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Auto Throw, Trigger Rails and the Block Watcher

Posted by on Feb 26, 2015 in Tips DCC Components, Tony's Tips |

Block Watcher

DCC Guru Larry Maier discusses the Hare, Auto Throw, Trigger Rails and Block Detection using a Block Watcher

I have some questions about HARE and Auto Throw. I am trying to set up my HARE V1 rev J, in the following manner.  First, I want to have Auto Throw set to prevent a train from entering the turnout when the turnout is set in the opposite direction.  This should be accomplished by normal installation, as shown in the instructions. Successful completion of this effort is very important since the turnout is buried in a tunnel with limited access.  Have I got this straight, will it work, or have I missed something?

If you want to actually stop the train, then the trigger rail must be longer than the longest engine. In your case, the entire consist at the front counts. Since the train is arriving against the points, there is no power to the trigger rail, so the “engine” will stop once all power pick up is within the trigger rail. Remember the auto throw timer only locks out auto throw AFTER an auto throw has occurred. If the first train is moving through the switch by a means other than auto throw, then the second train will throw the switch under the first.

Second, to prevent a second train from entering a turnout or throwing a turnout when the first train is traversing the turnout, I want to set the Auto Throw Timer (CV67) to allow the first train (usually 12-15 cars) to clear the turnout.  Trigger rails will be set about 24 inches from the turnout.  If the trigger rails are less than 4 inches in length, will the Timer stop a double-headed diesel locomotive until the time has expired?  Or will the second engine push the train through the trigger section, wherein the first locomotive would be reactivated via “hot” track and proceed through the occupied turnout, causing a crash?    Ric ZPSX-AR

You may want to look at the Lock Block protection shown in the manual. This uses a block detector output connected to the manual switch inputs. When the block detector is active, it is the same as a manual switch input, and it holds the Hare in Dispatch Mode as long as the block is occupied. In Dispatch Mode, all Hare functions are inhibited, so the points will not move under the superior train. Although one block detector is shown, you could have one in the clear path and one in the throw path (clear and throw manual inputs). In this case, you would want to use a DCC Specialties Block Watcher for each since you can set a release delay time. This allows you to hold the switch in Dispatch Mode for a fixed amount of time after the train moves through the switch before ANY Hare function is active again, and you can do it for both routes through the switch with the first train arriving automatically the superior train.