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!
Acrylic/aluminum hull problems
- puzzler300
- Posts: 55
- Joined: Jan 2nd, 2013, 12:26 pm
- Location: St. Cloud, Mn
Acrylic/aluminum hull problems
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- 12722451_928970360483685_664056920_o.jpg (338.04 KiB) Viewed 7069 times
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- Bathtub test, looking good!
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- 12' (3.6m) depth test, not so good.
(Kudos to the swim team for letting me test in their pool) - 12768101_928970447150343_1006197478_o.jpg (99.33 KiB) Viewed 7069 times
- 12' (3.6m) depth test, not so good.
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- Complete end assembly. Aluminum cap + bracket + o-ring
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- The aluminum cap
- 12787081_928987593815295_494889958_o.jpg (284.29 KiB) Viewed 7069 times
- puzzler300
- Posts: 55
- Joined: Jan 2nd, 2013, 12:26 pm
- Location: St. Cloud, Mn
Re: Acrylic/aluminum hull problems
I'm adding a CAD drawing that might help clarify what how the tube end works
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Re: Acrylic/aluminum hull problems
To start, I have no experience and yet to even start building.
How straight are the cut ends? How did you prep them?
How straight are the cut ends? How did you prep them?
- puzzler300
- Posts: 55
- Joined: Jan 2nd, 2013, 12:26 pm
- Location: St. Cloud, Mn
Re: Acrylic/aluminum hull problems
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
--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
- TigerShark
- Posts: 108
- Joined: Jan 7th, 2014, 2:43 pm
- Location: Washington State
Re: Acrylic/aluminum hull problems
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.
- puzzler300
- Posts: 55
- Joined: Jan 2nd, 2013, 12:26 pm
- Location: St. Cloud, Mn
Re: Acrylic/aluminum hull problems
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?
--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?
- TigerShark
- Posts: 108
- Joined: Jan 7th, 2014, 2:43 pm
- Location: Washington State
Re: Acrylic/aluminum hull problems
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
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
- puzzler300
- Posts: 55
- Joined: Jan 2nd, 2013, 12:26 pm
- Location: St. Cloud, Mn
Re: Acrylic/aluminum hull problems
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.
Also, do you think plain threaded rod will work? I'm mostly worried about corrosion.
- TigerShark
- Posts: 108
- Joined: Jan 7th, 2014, 2:43 pm
- Location: Washington State
Re: Acrylic/aluminum hull problems
Here is how my end cap seals:
I think your rods would be fine but I would use SS or Brass. You could thread just the ends of solid rod.
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.