Do you think a GANTLET is feasible

[Big_Boy_4005]

QUOTE: Originally posted by jkerklo

Would a prototype railroad ever share rails like in the 4-rail or 5-rail diagram? Seems sharing rails would cause construction/maintenance problems.

John Kerklo
TCA 94-38455
www.Three-Rail.com

I think the answer is no John. The 4 and 5 rail versions are strictly from the 3 rail toy realm. The 6 rail version represents 2 distinct tracks interlaced, that is most true to the prototype. It is also the most compact, which is really the entire point.

[lionelsoni]

Actually, the 4-rail version has the same number of rails as a prototype gantlet, while the 6-rail version is the one that reveals the toy-train use of three rails.

[Big_Boy_4005]

QUOTE: Originally posted by lionelsoni

Actually, the 4-rail version has the same number of rails as a prototype gantlet, while the 6-rail version is the one that reveals the toy-train use of three rails.

There is another give-away with the 4 rail version Bob, but it is rather subtle. The rail spacing is equal on all 4 rails. Of course this is necessary to preserve gauge on both paths. Because of this it requires a full gauge and a half in width to construct.

The 5 rail requires 2 full gauges of width. The only space saving really comes from the clearence that would normally be found between tracks, as it is reduced to nil in this scenario.

If I was going to do this, I would go for the 4 rail version, in spite of it's slightly more complex electrical considerations. Hint, hint Dave.[swg]

[spankybird]

Elliot, I have to agree with you, I believe the 4 rail would be great for Dave to build.

[lionelsoni]

I don't think that uniform rail spacing is necessarily unprototypical. As long as the gantlet produces the needed clearance, the rails could be spaced equally. However, one could further obfuscate the dual use of the inner rails by spacing them just a little bit un-uniformly. That is, put each inner rail perhaps 1/8 inch off-center between the rails that flank it. This would create an obvious 1/4-inch difference in the spaces between railheads, which would then be about 7/16 and 11/16 instead of 9/16 each, while keeping the pickup offset tolerable.

[fjerome]

ok, i was following this pretty well until big boy made the CTT reference. i grabbed my feb/05 issue up, but can't find anything related to this. am i looking in the wrong place? abnormally dense?

dave, the 5 rail is too easy and what is the point. if you can't have some real overlap, then the situation won't be clear. go with the 4 rail.

[lionelsoni]

Daniel, let me elaborate on your relay scheme: Since the two tracks would almost certainly be powered from separate sources, each relay should also disconnect the rail that it is switching from the other relay coil before connecting it to the supply. Otherwise, any difference in supply voltages could cause both relays to operate at the same time and create a short circuit. Furthermore, each relay coil should be returned individually to the supply for the track that it is powering, or, better, both should be returned to a fixed voltage.

[Anonymous]

QUOTE: Originally posted by lionelsoni

Daniel, let me elaborate on your relay scheme: Since the two tracks would almost certainly be powered from separate sources, each relay should also disconnect the rail that it is switching from the other relay coil before connecting it to the supply. Otherwise, any difference in supply voltages could cause both relays to operate at the same time and create a short circuit. Furthermore, each relay coil should be returned individually to the supply for the track that it is powering, or, better, both should be returned to a fixed voltage.

Bob,

I did not address the case where the 2 tracks are powered by different voltages. For this case, the following can be used:

Connect the coil of the 1st relay between track 1 hot and the 1st switched rail. Connect the NO contacts of the 1st relay between the track 2 hot and the 2nd switched rail. Likewise, connect the coil of the the 2nd relay between the track 2 hot and the 2nd switched rail. Connect the NO contacts of the 2nd relay between the track 1 hot and the 1st switched rail. The frog can be isolated to avoid shorts. When a train enters the gantlet, it will ground one of the switched rails through the wheels, activate the relay and power the other switched rail for the pickup rollers.

When one relay is closed, the contacts bypass the coil of the 2nd relay, preventing both from being activated simultaneously.

