Advice wanted: Trolley Show Layout Transformers

CW-80's are available through ebay fairly cheap, the later versions are very good transformers in my opinion. For JUST trollies or starter set 4-4-2 the Power Max or Power Max Plus would be even cheaper, but the CW-80 would be a better choice. The Power Max (30 watt) and power Max Plus (40 watt) wont run many 027 locomotives, so if you are also going to run any trains besides the trollies, I would avoid them.

  Now that I'm sure I started a RIOT, there will be many who will say to use something like a 1033, or RW , Excellent transformers unless the trains you want to run have a bell in their sound system, those postwar transformers wont have the buttons for the bells.

I think that the LW's will be a Good choice, again, so long as you don't want/need a bell control button.

Doug

(grin) Actually, 1034s are usually my transformer of choice for shows, BUT, as you say, I'm planning to run cars with bells (Lionel/K-Line interurbans, Rail King cars and hopefully an MTH Electroliner and/or Libertyliner) on the loops and a) it's a pain in the posterior to set up external horn/whistle buttons and b) the durn things tend to conk out after awhile. 

My main concern is whether the CW-80s would have enough oomph to handle large loops like this...  :)

 
VTY,

 
-MMM-
 

   The CW-80 should be fine for those layouts, other than possibly needing  extra feeders, a result of track length/voltage drop, not because of using a CW-80, and that might not be necessary. I have run my Lionel dual Motor LionMaster Challengers, Cab-Forward and Big Boy with a CW-80, without any problem until I added 8 scale size lighted (4 bulbs per car) passenger cars behind the challenger. I would expect that a Trolley or almost any train you are likely to run on your display layout will be fine with a CW-80. The only exception would be that SOME MTH PS2 locomotives don't play nicely with the Phase Control (I Think I got that right, Bob?) current that the CW-80 puts out, SOME PS2 locomotives do funny things unless run on a Pure Sine Wave current.

Doug

The length of the track has nothing to do with the current rating of the transformer.  The current drawn by the trains and other loads determines that.  The length of the track does figure into how much voltage drop there is between the transformer and the train and therefore how much higher the transformer voltage must be to get adequate voltage at the train.  However, the condition of the track joints and the number and gauge of any feeders also have an effect and may virtually eliminate voltage drop even on a large layout.

Typical track with joints in good condition is roughly equivalent to 16 AWG copper wire in resistance, which is 4 milliohms per foot.  A 10-by-10-foot loop therefore has about 160 milliohms of resistance.  However, if it is a complete loop, the train can get only 20 feet away from the transformer; and there are then two parallel paths feeding it.  So the actual resistance is only 40 milliohms.  A train drawing 5 amperes will therefore have a voltage drop of only 200 millivolts, which is negligible.  With the stop blocks that you describe, your loops will not be complete.  But, with 14 AWG or heavier feeders to the blocks, you should have no significant voltage drop.

The bottom line is that, with decent track and wiring, you can forget about the layout size in choosing a transformer and simply consider the load of the trains that you will be running.