Those little train set controllers are rated at 0.70va, so their output is limited to one open-frame motor (athearn old-style, most older brass, Bowser kits) and a few lights (either incandescent or diodes.) Doesn't make any difference how many scale miles of track that one locomotive runs on. Just don't add a second.
Present-day locos with can motors and LED headlights draw much less, so the wimp controller can run two, or, maybe, three. The down side is that all of them would run at the same voltage, with no independent control.
Those wimpy-packs show up regularly at yard sales, usually accompanied by locos that don't work (and aren't worth repairing,) cars that make good kitbash fodder and track that may or may not match what you already have - all for less than MSRP of the pack. I have several, of three different brands, thanks to my sister, the yard sale fanatic.
My suggestion would be to wire for two-cab control and use separate speed/direction controllers (two wimps or a dual-control MRC pack) plus a third source for switch machines, especially if you are using toy train turnouts. One Atlas switch machine will draw more power in a momentary surge than a couple of open-frame motors at full voltage.
Chuck (modeling Central Japan in September, 1964)
If you are wanting to run two trains independantly, you will need two power packs, or a dual power pack like MRC's Tech 4 model 280.
http://www.modelrec.com/search/product-view.asp?ID=1296
Rotor
Jake: How often does the train go by? Elwood: So often you won't even notice ...
You'd do well to get a MRC Tech series power pack. Any one of these would have enough power to run two locos easily.
Walther's page on MRC Tech series power packs.
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
jeffrey-wimberly wrote:That will run two Athearn BB locos for a little while. Eventually the amp load will destroy it, as the cheap LL power packs lack a circuit breaker.
Really? I'm surprised it could get a UL tag without a breaker. That strikes me as a genuine fire hazard. After all, the intended use is something where short circuits are common events.
It takes an iron man to play with a toy iron horse.
It takes power to run locomotives. It takes no power at all to run tracks, because they don't do anything by themselves. So, most of what the power pack needs to do is run engines. If you can put 2 locos on the same track and run them, then you can probably put the same 2 locos on different tracks and run them.
There are a few other considerations, though. If your track loops are very long, then there will be "voltage drop" from one side to the other. You can help this a lot by installing multiple feeders to get the power to the track more efficiently. Rail joiners are OK for power distribution, but with time they will loosen up, and they too will cause voltage to drop from one side to the other. Again, more feeders is the answer, and soldering the feeders to the rails is the best way to avoid problems with rail joiners for power. The typical way of doing this is to use a heavy gauge wire (#12 or #14) as a "track bus" beneath the layout, running out from the power supply, and then thinner wires (#20 or #22) from the bus to the track.
If you have illuminated passenger cars, they'll also draw power from the track. Be aware of this, because it can sneak up on you as you add more of them to your layout.
If you're using the same power pack to drive your electrically-operated turnouts, then you may notice a brief drop in engine performance when you throw the turnout. Likewise, if you're using it for structure lighting, streetlights, etc., each of these will draw a bit of power away from running the locomotives. You are really better off with a separate power supply for everything other than your track.
Short answer: Probably.
Disclaimer: Your results may vary. Exceptionally large ovals may require additional feeders. Offer not valid when layout is occupied by three or more locomotives, in which case DCC upgrade is recommended.