hello everyone just a bit of a general question here. My club was origonally wired by a guy using common rail. After some snafus with the performance of it, me and a friend re-wired the west loops of the layout to bi-wire and added rotary switches so the blocks could be controlled at the spot (or close to it). However at the meeting thursday night this sparked up a shouting debate. one side wants to use common rail (one wire runs the entire length of the layout and one rail is connected to it, and all the terminals on one side of all the packs are hooked up to that one wire, and the other wires go to the toggles for the blocks) and also wants to just have a centralised dispatch panel with a switch that when flipped will make all the loops into numbers, aka, turning throttle one makes loop 1 move and etc. in other words unless we have dispatch we're running an oversized lionel loop with no operations possible. this group says this is better because it saves us on wiring. The other side wants to use the good old fashioned bi-wire system (two wires go from the rotarys and one to each rail. with the 2 wires from each side of the pack going to the poles on the rotary. this group also wants dual control, with a DPDT switch you can select run or ops, in run the rotarys on the fasca control the blocks, in Ops, the rotarys on the fasca do nothing, but the rotarys on the dispatch panel work. For some reason common rail doesn't seem possible to most rules of electricity. wouldn't if you where trying to run 2 trains on 2 separate tracks in opposite directions there would be a short? It seems to work however it doesn't seem possible. I just wanted to hear peoples opinions on the forum to get some help as to what we should do. this is wiring for a DC layout. to get some idea on the track we're wiring, our website is Pikemasters - Colorado Springs Model Railroad Club thanks for any suggestions! Geep_fan
There are actually two separate issues - dispatched and/or local block control and common rail or 'bi-wire' (isolated) wiring. The first is down to your (club's) preference for operations. The second is to an extent preference BUT only if the controllers used are suitable for common rail wiring. They need to be fully isolated which in general means each controller will have its own transformer which is used only for that controller. If they are all-in-one units (mains lead in, variable DC out) check the manual. If they are units with external transformer(s) you'll have to work it out, but I'd recommend you go with isolated. (If minds are changed it's relatively easy to convert isolated into common-rail, but not vice-versa.)
Any DC power pack sold as a model train pack in the last few decades will be suitable for common rail wiring. (If there are exceptions, I'm sure people will chime in, but I've never heard of any.) Although I understand why common rail wiring sounds improbable, the simple fact is that it works, with properly isolated power supplies as Mike describes. Since in each track block the electricity can only flow back to one power pack, the voltage on that track matches the selected power supply. Any current that flows through the common rail cancels out and doesn't appear from the point of view of the locos. As for the dispatching issue, there are ways to setup any of the three possibilities you've mentioned (central dispatch, local control, loop control) with either common rail or bi-rail wiring. You can also use one method or the other for different control setups. In any case, it's advisable to gap both rails at block boundaries, and use a common bus to power the common rail, rather than the rail itself.
One other comment, on the dispatch issue itself: The way you described your DPDT switch on the local panels, it would override the central dispatch panel. That kind of defeats the point of central dispatch. Of course, when you want to do ops you could walk around to all the panels on the layout and flip them to ops, but it would make more sense from a practical as well as an operational point of view to have the central dispatch override the local panel than vice versa. (This is probably easier to do with common rail wiring, but anyway...) I'm sure I could offer more opinions on the dispatch issue, but after all, it's your club, and most other comments would require seeing a trackplan.
nope, DCC isn't a possiblity. too many members are still old school and prefer DC to DCC. plus the guy who laid the DCC side of the layout messed up big time. He laid the entire track setup for a 45x13 layout in less than a week. and he quickly wired it. as a result DCC operates poorly which has turned many members away from DCC. sorry, no trackplan, but the pictures do give a general idea. The idea was to put a DPDT at the dispatching panel. when its not an Op session, the switch is set so the local panels control the layout. flip it the other way and the corresponding Rotarys on the dispatch panel control the layout.
To me this will fall into the category of: It's your layout, whatever makes you happy. Something tells me this might divide the group; but, it's something the group needs to decided on. :tb-nerd: :tb-nerd: :tb-nerd: :tb-nerd:
Okay, that makes more sense. Note that you could also make the local control just another position on the rotary switch. Might make for a less cramped and more elegant panel. I would also note that setting the whole thing up with common rail wiring would involve buying less wire. To answer part of the original question, I guess I have a bias toward common rail wiring. (That is, as I said earlier, at the bus wire level. Actual rails should all be gapped.) Our wiring guru at the club wants to eventually convert our layout from common rail to actual two rail wiring, but I can never remember his justification for that idea.
well all the older more experienced members have already converted all the narrow gauge lines to DPDT for blocks and removed all the commons in the process. Since December at the last show we've been yanking the commons left and right and installing block control with bi-wire. the common rail works but we have ongoing shorts and the fuses attached to the tracks with common blow a whole lot easier then the ones on bi wire. Some operations on common rail we've tryed on our double track main line arn't possible on common, but possible with bi-rail. the only reason the club is even considering common rail is the cost and the guy who's installing it is like the money backbone of the club.
Bi-wire (also called "Direct-home" wiring) is a universal answer. For those that want to run DCC, replace one of the power packs with a DCC system, select all blocks to that input and DCC your happy self! Some of the DC guys might even be bitten by the bug! Modular groups do this all the time. Keeps everyone (almost) happy.
