Here I go again.....

Re: Here I go again.....

Postby j p » Thu Jan 09, 2014 9:37 pm

Juup wrote:This is interesting information. 40km/h for EW3 and 30km/h for EW2 and 60km/h for curved station track. I guess this is all in the spirit of wanting to be prototypical in our modelling, and then with the knowledge we gain we can compromise with awareness :)

JP, can I ask some questions?

What are these numbers based on? Is it a general rule for real railroads that for curved station track the maximum speed is around 60km/h, for a long turnout 40 and for a short turnout 30?

Or is it a calculation based on radius alone? If so, does that mean the speed limit for curved track of radius 100cm (i.e. the same curve as EW3 turnout) is 40km/h as well?

Or Is the calculation different for turnouts because turnout blades require more caution than simple curved track?

Last question, extending the logic of the speed limits you have provided, what would be the speed limit for a train running through Tillig's 12 degree Wye turnout (the longer one where both directions have a radius of 200cm)?

They say it takes about 10000 hours to become an expert at something. I am clearly not at 10000 hours yet - LOL.

Juup


No, it is not a general rule. It is based on the geometry. If you tried to run a real train through such a short turnout at a high speed, the centrifugal force would derail it. You could see a clear demostration of this in the news not long time ago, about a commuter train in N.Y. (that was a normal track curve though)

"Normal" turnouts have 40 km/h speed to curve. EW3 is shorter than that, but we shorten the lengths somehow on the model railroad.
"Slim" turnouts have 60 or even 80 km/h to curve. TT-Filigran makes the "slim" turnouts for 60 km/h, it is turnout nr. 14 if I remember correctly. High speed trains as TGV, Eurostar, ICE, Shinkansen etc. have special turnouts which allow hugher speed to curve. The length of such a turnout would be more than a typical station on a TT scale layout.
The reason for the different maximum speed on turnouts and on track curves is very simple. The turnout is always placed flat while the track curve has a cant/superelevation which compensates for (some part of) the centrifugal force.

You can find the figures for mph and US turnouts, but the physics is the same.
I tried to google the turnout speed and geometry and found this:
http://www.tillier.net/stuff/hsr/TM-2.1.3-Directive-Dwgs-TurnoutsAndStationTracks-100409.pdf
nr. 9 is 20 mph
nr. 11 is 25 mph
nr. 15 is 35 mph
nr. 20 is 50 mph


Tillig's 12 degree Wye turnout would be a 40 km/h turnout too, in both directions. Maybe our German friends can find DR or DB standards for the turnouts?

The correct speed for the main line curves on this layout would be something like 30 km/h, but up to 60 km/h is accpetable I think. Running BTTB or Tillig's models at full power (=Shinkansen speed) is wrong, even on the straight track.

I use km/h speed of the prototype for explanation. Divide it by 120 to get it to the model speed.
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Re: Here I go again.....

Postby ctxmf74 » Thu Jan 09, 2014 11:30 pm

"The cool thing about the removable backdrop is that I can remove it permanently :) It will be one of the last things I do anyway so maybe by the time I get to it, I won't care for it."

Another neat thing about making it removable is you could then convert the rear tracks of the staging to an industrial area if you ever decide you want to run some freight trains.Factories along the wall are easy to build and don't need much layout depth.....DaveB
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Re: Here I go again.....

Postby ConducTTor » Thu Jan 09, 2014 11:50 pm

ctxmf74 wrote:Another neat thing about making it removable is you could then convert the rear tracks of the staging to an industrial area if you ever decide you want to run some freight trains.Factories along the wall are easy to build and don't need much layout depth.....DaveB


Yes! :wave:
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Re: Here I go again.....

Postby ConducTTor » Fri Jan 10, 2014 1:43 am

I've made a few changes. I've changed the far left station turnout to a right curve to allow for larger diameter mainlines on the left side of the station. Also I've reworked some of the track on the right side so the main lines have a straight shot across the station. Also I removed two staging tracks.

