Diamond crossings and DCC

Hi,

As someone gearing towards converting my layout to DCC, I was running a
simple figure of eight circuit using Bachmann's DCC-fitted Class 25 and an
unfitted Bachmann Deltic using Bachmann's E-Z Command controller. The
diamond I was using was a Fleischmann Profitrack wide angle short crossing.

After a few circuits, the Class 25 suddenly changed direction and crashed
back into the Deltic!

Was this due to a momentary short on the crossing? And is this a problem
inherent with all diamond crossings and DCC?

I ask because I current have eight Peco long diamond crossings on my main
layout, and dread to think of the consequences if this were to happen when
I went live DCC on my main layout!

Thanks in advance for any help and/or suggestions you can provide.

Lloyd

On Mon, 16 Jul 2007 10:54:26 -0000, Lloyd Butler
<lloydatnospamchedworthnet> wrote:

>Hi,
>
>As someone gearing towards converting my layout to DCC, I was running a
>simple figure of eight circuit using Bachmann's DCC-fitted Class 25 and an
>unfitted Bachmann Deltic using Bachmann's E-Z Command controller. The
>diamond I was using was a Fleischmann Profitrack wide angle short crossing.
>
>After a few circuits, the Class 25 suddenly changed direction and crashed
>back into the Deltic!
>
>Was this due to a momentary short on the crossing? And is this a problem
>inherent with all diamond crossings and DCC?
>
>I ask because I current have eight Peco long diamond crossings on my main
>layout, and dread to think of the consequences if this were to happen when
>I went live DCC on my main layout!
>
>Thanks in advance for any help and/or suggestions you can provide.
>
>Lloyd

Hi Lloyd,

You have encountered something which I have frequently
surmised. My source of query being tender drive locos where pick-up is
spread over a long distance and the silmilar arrangement with the
older Hornby DE range ( cl25 thro' 52). The newer Hornby locos have
pick up for their whole length with entire side devotion to power
sourcing. This can give differing problems ranging from bridging
isolating joints, bridging sections carrying different line power in
adjacent insulated parts or shorting out on change over sections. This
is equally true for DC and even now I come across the odd short when
using a different loco. I can see how a DC "splash" could generate a
spurious reverse command.

If I was having that problem then I would make each leg of the
crossing dependant on the state of the other. i.e. if one leg is
energised then the other is de-energised. Being a short crossing, you
would need to extend the length of each stub to make a section long
enough to accommodate a loco to ensure that it can come to a halt
clear of the crossing if it arrives too fast and uninvited! This is
very simple using a 2 pole, 2 position ( or, on off on) switch.

Lloyd Butler wrote:
> Hi,
>
> As someone gearing towards converting my layout to DCC, I was running a
> simple figure of eight circuit using Bachmann's DCC-fitted Class 25 and an
> unfitted Bachmann Deltic using Bachmann's E-Z Command controller. The
> diamond I was using was a Fleischmann Profitrack wide angle short crossing.
>
> After a few circuits, the Class 25 suddenly changed direction and crashed
> back into the Deltic!
>
> Was this due to a momentary short on the crossing? And is this a problem
> inherent with all diamond crossings and DCC?
>
> I ask because I current have eight Peco long diamond crossings on my main
> layout, and dread to think of the consequences if this were to happen when
> I went live DCC on my main layout!
>
> Thanks in advance for any help and/or suggestions you can provide.
>
> Lloyd

Whether for DC or DCC, crossings are a problem. If the isolating gaps
occur at the frog itself (eg, a sliver of plastic molded in to separate
the rails), it's possible for a metal wheel to bridge from one rail to
the other. Check whether that's the way Fleischmann does it.Many
manufacturers do so, since it simplifies connecting the crossing to
other track pieces - you don't need isolating railjoiners. But IMO, this
is a bad way of isolating a crossing.

The proper way IMO is to isolate the whole crossing at each end of each
arm. Cut gaps between the frogs within the crossing. The frogs should be
all-metal. Or else bond the two rails of the of the frog to each other.
Electrically, the crossing will then consist of four L or V shaped
sections of rail, A, B, C, and D.

For one route through the crossing, A+B and C+D will connected to power
and ground respectively; for the other, A+C and B+D will be thus
connected. You need a switch or relay that will energise one route and
only one route through the crossing at a time. By judicious placement of
detectors ahead of each arm of the crossing, you can automate this, but
you will have to install mechanical or electrical interlocking as well.
Automated or not, extra sets of contacts will provide stopping (safety)
sections, and interlocked signals as well. IOW, you could make this
crossing a showpiece of signalling technology... ;-)

HTH

--
Wolf
'Just because it's true doesn't mean it's the right answer.'

