Has Anybody Made a Movable Frog Turnout?

[narrowminded]

Per a request I've just added #14 Frog machining and soldering fixtures to my list of turnout fixtures.  Easy now with the batch of similar fixtures so may as well have this one, too.  A quick check of the NMRA standards and then Fast Tracks tools show that they both stop at #12's.  There may be a reason.   It's not likely to be a standard offering but maybe a custom.

Long switches bring their own set of concerns with long, floppy rails but I don't have the experience yet to really know how bad it will be to work with them.  I may be overly concerned.   But the real question of this topic lies in the frog gaps continually getting longer between the frog point and the closure rail as the frog numbers go up and this may be a concern.  It's aggravated by our scale models using much larger flanges, hence flangeway clearances, therefore increasing the point gaps for any given size much more than the prototypes.   The way I'm making my frog and point rails with the webs fully supported at the ends should allow for the narrowest points therefore the smallest gaps possible but they still continue to get larger as the frog number goes up.  What has crossed my mind is, has anybody ever made movable frog points in N scale?  I'm aware of them in prototype but not up close and personal, like what frog size might be the conventional size to start considering movable points.   Quick search attempts in scale or in 1:1 haven't yielded much on this specific info.  Any experience or specific knowledge would be helpful.

[Maletrain]

You could also search on "swingnose crossing", for example: https://en.wikipedia.org/wiki/Swingnose_crossing .  And, there appears to be more than one approach: http://www.rail-fastener.com/railway-frog.html .  Some move the frog, some move one or both wing rails, and some use a riser block to fill the space where the wheel could drop. 

I looked at some drawings that I got since I sent you copies of what I had at the time, and I am having some difficulty with the B&O nomenclature.  There is a lot of stuff about "spring frogs" but nothing about "movable frogs".  And, there is a lot of content about "rigid crossings" and "movable point crossings" along with a lot of content on both switches and crossings at angles.  It is hard to be sure what applies to what.

There is a graph that shows a demarcation line between "rigid crossings" and "movable point crossings" which has some frog numbers on it.  The graph coordinates are ""Angle between tangents at intersections of center lines of tracks" vs "degree of curvature" from the tangent, I guess at the point of crossing.  All I can get from this that "rigid crossings" up to #6 frogs are good for curvature up to 6 degrees, except that "rigid crossings" up to #7 frogs are good in yards and terminals when there is no curvature (?).  But, it is not exactly clear to me how this does or does not apply to movable frog turnouts.

There is also a table for "Frog Heal and Toe Blocks" that specifies "rigid" or "spring" for frogs, with "rigid" shown for frog numbers up to #20 and "spring" for #8, #10 and #12.  That does not seem compatible with the graph, so I am pretty sure that I don't understand how the B&O did things.  I could try asking the B&O discussion group, if you think having actual prototype info would help you.

But, are you really trying to imitate prototype, or just trying to use an idea from the prototype to make your model work smoothly.  If it is really model functionality that is your concern, then prototype practice is probably not that helpful, because our model flanges are so much wider and our model treads are so much wider.

The drawings that I have of "spring frogs" do show the frogs to one side or the other, but say nothing about the throw mechanism.  Maybe there isn't one for the frogs in those drawings, and the frogs just spring back after being pushed to the other side. 

I am thinking it could really be a lot easier to do on our models.  A pivot pin could be put through a hole in the frog assembly back near the diverging end, and a throw hole could be put in some thick part of the frog toward its point, so that a wire from a Tortoise or servo could make it move.  I am thinking that it would be much easier to use separate throw mechanisms for the points and frog, rather than try to design a gizmo that made the throws of both happen the proper amounts with one actuator.  If somebody wants to spend a lot of effort saving one actuator, let that person get an article in MR on how to do it.

