Gear tower trouble in my AC6?

[JMaurer1]

I would have gone with epoxy as well. Brass expands and contracts a BUNCH depending on the temperature. CA , while it has great tensile strengths (reaching up to 4,000 psi in some cases), but it has rather low shear strength and and low ductility—brittle bonds that poorly resist impact loading. In other words, once the brass expands and contracts enough times, the CA bond will start to weaken and will eventually break. Now that the CA is holding the part where it should go, I would use a toothpick and add some epoxy to strengthen the bond.

Obviously this is becoming even more of a frustration to you by this point. Once again I am more than willing to take this burden on for you...just box the locomotive up and send it to me. I promise to post how difficult it is being once I have it so that you will be spared the frustration of having to go through it by yourself... 

[ATSF_Ron]

JMaurer1, well I certainly know who to contact when my eyes can't handle N scale any longer, lol!  I like the idea of an epoxy backup.  Others have mentioned epoxy as well.  I may run over to my local Ace Hardware as they usually have at least 3 types in stock.

[peteski]

JMaurer1, well I certainly know who to contact when my eyes can't handle N scale any longer, lol!  I like the idea of an epoxy backup.  Others have mentioned epoxy as well.  I may run over to my local Ace Hardware as they usually have at least 3 types in stock.

Best for this type of repair is J-B Weld Original Cold-Weld Formula. Not the 5-minute version. Yes, it takes 12 hours to harden, but it is also creates a strongest joint. I usually put the glued object either in the food dehydrator (which I normally use to speed up paint drying on my models), or on the top of my heating boiler. Either one produces gentle heat which accelerates the cure, and hardens the epoxy.  While adding epoxy over CA seems like a good idea, remember that if the epoxy does not directly contact bare metal of both parts being joined, the bond will be only as strong as the weakest part (which in this case is a layer of CA).

[robert3985]

Best for this type of repair is J-B Weld Original Cold-Weld Formula. Not the 5-minute version. Yes, it takes 12 hours to harden, but it is also creates a strongest joint. I usually put the glued object either in the food dehydrator (which I normally use to speed up paint drying on my models), or on the top of my heating boiler. Either one produces gentle heat which accelerates the cure, and hardens the epoxy.  While adding epoxy over CA seems like a good idea, remember that if the epoxy does not directly contact bare metal of both parts being joined, the bond will be only as strong as the weakest part (which in this case is a layer of CA).

What @peteski said. 100%

I will add make sure you completely de-grease your surfaces.  I prefer Bestine (heptane) and have used it for decades for de-greasing/de-waxing before painting, gluing and soldering.

Cheerio!
Bob Gilmore

[ATSF_Ron]

CA didn't hold.  As soon as the mini clamp came off, I heard a tiny "plink" noise and the joint failed.  Cleaned up and used the JB Weld.  Most of the cab bottom and top of the tank are shiny clean.  Clamp is back on.   We'll see tomorrow.  The saga continues, lol!

[peteski]

CA didn't hold.  As soon as the mini clamp came off, I heard a tiny "plink" noise and the joint failed.  Cleaned up and used the JB Weld.  Most of the cab bottom and top of the tank are shiny clean.  Clamp is back on.   We'll see tomorrow.  The saga continues, lol!

Oh well. . .  And to repeat what Bob and I have mentioned, for a good glue joint it is absolutely essential that both metal surfaces are free of paint, debris (like leftover AC glue), and grease/oil free.  Did I mentioned thoroughly degreasing the surfaces to be glued?   

Seriously, in model locomotives (which are lubricated, or even over-lubricated by default) oily film can over time spread out even to the loco's shell.  That is why it is so important to make ure to remove any possible greasy stuff.  That is why it is so vital to make sure to remove all oily film from the glued areas.

I'm also curious: when the CA joint failed, did it separate cleanly from one of the brass surfaces, or the break was in such a way that the glue remained on both glued surfaces?

[ATSF_Ron]

Peteski, it looked to me like it was the tank only. Which probably means I didn’t clean the other surface properly I’d guess.

[JMaurer1]

Darn it, I think that this will take care of your issue. Postman is going to miss me meeting him at the mailbox hoping for a box from you...

[ATSF_Ron]

Yep. Seems to be holding up well! 👍🏻

[ATSF_Ron]

Well, I decided to send it back.  Straight track running was fine.  Even through #6 turnouts.  There was a tiny bit of hesitation when taking the side track but not objectionable.  I decided I better try some S curves with my Unitrack test track.  The darn binding in the left turns was back.  No amount of fiddling loosened things up.  Plus, even the 19" radius curves I was using seemed "tight" and a bit bindy.  Also, I laid down a few ideas for my new layout section in the actual layout room using the Kato Unitrack 19" radius curves.  It just wasn't going to happen.  I thought I'd have the space for maybe 20" or 21".  Nope.  Reality set in.  The loco just wasn't running properly for what my needs are and on the radius I can actually accommodate in the space I have available.  Bummer.  Maybe someday in my lifetime Intermountain or BLI will release some of the early cab forwards, but for now I guess it's just the Intermountain AC-12s I have.

On the upside, I was able to score a couple SP connies for a very reasonable price.  Fabulous runners in 100% mint condition.

[Mike Madonna]

Ron,
Sorry to hear that loco went back. I guess you could chock this up to a "learning experience" with N scale brass steam.

[ATSF_Ron]

Thanks Mike. That’s how I looked at this. I got a lot of good experience working on the innards of one of these beauties. And I figure these are some of the most finicky to take apart. I think if I survived that I can pretty much open up anything I own. Well, maybe not an Intermountain. I’ve heard there’s a ton of parts to those things!

[JMaurer1]

Where is 'back'? I still might be interested...