Losing some power in a block of track

JDA,

   If you have a Lionel or K-Line voltage car, simply pull it down the tracks behind a few cars with your engine, and watch the volt meter, it should show you right where your voltage drops.  Replace that track and one on each side, and retest.

PCRR/Dave

The voltage may be there but not the amperage needed. Check for loose connections or track pins..

romiller

check the block with your meter along with the train in the block. Voltage drop does not show up without a load.

Did you insulate all 3 rails? Now only have a hot and no common in the block?

Only insulated hot.

 B

Have you supplied additional power wires to both rails, both the center and outside rails? If the track is after a switch, the switch may not give you a good common for the outside rails and will need a common supplied to the outside rails.

If the track is old or has been assembled a few times the track pins or track joining area may be loose as well. Use a pair of needle nose pliers to jently squeeze the track closed a little at the connection areas for the track pins. Look at the underside of your problem tracks, if it is old it may have rusted from the bottom side and won't show up on the surface.

Lee F.

Tried also connecting outside rails, added load to that section of track.  Voltage is the same everywhere, none of those things changed anything but my locomotive still slows down when in that block.  I am at a loss as to what to try next.

What size wiring are you using to feed the block that is losing power? If the wires are too thin, you'll get the voltage reading with a meter, but you might not get enough current for your train.

18 gauge.

My take, I would put on power, place a lighted caboose on track to be tested and then run my hand over the track being tested. When you feel the hot spot you have found your problem. if THIS DON'T WORK then you have to look for a piece of metal touching the center rail to the outside rail.  Also look at the bottom of the loco for a piece of metal, loose screw or loose pickup plate.

To me this is what makes running trains fun, problem solving, I once tore up 100 feet of track looking for something like this , and found it was a screw touching the rails.

Rod

Are the blocks on two different transformers?

.....

Dennis

JDA: I'm going to start from scratch and run through this problem with you.  First, 18gauge wire is really too thin for O-gauge trains, and in any but the shortest lengths will result in substantial voltage drop.

I assume the voltmeters of which you speak are on a transformer.  As such they only read the voltage which is being output from the transformer; they do not read the voltage which is at the locomotives's location.  Voltage drop is a product of amperage times the resistance, so if there is no amperage flowing, you will not have any voltage drop.  Voltage is lost only when there is a load on the circuit, and the amount of voltage drop is proportionate to the load (the amperage).  Applying a voltmeter, or a load as small as a single light bulb, really is not enough of a load to adequately test a circuit.  I cannot picture the load from a single light bulb causing rail joints to heat up noticeably. 

I do suggest that you buy a CHEAP voltmeter; one from Harbor Freight at four or five dollars is adequate for this purpose.

Since you apparently do not have a voltmeter, let me suggest this: get a pair of alligator clips, which are available at RadioShack, and the length of no-thinner-than-16-gauge wire.  Make yourself up a jumper cable long enough to reach from your transformer to the far ends of the layout.  Connect one end to the hot terminal at the transformer and when the locomotive is in the area running in the area where it slows down, touch the other end of this jumper cable to the center rail near the loco. If the loco speeds up, you have found what the cause of the problem is.  You can then touch this clip to various locations between the lockon and the locomotive to try to pin down precisely where you are losing the voltage.  Please be aware that the voltage drop may well be equally distributed along the entire run from transformer to loco.  if you suspect that it is that the problem is that a rail joint simply take your jumper wire and go across each joint while the logo is running in the affected area.

You haven't specifically mentioned whether or not you have multiple feeds to the outside rail, but do be aware that you really should have as many feeds to the outside rail as you have feeds to the center rail.  You can have voltage loss in the outer rail circuit also.  To test this, you'd put one end of your jumper terminal on the ground (usually "U") terminal of the transformer and touch the outside rail where the loco is running.  Have you tried "additional power jumpers" on the ground (outside rail) circuit?

Attempting to measure amperage will not get you anything in trying to solve this problem.  The name of the game in this testing is to try to increase the load as much as possible – – increasing the amperage – – to maximize the voltage drop and make it easier to locate where it is taking place.   FYI:   Amperage in a circuit is the same everywhere in that circuit.

Is the block that slows down the one with the on/off switch or the always on block?  If it is the one with the switch, try bypassing the on/off switch to see if the problem goes away.

.....

