20 replies to this topic

[chasbeeman]

I'm curious about an epoxy that doesn't need oven time to cure. Has anyone used JB Weld successfully for magnet installation?

[havlicek]

Always, and it's great for this.

[Don Weaver]

But don't you still need to "cook" it for best results?

[gotboostedvr6]

I used JB for many years.

I never had a failure.

Loaned a motor to a buddy who quickly ruined my win streak.

Now I use an adhesive simular to Skinners and bake the setup in a toaster I picked up from goodwill for $4.

The nice thing about my adhesive is I coat all my cans and magnets months ahead of time and bake and assemble when needed.

[Pablo]

Cook it if you're in a hurry.

 

If not, let it dry overnight.

 

It works great on magnets, as Havlicek said.

[gotboostedvr6]

I've found that warming JB early in the cure will help it flow. It's magnetic so it typically flows where youd prefer it to be. I warm it to around 100 degrees for 2 min then let it finish cure at room temp.

[Bill from NH]

At one time, JB Weld was the epoxy for gluing magnets into cans. Now I would limit its use to gluing ceramic magnets. Both the black Koford & Skinner's do a better job for gluing in cobalts. If anyone needs some technical data, contact Rudy Garriga, owner of Slick 7.

[havlicek]

I wouldn't know about cobalts, but I've glued in MANY solid and poly-neos as well as ceramics, so limiting the use of JB Weld to ceramics is fine, but not warranted by it's performance at all. I build these things all the time and I wouldn't use JB Weld at all... if you ever want to remove the magnets  JB Weld is, after all, a hi performing heavy-bodied epoxy. It will bond like crazy to most all "bondable" materials.  That bond is good to a surprisingly high temperature as well. Try hitting a can with magnets that have been installed with JB Weld with a torch and see what it's like to remove them.  I am absolutely sure JB Weld will bond just as well to cobalts as any other magnet material. I am not sure it's upper limit service temp is as high as Koford's or Skinners, nor am I sure stated max service temps are actually necessary.  

JB Weld (*not the "quick stuff") is good to 500 F for extended periods, and has a short term service capability (10 minutes) up to 600 F. With a material like JB Weld, if I experienced a bond failure, I would feel confident that it was due to improper prep or application/curing. I guess that some open motors experience 500 F operating temperatures at the can (?), but that would mean even higher temps at the commutator.  Anyway, if such things do happen, then for only those motors would I look for something else to use. Other than that, it's gobbledegook nonsense to not use JB Weld for the vast majority of motor magnet installations, because of worries about bond failure. The best advice to give is that JB Weld is great for the vast majority of cases. It's also cheap and readily available.

JB Weld FAQs

[NSwanberg]

[quote]I build these things all the time and I wouldn't use JB Weld at all... if you ever want to remove the magnets.[/qtuote]

 

I have a friend that came up to Michigan many years ago from Texas. He kept hearing about people using JB Weld. Being familiar with most welding processes he thought JB Weld was a welding system he had never encountered. The way the stuff works it might as well be.

[havlicek]

I have a friend that came up to Michigan many years ago from Texas. He kept hearing about people using JB Weld. Being familiar with most welding processes he thought JB Weld was a welding system he had never encountered. The way the stuff works it might as well be.

 
 In this case, it's not much of an overstatement to call it JB Weld. It's also great for installing bearings in cans if you want to avoid acid, and getting those bearings out (if necessary) is anything from really difficult to impossible without doing a number on the can. Not much has changed since whenever it was that "JB Weld was the epoxy for gluing magnets into cans." Certainly the materials (steel cans, ceramic and other composition magnets) are the same. I guess operating temps at the extreme high end may have changed a little, but I think it's more likely than not that any failures were because of poor prep and cure, rather than JB Weld not being up top the task. It could also be that Skinner's is more tolerant of poor prep, and there would be less failures related to that.  

 

Even so, there are only a very few cases where Skinner's *might* be better, so JB Weld should still be the choice almost always. It's a heckuva lot cheaper and more readily available, too.

