using a 180 brick for track power-what is the voltage and amp requirement for a twin motor engine and how many engines can be operated off this brick without tripping the circuit breaker
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The amp draw will also depend on how much load you are putting on the motors, i.e. how many cars are you pulling, how tight are the curves, are there any grades on the layout.
Earl
I've had 4 modest trains on my flat layout running at one time on a 10 amp brick with no issues.
18 volts at 10 amps = 180 watts.
If these are post war AC motors, more current is drawn than modern DC motors. The voltage is the potential and effects the speed of the motor. Most are designed to operate between 10-14 Volts. More cars added to the consist and the train will slow down until you raise voltage to compensate. This also effects the current draw.
The modern DC motored engines draw between 1 and 3 amps depending on the motor/truck/engine design.
With Command control engines and pulsed DC to the motors, it is alot more complicated.
180 Watts is plenty of power. G
to put it another way-i am using a 180 brick to power 3 different engines all with twin motors using the dcs system off one tiu fixed port and popping the circuit breaker after about four minutes of run time
Tom:
You have answered your own question. As others have pointed out, there are lots of variables that will affect the answer to your question, but in your situation, it sounds like the six motors and whatever load you have them pulling is just a little beyond the limit for that brick on your layout. I think it's time for more power.
I wonder why it pops after 4 minutes. I always figure the startup draw is going to be the heaviest. When I'm pulling a lot and know it's gonna be close, I stagger their startups to keep the initial draw from being to much... but I've also seen this, where it's ok for a few minutes and then the breaker pops. Is it heat buildup within the brick or TIU?
bobdavispf;
The motors heat up and get a bit tighter, and the whole thing takes a bit more power.
also most circuit breakers trip fast at a certain overload, but right at the line, they pop after a few minutes.
Russell - thanks, that makes sense. I thought the motors just "loosened up" and hadn't thought about thermal expansion.
Stuff like lighted passenger cars really runs up the total current.
I just fired up my Legacy Lionmaster PARR T-1and ran around at a 50 to 70 scale speed with six boxcars and a lighted caboose, it was drawing right around 2 amps most of the time. Smoke adds about another 1/2 amp to the reading. Obviously, this is a dual DC motored locomotive.
There are eight Fastrack switched running on the track power, but they barely register on my meter when they're on without anything on the tracks.
That's a sample of one. 
Originally Posted by bobdavisnpf:
Russell - thanks, that makes sense. I thought the motors just "loosened up" and hadn't thought about thermal expansion.
There can be many complexities going on as an engine, or motor, heats up. I did a lot of performance testing on jet engines in my working days. When the engine accelerates from idle to high power, the first thing that heats up are the turbine blades or airfoils because they are in the airflow path and they are relatively thin. The blades lengthen as they heat and form a better seal and the performance improves. The next thing that heats up are the seals surrounding the blades and as they expand, they move away from the blades and the performance deteriorates because there is more air leakage. The last thing that heats up are the large discs that hold the blades because they are quite massive. As the discs expand, they move the blades closer to the seals again which reduces the air leakage and the performance improves again. It can take as much as 30 minutes to get good, stable performance numbers.
Earl
I'm not sure our trains are quite as finicky as a jet engine! 
