Bennachie wrote:You could... but as you plan to go to about 70 feet depth, the external pressure on the o-ring will be just over 2 atmospheres, or about 30psi above the that inside the hull. There's a good chance your o-ring would not withstand that and it would just pop inside the hull. You could add a lip just inside the hull to stop the o-ring slipping in, or even better, get a groove machined into the flange to take the o-ring.
If you don't machine a groove you also risk breaking the dome by over tightening the bolts. The best and probably easiest solution is to buy a small sheet of fluorosilicone and cut a gasket.
*Edit* I t looks like you don't have room to machine a groove so that leaves adding a lip or making a gasket.
Boy, you really seem to know your stuff! Adding a lip probably wouldn't work well for me, since there's only a 1/4" to play with between the screw holes and the beveled inner surface of the toilet flange. I'll look into buying a sheet of fluorosilicone and cut a gasket. There's a couple of suppliers in my area. Hopefully I can buy a small quantity from one of them.
By the way: when I started building my ROV, I thought to myself "If I build it myself, I can save a lot of money". LOL. Not true. Well, it's been a lot of fun building it myself (and tackling the engineering challenges along the way). So I don't regret the journey!
...there's only a 1/4" to play with between the screw holes and the beveled inner surface of the toilet flange.
I hadn't noticed the bevel until you pointed it out. You could possibly add the lip to the inside of the flange, but you'd have to profile it to match the bevel and bond it to that. Probably rather more work than it's worth.
Boy, you really seem to know your stuff!
I've been working with ROVs for the last twenty years. Currently I'm part of a team supporting a fleet of work class and observation class ROVs, so I may have picked up a few handy bits of info along the way
I called around to a few local places near me. One of them said they couldn't supply me with fluorosilicone (they had a minimum order of $200 for pieces of it!), and because it's so expensive, they don't really have small leftover pieces floating around their warehouse.
But the sales guy I spoke to was interested in hearing more about what I was doing and why I needed fluorosilicone. After I told him, he suggested some cheaper alternatives. These are fairly pliable products (compared to the stiff rubber gasket I had previously made), and may fit my needs, he said. As a bonus, he also said a 5" square piece x 1/4" thick would probably be very cheap to buy (if not a free sample).
Well, it's been a lot of fun building it myself (and tackling the engineering challenges along the way). So I don't regret the journey!
