Waterproofing motors


#1

I’ve just seen that the steps to waterproofing the motors have been added to the wiki, but from reading and looking at pictures I don’t understand why all that is needed.
I mean, desoldering cables, resoldering other cables: isn’t applying liquid tape on top of the existing ones and putting heatsink on them enough?

Simone


#2

It might be, but we've been happy with this process.

You'll need to solder on longer cables, regardless. And if you're soldering, better to have only one point of connection, and this process ensures that the connection is protected (because of liquid electrical tape).

Make sense?


#3

Yeah, agreed on having the long cables that have just one connection exposed and the other in the sealed box.

Now just need to find were to buy in Europe the electrical liquid tape. In EU DIY is much less professional than in the US and all those things are difficult to buy if you are a private person and not a professional worker. :)

btw: I've fixed the numbering on the wiki


#4

I saw that - thank you!!

And the DIY options here aren't as good as they are in Shenzhen (they take a lot longer at least). Alas.


#5

Also keep in mind that water can travel up that stranded wire so it's very important that your solder joint "fills" the wire and that water cant touch the strands on the ROV side of the solder joint.

If you just attached those wires together with no waterproofing and went deep underwater, water could go right through your wire like a straw and fill your electronics compartment.


#6

Yeah, that's an issue I think may come up with deep dives. In our 20m dive at NEEMO, we didn't experience any leakage, but the guys at BC Robotics in Canada said the experienced some leakage at 50ft from an unknown source and suspected that it might be this effect (which I think is called "hosing") At any rate, I think it would be good to do some experimentation with this and see 1) What conditions cause it to happen and 2) what the most simple but effective ways to fix it are.

Let us know your thoughts!

E


#7

It can happen anytime, all it takes is a nick or cut in the insulation and, due to the capillary effect, water can penetrate several inches along the individual strands of wire, even at or close to sea level.

An easy fix for that could be to strip all wires for a short length, right where they transition the discs, before they get potted. That way, the epoxy can wrap around the individual wires instead of the insulation.Given that the epoxy isn't electrically conductive, of course.

Another option would be to drill individual holes for all the wires, instead of one big hole, then inserting and potting in place a short piece of solid copper wire each, as a pass-through, then you can solder on your wires on both sides of the discs, heat-shrink and/or liquid-tape your connections and not worry about internal leaks from your wires.


#8

I used the first method you described in one of my end caps but was frustrated at how tedious it was to strip off insulation off of so many wires, then keep them from shorting with each other as I potted everything. Perhaps kind of combining your first idea with your second and making a simple laser-cut guide that separates the stripped wires from each other would be the way to go. Hmm....


#9

I concur, it is tedious and, giving it more thought, here is another way: strip the individual wires- fairly close to the penetration point -, solder the strands together and then heat-shrink that area. That also creates a waterproof seal, wouldn't be as pretty however.

I've heard of people who inject epoxy or silicone into the cables somehow to fill the air gaps, similar to direct burial Cat5 which has some kind of goop in it. Too bad it's so stiff, might make for a decent tether for a bigger ROV though...


#10

HI Simone

Maybe this wil help you.

http://www.plastidip-shop.de/index.php/produkte/fluessigisolation.html

Cheers

Tobi


#11

Thank you.

It charges 15Euro for shipping to Belgium... for a 20Euro product that weights less than half kilo... looks a bit too much as shipping cost :)

But thank you anyway

Simone


#12

Hi

THats much

http://www.classicinternational.eu/plastidip/electronica-toepassingen/liquid-electrical-tape/?ba=true&bal=3080811&bac=1

will cost 25 Euros

In Hasselt (think thats Belgium) try caracrs or minishop, found that shops in a cartuning forum.

Cheers

Tobi


#13

Thx... will try those

Simone