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View Full Version : Suggestions on joining thruster wires in marine environment (underwater)



Ken Gracey
03-09-2012, 04:33 AM
Hey all,

Working on a new project in my free time. I expect to build a robotic, solar-powered, GPS-guided cataraft that can cross Lake Tahoe (29 miles). I'll be using the Crustcrawler HF-400 thrusters (thanks Alex!). This isn't Parallax official business, so just pretend I'm anonymous. One of my jobs is to pave the way for timid forum lurkers.

One of the first challenges is dealing with these thruster wires. They're a stiff 14 AWG wire and I don't have much to work with here - got to get it right the first time. Crustcrawler recommends a soldered, heat-shrinked connection.I need to add about four to five feet of wire to these motors to get the signals from the control system.

What's the best way to deal with these? Put on automotive butt connectors and heat-shrink the whole setup? 3.5 mm hobby bullet connectors with heat-shrink? Solder and heat-shrink with no connectors? Should I be throwing any glue into the heat-shrink tubing?

Looking forward to some input. I see another forum member is building an autonomous craft as well, so I'm in good company.

Thanks,

Ken Gracey

P.S. I'm only taking a break from quadcopters, I promise!

90397

90398

kwinn
03-09-2012, 05:06 AM
I repaired a broken power cable on my submersible well pump by soldering an inch or so of the wires together, putting silicone sealant (food grade) around the copper and a bit of the insulation, then heat shrink tubing over that. It was still working 4 years later when I sold the place.

Phil Pilgrim (PhiPi)
03-09-2012, 05:18 AM
Ken,

Marine-grade heatshrink tubing has heat-activated goo inside that forms a seal around the wires as it shrinks. I don't know what its depth rating is, though. If you can't get it where you are and want to try it, I could send you an assortment.

-Phil

jim N8RHQ
03-09-2012, 05:20 AM
I've had good experiences with the Deutsch connectors in wet environments with smaller wires running mostly 12v signal lamps and 5v sensors, but i see their size range includes up to 100A.
http://www.farnell.com/datasheets/628276.pdf
http://www.newark.com/jsp/search/browse.jsp?N=201861+2203&Ntk=PLS_MAN_BRAND_NAME&Ntt=Deutsch&Ntx=

Ttailspin
03-09-2012, 05:31 AM
West Marine (http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=35701&catalogId=10001&langId=-1&storeId=11151&storeNum=50523&subdeptNum=50566&classNum=50568) has good stuff, I think you have one right there in Rocklin...:thumb:
What a cool project Ken.

-Tommy

Peter KG6LSE
03-09-2012, 05:45 AM
I have made some UW SCUBA lights back when I was In LA cali ..
The way I sealed wires was with PVC cement and pvc tubing .. Like 1/4 tubing .the cement mates with PVC wire like a champ .
the Same apply with buttyl rubber and wetsuit cement .

a solvent bond where tthe solvent Welds the materials togheter Should be good ..

the other issue is what is the depth . if its a static load then some vasoline will be OK . it cant be compresed . and it excudes water . for my lights i used BNCs that Before I dove I jammed the jelly In both connectors before I mated them .
the lights lasted for 4 years . .

peter

W9GFO
03-09-2012, 05:49 AM
Unless the cataraft is going to be in the water for extended periods, I wouldn't worry about it. I would solder and heat shrink as normal, then maybe add a longer heat shrink with some silicone or hot glue to keep water from seeping in - but that is most likely not at all necessary.

bill190
03-09-2012, 06:15 AM
Electrical connectors on trucks underneath are bombarded by water. For these they apply "dielectric grease" (sold in automotive stores). Keeps those electrical connections working in a wet environment. I don't know about underwater?

