REVERSE RUNNING: Decisions, decisions ... DCC or DC? Stepping outside the box with a contrary view On a smaller layout, I will tend to run fewer trains and may operate more often by myself – yes, that’s true. But that means I tend to focus more on the quality of the running experience, savoring the moments more since there’s less layout on which to run. This means the quality of individual loco performance becomes a bigger deal on small layouts.
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— by Joe Fugate
O
ne of the common control questions asked by new modelers is DCC or DC better for small layouts?
With DC, there’s not a lot I can do to tune individual locomotive performance beyond cracking the shell and fiddling with the mechanism. Now if I like that sort of thing, then great. But the laws of physics put limits to what I can do with the mechanism. With DCC, however, I can individually tune a loco’s performance across many different dimensions. Here’s just some of the things I can individually configure: Crack-the-throttle voltage/ speed
The most common answer: DCC is not needed for small layouts – unless you plan to run more than one train at a time.
Max throttle voltage/speed
I think that’s the wrong answer – and I’ll tell you why.
Down-throttle deceleration
Mid-throttle voltage/speed Up-throttle acceleration momentum
momentum (“braking”)
Page 113 • Issue 11-05 • May 2011 • Reverse Running Commentary
Adjust reverse speed as needed to
match forward speed
Startup kick voltage spike amount
Then there’s more advanced capabilities like dithering/torque compensation (DTQ) and Back EMF (BEMF). You can think of DTQ as being a little like DC pulse power in effect – although technically they work quite differently. With DTQ, I can apply different amounts of static adjustment to “smooth out” loco performance at lower voltage levels, making the motor turn more deliberately. Then there’s BEMF, which takes smooth operation of a loco to a whole new level. With BEMF the decoder dynamically senses the spinning of the motor and applies more or less voltage in an attempt to keep the motor spinning at the same rate. If you set BEMF up high, you can grab and hold the loco in place and the wheels will speed up as the decoder attempts to compensate for the fact the loco has slowed down!
With BEMF tuned properly, you can make a yard switcher literally float through complex yard trackage like it has great mass. It’s delightful! My point is this – if small layout owners care about getting the best loco performance possible, then they need to be running DCC, not DC. With DCC you can tune your loco performance in a dozen or more ways in seconds – all without ever removing the shell! I think DC is on its way out, frankly. Model airplane modelers today immediately think radio control – a similar thing’s coming with model railroading. Before much longer, it will just be assumed you go with DCC when you get into the hobby. While independent loco control is a great feature of DCC, the equally powerful but often overlooked application of DCC is its ability to tune individual loco performance. You just can’t get that level of loco performance tuning out of straight DC – only with DCC.
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