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petn7 -> RE: I FINALLY BUILT MY OWN SUB FROM SCRATCH! (7/14/2004 9:31 PM)
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The bottles are about 45mm OD and made of HDPE. i bought them from some bottle supply company online, but i forgot their name. they bascially had any type of plastic bottle you could want; HDPE, PETE, etc. they like to sell in bulk, hence why i paid alot of money for just 10 bottles. plumbers tape will probably be over kill or have very little effect on water tight integrity for a few reasons. look here:
http://www.rcuniverse.com/forum/upfiles/109821/Yw68127.jpg
notice how there is basically 1 thread on the bottle neck opening? the top makes a water tight seal from the pressing of the top edge of the bottle neck on the plastic-like-foam on the inside of the cap. w/o modifying this configuration, the bottles can maintain water tight integrity to at least 9ft. i tested these bottles by making a very crude r/c diving bell with a sealed ballast tank. i could make the diving bell surface and dive on command with no water leaks.
the 2 tubes where the servo wires come out are only sealed by using a thin plastic tube filled with vaseline...that's it. after these pictures were taken, i made some modification to the 2 plastic tubes filled with vaseline. i added a small plastic stuffing box which should help seal the servo wires even more. however, i doubt even this stuffing box modification can hold a water tight seal down to 9 ft reliably. another source for a water leak is where i glued the 2 bottles together, end to end. it's a pretty good seal, but that middle joint, along with where the servo wires come out of the WTC are more likely to produce a leak than the end caps.
the motor case is its own WTC. it's filled with vaseline and sealed with silicone glue. the motor WTC came with the Alfa plastic kit. see, this plastic kit was designed to run in pools under no human control. it would surface and dive automatically.
in regard to your e-mail, there is no "tray" b/c the neck of the bottle is narrower than the inner diameter of the bottle itself, so it would be hard to get the tray to fit right. since the components are bascially stuffed into the bottle WTC i have a feeling the sub will have a slighty different center of gravity everytime she runs, but since the components and wires are light, this "wild-card-weight" shouldn't be a big deal. i have only tested the sub in the bath tub and everything works fine. when the paint job is done drying, i'll take it to a neighbor's pool and do a full test and hopefully get some underwater pics.
oh, and another modification i did was make the battery smaller. now it's 4 cells instead of 7. this will be an advantage for a few reasons. one, the motor will last longer. two, this allows me to have less "wild-card-weight" so i can add more weight to fixed points outside of the WTC rather than them being loose inside the WTC.
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