Reverse Loop Implementation

Hello, fellow railroaders. I feel silly asking this as I am an EE by profession but can anyone with access to a 1950s era American Flyer s-gauge instruction manual explain why the hookup for a single reverse-loop using a manual DPDT switch (not a reverse loop relay) apparently has to be more complicated than required? In addition to a track switch (turnout) it requires six track insulating pins and presumably three track terminals. I understand how it operates in this manner but, in addition to a DPDT switch, why not just make use of the two-train option on the turnout and a single insulated track section? Thanks for your time and comment. Sincerely,
John Wood (Code 5550) e-mail: snipped-for-privacy@itd.nrl.navy.mil Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337

On Aug 22, 7:05 am, snipped-for-privacy@itd.nrl.navy.mil (J. B. Wood) wrote:
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J. B. Wood wrote:
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That AF manual presumably applies to 2-rail track. For such track, you need only one additonal DPDT switch, and four insulating track pins.
I haven't seen the AF manual you refer to, so I don't understand how the reversing loops would need six insulating pins, etc. I suspect the designers thought they had to insulate the turnout as well, but I don't see why they would want to do that.
As you know, you need no special wiring for a reverse loop with 3-rail track.

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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.
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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.
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Wolf Kirchmeir wrote:
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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,

John,
J. B. Wood wrote:
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<snip> Well, if you're an EE, let me lean on *you*: I've been on and off looking around for a simple white noise circuit.
Why? Because I took the $20 sound car apart, and the circuit looks more complicated than it needs to be, and I'd like a schematic so I can just build half a dozen (hopefully for less than $20/pop to put in my tenders behind my steam engines, of course.
mark "painting and making a brush for the axle's the easy part"

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

David Nebenzahl wrote:
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All the ones I found seemed to be digital, and went on about white and pink noise generators. Got any links, or even an ASCII-art circuit diagram?
mark

On 8/26/2008 6:29 PM mark spake thus:
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.
Most of my links seem to have evaporated somehow. I did find this one:
http://www.musicfromouterspace.com/analogsynth/rayspinknoise.html
Here, Q1 is used as a the noise source as I described; notice how the collector is clipped off. The rest of it is just a filter network and amplifier.

David Nebenzahl wrote:
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Ok, I've never studied electronics - the times I've built anything, it's follow the directions. I still don't know why I would prefer pink to white noise for a chuff-chuff. Also, the link you sent left me somewhat confused - it looked like two separate circuits.
Any thoughts on this link? <http://www.ciphersbyritter.com/NOISE/NOISRC.HTM .
mark

mark wrote: [...]
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"White noise" is a mix of pretty well the full range of audible frequencies. It so happens that the sound of steam escaping from a small chamber and expanding into the atmosphere is pretty close to white noise. Boost the bass a bit, and you have the snd of a larger engine. Etc.
HTH

On 8/28/2008 5:44 PM mark spake thus:
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That's basically the same thing, but a lot simpler. Heck, build it and try it out. Parts can't cost more than $5-8.
That one, by the way, works the same way, by reverse-biasing a semiconductor (here a zener diode instead of a transistor). What happens, to oversimplify a bit, is that the junction "breaks down" in a very jagged way (if one graphs it), producing a lot of noise.

David Nebenzahl wrote:
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Thanks, that's muchly appreciated. And if I buy a package of the parts, I'll have what I was looking for. Now if I could only find my round tuit.....
mark

On Tue, 26 Aug 2008 17:17:43 +1200, David Nebenzahl
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A 1.5 volt GOW bulb replacing the speaker on an old but working transistor radio will give a visually random output, depending on the type of radio station you tune into. (Hip-hop actually has a use!) (Wagner requires the volume to be turned down)
Greg.P.

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Every Grain-Of-Wheat (GOW) bulb I've ever seen has been rated at 12-14 volts. Grain-Of-Rice (GOR) bulbs, on the other hand, are 1.5 volters.
Unless they've changed the terminology and I just didn't notice?
-Pete

On 8/30/2008 5:00 PM Greg.Procter spake thus regarding random noise generators:
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That's actually a pretty good way to do it, but unless you happen to have an old transistor radio around the house somewhere, those things are pretty hard to come by. I haven't seen one in years. (You could actually use any kind of radio, like a clock radio.)