90400


More...
http://www.dielectricgrease.org/

WBA Consulting
03-09-2012, 09:03 AM
Soldered connection (lap style joint) or crimp a high quality butt splice connector (Molex Avikrimp series as an example, Avnet has P/N 0192000001 (http://www.molex.com/molex/products/datasheet.jsp?part=active/0192000001_SPLICES.xml)for 10 cents each), then seal with two layers of glue-shrink. I would recommend 3M EPS300 Heat Shrink Thin Wall Adhesive Lined Tubing (http://solutions.3m.com/wps/portal/3M/en_US/Aerospace/Aircraft/Prod_Info/Prod_Catalog/?PC_7_RJH9U5230GE3E02LECIE20SOG5000000_nid=GSPD68S 1WNgsQS60V5THXRglGSBW5VPWRNbl)as it is more flexible than most glue-shrink.

Loopy Byteloose
03-09-2012, 10:54 AM
First and foremost, a marine maritime (saltwater) environment is far more hostile than fresh water. I'd would not even venture to make a high current connection for immersion in salt water. I'd just pull new wire from a dry enclosure to another sealed dry enclosure.

But Lake Tahoe is nice fresh water, so you should not have too much trouble.

Other than that, I have had very good luck with connecting 110VAC underground cable that was broken by a gardener by using ordinary wire nuts, copious silicone, and ample shrink wrap around all leads. Not sure how long it lasted as I wasn't the homeowner, but they never mentioned again for many, many years.

Upon occasion, I have worked on dockside boat carpentry in salt water. and if a 110VAC extension cord drops into the water with the slightest nick in it or at the plug, it starts to bubble from conduction to ground. It doesn't take long for it to eat away at enough copper or brass to destroy the wire at the nick or the plug in.

Soldering is always better than so-called high resistance connectors as dampness is going to corrode the connectors far faster than a solder joint if it ever gets in. If you need a disconnect, consider placing it in a dry location and consider your task to be a submersible splice.

ajward
03-09-2012, 11:06 AM
Hey all,

Working on a new project in my free time. I expect to build a robotic, solar-powered, GPS-guided cataraft that can cross Lake Tahoe (29 miles). I'll be using the Crustcrawler HF-400 thrusters (thanks Alex!). This isn't Parallax official business, so just pretend I'm anonymous. One of my jobs is to pave the way for timid forum lurkers.

One of the first challenges is dealing with these thruster wires. They're a stiff 14 AWG wire and I don't have much to work with here - got to get it right the first time. Crustcrawler recommends a soldered, heat-shrinked connection.I need to add about four to five feet of wire to these motors to get the signals from the control system.

What's the best way to deal with these? Put on automotive butt connectors and heat-shrink the whole setup? 3.5 mm hobby bullet connectors with heat-shrink? Solder and heat-shrink with no connectors? Should I be throwing any glue into the heat-shrink tubing?

Looking forward to some input. I see another forum member is building an autonomous craft as well, so I'm in good company.

Thanks,

Ken Gracey

P.S. I'm only taking a break from quadcopters, I promise!


Cool! An aircraft carrier for quad copters? :smile:

"Turn into the wind and prepare to launch!"

@

idbruce
03-09-2012, 11:28 AM
Ken

DISCLAIMER - The following recommendation is an untested conjecture.

As you already know, corrosion is going to be your worst enemy, so a very solid connection is of the utmost importance. Without any doubt, thoroughly solder the wires together instead of relying on a butt connector for your connections. Once you have a solid connection, protect it. Depending upon the current draw, motor wires can get quite warm, so wipe High-Temp RTV Silicone all around the solder joints and allow it to cure for several days. After the RTV has fully cured, cover it with small pieces of heat shrink tubing. To further insure a dependable connection, I would then add RTV around the heat shrink ends and allow this application of RTV to also fully cure, and then add another layer of heat shrink.

Not that I am an expert, but this is the way I would do it, and I think it would give you very adequate protection for a marine environment, both above and below water level.

Bruce

jdolecki
03-09-2012, 01:07 PM
Ken did you ever get that surface robot from ebay?

If you want to go underwater try this

http://www.ebay.com/itm/SeaRover-by-Benthos-Remote-Operated-Vehicle-ROV-Submarine-Univ-of-Michigan-/290677503530?pt=BI_Robotics&hash=item43adbab62a

mindrobots
03-09-2012, 01:34 PM
First off, welcome to the Forums, Ken Nonymous!

