Okay, will mock it up when have some benchwork up... Thanks.
7j43k I recommend you build a couple of test curves to confirm things.
I recommend you build a couple of test curves to confirm things.
Rich
Alton Junction
On tangent track, you'll have half an inch between two cars with two inch track centers.
On a 24" radius curve, a 60' car will overhang INWARDS by a quarter inch. Overhanging of cars OUTWARD will be less, maybe an eighth of an inch. Probably less.
So. You should be able to pull it off. With at least an eighth of an inch to spare.
I say it will work.
But.
If I'm wrong, who loses here?
Ed
Okay, quick question. Designing a switching layout. Two places will have parallel tracks on curves. Thinking of 22 and 24-inch radius curves. HO scale, 4 axle locomotives and max car size is 60 ft. Good?
selector That NMRA gauge is just a guide.
That NMRA gauge is just a guide.
I'll second Sheldon's Rivarossi H-8. My 2005/6 version came with two cabs, believe it or not. The one installed had the shorter cab roof overhang of the two, the extension reaching back to the tender. They're fragile, and I broke the optional cab's extension. Had I installed it, it's side clearance intrusion into track spacing would have been quite serious in my estimation. The nose of this beast is bad enough, and the engineer's injector overflow catches on stuff near the tracks, things like shrubs or lineside details. Beware!
While I have your attention, look up! What trips me with overhead clearances are pantographs, the chimneys on the odd caboose, crane booms....don't just look to side clearances. That NMRA gauge is just a guide.
SeeYou190 7j43k When I said that a Big Boy would overhang outwards on a 37" curve by 1/2" (using up ALL possible clearance at 2" centers), that was based on a model locomotive with a non-swiveling rear engine. Ed, I have compared two articulated locomotives, a Bowser 4-6-6-4, and a Bachmann 2-8-8-2. They have different designs. The Bowser has a rigid rear engine (prototypical), and the Bachmann has both engines able to rotate (non-prototypical). I know a lot of this is apples-to-oranges, but this is what I have noted. In prototype design, the boiler front seems to overhang a lot more on tight radius curves. With both engines rotating, boiler overhang is less, but cab overhang is increased. Overall, both seemed to require a relatively equal side clearance. Both of these locomotives would negotiate a 22 inch radius curve, and both looked completely ridiculous doing it. -Kevin
7j43k When I said that a Big Boy would overhang outwards on a 37" curve by 1/2" (using up ALL possible clearance at 2" centers), that was based on a model locomotive with a non-swiveling rear engine.
Ed, I have compared two articulated locomotives, a Bowser 4-6-6-4, and a Bachmann 2-8-8-2. They have different designs. The Bowser has a rigid rear engine (prototypical), and the Bachmann has both engines able to rotate (non-prototypical).
I know a lot of this is apples-to-oranges, but this is what I have noted.
In prototype design, the boiler front seems to overhang a lot more on tight radius curves. With both engines rotating, boiler overhang is less, but cab overhang is increased.
Overall, both seemed to require a relatively equal side clearance.
Both of these locomotives would negotiate a 22 inch radius curve, and both looked completely ridiculous doing it.
-Kevin
I completely agree with that assessment and will add that as the radius increases, the double swivel designs have less front overhang, while the fact that the rear engine swivels becomes much less noticable.
So while it may not be prototypical, the double swivel design is a great appearance compromise even for those with large curves. It makes your large curves look larger.
All of my articulated locos are modern plastic/die cast double swivel designs and look fine on 36" radius and above.
The EM-1 is the biggest overhang offender on my roster.
The others:
Spectrum 2-6-6-2's
Proto 2-8-8-2's (now 2-8-8-0's)
BLI N&W A 2-6-6-4's
Rivarossi C&O H8 2-6-6-6 (#2 overhang offender)
Sheldon
I'll note that my overhang dimension for the Big Boy was based on drawings of the engine. With the normal slop in HO models, I wouldn't be shocked to find more. Or even less.
I'll mention that 4-12-2's don't have this problem!
7j43kWhen I said that a Big Boy would overhang outwards on a 37" curve by 1/2" (using up ALL possible clearance at 2" centers), that was based on a model locomotive with a non-swiveling rear engine.
Living the dream.
When I said that a Big Boy would overhang outwards on a 37" curve by 1/2" (using up ALL possible clearance at 2" centers), that was based on a model locomotive with a non-swiveling rear engine.
ATLANTIC CENTRALBut it has some serious overhang at that radius........ It just barely stays in the 2" track center window at 36" radius.
Yep, that is why the operational restriction to the outer hidden loop only.
As far as I know, this is the only piece of equipment I have with an operational consideration like this.
