Shinohara

[Pruitt]

Are the newer Shinohara code 70 HO standard-gauge turnouts "DCC Friendly?"

[fwright]

DCC friendly is more an advertising gimmick than anything else. Read Joe Fugate's post on 10 years with DCC, I learned plenty there. I'm sure Joe can correct any mistakes in the following:

I have not looked at new Shinohara turnouts; I own several older ones. The older ones use what used to be "standard" turnout electrical practice. The two points are linked together with a metal throwbar, and the frog is powered by which ever point is touching its adjoining stock rail. The advantage was that if the switch was thrown against a spur, both rails on the spur would be of the same polarity, and nothing would run. This "feature" could be used to save block toggle switches and associated wiring in conventional DC.

The drawbacks of this design are:
1) You had to have a good knowledge of how your layout electrical system worked to put some necessary gaps in place. Basically, anytime a frog could receive electricity from the diverging end of the turnout, there had to be an electrical gap somewhere between the frog and the feed point.
2) Points touching stock rails are unreliable conductors of track power. Often a point wouldn't make complete electrical contact with the stock rail, or the weight of trains running over the point would break the electrical contact. When this happens, the point, closure rail, and frog and frog rails are unpowered to the next electrical gap (and your train stalls).
3) The back of a wheel riding on a stock rail might momentarily contact the adjoining (and opposite polarity) point rail, causing a momentary short circuit. This was pretty much resolved as wheels were manufactured to closer tolerances, and the distance between point rail and stock rail was increased slightly (which increases the throw distance to change the turnout direction).
4) A train approaching a turnout from the frog end with the turnout set against it would cause a momentary short circuit if/when its metal wheels bridged the electrical gap in the frog rail.

In conventional DC, a momentary short is not a show stopper. It is annoying, it can cause wheel pitting and sparks, but if the train has any momentum, it will continue past the point of the momentary short, break the momentary short, and continue as normal. Worst case, the train causing the momentary short stops, and the circuit breaker in the power pack trips.

With DCC, a short causes the entire power district to almost instantly shut down to protect the electronics, shutting down all trains powered by that power supply. Depending on the situation, if the momentary short is resolved by momentum, the power may/may not come back on. If the power comes back, the decoders and throttles will likely reset themselves, but not necessarily to the previous condition. Some sound decoders have enough initial current draw that they may prevent the circuit breaker from even turning the power back on, even with the short circuit removed.

Ways to fix this:
1) Buy DCC-friendly turnouts. These have points that are electically isolated from each other, and are electrically tied to the adjoining stock rail. Note that this improves both DC and DCC operation, and allows the points to be closer to their stock rails (less throw distance/more realistic appearance).
2) Because if 1) is implemented, points are now of opposite polarity, and the frog must be insulated from the points. Gaps are cut in front of the frog, and usually just behind it as well. This insulates the frog completely (no power) unless a separate feeder is run whose polarity is controlled by the trunout setting. The frog feeder minimizes stalling due to no power at the frog at the expense of an extra feeder and electrical contact at the switch machine, throw mechanism, or turnout control. Again, both DC and DCC operations benefit, regardless of whether the frog is "dead" or "live".
3) The remaining source of momentary shorts - a train approaching a turnout thrown against it and bridging the electrical gap with a metal wheel - is eliminated by using dead frogs, or putting in a very short dead section - just a little longer than the wheel gap span - just beyond the frog. Some people just live with a momentary short figuring it helps people not to approach a turnout thrown against a train too closely. Or put a current limiting device - see Joe Fugates's DCC forum again.

It's not terribly difficult to make the changes to an older Shinohara turnout to bring it up to current practice. Biggest change is to fasten the point rails to a non-conducting throw bar. Many use a PC board tie for a throwbar, solder the point rails to it, and then cut a gap in the foil on the throwbar. Feeders are added to connect each point to its adjoining stock rail. Then gaps are cut in the closure rails just slightly in front of the frog (and usually just after as well). Finally, a feeder and polarity controlling contact are added to the frog if a live frog is desired.

Hope this helps.

[fwright]

To more directly answer your question - check the throwbar of the turnouts in question. If the throwbar is metal, or there is a metal link between the points at the throwbar, it is of the older design. The new, DCC-friendly turnout will have the points insulated from each other. Another visual indication of improved design is small gaps in the 4 rails extending from both ends of the frog.

Fred Wright

[Pruitt]

If I see one I'll be able to tell. I'm thinking of ordering some but haven't seen them - I was hoping someone who has bought some recently would be able to tell me. Thanks for the replies, though...