Size of dummy engine and consist load for voltage drop check?

Classic Toy Trains Forum
1

I have a 30” insolated block ten feet from my control panel.

Suppose I have ‘xx-gauge’ wire feeding it. I leave the size of ‘xx-gauge’ open for discussion.

If I put the control transformer at 14V, under NO load the block will also be 14V, regardless of the size of “xx-gauge”. VOMs draw almost no current.

If I put an engine on the block, I can see the voltage drop monetarily until the engine runs off the end of the block.

But, if I had some sort of resister/diode/capacitor combination that would simulate the load of an engine and also lighted consists, I could simple alligator clip it to the block and test the wiring and connections.

Has anyone done this?

Thanks.

–Tom Meriam

PS: I am VERY SORRY that I used “alligator clip” as a verb…

2

You show creativity. Even though “fasten” or “attach” would work, my policy is when you need a word that don’t exist, make one up. [(-D] [(-D] [(-D] [(-D]

3

All you really nead is a resistor for a dummy load.

You will have to estimate the current that the train will draw or measure a real train. One way to do that is to put a resistor, probably less than 1 ohm, in series with the transformer output to the layout generally and measure the voltage across the resistor. The voltage across that resistor, divided by the resistance, will be the train current in amperes.

Then, for your dummy load, divide 14 volts by the current you measured. That is the resistance of the dummy load. The power that it dissipates as heat will be the square of 14 volts (196) divided by the resistance. (It would be prudent to get one with a rating about twice what you calculate.)

However, you should be able to calculate the voltage drop just from a knowledge of the wire size, “xx”, once you know the current. Copper wire resistances are approximately .001 ohm per foot for AWG10, .0016 for AWG 12, .0025 for AWG 14, .004 for AWG 16. Calculate the wire resistance by multiplying this number by the wire length. Then multiply by the current that you measured or estimated to get the voltage drop.

4

Thank you Bob Nelson. I will try what you have suggested.

–Tom Meriam

5

Notice that the dummy load might be pretty big. If the (simulated) train current is 5 amperes, for example, the power dissipation is 70 watts. That’s a big resistor.