As your train approaches each block, you simply flip the switch associated with that block to the position that connects it to your transformer. If your train is the only one in a particular loop of track, you will eventually come to a block that you have already traveled and won't have to flip any more switches, since all the blocks in the entire loop will already be assigned to your transformer. But, if another operator also runs a train on that loop (or part of the loop), he will have had to move switches to connect some of the blocks to his transformer; so you will have to reclaim those blocks when you get to them.
If you want to park a locomotive or a train somewhere on the layout, you just drive it to that block, then move that block's switch to the center-off position. Then your cab is free to power another train in any other block, by flipping the switch associated with that block to connect it to your transformer.
You can see that this is a manual process; but it has been done automatically, as far back as the 1950s: When I was in college, I belonged to an HO model-railroad club (TMRC) that had such a system (called "the system") to connect blocks to cabs automatically, using a lot of cast-off telephone switching equipment--nothing electronic. It was extraordinarily complicated; and the members (including myself) were mostly far more interested in tinkering with the system, under the layout, than in running trains. During my tenure, we even designed a completely new system ("system 2"). I think they're now on system 3, which involves computers.
Bob Nelson
At the risk of look really out of it, how do you change the switches to operate the different blocks? I assume one loop of track might be made of 2 or more blocks. Does this have a way of happening automatically? I am having trouble with the TMCC, in that these sensitive pcs of electronics are too easy to damage and very expensive to repair now that Lionel doesn't make the original CAB-1 and base units and that means I will have to upgrade to Legacy for about $500. I am thinking of using my American Flyer 275 watt transformer and adding some standard Lionel transformers. It looks like I can sell the TMCC stuff I have and easily make the change.
Paul
Cab control is the concept of dividing the layout into "blocks" whose center rails are isolated from each other, and providing a switch or set of switches for each block that can connect that block to any one of several transformers, which are the "cabs".
This arrangement allows a train to be powered by a single transformer as it moves around the layout, by selecting that transformer for each block before the train enters it. This prevents the situation where two transformer outputs are momentarily connected together as a train passes from one block to another. This can produce a harmful fault current and destructive voltage spikes with traditional variable transformers.
The variations on this idea involve such things as having various types (toggle vs. rotary, eg) and arrangements of switches, and multiple switchboards at separated cab locations, with various ways of prioritizing the cabs to prevent two cabs from trying to power the same block.
I have tried to find the former information you referred to, but I don't have that issue. Could you take a minute and basically explain the concept of "CAB control"? I have an 8 X 12 layout with 3 loops and 7 sidings. I have planned to use 1 transformer for each loop and 1 transformer for the sidings. I have one transformer for accessory power. I have about 12 operating accessories, 10 uncouple tracks, 5 operating tracks and 17 switches. My track is GarGrave phantom, switches are Gargrave, 98% of rolling stock is postwar Lionel.
I am thinking your reference to "CAB control" allows more flexible use of power???
Thanks,
Paul, I see from your other thread that you are using TMCC. Maybe someone else here can help you; but I stay away from those products, because (except for the NMRA's DCC) the manufacturers keep their designs secret. I hesitate to give any advice about them, since I literally don't know what I'm talking about.
Please elaborate on the pit falls of one transformer for each loop of track. I have just built my layout and I am having issues. I have 3 transformers for 3 loops of track and 1 for accessories. I thought I was isolating the loops using insulated track sections between turnouts leading from loop 1 to loop 2, etc. I am finding that I am having some bleeding of power between loops.???
I haven't set up CABs with switches yet.
Let's call the switches for a particular block S1 and S2. Let's call the terminals of a particular SPDT switch -C (common), -NC (normally closed), and -NC (normally open). Let's call the terminals of a particular DPDT switch -1C, -1NC, -1NO, -2C, -2NC, -2NO. Then the connections for 4 cabs are
center rail---S1-C
S1-NC---S2-1C
S1-NO---S2-2C
S2-1NC---cab A
S2-1NO---cab B
S2-2NC---cab C
S2-2NO---cab D
One of several ways to do connections for 6 cabs, adding a third DPDT called S3, is
S2-1NC---S3-1C
S2-1NO---S3-2C
S2-2NC---cab A
S2-2NO---cab B
S3-1NC---cab C
S3-1NO---cab D
S3-2NC---cab E
S3-2NO---cab F
1. Good catch! If those are really separate transformers, as he seems to be saying ("...at least two transformers"), he indeed should have connected transformer B to the outside rail as you said. But whether that would be the U terminal depends on the transformer types. The postwar Lionel transformers generally used U for the common only if they were meant to control than one train. That may be the cause of the problems with the early CW-80s, which had two U terminals that were not common. However, the later CW-80s, which I hope yours are, do use U for the common, even though they control only one train apiece.
2. Closing the loop will reduce the worst-case voltage drop to the outside rails by a factor of 4. I would close the loop.
3. It seems reasonable that they would make all of them the same. Nevertheless, I would test them, since manufacturers sometimes do unreasonable things. But, even if the transformers are the same, it is possible to plug two of them into outlets that are not in phase, which would result in outputs that are not in phase. This would happen if you plugged them into the same duplex receptacle, wired into a 3-wire circuit.
Good luck with your layout!
I was also pleased to see Kent's article as I am just starting to wire my new layout and am going with cab control. I do have some questions that you may be able to answer.