SeeYou190 7j43k SeeYou190 My 2-8-8-4 will need to be restricted to the outermost of my hidden return tracks. The cab overhang is so excessive on the outside of the curve that this is necessary. -Kevin Mmmm. Me like! Good! (Sorry about letting my inner kid appear--it happens.) Ed I am amazed by the Bachmann 2-8-8-4. It runs like a fine watch, looks good, and will negotiate a 22 inch radius curve. -Kevin
7j43k SeeYou190 My 2-8-8-4 will need to be restricted to the outermost of my hidden return tracks. The cab overhang is so excessive on the outside of the curve that this is necessary. -Kevin Mmmm. Me like! Good! (Sorry about letting my inner kid appear--it happens.) Ed
SeeYou190 My 2-8-8-4 will need to be restricted to the outermost of my hidden return tracks. The cab overhang is so excessive on the outside of the curve that this is necessary. -Kevin
My 2-8-8-4 will need to be restricted to the outermost of my hidden return tracks. The cab overhang is so excessive on the outside of the curve that this is necessary.
Mmmm. Me like! Good!
(Sorry about letting my inner kid appear--it happens.)
I am amazed by the Bachmann 2-8-8-4. It runs like a fine watch, looks good, and will negotiate a 22 inch radius curve.
But it has some serious overhang at that radius........
It just barely stays in the 2" track center window at 36" radius.
SeeYou190This potential contact needs to be avoided because it will happen at the most fragile parts of detailed train cars. The corners and the center.
I think Ed (and indirectly Mike) are correct about the relative unimportance of many factors on curved yard track spacing, including that nonprototypical articulated-locomotive outward overhang will likely be 'controlling'.
I'd be interested to know if the 'test' 86' boxcar has more inward interference than typical passenger cars -- likewise if 89' flats are in the same general category.
At least some of the changes to the NMRA 'gage' will be AAR plate changes over the years, with plate H now being common. Do any modern Plate H models have more serious momentary-contact inside overhang than the old 86' boxes?
Here's Gritton's useful 'unified' plate reference again, through plate H:
https://gritton.org/greg/rail/docs/clearance/AAR_plates_with_UIC.gif
Note the 'kinematic' adjustments, but more importantly the AAR recommended clearance for Plate H.
OvermodI didn't go into that detail as I was only concerned with potential momentary contact
This potential contact needs to be avoided because it will happen at the most fragile parts of detailed train cars. The corners and the center.
Overmod All this palaver is fun but I don't think it's getting the OP much closer to what he was asking to know...
All this palaver is fun but I don't think it's getting the OP much closer to what he was asking to know...
Here's a bit more on the subject:
On a 38.5 inch radius curve, the tightest in the yard, a 65' long freight car (the potentially most troublesome) will project an approximate additional 1/8" inwards. It will not project outwards that much. Since there is 2" between track centers, and a freight car is about 1.5" wide, there is 1/2" available for clearance WITHOUT accounting for increased curve overhang.
1/8" is dramatically less than 1/2", so I say clearance in the curves in the yard for the type of cars and locomotives that will be in it is more than adequate.
IF projection outward in the curve were to also be 1/8" (which it will not), and two of these cars were passing, there would still be 1/4" clearance.
Note that no road engines nor passenger cars will be in this yard.
Now, the arrival/departure tracks might be different. I see a 37" and a 39". If an articulated is planned on being operated there, overhang outwards for the boiler front should be considered. And perhaps outward overhang on each end of a 4-8-4. Articulateds could be limited to the outer track, and likely things would be fine there.
I also note that two of the three A/D tracks don't have much straight near the switches, perhaps generating difficulties adding/removing engines and cabooses.
It would be wise if the OP were to do some overhang measurements and calculations for the "biggest" motive power and passenger cars on specified radii before locking things in.
I took a few minutes and found that the outward swing of a Big Boy's front would be a half inch on that 37" radius A/D track, so running such an engine on that track would not work out if there were cars on the next track. In fact, if articulateds are contemplated on the layout, some double-checking all over might be in order. For the A/D tracks, it might make it a fun challenge to limit articulateds to the outer of the three tracks.
Except for 89' flats, passenger cars are the big challenge on INWARD overhang. On a 37" curve, they will come inwards about a quarter inch. And less outwards.
Looks like the biggie on curves will be articulateds.
7j43kOvermod, I trust you are getting my point.
I didn't go into that detail as I was only concerned with potential momentary contact of a (potentially wobbly) car with a standing adjacent train with its now-fixed overhangs. I think by the time we get to Unstoppable-grade levels of tilt, we're no longer in the realm of advice to the OP on reasonable track spacing for his purposes. Even modeling of negative cant deficiency in passenger models (which Hornby did, and I presume Rapido did with their APT model) is on the esoteric side for typical modeling concerns -- although not for Amtrak on the NEC north of New Haven...