[robert3985]

Per a request I've just added #14 Frog machining and soldering fixtures to my list of turnout fixtures.  Easy now with the batch of similar fixtures so may as well have this one, too.  A quick check of the NMRA standards and then Fast Tracks tools show that they both stop at #12's.  There may be a reason.   It's not likely to be a standard offering but maybe a custom.

Long switches bring their own set of concerns with long, floppy rails but I don't have the experience yet to really know how bad it will be to work with them.  I may be overly concerned.   But the real question of this topic lies in the frog gaps continually getting longer between the frog point and the closure rail as the frog numbers go up and this may be a concern.  It's aggravated by our scale models using much larger flanges, hence flangeway clearances, therefore increasing the point gaps for any given size much more than the prototypes.   The way I'm making my frog and point rails with the webs fully supported at the ends should allow for the narrowest points therefore the smallest gaps possible but they still continue to get larger as the frog number goes up.  What has crossed my mind is, has anybody ever made movable frog points in N scale?  I'm aware of them in prototype but not up close and personal, like what frog size might be the conventional size to start considering movable points.   Quick search attempts in scale or in 1:1 haven't yielded much on this specific info.  Any experience or specific knowledge would be helpful.

@narrowminded  Mark, I've built a few #12's and didn't have any problems with their length.  However, looking at prototype drawings of #14's, I notice that instead of the usual two throwbars between the point rails, my diagram shows there's four throwbars.  I assume this is to control the "long & floppy" rails of the point rails, which are (if I remember correctly) 33' long.  I'd use PCB tie material to do this if I were building #14's, and you might consider this, but would necessitate hinges at the point rail heels that also allow slippage such as a shortened rail joiner or something similar to Proto87Store's point rail hinges, but definitely NOT the elegantly simple notch hinges we've discussed.

As for moveable point frogs, I don't have any drawings of points that need to be thrown, but I have some drawings of what are called "spring point frogs" that involve moveable points, but are spring loaded and activated by the wheels' flanges.  Are you talking about frog points that need a switch machine or frog points that are spring loaded??

Anyway...looking forward to your progress with the turnouts, as well as your Code 55 mainline tie base.  I'll be starting on my big Wilhemina Pass/Devils Slide LDE in about two, maybe three months and I would love to use your tie bases, and possibly your turnouts for my track! 

Cheerio!
Bob Gilmore

[narrowminded]

There is a graph that shows a demarcation line between "rigid crossings" and "movable point crossings" which has some frog numbers on it.  The graph coordinates are ""Angle between tangents at intersections of center lines of tracks" vs "degree of curvature" from the tangent, I guess at the point of crossing.  All I can get from this that "rigid crossings" up to #6 frogs are good for curvature up to 6 degrees, except that "rigid crossings" up to #7 frogs are good in yards and terminals when there is no curvature (?).  But, it is not exactly clear to me how this does or does not apply to movable frog turnouts.

There is also a table for "Frog Heal and Toe Blocks" that specifies "rigid" or "spring" for frogs, with "rigid" shown for frog numbers up to #20 and "spring" for #8, #10 and #12.  That does not seem compatible with the graph, so I am pretty sure that I don't understand how the B&O did things.  I could try asking the B&O discussion group, if you think having actual prototype info would help you.

Possibly and by asking the same basic question that I asked here.  My interest in doing this is to make a smooth running turnout and fear that the larger frog numbers with their ever widening frog point gap where the wheels want to drop naturally will be an issue that, just as on the prototype, would be helped by the movable frog.  My best understanding is that they are used, even on low numbered frogs, to reduce the pounding damage to the frog point, especially useful in busy yards, and would also be used on higher speed turnouts, especially helpful on the larger frog numbers.  I suspect that for my purposes the number where I might want to start using such a thing, or maybe offering the option, would be around a #10 or #12 and up.  The #14 frog that I just drew up is what brought this forward for me realizing that the gap will become quite large on this number frog.  It made me especially curious at what point did this become common on prototypes.

