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​Waterproofing problems

A project log for OSUG: Open-Source Underwater Glider

A versatile autonomous environmental drone using a buoyancy engine

alexwalexw 06/09/2017 at 10:091 Comment

The current state of the glider is not capable of performing underwater testing (It’s likely to currently be IP66 rated without sealants, i.e. very much not sufficiently sealed). The poor performance is due to a mixture of design flaws and fabrication difficulties. For instance, the design uses multiple o-rings where fewer would suffice, increasing the chance of failure. Moreover, the dimensions of the printed o-ring grooves vary by minute amounts between test prints, making it hard to produce reliable seals as the grooves between layers allows water to pass through.

To solve this issue, I am currently I am looking at purchasing a watertight enclosure (above, but with a custom length tube) from BlueRobotics. All of their hardware has been purposefully designed to withstand underwater conditions for ROVs and the enclosure I am looking at purchasing is rated to a 100m depth. The enclosure and associated parts are relatively affordable compared to commercial solutions, however they are expensive enough that they could put off hobbyists looking to build the glider (The order I am looking at placing is ~$500 including shipping to the UK). I feel like this is justified to produce a working prototype more quickly, with effort spent on getting to a stage where I can demonstrate underwater movement, rather than spending time on producing a watertight enclosure. In the longer term, I will revisit the printed endcaps, to reduce the cost and to increase accessibility to the design, using the Blue Robotics endcaps as a drop in option for those without access to a printer of a high enough quality to produce watertight seals or those wanting to go to a greater depth.

Once I have recieved the parts, I will post an update showing the parts I have purchased (I’m still finalising the order) and any thoughts I have concerning the enclosure.

Discussions

` wrote 08/16/2017 at 15:02 point

To create sealable endcaps, you may just need a printer with a polar axis--a radial axis (or X-Y, and use Y=r and X=0) over a rotating bed. Build up layers using rings of constant radius. That would eliminate stairstepping on the O-ring tracks.

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