Fiddle Yard 'Throat' On Curve

[Harlequin]

1 hour ago, Ian J. said:

Using Peco Code 83 #7 turnouts looks about right (thanks for the suggestion):

 

:

 

I'm not sure how I'd design boards to fit under this though. I'm thinking a custom designed laser cut curved plywood board/frame under each (up and down) fan, such that they would match up perfectly on the inside of the outer fan, and the outside of the inner fan.

 

That looks pretty good. The only thing that strikes me is that the arrangement of the turnouts means that some of the storage loops are much longer than others and the inner routes have to traverse many more turnouts than the outer routes.

 

Those things may not be problems for you but you could even things out by making the fans have more of a branching tree structure. That might also create a natural gap in the fans where you could locate a baseboard join.

 

BTW: If the storage loops will represent terminus stations where the trains stand for a while and then run back through the scene in the opposite direction the trains need to be able to crossover. So you need crossovers, ideally outside the loop points fans, but not in the scenic area. For complete flexibility a pair of facing and trailing crossovers at both ends allow you to store a trains in any loop and extract it from any loop in either direction - but that takes a lot of space!

 

[Sol]

I have seen a lot of turnouts across joins & I even did one.

 

[Sol]

And it was seeing this

http://www.brma.org.au/BRMA Galleries/British/SA Layout - 1141 - Wellingford and Bakewell Bridge Railway/SA - 1141 - Wellingford and Bakewell Bridge Railway - More Information/SA - 1141 - Wellingford and Bakewell Bridge Railway - TCH.html

 

that inspired me to do that turnout on the liftup

[DCB]

Looks like you either have a monolithic near triangle with 5ft  and 4ft  short sides  or an awkward mosaic of small boards to keep below 4ft.   I have done a doodle....   Many people will tell you that many tracks across a joint wont work but our layout has about 9 tracks across the end of a lifting flap and it gives very little trouble.   

A good woodworker can create curved baseboards with curved ply sides, I can't I hide the mess with a hardboard fascia.   However I have used 12mm ply with minimal bracing in the past and I don't see why it wouldn't work here, there may need to be a sub structure but it shouldn't be beyond the bodging ability of your average modeller with a power saw and a tape measure.

[Ian J.]

That's a good way of splitting the boards up David, I like it 

 

@Harlequin I'm happy with the turnout arrangement as it keeps all the curves to a reasonably consistent curvature, and will hopefully allow smoother running overall. Also, for the extra length sidings due to the added curve, such things as long trains of short wheelbase wagons could fit where they might not fit in the straight sections. Long carriages are a no-no of course, as there wouldn't be sufficient clearance from the adjacent tracks.

 

@Sol I modelled a shed (I still have the incomplete boards) where I cut across a number of turnouts. It's OK, but not something I would want to ever do again if at all possible. Also, one can't cut across a point just anywhere, we obviously have to avoid the blade area. I think David's board arrangement in his post above is likely to be the one I work with.

Edited October 5, 2019 by Ian J.

[Robert Stokes]

OK, I understand now. I had assumed that it would be a permanent fitting in a room or shed - for the sole reason that it's what I'm doing.

 

Robert

[Harlequin]

31 minutes ago, Ian J. said:

That's a good way of splitting the boards up David, I like it 

 

@Harlequin I'm happy with the turnout arrangement as it keeps all the curves to a reasonably consistent curvature, and will hopefully allow smoother running overall. Also, for the extra length sidings due to the added curve, such things as long trains of short wheelbase wagons could fit where they might not fit in the straight sections. Long carriages are a no-no of course, as there wouldn't be sufficient clearance from the adjacent tracks.

 

@Sol I modelled a shed (I still have the incomplete boards) where I cut across a number of turnouts. It's OK, but not something I would want to ever do again if at all possible. Also, one can't cut across a point just anywhere, we obviously have to avoid the blade area. I think David's board arrangement in his post above is likely to be the one I work with.

 

If you have wagons standing on the long curves can carriages get past them??? If not then the curves might not be usable as storage space at all! (At least not without very careful scheduling.)

 

If you could open up the spacing on the curves then the loops would be easier to use because you'd know that everything can pass everything safely.

 

Edited October 5, 2019 by Harlequin

[Ian J.]

4 minutes ago, Harlequin said:

 

If you have wagons standing on the long curves can carriages get past them??? If not then the curves might not be usable as storage space at all! (At least not without very careful scheduling.)

 

 

If you could open up the spacing on the curves then the loops would be easier to use becasue you'd know that everything can pass everything safely.

 

 

I think I'd have to settle for careful scheduling and storage line use. However, as I work with the plans I will see if I can open up the curves a little and not compromise the running consistency and minimum radius requirements.

