No Name ROV

[Pilikia]

AHarris,

I appreciate your asking if I would mind you developing a similar design. I certainly do NOT mind. Please feel free.

In general, even though you are very polite and thoughtful to ask, I discourage you asking such questions. If someone feels protective of their designs, they should not post them in a public forum. They should copyright or patent them. I have no exclusive right to this idea. In fact, I stole it! Woods Hole has a side-scan sonar survey ROV that has the same basic configuration. I didn't ask them if I could use the idea. Suppose I asked, and they said, "NO!"? What would I do then? In general, just do it! If you feel indebted, a simple thank you or credit is sufficient.

A word about nomenclature: "ballast" refers to weight located low, near the keel, to help keep a vessel upright (and in ROVs to help manage buoyancy). In the case of this ROV, the batteries are located to serve as ballast. The upper hulls are empty, and provide flotation or positive buoyancy.

[Pilikia]

derilecte asked, "where did you get the clear dome?" Answer: http://www.surplusshed.com/pages/item/m1588p.html

I have ordered this dome, and it has been shipped, but hasn't yet arrived. Maybe later today it will. Before I ordered it, I emailed them the following questions, and they answered me with the responses I think I've set to display in blue letters:

1. Is the 5” dimension the inside diameter or the outside diameter? ID

2. You describe them as “thick.” What is the thickness of the dome wall? 3/16"

3. By “Optical” do you mean that when looking through the dome from the inside, there is no obvious distortion or waviness in what you see beyond the dome? YES

4. In the little photograph on your website, there appears to be a “lip” or thickening at the rim. Is that true? If so, how thick is that part? 1/4"

I suggest you wait until I get mine and can report on its suitability, before you order one.

[Pilikia]

derelicte, the optical acrylic dome arrived today. It was very well packaged with paper wrap, plastic bag, and 2 large sheets of bubblewrap, which was a good thing because the box was smashed all to hell.

It's true what was promised, the dome is very sturdy and optically very "clean," without distortions or waviness.

There was a very slight lip on the inside of the base, which prevented it from fitting over the end of the 4" coupling. I spent about a half hour sanding it off and easing the edges of the dome and the coupling. It still wouldn't quite fit over the coupling. I heated the dome in hot (not boiling) water, and it fit over the coupling! It still needs more sanding to get it to fit further down the sides of the coupling. I'd like to see a minimum of 1/4" overlap. Right now it is only about 1/8".

Anyway, compared to some other domes I bought, this thing is far better.

[thegadgetguy]

How deep would you say this dome might be good for?

[Pilikia]

thegadgetguy asks, "How deep would you say this dome might be good for?"

The short answer is I don't have the foggiest idea. Acrylic, like all polymers, can be made to have a wide range of physical properties. I have no idea the specs on this acrylic, and it probably wouldn't mean much to me if I knew. This acrylic is 75% the thickness of the 4" PVC. The domed shape is a natural for resisting external pressures. I'd be very surprised if this dome fails at less than 100 meters.

My guess is I'll discover some other factor, like the com wires of the tether, that will put a depth limit on the rig.

[bossfrog]

I'm still working on how to create the little dome shape I've shown, but it is just for improved hydrodynamics and irrelevant to the structural connection.

I was thinking that if you get rounded 2" end caps and drill them for the 3/4 struts that would give you the shape you are looking for. If the 3/4 T fitting is butted up against the end cap, it would be stronger and also make a better waterproof joint. I purchased the components yesterday and will try to take pictures and document what I'm building to add to the thread.

Larry

[Pilikia]

bossfrog,

I've seen endcaps that are much more rounded than others, but my local stores don't have them. Do you know of a source?

About butting the tee against the endcap for added support, that's a good idea that has one problem: To be able to replace the motors, that part of the tee needs to be threaded. And the threaded connection has to be cranked down good and tight or it'll leak. So, probably best the endcap not be allowed to interfere with that. The 3/4" pipe is really pretty stout. I think it'll be okay without additional support.

I definitely appreciate you being right-on with thoughtful suggestions.

--Pilikia

[bossfrog]

I got my rounded end caps at the local Home Depot store. I hadn't really considered replacing the motors when looking at the housings. Looks like I have some more research to do before I start building.

[Pilikia]

I've been working on a design for a little ~ 8" cube wooden box that opens up to be the control console for the ROV. The monitor is a 7" screen intended for video and rear-view display in vehicles. There's an 8-pole joystick for controlling the ROVs propulsion motors; and two 3-position toggle swiches, one for diving and surfacing, the other for operating the tilt of the cameras. In the rear portion of the box is a 12V motorcycle battery that powers the monitor and the control signals. The bottom of the monitor just clears the top of the battery as the lid closes.

[SoakedinVancouver]

The turtle is a nice touch!