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Minimum tunnel height

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Posted by BMMECNYC on Friday, February 8, 2019 3:27 PM

For a helix, I would think that you would want to add at least a finger width, maybe a bit more so you can safely extract equipment of median height in the event of a mishap.  Tunnel, maybe a bit less.

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Posted by SeeYou190 on Sunday, January 27, 2019 5:02 PM

RR_Mel
I used the HO NMRA gauge plus a ¼” for my tunnels and they look pretty good.

.

I don't use a gauge. I couple a TOFC flat and a Rivarossi observation to my 2-8-8-4 EM-1 and run it through the tunnel. If that train can make it, all my equipment will be OK.

.

-Kevin

.

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Posted by selector on Sunday, January 27, 2019 3:01 PM

railandsail

... but a few circumstances had me looking at railhead to underside of overhead roadbed material. (did that make sense? Confused)

 

It's the only way to think of it if you want to keep it simple and to avoid costly errors.

Doing a thought experiment, you imagine the highest rolling stock you have, or are thinking about purchasing, say double stacks or the stack on a steam wrecker crane, or maybe the boom's cable guide gantry.  Better yet, why not extract that item from its box and place it on rails.  Measure its lower comfortable limit for overhead clearance, and then use that to add to any roadbed and sub-roadbed thicknesses you intend to place where tracks cross over each other at disparate grades.

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Posted by ATLANTIC CENTRAL on Saturday, January 26, 2019 8:56 PM

railandsail

Tunnel Clearances

Is the true tunnel clearance measured from the railhead, or from the roadbed base line?

In our modeling we need to allow for the depth of the rail and the ties to get our existing trains thru,...and future purchases.

What brought this subject up in my mind was my checking, and rechecking that I could get some overlaping tracks (verticial ones) to fit in my helix-to-shed bridging. I was working with roadbed to roadbed dimensions, but a few circumstances had me looking at railhead to underside of overhead roadbed material. (did that make sense? Confused)

 

The NMRA has revised their standards and recommended practices, but for the most part, the clearance has not really changed - 3-1/32" above the rail head for all post 1900 modeling except for the most modern equipment.

Why is this even a question at this point in this hobby?

Here is the link again:

https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-7.1_tangent_track_centers_and_clearance_diagrams_july_2017.pdf

So obviously one needs to know what construction method they are using and add that total, subroadbed, roadbed and track, to the 3-1/32" for a rail head to rail head number for calculating grades - I use 4"...........

Sheldon 

    

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Posted by NHTX on Saturday, January 26, 2019 8:27 PM

     Fittng newer equipment through older tunnels results in some interesting solutions to the problem out there in 12"=1' land.  A lot of tunnels had their floors lowered to accomodate the taller cars.  This caused track to ramp down into and up, out of the tunnels.  Other railroads  cut triangular notches high and wide enough to permit the passage of Plate F equipment through old, arch roofed tunnels.  In some cases it looks like it was done by ramming  instead of cutting away the excess material.  The latter fix would be interesting on a model railroad.

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Posted by dehusman on Saturday, January 26, 2019 2:26 PM

railandsail
Is the true tunnel clearance measured from the railhead, or from the roadbed base line?

Railhead, i.e. top of the rail.

The clearance is determined by AAR "plates" which give the clearance diagrams.  They have evolved over the years.

Here are diagrams of the plates:

http://www.icrr.net/plates.htm

They apply to any structure (bridge, tunnel, building, etc).

Earlier railroads had tighter clearances, but they were widened as the railroads bought bigger equipment.

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Posted by mbinsewi on Saturday, January 26, 2019 1:10 PM

railandsail
, but a few circumstances had me looking at railhead to underside of overhead roadbed material.

I never built a helix, but if I were, that measurement makes more sense to me, as that is the actual area you need for your highest rail cars, and some space in case you have to get your fingers in there.

Mike.

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Posted by railandsail on Saturday, January 26, 2019 1:06 PM

Tunnel Clearances

Is the true tunnel clearance measured from the railhead, or from the roadbed base line?

In our modeling we need to allow for the depth of the rail and the ties to get our existing trains thru,...and future purchases.

What brought this subject up in my mind was my checking, and rechecking that I could get some overlaping tracks (verticial ones) to fit in my helix-to-shed bridging. I was working with roadbed to roadbed dimensions, but a few circumstances had me looking at railhead to underside of overhead roadbed material. (did that make sense? Confused)

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Posted by RR_Mel on Friday, June 2, 2017 8:25 AM

DSchmitt

I don't think, there are three different different NMRA gauges, but the modrler can make their own from the information on Atlantic Central's link. 