[Harlequin]

I've just measured the inner and outer radii of the Code 83 curved turnout (from Peco's PDF template) and they are:

Outer = 60in

Inner = 28in

 

(Those values are for the actual curved parts of the turnout, i.e. excluding the short straight section before the tips of the point blades.)

 

This is a bit of a surprise because it means that the radii are exactly the same as the equivalent Code 75 part!

 

[The Johnster]

Fiddle yard roads, straight or curved, need enough room between them to get your fingers between stock should it need to be lifted out; if this is done stock on adjacent roads should clear.

 

 When you are laying the track, before you finally fix it, take your longest vehicle and the one with the longest end throw/overhang, and tape felt tip markers to the centre and the end corners.  Then push the vehicle around the curves so that the markers draw lines on the baseboard.  If any lines intersect away from junctions, you have discovered a fouling point and need to reposition the track. 

[Harlequin]

On 01/10/2019 at 15:52, Pete the Elaner said:

Referring to the above plan by Harlequin:

Storage loop 1 & 2 only properly serve the up line & 3,4 & the branch sidings only properly serve the down. Any train run into the fiddle yard on the down can cross over to be stored in the up sidings but there are only the 2 of these.

This seems to be a very popular configuration but I find it inflexible.

I routed my running lines outside of the storage lines. I can run any train out of the yard onto either up or down, so for my WCML 1990s layout, I can get away with 1 HST, 1 Mk3 set & 1 Mk2 set running in either direction on the fast lines sharing the same 3 storage lines. I actually have 4 storage lines so can use the 4th for a unit or the cobbler set.

The only downside to this is that the fiddle yard needs to be slightly shorter because the up/down lines need to share a common entry line...but I can still fit a full length HST on a 15' layout.

 

Hi @Pete the Elaner,

 

Sorry, I realised that I didn't read your post "properly" before... (Ha ha, oh dear).

 

So you'd have something like a turnout on the outer circuit feeding a single slip on the inner and then into the loop points fan. That would be very space efficient, and as you point out, very flexible in terms of entry and exit directions.

 

Another advantage of your scheme is that trains running on the main circuits are less likely to interfere with any manual fiddling that might be going on in the storage loops.

 

The only potential downside is that trains entering or leaving the outer circuit have to cross the inner and so might affect operations on the inner. Is that at all a problem in your experience?

 

Edited October 5, 2019 by Harlequin

[Ian J.]

2 hours ago, Harlequin said:

I've just measured the inner and outer radii of the Code 83 curved turnout (from Peco's PDF template) and they are:

Outer = 60in

Inner = 28in

 

(Those values are for the actual curved parts of the turnout, i.e. excluding the short straight section before the tips of the point blades.)

 

This is a bit of a surprise because it means that the radii are exactly the same as the equivalent Code 75 part!

 

 

Interesting. Anyrail might have incorrect geometry then, as I think the code 75 curved turnouts on it are tighter than the code 83, by at least a couple of inches.

[Hitchin Junction]

You might want to check out Central Valley in the USA. They offer a wide range of inexpensive turnouts that are curvable to your own radius requirements.  www.cvmw.com.

 

Tim

[Dungrange]

4 hours ago, Harlequin said:

I've just measured the inner and outer radii of the Code 83 curved turnout (from Peco's PDF template) and they are:

Outer = 60in

Inner = 28in

 

(Those values are for the actual curved parts of the turnout, i.e. excluding the short straight section before the tips of the point blades.)

 

This is a bit of a surprise because it means that the radii are exactly the same as the equivalent Code 75 part!

 

 

That's interesting, although the diverging or inner curve is never going to be a constant curve, since you have a combination of the radius of the switch, the radius of the closure rails and the angle of the Vee.  The Code 83 range has a V angle of 1:7, whereas for the code 75 range it's around 1:4.5.  This means that the substitution radius of the Code 83 range is greater than the substitution radius of the code 75 range.  That is, if you were to join around 30 turnouts Code 75 turnouts to form a circle, you'd have a circle of circa 30" radius, whereas if you were to do the same with the Code 83 range, you'd have a circle with a radius of around 3'.  The radius through the switch should be about the same for both turnouts and what you are stating is that the radius through the closure rails is also the same, which means that the more generous geometry of the Code 83 range is effectively due entirely to the more acute crossing angle and therefore shorter length of the 28" radius in the closure rail. 

[Dungrange]

1 hour ago, Ian J. said:

Interesting. Anyrail might have incorrect geometry then, as I think the code 75 curved turnouts on it are tighter than the code 83, by at least a couple of inches.

 

I don't think that there is anything wrong with the geometry in Anyrail.  The image below shows from left to right; a Peco Code 83 #7 right hand curved turnout; a Peco Code 100 Streamline right hand curved turnout; and a Peco Code 100 left hand curved turnout sat on top of a Peco Code 83 #7 Left hand curved turnout.  This is just to show that the Code 83 geometry definitely has a smoother diverging alignment due to having a larger substitution radius.

