I saw this turnout frog assembly on the side of the road at a crossing. I read about 'Spring Loaded Turnouts' before but have never seen one and I am assuming this is one. Does anyone know how they work and is it adaptable (and practical?) to HO scale turnouts?
-Bob
Life is what happens while you are making other plans!
It looks like this is a high-speed frog that opens and closes with the switch points. A spring switch is different -- it spring-loads the points so they normally stay in a particular (normal) position. A train going through the points in the facing direction will always go through the normal route (although in unusual situations it's possible to override the spring setting). A train going through the swiltch trailing in the reverse direction will, using the weight of the cars pressing against the spring-loaded point, go thgrough the switch without derailing. It avoids the need to stop and drop a trainman to throw the switch, for instance, at one end of an economy CTC controlled siding that doesn't have a remote switch machine.
You could theoretically do this on a model if you could fiddle with the spring loading so it would work. It might be better to use a detection circuit to throw the switch with a switch machine, which could give you he same effect without the need to experiment or fiddle with the spring strength.
John called the part accurately. It's a sprung high-speed frog, while the OP is talking about a switch that functions with spring-loaded points.
In the smaller scales, including HO, these can be iffy. There's just too much variance in car weights, etc to get them to work reliably in general service.
Where I have seen them with some success is on traction layouts. There, the trolleys usually are heavy enough to work the springing reliably and are usually close enough in weight that setting the spring up gets you close enough in the ball park to work.
Otherwise, trying to run a long train of various cars through one can be pretty dicey stuff.
Mike Lehman
Urbana, IL
An Atlas Snap Switch already works like one. The fiber (plastic, nylon, whatever it actually is) pin that comes out of the snap switch machine and connects to the throwbar already springs when something goes through it from the wrong direction. We use them on an automated logging line on our museums' model railroad. We have very little trouble with them.
The closed frog in the photos is designed to be forced open by passing wheel flanges - note the large can-like spring housings. Making one that will work in HO would be iffy, since the wheel loadings are so low. In any smaller scale I'd consider it the impossible dream.
As for spring switches, I have built them in HO and they work reliably. The normally closed point is continuous almost to the frog, and spiked for only about 1/3 of its length. Flanges approaching trailing point can force it open unless the car is SERIOUSLY under weight. In the netherworld, I build them like single point traction switches. For visible track I'm leaning toward using ordinary points held in the normal position by a very light free-hanging weight. Some experimentation will be required before I arrive at a final format.
Chuck (Modeling Central Japan in September, 1964)
Movable Point Frogs have been around since the early 1900s. The main reason for their use is to avoid excessive wear on the point itself especially in early times when steel alloys weren't developed that would stand up to the heavier loads and higher speeds and frog replacement was costly due to having the track out of service on a busy line.
http://en.wikipedia.org/wiki/Swingnose_crossing
More interesting reading here:
Here is a drawing of a very similar design to the one you show in your photo.
I have seen movable point frogs that were actuated by rodding connected to the points and in some cases actuated by a dedicated switch motor.
Spring switches are an entirely different concept, mainly used for operational efficiency whereby a crew member does not have to manually throw the points (switch) and trains can run through from either trailing route. They are usually indicated in the timetable and also by a [SS] sign near the switch. An engineer HAS to be aware not to stop and back while any part of his/her train is over a SS for obvious reasons.
I have also seen "run through" switches that are not spring switches but the points will throw over and stay in that position until either manually thrown or a train approaches from the other leg. Even the switch lamp or target will move automatically when the points throw.
Hope this helps... Ed
Thanks guys, I think I will pass on the HO adaptation and use the electonic version to throw the turnout if entered from a closed direction.
I found this (prototype) at a crossing on a little used industrial siding and it is near a turnout, but didn't make any sense as to why it would be used here. Maybe the RR just dumped it here for short term storage (don't think anyone could steal it!).
Tru-Scale track offered turnouts with moveable frogs, and there was an article some years ago - mid-'70s or earlier - in MR on scratchbuilding a moveable frog turnout.On an earlier layout, I built one (my first attempt at scratchbuilding a turnout) and it performed flawlessly. It was curved, and at least a #11 or #12 - very long and built in-place to suit a particular track situation. I powered it with a Fulgurex motor-driven switch machine. I had intended to take it with me when we sold that house, but the new owner asked if I could leave the layout, and since that was the only really good feature of the layout, I left it intact.Perhaps I'll build some new ones on my recent layout extension, so thanks for bringing up this reminder of it.
Wayne
The Elements of Railway Engineering by Prof Wm Raymond (rev Riggs and Sadler; 1937) says that movable point frogs are used in slip switches; where the crossing angle is less than about 8 degrees; and for crossings on curves. The book also shows drawings of something called a Wharton Safety Switch which involved lifting the wheels so that the flange would travel over the main line rail. Not likely that anyone has built one of those in HO.
Dave Nelson
gmpullman Movable Point Frogs have been around since the early 1900s. The main reason for their use is to avoid excessive wear on the point itself especially in early times when steel alloys weren't developed that would stand up to the heavier loads and higher speeds and frog replacement was costly due to having the track out of service on a busy line. http://en.wikipedia.org/wiki/Swingnose_crossing More interesting reading here: Here is a drawing of a very similar design to the one you show in your photo. I have seen movable point frogs that were actuated by rodding connected to the points and in some cases actuated by a dedicated switch motor. Spring switches ar an entirely different concept mainly used for operational efficiency whereby a crew member does not have to manually throw the points (switch) and trains can run through from either trailing route. They are usually indicated in the timetable and also by a [SS] sign near the switch. An engineer HAS to be aware not to stop and back while any part of his/her train is over a SS for obvious reasons. I have also seen "run through" switches that are not spring switches but the points will throw over and stay in that position until either manually thrown or a train approaches from the other leg. Even the switch lamp or target will move automatically when the points throw. Hope this helps... Ed
Spring switches ar an entirely different concept mainly used for operational efficiency whereby a crew member does not have to manually throw the points (switch) and trains can run through from either trailing route. They are usually indicated in the timetable and also by a [SS] sign near the switch. An engineer HAS to be aware not to stop and back while any part of his/her train is over a SS for obvious reasons.
The moveable point frog and the spring-rail frog (pictured) are not the same thing. With the spring-rail frog, the frog point doesn't move. The wing rail does when the wheel flange passes through it.
Jeff
tomikawaTT The closed frog in the photos is designed to be forced open by passing wheel flanges - note the large can-like spring housings. Making one that will work in HO would be iffy, since the wheel loadings are so low. In any smaller scale I'd consider it the impossible dream. As for spring switches, I have built them in HO and they work reliably. The normally closed point is continuous almost to the frog, and spiked for only about 1/3 of its length. Flanges approaching trailing point can force it open unless the car is SERIOUSLY under weight. In the netherworld, I build them like single point traction switches. For visible track I'm leaning toward using ordinary points held in the normal position by a very light free-hanging weight. Some experimentation will be required before I arrive at a final format. Chuck (Modeling Central Japan in September, 1964)
I have accidently gone through an EZ track switch with it lined in the opposite direction. However, all of my rolling will push the points aside with ease. The only issue is if I don't realize the switch is lined incorrectly and the reverse direction when the train is on the switch. If the spring and/or mechanism is weak, then you can easily have a spring switches in HO scale. Just be careful.
Kato's HO unitrack switches work as spring switches, if you set them to be non-power routing. (You move a screw on the bottom the turnout from one receptacle to the other, just takes a minute.) I use them on my layout all the time with no problem. It makes switching moves a lot easier, because you don't have to throw the turnouts as often.