But, are you really trying to imitate prototype, or just trying to use an idea from the prototype to make your model work smoothly.  If it is really model functionality that is your concern, then prototype practice is probably not that helpful, because our model flanges are so much wider and our model treads are so much wider.

That's exactly where I think this could be helpful, eliminating that frog point gap, but I would want to try to be somewhere in a reasonable range in the offerings.  Because of the wider flangeways and all related dimensions the model turnout will encounter the wider frog point gaps much sooner than a prototype.  I'm not too worried about the mechanics of accomplishing the moving point but it would need extra precise parts and some related cost.  No details yet as this just surfaced on my radar.

[narrowminded]

As for moveable point frogs, I don't have any drawings of points that need to be thrown, but I have some drawings of what are called "spring point frogs" that involve moveable points, but are spring loaded and activated by the wheels' flanges.  Are you talking about frog points that need a switch machine or frog points that are spring loaded??

Anyway...looking forward to your progress with the turnouts, as well as your Code 55 mainline tie base.  I'll be starting on my big Wilhemina Pass/Devils Slide LDE in about two, maybe three months and I would love to use your tie bases, and possibly your turnouts for my track! 

Cheerio!
Bob Gilmore

Yes Bob, I'm thinking of the prototypes that use a separate machine to operate the frog although I'm not sure that I would need to do that.  I just don't know yet as this has just now arrived on my radar.  It was pondering building a #14 or larger that brought this up.  For my purposes I would envision this only for a long mainline turnout although spring rigs and such do show up in smaller sizes for protecting the frogs on heavily used track.

The timing on your addition should be good and I really hope to be able to supply what you need.  I'm sure you'll make it look good!

[Maletrain]

...The timing on your addition should be good and I really hope to be able to supply what you need.  I'm sure you'll make it look good!

Yep, I can't think of a better advertisement for a new product that to have pictures of it incorporated into one of Bob's layouts. 

[draskouasshat]

Weve installed new no.24 turnouts with swingnose frogs. I haven't seb first hand any smaller switches with them yet
Drasko

[John]

There was an article in one of the model railroad magazines years ago .. I don't know which one though ..

[narrowminded]

Weve installed new no.24 turnouts with swingnose frogs. I haven't seb first hand any smaller switches with them yet
Drasko

That's excellent, exactly the kind of thing I'm looking for.   Thanks.

[Doug G.]

Tru-Scale made movable frog switches in HO where the gap was totally eliminated by the frog wings being brought against the frog rails. Lima made the same thing in N scale in the early years. There is a pivot about halfway between the points and frog.

I guess I'm not sure I'm describing exactly what you mean. Personally, I think it is a superior design for models where the flanges are grossly oversize. and the vast majority of derailments are right in the frog area.

Doug

[peteski]

Tru-Scale made movable frog switches in HO where the gap was totally eliminated by the frog wings being brought against the frog rails. Lima made the same thing in N scale in the early years. There is a pivot about halfway between the points and frog.

Unprototypical but it worked really well.

[narrowminded]

Tru-Scale made movable frog switches in HO where the gap was totally eliminated by the frog wings being brought against the frog rails. Lima made the same thing in N scale in the early years. There is a pivot about halfway between the points and frog.

I guess I'm not sure I'm describing exactly what you mean. Personally, I think it is a superior design for models where the flanges are grossly oversize. and the vast majority of derailments are right in the frog area.

Doug

The prototype style that I'm thinking about has the frog point only moving side to side with the motion of the switch point rails.  It does eliminate the frog point gap.  I'm comfortable that I can make the turnout work as intended without the moving frog just by making the assembly precisely but there is a natural drop at that point even when precisely executed and I thought that, just maybe, some might be interested in a prototype style of moving frog that eliminated that drop.  Maybe just a cool factor.  

I will know better if this is an issue worth some effort after I've actually built a few of these longer turnouts.  So far I haven't worked with any this long and doubt I'll have a layout that can utilize these long lengths but some might.  After building a few long ones I may decide it's just overkill to worry about this.