The other point in question is the wobble. Yes, good models shouldn't wobble, but a good three-point side-bearing arrangement implies that the 'stiff' truck can prevent any roll of the carbody including when the 'far end' leads into what may be sharp curves and its angular momentum change is accommodated via the center pin of the 'tiltable' truck. Long practical evidence with good model railroading practice certainly indicates this doesn't rise to the level of a chronic derailment cause, but in some cases, especially with sprung or 'articulating' sideframes, it might prove to increase the effective upper-outer 'critical contact radius' enough to matter if the situation were already critical.
selector You were right on the money, Rich. In a world governed by 'likes', I had merely hoped to offer reinforcement by posting my own version of the same idea.
You were right on the money, Rich. In a world governed by 'likes', I had merely hoped to offer reinforcement by posting my own version of the same idea.
hgodlingThey are assuming you have a big boy pulling 85' passenger cars so that is probably excessive.
Lastspikemike Centrifugal force would act on trains travelling on both the inside track and the outside track so the only effect of that would be the delta resulting frim the differing radii. Pull the other one.
Centrifugal force would act on trains travelling on both the inside track and the outside track so the only effect of that would be the delta resulting frim the differing radii. Pull the other one.
Nope. Sorry.
You are wrong. Wronger than Overmod said.
The whole point of bringing up centrifugal force here is that the train tips at a certain angle. If it DIDN'T tip, what's the point?
For trains 1.5" wide, on parallel tracks at 2" centers, when the tipping angle from vertical is 42 degrees, they will touch. I just did an experimental setup to find that number.
You, of course, will say that this is silly, among other reasons because they'd have derailed already. Yes. Quite true.
But:
My POINT is that they WERE 1/2" apart when they were stopped. To get to the above silly point, they have to move closer and closer as they tip further and further. So, although they won't touch for sure until 42 degrees, the possibility that they MIGHT touch increases, too.
Let's see what happens when we close the track centers down to 1.6". Standing still, they don't touch. They're separated by .1" But if they were to tip from centrifugal force, both going at the same speed, that .1" would DISAPPEAR at 21 degrees (experimental result again) from the vertical. And, as pointed out above, the possibility starts increasing at earlier tip angles.
This effect is in addition to the difference of lean angle caused by differing radii.
Overmod, I trust you are getting my point. Note that the trains are traveling at the same speed.
richhotrain selector To the OP, I suggest deriving empirical data. You have certain items of rolling stock. They gotta work. Right? So, find out if they'll work down to a certain limit. Get out a sheet of plywood or drywall, fix some track radii..nested to duplicate the conditions in your yard...and run a good sampling of your locomotives and rolling stock around them to see what happens. You'll find an empirical 'lower limit' above which you'll know to craft your curved yard ladders, and you'll construct them with confidence knowing your product will be satisfactory. Agreed, and this is why I wrote my earlier response to the OP. richhotrain Years ago, I got some good advice from my LHS guys about spacing of tracks on curves. They recommended that I buy a pair of 85' boxcars and test them on actual track to be sure. I wouldn't blindly rely on the advice of others unless they can say with certainty that 2" on center spacing for 36" radius tracks will work based upon their actual experience. If this were my layout, I would use 2 1/2" spacing on curves and, since it is the yard, I would step down the radius on curved tracks to something like 32" radius. In fact, that is exactly what I did on my old layout where I installed a yard on a curve on my layout. Don't act on the advice of others unless they speak from personal experience. Try it out for yourself by putting down some track and running some cars. You are building a yard on a curve as I did on my layout. Spacing that works on straight mainline tracks is not the same as spacing on a curve, epecially in a yard where you are more likely to need to access individual cars. Rich
selector To the OP, I suggest deriving empirical data. You have certain items of rolling stock. They gotta work. Right? So, find out if they'll work down to a certain limit. Get out a sheet of plywood or drywall, fix some track radii..nested to duplicate the conditions in your yard...and run a good sampling of your locomotives and rolling stock around them to see what happens. You'll find an empirical 'lower limit' above which you'll know to craft your curved yard ladders, and you'll construct them with confidence knowing your product will be satisfactory.
To the OP, I suggest deriving empirical data. You have certain items of rolling stock. They gotta work. Right? So, find out if they'll work down to a certain limit. Get out a sheet of plywood or drywall, fix some track radii..nested to duplicate the conditions in your yard...and run a good sampling of your locomotives and rolling stock around them to see what happens. You'll find an empirical 'lower limit' above which you'll know to craft your curved yard ladders, and you'll construct them with confidence knowing your product will be satisfactory.