1. In Kent's wiring schematic it shows the U post of Cab A attached to the outside rail but nothing for Cab B. Shouldn't a wire from Cab B's U post link up with the one from Cab A?
2. I will be running a 14 AWG bus for all my outside rail feeders. Should I connect the ends of that loop or leave it open?
3. I am a bit confused with the phasing of transformers as I am using two CW-80s for the Cabs and I thought with modern plugs with the large blade on one side they would always be in phase?
sorry for the laundry list of questions but I want to get this right and I am just getting started in the hobby. Thanks.
Jay L
Ottawa
My Layout is a Loop to Loop Plan, the mainline is divided into 4 blocks, with a Yard Lead and a 3 Track Yard. My 4 Locomotives are all Post War, Old School stuff. I use Atlas Selectors for block control. Here is my Control Panel, a plywood box on casters.
My Track Plan and Block Layout
I have always used 14GA. I wired up Spaulding's NP line many years ago with seemingly thousands of feet of the stuff. DPDT allows you to use the extra poles for lights to indicate block assignment.
I use up/down for block assignment specifically because we use side-to-side for "local/remote", meaning when "remote" the main cab runs the block, when "local" you can use a local cab for switching.
Dave
I just dug out that article, which describes the same, classic scheme. However, there are a few puzzles: One is that he used DPDT switches. As his wiring diagram shows, one pole is not used at all. The text however prescribes DPDT switches at every mention but never explains why.
Another thing that bothers me is that he prescribes "heavy gauge wire for runs of 12 feet or longer." He never mentions what "heavy gauge" is; and it's hard to tell what he has on his control panel. In any case, having runs shorter than 12 feet does not make undersized wire safe. He should be using 14 AWG with those 15-ampere ZWs.
It wouldn't surprise me if he has had to repair a few broken wires over the years since 1992. There is a better way to do the cabling to his hinged panel: He could have bundled all his wires into a single cable at, say, the left side and clamped it to the underside of the panel near the left end of the hinge. Then this cable would go horizontally along the hinge to another cable clamp at the right end, this time to the stationary framework under the panel. This arrangement, which is used for such things as telephone-switchboard desks, protects the wiring from flexing, since opening and closing the panel merely twists the cable through a modest angle.
Although it doesn't matter when a cab-control system is used as intended, it is a good idea to arrange the transformers to be in phase with each other. That way, when the inevitable mistake is made of running from one transformer's territory into another's, the fireworks are minimized.
I was pleased to see Kent Johnson's article on the last page of the May, 2012, CTT, telling how to wire and use a cab system on a layout. As many of you know, I have been urging this classic arrangement on the forum for a long time as an alternative to the all-too-common and risky transformer-per-block scheme.
Kent's article illustrates several important features of cab control that may not be immediately apparent. For one thing, he places the gaps on the trailing-point side of the turnouts, so that each turnout forms the end of a single block. This makes it simple to isolate his track 3 and track 4 from each other, compared to any other placement of the two gaps around the turnout.
He also mentions the left-right orientation of the toggle switches, which makes them much easier for the operators to use, by associating the toggle handles' positions with the locations of the transformers. It's a good idea to check your switches before installing them, because some connect the center terminal to the same side as the handle position and some work just the other way around.
Finally, the use of center-off switches makes it easy to park trains wherever needed, while leaving both cabs free to operate two trains elsewhere on the layout.
A feature that Kent didn't mention is the fact that the number of blocks is not limited at all by the number of cabs. At the cost only of one additional switch per block, you can subdivide the layout into as many blocks as you need or want.
I would like to mention some other more advanced options that may make cab control even more attractive to use. One is the possibility of more than two cabs. This can be done by using switches with more than two active positions. Rotary switches are attractive for this, but multiple toggle switches can also do the job. For example, an SPDT-CO and a DPDT per block can handle up to 4 cabs. And an SPDT-CO and 2 DPDTs can handle up to 6 cabs, an SPDT-CO and 2 3PDTs, up to 8 cabs.
One problem with going beyond two cabs is that you will likely switch the block to an unwanted cab as you turn the rotary switch past their positions or as you try to flip multiple toggle switches to their new positions. To avoid this, you need to switch the SPDT-CO to the center-off position before moving the other toggle switches. With the rotary switch, you would have to provide an auxiliary SPST switch to disable the rotary switch while turning it. However, having a single switchboard is not so practical when there are more than two cabs, since only about two operators are able to get close enough to use it. Another option is to give each operator his own switchboard. This could be an array of simple SPST switches; but that raises the likelihood that two operators will sooner or later try to power the same block at the same time.
To avoid this, make the operator's switches SPDT (center-off not needed). The most privileged operator uses his switches to connect each block to his own transformer or to a dedicated wire running to the next less privileged operator. His switchboard looks just the same, except that he connects the dedicated wire to his transformer or to a second dedicated wire to the third operator's switchboard, and so on. The low man on the totem pole can get by with SPST switches; but it's a good idea to go ahead and spring for SPDTs anyway, to allow for future expansion.
Notice that this arrangement allows the operators to be located at different places around the layout, not clustered together cheek-by-jowl (unless you like it that way).
Another wrinkle to the multiple-switchboard idea is to use DPDT switches instead, with the extra pole lighting a lamp on everyone's board to show that someone else is using the block.
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