 

That’s good info.  Thanks for unscrewing my head.  Sometimes new stuff really does a number on my 80 year old brain.  On my tunnel portals I added a ¼” clearance to the HO Mark IV NMRA “Classic” Standards Gauge.   As stated earlier better safe than sorry.
 
Good topic!  Great responses!
 
 
 
 
 
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Posted by rogerhensley on Friday, June 2, 2017 5:28 AM

Perhaps this will help explain how railroads set tunnel clearances. http://madisonrails.railfan.net/eci/gauge.html

 

Roger Hensley
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Posted by DSchmitt on Friday, June 2, 2017 2:31 AM

I don't think, there are three different different NMRA gauges, but the modrler can make their own from the information on Atlantic Central's link. 

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Posted by RR_Mel on Thursday, June 1, 2017 8:25 PM

gmpullman

 

 

I believe there are three NMRA gauges in HO. Old Time, Classic and Modern.

http://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-7_2012.02.pdf

There have been several revisions over the years. Mark II, III, IV and now IV-b.

Regards, Ed

 

The gauge I have must be a Classic NMRA HO for standards Gauge, H measures 3.031”/76.97mm.  It is labeled Mark IV, I also have a older HO gauge that doesn’t have a label and it is the same size as the Mark IV.  I can’t find anything but the HO Mark IV online.  Can someone clue me in to the difference size Standards Gauges.
 
 
 
 
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Posted by ATLANTIC CENTRAL on Thursday, June 1, 2017 8:12 PM

    

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Posted by riogrande5761 on Thursday, June 1, 2017 7:37 PM

Do all the NMRA gauges say explicitly what they are providing vertical clearance for and do they guarantee to clear all models?

I think it still makes the most sense to use your tallest model as a guage and add a margin onto that.  Better safe that sorry.

 

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by gmpullman on Thursday, June 1, 2017 1:48 PM

riogrande5761
That would be my guess too.  I would not rely on the NMRA guage if you have modern tall freight cars like hi cube double stacks. 

I believe there are three NMRA gauges in HO. Old Time, Classic and Modern.

http://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-7_2012.02.pdf

There have been several revisions over the years. Mark II, III, IV and now IV-b.

Regards, Ed

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Posted by riogrande5761 on Thursday, June 1, 2017 1:39 PM

ACY
 
ATSFGuy

No dome cars north of Washington and around New York because of these issues.

Tom

In once case, a western road ran eastern low profile domes.  The D&RGW bought 3 dome observation cars with squashed domes which were original designed and ordered for eastern clearances by the C&O RR.

I'm pretty sure that the standards gauge dimensions predate double stacks. 

That would be my guess too.  I would not rely on the NMRA guage if you have modern tall freight cars like hi cube double stacks.  Even though I have basically backdated to pre-double stack era, I did design my clearances to allow double stacks to run.

IMO, it's best to take your tallest rolling stock and use that as a guage, and then add at least a 1/4 inch onto that.

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Posted by ACY Tom on Tuesday, May 30, 2017 9:27 PM

ATSFGuy

No dome cars north of Washington and around New York because of these issues.

 

 

For the most part, that's true. The B&O operated dome cars that had a special low profile, unlike the taller cars used on the Western roads. Walthers makes them. The low profile was due to height restrictions in a number of tunnels on the B&O's route. The tops of the B&O cars were pretty close to the catenary on the approach to Washington Union Station, so all persons were required to vacate the dome within Union Station grounds.  If I recall correctly, the dome was cleared around Silver Spring on the eastbound trip. 

By the late 1980's. when I started working for Amtrak, those B&O tunnels had been enlarged, mostly by lowering the floor, and the Capitol Limited had been reequipped with Amfleet II coaches, Budd 10-6 sleepers, and one dome coach that had come (I think) from the Northern Pacific. Amtrak continued the policy of clearing the dome when the train was under wire. On one memorable round trip to Chicago in the first half of 1988, we were delayed leaving Washington because Amtrak had been informed that the former B&O line was blocked by a derailment at some point. When we finally left Washington, we took the NEC to Perryville, remaining under wire all the way. Again, access to the dome was denied until we got past the overhead. At Perryville, we took the Old Port Road to Harrisburg, then the former PRR line via Altoona, Horseshoe Curve, and Johnstown, to Pittsburgh, where we returned to the normal route to Chicago. I understand the old PRR did not use domes because of limited overhead clearance in tunnels, but those tunnels had been enlarged by 1988, as on the B&O. We were assured that the B&O would have the normal route cleared so we could take that route home. However, B&O had another derailment at a different location, so we did the same detour on the return. I don't remember how many of our passengers realized their good fortune in getting to pass over Horseshoe Curve in a dome car (although the westbound passage was after dark).

