Here's a glimpse of what I've been working on:
This is going to be a sealed, pressure compensated, magnetically coupled thruster using the current OpenROV motor and the Delta V-15 prop. Currently, the pod diameter is 32 mm, and the overall length is probably going to be just over 120 mm. When it's finished, the thing will be filled with mineral oil and sealed, at which point it should operate at essentially any depth.
The first couple of sets are going to be machined (with the magnetic couplers made using rapid prototyping), but once I feel comfortable with the design I'm going to look into casting some of the pieces out of resin, which should make additional units much cheaper.
Currently there are a few outstanding tasks:
- Add the structures needed to attach the thruster to the ROV's hull (and provide power)
- Add the duct.
The first task should be pretty straightforward: pick a nice airfoil section and add some mounting hardware. The other is a bit more tricky:
- Duct design has a substantial impact on thrust
- I don't have any good simulation tools for testing
- Manufacturing foil shapes is difficult, slow, and usually expensive - you need a very good machinist (I'm fair, but not that good), a CNC machine (I wish), or an RP machine (again, I wish)
- Iteration is going to be expensive
For now, I may just punt - use a modular interface to put something on there that is probably going to work acceptably well. Then if I find myself with more time, tools, and some further experience, I can tweak it to my satisfaction.