There is a lot made of turnouts being
DCC "friendly". But most of the companies touting "DCC
friendly" fail to tell you the "whole" story. We like
Peco InsulFrog turnouts because they are 100% DCC friendly, not just
partially friendly. This is especially important for beginners and people
who have a hard time understanding electrical matters. While live frog
turnouts can be used with DCC, there are things the user must know and
take into consideration in order to use them successfully. With Peco
InsulFrog turnouts, you just install them like another piece of track,
and use them. And they are of the highest quality for not much more
money than cheap turnouts.
There are three points to being DCC friendly:
- Wheel flange clearance between stock rail and open point
- Frog and frog rail changing polarity
- Point vibration causing power/signal problem
Most so called DCC friendly turnouts address point
1. Some address point 2. Most do not address point 3 (which we will
cover in detail below). |
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| 1. Wheel flange clearance between the
stock rail and open point |
With
power routing turnouts, both points usually carry the same polarity.
Iillustration #1 at right shows how the power flows on a normal power
routing turnout. Polarity is shown with Red and Green lines drawn over
the rails. |
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You can see that the open point has the opposite
polarity. If the clearance between the stock rail and open point is
not enough to allow the wheel flange to go through without touching
the point, you will have a short circuit. |
Note: These short circuits generally don't matter
when operating with DC analog because the typical power pack doesn't
put out enough current to harm anything (they generally put out only
enough power to run one train). When a short circuit happens, the
power pack simply puts out all the power it can for the short period
of time the short circuit is occurring, and no harm is done. But with
DCC having enough current on the rails to run ALL the trains, a short
circuit can cause harm. Therefore, Short-Circuit Protection is built
into boosters. When a short circuit occurs, the booster shuts down
and the trains stop.
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This issue is totally irrelevant with Peco InsulFrog
turnouts for two reasons. As you can see in Illustration #1, there is
plenty of clearance for even the fattest wheel flange. But more important,
the open point never has the opposite polarity. Illustration #2 shows
how power flows in a Peco InsulFrog turnout. |
The insulating frog point (shown
in blue) is only 5/16 of an inch long. The total span of rail without
power is 11/16 inches long. Rarely would you ever have more than one
wheel at a time on this gap of power. |
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Live frogs are good for nature, but are not
needed for model railroads anymore. In the past, when locos didn't have
all-wheel power pickup, and the power pickup they had wasn't very good,
you needed all the power you could get on every wheel that had power
pickup. This made live frogs all but a requirement for a good-running
railroad. But with the quality built into today's locos, the power provided
by a live frog just isn't that important any more - providing you keep
your locos properly serviced. In fact, with DCC, they can be a detriment.
There are many web sites with all kinds of information on how to keep
the frog from causing a short circuit: to include installation of 1157
automotive bulbs to feed the power, and other things. But, if you don't
really need power there, why go to all that trouble when you can install
a turnout that doesn't have that problem to start with. Giving up this
one small area of power is a small price to pay for a turnout that's
overall easier to use. |
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| 2. Frog and frog
rail changing polarity |
Some people call this Power Routing, some call
it Live Frog. Illustration #1, above, shows how a power routing turnout
is powered when closed for the through route. Illustration #3 shows
how it is powered when thrown for the divergent route. |
You can see that all the track pieces in the
middle changed from green to red. With Peco InsulFrog turnouts (Illustration
#2, above), all the track pieces stay the same regardless of which way
the turnout is set. |
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| The reason this is called power
routing is that it can make the unselected route dead. In the illustration
above, you can see that both rails of the through route have the same
polarity. This means a loco can't run (the through route is dead). With
DC analog, people used this to be able to run a loco onto a siding to
let a train pass. But with DCC, this is not needed (simply because each
engineer is controlling their trains independently regardless of track
power).
With DCC, it's more important to have good solid
track wiring to all rails. Running power through the point contacts
is not as positive as connecting the siding directly to the track power
bus.
You can read more about turnout point power below.
You can read more about accommodating the switching
of polarities of power routing turnouts in the About
ElectroFrog Turnouts section. |
| 3. Point vibration
causing power/signal problem |
|
With DCC, power to the points
is far more important than power to the frog. The typical turnout provides
power to the points via slip joints, brass contacts, or some other method.
The problem is, when your loco is traversing the points, the points
vibrate. And with just that little bit of movement, power is interrupted.
It's only for just a fraction of a second, but just long enough to mess
with the signals. Unlike a spot of dirt on the rail, a whole truck of
your loco will be on it. This means that 1/2 of your power pickup for
that side is gone for that fraction of a second. At first blush, this
wouldn't seem too much of a problem, and usually isn't - after all,
you still have as much power in the other truck as locos used to have.
But, with so many more things that DCC does than you could do before,
this kind of power interruption can cause spikes that can be disruptive.
Peco turnout points get power from
two directions. But more importantly, both of those directions are more
positive than most other turnouts provide.
- The points make contact with the stock rails like
all others. But, only Peco has a spring that forces the points tightly
to the stock rails. Besides providing good solid electrical contact,
it also resists vibration caused from locos running on it.
- The points also have wipers which make contact
to the bottom of the stock rail. So, with the spring holding the
point tightly against the stock rail, and the wiper making contact
to the bottom of the stock rail, it has two points of contact for
power transfer at that end of the point.
- The points also have a unique pivot connection
to the closure rail. It doesn't just ride on the pivot pad as points
do on some turnouts. It has two tabs that stick through a hole in
the pad, and bend over to secure it to the pad. This provides contact
from the tabs to the hole in the pad, as well as between the top
of the pad and bottom of the point (again, two (not one) points
of contact from that end). Since the frog rail is connected to the
closure rail, connecting track power to the frog rails will feed
power to the points via the closure rail pivot point. The point
gets power from both directions: from the point and wiper with a
spring to hold it tight, and from the pad contact with prongs to
hold it tight and also transfer power.
No other turnout has all these advantages
for DCC.
If you absolutely need to have Power
Routing Live Frogs, read about how Peco's ElectroFrog turnouts work
in the About ElectroFrog Turnouts
section. |
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