PS2 Mikado 2-8-2 20-8007A stops on SOME switches

Sure, Place a piece of electrical about 3 inches long on the center rail. Park one roller on the tape, the other roller on the bare center rail.... Will the engine fire up with the one roller? repeat with the other roller.

Or use a continuity meter  at the work bench and test for continuity between both rollers.

tested good continuity between the rollers while on the work bench.

Found an interesting thing - there is one truck on the tender that has a brass strip across the axles to send the 'common' to the boards.  I could not get continuity between the axles and the brass strip.  That is where I will start in afternoon tomorrow.

I have seen many smaller locomotives, steamers and diesels, stall on switches, it's not an unusual issue.  For steamers, one cure is add a roller to the tender and share the track power.  This has solved the issue for me for a number of small steamers.  Sharing the wheel connection is a good move too.  I use a 2A trip PTC in the track power wires between the units to protect the tether wire in the case of a derailment that shorts a roller to the outside track.

Problem probably is not rollers, but ground pick up. On locos lacking a trailing truck, loco may lose ground contact on switches.  You are on track with wiper.  That may cure it.  Be sure there is a wire from wiper to tender frame; if not, add one.

Actually RJR, my experience is opposite of yours.  More often than not for me, it's the center rail pickup over switches that is the issue.  I can't argue with additional outside rail contact, but that isn't my usual issue with stalling on switches.

John,

What is a PTC? Where can I get them? Is it a push button reset? Like the idea, excellent!!!

        Steam Forever

           John

GRJ, I've only had the lack of ground issue with one loco, an RK 2-10-0.  When going over a non-derailing switch with a slight bump in the tracks, it would lose ground as the driving wheels rose,  MTH had failed to include a wire between wiper and tender frame.

On locos with a trailing truck, MTH usually has a wiper and wire to assure proper ground pickup.  Loco becomes more sensitive when it lacks a trailing truck.

Many decades ago, when I ran Lionel pre- & post-war, I found tender rollers surfaces would often gum up, so that the whistle wouldn't blow.  I found that adding jumper wire between loco and tender solved this problem, because the sparking burned the dirt off.

John J. Giuliano posted:

What is a PTC? Where can I get them? Is it a push button reset? Like the idea, excellent!!!

A PTC is a self-resetting fuse. It protects the wiring in the case of excessive current, but will reset when the overload is removed.

Here's the one I use: Littlefuse AHEF100

I've had similar issues with Gargraves and Ross switches.  With both, there is quite a long connectivity gap on the frog side of the outside rail.  I have found that if the plastic part of the frog is slightly higher than the metal rails, it will cause the engine to slightly lift off the other outside rail.  This coupled with rubber tires causes the engine to stall.  

Try running the engine in the opposite direction through the switch.  If it goes through the switch, you are likely to have an outside rail connectivity issue.  If it still stalls, the center rail connectivity is suspect.

Tony

It is engine dependent, and with 2R-3R engine, it very well can be the wheel pick up especially on switches with isolated outer rails.  G

With the 2R-3R, it's a different kettle of fish, I agree that the outside rail can be the issue sometimes with those.  I rarely see outside rail issues with a locomotive that truly has all the wheels common, far more often it's the fact that the locomotive has only two rollers and they're closely spaced.

Obviously, every situation is unique and requires an analysis of the situation at hand.

Problem solved!!

This afternoon I replaced the battery with a BCR2 and cleaned one side of the wheels on each tender truck.  For some reason, MTH uses insulated one side tender wheels, different side for each truck.  Checked continuity, then cleaned the wheels.  While at it, I cleaned the locomotive drivers and roller pick-ups.  Ran over the lower level of the layout, with many Ross switches,  at both moderate and slow speeds.  Even reversed and ran over the questionable stopping switches.  Ran perfect.  Guess it was a combination of battery strength and dirty contacts for the common rail.

Thanks for the response.

bruce

When you're switched into 3-rail, both sides of the tender trucks should be frame ground.  The reason for the insulated wheels is when you switch to 2-rail mode, you need insulated trucks.

What size Ross switch? When it stops, if you wiggle it does it start right up? Does it do it in both directions? Had an MTH F A-B-A set and it used to stop all the time at a crossover. After adding relays and wiring in the rails we discovered it was the fact on one side of the crossing only one rail was grounded, it wasn't the pick-up rollers at all. I'm guessing this engine has blind center drivers and if the plastic switch part is high it is lifting almost all the drivers off the rails. Really short tender too?

Thanks, John.  I forgot about 2Rail/3Rail on the later PS2 and PS3 locomotives.  The switch on the tender has always been in 3 Rail.  BUT - both sides of the truck wheels should be going to ground, only one side does this.  Switches are prewired by Ross, vary from O54 to O72, WYE O54,  and others.  Yes short tender  - only about 4-1/2" between trucks on tender.

That's not an uncommon situation, those two switches, that one and polarity, are frequently a source of problems.  Something about using a ten cent switch to handle track power... 

If you're never going to run in 2-Rail, which I suspect is likely, I'd consider pulling a wire from the switch and wiring both sides of the trucks to frame ground.

Another aspect of these insulated wheels on the pilot is that they will not throw a non-derailing switch.   Another reason as John suggests to ground both sides of the pilot wheels.

Bill

Thanks, a VERY important item.