I don't have an answer for your but I'm puzzled by the responses. I thought the learned opinion on the forums a while back was that crimped connections were better than soldered connections. In this case, crimped connections with non-corrosive goo and adhesive shrink wrap would be the bestest!

Hope this doesn't cause a firestorm of debate around your project.

idbruce
03-09-2012, 02:14 PM
In this case, crimped connections with non-corrosive goo and adhesive shrink wrap would be the bestest!

Hope this doesn't cause a firestorm of debate around your project.


:) :) :)

Rick

HMMMM.....



I thought the learned opinion on the forums a while back was that crimped connections were better than soldered connections.


I would have to disagree with this opinion. Thoughout my life, I have removed many crimped connections due to corrosion and inadequate contact, but I never had to desolder two wires that were properly soldered together.

Bruce

Cluso99
03-09-2012, 03:49 PM
Ken: As Phil said, there is heatshrink with embedded resin. It requires a heat gun as it shrinks at a much hotter temp. There are also joiner crimps with heatshrink with resin. Solder is fine so long as the current isnt too large that it may heat and melt. Do not use spade connectors as the heatshrink with resin does not shrink as much. I have wired 8 35ft cats including my own. They are in survey and salt water - I use joiner crimps with resin heatshrink for up to 10A. These come in one piece and are blue for 4awg and red for 6awg. Soldering iis fine too. In oz the major electrical wholesalers carry both though I have not seen them in marine stores. Unfortunately all my leftovers are interstate and I am not going up for a while or I would post you some. If you cannot find it let me know and I will chase it down here.
BTW ensure the resin just oozes out the ends all around the cable.

Ken Gracey
03-09-2012, 04:41 PM
Hey all,

What a unique arrangement these forums provide for the lazy, like myself. Before I fell asleep I was able to scratch a message into the forums. When I awoke I harvested tons of replies and sorted out the ones that I want to use! Now I'm anxious to post my next question to the buoyancy experts, then another one for the solar/power budget gurus, and another one for the programmers. Thank you to everybody who has given me the time.

@jdolecki - that ROV on eBay didn't sell so I sent them an offer but there was no reply. It would've been the perfect chassis for my project, too. That UMich robot you found on eBay looks like a great opportunity to inherit somebody else's project. There's a lifetime of work in that robot for somebody (not me)!

@ajward - launching a quadcopter off of this craft certainly came to mind, but knowing what I don't know certainly provides cause for me to minimize risk. I can't set sail with more hardware than I'm willing to loose :). I should be able to take away several quadcopter lessons and apply them to this project.

I just did a forum search and I've been sitting on this project since 2010 - I should have answered Bruce's thread about unfinished projects. I think I've been obsessing over wire connections for two years.

Looking more into the requirements, my test environment is a very fresh lake (oligotrophic - mostly free of nutrients and especially corrosive salts). And the duration of exposure is probably a dozen hours a time if I'm remotely successful. Therefore, I called up the local Napa auto parts and found out that they stock some marine grade heatshrink tubing. I'll do a soldered lap joint and then cover it with the marine-grade heatshrink.

Will return with a bit more progress, in another thread.

Thanks everybody!

Ken Gracey

tim1986
03-09-2012, 09:59 PM
Hey Ken, I love the idea for your project! You might want to try Sugru. It's a silicone putty that air dries overnight and costs about $20 for about 60g. It comes in 12 small packs. http://sugru.com/

(http://sugru.com/)-Tim Ballas

WBA Consulting
03-10-2012, 06:07 AM
That's nice having a solution in the neighborhood! If you happen to take the week off and get it finished at lightning speed :tongue:, bring it to the polar bear plunge (http://tinyurl.com/6ublggx) this Saturday!

(Hi Tim!)

Loopy Byteloose
03-10-2012, 07:22 AM
I learned something new - marine grade heatshrink is available with some sort of internal sealant.

