I have a somewhat odd observation I’d like to bounce off all of you. I’m seeing extensive “pitting,” or texturing on the inside of an acrylic electronics tube enclosure. I’ve attached pictures here. The tube didn’t come like this, and I don’t think it has anything to do with the product itself (manufacturing, etc.).
Rather, I’m guessing something the enclosure was exposed to is causing this? We stored one of our vehicle indoors in a non-climate controlled area, in a very old, humid building. I’m almost wondering if this is some sort of fungal growth? Or some sort of growth? It seems to have spread and gotten worse . . .
Has anyone seen anything like this before? I assume the best course of action would be to replace the tube. The sub is watertight thus far, but I assume that once the pitting (or whatever it is) compromises the acrylic underneath the o-rings, we’d be in trouble.
I’ve experienced that too Zach and think it’s because I cleaned up the invariable grease marks with a cloth that had some residual methylated spirits (ethanol/methanol blend) on it. Apparently this is very bad for acrylic and causes the type of ‘crazing’ you have.
Not sure if any kind of alcohol or petroleum based product will do this but did later see a warning about this somewhere in the BlueROV docs and have since used warm soapy water to clean and no further problems.
For me the crazing doesnt penetrate very far so assume its just an asthetic issue. Great tip to double check where the o-rings seal against the acrilyc tube though and I vaccum test before each dive anyway just in case!
Thanks for your response, @BillyBudd! Very interesting that you experienced a similar issue. I don’t remember using any sort of alcohol on the tube - usually we simply wipe it down with a clean micro-fiber cloth. Tagging @m.williams just in case she knows about any other cleaning material that may have been applied.
If the issue is on the inside of the tube, have you tried opening the enclosure to see whether the surface is actually damaged, or if it’s some form of growth that can be wiped off?
If it is some form of fungus then it may also be a good time to recharge or replace your dessicant, since living things don’t tend to thrive in environments with minimal moisture…
The texturing inside the acrylic electronics enclosure can not be wiped off. I do believe we are due for exchanging of desiccant packets though! A possibly interesting note; this pitting only occurs inside the acrylic tube, not the acrylic dome where the camera is, which is good for us as the video quality isn’t affected.
Not sure if this is relevant but perhaps. I remember old clear acrylic snap on motorcycle helmet visors doing the same thing especially when left in the garage elements on the bike seat. So im thinking perhaps the tube being a sealed enclosure may not be anything contributing but maybe U.V. exposure is a factor combined with the tubes composition materials? Somebody that works in the injection mold field would be a great person to give some better insight.
That’s interesting @m.williams - I don’t have any on the dome, the outside nor any on the acrylic battery tube so maybe it wasnt the ethanol for me either (see here for warning about using solvents on acrylic though).
Now wondering if it was heat-related as the electronics enclosure quickly reaches around 65-70C. When I first starting using the BlueROV I didnt realise this and possible had it powered on out of the water for extended periods so maybe reached higher temperatures (which can also cause acrylic crazing). Now only have it powered briefly when out of the water and remove the vent to hopefully reduce the temp.
Hi all -
I’ve noted this too, and think it is primarily linked to heat exposure and maybe a bit of UV. Because the processes used to manufacture the dome and tube are different, the dome does indeed seem to be less susceptible.
Polycarbonate domes would not only be tougher, but more UV resistant as well (in the works!)
Great observations. The compounds between the two (dome&tube) are different im sure. The tube being directly above the heat source im thinking is likely a factor progressing its degradation. Something also i wonder is if warm capacitors vapor slightly and theres no where for the vapors to escape in that enclosure. They claim electrolytic caps contents corrosive to a degree. That combined with heat and U.V. might “cook it in” so to speak. Just shows the design challenges manufacturer face day in and day out just trying to bring to the consumer a product as good as it currently is. Always room for improvement no doubt.
Thanks everyone for your responses! This has been very informative. @tony-white, I marked your response as the solution as it seems like heat and UV are known drivers of these observations.
Follow-up question: do you have a sense of the temperature (or an approximate range of temperatures) at which this issue may arise? I ask, as it’s sometimes convenient to leave our ROV locked in a vessel. Depending on the time of year, it can get quite toasty in a locked vessel cabin . . .
Many Thanks Also Zach - I always assumed this must have been due to contamination with a solvent (only several small patches in my case) so really appreciate your group’s feedback!
Tony once mentioned the phenomenon of ‘heat cycling’ that can cause cracks in plastics - not sure if this is relevant to the acrylic tubes but guess it might be?
I think what happens here is when plastic components with metal screws/fittings are heated and cooled repeatedly the different thermal properties can cause cracking of the plastics. Presumably this would be severe when taking a ‘hot’ ROV and dropping it in the water. So I never expose mine to direct sunlight out of the water and only store the ROVs in a cool dry place with a consistent temperature (ie basement without AC) and ensure they dont warm up too much in the field before deploying…