	#1
Lloyd Butler	Diamond crossings and DCC Hi, As someone gearing towards converting my layout to DCC, I was running a simple figure of eight circuit using Bachmann's DCC-fitted Class 25 and an unfitted Bachmann Deltic using Bachmann's E-Z Command controller. The diamond I was using was a Fleischmann Profitrack wide angle short crossing. After a few circuits, the Class 25 suddenly changed direction and crashed back into the Deltic! Was this due to a momentary short on the crossing? And is this a problem inherent with all diamond crossings and DCC? I ask because I current have eight Peco long diamond crossings on my main layout, and dread to think of the consequences if this were to happen when I went live DCC on my main layout! Thanks in advance for any help and/or suggestions you can provide. Lloyd

	#2
Peter Abraham	Re: Diamond crossings and DCC On Mon, 16 Jul 2007 10:54:26 -0000, Lloyd Butler <lloydatnospamchedworthnet> wrote: >Hi, > >As someone gearing towards converting my layout to DCC, I was running a >simple figure of eight circuit using Bachmann's DCC-fitted Class 25 and an >unfitted Bachmann Deltic using Bachmann's E-Z Command controller. The >diamond I was using was a Fleischmann Profitrack wide angle short crossing. > >After a few circuits, the Class 25 suddenly changed direction and crashed >back into the Deltic! > >Was this due to a momentary short on the crossing? And is this a problem >inherent with all diamond crossings and DCC? > >I ask because I current have eight Peco long diamond crossings on my main >layout, and dread to think of the consequences if this were to happen when >I went live DCC on my main layout! > >Thanks in advance for any help and/or suggestions you can provide. > >Lloyd Hi Lloyd, You have encountered something which I have frequently surmised. My source of query being tender drive locos where pick-up is spread over a long distance and the silmilar arrangement with the older Hornby DE range ( cl25 thro' 52). The newer Hornby locos have pick up for their whole length with entire side devotion to power sourcing. This can give differing problems ranging from bridging isolating joints, bridging sections carrying different line power in adjacent insulated parts or shorting out on change over sections. This is equally true for DC and even now I come across the odd short when using a different loco. I can see how a DC "splash" could generate a spurious reverse command. If I was having that problem then I would make each leg of the crossing dependant on the state of the other. i.e. if one leg is energised then the other is de-energised. Being a short crossing, you would need to extend the length of each stub to make a section long enough to accommodate a loco to ensure that it can come to a halt clear of the crossing if it arrives too fast and uninvited! This is very simple using a 2 pole, 2 position ( or, on off on) switch.

	#3
Wolf	Re: Diamond crossings and DCC Lloyd Butler wrote: > Hi, > > As someone gearing towards converting my layout to DCC, I was running a > simple figure of eight circuit using Bachmann's DCC-fitted Class 25 and an > unfitted Bachmann Deltic using Bachmann's E-Z Command controller. The > diamond I was using was a Fleischmann Profitrack wide angle short crossing. > > After a few circuits, the Class 25 suddenly changed direction and crashed > back into the Deltic! > > Was this due to a momentary short on the crossing? And is this a problem > inherent with all diamond crossings and DCC? > > I ask because I current have eight Peco long diamond crossings on my main > layout, and dread to think of the consequences if this were to happen when > I went live DCC on my main layout! > > Thanks in advance for any help and/or suggestions you can provide. > > Lloyd Whether for DC or DCC, crossings are a problem. If the isolating gaps occur at the frog itself (eg, a sliver of plastic molded in to separate the rails), it's possible for a metal wheel to bridge from one rail to the other. Check whether that's the way Fleischmann does it.Many manufacturers do so, since it simplifies connecting the crossing to other track pieces - you don't need isolating railjoiners. But IMO, this is a bad way of isolating a crossing. The proper way IMO is to isolate the whole crossing at each end of each arm. Cut gaps between the frogs within the crossing. The frogs should be all-metal. Or else bond the two rails of the of the frog to each other. Electrically, the crossing will then consist of four L or V shaped sections of rail, A, B, C, and D. For one route through the crossing, A+B and C+D will connected to power and ground respectively; for the other, A+C and B+D will be thus connected. You need a switch or relay that will energise one route and only one route through the crossing at a time. By judicious placement of detectors ahead of each arm of the crossing, you can automate this, but you will have to install mechanical or electrical interlocking as well. Automated or not, extra sets of contacts will provide stopping (safety) sections, and interlocked signals as well. IOW, you could make this crossing a showpiece of signalling technology... ;-) HTH -- Wolf 'Just because it's true doesn't mean it's the right answer.'