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JB Weld vs. Solder

Old 10-19-2013, 11:58 PM
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abufletcher
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Default JB Weld vs. Solder

You hear some great claims about JB Weld. But which is stronger, JB Weld or Solder? Or are they strong in different ways and for different applications? I can't imagine using JB Weld to bond music wire undercarriages (instead of solder). But maybe it could work. Maybe the music wires wrapped first as we do with copper wire and then slathered with JB Weld WOULD hold up just fine. Certainly the method that GTM used on undercarriages works (e.g. using JB Weld to hold music wires inside aluminum tubing).

At the moment, I'm endeavoring to make scale, yet still fully functional, rigging attachment points for my Albatros CI. On a previous Mark I version I used solder (regular solder instead of silver solder). But on a Mark II version, I've tried JB Weld which greatly simplifies the production. The primary job of the JB Weld is to connect a brass eyelet to a 2.6M bolt via a length of 4mm brass tube. The brass tube passes through the wing and the fitting is held in place by a nut (as on the original). It seems strong enough.

Anyway, what are your experiences with JB Weld?

Last edited by abufletcher; 10-20-2013 at 02:34 AM.
Old 10-20-2013, 06:30 AM
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LesUyeda
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My understanding is that JB Weld is nothing more than an epoxy.

Les
Old 10-20-2013, 06:50 AM
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abufletcher
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Technical it certainly is. You mix the two parts together just like epoxy, but it's cures much slower and it's claimed that you can drill it and shape it just like metal afterwards. So perhaps it's epoxy with metal powder mixed in. Does this improve the metal to metal bond characteristics? I don't know. My guess is that JB Weld is at least a strong as regular solder.

I suppose it comes down to what sort of "strong" we're talking about. Strong in tension (for example the bolt ends in the brass tube) is probably one kind of strong. And strong under load (as in soldered undercarriage joints) might be completely different. And then there's the question of which would be most resistant to vibration or repetitive stress.
Old 10-20-2013, 07:39 AM
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It seems to be quite strong in the "can't pull it apart" sense:

http://www.youtube.com/watch?v=5JynysLv9R4
Old 10-20-2013, 10:17 AM
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Solder is stronger. JB weld is easier. JB weld is epoxy; it just has a filler that is hard, and made for cheap fixing of castings. JB will be stronger than a bad solder joint so if you cant make a solder joint for nothing, JB will be good. The harder the solder the stronger, too. Just have to have more heat to get the job done. Both are about shear and surface area; both will break when you exceed. Tension joints, although necessary, are weak joints.
Old 10-20-2013, 02:04 PM
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[QUOTE=abufletcher;11642680]It seems to be quite strong in the "can't pull it apart" sense:

http://www.youtube.com/watch?v=5JynysLv9R4 [/QUOTE

From my experience JB Weld is grossly over rated. I have an application that requires great shear strength in which JB Weld failed miserably. I tried other epoxies with greater success; but still not adequate.
I finally gave up and resorted to using silver solder and have not had any joint failures, even when subjected to 10x the stress.
Old 10-20-2013, 02:05 PM
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LesUyeda
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", but it's cures much slower and it's claimed that you can drill it and shape it just like metal afterwards."

I have forgotten the details, like many other things that I have forgotten, but there two flavors (at least) of epoxy hardener, and depending on which one you use, what the epoxy cures out like. Either not rock hard, ever; or just like that video shows.

Les
Old 10-21-2013, 04:33 AM
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abufletcher
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I suspect that JB Weld is at least as strong at ordinary electrical solder. Probably not as strong as silver solder. For my little fittings I also suspect that JB Weld will be stronger than a poor quality soldering job...which seems likely given the way the pieces (of dissimilar metals and finishes) have to fit together.

Last edited by abufletcher; 10-21-2013 at 06:21 AM.
Old 10-21-2013, 06:08 AM
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I'm a soldering rock so I use JB Weld on occasion and like it a lot. I have concerns about it being fuel proof. On one application I JB Welded the inside of a nose wheel. Fuel (5%) would flow onto it in small amounts constantly (it was directly under the engine). Over time, I have noticed I am wiping away gray guck from the washer.

I used it once to hold a starter onto an outboard motor housing when the threading in the motor broke off. It held for years until I replaced the outboard.
Old 10-21-2013, 08:57 AM
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cocobear
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JB Weld is much stronger n compression tension situations. Add vibration or bending and it fails quickly. Abu, when you say silver solder you mean hobby grade right? "Real" silver solder dstroys any asspect of JB Weld.
Old 10-21-2013, 10:20 AM
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Yeah, I'm talking about the 3% silver solder that flows about about 450C (vs. what is sometimes called "brazing" that flows at closer to 700C). I guess what I was hoping was that since biplane wing struts are actually in compression in flight (i.e. their function is to keep the wings APART rather than to keep the top wing from flying off), combined with the fact that the rigging wire stresses are at an angle, that the JB Welded attachment points would do the job.

How much vibration is there on flying wires?

Last edited by abufletcher; 10-21-2013 at 10:51 AM.
Old 10-21-2013, 12:01 PM
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cocobear
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I believe that even a small bit of flutter would destroy the JB. suck it up and solder them
Old 10-21-2013, 12:17 PM
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Originally Posted by cocobear View Post
I believe that even a small bit of flutter would destroy the JB. suck it up and solder them
Easier said than done. I'll have to order a new set of eyelets and essentially start all over again with a new design for the fittings. And silver soldering such small fittings (including soldering so that no solder gets on the bolt threads) is no easy task. I'll also have to rethink the attachments of the top wing fittings. But what has to be done has to be done.
Old 10-21-2013, 12:24 PM
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Maybe I can use one of my JB Welded fittings to do some informative destructive testing.

