Mea culpa, mea maxima culpa. My brain seems to be shrinking at an accelerating rate. I guess – heck, I’m sure – there have been magazine articles and forum postings on this issue but I cannot seem to find them readily.
Can someone provide a brief description of the factors that make a turnout more or less DCC ready? I just saw an add for a new line of Micro Engineering turnouts that are said to be DCC compatible. It suggests this feature was not present in their prior product, but does not go into how they differ from prior Micro Engineering products to warrant this claim.
I assume it all relates to a need to avoid even the briefest of short circuits because of the faster acting circuit breakers (where DC can and does bull its way through a brief short circuit).
Where do classic old Shinoharas and Atlas customlines come out in this debate – I thought there was a comparison article in MR this but darned if I can find it.
As a supplement to that question, between the Peco electrofrog and Peco insulfrog turnouts, I have been under the impression that it is the Insulfrog that is the more DCC friendly of the two. But I am not sure why this is so if the frog is correctly wired, or maybe I am misreading the Peco instruction booklet. And I have visited layouts with electrofrog that are indeed DCC. I write this as someone (see first two sentences of this posting, above) who in a distracted moment has unintentionally purchased both insulfrog and electrofrog Pecos.
And as a still further complication, assuming Insulfrog is the more DCC friendly of the two, does that mean it is the more DC unfriendly of the two?
I am with you - I never really understood where the problem lies. I have been using turnouts with insulated frogs on various DCC layouts without any additional wiring than a set of feeders for each track, spur or siding and I never had any problems with engines stalling or short circuits. All I did is to check my wiring with a volt meter and to ensure my track is in gauge and clean.
DCC friendly does not me DC __un__friendly and a Peco Electrofrog can be also used with DCC, proper wiring assumed.
IMHO, it finally boils down to the questions of how many pick-ups your locos have and whether they can “bridge” the dead frog properly.
You’ll notice that on the unmodifies turnout the frog is not isolated. More importantly, you’ll also notice that there are two metal straps that join the two point rails which get removed during the modification. With the metal straps in place on the turnout in the picture, the straight stock rail and the two point rails will have the same polarity, while the curved stock rail will have the opposite polarity.
Assuming an engine will take the curved route, a problem may occur when the back of a wheel on the curved stock rail contacts the point rail at the same time. A short will then occur, tripping the command station (or other fast acting) breaker.
Some of the nay-sayers will claim that this cannot occur when all the wheels are in gage, but I have found that some of my 6-axle diesels will cause a trip. I believe that this is due to the attack angle as the diesel truck enters the turnout, primarily from the frog end.
My club just recently purchased some of the new Shinohara code 100 #6 turnouts, and these appear to be partially DCC friendly. They still have the metal strap at the ends of the points, but the metal strap at the closure rails has been replaced with two rail-joiner type connections.
The other impact of using DCC instead of DC is that a short circuit in DCC shuts down the entire power district - entire layout if only one power district - where a short circuit in DC only affects the specific block and the throttle selected for that block. With a short circuit in DC, the rest of the layout still works normally.
Good turnout wiring works better in both DC and DCC. Back in April 1963 - long before DCC was a gleam in anybody’s eye - Jack Work was proposing what is now called “DCC-friendly” turnout wiring in the pages of Model Railroader. My handlaid turnouts built in the '70s used “DCC-friendly” wiring.
But because a short at a turnout doesn’t shut down the entire layout in DC as it does in DCC, turnout manufacturers used inferior wiring schemes as a trade-off to enhance the mechanical strength and reliability of their turnouts. Linking the points together with a metal strip, and not gapping the closure rails near the frog does make the frog area and throwbars mechanically stronger. The cost is occasional temporary short circuits when a wheel back brushes against the open point. And the gap between open point and stock rail has to be wider than otherwise necessary to minimize this type of short circuit.
[quote]
Where do classic old Shinoharas and Atlas customlines come out in this
Due to the possibility of momentary shorts at the insufficiently-insulated frog, a lot of so-called, “DCC friendly,” commercial turnouts - aren’t.[|(]
Here’s a description of a truly DCC friendly turnout - with one caveat:
The closed point rides up on the base of the stock rail and makes positive, sliding electrical contact - locomotive weight just improves that contact.[^]
The open point is electrically dead, not connected to anything - no possibility of a flange-back short.[8D]
The wing rails and frog, a solid assembly, are powered from the appropriate stock rail through contacts on the point actuator, manual or automatic - no stepover shorts or stalling on a too-long insulated frog.[:O]
There are insulated rail joints on both frog-point rails, to keep the frog/closure rails isolated from the rails beyond the frog.[:P]
The caveat - it is the engineer’s responsibility to stop short of the clearance point if a turnout to be crossed in the trailing-point direction is not aligned for the branch his train is on. Signals may, or may not, be provided to inform personnel of the position of switch points.[swg]
If the above sounds like a description of my hand-laid specialwork, I’m sure that’s only a coincidence…[:-^]
Chuck (Modeling Central Japan in September, 1964 - with bulletproof track electricals)
Thank you, fellows, all of you - there is a lot of information and thinking here to digest. This is one exchange I need to print out rather than rely on finding it again.