tanks) but I cannot confirm since I never broke down one of the yellow ones. All my tanks were the black ones.

Phi is correct about just the valve tops sticking out of the case, w/ regs inside.

FWIW, another tank I played with that seemed to fit was a standard 9 cf aluminum medical O2 tank.

Hope this helps-

Ken

DanFountain

I've got a BP240 conversion project in the works. The upper recess where the ice-pack used to reside is the right size for a 4-3/8" diameter tank such as a 13 or 19 cf scuba pony bottle or a 6, 9, 11 or 15 cf medical O2 bottle. A 13 cf pony bottle is just a bit too long with a standard valve on it, although I've seen one with a low-profile valve stuffed into the space. (See http://www.rebreathertech.com/scuba/biopak240/complete/) The trouble with that is, the valve knob is inacessible while diving. What I'd like to use is something like the Scubatec "Comptec Big" DIN valve (see http://en.scubatec.it/monoattacco.htm ) which has the valve knob coming out axially with a radial DIN outlet. Anybody know where I can get one in 3/4" NPSM in the US? ?

The lower recess, where the big, fat composite O2 tank sits, would fit a 5-1/4" tank such as a Luxfer L013, a 3000 psi airpack tank which takes a 0.750 x 16 valve, such as a survivair escape bottle valve. (is this the same size as the "oddball" O-ring sealed valve seen on some old 72 cf scuba tanks?)

As a side note, does anybody know what kind of plastic the center section is made of, and what kind of adhesive will bond to it? I mean seriously bond to it, like building up the outside of the center section inlet so the restriction could be ported out.

I'm interested to hear how other BP 240 modifiers are doing.

Dan

S. Marc

Hi,

Thanks for the info you have all provided.

I have had good luck with bonding 2 part cold cure epoxy to the center section, as well as Brownells stock bedding compound (used to pillar bed or just bed the actions of rifles) I think it is just a high end 2 part epoxy.

I am also looking at removing the restriction on the center section inhale port.

What are your ideas for doing this Dan?

I was thinking of just cutting the sides of the inhale port rectangular piece after in comes into the center section, and molding in a wider part. This is hard to explain and visualize.

I looked at a BMR 500 center section picture and it appears that what they did was lower the base of the inside of the center section that the scrubber fits into, to allow a proper port / tube for the inhale tube to go without restriction.

Any thoughts?

Marc

Skipbreather

Hi Marc-

The BP240 center section is essentially IDENTICAL to the BP60 center section and has the same major problem w/ the “half moon” shaped restriction. The BMR500 center section, on the other hand, was a cross between the design of the MK15.5 center section and the BP center section that was custom designed and built for the rig. If memory serves it has full 1 inch inside diameter breathing ports for both inhale and exhale. It also uses couplers for the MK16 (VS MK15) to take advantage of the larger bore.

So: If you want to modify a BP center section and home build have fun- BUT spending more money for a BP240 (vs a BP60) as a starting point will not get you a better center section, just a fancier back plate. Even the O2 reg is identical. You WILL get a higher capacity scrubber and a slightly- about ¼ inch- taller metal dome.

Good luck!

Ken

DanFountain

Marc,

If I could find an epoxy putty or other structural material that would bond securely with the filled poly-something plastic of the center section, I would
fill in on either side of the inlet and then grind it out to a more-or-less rectangular opening with a cross-sctional area at least equal to the ID of the hoses. Otherwise, I might just cut off the existing inlet spigot & build up a new inlet piece with the rectangular cross-section and bond it into place - probably in a different position about 90° from the outlet so hoses are over the shoulders ala BMR500.

Dan

S. Marc

Dan,

one of the three center sections I have had a small hairline crack in it where the center sectin goes to a 90 degree just below the lid sealing oring. I also tried to tap a second set of drilled holes into the center section once it was rotated, to make an easier connection for 02 and diluent, but used a product named Rapid tap which promptly melted the plastic holes I have drilled, making them somewhat oval. I used Both Brownells 2 part glass bedding compound and cold cure epoxy. Both bonded to the center section very well, both are sandable (is that a word?) and can be painted or dyed if necessary.

As I have a spare center section, the one I repaired as above, I think I may try what you suggested. Cut off the existing inhale port, fill the area with epoxy, and attach a machined piece of PVC tube, and create a rectangular PVC piece for bonding to the center section.

More than a weekend job, so if I do it, I will post pics in a couple of weeks.

Marc