Design options 5 DoF hydraulic arm for submersible Gold Mining Operation 10-30 Meter depth

Beginner here seeking advice or direction re: Outcome Desired: design for remote operated, underwater hydraulic arm for Gold Dredge business, maximum depth 10-30 meters, Job: moving, grasping, scraping, relocating rocks (3-8 inch diameter/ max 20kg) and bottom sediments, continuous operation 24/7. Arm operator on surface support vessel. I am a technically proficient fabricator with 3-D modeling and CAD (Fusion 360), and chemical engineering. Limited mechanical engin. exp. Any guidance would be greatly appreciated, on various approaches to achieve the desired Outcome i.e. a remote operated manipulator arm that can move sediments, rocks, etc. for a Gold dredge at minimal depth. Ive looked at commercial arms, but they are very expensive and I dont see any major technical obstacels to fabricating one myself. Problem is I have VERY limited experience with the available tech, parts and systems. Just need a starting point. Thank you very much in advance for assistance. Michael Hyder

@BeachBum Welcome to the RobotShop Community.

I’ve looked at commercial arms, but they are very expensive and I dont see any major technical obstacles to fabricating one myself

“Problem is I have VERY limited experience with the available tech, parts and systems”

That kind of seems like an obstacle. Consider that the cost of a commercial product is not just the sum of its parts, but also margin they have to make, as well as offset the significant R&D cost which went into developing the product in order to ensure it works to spec. Beyond that, if they decide to manufacture in-house, there’s the cost of the machinery etc. Even worse is that these are not “mass market”, so they need to recoup their money on just a small number of units.

Operating hydraulics on the surface (on land) is one thing, but something completely different underwater and at up to 30m depths. If it’s salt water, it has to be fully protected from corrosion (every exposed part including hydraulic lines, seals etc) need to be rated for 30m. There also needs to be a power source and electronics at that depth too. Last, unlike an ROV, the setup needs to be protected from sediment clogging or impeding motion (dredging as opposed to simply exploring).

As such, can’t say I envision it as an easy project, especially one on a budget and with limited experience. The starting point would be to come up with a design, then research the equipment needed which are rated for salt water and 30m depth. You may end up spending significantly more time in development (time = money) and prototype costs than it would have taken to buy a ready to use unit.