It boils down to whether the threaded part of the brass eyelet would pull out of the brass tube. It would be easy enough to solder the eyelet directly to the tube, but it first has to pass through a collar (stamped, plated aluminum?) and several other parts so that the actual location of the solder joint would not be visible while soldering. I would just have to trust that the solder if flowing into the joint.
Old 10-21-2013, 12:26 PM
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LesUyeda
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My fuzzy mind, again. I'm not clear where we are talking about using JB or solder????

Les
Old 10-21-2013, 12:43 PM
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Jim Branaum
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Originally Posted by abufletcher View Post
Maybe I can use one of my JB Welded fittings to do some informative destructive testing.

It boils down to whether the threaded part of the brass eyelet would pull out of the brass tube. It would be easy enough to solder the eyelet directly to the tube, but it first has to pass through a collar (stamped, plated aluminum?) and several other parts so that the actual location of the solder joint would not be visible while soldering. I would just have to trust that the solder if flowing into the joint.
Hmm.. there has to be an easier way. Why couldn't you put solder into the tube, tap it when it cools, install the eyelet and then reheat the tube later to make the solder flow around the eyelet?
Old 10-21-2013, 01:03 PM
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JB Weld is good for large areas and as you stated in the first post - filling in the voids of a tube around rods in the tube.

But I would not trust JB Weld at all for a small area join where solder would be much more secure.
Old 10-21-2013, 03:14 PM
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I have done allot of silver and low temp soft soldering over the years, done properly I would trust either method far beyond JB-Weld when it comes to attachment of metal to metal. Then again that is just one mans opinion...

Bob
Old 10-21-2013, 04:06 PM
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A good one though
Old 10-21-2013, 04:25 PM
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Originally Posted by sensei View Post
I have done allot of silver and low temp soft soldering over the years, done properly I would trust either method far beyond JB-Weld when it comes to attachment of metal to metal. Then again that is just one mans opinion...

Bob
totally agree. JB weld wouldn't be as strong in a metal joint subjected to bending stress like a landing gear. I have had success bonding wood to metal using JB weld though but that joint is loaded in shear, different than a direct bending load.

There's the strength of the bonding agent (the jb weld itself or solder itself) to consider as well as the strength of the bond between the glue and the substrate(in this case the metal). I'd expect solder to stick to metal better than JB weld if the surface is properly prepared.

greg
Old 10-21-2013, 04:52 PM
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In my experience JB Weld is great for stationary items. The least bit of movement or vibration and it break's. I tried it on a set of flying wires where the joint was in the fuse. It did not last but one flight, on the second the wires were flapping and the JB was in tiny bits in the bottom of the fuse. I have also tried several low carbon wire for flying wires and they stretched, so I would have to say flying wires are under a good amount of stress and flex. A good way to see the flex in flying wire is to use a hacksaw handle to mount a wire to. Don't tension any more than it would be on an airframe. Then get in your vehicle and get up to 60-80mph and hold the hacksaw out the window, I think you will be surprised at how much they dance.
I don't use anything other than 60% silver based solder now. And no regrets, and yes there was a bit of a learning curve but well worth it.
Old 10-21-2013, 05:37 PM
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There's a lot of experience talking here and it seems prudent on my part to accept it. I'll start over with some soldered fittings. (By the way, I like the idea of putting a bit of solder INSIDE the tube!)

The ideal solution would be an eyelet with a threaded 30mm post. But the longest I can order have only a 7mm post. Thus I need to extend them with the length of brass tubing.

Incidentally, it's interesting to note that one several of the DBsportscale WWI models the struts are held in place with MAGNETS! Of course the flying wires themselves are anchored (with a patented DB system) to the spars (as they ideally should be).

Old 10-21-2013, 05:56 PM
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It is just that metal has much different CTE (Coefficient of Thermal Expansion) then that of an epoxy based paste like JB Weld. So with that said, every time your application of metal to composite bond line is subject to hot or cold conditions they literally try to break free from one another of the bond line between the two substrates, we in the composites field use the CTE at times in metal mold to composite component manufacturing relationships as a needed process for the successful release of the part from the tool after an elevated cure cycle.

Bob

Last edited by sensei; 10-21-2013 at 06:00 PM.
Old 10-21-2013, 06:47 PM
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I would say that using JB Weld to glue a peice of threaded rod into a brass tube would be fine. The key to success would be to make sure the pieces are as clean as you can get them using acetone. The next is surface prep, you need to get any oxides off the materials. Sanding with 320 on the bonding surfaces would take care of this followed by bonding the parts within a couple hours. The big part of the equation would be to cure at an elevated temp. This will increase the strength of any epoxy and will help stabilize the CTE that Bob mentions. At 150 degrees slow cure JB Weld will be fully cured in one hour. Hysol makes some products designed to bond metals to composite structures, another option.

FYI soldering is going to be more difficult then you think. The tricky part is going to getting the two very different materials to the same temp. This is necessary to get good solder flow. All electronic barrel type solder connectors have weep holes so you can see the volume of solder that flows into the barrel. We also use a resistance type soldering tweezer to apply heat as it will apply the heat on both sides. Very tricky with just an iron without overheating. Pre tinning both parts makes good sense then simply re flow the barrel and slide the threaded rod in,make sure you get re flow of all solder and then remove heat. Everything has options.
Old 10-21-2013, 07:43 PM
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Originally Posted by speedracerntrixie View Post
FYI soldering is going to be more difficult then you think.
No, that's exactly what I think. It's going to be a nightmare...which is why I was hoping that JB Weld might do for this application. Later, I'll try to post a sketch of what I'm trying to achieve.

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