Some members like common rail because it take less wire. Thus the issue is (may be) how much will it cost to go bi-rail? Isn't wire purchase relatively inexpensive compared to other layout costs? It seems the bi-rail would allow more options in the future. You would still have the DC-cab control.
In ancient times :angel: we had at the FREMO DC control. We used no common wire with our module layouts. We had one thick cable for up to five throttles. Each throttle with its own power source. The yard panels had seven colored buttons for choosing the throttle. (Two yard throttles, you could not run to the next station with this throttle.) Wolfgang
Dustard is right! And prepare your layout gently, slowly for the DCC era... old meanning never last long:tb-wink:
I won't operate my locomotives on Common Wire or Common Rail layouts. I've seen some unusual smoke come out of my locomotives and I don't think I had a smoking unit installed. Analog DC and Common wire and or common rail has it's problems. As long as you are running trains all in the same direction it seems to work fine. Set a train to running in the opposite direction and you can watch the trains stutter, stall and shut down completely. I've talked to electricians, electrical engineers and they have all said the same thing... Common Wire, "This is not a good or reliable delivery of DC Analog current to the track". Explaining, the current from one transformer is searching for it's own home run. Causing the electrical motors to momentarily go into reverse thus what you and I see translated into stuttering, stalling, and in some cases shut down...due to a very basic short. Using the electrical toggle switches, DPDT (or double pole double throw) approach to controlling trains (Or as you so indicated Bi-wiring) is the best method to utilize and gives you the smoothest operational performance. You can accomplish this with rotary switches as well. This will also work for DCC delivery as well. Simply, install the bi-wires with 14 gauge wire and it will work splendidly when you switch over. Not a problem. Tie in DCC to one of your cabs and throw your toggles or turn the rotary switch to said cab and you are running trains. I hope this helps.
I've put in hundreds of hours on common rail layouts without any problems attributable to the wiring method. I'm not sure what mistakes people make (bad power supplies? not gapping rails properly?) but it is not an unreliable wiring method. If I may say so, if you are experiencing problems like the ones Rick describes, it's because there is a mistake somewhere. It's also worth throwing in here that you CAN run DC and DCC together with common rail wiring. You do need to optically isolate the Loconet (or equivalent) connections. Digitrax will give you optically isolated boosters, although I don't think it's documented anywhere, you have to call them up and ask. Not sure if other DCC manufacturers offer this.
Ben and of course all tuned in, Feel free to read on: According to several electrical engineers I've discussed this with many of our components for Stereo's, Autombiles and so on use a common wire. The catch here is at no time is the positive of one power source run over the negative...common wire...of another source. In my visits to a number of model railroad clubs, I discovered that most of them operate sections or blocks. These are set up where they only operate in one direction and then in the opposite direction without overlapping. The common or common wire for that local, section or block is never compromised by running a reverse positive over the negative common rail. Thus no problem. Try it the other way around where you are operating trains in opposite direction on the same common wire and you will see for yourself the problems this concept can curse you with. Most private home railroads are run by operating in the same direction. This works for a while but try to run one locomotive or train in the opposite direction and the fun starts. You will observe the locomotive stutter, hiccup, stall and eventually shut down. So, just in case we missed it the first time. The positives from each power source or transformer is looking for it's own home run or a pathway back to it's source. The action of the electricity on the motor will momentarily reverse the motor causing the afore mentioned / said action or behavior. It's not due to some mistake in wiring....I can asssure you. Another concern of mine is if you use any of today's modern, hi-tech, transformers with Momentum or Brake functions. The common wire and the subsequent short (positive on a negative pole) will cause you to loose the memory features, leaving you with a throttle pegged to max. I ought to know...been there done that. If you have your layout wired to common rail or wire then do this. Take one train and start it up headed east bound, it should start up and move along just fine. Now take another train and set it to running westbound...in the opposite direction. Did you notice the first train slow down? Is the second train having a hard time coming up to speed? Stuttering, hiccuping? Is the first train now showing the same symptoms? I guess you must have made a mistake wiring your layout...right? No not at all. This is a good example of how common wire or common rail works or is that doesn't work...very well?
To repeat, I've run hundreds of hours on common rail layouts with trains running in opposite directions and have never seen the problem you describe for myself. Our club layout, with about 60 mainline blocks and probably twice as many yard blocks, is a common rail layout. It has 9 DC cabs and a Digitrax Super Chief wired to the common return. (The Loconet connections on the DCC boosters are optically isolated as mentioned earlier.) I have put in hundreds of hours running trains on both analog and DCC while other club members ran trains in both analog and DCC in whatever direction they pleased. I also put in hundreds of hours on my own simple 2-cab common rail layout when I was a teenager, running trains in opposite directions without noticing any difference. If the common rail concept had as basic a flaw as you say, Rick, nobody would ever have suggested it anywhere, it would not have been included in all the books written model railroad wiring in the last few decades, Atlas would not have based its entire control component product line around the concept. But it is in those books, and that product line, because it works, if you do it right. No. Never. No. Never. No. That would be a sign of dirty track. No. Never. Why? Everything works fine.
If you hook the positive from one power supply to the negative of another, ISOLATED, power supply, you will not cause a short, and it is a perfectly acceptable electrical engineering practice in many cases.
