This is the first attempt at blowing an acrylic dome for the front of the ROV that houses the main camera.
It might have been sufficient to use a flat sheet of acrylic but the viewing angles would have been greatly reduced, so a dome is preferable.
There will be a tilt and pan camera mounted behind the dome to give the best viewing angles.
The hope is to gas compensate the ROV to 100 PSI, to pressurise it with air so the pressure from the water outside the unit when at the operating depth won’t damage the camera.
While working at a depth of 30m this should also allow enough air to fill lift bags to float the catch back to the operator. It would also ensure no water enters the ROV and will also show any leaks immediately on the surface.
It would also be possible to connect the ROV up to a small diving cylinder with a variable regulator set to +50 PSI. With a safety/dump valve the ROV could dive to depths of 1000 metres. Dive cylinders are rated to 200 bar or 2000m filling the 7 litres of the ROV.
Dome Blowing:
- Heating a square of acrylic in the oven.
- Clamping it down over an air inlet and inflating it till it forms a dome.
- Reinforcing ring formed by cutting out the centre from a 140mm bicycle brake disk- 3mm stainless.
- Air injected with the regulator on the compressor by slowly turning it up.
The first run. c
I used a section of tractor inner-tube for the air inlet and cut out the bit with the Schrader valve. I then screwed the reinforcing ring down through the rubber and into the board bellow with self tapping screws.
This method worked but the time taken to screw the ring down allowed the acrylic to cool a lot and didn’t reliably seal the dome.
Next I converted my hydraulic pipe bender into a press, with the same section of inner tube as with the first attempt and a 110mm Upvc pipe joint over.
Doing this it was possible to quickly seal the acrylic over the air inlet. Visibility was reduced and the dome touched the height gauge which flawed the dome.
Next I hope to get a better idea of the oven temperature – by inserting a digital thermometer.
Using a laser pointer as a height gauge, I will install a small light in the dome forming chamber and increase the pressure more gradually.
The best dome so far is still a bit wonky it will probably distort the image too much. It’s made from 8mm acrylic.
Pressure testing:
The first dome was off the shelf 3mm acrylic. It didn’t withstand the pressure test. It might have been safer to test with it filled with water.
The second test with the 8mm acrylic dome was successful:)
I would also like to test the idea of using an OpenROV style etube ( transparent acrylic tube with o-ring seals). Connected to the front of the housing with tank connectors and tubing.
This approach would be easier to install on the housing and would reduce the impact on its structure- no large hole or screws. Possibly making the ROV stronger. The endcaps of the etube would need to be bolted together so the tube could be pressurised.
spam filter good
dam right. If this works- I got the message: “ERROR You chose the wrong image solution for the security challenge, please read the instructions and try again.” I guess because I didn’t drag a seed to the flower pot. I am starting to think the bubbling was because all the numbers had rubbed off the oven controls and the temp was to high? Would like to install the digital thermometer.
Looking good.