Model Train Journal

I took the trucks and couplers off the Weaver 50 flatcar for two reasons.
One was to modify the center beam frame so that the trucks can rotate enough to negotiate O-27 curves.
The other was to remove the Weaver coupler and mount a Kadee coupler onto the flat car.
The trucks are surprisingly free rolling. One of them rolled off my desk onto the floor, where it did a sudden disassembly.



A small rod that allows the side frames to rotate and keep all wheels firmly on the track exploded off the side frame.
Maybe I can glue it on. I asked Gemini how to glue acetal homopolymer (polyoxymethylene, or POM-H).

Gemini said, "Yes, acetal homopolymer (POM-H, or Delrin®) can be glued, but it is notoriously difficult to achieve a high-strength bond with conventional adhesives due to its low surface energy and high solvent resistance. Cyanoacrylate, works through a rapid chemical reaction called anionic polymerization. The bond is incredibly strong due to molecular forces and also due to mechanical binding."


Looking at the break, I see lots of surface roughness. Maybe that will help the bond.



When I bonded Delrin discs at work, I used a two-step glue. Step one was to coat one side of the discs with a chemical that broke the surface Delrin molecules. According to the instructions, breaking the molecules exposed electrons to share with the glue. They look like they are already broken in the image above.

Edit 1: added "in the image above" to clarify where I see broken molecules.

I've never had any luck with that repair. The forces generated (on that classic lever arm) far exceed the yield of the bond over that small a surface area. Gemini isn't telling you that CA is strong only in tear and notoriously weak in shear. Knowing you, you'll want to try it anyway. GRIN!

When you have finished, send me your address and I'll send you a replacement for the basic truck assembly. I have spares. Keep your wheels to hand; those I do not have.

Thank you Sarge, that is mighty generous of you.

I will post the results and how I did or did not fix it.

We are up mighty early. I woke up due to pain from something I came down with late today. My wife was already up. She asked what woke me up. I said, "I think I caught the flu from Healey while talking to him over the internet."

Re: Weekend Photos - November 2025
Post by healey36 » Tue Nov 11, 2025 8:55 am

healey36+ wrote:Laying around the house, sick as a dog (no offense to the retrievers).

She was not amused as she accused me of being an idiot and explained that I could not catch the flu from someone on the internet.

webenda wrote:......Delrin®) can be glued, but it is notoriously difficult.........

Got that right.

Cyanoacrylate (CA) rarely works for Delrin and rarer yet with any strength.

There are some specific 2-part epoxy-like adhesives for Delrin and then there's a "welding" method that would seem inappropriate to the situation.

Replacement parts from Sarge is your best solution!

webenda wrote:"I think I caught the flu from Healey while talking to him over the internet."

Sure, throw me under the bus

I think I'm finally over that crap, although a lingering cough that'll probably go on for weeks given my history.

I did read recently in a ChatGPT thread that the flu can be transmitted by certain AI-generated posts (or was it viruses?)

We went through that with Celcon gears. Loctite sold me a solution that was supposed to prepare the gear for Loctite shaft. Didn't work.
The only thing that worked (other than a Woodruff key) was to knurl the axle. I did a lot of knurling for the Babbit folks.

I have piles of 3-rail junk. Even some wheelsets. Happy to send for postage. To anybody.

I followed the instructions that came with the Loctite Plastics Bonding System for hard-to-bond plastics.
Activator applied, wait 60 seconds, apply glue, and immediately put parts together, hold for 30 seconds.

Full cure in 12-24 hours.
I waited 2 hours before I snapped the fixed truck side into the bolster. Bond held.
Then I bent the side frames enough to insert the wheels and axles. Bond held.
All fixed, the Loctite two-part plastic glue works.

Then I twisted (shear force) the truck apart for the purpose of examining the bond.
It looks like 75% of the glue stayed bonded to the plastic parts. Mostly, the glue itself sheared when I twisted the truck.

Next, I will glue the bar back on and wait 24 hours before doing anything with it (this time getting the snap-together design, molded into the bar, pointing to 12 o'clock).

Add a reinforcing pin.

Rufus T. Firefly wrote:Add a reinforcing pin.

I have been using an open paperclip to guide the rod onto the side frame. This ensures that the rod is glued at right angles to the side frame and is located in the exact place of the break.


In the first glue-up, the paperclip came out easily. In the second glue-up, the paperclip is firmly glued in.

Rufus, it is bizarre that the paper clip accidentally got glued in, and you suggested a reinforcing pin at the same time.

The truck went together this second time just as it did the first time, except there is no twist; all wheels are on the level.


The Rufus Pin is barely visible.

Interesting!

Show us a photo of the stuff you used. Sounds very useful.

webenda wrote:Rufus, it is bizarre that the paper clip accidentally got glued in, and you suggested a reinforcing pin at the same time.

Serendipity; the Universe decides; ride the particle/wave........