Speed drop in a 10 piece track section on my layout - track or wire?

[kgill]

I run basic DC.

New Controller

Mix of new and old locos.

Same problem with all locos in same spot.

brass track, atlas #4 turnouts with snap switches.

I have one feeder wire for a 4x8 foot layout feeding the outer loop of a two loop layout, the outer loop is where the trouble is.

I realized that the engine speed drops slightly right after passing through a turnout placed just before the curve at the end (turn 1 if you are at Indianapolis 500) , travels at reduced speed for about 8-10 track sections, then after hitting the turnout on the other side (turn 2), it picks up again.

With no loco running, I placed a meter on the rails from the feeder wire and moved it along the rails towards problem turnout. Immediately after the crossing or the frog, i saw a 1.5 volt drop when i had my controller at 1/2 speed. All the way through the curve and up to turnout #2, same drop. After turnout #2 voltage back up.

I pinched brass joiners at turnout #1 to make sure they are tight. If i remember what I did correctly, this brought the voltage back up. Thought I had success.

Here is where I am confusing myself.

I ran the loco again and heard drop in engine speed still. I noticed that this happens at this spot - past the frog- when the loco passes. As it runs through turn 2 turnout, voltage and speed regain the 1.5 volts. does voltage normally drop in the track when the loco passes anyway because it is drawing energy? I dont think so but I dont know why it is happening.

Two problems one solution?

Replace the Atlas #4 with a non insulated turnout frog like Shinohara?

Did i miss observing something to locate the real problem?

Keith

[mfm37]

Add a set of feeders to the slow down section of track. A voltage drop of 1.5 volts with no load on the track should not be happening. With a load (engine) that drop should increase as your observation shows.

Martin Myers

[kgill]

Ok. Ill try that, easy test at least, and possible save of trip to hobby shop. Thanks.

Keith

[rrinker]

 Yes, just add more feeders. You still have a bad or loose rail joiner in there somewhere. Pinching it tight is only a temporary fix, as you runs trains it will work loose again, or another one will. You should probably have 4 sets of feeders around a 4x8, if the current set connect at the middle of the front straight, then you should have another set int eh middle of the back straight, and a set between truns 1 and 2, and a set between turns 3 and 4.

                --Randy

 

[MisterBeasley]

I agree that the problem is probably a lack of feeders, but since you said brass track, have you cleaned it lately?  Cleaning is a chore that we all must deal with, but brass track makes it more important to keep the railheads clean.  Nickel-silver track and brass track both oxidize just from contact with the air.  But, the oxide of the NS track is electrically conductive, while that of brass is not.

Install feeders.  Clean the track.  And, consider soldering the rail joints if that's practical.

[richhotrain]

One more vote for more feeder wires,

Rich

[Soo Line fan]

kgill

With no loco running, I placed a meter on the rails from the feeder wire and moved it along the rails towards problem turnout. Immediately after the crossing or the frog, i saw a 1.5 volt drop when i had my controller at 1/2 speed. All the way through the curve and up to turnout #2, same drop. After turnout #2 voltage back up.

Kieth,

To begin with, always test at full track voltage. Turn the controller all the way up and repeat.

When you use a DMM and check track voltage, without a load, it is an open circuit check. What you measured was open circuit voltage. This is an okay test but there are better ways. What you found was a loss of current caused by voltage drop.

Voltage drop is always caused by extra resistance. Loose or contaminated rail joiners, under sized wiring, suitcase connectors, cold solder joints, loose terminal screws are all potential sources of this resistance.

Switches, over time due to the way power is routed past the frog, can also cause a drop. You have confirmed that once the loco gets past #1 and until it gets past #2, you have a slow down. The DMM readings also show this.

kgill

I pinched brass joiners at turnout #1 to make sure they are tight. If i remember what I did correctly, this brought the voltage back up. Thought I had success.

You did have success - at raising open circuit or no load voltage.

kgill

Here is where I am confusing myself.

I ran the loco again and heard drop in engine speed still. I noticed that this happens at this spot - past the frog- when the loco passes. As it runs through turn 2 turnout, voltage and speed regain the 1.5 volts.

When the circuit saw a load by running a train, it lost current. This is why checking open circuit voltage across the rails is just an okay test.

kgill

does voltage normally drop in the track when the loco passes anyway because it is drawing energy? I dont think so but I dont know why it is happening.

Voltage will drop but only slightly, no where near what you are measuring . The DMM is confirming what your eyes are telling you.

I would leave the switches alone unless they are worn. To fix your issues, run at least 2 extra sets of feeders into this 10 foot area. This may or may not be the end of it. You may end up replacing or soldering some of the rail joiners but start with the extra feeders. Then head off future slowdowns by adding feeders to the rest of the layout.

As I said earlier, the test you are making is okay, you can repeat it after the feeders are attached.

A better method is to place a load on the track.

• For DC, use around a 1/2 amp light bulb. Attach leads and alligators to the bulb.
• Attach a alligator to each rail, turn the power all the way up.
• Use a DMM to read track voltage near the bulb.
• Move the bulb to the next section and repeat.