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In lugnet.trains, Christopher Tracey writes:
> -has anyone built a wye in lego?
Unfortuanately, it can't be done without using something to create isolated
blocks. Too see the problem, note that the outside rails of the turnouts are
always connected. The inside rails are switched depending on the turnouts
position. What this means is that the 3 outside rails of the wye are each a
single electrical connection. Now, assume that the three turnouts are labeled
A, B, and C. Assume A is the connection to the mainline, and the controller.
This means that the outside rail of the AB connection is polarity P1 and the
outside rail of the connection AC is polarity P2. Now, set turnouts B and C so
they point at each other. Setting turnout B thusly, connects the inside rail
of BC to the outside rail of AB, and thus to polarity P1. Setting turnout C
thusly, connects the inside rail of BC to the outside rail of AC, or polarity
P2. There is the short! Meanwhile, the outside rail of BC will get no power at
all.
Now you, well, maybe if we never set turnouts B and C to both point at each
other. Well, then we never get a short, but you will see that both rails of AC
always get the same polarity, and thus the train will not move. Say we set
turnout A to point to B, and B to point to A, meanwhile turnout C points to B.
Turnout A's setting causes the inside rail of AB to be P2. Turnout B's setting
causes the outside rail of BC to be P2. Turnout C's setting causes the inside
rail of BC to be P2. Reverse all the turnouts and the polarity of both rails
of BC is P2.
What would be much nicer is if the turnouts also switched the power to the
outside rails. Then you could safely build a wye, but you would need an
auxilliary connection to wye section BC.
Note that because of the way the turnouts work, if you have a double ended
passing siding, you must set both turnouts to the main or to the siding in
order for one of the tracks to be isolated from power. An interesting result
of the way they work is that if you have a layout which is just a passing
siding without a loop connecting both ends (in other words, a point to point
layout), and you connect power to one end, the other end is always powered no
matter the setting of the turnouts (even if they are set opposing). This is
because the outside rails of the siding are continuous with the rails at each
end.
Frank
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Message has 1 Reply:
 | | Re: Yards
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| Frank Filz wrote: <frank's excellent description sniiped for space> Thanks for your insights... I might try to make a wye. I think we may be able to get around some of the polarity issues because we use DCC to run our layout. And as I stated in my (...) (25 years ago, 28-Apr-00, to lugnet.trains, lugnet.org.us.wamalug)
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Message is in Reply To:
| | Yards
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| I am trying to design a yard for the next WAMALUG display and I haven't come up with a decent design yet. Our previous yards were ok, but they were lacking in the function department(the switcher couldn't do anything without crossing the mainline). (...) (25 years ago, 27-Apr-00, to lugnet.trains, lugnet.org.us.wamalug)
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