ReversingLoop Section Length

[rlandry6]

I have a reversing loop, actually it's a wye, but it's not going to be used for turning trains. It's providing two different ways to get into a townand establish direction. One of the sections is not going to be anywhere close to the length of the longest train going through it, but I'm not going to have any rolling stock that uses the wheels for a pickup, such as a lighted passenger car. As long as it is long enough to contain the loco and tender, which is the only power pick-up, will I run into a problem getting the automatic reversing module to switch polarities when a loco enters the section? Before everyone jumps on what poor design this is.... I already know that... I'm working within the space restraints that I have to work with.. If it just won't work at all, I'll try to redisign the wheel. Otherwise I'll do the best I can to work around it..

[dehusman]

If the tail of the wye is a stub the simplest way to work it is to have the switch on the tail of the wye control the polarity.  When the switch is lined for the west leg the polarity is the same as the west leg.  When the switch is lined for the east leg the polarity is for the east leg.  Very simple and pretty foolproof.

On a DPDT toggle switch there are 6 contacts. 

Connect the north rail on the west leg to the top right contact. 

Connect the south rail on the west leg to the bottom right contact.

Connect the north rail on the east leg to the bottom left contact.

Connect the south rail on the east leg to the top left contact.

Connect the west rail of the tail to the top center contact

Connect the east rail of the tail to the bottom center contact.

Dave H.

[selector]

You have it right, rlandry.  The gapped section that is to have its polarity altered needs only to be sufficiently long to encompass the length of the longest separation between the first and last power-transferring axles using that gapped reversing section.  If those widely separated axles are contiguous to the engine and to nothing else, you are fine.  Add one more axle that requires wipers to power something and you must add that length for the purposes of reversing the polarity safely within the length of the reversing section.