Assembly trick for Kadee coupler boxes with centering springs?

[IWannaRetire]

Does anybody have a trick for assembling this sort of coupler box? 


 

I've read and understand why coupler boxes should not be glued to car frames or bodies. I use hardware.

I am working with Kadee 803/7 boxes (On3-On30) that have a centering spring. That is, they should have, but my springs keep vanishing into thin air...

I can assemble them OK off the car, but then trying to keep the box and lid together while turning the assembly upside down and trying to insert mounting screws, is where things go awry. 

Before even trying to assemble coupler to car, I pre-drill and run my mounting screws in ahead of assembly to cut appropriate threads, so when it comes to final assembly "all" I need to do is hold the coupler in place and tighten the first screw.

I just want to hold the box and lid together for a bit, just long enough to screw it to the car.

I tried MEK, it doesn't work at all. I tried a tiny bit of AC, the sort that comes in tiny tubes.  I applied a tiny bit to the outside of the join between the box and lid, not to the actual joining surfaces. It worked, but hours later, my coupler was sticking, it hadn't been initially.  My guess is that the vapors gassing off inside the box might have affected the plastic?

One older Kadee 803 package reads: "Contains: Acetal plastic." 

Spelling is everything in organic chemistry, Acetal and acetate are not the same at all.  On my trip down the web I discovered that Delrin is also an acetal plastic.   

I am familiar with Delrin.  Google's AnnoyingInsistence reaffirms that it's strong, slippery stuff, impervious to "most" solvents, but not all acids, bases, or oxidizing agents.

A thread on the Practical Machinist forum led to an industrial epoxy that works with Delrin, but the manufacturer states that surface prep and a primer is needed, and a 1.7 oz tube of just the epoxy is about $75.   

Kadee does suggest in their Whisker coupler instructions that to help keep the knuckle springs in place, a "tiny dab" of glue on each end of the knuckle spring would do.  Instructions suggest Duco.

I realize that gluing the knuckle springs is metal-to-metal.  I don't have any Duco, but I might get some as it was pretty handy stuff back when I was a kid.

Before I try a very narrow strip of blue tape around the assembly, and after getting it on the car, I could remove the 3 sides of tape showing, Does anybody have a trick because I'm out of extra centering springs.

[deemery]

Doesn't Kadee make a tool for that?

dave

[IWannaRetire]

Thanks, Dave.  I've got Kadee's #241 toothpick-like combination spring pic/uncoupler. As far as I can see, the other #1020 tool is just a normally-closed tweezer.  My current tweezer ends get in the way, but I probably should look at some different tweezers with finer tips.

[jbvb]

I'd try a tiny dab of Walthers Goo where the lid touches the 3 posts for mounting screws.  I think it would work to apply it to the top of the lid assembled to the box.  Not so much it would interfere with removing the coupler and box if you need to.

[IWannaRetire]

James, I've seen Goo mentioned a lot on different model forums, but haven't used it yet. I'm willing to try almost anything now.

So, along with more centering springs looks like I need to order better tweezers and a new glue...

[jbvb]

If you're in range of a hobby shop, almost all of them stock Goo.  You could also try whatever your local hardware store has for "rubber based contact cement".