(Edit) Altering the original intent (2/3rail operation). . You could reverse one axle on each truck to allow for pick-up from either outside rail via both trucks in the 3 rail mode.
Three rail only operation.
Would short the two rail mode.
Correction noted.
If you reversed an axle, you'd short between the rails, that will certainly screw up the two/three rail mode! 
How is that not "messing" with the original intent (2/3rail operation)?
This is a very interesting thread, it sounds as if the simple fix that GN John is talking about could be done at the 3R to 2R switch. Do all such engines from MTH have this switch?
This is one of the reasons why I love RK imperial products. I doubt if the 2-rail market would stand for anything less then Premier standars so I guess I'm safe.
Tender switches.
I do not have any steam with the 3/2 capability, however, I did have incessant issues with two geeps. The frustration with resulted in a 3/2 switchectomy! They run fine now.
Personally I believe by trying to make these engines all things to all people, they are becoming more tempermental. I concur that the simple RailKing offerings are much more robust. There was an initial problem with contacts in the trucks and a small brass piece was offered if pickup of power was insuffiecient. It wasn't, however, well publicized. FWIW
I can imagine either the polarity or 3rail/2rail switch could enter into this issue. I haven't looked at the inside of one of these yet.
Dunno about all the details above, but my big 3/2 ATSF 3463 Hudson would stop in
my GG switches when moving slowly. I discovered that some of the wipers were simply
not touching the axles. I adjusted/bent them and the 3463 is actually one of
the most electrically sure-footed locos that I have ever seen. Never blinks.
Hi D500, you would be surprised at how many tracking problems I have fixed by adjusting the ballast of a switch or a minor adjustment of the pick-up rollers.
I had an old Williams engine, an FM that would not take an O-72 turn. It turned out to be a power wire was a little to short to allow the motor to move through a turn, or a switch. Just goes to show ya, it's not always a complex fix to our problems. Sometimes it just takes a close look.
Hi All,
Sometime back I posted a problem with my MTH Railking steam proto 3, not sure
of the item # at the present, I am having issues when the engine is crawling through an Atlas switch, it just shuts down. When you push the engine past that point, it will startup and run. I was told to reposition the pickup rollers (turn them inward)to correct this which has not been done as of yet. The switch does have a power and common drop.
I am running 3 rail DCS. Is this the same issue as what is noted in this thread?
Mike CT, thank you very much for the comprehensive 2 3 rail information and excellent photos. My engine is not a project any more. I hadn't planned on it being one of my main runners. It looks great and it's fun to have.
Since my Run Room theme is a Texas South Plains Railroad, that engine was imported by a Texas rancher oil man while he was on vacation in Europe. The rancher really liked the engineering model. He even hired the engineer and conductor to come home with the engine. Engineer and conductor speak no english. That steam engine will pull stock cars and oil tankers when needed and it will be running fast through the yard until some of the coating wears off the wheels.
Do you think they are trying to do too much with a single engine? Seems to me they should have separate products for 3 rail and 2 rail. I think at one time MTH made a limited number of 2 rail engines.
Also, one of the suggestions in the Tips and Tricks publication from Kalmbach a few years ago had to do with insulating one of the outside rails to allow for future accessory activation. I did that on my layout to the outside third rail to allow for the installation of crossing gates ect.
My guess is that could cause a problem if only one of the outside rails of one of these MTH engines can pick up the common or ground.
Trianman9, I'm sure the convertible engines serve a purpose for some. For future purchases I will just be cautious and stear clear. I do use the outside insulated rail sections as track trips. The convertible engines would just add one more level of complexity and barrier to reliable running. I would rather run than work on engines.
For what it's worth, concerning Atlas O switches, there is definitely a "dead spot" in EVERY Atlas switch. This is the gap between the center rail and the corresponding twin-rail hot section near the point pivot area (I know I'm not describing it clearly). Anyway, the spacing of pick-up rollers on EVERY SINGLE 3-Rail locomotive, steam or diesel, or electric, MUST have the pick-up rollers farther apart than this gap (dead spot) in every switch. Thus, some locomotives, with pick-up rollers closer together than about 4 or 4 1/2 inches, will stop dead!