Since many places salt their roads in the winter, this might just find a niche in my items to have on hand.

Paul K.
03-10-2012, 08:03 AM
Plasti Dip might work. I'd scuff up the wiring first.

Cluso99
03-10-2012, 10:27 AM
If that is all you require Ken, just a silicone blob over the soldered wires covering the insulation as well would be fine.

Agreed this forum is great for inquiring about various solutions.

idbruce
03-10-2012, 02:27 PM
Ken

I imagine these wires will be underwater.

If you have not already soldered your wires together, there is one other thing that you might want to consider. I am almost certain that the insulation for the thruster wires is water resistant, however when selecting wires for your extension cables, select wire with an insulation that has a high degree of water resistance.

Bruce

EDIT: I have not checked the properties, but I imagine stranded THHN wire would be a good choice.

idbruce
03-10-2012, 02:37 PM
Ken

I was wrong about THHN wire, please refer to following link to aid in your selection:
http://en.wikipedia.org/wiki/Wire

Bruce

Beau Schwabe
03-10-2012, 06:32 PM
Be careful when using a silicone sealant ... some are corrosive to wire. A quick way to tell... If the silicone smells like vinegar, don't use it.

idbruce
03-10-2012, 06:43 PM
Be careful when using a silicone sealant ... some are corrosive to wire. A quick way to tell... If the silicone smells like vinegar, don't use it.


Never heard that before.... Nice piece of information.

Prophead100
03-10-2012, 07:02 PM
West marine also has a liquid electrical tape that is designed for sealing wires in wet locations. You still would want a heat shrink to protect it though.

RDL2004
03-10-2012, 07:20 PM
Be careful when using a silicone sealant ... some are corrosive to wire

This is true, but there are types which are safe for electronic (and plumbing) use. All you have to do is go to Google and search on: acetic acid silicone. It doesn't seem to hurt fish though, for some reason, because one common use is as aquarium sealant. I guess the acetic acid exudes and is washed away, but with wiring it gets trapped between the silicone and the surface of the metal.

4x5n
03-10-2012, 09:01 PM
I repaired a broken power cable on my submersible well pump by soldering an inch or so of the wires together, putting silicone sealant (food grade) around the copper and a bit of the insulation, then heat shrink tubing over that. It was still working 4 years later when I sold the place.

Not sure I understand the reason for using food grade silicone sealant but I've also used silicon inside of heat shrink tubing for splices that needed to be water "safe". For "smallish" gauge wires you can get plastic crimp connectors. They contain a small vial of silicon and when you crimp the connector to make the connection the vial breaks and seals the connection. I haven't seen them for wires bigger then 18 gauge though and won't be useful in this case.

Peter KG6LSE
03-10-2012, 11:51 PM
Be careful when using a silicone sealant ... some are corrosive to wire. A quick way to tell... If the silicone smells like vinegar, don't use it.

Learned this the hard way .. :)

xanadu
03-11-2012, 07:20 PM
It would look cool :) with a clear PVC conduit, and you could inspect the wires anytime.

kwinn
03-11-2012, 08:47 PM
First off, welcome to the Forums, Ken Nonymous!

I don't have an answer for your but I'm puzzled by the responses. I thought the learned opinion on the forums a while back was that crimped connections were better than soldered connections. In this case, crimped connections with non-corrosive goo and adhesive shrink wrap would be the bestest!

Hope this doesn't cause a firestorm of debate around your project.

Based on my experience I would say all else being equal, nothing beats a good solder joint. Of course the solder joint has to be done properly. At least an inch of overlap between the wires to be joined, an adequate and even application of solder, and complete removal of flux residue and other contaminants from the area the shrink wrap and/or other insulating material will be placed.

kwinn
03-11-2012, 08:50 PM
Not sure I understand the reason for using food grade silicone sealant but I've also used silicon inside of heat shrink tubing for splices that needed to be water "safe". For "smallish" gauge wires you can get plastic crimp connectors. They contain a small vial of silicon and when you crimp the connector to make the connection the vial breaks and seals the connection. I haven't seen them for wires bigger then 18 gauge though and won't be useful in this case.

