catenary ho

why does locomotive run slow on catenary and faster on two rail system.


  • Hello David

    Welcome to our Forum.

    Are you operating an analog or digital layout? If it is digital, it is nice that it runs, in the first place.

    Are you using the same power supply for both, tracks and catenary?

    What brand and model is your locomotive?

    You see, there is no blanket answer to your question.

    One possibility is that the voltage drop through catenary system is greater than the drop caused by the rails. But this is only one out of many possibilities.

    You see, we need more info.Choo Choo2015-02-18 23:46:51

  • I am using same locomotive and power supply for catenary and two rail system. I want to know if this is a common problem with catenary and can the problem be solved?
  • It is not a common problem.

    Is your layout digital or analog?

    What is the make and model of the locomotive?

    What is the make and model of the power supply?
  • Hello:

    Welcome to the forum.  What type of catenary are you using?  I assue that you use standard DC-track.  The reason for the different bahaviour is the way track and overhead catenary conduct electricity.  While railjoiners usually conduct electricity decently well (untill they get loose), the catenary pieces rely on the way they touch one another.  The latter should result is a higher resistance, and thus a higher voltage drop.

    One way to solve this is by soldering the catenary pieces together and, have several spots where power is fed into the catenary system.  Also, you might try to run your locos with both panthographs up.  This may take care of some of the problems since the current flow down a panto may encounter more resistance than the current from the track.

    Finally, if you decide to go DCC, then the whole issue goes away.


  • what if I use a separate transformer for the catenary and another one for the single rail, would this increase power to the catenary system?

  • how does the problem go away if I use dcc?

    David, I do not see how the problem will go away with DCC but let Ulrich explain why this will be not a problem anymore with DCC, I do not see it right now.

    The general problem is not the power supply, it is the way the power is delivered to the locomotive. As Ulrich already stated right, the tracks feature a much better connection to each other.

    Whenever you have a power source and using a cable to connect it to a load (like your locomotive) the cable (and the rail) adding resistance what reduces the Voltage (Voltage drop). The more resistance (long, thin cable, long track layout) you have the less voltage gets to your locomotive and this slows it down. The connection of the catenary's to each other without that they soldered together adding even more residence and your locomotive gets less voltage.

    Small Example:
    Your Transformer puts out 12V
    Your Locomotive runs perfect with 12V
    The Voltage you get on your tracks are not 12V, it might be only 10,5 Volts (you will not notice this because you have no reference)
    The Voltage you get on the Catenary might be only 8 Volts what would be over 30% less and this slows it down (you notice this because you have a reference how it runs on rail feeding).

    How to fix it (it is possible):
    A recommended practice is to feed power to the tracks (or catenary) on multiple locations (usually all 6 - 9 feet of track). The way the catenary is connected together is here the problem in my opinion. Without knowing what system you are using (Maerklin, Trix, Viessmann, Sommerfeldt, etc.) it is hard to give you further advice. More information and pictures would come in handy.

    I hope it gives you a better idea what causes your problem.

    RRVRR2015-02-19 15:12:57
  • If you switch to DCC, the problem goes away because the pantographs of electric locomotives with a factory installed decoder are not wired to pick up power, because of the inherent problems.In a digital environment good conductivity is more critical because of the complexity of the digital signal. This signal does not only provide the electrical power, it also carries a binary signal like computers use. In this case a catenary system is merely for show.
    Well, my question was how the problem should go away when using catenary power pick up with DCC (or MFX) instead of DC (or AC - we don't know yet)????

    Just saying that on a regular basis this is not supplied by manufacturer (for the stated reason) means not that it can't be done. If somebody would like to use the catenary the problem will persist and you are right it will get worst. Nobody that I know would like to do it but again, this was not the question for my understanding. Wink

    RRVRR2015-02-19 15:37:22

  • Okay, I think there is a basic misunderstanding here.
    In the past, modelers used live catenary power as a means to be able to operate two trains independently on the same section of track.  I planned to do that on my previous layout.  The plan was to have an electric switcher working off catenary.  That would have allowed the switcher to enter track sections on which other trains were stopped.  I tested this on a small section (with some ugly non-ptrotypical catenary), but never got much further prior to a move -- and the dismantlight of the layout..
    With DCC, there is no reason to run anything off live catenary.  All power is fed through the tracks, and you can operate any number of locomotives independently on the same section of track.
    The reason the problem of bad power feed with live catenary will go away with DCC is that you no longer have any power feed through the catenary.  There simply is no reason to have live catenary, as there are all sorts of problems with reliable power feed through catenary -- which are not encountered with power feed through the tracks.
    Hope that makes sense.
    -- Ernest
  • Dear Aaron:

    When operating a DCC layout, all power is fed over the rails (and the studs if you use Marklin).  Feeding the power over the overhead catenary makes no sense in this case out of several reasons:

    a) Since the power pick-up through the wheels and rails is more reliable than through the catenary and panthographs, there is no need to feed power through the overhead catenary when using a DCC system.  The electric locos will pick up power from the rails just like your steamers and diesels.  The capacity of DCC systems is large enough to handle all this traffic.  Moreover, overhead catenary power adds an unnecessary complication when running your electrics through a return loop, unless you have Marklin track.

    b)  In an analogue system, the overhead catenary and one of the rails form a second electric circuit with a common return (one rail in DC, both rails with Maerklin).  If you carry this idea over to the DCC world, and try to boost capacity by running two command stations (one overr the rails and one over the catenary), then you are asking for serious trouble since you would operate two command stations with a common return, something all DCC manufacturers warn against.  Even with boosters, it is not recommended to have a common return because of possible interferences.  Most DCC manufacturers strongly advise against any such common rail wiring too, and recommend that power district are separated in both tracks.

    Ulrich, Ernest,
    you are both right but you might went to far on this Wink
    I understood it as a general question to do it like the prototype. I did it when I was young on an old Maerklin Layout where I had catenary's installed. It was fun to see the sparks on the catenary when you switch of the lights.

    As off today it indeed makes no sense to use the catenary at all and I would never recommend it. The reason Ernest stated to control two trains on one track in analog would be a way to do it but on my old Maerklin it only worked well at full speed. Driving the locomotive at slow speed is a pain.

    RRVRR2015-02-20 08:29:51
  • Markus:

    If you use the old Marklin catenary, it oxidizes, and the resulting product is a lousy conductor.  When I ran analogue, I ran all my engines with both pantos up if they picked up power through the catenary.  Even then, it was not a completely satisfactory experience.

Sign In or Register to comment.