If I have a door towards the middle of one of the sides of the room, the left side tracks will have a lift out piece (door area in the first image).

If I end up with a door along one of the long walls or close to one of the corners (the most likely scenario), there will be no lift out - instead the track will look like the second image.

Any more thoughts/ideas?
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Re: Here I go again.....

Postby ctxmf74 » Fri Jan 10, 2014 2:09 am

"If I end up with a door along one of the long walls or close to one of the corners (the most likely scenario), there will be no lift out - instead the track will look like the second image"

That should cover all the bases. If you build modular you can even fit the parts into totally differently shaped rooms by building some new connecting sections. Do you plan to start on this design in it's present space now? Maybe build the station side first and see what your situation is after working on it for a while?....DaveB
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Re: Here I go again.....

Postby ConducTTor » Fri Jan 10, 2014 3:03 am

ctxmf74 wrote:Do you plan to start on this design in it's present space now?


Not until after the NMRA National in Cleveland - too much to get ready for that.

ctxmf74 wrote:Maybe build the station side first and see what your situation is after working on it for a while?....DaveB


Exactly what I'm planning on doing :thumbup:
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Re: Here I go again.....

Postby LVG1 » Fri Jan 10, 2014 10:10 am

j p wrote:The reason for the different maximum speed on turnouts and on track curves is very simple. The turnout is always placed flat while the track curve has a cant/superelevation which compensates for (some part of) the centrifugal force.


Oh, I think that's not that simple.
On the one hand, the radiuses of regular tracks are usually clearly larger than those of turnouts. That's the opposite of your logic. The reason is the lack of space in stations and the expenses of longer turnouts. That's why the safety margin is lower on turnouts.
On the other hand, superelevation increases the thread of vehicles overturning to the inside of the curve—especially in long, heavy trains and uphill, respectively. That's why not all curved tracks are superelevated.

Besides velocity, radius and superelevation, also the gauge and the height and excentric position of the center of mass of the vehicles is important for the calculation of the speed limit in a curve. That's why Switzerland allows higher speeds on turnouts for trains with a low center of mass ([almost] only passenger trains; designated as class "R" in Swiss rules).

In Germany, the speed limit is calculated in a way that the centrifugal forces won't derail a train driving twice as fast as permitted with the highest permitted centre of mass. But I don't know if this is the rule for turnouts or for the open road.

j p wrote:You can find the figures for mph and US turnouts, but the physics is the same.
I tried to google the turnout speed and geometry and found this:
http://www.tillier.net/stuff/hsr/TM-2.1.3-Directive-Dwgs-TurnoutsAndStationTracks-100409.pdf
nr. 9 is 20 mph
nr. 11 is 25 mph
nr. 15 is 35 mph
nr. 20 is 50 mph


What do the numbers say about the geometry?
I'm not aware of any designation standard of this kind used in Germany.

j p wrote:Tillig's 12 degree Wye turnout would be a 40 km/h turnout too, in both directions. Maybe our German friends can find DR or DB standards for the turnouts?


There are two ways of addressing turnouts in Germany—one for those who use turnouts and one for those who build turnouts.

Those who use turnouts don't care about geometry. They only want to know how fast a turnout can be passed.
So operational staff describes the various kinds of turnouts by the top speed on the diverging track. Three types are common in Germany. Most turnouts are 40 km/h-(25 mph)- and 60 km/h-(37 mph)-turnouts, respectively. 100 km/h-(62 mph)-turnouts are also relatively common on fast main lines. Other types are extremely rare.
In Switzerland the usual types are 40 km/h (25 mph), 60 km/h (37 mph; for class "R": 65 km/h [40 mph]) and 90 km/h (56 mph; for class "R": 95 km/h [59 mph]).

Track building staff name turnouts by a fraction. This fraction describes the ratio between the two cathetuses of a triangle which the diverging track is the hypotenuse of.
So a 1/6 turnout has a diverging angle of exactly 9.462°. A 1/9 turnout is 6.340°.
Unortunately, I don't know much about the geometry of prototype turnouts. So I can't tell which geometry belongs to which top speed.
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Re: Here I go again.....