I have an MTH New York Central Mohawk that I had to add a third pick-up roller on the tender, in order to span the gaps in my Atlas #5 switches. No more problems now.
Hi
I have a steam engine MTH 20-3313-1 and it is a 2 to 3 rail type with the same stalling problem.
The locomotive is build with no power pick up and a rear trailling wheel truck with a wiper toutching the axels. The wiper is fixed on an insulated bracket. picture1
The right wheel are not insulated and they are in contact with the right rail (probably the power pick for two rail)
Picture 2 is the two to tree rail tender with the wiper on the front truck
Hope the picture will give you some clue
John
IMO There is a very good posibility that the 3/2 locomotives/units can be produced at the cost of either a 3 rail or 2 rail locomotive, and eliminates the need to set up a special production for limited two rail units. Hobbyist are either two rail or three rail, not a lot of change from one to the other. IMO
Usually switch (turnout) continuity problems are with the center rail. It's unusual to see an outside rail problem, but the 3/2 has the ability with it's isolated wheels to create that problem. The Decapod that I pictured has been a solid, trouble free runner.
I've also done an Atlas 6924 relay upgrade to my layout that has solve dead spot problems. Surprisingly, Jack, my Weaver E8's with pick-up rollers 14" apart could find back to back turnout dead spots.
Interesting discussion
Mike
See all engine improvements that were possible.
MTH 20-3383-1 2-3-1 Pacific Steam Engine
http://www.slsprr.net/features...0Pacific%20Steam.htm
Engine is now on probation.
Odd. I have an ATSF 3463 3/2 Hudson that was having exactly the same problems with
my GG switches. I suspected something complicated, but after looking at the wipers
I saw that a couple of them were not touching their axles. I gently bent them and this
4-6-4 will sail slowly through multiple GG switches (old and new styles,
with no special wiring) with nary a flicker.
I know that you've been through all this, but the 4-6-4's AC common-pickup arrangements seem well-designed - and my Chapelon 3-2-1 has never had a pickup issue.
GG and Ross (I have a few) switches are pretty similar, of course. Strange.
I had a customer with this problem which I traced to the 2rail/3rail and polarity switches. He said he wouldn't ever use 2 rail so I asked him if he wanted me to hard wire it for 3 rail. After bypassing the switches and hard wiring it for 3 rail it worked fine.
I bought a MTH Hudson 20-3313-1 used and I have the same stalling problem than your beautiful Pacific locomotive.
(The broken wipers were repaired with very little improvement.)
The ground strap(parts name) on the locomotive rear trailling truck is there for power feed (+) from the right side track when in two rail mode
To be sure compare the two wheels at the end of the axel. The left wheel is fitted with a plastic insulating bushing.The right wheel is straight mounted on the axel and conduct power.
My locomotive is built for two rails operation and then be switch in tree rails mode trought the 2 - 3 rails switch.
John
I have the painted version on the bench for a repair. The 2R-3R units do route both wheel sides to black power wire or Outside rails when in the 3R position. Only when the 2R-3R switch is in the 2R poisition does the wheel isolation come into play.
For this unit, the rear truck left wheels are connected to the tender chassis via metal bushings and a gray wire is routed to the polarity switch. There also is a gray wire with screw into the tender frame connected via wire nut.
The right tender wheels on the front truck are linked to the polarity switch via the wiper. They also are connected to the engine right wheels via harness. One issue is the blackened axle.
When the 3R switch is in 3R, the brown wire bringing roller power from the engine (and tender if equiped) goes directly to the PS-2 3V board red wire position.
The polarity switch (depending on which position) routes either the left or right wheels to the 3R-2R switch an directs it to the black 7pin connection.
The polarity switch sends the other wheel set to the 7pin ground connection via a direct connection from the polarity switch.
The main point being that when in 3R both left and right wheels from the tender and engine go to the outside rail position for board power.
If an engine is having problems then one of the switches, pickup points, tether wires, draw bar ground may be having issues. G
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