Homebuilt ROVs Forum

Aloha!

I have been MIA from this forum for some months, my attentions diverted to projects that actually put food on the table. But, IIIIIIIIIIIII'm Baaaaaaaack!
In the workshop of my imagination, there have been several revisions to my earlier plans:

1. Someone on this forum mentioned they were using 2 vertical thrusters, the faster to dive to depth and to resurface. This struck me as a fine idea, and I incorporated it in the attached project. I have a little trepidation about it. I'm not sure I've located the vertical pair of thrusters such that the lifting or diving workload is divided equally between them. I imagine if it's not equally divided the whole thing may veer off this way or that. We'll see. I think I have them located to be pretty equal.

2. Another change is switching from the Rule thruster motors to the Johnsons. The Rule's wires emerge from the side of the motor housing; The Johnson's wires emerge from the rear of the motor housing. The big difference this makes is the Johnson wires can be kept entirely dry, and require no hull penetrations. It requires cutting those funny fins off the Johnson, and grinding off the raised lettering on the otherwise flat shoulder at the rear of the housing. Then, a short piece of 2" PVC sch. 40 fits nice and snug on that shoulder, ready for a good epoxy glue job. On its other end, standard fittings can be used to neck it down to integrate into the frame.

I really like having all the motor wiring completely internal. Now the only hull penetration is for the tether cables. The risk of leaks is greatly lessened.

3. Before, I was planning on using a large threaded plug at the aft end of the main hull for access to the battery packs and relays. That plan made it both difficult to work on and in serious danger of leaking. That plan also envisioned the cameras in their own housings, outside of the hulls.

The revised plan puts the cameras inside the main hull, capped with a 3/16" thick "optical" acrylic dome that fits snugly over the 4" (nominal) straight connector (5" OD) at the fore end of the main hull. There is a special adhesive for bonding acrylic to PVC. Access to the main hull is now a lathe-turned fitted joint that uses both the thickness of the pipe hull and the thickness of a straight connector over it to accomodate an O-ring seal that is drawn tight with 4 adjustable draw clamps. The joint is located to provide easy access to the cameras, the tilt servo, the relays, and the charging wires for the battery packs.

Well, I've already rattled on enough to put you to sleep. You can track these changes in the following illustrations:

that looks really great!

what program did you use to render it?

could you please elaborate on your motor mounts? they look cleaner than the 1.5" pipe clamps I used for the bilge pump cartridges.

also, I like you light mounts, but I'd be worried that if you bump into something with them it would move their alignment.

Wow, I really like your project. I'm going to have to rethink my project and maybe incorporate some of your ideas. Luckily, I'm still in the planning stages and acquiring the parts so it wouldn't be too hard change.

derelicte, thank you for your kind words.

The 3D model was created in SketchUp, a FREE Cad program from Google. All of the images except the one with black background are screen shots taken in SketchUp. The rendering (first image) was made in Kerkythea, also a FREE program. Kerkythea has a SketchUp plug-in that creates a file of the SketchUp model that the Kerkythea program can use. These two programs work together very nicely. They both have a bit of a learning curve, but they also have good Help and tutorials.

About the motor mounts, assuming you understood the explanation of how to attach a short piece of 2" PVC to the back end of the motor, the next step (in my case) is to reduce the 2" down to 3/4". There is a type of bushing (called "Spigot x Slip") which slips inside the 2" pipe, and has a hole at its center that receives a 3/4" pipe. These are available at http://www.plumbingsupply.com/pvc.html#bush. 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.

[8/24/2011 edit: I've just received the "spigot x slip" fittings. I had misunderstood the description. The fitting does not fit inside the 2" pipe, but rather is the same OD as the 2" pipe, so a straight connector sleeve is required. It'll work fine . . . just a more weight.]

About the lights sticking up just asking for trouble, in most underwater environments they will be no problem. The reason they stick up is to get as much separation as possible between the cameras and the lights. This is preferred because from the cameras' angle of view, it decreases the amount of "snow" (suspended debris in the water) that is illuminated by the lights, making for much better pics and video. In situations like exploring a shipwreck or a lava tube, the lights can be mounted on the underside of the of the upper hulls, so they hang down and are close to the cameras. These lights have their own internal batteries, so there are no wires to fret over. There are little "z"-shaped clips (not shown) attached to the hulls that hold the light supports. This lower mounting is not near as good a position, but sometimes necessary.

8/20/2011 edit:

The z-clips are now added. Attached shows lights in the lower position for navigating tight places.

That certainly looks like a fine machine! I can't wait to see it operational, if only I could get the materials and then my mind too would be running wild.
Good luck with the project, she looks great... if not very expensive!
How much are you planning to spend, if you don't mind me asking?

AHarris, thanks for the positive feedback.

At this point I've probably spent more money on parts that I've since decided not to use than on parts I will use. I'm not sure how to avoid that. Ideas evolve.

Looking at the basics: PVC pipe & fittings, batteries, motors, cameras, servos, Ethernet cables, joystick, switches, relays, solvent, epoxy, paint, and a lot of miscellaneous . . . it's in the vicinity of $1000.

As hobbies go, it's really cheap!

Are all the parts you using "off the shelf" or are any of them being custom made?

AHarris asks, "Are all the parts you [are] using "off the shelf" or are any of them being custom made?" Hmmm . . . Well, of course the entire thing is custom made by me. Some components, such as the motors, are off-the-shelf but modified by me, as discussed near the top of this page. Some components, such as the cages around the props, are fabricated from scratch by me (so far, I haven't found a suitable off-the-shelf version). The lathe turning of the O-ring connection of the main hull is being farmed out to a machinist with a lathe that can chuck 5" diameters.

Also, some components are off-the-shelf but unusual, such as the "saddle tees," discussed in the forum entry "Attaching Struts to Hulls" in the "Frames, Hulls, & Buoyancy" section of "On the Bench."

If you see other components you are curious about, feel free to ask how and where I am sourcing them.

Thanks for the information and also that grammatical error you picked up om, just like to say again how much I love the design. If you don't mind, I may use your "sling" method of having the main housing which contains the majority of the weight and the ballasts above it.
When you see it on paper, you realise how important weight distribution is. I now have realised that in combination with currents and waves, mine probably shall role.
Thanks for sharing your design with us, you probably saved my ROV! As I say, if you don't mind I may use a similar shape?

where did you get the clear dome?