A relatively new development in North American mainline track design (the mainline application dating from more or less from the turn of the 21st century, although street railroads used them decades before), flange bearing frog switches are on their way to becoming very common.
They make a lot of sense for their designed application - serving low-usage sidings off a fairly busy main route. The mainline goes straight thru at normal speed, unbroken rail, no frog gap to traverse; the siding (or low usage crossing route in a OWLS - one way low speed - diamond) is accessed at a low speed (FRA imposed 10mph) because the wheel is ramped up and over the mainline rail (the wheel thread actually traverses across the mainline railhead). Spiffy, and should reduce maintainence costs a lot (which in turn could mean more sidings, spurs, and diamonds which is always a plus).
So, which hardy modeler have working versions of these on their layouts/modules, particularly in HO or N scale? Or am I so completely late to the party that I just need to order a Peco SLE83666 #6 Left ElectroFrogLess switch?
in Tony Koester’s article on building a turnout scratch (MR dec '89) he suggests filling the space in between the rails of a frog with solder and using a hacksaw blade to clean the space between them. This provides some metal for the flange to ride on while crossing the rails.
He also suggests using pre-molded frogs similar to below.
I would think that you’d almost have to run fully sprung loco drivers and car trucks with heavy car weights in order to make one of these frogs operate correctly. Not everything scales down well in models.
The Union Pacific railroad is installing movable point frogs in many locations as turnouts are being added or replaced. I don’t think those flange-bearing frogs used on streetcar lines could support the weight of a diesel locomotive.
Yes, that is true. It would be a bit of challenge for several reason:
With DC/DCC, the section of the mainline rail that the jump frog crosses MUST be insulated, to prevent a short when the locomotive wheel flanges cross it as the loco heads from/to the siding. This insulated section of mainline rail probably would involve a short section of plastic replacing the mainline railhead, as a simple thin non-insulated coating would probably wear away quickly.
The prototype jump frog has a guard rail/guide rail section in the rail opposite the railhead crossing (apparently called the “curved stock rail” according to several images I found on-line). This guard rail (which is also ramped to follow the profile of the mainline crossing rail) is what keeps the axle from derailing as it skitters across the mainline - on this Railroad.net page in the middle are two images of a jump frog to give you an idea.The inner guard rail could be made of plastic, the curved stock rail ramp of a soldered thin stock. Hmm, it could be done, but I know it would be tricky to get it to work reliably, and certainly wouldn’t tolerate the infamous Rivarossi Pizza-Cutter style wheels.
However, apparently the railroads are starting to love these switches for low-speed low-usage sidings and industrial spurs off mainlines, and we’ll probably be seeing a lot more of them on the prototypes.
Gregc - not sure that Tony Koester’s frog design is relevant to this topic (After his last few columns, sometimes I wonder if Tony Koester is relevent) - that’s a regular frog configuration with solder raising the railw
Reproducing the geometry (including the humped-over switch points) would be a snap for this dyed-in-the-wool specialwork scratchbuilder. Even compensating for the wider treads and deeper-than-prototype flanges of RP25 wheels wouldn’t overly complicate the situation.
HOWEVER!!! - most model rolling stock is far too stiff to be happy on the ‘designed into the trackwork’ humps. That especially includes some model diesels with under-gearbox clearances measured in microns, and also long-wheelbase unequalized steam. If I did build one, it would be on a test module, not working main - and there would be a LOT of testing before I ever tried one on a single track main that has to handle everything on the railroad.
The prototype, with its fully-equalized rolling stock, has worked out THEIR glitches. We modelers have yet to begin.
Chuck (Modeling Central Japan in September, 1964 - with level turnouts)
IIRC, the Tru-Scale turnouts pivoted everything between the switch points and the frog point as a unit. The result was a closed frog - and a HUGE flangeway on the open side of the frog point.
To those unfamiliar, imagine a Shinohara turnout with the point pivot farther back and the closure rails integral with the points. There was another plate just ahead of the frog point, joining that end of the closure rails.
It’s still a viable, if unprototypical, way to arrange the moving parts of a turnout. What it doesn’t (and didn’t) do was lift the flanges over a solid, un-notched stock rail at the points and the frog.
Chuck (Modeling Central Japan in September, 1964 - since 1964)
I do not recall off-hand anyone having build a turnout like that where one rail is ramped up over the mainline rail. Personally, I think that it would create a lot of difficulties, particularly with engines and rolling stock due to the sharp grade up to the turnout on just one side. Generally it is advisable to keep the track as FLAT as possible to ensure electrical and mechanical reliability. I would guess that you will have electrical pickup problems going over the raised portions of the diverging route, as well as problems with freight cars derailing unless their trucks are very carefully tuned. 6-axle diesels and steam locomotives certainly will not be able to go through a model of this turnout.
As to flange bearing frog switches in general, any correctly built model turnout is flange bearing. Due to the oversize flangeways required by the over size wheel flanges on our models, there is a point when a car going through a turnout has at least one wheel completely unsupported by the rail head. For smoothe operation through the turnout, the depth of the frog is designed so that the flange on our model train car rides on the flat surface inside the frog and it keeps the car from lurching as it goes through the turnout. Cars with flanges larger than RP-25 will lurch through the turnout because the overly large flange hits the flat part inside the frog and bounces the wheel up off the head of the rail.
In that resepect, most model turnouts are flange bearing frog switches.
Take another look, Pilgrim. BOTH rails hump up at both points and frog - rather like a speed bump. The diverging route points are inverted L shapes that slide the humps on top of the straight-through running rails. The open point would be lots taller than a Kadee magnet, and there have been reports of those fouling on gear boxes.
Unless you run heritage or excursion steam, no steam loco should ever have to. This is a 21st century development.
[quote]
As to flange bearing frog switches in general, any correctly built model turnout is flange bearing. Due to the oversize flangeways required by the over size wheel flanges on our models, there is a point when a car going through a turnout has at least one wheel completely unsupported by the rail head. For smoothe operation through the turnout, the depth of the frog is designed so that the flange on our model train car rides on the flat surface inside the frog and it keeps the car from lurching as it goes through the turnout. Cars with flanges larger than RP-25 will lurch through the turnout because the overly large flange hits the flat part inside the frog and bounces the
