TMCC loco quits over switch

[rick486]

Hate to be such a pest for information but have just assembled about 150 feet of track in my living room (see "Power for multi loop, multi train layout" to see my Christmas layout.

Anyway. I bought 5 remote switches and am using 2 manual switches for the layout. Because of the size of the loops of track, I have 18ga wire (power) running to the middle and far ends of the loops. I also bought and installed the Lionel Block TMCC controller and have hooked it up to the two loops plus two sidings. Amazingly, when all the programing was done, it worked like advertised---all the blocks (4) came online when ordered by the CAB-1.

The problem is on the one loop in which I'm running two trains---a diesel and Lionel's new Lionmaster Big Boy UP loco, they seem to run OK except when the Big Boy runs over one of the remote switches at the far end and it stalls. The O Standard desiel (Pennsy) does not. I've disconnected the other loop....run power shunts from one side of the switch to the other and have 18ga power wires out to this extremity....all to no avail...the Big Boy stalls over this switch.....

The Big Boy runs fine over the second loop with many switches.

Could I somehow have switched the center rail-outside rail in one of my runs to the hinterland of this loop....?????

HELP.....I'll have to sidline this great loco for Christmas if I can't fix it.

One other thing, I'm only getting 12-13 volts on the track power side of the 80w transformers....I thought I was supposed to get 15-18 volts???? Maybe I need the Powermaster 180w for each loop?

thx
Rich

[pmilazzo]

Sounds like you are losing power going to the big boy. Two things you should check. Get an ohm meter and check that both sets of rollers on the bottom of the big boy are at 0 ohms by placing each probe on one set of the rollers. There should be no resistance. Infinite resistance means that only one is working for you and that would explain the stall. You could do the same test with the meter set to "diode mode" which tells you if you have continuity sometimes with a tone.

If this is the problem, try cleaning all the rollers and try again. If the problem persists, you probably have a loose wire going to one set of rollers on the engine.

If the roller test passes (0 ohms, or a tone in diode test mode), it's time to look at the track.

When the engine stalls out on the switch, carefully remove the engine and place it on it's side next to the stall. You want to be as careful as possible not to introduce additional human error. Note where the rollers are on the track. You can do this by just getting one roller positions and measure where the other one would be or just comparing with the engine on it's side next to the track. Again get your meter and check the center track like we did the rollers. Touch each probe on the track where the rollers would be. You should again get 0 ohms or a tone in diode mode assuming that the center rails are connected through the switch. If not, clean the track and try again. If the problem persists, try tightening nearby track connections with a long nose pliers and or add another drop near the problem.

Lastly, it may a perfect storm scenario where the roller spacing on the big boy happens to be just the exact distance where intentionally there no power is on the track. This sometimes happens with some engines when there are back to back turnouts. When it does happen, it's just bad luck. Some engines will go though with no problems and others will hit the dead spot.

There are three solutions for this. One is to change the roller spacing on your engine. Sometimes by installing one or more roller assemblies backwards, that will change the roller distance (closer or farther) and you will miss the dead spot on the track. Usually, a screw driver is all you need and you are back in business.

Second solution is to connect the rollers on the tender to the rollers on the engine giving you more center rail contacts and longer reach to the the center rail power. The down side is you will have to add an addition wire from the tender to the engine.

Third solution is to change the track geometry if you can so that the rollers will not find this dead spot. Sometimes between back to back switches, you can add a 1 3/8" track and that may just be enough to give the rollers the distance they need in the big boy to get power again.

[rick486]

Thanks,

I'm gonna look into all your suggestions and check the engine with an ohm meter, but here's what I discovered in the mean time:

The "faulty" switch is an 0-48 radius remote...I noticed that when the Big Boy engine rolls slowly over the switch, there is a momentary electric arc (short) and the TMCC stops. The short seems to be coming from this overly long, all metal tang which I've now covered with electrical tape:

http://forum.ogauge.org/picture.php?albumid=10&pictureid=105

If you'll notice, all the other switches, both manual and remote, have a more rounded tang with a gray plastic nose:

http://forum.ogauge.org/picture.php?albumid=10&pictureid=106

I'm going to check the engine as you suggested and attempt to see which pick-up is shorting the rails.

Rich

[pmilazzo]

So are you saying with the black tape on the turnout, you loco makes it through the turnout with no issues?

In order for that tape to work, some part of the engine which is grounded like the wheels or chassis is coming into contact with the center rail.

[rick486]

I think you're right about the wheels shorting the center tang of the switch, it seems to be the front truck of the tender, but I'll have to check further.