Buss line information needed.

[Boonter]

In a recent post about buss line usage a couple of statements confused me.  I am planning to use a buss bar (Mmultiple connector bar) closer to the distant parts of the track to add more lock ons to a large layout. The bar is homemade using a brass strip 1/8 x 1" with screw terminals for input and redistrabution.

My concept of buss bar usage has a larger gage wire connected to the transformer with smaller gage wires feeding from the terminals to the lock ons.  One post stated that the buss line should RETURN to the power source.  That seemes incorrect to me.

Another reccomendation was that two wires are needed (a second buss bar?) for the 'commom'  or outside rail.  Us the commom necessary at each lock on ?  If so, why ?

All answers, comments corrections and advise are appreciated !

[lionelsoni]

The electron current needs a complete circuit to flow.  That means two wires between the transformer and the track, one for electrons going to the track, the other for those coming back.  The reason for adding feeders to distant track is that the track has resistance.  The current flowing through the track, in amperes, multiplied by the track resistance, in ohms, equals the voltage difference between the transformer and the train.  That voltage difference is subtracted from the total voltage measured at the transformer.  Both the center rail and the outside rails have resistance, although the two outside rails together have half as much as the center rail and therefore contribute half as much voltage drop.

In a marginal situation, you can get away with eliminating the center-rail voltage drop only; but to get it all, you need feeders to the outside rails too.

As a rough rule of thumb, the rails are equivalent to 16-AWG wire.  So it's important to use heavier wire than that for the feeders if you want to make a substantial reduction in the voltage drop.  You can find 14, 12, and 10-AWG easily at home-improvement stores.

However, it is important for safety that you use wire heavy enough to carry safely the greatest current that your transformer can put out.  For example, a ZW or Z transformer's circuit breaker trips at 15 amperes; so a layout powered by one of them should have no smaller than 14 AWG wire.

By the way, "buss" means "kiss"!  For a wire that goes everywhere, the word is spelled "bus", from the Latin "omnibus", meaning "for all".

[Boonter]

Bob, many thanks for the clarification and understandable explination.  I;ll jist make another 'BUS' bar for the second wires. 

In passing, as a young man in the automotive parts business the explination for the term BUSS bar that it was derived from the Buss fuse company, maker of automotive fuses.  Interesting comparison of terminoligy.

[lionelsoni]

You're welcome.

I'm pretty sure that the two-s spelling resulted from confusion with that company's name.  It is actually the surname of Al, Frank, Joe, Harry, and Lee Bussmann, brothers who founded the company in 1914 in St. Louis.  I think that most people don't notice the connection in meaning between bus as a vehicle and bus as an electrical conductor, that is, that the vehicle is "for all" the population to ride and that the wire carries current "for all" the loads that it serves.  You will sometimes see the vehicle actually called an "omnibus", the full word that "bus" is shortened from.

 

[phillyreading]

You do not need a return set of wires to the transformer, that will only get you confused. Also use a differant color wire for hot and common or return wire, or buy AWG 14-2 with ground wire and you get three wires already color coded, except the center wire is bare or wrapped in paper. Single wires might be more expensive per foot, so that is why I mentioned the 14-2/ground.

[lionelsoni]

You do if you want to bypass the resistance in the outside rails to eliminate the voltage drop that those rails can produce.  I doubt that using such wires will cause anyone much confusion.