ScaleTrains SD40-2 Railhead Rubbing Problem - Easy Fix Link

[robert3985]

Although I've posted this elsewhere as a comment, I thought that posting it separately would give it more coverage.

Although ScaleTrains SD40-2's are fabulously detailed N-scale models, some of them are having problems with the front of the plastic fuel tank rubbing the railheads and catching on any small track irregularity such as where there are rail joiners, guardrails, frog points, etc...., which can ruin the experience of having such a really well-detailed model running on your layout...if it doesn't "run".

I was in possession of an ST UP "Fast Forty" the last few days that had this problem, and the fix is very easy, with at least one caveat.  I'm posting a link here to my ten-minute solution, which is being well-received: https://www.facebook.com/groups/427105965735906/permalink/938079227971908/

Photo (1) - ScaleTrains UP SD40-2 "Fast Forty" at Echo Curve:


My explanation is pretty complete and I hope if any TRW members are having problems with their ST SD40-2's with low fuel tanks, this will assist you in fixing the problem quickly.

Cheerio!
Bob Gilmore

[Joe Cox]

Very interested, but some of do not do Facebook

Any alternatives?

J Cox
Austin TX

[crrcoal]

Don't need to be on FB to see his post on FB as it's a public group.

[spookshow]

I'm still trying to figure out why they glue those screws in. Morons! 

-Mark

[pdx1955]

I'm still trying to figure out why they glue those screws in. Morons! 

-Mark

It's possible that the glue is a factory fix for the loose fuel tank that Robert noted. This probably was not originally specified but "addressed " in a QC review along the way. Depending on if there is any solder bumps is probably the difference in making the fuel tank sit askew causing this issue. Clearly if you see the tank not parallel to the rails , you need to do this fix to avoid problems.

[spookshow]

The problem isn't a loose fuel tank, the problem is sloppy installation of the speaker that prevents the fuel tank from going on all the way.

-Mark

[Steveruger45]

I'm still trying to figure out why they glue those screws in. Morons! 

-Mark

Me too.  If they were trying to be sure they stay in then blue loctite, like they use on laptop screws would be the way to go.

[robert3985]

I'm still trying to figure out why they glue those screws in. Morons! 

-Mark

Y'know Mark, I've been trying to figure that out too.  Could be that if there's a glob of solder/flux/whatever near one or both speaker solder tabs...which prevents the plastic tank from fitting precisely against the flat bottom surface of the frame/speaker-enclosure...if you tighten the screws up too much, it cracks the plastic tank part...so, instead of making sure the tank is able to be positioned flush against the bottom of the frame/speaker-enclosure, they apply their canopy glue style adhesive to the screw threads so they don't fall out since they're not tightened properly.

Just a guess, since the reason the screws don't immediately go in all the way after cleaning up the lumps & bumps might be because of hardened canopy glue inside the threaded holes, making it impossible to see just how far into and tightly the screws could have been tightened if the threaded holes didn't have any glue residue in them.

BUT, torquing the screws strongly (but not strong enough to strip the threads from the holes) several times each makes them seat further into the hole, either by threading through the glue residue, or letting the steel screws thread the soft metal of the mounting hole walls further until they can bear against the plastic fuel tank's countersunk mounting holes without either hitting the end of the hole's threads or bottoming out in the shallow holes.

Oddly, the "lump" of solder/flux (I'm assuming) on the bottom edge of the frame/speaker-enclosure near one of the speaker's solder tabs, was painted over...which makes me wonder about the assembly priorities.  If I were painting and assembling the model, painting the frame (and masking it were necessary) would be done before soldering up the mounted speaker...not after it was installed and soldered to its speaker wires.

I am assuming that a human is responsible for soldering the wires too, but, MAYBE it's automated and the tip of the soldering fixture got out of adjustment and wiped across the bare frame/speaker enclosure, depositing a bit of molten solder to the bare metal...which I'm certain is what is causing this problem...either by a human or robot.  If those who encounter this problem on their models have that bit of hardened solder in nearly the exact same place on the frame/speaker-enclosure, then it's a good bet that it's a problem with their automated production line.

Cheerio!
Bob Gilmore

[turbowhiz]

It's possible that the glue is a factory fix for the loose fuel tank that Robert noted. This probably was not originally specified but "addressed " in a QC review along the way. Depending on if there is any solder bumps is probably the difference in making the fuel tank sit askew causing this issue. Clearly if you see the tank not parallel to the rails , you need to do this fix to avoid problems.

Some more data on this:

My example did NOT appear to have glued screws. The speaker connectors have wires presumably hand soldered on. The speaker contacts DO extend into interference with the fuel tank, even without the soldered wires. The design of the speaker itself that assumes a PC board mount, like found in say the Rapido -8 for example, so the contacts are effectively sprung. The fuel tank will not sit level without being screwed in place…Depending on how sloppy the soldering to the speaker is, it could definitely interfere with the fuel tank fitting correctly, nerveless even more sloppiness like seen in Bob’s example.

The theory that the glue came from some sloppy QA rework seems plausible.

[spookshow]

Got my supposedly repaired loco back in the mail today. It's still bottoming out though, so it looks like they didn't fix anything. Fortunately, the screws are now removeable, so I can try to fix it myself.

With my irritation level mounting, I'm anticipating assigning a very low grade to these pieces of junk...

-Mark

[Scottl]

No stake in this, but that photo indicates a gorgeous locomotive.  Sounds like a pretty minor fix.

[eja]

I'd say something about expensive models now, but you already know what I'd say, so I won't say anything.

[jagged ben]

...

With my irritation level mounting, I'm anticipating assigning a very low grade to these pieces of junk...

-Mark

That would be unfair.  It's an A+ model with a quality control issue.  Not junk.

[kiwi_al]

Got my supposedly repaired loco back in the mail today. It's still bottoming out though, so it looks like they didn't fix anything. Fortunately, the screws are now removeable, so I can try to fix it myself.

With my irritation level mounting, I'm anticipating assigning a very low grade to these pieces of junk...

-Mark

May I make a suggestion, Grade the DCC Sound Version low but separate the review for Sound / DCC and DC. The DC model doesn't have the fuel tank issue as there isn't a speaker in it so it fits properly. It runs pretty much like my Katos. Just a suggestion.

[spookshow]

I'm still not having any luck with this. The fuel tank appears to be straight and on as far as it can go -



But introduce any sort of grade change (say, by sliding a thin piece of styrene under the rail join) and that fuel tank is bottoming out -



What am I missing here? 

-Mark