THERMOFORMING REBREATHER COVERS

"SOMETIMES THE MAGIC WORKS
SOMETIME IT DOESN'T"

Chief Dan George in Little Big Man

I always remember that scene when they came down the mountain in the rain.

This project was a lot of fun. It had a learning curve as you can see some failures under the successful formed shell. I have been modifying an RGU and needed more room in the case to add a air tank for deeper diving than the 20 foot limit for oxygen. I did not just want to attach a tank to the bottom of the case. That would be too simple for me. It would also create more things to snag underwater.

This project has a double warning. Fire burns. Hot plastic burns. Torches really burn. Tinkering with rebreathers is not a safe activity. It can kill you. It has killed really experienced divers and has killed the unwary. You should not tinker with rebreathers, they are dangerous critters. I am not responsible for any injuries you get from trying this really stupid idea. Further, I figure the first cover cost about $500 dollars or more to build plus several days of work that could have been productive when a couple of straps would have done the same thing. Pretty dumb for a guy who thinks that he is smart as I think I am. I'm glad my clients are not rebreather divers and see this.

On the upside for me. When Patrick and I placed the softened plastic on the vacuum table, it was really neat to see it take the form of the model. It is fun working with your kids and we both enjoyed the problem solving activity. It was a fun learning experience and this will not be the last thing that I thermoform. It's not about saving money is it Dr. Bob? Trying to save money this way is like sailing to get somewhere in a hurry? It's the process that provides the fun.

The first part of this project was to build a model of the shell as I wanted it to be. I used the RGU shell, oil based clay from Monstermakers to fill in spaces and smooth curves, particle board to increase the depth of the shell, two pieces of 2x4 to lengthen the shell, and some raised letters My Oxygen Machine (MOM). this took about two hours. I expected it to take much longer.
Then we placed the model on the vacuum table. One of the guys made the vacuum table for me from a sketch the day before we left the office for Christmas break. Thanks Mike for the great job. You can see where the shop vac hose connects. The idea is that when the softened plastic is placed on the vacuum table, it forms over the mold.
We stapled a piece of thermoplastic to a 2x4 frame and heated it with our little torch from Harbor Freight Tools until it got flexible. The plastic came from Select Products . It is their low temperature material. I really like working with these guys, they ship fast and have a great customer support attitude.
Here the plastic is soft and rubbery. This is one place I screwed up several times in not getting the plastic soft enough. I was just impatient. Dinner was cooking.
When the sheet covers the model and vacuum table it is sucked in and conforms to the outside shape of the model. I did not get this sheet hot enough and the plastic did not fully conform to the model so I decided to reheat it. Not a good idea as the next shot shows.
Ok, maybe I overdid the reheating a little. Another one for the oops pile. 15 bucks shot to hell....Oh well, you get the idea. Do not attempt to reheat on the vacuum table if you use a torch..... Stay tuned as next week I build an oven to heat the plastic to a more uniform temperature and just heat the outside with the torch. Why not show you now. Well another of my ideas did not work out so well. It created a delay.
My long suffering wife of some 30 plus years of wedded bliss loves snow, so I bought a backyard snow machine for a Christmas present this year. (2001). I accidently left it on all night and look what happened.

Tom