Operating a PS3 Engine on a 3 Rail Layout With ABS

Interesting, never thought about it. The only way around changing the axle/wheel sets out? You'd have to common the wipes. Seems easier if possible to replace lead and trailing truck wheels. Don't think they common the axles in "3R" on any 2R/3R.

How well do theses engines work on non derailing switches then?

I was under the impression that the 2-rail/3-rail switch shorted the outside rails in 3-rail setting.

John,

I was under the impression that the 2-rail/3-rail switch shorted the outside rails in 3-rail setting.

That's been my understanding, as well.

That was ours as well. Don't have any PS3 steam to verify it on.

Gentlemen

On a steam locomotive, all the 2 rail/3 rail switch does is to divert the "hot" pick up from one side to the pickup rollers.  So in the 3 rail position, the wheels on one side are electrically isolated from everything.   

Here's a clip from such a locomotive tender, note that the switch is supposed to connect the right and left wheels in 3-rail mode.  That's what I always assumed happened.  These switches are a frequent source if problems, so that may be the first place to look.

It would seem you are mistaken on this belief if my MTH documentation is to be believed.

Both sides have continuity when the switch is in 3 rail on my PS3 engines. None in 2 rail.  Maybe a bad connection on the straps on the trucks or a bad switch.

Gunrunnerjohn,

Thanks for the schematic. I stand corrected. But neither my L1 nor H10 show any connection to the right side drivers or tender wheels with an ohm meter with the switch in the "3 rail" position.  It is entirely possible that the switch is bad as suggested by Joe.  (It is unlikely the wipers are messed up, as then it would not run in 2 rail!) The original poster might want to check for a faulty switch.

There's no certainty that MTH was consistent in that wiring of all of them, I just looked in the service book and found that diagram.

I'd probably look at the switch first, as I've seen comments in the past about issues with the wiring of those.

It is unlikely the wipers are messed up, as then it would not run in 2 rail!) The original poster might want to check for a faulty switch.

I didn't see anything suggesting it had been run in 2 rail.

Joe

Just to clear up the confusion:

It is unlikely the wipers are messed up IN MY CASE as then it would not run in 2 rail!.  

OK, that's why I was confused. I thought we were talking about the original posters engine.

I have two 2R/3R PS-2 steam engines.  When you through the switch to 3R you get left right conductivity.  BUT, a big but, this is not in a set of wheels on one axial.  May be the front right to the rear left.  You have to check all possibilities.

Ron

Obviously, only the wheels that have wipers will be common as that's where the connection is made.  I know the early MTH 2-rail stuff had the tender wheels insulated on one side, and the locomotive wheels insulated on the other side.  Truthfully, I don't know what's current, and I don't have one on hand to look at right now.

I have had very little time to do additional testing.  With the locomotive and tender connected electrically through the drawbar and the switch set at 3Rail, I get the following results with the locomotive and tender lying on their side:

The right front and left rear wheels of the tender do have conductivity.  The locomotive is a 4-8-4 configuration.  None of the locomotive wheels have conductivity.  However, when I ran the locomotive through a non derailing switch with the switch set in the wrong direction, the switch changed immediately when the front truck hit the sensing rail.  These findings don't add up!  I am having a lot of trouble duplicating test results.

I plan to do more testing and will post results.  All of the assistance is greatly appreciated.

I have now had some time to do some additional testing.  Keep in mind that the locomotive we are discussing is a steam engine 4-8-4 PS3.  My layout utilizes  Ross switches and curves.  The straight track is Gargraves.  All track is mounted on cork roadbed which is glued to homasote.  All electrical connections to the track are soldered.

The 2/3Rail switch appeared to be in good order.  I took the casing off of the tender; the switch is DPDT.  In the 3Rail position, both poles were a dead short between the center commons and the 3Rail end of the switch.

I tested the tender for wheel continuity.  The right front wheels and the left rear wheels have electrical continuity.  These same wheels also have electrical continuity with the 2 left wheels on the front truck of the locomotive.

I ran the engine on a continuous non ABS loop, with the engine going ccw in the forward direction.  I also put the engine in reverse with the engine going cw.  I then turned the engine 180 degrees so that it went forward in the cw direction.  I also ran the engine in the reverse direction going ccw.  No matter what I did, the locomotive ran flawlessly.  Keep in mind that this is a DCS loop with the inner rail of the loop as the ground.

I next ran the engine on a continuous ABS loop.  The inner rail serves as the ground for both the DCS and ABS.  The outer rail serves as +12VDC for the ABS system.  I first ran the engine in the clockwise direction.  I then ran the engine in reverse going ccw.  The engine again ran flawlessly.  Keep in mind that left rear wheels of the tender were on the outside rail.