[Harlequin]

Small correction: On re-examining, I make the inner curve radius 30in.

 

[Ian J.]

Seeing the pics of code 75 and code 83 alongside, makes me wonder what the check rail gap is for code 83...?

[Sol]

40 minutes ago, Ian J. said:

Seeing the pics of code 75 and code 83 alongside, makes me wonder what the check rail gap is for code 83...?

Possibly close to these 

https://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-3.2_2010.05.08.pdf

[Hitchin Junction]

12 hours ago, Dungrange said:

 

I don't think that there is anything wrong with the geometry in Anyrail.  The image below shows from left to right; a Peco Code 83 #7 right hand curved turnout; a Peco Code 100 Streamline right hand curved turnout; and a Peco Code 100 left hand curved turnout sat on top of a Peco Code 83 #7 Left hand curved turnout.  This is just to show that the Code 83 geometry definitely has a smoother diverging alignment due to having a larger substitution radius.

 

 

Peco code 83 follows the USA (NMRA RP12 model version) turnout geometry. All the crossing vee sections are straight and have 1:5, 1;6 1;7 1:8 etc. vee crossing angles of your choice.  Not radii. Ditto for all other USA turnout manufacturers.

 

Tim

[Harlequin]

4 hours ago, Hitchin Junction said:

 

Peco code 83 follows the USA (NMRA RP12 model version) turnout geometry. All the crossing vee sections are straight and have 1:5, 1;6 1;7 1:8 etc. vee crossing angles of your choice.  Not radii. Ditto for all other USA turnout manufacturers.

 

Tim

Note that Dungrange specifically said "substitution radius".

 

The code 83 curved turnout in question definitely has curved rails from the tip of the frog/vee to the end of the turnout - at least in the Peco PDF template, which is in vector form and so can be analysed in a drawing program.

 

[Ian J.]

8 hours ago, Sol said:

Possibly close to these 

https://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-3.2_2010.05.08.pdf

 

Thanks. If set to those standards, that's about a 1.1mm gap, which should be ok for me.

[Dungrange]

5 hours ago, Hitchin Junction said:

Peco code 83 follows the USA (NMRA RP12 model version) turnout geometry. All the crossing vee sections are straight and have 1:5, 1:6, 1:7, 1:8 etc. vee crossing angles of your choice.  Not radii. Ditto for all other USA turnout manufacturers.

 

Yes, that's correct and it should be the same for UK track, but I agree that for many turnouts it isn't.   As I said previously, the substitution radius of the diverging or inner curve is not a constant radius.  The radius through the switch will be determined by the radius of the outer curve (ie 60") and the section through the common crossing should be straight - the length of that straight being determined by the crossing angle.   That therefore means that the radius of the closure rails (between the switch and the common crossing) must be less than the overall substitution radius.

 

Harlequin has indicated that the radius of the closure rails is about 30" for the Code 83 #7 turnout and 28" for the Code 75 / Code 100 Streamline turnout.  I've not tried measuring these myself, but placing one turnout on top of the other, I can see that the radii are very similar.  Both of these would sound about right for turnouts that have substitution radii of around 36" and 30" respectively.

[Dungrange]

1 hour ago, Harlequin said:

Note that Dungrange specifically said "substitution radius".

 

The code 83 curved turnout in question definitely has curved rails from the tip of the frog/vee to the end of the turnout - at least in the Peco PDF template, which is in vector form and so can be analysed in a drawing program.

 

 

The actual turnout also has a distinct curve between the frog and the end of the turnout - it's not just the .pdf.  I'd estimate that the straight section through the common crossing on the #7 is very short - somewhere in the region of 21 mm.  I'd say it was straight from approximately 5 mm before the knuckle, through the flangeway to approximately 5 mm past the tip of the vee.  It then starts to curve again within the wing rail.   It probably doesn't do that in the prototype, where I think it should be straight beyond the end of the wing rail, but these are the sort of compromises that we need to accept to avoid excessively long turnouts, which most of us don't have space for.

[Hitchin Junction]

USA prototype turnouts have always had standardised straight vee crossings that were manufactured off site and dropped into place when the turnout was laid. Even for curved turnouts, where the track went back to curved past the crossing. But curved turnouts are the rare exception in the USA anyway.

 

Tim

 

 

[davefrk]

I appreciate you're wanting to used RTL pointwork but have you considered building points to suit. I had the same problem with my layout Wharfeside, I wanted the longest siding space for a few long trains and two or three short trains per siding so the only answer is pointwork on the curve. Okay in EM I was going to have to build the points anyway but this has proved to be very successful.

 

Minimum radius 4ft with approx 7ft on the outer road. Six 'kick back'sidings at each end to reverse trains into, the outer roads each side are the though running roads and no problems have occurred that haven't been due to wagon wheels being out of gauge, now all sorted.

 

Dave.