Postby krokodil » Fri Jan 10, 2014 1:12 pm

It is not just the question of the geometry, but also the locks on the turnout (how are they fixed in each position). For high speed turnouts they install special lock elements, while the super high speed turnouts ( over 100 km/h ) recently they prefer moving frog turnouts, in each positions the rails does not have any gaps in route.
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Re: Here I go again.....

Postby Juup » Fri Jan 10, 2014 2:01 pm

Thank you JP, LVG1 and Krokodil for your very informative responses! This helps me look at my own track plan from an entirely new perspective.

Can you tell me if I understand all of it correctly?

Speed on a TT model layout is usefully calculated as real world speed divided by 120. So an IC train doing 120km/h in real life would on our layout be doing 1km/h. An ICE at ‘full blast’ may be closer to 2km/h. Having returned to model railroading after many years, I have noticed how today’s models are calibrated to run closer to prototypical speeds. The N scale Fleishmann locos of my youth were way too fast!! Also an old BTTB runs faster than a new Tillig loco. Would be good fun to incorporate speed sensors of some kind at key places on a layout :)

Speed limit is a function of a) radius, b) super-elevation, and c) centre of gravity of a train (with passenger trains having lower centres of gravity). Different countries combine these factors slightly differently. Speed through turnouts may in addition be affected by the mechanical design (Krokodil’s point). Oh, easement into curves might affects things as well, right?

Due to space and financial restrictions, stations will have shorter turnouts. Hence, the required slow-down for a train navigating a turn-out in a station is likely to be greater than using a (usually longer in the prototype) turnout outside of station areas.

So, even though all our turnouts on our model railroad, whether in or outside of stations, may be e.g. EW3 (because TT Filligran is too expensive and we may lack the space), we can achieve some realism by:
a) having a higher speed limit for turnouts outside of stations (because in the prototype these turnouts would be longer), and lower speed limits for turnouts in station areas stations (because in the prototype these turnouts would be shorter). Modelling DB or other continental railroads the speed limit for station turnouts may usefully be 40km/h (for a NA layout 20-35mph), and outside of stations 60-100km/h depending on the kind of line (NA layout 50mph). Trains travelling ‘straight through’ turnouts can ignore these speed limits.

b) try to have express trains passing through a station (without stopping) do so without using the curved part of a turnout … they should be moving straight through any turnouts or else they will have to slow down quite a lot. That might be a challenge for ConducTTor to achieve … but there is always ‘compromise with awareness’ :)

Finally, this information is potentially discouraging in terms of how fast we are able to run our trains through model type curves (without turnouts). But again, we can perhaps achieve a sense of realism by specifying some kind of relationship between speed on the one hand and radius, super-elevation and centre of gravity on the other (as appropriate/possible given our particular space restrictions). For instance, one might stipulate that passenger trains (with low centre of gravity) can do 150km/h on any super-elevated curve with radius of 50cm (or 75cm or 100cm), while goods trains going through the same curve can do no more than 100km/h. Each layout can use a slightly different formula depending on the extent to which space has constrained curve radia (or is it radii?). Would that be a good approach? That would allow (the) ConducTTor to tweak a formula for his layout that allows him to run his ICE at speed through the bottom half of his layout.

About super-elevation … best to avoid or restrict where the speed limit is lower (especially where there is goods traffic) and in uphill gradients … is that about right?

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Re: Here I go again.....

Postby ctxmf74 » Fri Jan 10, 2014 2:09 pm

"So a 1/6 turnout has a diverging angle of exactly 9.462°. A 1/9 turnout is 6.340°.
Unortunately, I don't know much about the geometry of prototype turnouts. So I can't tell which geometry belongs to which top speed"

I've heard a rule of thumb is twice the frog number so a #6 would be 12 mph, #8 would be 16 mph, etc. but that chart up above looks like they used about 2.25 to 2.50 times the frog number.....DaveB
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