I then turned the engine 180 degrees and again ran it on the continuous ABS loop.  In this mode the left rear wheels of the tender were on the inner rail.  Whether I ran the engine in forward or reverse, it would randomly come to a quick stop, shut down and have to be restarted.  Then I ran it again.  If it stopped quickly, I pressed my hand on the left rear of the tender and it continued to move.  I did this every time it stopped, and the engine continued to move.  It appears that lack of good electrical continuity between the left rear wheels of the tender and the inner rail is the problem.

I then checked my non derailing switches.  If the left side of the engine activated the non derailing feature, the switch automatically changed positions.  If the right side of the engine “activated” the non derailing feature, the switch did not change position.

I’m not sure how to rectify the above problem.  I suspect one solution is to deactivate the ABS system and electrically tie the two outside rails together.  I really don’t want to do this; as the ABS system incorporates route signaling utilizing searchlight signals from Custom Signals.  Any advice is appreciated.

Let's assume you're never going to run in 2-rail mode.

I'd look into changing the wheelsets of the tender trucks to standard 3-rail solid wheelsets, that will solve the issue of the continuity.  You could also change the leading and/or trailing truck on the locomotive for different wheelsets.

I’ve done some additional testing based upon Gunrunner John’s suggestion.  First of all, the engine we are discussing is a PS3  4-8-4 Premier steam locomotive, Great Northern 20-3500-1.

The locomotive front truck and rear truck all have insulated wheel sets.  Likewise, the 6 wheel sets on the tender also are insulated.  I have a 6 axle tender from an older PS2 Premier steam locomotive; these wheel sets are not insulated.  I swapped 3 of the wheel sets from the PS2 tender and put them into the rear truck of the PS3 tender.  The PS3 tender then had 3 wheel sets which were insulated and 3 wheel sets which were not insulated.

I ran the train all over the layout in all directions with the ABS system operating.  Everything worked perfectly.

I called my dealer and explained all of this to him.  I asked him to acquire non-insulated wheel sets for the locomotive front and rear trucks and the 6 non-insulated wheel sets on the tender (a total of 10 non-insulated wheel sets)  Apparently MTH doesn’t make such a product, so he is not able to obtain the wheel sets.

Gunrunner John  - do you or anyone else know where I can obtain some used wheel sets that will work on this locomotive?  I greatly appreciate your suggestions.

I don't know where you'd get them.  I have another idea.  Is it possible to somehow bond a wire from the axle to the inside of the insulated wheel?  I don't know that you can solder to it, but a really tiny screw in the back of the axle with a wire from the screw to the axle would give you continuity.  Somewhat of a kludge, but any old port in a storm.

 I'm not sure about this...

I had thought that MTH released some models where the outside wheels were not bonded when in three rail mode?

 I believe after some replies, the wiring was changed to make sure they were connected?

It really does not matter. If his loco is not wired that way, then it needs help. I would think he could rewire inside easier than adding anything extra? The wiring is there, just not connected correctly on the three rail side of the switch, right?

It sounds like the wheels are insulated and there is no way to connect the sides.  I know some of the wheelsets are just insulated on one wheel, there's no easy way to fix that without some hacking or changing the wheelset.

 Just to make myself clear, there must be some way of picking up power from each wheel side in two rail mode, right? The pickups/wipers are already installed and wired.

 When in three rail, the insulated side should connect to the frame (ground or what ever you'd call it) side, right?

 I'm not sure what needs to be hacked? Just add a jumper wire. I maybe overlooking something obvious??

One wheel on each axle is insulated, and the insulated wheels are staggered left to right.  I don't have one of the switchable ones here now to look at.  I believe one is waiting at the shop for repairs, maybe I'll have a better idea when I look at the details.

Here’s what is grounded and what is not.

This engine is a 4-8-4, and therefore it has 8 axles.  I will call them axles 1 thru 8, and the wheels will be either L (left) or R (right).  The tender has 6 axles and I will call them axles 9 thru 14.

1.  On the tender, 9R, 10R, 11R, 12L, 13L, and 14L are grounded together.  Wheels 9L, 10L, 11L, 12R, 13R and 14R are insulated.

2.  Wheels 1L and 2L are grounded together.  They are not grounded to anything else.  Wheels 1R and 2R are insulated.

3.  Wheels 7R and 8R are grounded together and are also grounded to the ground wheels on the tender.  (See 1.)  Wheels 7L and 8L are insulated.

