Underwater Robotics Questions

[Greg Marra]

Originally Posted by Mikell Taylor

Ask one of my former interns (Gui or Ana perhaps) about the robo shark they dissected -- I think the manufacturers used copious amounts of grease to "waterproof" that guy's servos.

I've also polled folks who have built swimmers for Olin's Design Nature course, and I think we've come up at the best DIY underwater servo solution possible on a budget.

1. Get a normal hobby servo
2. Open it up, coat circuit board in epoxy
3. Create stuffing-box-like seal with two O-rings between the output "horn" and the inside of the case
4. Reassemble servo in mineral oil
5. Dip servo is plasti-dip

I don't know anyone who has done all of these steps on a single servo, but doing a few of them gets you at least an hour of underwater runtime. Doing all of them hopefully gets you more.

Originally Posted by JesseK

If you did a single motor design, it's easy to encapsulate that into a watertight container.

The really tricky thing is we're going for a biomimetic swimming design, so just rotary motion from a motor isn't terribly useful. We need to wiggle like a real fish. I really like your link to how to waterproof motors though.

Ultimately it looks like we're going to go with a design that only has hydraulic components outside of our watertight shell, so maybe I won't need to run electronics underwater after all!