Dennis

JDA:  If you can figure some way to put a constant electrical load at the end of the block, like a bnund of lighted passenger cars, you can use your AC voltmeter to detect poor rail connections by placing one prod on each side of the joint.  Any voltage reading will indicate a bad connection.  You may have to set the voltmeter to a low AC reading.

You can connect the prods to the transformer and copmp[are the reading with that taken at the end of the block, under loco load.  Or you can connect one prod to the transformer and the other to the track, when there is an electrical load at the end of the block.  Move the track prod along and look for a voltage change.

  Try taking out the insulating pins and replacing them with steel pins, making the layout one 'block'. See if your trains still slow down at the same spot on the layout. If they do, either you are losing voltage somewhere, or there is a possibility of a slight grade on your layout. A slight grade, even one almost imperceptible, will cause your trains to slow down without affecting the voltage.

Larry

I second the lighted caboose; its easier to deal with than a moving engine.

The problem with using a lighted caboose is that the current drain is minimal, so that the voltage loss at any point is minimal & therefore harder to detect.  The ideal is to use heavy duty resistors and make up a device that, when clipped to the track, will pull the maximum amperage your system can provide.  Then the effect of any poor connections will be magnified and more easily detectable with the voltmeter.

Voltage loss is often referred to as "IR drop," I being the amperage and R the resistance being encountered (i.e., the poor connection(s)).  The more amperage, the greater the voltage drop, which shows up better on a voltmeter.

Larry is right about the effect of a grade.  I forgot that since I run DCS, which compensates for grades.

Thanks to everyone for all of the suggesitons.  I have tried all of them (I think) and get the same result.  The only thing I have not tried is to replace the track.  I may try that some time but for now, I think I will  just live with the problem. 

Put a level on your layout to see if you have a slight grade. If not, then you have an electrical issue. If you have a simple loop, try turning the entire loop 180 degrees. See if the problem stays in the same physical location, or has followed the track to the other side of the layout. If the problem has followed the track, then take apart each section of track, clean it and the connecting pins thoroughly of all dirt, oil and/or rust. Reassemble the track, making sure all the pins are tight, crimping the track ends if necessary. Make sure all lockons are clean and tight fitting, and all wire is of sufficient gauge to prevent voltage drops.

Larry

JDA, since you do have a voltmeter, try this.  Connect voltmeter to track near the end of the problem block.  Have no trains or anything on the block.  Apply power.  The voltage applied and at the end of the block should be equal.  Then run a train starting from the other end of the block and observe the readings on the voltmeter connected to the track.  If you problem is electrical, it will show up.  If voltage drops markedly as loco enters the block, wiring between transformer & track is the culprit.  If voltage drops as loco approaches voltmeter, problem is in track.  I do think 18-gauge wire is partly to blame.

A couple of thoughts:

I don't think you said what kind of engine you are running?

If its a PW AC style motor, it will draw way more power than newer engines, and this will accentuate any voltage drop to the track.

If you set your track voltage to about 12-14 volts, you can use a surplus automotive headlight as a dummy load by wiring it up with a couple of alligator clips. It will draw about 5 amps and this will quickly find any voltage loss.

Simply clip it between the center and outside rails and measure the voltage there, before and after.

My guess is that with 18 ga wire you may find a 2-3 volt loss, and this will definitely cause an engine slow down.

One thing you could do is add DCS and run only PS-2 and cruise control equipped TMCC engines. This will eliminate or greatly minimize any slow down due to voltage sag.

Rod

JDA;

I would use 14 ga if you are running conventional, especially if the wire is longer than say 20 feet.

You could also run another jumper feed to the track at the end of the block, which willl mitigate the track losses.

Rod

 The 14 gauge wire would be the best choice. The heavier the wire, the less voltage loss in the wire, especially over long stretches.

 Check your track first. Add multiple feeder wires to each block anyway; it does not hurt to distribute power with wires instead of relying only on the track.

Larry

JDA:  You're welcome.  I am a devotee of using 14-gauge wire for all track feeds.

Do note that your voltage drop can be on either or both hot and ground feeds.  You didn't mention what type of track you use, but steel pins can corrode.  The old Lionel tubular track suffered from both this and spreading of the rail around the pins.

There will always be some voltage drop when the train enters the block.  That's just the nature of low voltage operation.  Name of the game is to hold it to a minimum.