BLI Pennsylvania M1a/b

[Chris333]

I certainly know nothing about DCC, but I have been reading about Bachmann On30 locomotives with sound. It looks like the only way to wire capacitors to their decoders is so they keep the sound alive and not the locomotive.

I have a Bachmann 2-8-4 and a Walthers 2-8-8-2 with sound, both running on DC only. But when ever the sound cuts out the loco stops as well.

[peteski]

I certainly know nothing about DCC, but I have been reading about Bachmann On30 locomotives with sound. It looks like the only way to wire capacitors to their decoders is so they keep the sound alive and not the locomotive.

I have a Bachmann 2-8-4 and a Walthers 2-8-8-2 with sound, both running on DC only. But when ever the sound cuts out the loco stops as well.

Do you have any specific source where that is stated (and maybe reasons given)?  Most sound decoders are integrated into a single unit (sound, motor and functions are all together. There are at least 2 levels of filtering caps in those circuits. One is the raw rectified voltage (this is where the true keep-alive supercap circuit gets usually attached).

Then there is a smaller filter on the regulated voltage side. That circuit keeps the decoders microprocessor (microcontroller) supplied with steady regulated voltage.  If additional cap was added there, that would only keep the processor running. But that is a low current circuit which is not designed to also charge up a large capacitor.

I suppose there could be a separate audio processor and a separate power supply for that which also used filter caps.   Installing a larger capacitor there would keep the sound processor and audio amp powered. But without the main processor (which also talks to the audio processor) that would be pointless.  In my experience with decoders, all the different sections of the decoder tap their power from the main rectifier and its filter cap (where keep-alive is usually installed).

[Chris333]

Maybe it all depends where you tap in:
http://www.railroad-line.com/discussion/topic.asp?TOPIC_ID=42624&whichpage=1

http://model-railroad-hobbyist.com/node/13337

[Lemosteam]

Well, I figured out how to double-head the M1's. Removed the dummy coupler. Took one of FVM (former unimates) dummy couplers, cut the back off of it which left a small square shape on the back of the coupler. Shaved it down just a bit and it fit right in the original coupler hole in the pilot without having to cut into the pilot at all.  Used CA to attach (not ideal, but it works).  Ran it around the layout and it works fine on my 19" radius curves. Since it doesn't swing side to side, I'm not sure how tight of a radius it will work on, but it works for what I need.  Got both of them weathered up and added coal to the bunkers.  They're ready for revenue service.  Was pulling 50 MT 33' loaded hoppers around my layout with no issues (I don't have any more hoppers, but they would probably pull 60-70 cars).  I'm happy.

Nate

So has anybody tried to shove an MT 905 in there?

@Nato did you add a screw?

Curious as my test coupler was both a success and a failure.

The successful part is the coupler inserted into the OEM pocket as intended and survived an @eric220 gauntlet of pull testing (thank you for your effort an willingness and all photos and images are courtesy of eric220). 

The first test was a grueling head to head, pull-off, of two massive M1's yanking in opposing directions.  I am quite surprised at the durability of the FX

https://goo.gl/photos/an1YQnW7YUZ3TJqw6

Thew second involve yanking a long train up eric220 's massive helix:

https://goo.gl/photos/o2nMKtR1gny5P7Mi6

The failures are that this think is butt ugly on the loco and friggin' HUGE- I must have accidentally scaled something wrong.  Also a fail was the two couplers had to me manually assembled.

These pictures help to show the issues:

You can see that the coupler is scaled much larger than the MT coupler that is on the tender of the loco.



Here you see how huge it is relative to the loco's pilot 



Here you see how the coupler looks from a 3/4 front right side view    Thinking that Neolube dipping would diminish the size a little visually but still not enough to be acceptable.


So while ther failures are cosmetic, the next steps would be to carve the design down to fit the MT coupler better, and have the shape mimic a real coupler a little better with some added detail such as a release pin and simulated pivot recesses, etc.

So I ask based on the failures and successes, should I pursue this or just let the design go as a failed experiment?

[chicken45]

Pictures are showing up as private, @Lemosteam

[peteski]

Maybe it all depends where you tap in:
http://www.railroad-line.com/discussion/topic.asp?TOPIC_ID=42624&whichpage=1

http://model-railroad-hobbyist.com/node/13337

That's a lot of reading! I skimmed through the first page of the thread and I decided that without me having the decoder in hand (to trace the circuitry), I'm not going to put any effort into figuring this out. On3 is not something I'm ever planning on getting into, and I'm not a big fan of Tsunami either. 

But I did ask for it - thanks Chris.

[eric220]

@Lemosteam as I said in private, go for it!  The buy from Shapeways, dip in neolube, pop in place is by far the simplest and most elegant solution. I didn't mention it before, but the height of the coupler was actually dead on with the tender coupler that it was attached to.

[eric220]

A little update. @Lemosteam revised his design, and I gave them a test. Here's the old, the new, and the original dummy coupler.



And here's the new coupler coupled to a second M1.



I put it through the same stress tests as the original design, and the new design performed admirably. The two locomotives worked together to easily pull a train that was too much for one locomotive through grades, crossovers, and radii down to 15". Coupling and uncoupling, although requiring the 0-5-0, was fast and simple.

From my perspective, I would be content to use the test samples that I got for these tests on my locomotives. Does anyone have any feedback?