Daniel Lang

[Big_Boy_4005]

QUOTE: Originally posted by fjerome

ok, i was following this pretty well until big boy made the CTT reference. i grabbed my feb/05 issue up, but can't find anything related to this. am i looking in the wrong place? abnormally dense?

dave, the 5 rail is too easy and what is the point. if you can't have some real overlap, then the situation won't be clear. go with the 4 rail.

March 05, page 77 will clear things up for you.[swg]

[Jim Duda]

Gentlemen: Seems it's a given The Professor should incorporate one into his Monster layout...c'mon Elliott, it would certainly be an attention getter - and you could document your control scheme and share it with us. Since it will be computer controlled, have the opposing trains wait for one to clear it, then send the other one over it. Are you game? Post the video on the forum for us...pretty cool stuff!

[lionelsoni]

Daniel, it seems that you have each track's center rail powered through a front contact on a relay whose coil is returned to the other track's supply. So, if the track-2 power is off, track 1 can't operate the relay to get voltage on its center rail.

However, even if you switch the relay-coil returns so that each track's relay depends on its own supply for coil and voltage to its center rail, you still have the problem that a train on track 1 with low or zero track voltage, for example, looks to the track-2 relay like a train on track 2. Relay 2 therefore picks up and tries to put track-2 voltage on the track-2 center rail, which is already grounded by the wheels of the train on track 1.

I think you need form-C contacts on each relay, so that the back contact can disconnect the center rail from the other relay before applying voltage to it.

[FJ and G]

"dave, the 5 rail is too easy and what is the point. if you can't have some real" F

---------------------------------

I was off the forum yesterday and today I see the 4-rail plan is gathering momentum. I like!

Not easier but then what would be the point? I am actually building the layout as much to learn about electronics and other things as to experiment. That is 99% of the fun!

A very innovative plan the 4 rail is, that really would have made the March CTT Trackplan page, a good plan, an even greater plan (where it crosses the bridge 4 times).

Thanks for the ideas, guys. You are on the ball.

[Big_Boy_4005]

QUOTE: Originally posted by Jim Duda

Gentlemen: Seems it's a given The Professor should incorporate one into his Monster layout...c'mon Elliott, it would certainly be an attention getter - and you could document your control scheme and share it with us. Since it will be computer controlled, have the opposing trains wait for one to clear it, then send the other one over it. Are you game? Post the video on the forum for us...pretty cool stuff!

Jim, the only problem is if I did do one of these, it would probably be inside a tunnel where nobody would see it anyway.[;)]

Speaking of video, I have to finish packing trains, as I am off to do a mall show this weekend. One of the things I will be doing with the display is some relay logic train control. The exact kind of thing required to control this track feature. I will take some video, then I have to figure out how to share it.[8D]

[spankybird]

Elliot, If you plan on sharing your video, I have found 15 to 20 seconds is about the limit for downloads. 20 seconds of video can be about 10 mgs.

So do alot of short ones.

tom

[lionelsoni]

I just got the March CTT and saw the unusual layout pictured on page 77, with two sections connected by a 4-track bridge. The layout is intended for use with only one train, which crosses the bridge once on each of the four tracks during each complete circuit; so the bridge tracks are deliberately spaced as close as possible. It looks like a gantlet waiting to happen!

One possibility is a 9-rail gantlet, similar to the 2-track 5-rail gantlet discussed here except that each pair of adjacent tracks would share a running rail, with each track having its own dedicated center rail. This could of course be done with three conventional tracks, suitably spaced, with the center track connected to the transformer so that its outside rails are connected to the outer tracks' center rails and its center rail is connected to their outside rails. The result is 9 rails, alternately connected to the two transformer terminals.

A more extreme version would use only two conventional tracks, in the same way as the 4-rail gantlet that we have discussed. The rails would be again connected alternately to two sides of a circuit; but a relay would be used to swap the connections to the transformer. Control rails on the individual tracks approaching the bridge would latch or release the relay to get the correct polarity for the rails that the train will use. A relay with three sets of form-C contacts would do the job, two to do the reversing and one to provide the latching contact.