2-rail DCS Upgrade

with PS2, you really need that switch, to make things easier.

Powerpick-up points must be good even though it has a battery. I try to get the power from the farthest points that I can to allow for traveling slowly over large switches.

 I think of more.....maybe ask Barry???

Polarity Reverse switch? How about a hefty Bridge rectifier instead, Sure, you lose a bit of voltage but no polarity reversing needed.

Its anoying that the ps2 boards already have a big bridge rectifier, but it expects the dcs signal on the "red" lines, which is probably the only reason a polarity switch is needed for dc operation.  I would expect another rectifier just used to route the dcs signal to the proper power inputs would work.

So what are you supposed to do with the pickups on each truck when you go through a reverse loop?  Would you need a rectifier on each truck to avoid shorts?  Is shorting out on a wheel between reversed sections ever a problem?

Eric

When a MTH engine loses the signal, it continues doing whatever it was last directed to do.

 There always seems to be questions about how they act. You would treat them the same as other DC engines on your track (if you're using DC).

I don't think the rectifier would work.

 

John, Not knowing the make the only thing I would do is make sure I knew which wheels were common to the chassis on both engine and tender, and which wheels where isolated as a group.  Then use a polarity switch as Joe mentioned.

 

The tender ground wire that MTH has on the harness of some steam will have to go to the switch not the chassis too. 

 

Otherwise straight forward.  G

I have converted, or have had converted, about a dozen or so 2 rail locos to PS2. What GGG said is true, and about all you have to worry about.  If you can convert 3 rail locos, you can convert 2 rail locos just as easy. 

Thanks guys.  I suspected it wouldn't be a big deal, but I figured why not float a query and make sure there's not something oddball that I'm missing. 

 

I'm planning on including the polarity switch, can't hurt.  The victim is an MTH Premier 2-rail that basically has nothing but a smoke unit, no sound or other control, so there's lots of space to work.

Interesting discovery.  The insulated wheels on the tender are on the opposite side of the insulated wheels on the locomotive! If I were to connect the frame of the locomotive to the frame of the tender, I'd be shorting the tracks.  I wondered how this was working, but I discovered the drawbar is insulated from the locomotive frame.

 

This would indicate I'll have to swap the tender wheelsets around to get them on the same side, correct?

 

That's how the PS1s get their power.

Joe, you'll have to explain that one.  Are you saying that's by design? 

 

I couldn't find any wipers on the wheels, so maybe what you're saying is the frame of the locomotive and tender are by design running on the opposite rail track power?  That's more than a little odd, but perhaps that's the way it works.

 

I just looked again, and sure enough, the frame comes over to the power through the tether!

 

That's one from left field that I didn't expect!

 

With 2rail steam engines usually the engineers side picks up the positive and the opposite side of thetender picks up the negative. My 3rd rails is like that. The tneder picks up the negative and when they are connected it will run but if they're not it won't. 

 

Also it sounds like someone ripped everything out. All of mine have wipers on the tender.


Ralph

I don't see any evidence that there was ever any pickups on the insulated wheels of either the locomotive and the tender.  I always thought that they had pickups and that the engine would run alone.  Many HO locomotives work that way.  However, at least for this MTH Premier model, that appears not to be the case.  It's wiring also reflects the way it is configured, and there is nothing to suggest this isn't the factory configuration.

 

Naturally, there is very little information on the MTH site about 2-rail in general, specifically how it's wired.  Nothing has been ripped out, the tender has one wheel on the wheelset insulated, and the other brings the track power up to the frame.  Since they depend on the two truck screws on the tender to provide power, I think I'll run a wire from at least one truck to get a better connection.

 

no wipers. insulated wheel sets on one side only. reversed on the tender for power pick-up.

You're right Joe, just not what I expected.  I don't routinely do 2-rail stuff, so all I've seen is HO stuff with the wipers.

 

All of my engines have wipers. The one is my 9000 which is a PS2 with the 10 pin drawbar and the other two are PS3's and I haven't changed a thing on the two PS3's. The 9000 I put NWSL scale wheels on the tender and wired it back up as it was from factory. Just interesting as to what you have. But if it works it works.

 

Ralph

 

Since it's a fully intact locomotive at this point, I put it on the track and applied DC.  True to form, it ran, reverse the polarity and it ran backwards.  It was obviously designed without the wipers.  I do note that the trucks on the tender have two holes that could be for optional wipers, and I suspect it would be more reliable with them.  However, I'm pretty sure it didn't come with them, the holes are not threaded and clearly have never been used.

 

 

Did MTH make a 2 rail PS1? I never saw one. That's interesting.

Ralph

This one is conventional with no sound.  According to the documentation, PS/1 requires AC, so I don't know that a 2-rail version with PS/1 was available.  Joe should know, he's into 2-rail.

 

 

There were several models. They had a board inside and were meant for DC only. no sound. I bought one (Allegheny) with a smoke unit inside!

http://mthtrains.com/content/20-3017-2

I should never had said PS1, sorry. It was it that time frame when these models came out. The two rail versions were without sound and DC only.

now if I could find this other holly grail loco cheap....

http://mthtrains.com/content/20-3021-2

http://youtu.be/dGW7xeEz_Uk?li...xZM9pcZwOpkZrcdHggpg

https://www.youtube.com/watch?...xZM9pcZwOpkZrcdHggpg

 

This one has a small board in the tender (very small), and a little constant voltage board in the locomotive.  It does have fan driven smoke, and that's about it.

 

what model # is it?

Joe, it's the MTH 20-3036-2.

BTW, how are reversing loops handled in 2-rail O-gauge?  Curious what happens when polarity on the rails changes, I'd assume the obvious.  It this the same has HO?  What about DCS operation with DC on 2-rail?

Reverse loops are handled just like HO scale, that is block the loop so while the train is in the loop you can change polarity on the main via toggle switch or a reverse loop electronic thing-a-majig that swaps polarity automatically. What sucks about PS2 is if any other engines are on the mainline when polarity is swapped you either lose control of them via the dcs remote or they stop

 

PS3 will be real blessing as those polarity problems disappear. I have one 2 rail engine w/ PS3 in it and when the rail polarity is changed while the engine is running it doesn't notice it  

I was wondering, I suspect I should inform the guy that I'm doing the conversion for BEFORE I actually start it about such issues.  He may want to rethink converting this to PS/2.