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Potting Compound


(Patrick) #1

Hi,

Any advice on what potting compound to use on the connections of M100 motors? Can’t seem to find Loctite Marine Epoxy anywhere in the UK.

Thanks, P


(Harold Scadden) #2

Patrick I don’t know what distributors you have in the UK … but have you tried buying the potting compound on Internet via an overseas distributor?

I have a special silicone that I use in one of my products that even with buying it in the US, the material is still shipped directly from Dow Cornings plant in Japan. I don’t think you would have an issue with HAZMAT and a carrier for that compound.

Give that a try and or if you got particular distributors in your area … I might have time to scan their sites for something that you could give a try. Please understand it would ONLY be a recommendation because Blue Robotics pressure tested their product using the recommended epoxy and that is really the only thing that has concrete testing. I am not saying other stuff won’t work, I just thought I would toss that disclaimer in for myself and the OEM.

 


(Patrick) #3

Harold, thanks for the advice. I’m working on a university project with a pretty tight timescale and can’t afford to wait for the delivery. Would something like this be sufficient?

http://www.toolstation.com/shop/p96720

Patrick.

 


(Harold Scadden) #4

Patrick, I HIGHLY recommend staying away from quick set two part epoxy resins. Please use something that is a slow cure because it will do a couple of things for you …

Slow cure resins allow natural degassing of the pour and they have a better tendency to adhere to dissimilar components.

Now I will say that I just checked out the Safety Data Sheet for it and I am very familiar with the resin / curing chemistry that this epoxy uses. Even though I hate fast cures … it has a good base resin / curing agent. It is more than likely going to be runny once you mix it. The resin will more than likely be thick until you start stirring in the curing part. If you have the capability … degas this stuff under vacuum if possible. You are going to mix air into it.

As far as the chemistry on it, it will have some shrinkage on you but considering what you are going to “pot” you shouldn’t experience much. Your volume is small.

I can only say … “Go for it!”. Please let us know the results.

Also, if you can lightly sand the areas that you can reach (leave electrical contact areas alone) this will help to increase your bonding surface area and give you a better seal.

Good luck!

 


(Patrick) #5

Thanks, I’ll let you know the results!

Patrick.


(Paul) #6

Since epoxy and potting are such important parts of any build using B.R. components, maybe someone can post a video how they do it? Particularly how they pot wires in the hull penetrators? I think this would be very helpful.


(Rusty) #7

Hi guys,

We’re trying to figure out how to offer the Loctite Marine Epoxy for shipping. Unfortunately, shipping chemicals is a little tricky.

Most epoxies should work pretty well but there are degassing issues with fast-cure and it can be tricky to seal the M100 connections with anything that has thin viscosity. The marine epoxy is very thick which makes it easy to apply.

Paul, we definitely want to post video tutorials on how to use our products. We’re working on it! We would, of course, really appreciate any videos from users as well!

-Rusty


(Nicholas) #8

I’m not a fan of the epoxy where you squeeze it onto cardboard and mix it with a popsicle stick. It gets dust and dirt and moisture and air bubbles and doesn’t mix in the right proportions.

I’ve get around these issues by using the professional style 50ml double syringe packs with the twisty mixing tip. No air or contaminants can get in and it mixes fully and in the right proportions. If you get the 3M DP-270 or anything in that family it is designed to be used with the mixing tips and squeeze gun. There are lots of chemical companies that use this same double 50ml package, not just 3M, so it’s a good idea to own that gun if you’re getting into this sort of thing.

This is 3M DP-270:

Here are the mixing tips:

http://www.amazon.com/3M-38191-Static-Mixing-Cartridges/dp/B00596QVHG/ref=pd_sim_328_1?ie=UTF8&dpID=41XEPL2d0TL&dpSrc=sims&preST=AC_UL160_SR160%2C160&refRID=07DFQYY0ZZZ05KXJNS8M

Here is the squeeze gun:

http://www.amazon.com/3M-Scotch-Weld-EPX-Plus-Applicator/dp/B001ANXYF4/ref=pd_sim_328_4?ie=UTF8&dpID=31kYmNJ8GIL&dpSrc=sims&preST=AC_UL160_SR160%2C160&refRID=07DFQYY0ZZZ05KXJNS8M
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(Harold Scadden) #9

@Nicholas - it is not so much using a spiral mixer tip as it is the epoxy that you are using in the first place. The current epoxy that Blue Robotics is using on their motors / penetrators works just fine. I mix epoxies all the time and I don’t worry about the things you have mentioned … never had a problem with dust/dirt, moisture or the air bubbles. Air bubbles only happen in the lower viscosity fluids to a point that even start to create or make you think you have a problem.

The motors were tested at pressures much higher than anyone on here will ever go with them … and they didn’t leak. That pretty much proves it in my book.

 


(Nicholas) #10

I didn’t mean to imply that BR motors aren’t properly made, or that Loctite isn’t a fine epoxy. It seemed like OP was asking for some alternatives to the Loctite stuff, and other people were giving opinions on what works for them. The 3M stuff works for me, especially since I’m a clutz and tend to make a mess. It’s all the same chemicals right? Epoxy, urethane, etc?


(Harold Scadden) #11

@Nicholas - 3M works fine for me too … just not in this application. The problem with epoxy, urethane and the long list of two parts … they are not all created equal and what works for one application can totally bomb for another one.

Yeah, the two parts that use spiral mix tubes are nice and help you to get a pre-mix out of the tip that is at the correct ratio, but you would be amazed at how dorked your mix ratio can be and it still works. Then again, that depends on the two part that you are using.

The Marine Epoxy that is called out on this sight is something that I messed with and I am not happy with how you have to mix it but I understand the reasons why. It won’t shot through a mix nozzle to save your life. I have all of the tools of the trade at work since that is what we do for a living … urethanes, epoxies etc. for molding cables for use in seawater at extreme pressures and I was stuck hand mixing it. Again, it wasn’t because of how the container came … it is because the stuff is viscous as all heck. I couldn’t even mix it by hand and load it into a syringe to inject it.

I also have two part epoxies that you can’t use a mixer nozzle on because of the totally opposite reason … they are so blasted runny that the mixture would run straight through the nozzle.

 


(Manolis) #12

Hi everyone,

When I examined the attached image to the cable penetrator I came accross a possible issue :

Can a tiny cut (or hole) on the umbilical (eg a simple twisted pair) act as a pipe to induce water in the watertight compartment through the cable penetrator and the potting mixture? Should we remove the insulation from the cables (of the umblilical or motor(s) or light(s) ) and use a kind of spacer to keep the conductors separated until the compound cures ? In that case

a) is the potting compound an effective electric insulator ?

b) how many conductors and of what diameter can pass throught the (6mm?) penetrator bolt without touching each other or the bolt itshelf ?

Can’t seem to find Loctite Marine Epoxy anywhere in Greece, too.


(Harold Scadden) #13

@Manolis - if you have a cut in the cable jacket there is a chance that water can wick into your enclosure … that without a doubt is a good possibility. Will it happen instantly? Depends on water depth etc. on how fast the water will wick.

As for electrical properties … I never tested it and the Technical Data Sheet has non listed; however, from looking at the contents of the “Part A” on the MSDS the epoxy resin is silica filled. Every silica filled epoxy I have ever used as been an execellant electrical insulator. By nature, epoxies are insulators.

The amount of wires within a “cable” would be determined by the overall gauge of the conductors etc.

If you can find a waterproof epoxy and have a link to a technical data sheet, I can at least give you an educated guess on if it will work or not.