Walthers states that their 20"/24" curved turnout has a #6.5 frog. I figure it to be a #10.5.
i’m working on laying out a curved turnout and I come up with larger frog numbers than the commercial turnouts of the same sizes. Do commercial turnouts use stock frogs?
Model track manufacturers seem to use their own terminology when labeling curved turnouts. If you are measuring the ratio of the distance to width, is that how you came up with 10.5 for your Walthers #6.5?
Using commercial turnouts, we pretty much have to make a “best-fit” for whatever are available on the market; either that or custom build your own using FastTracks.
Look at your drawing. You show the whole turnout being more than 15 inches long. It is not. If you get your hands on the turnout, which I highly recommend, you’ll find that it’s the radius they lie about rather than the frog.
I agree with Carl, I worked up a Peco curved turnout on my CAD a few years ago and couldn’t come up with their specs as printed. I’m glad I bought the turnouts before I did the drawing otherwise they wouldn’t have fit my CAD driven track work.
My guess is that in the case of curved turnouts, the term ‘substitution radius’ has more application and meaning because of the twin curved routes, something a conventional turnout won’t offer the user. You can’t practically insert a true NMRA-compliant #6 turnout into a 44" radius curve without a compromise at the turnout, a kink if you will, but that’s not true for a curved turnout with the same frog number. At least, it ‘should be’ true for a curved turnout with the appropriate twin curved paths.
I don’t think that is correct for most (if not all) commercial curved turnouts. There is still a small amount of difference from a true curve radius owing to the points and frog. Much closer ̶t̶h̶a̶t̶ than a straight turnout – but not exactly a circular curve.
Byron, don’t you have that ackwards? A curved turnout will be a much better fit into a curve than a standard NMRA type. The diverging route past the frog is straight for an inch or more. If one chooses to mangle the turnout and clip the rails almost immediately after the frog, then you could add curved rails from that point on. Personally, I’d just use a curved turnout.
i don’t believe this is suggesting that such a turnout can fit cleaning into a curve of the same radius
i do believe it is indicating what the tightest radius is for purpose of determining if a locomotive can handle the turnout. Locomotives have maximum track curvature limits
i’m planning on laying a curved turnout. I plan on making the frog match the inner/outer curve radii, which will be tight (hence the ? about frog #).
i see no need to “straighten” the rails around the frog (which I did with other turnouts i laid). I believe the guard rail should guide the truck, maybe widen the gauge a little.
A curved turnout will fit better, but not perfectly, into a circular curve. I see that I accidentally typed “that” instead of “than”, which may have created confusion.
I suspect the reason the rails are straight while running through the frog is that the designer/builder of that switch was using an off-the-shelf frog. Which is based on two intersecting straight lines.
A custom curved frog would likely cost much more than a standard one.
Likely true, remember the number for the frog is derived from the separation per unit distance for the FROG, not the whole turnout. Curve the rails past the frog to some radius and you may get a number completely different from the frog - you need to draw straight lines from the frog to determine the frog number.
Is the frog number or angle of a frog in a curved turnout even relevant? I figured the minimum implied radius is the constraint. Implied radius of the diverging route is sort of the same issue with straight turnout but that’s traditionally explained by the frog # when talking about straight turnouts.
It may be on the prototype, in which case typical frog numbers would be puzzling to most modellers. In our hobby, though, the frog number is simply the ratio of through axis progression over the divergence at the frog point and beyond.
A #6 frog diverges one unit toward the diverging route for every six units of length the rolling item moves parallel to the main axis…the through route. Think of it as the ratio of ‘through over run’, and like the inverse of ‘rise over run’.
For curved turnouts, to me what really maters is how longer rolling stock is able to reliably operate through ether of the routes so I tend to focus on radius here. Since many seem to report the inner radius is actually somewhat smaller than the manufacturer stated radius, if I don’t want to roll my own, I try to use the largest available.
I’m using a 32 inch minimum mainline radius for my layout so apparently the reported inner radius of some curved turnouts (such as the Walthers #8) is, depending on who you ask, something like 28 or 30 inches. Some even believe the Peco #7 with it’s stated 36" radius is closer to 30 inches also.
If the above is true, then the curved inner radius is smaller than the minimum I am trying to keep to, but my guess is if I use 32 minimum except for where the turnout is, that inner curve on the curved turnout is short enough to probably not have adverse affects on any rolling stock which might have issues below 32" curves.
AFAIK, I don’t have any rolling stock that cant handle radius’s significantly lower, like 28, even 26, but thats why it’s helpful, if space allows, to use a minimum that has some built in margin for longer rolling stock over what is factory recommened.
I don’t have any Walthers Empire Builder passneger cars, but recently I read a long forum discussion started by a modeler who was asking if his 9 car EB could run reliably on his 32 inch minimum curves. Walthers apparently reports a minimum of 24" is recommended but hobbyists have found those EB passenger cars often don’t actually work well on 24 inch curves. In reality they really seem to need something like 28" radius or more, 32" being totally fine by a number of experiencial reports.
If the frog were curves at the same radius as the diverging rail in the curved turnout, then I might say that the frog ‘angle’ is the same as the diverging rate of the rails - but a curved frog wouldn;t have an ‘angle’ since it’s curved, so assigning a number to it would not be in direct comparisoon to a straight turnout - possibly how model manufacturers get away with using rather arbitrary numbers. But if the frog is straight, a true angle between two lines, then it has a number that stays the same regardless of the radius imparted to any rails on the diverging side. Too shallow a frog angle (higher number) with diverging curves that are sharper than the substitution radius of an equivalent straight turnout, or the closure rail radius of an equivalent straight turnout, would be next to pointless, as who cares if the larger rigid wheelbase loco cna negotiate the frog if it can;t negotiate the tight diverging curve? Reverse I think would be true as well, why have a #4 frog feeding 60 and 32" radius curves, if the loco can get though the curves but not the frog?
If the frogs on commercial curved turnouts are curved - unless everyone agrees where to draw intersecting straight lines, any measurement of angle and thus frog number are somewhat subjective For there to be any consistency, each manufacturer would need to agree to measure from the same points within the turnout. I think that accounts for much of the variation in listed frog numbers. And if they can;t even agree to what the diverging rail radii are, and publish unrealistic numbers, good luck reconciling it all.