The food grade silicone sealant does not contain acetic acid.

Loopy Byteloose
03-12-2012, 07:29 PM
Acid or basic conditions set up corrosion around electrical connections. Just look at the battery in your car. It is lead acid, so the cables become a mess. It is all about providing unwanted ions. Even acid core solder is a problem. Regular silicone used chlorine as a catalyst for setting and that is ionic (thus the food grade is thought as best). I am not sure where the acetic acid comes in (maybe in food grade as acetic acid is equivalent to vinegar). I do find cleaning copper circuit board with alcohol a corrosion problem as that too is a slight acid (so I use soap and water).

There is a real perception problem here with recommending any particular silicon as superior in this context. Why so? The manufacturers have taylored proprietary formulations. There are regular, food-safe, and fish-safe. Some 'regular' compounds have fungicides in it. That may not be safe for food or fish; but good for a wire connection. Furthermore, it seems most have moved entirely away from cholorine and into acetic acid for setting the RTV (room temperature vulcanization) Silicon sealants. Thus, this is a huge tempest-in-teapot. In this context, any silicon is likely to work well. If you have doubts, use hot glue (and don't ask me what's in it). A soft epoxy might be the truly best alternative as an inert, water tight sealant.

And, if the wires to be connected are going to heat up enough to potentially melt normal solder, a crimped or mechanically connected wire is better. Just look at all the heavy wiring inside your home fuse box. No soldering there - all mechanical. Sometimes, silver solder is used to tolerate a higher temperature.

In older homes, all the wiring in the walls was soldered and wrapped with tape; ceramic knobs and tubes kept the wires away from wood.

Now all connections are required to be made inside an electrical box in order to prevent fire. Also, the boxes allow one to open and repair failed connections as nearly all failures of wire are at the connections.

Old school (circa 1950s) technique required that all solder joints first be constructed as a good mechanical joint, and only then be soldered.

In other words, techniques are evolving as we speak. Use common sense and try to make the connections both durable and repairable.

bill190
03-13-2012, 12:30 AM
...And, if the wires to be connected are going to heat up enough to potentially melt normal solder, a crimped or mechanically connected wire is better. Just look at all the heavy wiring inside your home fuse box. No soldering there - all mechanical. Sometimes, silver solder is used to tolerate a higher temperature...

FYI - For high amperage electrical connections, the mechanical connections need to be torqued to a specified tightness or the connection will get warm or hot!

"Tight" is not good enough. Needs to be "tighter". They typically specify to tighten in "inch pounds". 1 foot pound = 12 inch pounds.

idbruce
03-13-2012, 12:58 PM
bill190



FYI - For high amperage electrical connections, the mechanical connections need to be torqued to a specified tightness or the connection will get warm or hot!

"Tight" is not good enough. Needs to be "tighter". They typically specify to tighten in "inch pounds". 1 foot pound = 12 inch pounds.


Not that is relevant to this thread, but since you brought it up.

Several years ago I attended a licensing preparation seminar for the NEC (National Electrical Code) and the speaker was Tom Henry's son. Both Tom Henry and his son are experts in the NEC. During the seminar, he told the class that he is often called to testify as an expert witness in cases that involve both fire and death resulting from faulty wiring. He also said that his main testimony often consisted of the hazards of not torquing electrical devices to the manufacturers specifications, at which point it is basically a shut case with the installer being liable for neglect, providing the installer did not properly torque the electrical devices.

Bruce

jmg
03-14-2012, 01:08 AM
Old school (circa 1950s) technique required that all solder joints first be constructed as a good mechanical joint, and only then be soldered.


This is still good advice - if it is a serious connection, I usually sparse-wrap with some finer tinned copper wire, a number of turns along the overlap, and then solder the lot.
If you do this to stripped, but _not_ tinned multi-strands, you can get a more circular end result.

Ensures nothing moves as the solder cools, and gives some ribs for that marine grade heatshrink to hold onto.