I was debating whether to bother taking shots of my coupler mods, and after close inspection, decided to do it. The piece I cut off was sitting on the bench next to the truck, so I snapped a pic.

You can see I cut off 3/4" and then drilled a hole for a 2-56 bolt. I’ve done this on many coaches in the past. But wait - what’s going on with the other truck in the background?

Aaagh - the couple mount has broken apart!

Most unusual - the plastic is usually fairly malleable and difficult to break. But there it was, with clean shiny plastic on each side.

Even more interesting, was the pieces left under the bolt, where it split down the middle.

Every now and then you get a very brittle piece of plastic - I recall a Bachmann hopper that I was cutting/trying to cut with the table saw. It just shattered rather than making a clean break or melting.

Guess I will have to make a new coupler mount. Anyone ever seen this before?

I found a piece of plastic in the ‘bits’ box and drilled it to fit. (Of course, I Loctite’d the bolt originally so it took some work to get it off.)

And here it is, all restored. I’ve glued the white pastic to the body of the truck, hoping it won’t swing around, and yes, more Loctite.

Pete

If you used Loctite on the screw to hold the coupler to the plastic truck therein lies your failure mode… Loctite (thread locking adhesive) and or any similar ilk, is NOT plastic compatible and is known to fail as such. I don’t recall the specifics (chemical reaction I think) but I learned of same when I rep’d for Hitec RCD. Hitec developed a plastic composite known as Karbonite for servo gear-trains, modelers that utilized a thread lock began to experience gear train failures on the output gear that looked eerily similar to your depicted failure. We couldn’t figure out why some had a failure modes while most did not. Eventually enough data was collected to understand the gear-train failure mode.

Michael

Yep, Aristo truck plastic can be finicky:

truck failure from chemical reaction to lubricant, journals just cracked.

If you used Loctite on the screw to hold the coupler to the plastic truck therein lies your failure mode…

Now you tell me. And I used Loctite again on the repair (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-surprised.gif). Hopefully it stayed on the bolt this time - I do recall a big blob seeping out onto one of the nut/bolts.

I’ve used Loctite 425 (135461) without failure for a couple of years on various plastic parts of Bachmann locomotives and cars. I have only had to disassemble one of the screws, it came out with a bit of difficulty but I could see not see any damage to the threads and reassembled it with no issues. These have been metal screws into threaded plastic components.

I wasn’t aware plastic compatible thread lockers were available. I looked up the cut sheet on Loctite 425, its a cyanoacrylate composite developed to be used with plastics verses the anaerobic adhesive offerings. Cyanoacrylate is typically realized as Super or Crazy glue, which is what I have used and or recommended for said purpose (very sparingly). Loctite is very proud of the 425 adhesive at about $20.00 for a 20 gram bottle. Also appears to have been released 2007 or so, several years after I learned of the compatibility issues with plastics and common thread lockers.

I’ve also used products with a viscosity (similar to silicone) such as Shoe Goo, PFM, E2000 and similar products with great success. You don’t need more than small dab on the screw threads or the screw head in my experience.

Greg alludes to a commonly overlooked consideration, i.e., “PASTIC COMPATIBLE LUBRICANTS” for gear-trains and such…

Michael

I’ve also used products with a viscosity (similar to silicone) such as Shoe Goo, PFM, E2000 and similar products with great success. You don’t need more than small dab on the screw threads or the screw head in my experience.

I was about to comment that almost any glue will stop a small bolt from unwinding, as long as the glue adheres to the metal and they are clean. I have some gel superglue, and some gorilla glue that will work.

I think the one that failed was due to an excess of Loctite thread-locker. It was hard to get the nut off the bolt afterwards. The two bolts now seem stable - no sign of weakness - and both have a small dab of loctite on the top and thus in the nut’s threads.

I put the trucks back on today as I want to get going with the other 3 cars. I noted that the retaining screw has quite a bit of play - it doesn’t snug down onto the truck, which is good. However, at least one source says loosen the trucks 2 full turns of the screw - if I did that they’d fall out! Anyway, there’s no need - lots of looseness as they are. (Maybe an earlier iteration had a flush screw?)

Anyone have any good reason for putting the screw back over the slot to prevent it swinging too far? I can’t see why it’s needed, as long as I am not mistreating the coach.

That screw and washer keeps the truck from rocking upwards at the end, helps keep coupler height. I would put it back on.

The amount it swings from side to side is controlled by the boss in the slot, screw or not (unless it comes out as above)

Greg

That screw and washer keeps the truck from rocking upwards at the end, helps keep coupler height.

Well, as Aristo couplers refuse to uncouple, I can’t see why it matters. I like ,lots of vertical movement in my trucks!

It matters if you change to Kadees. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

Undue upward motion at the outer end of the truck could cause the coupler shank to rub and catch on the chassis, which, Aristo couplers or not, would normally cause derailments.

This is a long truck, with a long coupler shank, so excessive up and down motion would be “amplified” at the couplers. It’s also not pivoting in the center of the truck, which can cause other issues, especially with how it is sprung.

Aristo never did anything that cost extra money in parts or assembly costs unless there was a good reason.

Greg

Undue upward motion at the outer end of the truck could cause the coupler shank to rub and catch on the chassis, which, Aristo couplers or not, would normally cause derailments.

Greg, that doesn’t make practical sense. If the track is so uneven that the truck is moving to the extent it rubs the coupler on the body, then preventing it moving is also going to lead to derailments. No?

I guess I did not write very clearly. I will try again.

Not controlling the up and down motion of the end of the coupler could cause derailments by the shank catching on the body when the coupler is “up”.

You asked if you needed to put the other screw in. I commented it can serve to control the up and down motion of the coupler.

Also, it’s not just uneven track, as I stated, the truck is not pivoted in the center, the shank is really long, the pivoting of the axles is all goofy, the center axle is not sprung, so a number of things can cause up and down coupler movement on this particular truck…

This is why Aristo put the “shelf” on the bottom of the coupler knuckle to prevent over-riding would be my guess. Locking the couplers together to prevent this covers a multitude of sins. In the prototype, you normally only see this level of protection on passenger cars (although I believe it was on certain freight cars)

Greg

Ahh, don’t ya love it when you have multiple motions and forces interacting in three dimensions.

I’ve studied these trucks a bit, have HW cars in new and old style, changed to body mounts, modified the trucks to make more even springing, modified the bolster rib, etc.

All the asymmetries and elongated parts make certain things more difficult. For many years to “common wisdom” was to eliminate the center axle or change to 2 axle trucks. All my cars have all their axles.

Greg

Greg, I don’t doubt you are right about the trucks. I’ll see how they perform for me and then reconsider.

They certainly worked this afternoon, but Riverbend’s track is on concrete and is pretty well laid. The only problem I had was the coupler heights, as I rushed to finish the shortened shanks on the combine last evening and didn’t check the heights. That’s why it is running with the baggage at the wrong end!

Unusual to see a steam plume in Florida. It was a very dry atmosphere.

Pete Thornton said:

Aaagh - the couple mount has broken apart!

Most unusual - the plastic is usually fairly malleable and difficult to break. But there it was, with clean shiny plastic on each side.

Anyone ever seen this before?

Yes I have seen this before numerous times however not even where a mounting point is but in the middle of the coupler tang itself

Pete Thornton said:

Unusual to see a steam plume in Florida. It was a very dry atmosphere.

Did we go from diner trucks to unusual steam plumes videos as I know you guys prefer to stay on topic ?