I have a bjiou promlem-ette with some Peco diamond crossings. The way
they are built, there is an exposed rail-end of opposite polarity to
the adjacent rail such that if the back of the wheel touches it, a
short occurs. But the other end, where the adjacent rails are of the
same polarity, is insulated! Two crossings (different angles) are
both the same. Since the crossovers are nowhere near a point and I
use DCC (so don't have isolated sections of track) this is a bit
Obviously I can fix it simply by filing back slightly and adding a
thin insulating piece over the rail-end, but why is it done that way?
Simply reversing the insulated and exposed ends would solve the
Noticed the exact same thing on my crossovers. No idea why it is this way
except maybe the wiring is simpler and there should only be a small short if
any at all!! I'm gonna modify the wiring on mine and fit a relay so that any
points facing the crossover will cause the two offending rails for each
direction to be isolated when the trains are travelling in that direction.
The wiring provided underneath the crossover should provide all the
connection I need but I'll snip a few of the interconnections.
So just turn the crossing around - the angle will be a little larger, but
who will notice?
Slightly more seriously, you need to isolate both routes and apply one of
those automatic revewrsing loop thingies they make for DCC or power both
blocks from their nearest turnouts and utilize a diode matrix so that both
routes can't be selected at the same time.
In message , "Just zis Guy,
you know?" writes
I'm sorry about getting heavy about this, but other people have been
going on about correct railway terminology (see threads about "frogs")
Please do not use the word "crossover" to refer to a diamond crossing. A
diamond crossing is not a crossover. A crossover is two points
(turnouts, switches) in a double track arranged so as to cross the train
over from one track to the other.
On Thu, 10 Feb 2005 12:44:04 +1300, "Greg.P."
wrote in message :
I've come to the conclusion that messrs. Peco have designed these on
the assumption that the crossing lines will have opposite polarity
(not unreasonable). I will be cutting back the exposed rail slightly
and laying in an insulator, and painting the insulated section in the
middle with conducting paint to reduce stalling on the crossing. I
really don't want to get into special wiring just for a couple of
crossings when the rest of the wiring is so simple.
I am not sure how well diode matrices work with DCC. I was under the
impression that they tended to cause problems, is that not right?
I imagine that would be the way most (British) modellers would use them.
By simplifying wiring in that manner, you're restricting current collection in
a fairly major manner, in that you will have; _dead frog, insulated rail join -
insulated rail join - insulated frog in quick succession.
If you're driving turnout motors with DCC decoders that will not allow a
separate power supply then diode matrixes probably will cause problems, but
most accessory decoders now allow a separate supply. Otherwise there is no
I've had diode matrixes in use for 25 years using IN4001 diodes driving Peco
and H&M motors and never had a failure.
I've never had any problem.
I assume you mean a 'scissors cross-over?
Pilz make a nice one, but all wired as a single unit. (it took ages to isolate
the two main lines)^:
The problem with a preassembled one is that not everyone uses the same track
spacing, particularly in stations where platforms are likely to be involved.
On Fri, 11 Feb 2005 09:27:07 +1300, "Greg.P."
wrote in message :
Yes, maybe. All my track has the same polarity because it was wired
for DCC from the outset.
Er, what? No insulated rail joins at all on my crossing. Cross
porpoises? This is a diamond crossing (SL84), not a crossover as per
the subject (as John picked me up on below).
No, my point motors are all supplied separately via passing-contact
switches, I don't use DCC to drive them. Partly because of the cost
and partly because it amuses me to build the faux frames. DCC is only
on the track.
I do the same thing for analogue. I haven't yet used a diamond crossing where
encountered a polarity problem.
Sure, but why power the conflicting track? You can't run two trains across a
crossing at once and unless your layout consists of two independent, overlapping
circles you must have turnouts somewhere.
OK, so capacitor discharge units are indicated and why operate every point
individually when you could operate routes?
A simple example:
With a three way turnout you have three possible routes but four solenoids - why
provide four buttons/ passing contact switches which have to be pressed in the
order when three buttons will do the job without the complication of sequence?
If you add another turnout beyond the three way you have six solenoids/six
but only four possible routes.
On Fri, 11 Feb 2005 12:31:28 +1300, "Greg.P."
wrote in message :
My layout has two loops and some branches, all connected by various
points, and all permanently powered with the same polarity. There are
no isolating sections anywhere, no relays, no microswitches, and the
only insulating joiners are on electrofrog points. Oh, wait, there is
one isolated section - the programming track. That can be switched in
and out of the main circuit (so you can drive a loco in, switch a DPDT
switch and program the decoder). It also acts as a loco siding.
The nearest points on one of the tracks are just under 8ft away and on
the other there is a set 6ft away and another set 14ft away. In
between is a station. If I isolated the crossing I could not run a
train across the main line behind another train which was pulling out
of the station away from it (or indeed move it within the station).
Maybe that would be verboten on the prototype anyway, I don't know.
I never even considered doing it any other way. Maybe I should have,
but I didn't. Every joiner (except the insulating ones) has a drop
cable soldered to it, and they are all wired to one of a number of
2.5mm^2 busbars underneath, all of which are connected back to the
Lenz DCC controller. There is no detectable volt drop anywhere on the
layout, which was one of my key goals since my old layout (which used
mainly the track to conduct the electrickery) was prone to volt drop
in several places despite only being 12ft square. So there it is.
The two crossings are the only place where I have a problem thus far.
It's always possible to change wiring.
My concern is that you will end up with a lot of non-conducting rail in a short
Many short wheelbase locos get hung up on dead frogs, hence Peco offer the live
but two dead frogs and two dead sections of rail taken at slow speed in the
is asking "what the limit is".
A track crossing the main line is going to be signalled - use the signals to
power from main-line to branch.
Phil: You are forgetting 2 things:
1: The Kiss principle - Keep it Simple
2: Not all layouts use physical signalling - for which the prototype
is Radio Tokenloess Block Signalling or 1 engine in steam
Just because its in this uk model rail group does not mean it is
following BR Mainline (or Railtrack!) practices
Switching the supply ineccessarilly is introducing a possible point of
failure - multiple current collection from locos is a better solution, and
so would buying an alternative make of fcrossing with a slightly larger
than Peco's - to no real detrimiment - only benefit.
Power should also be maintained on all sections to maintain coach
lighting. REMEMBER that 'power o the 2 rail track' is NOT prototype
practice - it is a modelling convenience.