Discussion in 'HO Scale Model Trains' started by mentor63, Jan 31, 2008.

  1. mentor63

    mentor63 Member

    Turntable and Loco Service Facility

    Hi Model Railroad Fans,

    I am new to the Forum, but learned several things that had been bothering me my first log in as a guest. So I joined and now I have a question.

    I am building an HO layout which includes a Walthers 130' turntable. I am rapidly approaching the point where I can no longer put it off, but I have been dreading actually installing it and the associated 6 stall round house as I am guessing it is not very forgiving of inaccuracies or errors. Also the electrical wiring is not entirely clear to me as I have never done a reverse loop and understand that is required for the turntable.

    So, any tips before I dive into this project?


  2. Nomad

    Nomad Active Member

    I can't help you with the tt, but I am sure somebody will be along shortly to answer your questions.
    Just wanted to say Welcome to The Gauge, Mentor:welcome1:.

  3. Santa Fe Jack

    Santa Fe Jack Member

    I am poised to install the 90-ft version of the same turntable. I do not think that a reversing loop is necessary, actually. The power to the bridge is supplied by the turntable control box (I assume that this is the same for the 90-ft and 130-ft versions). For the power to the tracks (I will have 11 of them, including 3 to a roundhouse) I was going to install a master switch that would supply power to any one of the tracks, that power being matched to the power to the bridge. This required that I find a 2-pole 12-position switch, which I did at the local nuke lab surplus store (this is Los Alamos, after all).

    I am also anticipating that the trackwork will be tedious and unforgiving. Let's keep in touch on this, and learn from each other.
  4. Trainiac77

    Trainiac77 Member

    Hi Mentor63 and welcome to the group. I've done a bunch of turntables and I always add a reverse/forward switch to the table track. Simply put if the table is turned around, the lead track or the storage track polarity might be reversed. Forgive me if this is too simplistic but this is the way I wire the switch.

    Also I make the lead track and the storage tracks all the same polarity with on/off switches on each. I've also added LED's on the tracks to show polarity, but that's a whole'nother subject. Hope it helps. - Trainiac77

    Attached Files:

  5. mentor63

    mentor63 Member

    Thanks for the inputs so far. Right now I am working on exactly where the turntable will be placed, as that seems to drive everything around it (the roundhouse, associated outside repair facilities, the yard tracks and turnouts nearby, etc.) and, of course, there is never enough room. Working on determining the "long poles in the tent" right now so I can shoehorn everything in and adjust the less critical items as needed. I will keep in touch, Santa Fe Jack, as you suggest. Good Luck!

    Keep flying with the eagles!

  6. steamhead

    steamhead Active Member

    Welcome to the Gauge, Mentor...I'm sure you'll find in it a wealth of info and good people to give you a hand....

    Speaking of which...Trainiac...Could you please post the diagram you mentioned for wiring LEDS to indicate track polarity...?? I'm used to DC but now that I'm into DCC the intricacies of this escapes me...
  7. Santa Fe Jack

    Santa Fe Jack Member

    I intend to add LEDs to show which of the tracks has power, provided through the 2P12T switch.

    I still do not see the need for the reversing loop, as the table (bridge) track, the storage tracks, and the leads to the turntable will all be wired to a single block, and run from one controller. If I want to reverse polarity, I just do that with the controller. I think this should work.

    Maybe it's different because I am using DC block wiring on my layout...
  8. MasonJar

    MasonJar It's not rocket surgery

    Some turntables are wired internally to "automatically" reverse as they are turned. This is sometimes called "split ring". Turntables that are wired through something like a headphone jack need a reversing circuit because the wiring does not "change" automatically as the TT is spun around.

    A common example of the split ring TT is the basic Atlas one.

  9. Trainiac77

    Trainiac77 Member

    Here is the simplest one I use. I use them very sparingly as they do draw off the track power. For me though this isn't a problem because I use the old Hogger tethered throttles which are 10 amps @ the track. Mostly one on the led in track and on the turntable bridge hidden between the rails.

    Of Course you could do this with a single LED as well, if the polarity is forward it's on, if its reversed it's off or vice-versa.

    Hope this helps.....Trainiac

    Attached Files:

    • LED.JPG
      File size:
      10.1 KB
  10. mentor63

    mentor63 Member

    Santa Fe Jack,

    I am doing DCC, so that could it, or I could be remembering the need for a auto reverse completely wrong.

    Right now I am concerned about the geometry of getting the six (6) tracks going into the roundhouse lined up with the center of the turntable. The distance from the roundhouse to the center of the turntable seems to be the key issue and the plans specify the distance (12"?) so how hard could it be, right? Ha! We will see....

