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 Post subject: A "2-frog" slip switch.
PostPosted: Mon Apr 21, 2014 4:17 pm 

Joined: Tue Sep 02, 2008 2:31 pm
Posts: 33
There are actually two types of slip switches in the world. FastTracks has one design I call the "four frog" design, which also has 8 points. That is there are two proper frogs at each end of the switch, but there are also two gaps in the middle of the switch forming frogs of sorts where the wheels are unsupported. If you take a straight path through the switch with a single axle you will find 4 places where a wheel is unsupported.

There exists a second type of double slip, I call it the "two frog" slip. I found an illusive good picture here: (Click on the "200dpi jpeg" link for a bit better view)

Note that there are no frogs in the middle, rather, four more points. This switch has 2 frogs and 12 points! The result though is that a axle going through this switch will only find it's wheels unsupported twice. These are supposed to be less prone to derailments, at least at some crossing angles.

My question is, is something like this feasible to build? I don't think detached points would be possible in that short of a span, so I believe it would require rail thin enough to bend (code 40, maybe code 55 in N). I believe it would also make the electrical situation a bit more complex just from looking at it. I ask though because I would very much like to have the aesthetics of this particular style for a prominent location.

What say ye experts?

PostPosted: Tue Apr 22, 2014 8:43 am 
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Joined: Sat Aug 13, 2005 10:48 am
Posts: 365
Location: East Texas - USA
Moving center points are common and required for double slips #8 and longer. Even FastTracks does this for their HO #8 DS. I've done moving center points double slips for #5, #6 and #7 sizes as well as #8, #10, #11, and #12.
For N scale, it would be difficult to have hinged moving points for the shorter sizes (they are really short). Using a light rail that flexes may be a good approach.


-ed mccamey-
NMRA Standards and Conformance Department
PROTO & FINE Scale Coordinator
I estimate I have about 5 pounds of coupler springs somewhere in the vicinity of my workbench.

PostPosted: Tue Apr 22, 2014 10:46 am 

Joined: Tue Sep 02, 2008 2:31 pm
Posts: 33
Ah, so it appears I didn't check enough of the track library! I see that the HO #8 and O #8 have this layout. I read the slip instructions and saw no mention of inner points (I think technically they may be a "moveable frog") so I didn't think any of the templates had it.

I also dug up some old links (thanks google), here's a guy who built his own in HO:

In the process I also found some drawings including a Caltrain #9 with moveable frogs and a MetroLink #8 and #10 with cast center frogs (are those self guarding frogs?). This site also has PRR Standard Trackwork Plans which includes single and double slips from #6 to #20, all of which have points and no frogs in the middle.

I'm guessing that the prototype would not have used anything smaller than a #8, perhaps even a #10. At least for ordinary switches my understanding is no railroad allows smaller than a #8 today, and most want at least a #10 even for their own yards. Given slips are likely to be used with very long passenger cars, it seems unlikely there would be an exception.

Currently the N double slip is shown in a #6 only, so I'm thinking if I want to make more than one I'd want to ask them for a #8, basically a shrunk down version of the HO #8 with a moveable frog.

I may try building one without a jig to test feasibility. Maybe I can beg for a tie template for a #8 to start? :D

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