4.  Wheels 3R, 6R, 7R and 8R are grounded together and are also grounded to the ground wheels on the tender.

5.  Wheels 3L, 4L, 5L and 6L are grounded together but not to anything else.

6.  Wheels 4R and 5R are not grounded to anything.

7.  Copper wipers are on axles 7 and 8 and also on axles 10 and 11.

Because only the right front wheels and left rear wheels of the tender are grounded together, poor grounding conditions occur when most of  tender weight is on the left front and right rear wheels.

I don't see a way to fix this without either replacing the wheel sets with standard 3-rail ones or doing the kludge that I suggested to connect the left and right wheels in some of the insulated sets.

Personally, my opinion is the MTH 2-rail/3-rail switching is poorly thought out, many folks use a rail for signaling.

 It's always tough to just imagine this stuff in mid air without seeing it.

"5.  Wheels 3L, 4L, 5L and 6L are grounded together but not to anything else."

  I would have to ask if these wheels are picking up power in two rail mode? I guess they might not be? If they were, that is where they would need a jumper to the three rail switch side. That's if I'm imagining any of this correctly. That's a big "IF"!!

 That is also where John would be correct in saying that something would have to get bashed. Again, If I'm guessing correctly?????

Joe, the MTH 2-rail stuff I've worked on has an insulated wheel that doesn't connect to anything on one side of each axle.  If these are the same, there's no way I can imagine fixing it without one of the measures I suggested.  Obviously, the easy way would be to find standard wheelsets that match the insulated ones for the leading and trailing trucks on the locomotive.

I think the Wheels 3L, 4L, 5L and 6L are grounded together Should have a connection to the 2-rail/3-rail switch, perhaps that's one issue here.

As I mentioned in a earlier post, the two right wheels on the front truck are insulated  wheels.  If the engine is going over a non-derailing switch that requires a right rail activation, the switch will not change position until the 3^rd axle of the locomotive activates the rail.  This is a rather poor design.  MTH would have been better off to offer the engine in either 2 rail or 3 rail and not utilizing a switch.

At any rate, the only viable solution seems to find some wheel sets from a PS2 locomotive that have a relatively close match to the wheels that came with the locomotive.  PS2 steam locomotive wheel sets appear to have both wheels grounded.

Does anyone know of any hobby shops or repair shops that may have some proper wheel sets on hand?  I need wheel sets for the front and rear truck of the locomotive as well 6 wheel sets for the tender.

Can you make some sort of jumper from the insulated wheel to the axle? They make conductive epoxy. Could you put a ring of that from the wheel to the axle to bypass the insulator on the wheels?

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It has to work that way to operate properly in 2-rail mode. If you check the tender, you'll also see that the wheels on one side are insulated. The 2-rail/3-rail switch basically throws the hot pickup from the right side wheels on the tender to the center rail lead coming from the locomotive. We've had locomotives stall from a loss of ground signal at low speed at a "switchover" point in an insulated rail sensing area (insulated rail moves from the right over to the left -- you end up with all the wheels on the insulated rail instead of ground.

A work-around for this would be to put a couple of wheel wipers against the treads on the insulated wheels of the tender and tie them to the axle. This would turn the factory insulated axles into non-insulated axles without being permanent. You'd lose 2-rail mode but you'd get a tender that shunts the circuit. You would, however, create a short-circuit if you switched to 2-rail mode and tried to run it on 2-rail track.

Thanks Matt!

I only run in 3 rail mode, so a short circuit in 2 rail mode wouldn't happen.  One of the major problems seems to be the tender; this is due to half of the wheels being insulated.  As a result, sometimes the ground path isn't as good as it should be.

Just curious, did you check with MTH to see if they have the wheelsets?  Also, you won't have to replace them all, just a couple of sets I would imagine.

My dealer who sold me the locomotive said that he had contacted them, so I haven't tried calling MTH.  Perhaps I should.  Is the lady I should talk to named Midge?

Yep, if anyone can find them, it'll be Midge.

I contacted Midge today.  She stated that they do not stock wheel sets for locomotives.

Someone must know somebody who has some wheel sets on hand.  I did place a "wanted to buy" topic on this forum, but no response as yet.

You may have to consider the kludge I suggested.

Somewhere down stairs, I have 3r wheel sets that came out of my engines. I did convert an Allegheny to two rail. I have a few more that need converting, that I'd love to trade for insulated wheel sets. Trouble for me is, I don't know what exact wheels you are after. Some aren't even MTH.

 I'd have to figure out the axle shaft ends (pointed? angle degree?), exact axle lengths, wheel diameters, etc., that you need, because I don't have that engine.

 Most of us two railer's have to add wipers at some time to help out poor designs or conversions. It's actually pretty easy.

There is another work-around. You can take the tender trucks apart and reverse half the axles. This should short the trucks -- i.e., ground both sides.