TOPIC THIS POST: All about DCC friendly turnouts
So what's the big deal with DCC Friendly turnouts anyway? Actually, it's all about shorting the track, and the most common place a short can occur on a layout is
at turnouts.
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A DCC friendly turnout is a turnout with less chance of a short if something doesn't track right. And a DCC friendly turnout can be a key component of good short management, in addition to the 1156 bulb we've already discussed.
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Any time I've seen the DCC friendly turnout discussion come up on boards and forums, there's always a lot of talk about the points end of the turnout, but I don't think that's the real issue. More derailments happen at the frog end of the turnout, and it's also the more likely place you'll see a short.
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So to focus on the frog end, you have two basic choices with how you handle the frog – live (powered) frog or dead (unpowered) frog.
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In both cases, the frog is generally isolated with gaps (unless you use the turnout to do power routing). If you look at a live frog turnout, the polarity of the power to the frog is based on the position of the points.
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But with a live frog turnout, if you run through the turnout from the frog end with it thrown against you, you will get a short. And we
don't like shorts on a DCC layout!
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By contrast, with a dead frog turnout, you expect the other wheels of the loco NOT on the frog to pickup the power. Most modern locos have all-wheel pickup and a dead frog is not an issue. Only if you have extremely short wheelbase locos will you have a problem with dead frog. I model the 1980s SP, so dead frogs work fine for me.
I spoke with Gary Siegel recently (owner of the wonderful L&N layout covered in MR back in the late 90s) and asked him which he was using: live frogs or dead frogs? Like me, Gary started out using live frogs but has now gone to dead frogs.
As to the pros and cons of live frog versus dead frog ...
LIVE FROG
Advantages:
- No dead spots in the track
- When entering a turnout thrown against you from the frog end, the train stops (shorts) preventing a derailment.
Disadvantages:
- Need contacts to route power reliably to the frog, which is more work since using the points alone is not reliable over time.
- A short on a DCC layout during “normal operations” is generally BAD.
DEAD FROG
Advantages:
- Easy to do – no extra wiring
- No short if the turnout is thrown against you – you just go on the ground like the prototype ( which can about 10% of the time cause a short ... so nothing's perfect).
Disadvantages:
- Dead spots in the track can be bad
- May have to cut gaps around the frog – which means more work.
WHAT I PREFER
I prefer dead frog turnouts. Modern all-wheel pickup diesels don't even notice them, although some older steamers without all wheel pickup may have trouble, as well as really short wheelbase locos.
You can get dead frog DCC friendly turnouts from several sources today:
- Atlas code 83 Super -Switch (#4, #6, or #8)
- Peco insulfrogs
- MicroEngineering turnouts
- Walthers/Shinohara DCC Friendly models (although in high demand so are often out of stock)
Older Shinohara/Walthers turnouts need modification to be made DCC friendly.
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Here's a photo of a Shinohara/Walthers old-style turnout that's been modifed to be DCC friendly (this turnout was recycled from an earlier layout, which is why it looks kind of grungy).
Study the photo and you can see what was done to make it DCC friendly.
- Replace the throwbar with a printed-circuit (PC) board throwbar. Remove the foil from the center of the throwbar so you don't short the two points. The foil under the stock rail helps conduct power to the nearby point so you don't rely on point contact alone for them to get power.
- Attach each point to its closure rail with half a rail joiner. This makes the point the same polarity as its closure rail, which minimizes the chance for a short at the point end if there is ever a derailment there.
- Solder a PC tie under the closure rails, to route power from the stock rails to the closure rails. Remove the foil in the middle of this PC tie so you don't short the two closure rails together.
- Cut gaps around the frog, and fill the gaps with black or gray styrene plastic glued in place with superglue. Leave the frog unpowered.
If you modify an older turnout as shown, even if you get a derailment at a turnout, you will only infrequently also get a short.
WHAT IF I NEED TO USE LIVE FROG?
If you do need to use live frog turnouts, then put an 1156 bulb in the feeder wire to the frog. This way, if you do happen to get a short from running the turnout the wrong way, only the one who gets the short will be affected by it – not the whole power district or layout.
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