# block control



## Blk69 (Dec 6, 2009)

Wanting to run two engines on a single mainline loop. On my O scale layout, this was fairly simple to wire track with block control. Basically I had a contact that was activated (by weight of Engine) that would kill a section of track behind the cut out (catching a engine if it were to close to the one activating the contact).

Things slightly different outdoors (track will be ballasted down). Would you all suggest a photo eye tied to a relay as the best way to achieve this control outdoors. Anyone have any guide lines on how long to make the isolation blocks?


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## toddalin (Jan 4, 2008)

You can activate a relay just by using a pair of insulators laid end to end with a small section of rail between and let the wheels bridge the gap to trigger the relay. Alternatively, you can do this with a reed switch and a magnet on the engine. The relay can be set to "self latch" until the other train "unlatches" it.


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## astrayelmgod (Jan 2, 2008)

I don't know where you are, or what others are doing in your area, but around here (Southern California), battery control is sweeping through like some sort of virus. I had elaborate plans for all sorts of automatic multiple train control, but now I probably won't bother, even though I personally don't have anything that is battery powered.


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## wgn4884 (May 23, 2013)

Blk69, I'm doing something like you want to do on my indoor layout. On a loop about 160 feet long I put in 3 insulated rail joiners dividing the loop into three sections of near equal length. The common rail is continuous with no insulated joints. Each of the 3 blocks has a feeder to the other rail. One block (normal block) has full power all the time. The power feeder to the next block (detection block) goes through a Dallee train detector. When a train is in the detection block, a relay on the detector board activates and cuts power to the third block (slowing block). It would be simple to cut power completely to the slowing block, but I wired it with a big diode. When the train detector relay activates, the Normally Closed relay contacts open and break the flow of current from bypassing the diode. Thus when a train is in the detection block, voltage to the slowing block is reduced by about 0.7 volts and the train slows a little but does not stop. It took some trial and error to get it to work, and the two trains must be fairly close in speed. The effectiveness of the slowing block is enhanced by it including about 35 feet up a 2% grade. This only works in one direction, but a single train can run in either direction. 

I hope you can get it worked out. 

Bill in Georgia


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## wgn4884 (May 23, 2013)

Blk69, to clarify my previous post, trains go from the detection block to the normal block then to the slowing block. 

Bill in Georgia


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## Blk69 (Dec 6, 2009)

I like the idea of a small section of track as the activator. How long of a piece of track did you use for activation?


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## Blk69 (Dec 6, 2009)

great tip about the diode. Slowing the second train would be superior to stopping it. thank you.


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## wgn4884 (May 23, 2013)

Hi, Blk69. I measured the track sections and came up with the detection block is 46’ 8”, the normal block is 64’ 1”, and the slowing block is 49’ 6”. So the total loop is 160’ 3”. I think what may be relevant is that the detection block is 29%, the normal block is 40%, and the slowing block is 31% of the loop length. 

When a train enters my slowing block, it is about 3/4 the way through an 8’ diameter curve and transitioning to a 2% up grade. This makes the slowing barely perceptible to anyone but me, since I know it is happening. The train is going up hill for about 35’ and most of the slowing happens in this first part of the block. All of the detection block is level track, but with an 225 degree 8’ diameter curve and a second curve of the same diameter of 45 degrees. The normal block includes all of the down grade track. 

The Dallee detector has a DPDT relay and has a delay about a second. This is good because it keeps the relay from chattering. The current flowing through a lighted caboose is enough to keep the relay engaged, so if you are running lighted cars, the effective length of the detection block is the length of insulated rail plus the train length. One train I’m running now is about 10’ long with lighted caboose, so the detection block is 56’ 8” when this train is in it. The other train I’m running has a Mogul and tender, so it adds about 18” to the block length. 


A bad thing about my blocks is that one train enters the detection block before the other enters the slowing block. The caboose wiring puts full voltage to the slowing block for an instant when the front wheels are in the slowing block buy the rear ones are still in the normal block. This hasn’t caused a problem, but it could with a long string of lighted coaches. It could burn out the wiring in the last coach. It would be better if the first train were completely in the slowing block before the other enters the detection block. 

If one diode doesn’t give enough speed change, more diodes in series could be used but with more jerk load on the gearboxes. 

Hope this helps. 

Bill in Georgia


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