    Keep flying with the eagles!

  11. Santa Fe Jack

    Santa Fe Jack Member

    My 90-ft turntable came with a full-sized template for laying out the tracks. Did yours? I will be running 3 tracks into a roundhouse, and have these and 8 others at 10-degree angles around the turntable. For the 90-ft version, the tracks are nearly touching each other at the lip of the turntable. For the 130-ft version, they should be comfortable further apart, but the distance from the turntable edge to the roundhouse will be that much closer.
  12. mentor63

    mentor63 Member

    Yes, my 130' came with the template for cutting the hole, etc., but not much about how to place the roundhouse. However, if the turntable is 10" in radius and the roundhouse has to be 12" from the center of the turntable, there must be about 2" between the edge of the turntable and the roundhouse. I think I will just need to get the overall placement close, then install the turntable. Once that is done I can tweak the roundhouse placement a bit as needed.

    Keep flying with the eagles!

  13. steamhead

    steamhead Active Member

    Thanks for the diagram Trainiac....@ questions...1.- Will this work with DCC, and 2.- What is the value of the resistor..?
    (Sorry M63..Don't mean to highjack your thread...). :cry:
  14. Floyd

    Floyd Member

    I have been reading the above information on the turntable subject and am glad that it was brought up.:thumb: I purchased a TT at an estate sale for a price that was too good to pass up but as of yet I have not ventured to install it. I have ordered a roundhouse....may have to add some room to the existing layout.:confused: I find any information on the subject helpful so will keep my eyes peeled to see new posts as they are added.
  15. 60103

    60103 Pooh Bah

    I don't think trainiac's circuit will work with DCC; becuause it's a form of AC, both LEDs will glow a bit.
    If the Walthers TT is one that requires a reversing switch, the best method is to makes sure one end has a distinguishing mark (a cabin or a special paint job) and set it so the reversing toggle points at that end.
    In DCC, a reversing black box will do the job and it's not a large investment after the other bits.
  16. Trainiac77

    Trainiac77 Member

    I really don't know if this will work for DCC, I only have used it on DC. The polarity on DCC is determined in the locomotive module not on the track.

    The value of the resistor is determined by the voltage divided by amperage (ohm's law)

    Hope this helps.

    Attached Files:

  17. mentor63

    mentor63 Member

    I have been going back and forth between my CAD playout plan and the actual layout to get the geometry "on paper" to transfer to the actual layout. Seems there is always some inaccuracies. It is an older CAD program and some of the turnout templates are not the correct size for the new turnouts I am using. :-x But I just moved/installed two of the surrounding track sections to try to get the tracks leading to the TT as straight as possible. I am trying to stick to a minimum 24" radius, but have had to compromise a bit in a few places. I have a cutout I made in foam for a long section of 24" radius and I use the little 4"-5" long metal track guages. Since I plan to run a UP Big Boy, I try to test the track where ever I think it might be a problem. So far so good. :mrgreen: I am slowly sneaking up on actually installing the TT.

    Keep flying with the eagles!

  18. mentor63

    mentor63 Member

    I just re-read the instructions (about time!) that came with the Walthers 130' turntable I will be installing. It says the electrical power to the turntable track is automatically reversed so I guess I will not need a separate auto reverse. It just requires a separate power source for the motor and indexing system that rotates the turntable. The actual installation looks fairly straight forward, but time will tell.

    It also says that all lead-ins to the TT must be straight. Clearly, that would be best, but I thought I had seen curved track leading into a TT. Does anyone know anything about that?

  19. Well, the idea is that nothing will hit the sides of the actual table while the loco is entering. If you place a short section of straight track to allow the loco to realign with the track, you can have a curved approach. With a Big Boy, I wouldn't recommend bringing the curve right up to the turntable. I have one too; the overhang would destroy the table lol...
  20. mentor63

    mentor63 Member


    That's what I thought. I am planning a 20" straight-in lead through the steam era coaling, sand, water, but want to be able to bring in, and exit, shorter steam and diesel locos from two other leads and that would result in some curves ending near the TT. I think if I plan at least some straight track just before the TT it should work.

    Due to layout size limits near the TT, I was concerned also about the track near the TT and roundhouse being too tight for the big engines. I tried both my Big Boy and DD40 last night and they worked fine. More overhang than I would like, but I think it is a compromise I can live with. So now I have bracketed the surrounding area and am about ready to plunge into the TT install. Thanks


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