Model Forum / General / Railroads / August 2008

It might depend on where the power pack was connected.  If the power
pack feed was wired to someplace on the reverse loop itself, then yes,
you would need to isolate the turnout.  Of course, running a power pack
feed to the trackage of a reverse loop, is itself wrong, since the
rule-of-thumb is to always power turnout rails from the point end and
NOT from either of the frog ends.

Nor with an overhead powered trolley.

Note: a two-rail reverse loop shares some 'features' as a mobious strip.
This might be a good way to visualize the issues of two-rail reverse loops.

Hello, Wolf, and all.  First, my thanks for all the replies.  After
additional study of the s-gauge American Flyer (AF) track switches
(turnouts) I've concluded that the intent of the AF single reverse loop
wiring is to 1) not interrupt the current to the running train while in
the loop as the DPDT switch is thrown (this is stated in the AF manual)
and 2) by setting the "2-train" button on the turnout appropriately,
cause the train to stop in the loop short of the turnout to prevent
derailment.  This would be the case when, after throwing the DPDT
switch, the operator forgets or is late in switching the turnout to the
position required for train exit from the loop.

It's interesting to note that when wiring up the AF reverse loop relay
per AF instructions to somewhat automate the reverse loop (you still
have to manually throw the turnout) the current to the train in the loop
will be momentarily interrupted.  In this case, however, only one
insulated block section vice three (using the DPDT switch method) is
needed.  Sincerely,

On 8/25/2008 6:06 PM mark spake thus:

Ackshooly, you ought to be able to find lots of those out there in
web-land. I say that because a couple years I got a wild straw up my
butt to build a circuit to simulate a flickering fire, based on a noise
generator. It never worked you (well, at least not yet), but I did find
lots of noise-generating circuits along the way. May even still have
some links.

Hint: there are basically two types of noise generators: simple and
complicated. The simple ones are "analog" and usually use a
reverse-biased transistor as an avalanche diode (only two connections
used). The complicated ones use all kinds of logic components to
generate what is usually a pseudo-random repeating sequence. I favor the
simple ones myself. Basically all you need besides the generator is a
filter to select the frequency range you want (a capacitor or three) and
a small amplifier (one chip, like a 741).