Agreed, and this is why I wrote my earlier response to the OP.
richhotrain Years ago, I got some good advice from my LHS guys about spacing of tracks on curves. They recommended that I buy a pair of 85' boxcars and test them on actual track to be sure. I wouldn't blindly rely on the advice of others unless they can say with certainty that 2" on center spacing for 36" radius tracks will work based upon their actual experience. If this were my layout, I would use 2 1/2" spacing on curves and, since it is the yard, I would step down the radius on curved tracks to something like 32" radius. In fact, that is exactly what I did on my old layout where I installed a yard on a curve on my layout.
Years ago, I got some good advice from my LHS guys about spacing of tracks on curves. They recommended that I buy a pair of 85' boxcars and test them on actual track to be sure. I wouldn't blindly rely on the advice of others unless they can say with certainty that 2" on center spacing for 36" radius tracks will work based upon their actual experience.
If this were my layout, I would use 2 1/2" spacing on curves and, since it is the yard, I would step down the radius on curved tracks to something like 32" radius. In fact, that is exactly what I did on my old layout where I installed a yard on a curve on my layout.
Don't act on the advice of others unless they speak from personal experience. Try it out for yourself by putting down some track and running some cars. You are building a yard on a curve as I did on my layout. Spacing that works on straight mainline tracks is not the same as spacing on a curve, epecially in a yard where you are more likely to need to access individual cars.
Good lord, Mike....why not read and think a bit instead of scurrying over to your keyboard at every opportunity.
There are few things sadder than when you try to help a dog and he tries to bite.
LastspikemikeCentrifugal force would act on trains travelling on both the inside track and the outside track so the only effect of that would be the delta resulting from the differing radii. Pull the other one.
As we say in skeet, PULL!
Lastspikemike To answer the OP's question indirectly the NMRA recommends wider track centres than 2" for reasons not clear to me. https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7.1_tangent_track_centers_and_clearance_diagrams_2019.01.pdf https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7.2_curved_track_centers_july_2017.pdf https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7.3_curved_track_obstacle_clearances_july_2017.pdf https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7_track_centers_and_obstacle_clearances_july_2017.pdf One wonders why the NMRA gauge is set at 2 3/16" for measuring clearances. The clearances to track centres are 2.5" minimum for a pair of parallel tangent tracks. That's 5/16" wider than the gauge!
To answer the OP's question indirectly the NMRA recommends wider track centres than 2" for reasons not clear to me.
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7.1_tangent_track_centers_and_clearance_diagrams_2019.01.pdf
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7.2_curved_track_centers_july_2017.pdf
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7.3_curved_track_obstacle_clearances_july_2017.pdf
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7_track_centers_and_obstacle_clearances_july_2017.pdf
One wonders why the NMRA gauge is set at 2 3/16" for measuring clearances. The clearances to track centres are 2.5" minimum for a pair of parallel tangent tracks. That's 5/16" wider than the gauge!
The NMRA RP actually says tanget (straight) tracks can have a spacing of 1 25/32" for cars of the "classic" era. (which fits the OP 1950s.
The 2.5" spacing is for curved tracks. This is to account for the overhangs in the corner. They are assuming you have a big boy pulling 85' passenger cars so that is probably excessive.
The standards gage is for straight tracks and is actually more for structures. Which have different clearence needs.
And again, tapered wheels and and tapered axle ends do NOT insure that the car is ALWAYS centered on the track...........
Overmod
back when I started on RR about 197? worked at Robert Young Yard in elkhart before I got on the GTW anyway some of the tracks off of the hump were off limits to people they were so close together If the cars rocked a bit they would hit I think they finally fixed them long after I was there
LastspikemikeWhatever works for any trackside obstruction has to work for passing trains. That's just geometry. Things either overlap or they don't.
PRR discovered at some point that clearances on Horse Shoe were a bit tighter than the ones used for clearance in the J1 2-10-4 design, with the result that passing engines started trying to knock parts off each other.
There were some yards in the East with so little room between tracks that there would be damage if cars on adjacent tracks had plug doors left open.
It can't matter if only one of the things is moving or both are.
Part of the fun is that the force of contact (and many of the effects) increase greatly with relative speed. At some point there might be aerodynamic effects that could induce deflection or rock.
There is an NMRA RP (RP-7.2) to provide some guidance on this. The RP assume very large locomotives and 85' rolling stock, so it is probably a bit overconcervative. They recommend around 2.5" spacing for 36" curves.
They do provide a tool to calculate the recommended spacing for your specific rolling stock.
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/curved_track_center_and_obstacle_clearance_assistant_jul_2017.html
Just playing with your rolling stock may be the easier route. However, for someone like me who is still planning and has limited rolling stock, these tools may be more helpful.
richhotrainDon't act on the advice of others unless they speak from personal experience
+1
Anyone can read my posts, copy and paste them, and then claim that they are an expert.
Unfortunately, they are using my posts, which are not a good place to start.