[Robert BG]

I've used JB Weld before for years without any issues. The only time I had a problem was because of bad prep work.I have both ceramic strap can I-15s and cobalt Group 27s from 20+ years ago that were bonded with JB Weld that are still holding strong to this day. The stuff works and works well but it isn't forgiving of sloppy prep work or acid flux intrusion (no epoxy is).
 
Now having said that these days I'd only use it in a pinch like if I couldnt bake the motor, ran out of stuff while prepping for a race, or maybe on a C/D can that also used clips, tabs, etc., to hold the mags in place, etc. Not because JB Weld isnt good, it's just Skinner's or Koford's stuff is just a little better, especially for those of us that race.
 
Now if you're not a serious racer building high-end motors chances are you'll be fine. But considering the cost of a tube of Koford's stuff it's hard to justify using JB Weld in my opinion. Although if baking is the deal breaker then by all means use JB weld and if you can't bake it but want the benefits of the faster cure and more fluidity with the JB weld you can hang the finished motor over a light bulb. A few inches above a 60 watt bulb will be all you need and when I used to do it I'd make a little stand of sorts from alum foil. All you're trying to do is elevate it a little from the bulb and make a place to set the motor.  If done right you can set the motor in the foil and it'll heat everything pretty evenly.
 
Realistically John is correct and for most folks on here JB Weld is all anyone really needs. Unless you're a serious racer/builder, then there comes a point where the step to Skinners/Koford epoxy is the way to go. But by then you'll have the experience to know whats needed and why.

[Cheater]

Want to emphasize that you definitely do not want to use the 'five-minute' JB QwikWeld.

 

As for heating JB Weld, I would stick the can on the backside of my Hakko iron holder, though I did use a light bulb for many years.

 

One of the nice things about JB Weld is that it will reach a pasty, plastic stage so you can "carve" the overflow and squeeze outs away with an X-Acto and small screwdrivers before it gets rock hard.

[havlicek]

Besides what Greg said, it should be restated that JB Weld does not need to be warmed to cure to full strength. Warming it will definitely speed the cure, and short of a separate toaster oven not used for food, a hair dryer, soldering iron, lightbulb whatever will work just fine... but are only necessary if you're in a hurry.  

 

Of course, for motors that won't see such high service temps and also use clips, regular CA glue will work fine to prevent the magnets from moving forward or aft and messing with the arm-centering.

[Guy Spaulding]

Used it exclusively in the '80s for 15s, and cobalts. Clean the areas to be glued, inset magnets and position as desired with alignment plug or wedges. Set on a solder block and use an incandescent, goose-neck desklamp with the bulb right on the motor overnight. 

 

Todays CFL bulbs don't seem to do the same. Wonder why? LOL.

[Phil Hackett]

I never had a problem with JB Weld. One of the secrets to using it is *not* overheating it in an oven. Cure it at about 150°F max. It'll set fast but you still have to wait 12 hours or so.

[Ramcatlarry]

Todays CFL bulbs don't seem to do the same. Wonder why? LOL.

 

CFL and LED bulbs are more efficient on giving light and minimum heat compared to Halogen and incandescent bulbs. The goal is to heat the liquid epoxy to help it set up.

[havlicek]

'Zackly. Light bulbs were never intended to be "heaters." That they have been used as such is a testament to just how inefficient incandescent bulbs actually are. The heat is energy wasted, i.e. not being turned into light, as a byproduct of the intended purpose of producing light.  

LED bulbs still produce heat, but not enough to be "useful." So, if you try installing one in your EZ Bake Oven, that little cake ain't gonna bake!

[Racer36]

Sheesh... Here I thought I was a lousy baker...

[havlicek]

Sheesh.... Here I thought I was a lousy baker.....

 

 Well, for the EZ Bake thing, Uncle Fester has the right idea Dennis!

[David Rees]

I have used it but eventually the magnets would always come loose .  Take my tip use Koford magnet epoxy for reliability 

[Roy Lievanos]

I used JB weld back in the 80's. I would come home from work on a Friday. Build a couple of setups and glue magnets with JB weld. Around midnight I would put them on my rabbit intake manifold and drive to Phoenix for a USRA race. Nice and hard after 6 hrs. Never had a problem. Been years since I have had to glue magnets since I got back into slots using $14.00 Sealed motors.