Homebuilt ROVs Forum

Hi all,

I've been working on building a hull for my electronics. This is my 3rd iteration, and the one I'm most confident about. I'm working on the primary housing --housing my camera, batteries, and Arduino-- and so far it looked like it was going pretty well.

It's primarily made out of a 3" (76.2mm) ID 3.5" (88.9mm) OD acrylic tube. The ends are machined aluminum with 2 3" (76.2mm) ID 3.5" (88.9mm) OD o-rings, one on each end. The white brackets on the ends serve only to hold the end caps in place by means of four threaded rods. I tested it in my bathtub just to make sure the idea wasn't fundamentally flawed and that worked really well, actually. I took a trip to the pool at my university and threw it in the deep end and I'd say it lasted 6' (1.8m) before it started leaking.

I feel pretty stumped as to where to go from here. Any input would be greatly appreciated!

I'm adding a CAD drawing that might help clarify what how the tube end works

To start, I have no experience and yet to even start building.

How straight are the cut ends? How did you prep them?

Approximately straight? I haven't done anything to it. I bought it off McMaster Carr and just left it. Definitely has saw marks on the ends, no idea the depth, but I can feel them. I want to put it in a lathe and face it, but I also don't want to shatter it (if it isn't evident, I have no idea how to work with acrylic).

--edit--
I found this video: https://www.youtube.com/watch?v=QhAXbA2lmnE and I think I'll try the sander + buffing wheel tomorrow and test it one more time.

I'll post results

Clean those ends up and that might work. You could swirl it on fine sandpaper over a very flat surface. Also you might need more compression.

Sounds good, I tightened it today until it sounded like the ABS was cracking, but I might try a bit more.

--edit--

I've stripped out the threads on my aluminum threaded rod, any good places to get threaded stainless rod?

Also, has anyone tried silicon grease on their o-rings to help with sealing?

You also shouldn't need to get it that tight. You definitely need to use some grease. I use vasoline. Just a little to moisten the o-ring. You have to keep the area very clean also. I think if you had a part of the end cap that extended into the tube that would work better. I have double O-rings on my setup. One with a seal inside the tube and one seals on the end of the tube. You have to think where is the o-ring going to go when water pressure is squeezing it? I think yours would likely get pushed inside with your current design if you take it too deep.

Home Depot should have threaded rod. You could also get unthreaded and use a die to thread just the ends which would be stronger. You can also order it from Mcmastercarr.com or onlinemetals.com

I was thinking the easiest thing to do would be to re-machine the aluminum caps with a taller center piece, or deeper o-ring grooves. Is there any advantage to the double o-ring system other than redundancy?

Also, do you think plain threaded rod will work? I'm mostly worried about corrosion.

Here is how my end cap seals: This works for me, I have never had an issue with this design.

I think your rods would be fine but I would use SS or Brass. You could thread just the ends of solid rod.