So... you want to build your own watertight cylinder?
 
First off, STOP. Take a deep, hard look at your skillset and experience. If you do not have extensive experience with RC submarines, electronics, soldering and basic RC wiring, this is not the correct path. Period. End of story. 

If you do feel you have these skills, or you choose to ignore my warning, then this package of 3D files may be something worth investing in. Before you go any further, if you do go down this path, you are on your own. You decided to take this on and you'll deal with the consequences. If you do need help, it can be made available by booking and paying for consult time on my website here. 
 
This product was never intended as a commercial offering and is only here due to extensive requests. Building a cylinder is a massive undertaking filled with challenges and, if not done correctly, can result in the total loss of your RC submarine. You've been warned. 

These are the files that were previously used to produce my 2.5" SubDriver watertight cylinders. These units are no longer in production, I don't have excess stock, and I am no longer supporting them.  There are no instructions available. 
 
The file package includes: 
 
Battery Tray
EndCaps
Ballast Bulkheads
Gas backup mount
Pump bulkhead
Servo / motor mounting clip
Ballast adapter
Gas backup mount
Servo plug (to cap off unneeded openings in endcaps)
Clear tube adapter ring
 
What you'll need to source (No, I do not offer these products at this time):
 
Brushless or brushed motor of your choosing with 19mm mounting hole spacing. You can simply drill out different hole spacings if your motor has different configuration
ESC suitable for the electric motor you chose
Drive coupler for connecting motor to 1/8" drive shaft
12V air pump such as this one from Amazon
Silicone hose 2mm ID x 3mm OD for air hoses
2IS pump and ballast servo controller
Mini servos such as these ones
3S LiPo battery
1/8" brass tube used to create pass throughs for ballast air, ballast vent, as well as linkage rods
5/32" brass tube for ballast vent sleeve
1/8" shaft seals. I go into the construction of these in this video
M3 threaded stainless rod for cylinder compression
M3 brass standoffs for installation in pump and ballast bulkheads to screw threaded rod into.
M3 acorn nuts to secure end caps onto cylinder
61mm ID x 65mm OD clear plastic round tube for main cylinder body
1/2" OD clear plastic tube for wiring passthrough in ballast tank
Rubber orings 63mm OD x 56mm ID x 3.5mm width for main cylinder seals
Rubber orings 3mm ID 1.5mm width for acorn nut seals
Linkage horns (build or buy) for ballast linkage
1.5mm pushrod linkage stopper for ballast linkage to ballast vent
1/8" stainless steel rod for main drive shaft
1/16" brass or stainless rod for servo linkage intermediate shafts
M3 and M4 stainless bolts