Tom   

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Posted by ATSFGuy on Tuesday, May 30, 2017 7:13 PM

Eastern Roads are riddled with Tunnels, steep grades, low and tight clearances, and lots of single track territory. I believe L&N, SAL, SOU, ACL, CofG, FEC, and the Northeast had a lot of tunnels.

No dome cars north of Washington and around New York because of these issues.

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Posted by BMMECNYC on Thursday, May 4, 2017 7:04 PM

http://www.hoosactunnel.net/bore.php

 

Does this answer the question?  While not being a standard (little standardization was present in the early years of railroading), the dimensions were specified by the contract to build the tunnel.

The website linked has a brief synopsis.  Builders of the Hoosac Tunnel (by Cliff Schexnayder, PE) is an excellent read, which goes into in depth information about the building of this tunnel.  

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Posted by DSchmitt on Wednesday, May 3, 2017 12:34 PM

ATSFGuy

What were tunnel heights back east?

 

They varied, but generally lower than in west because smaller equipment when they were built.  22 posts and no definitive answer because there is none. 

A discussion: Link previously posted above

http://www.railroad.net/forums/viewtopic.php?f=136&t=65680

 

 

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Posted by ATSFGuy on Wednesday, May 3, 2017 12:13 PM

What were tunnel heights back east?

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Posted by tomikawaTT on Friday, April 14, 2017 8:15 PM

The ex-Hudson River Railroad tunnels north of Peekskill, NY, were short, tight bores through solid rock.  They were holed through before the Civil War, and AFAIK were never enlarged.  The Hudson River RR became the New York Central main line - and those low tunnels held the Niagara to a height a foot lower than most 4-8-4s and helped to keep domes out of Grand Central Station.

So, why haven't they been daylighted?  Traffic is heavy, those razor ridges are TALL - and the adjacent river has been sounded deeper than the test depth of pre-WWII submarines.  The only other option would be to move away from the river - into a continuous tunnel through rock the equivalent of ceramic armor.

Chuck (Modeling Central Japan in September, 1964 - before the JNR North Coast line was moved inshore by tunneling)

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Posted by NYBW-John on Wednesday, April 12, 2017 8:43 PM

cowman

Not sure of the exact dementions, but a few years ago they lowered the track in the tunnel that goes under Bellows Falls, VT.  Before the project started there was a front page photo of an  Amtrak FP-40 coming out of the tunnel, I wouldn't wanted to have been a flea on either the top or a side, it filled the tunnel.  Measure your tallest car or loco and make it just fit, just barely.

Have fun,

Richard

 

I don't know that I want to go quite that far. Theoretically the tunnel was bored in the era when crewmen would be on roofwalks and would need to be able to lie down and still pass safely through the tunnels. The fact that telltales were necessary tells me that tunnels weren't too much higher than the tallest car. If they were bored to modern standards telltales wouldn't have been needed.

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Posted by cowman on Tuesday, April 11, 2017 5:02 PM

Not sure of the exact dementions, but a few years ago they lowered the track in the tunnel that goes under Bellows Falls, VT.  Before the project started there was a front page photo of an  Amtrak FP-40 coming out of the tunnel, I wouldn't wanted to have been a flea on either the top or a side, it filled the tunnel.  Measure your tallest car or loco and make it just fit, just barely.

Have fun,

Richard

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Posted by 7j43k on Tuesday, April 11, 2017 4:57 PM

Goofy Tunnel is at Applegate, CA.

 

Ed

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Posted by DSchmitt on Tuesday, April 11, 2017 4:37 PM

7j43k

Since you're doing a rock bore, it would be an option (in the prototype world) to give them mouse-ears:

 

 

Most of the missing material was removed on purpose.  You can do the same thing to a rock bore.

 

And I just have to show a picture of the Goofiest Tunnel in the World:

 

 

Nice view of Keddie Wye.  I don't think I have ever seen a photo that wasn't taken from the highway before.  

------- 

Where is goofie tunnel?

 

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Posted by 7j43k on Tuesday, April 11, 2017 3:39 PM

Since you're doing a rock bore, it would be an option (in the prototype world) to give them mouse-ears:

 

 

Most of the missing material was removed on purpose.  You can do the same thing to a rock bore.

 

And I just have to show a picture of the Goofiest Tunnel in the World:

 

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Posted by NittanyLion on Tuesday, April 11, 2017 2:40 PM

NYBW-John

 

 
RR_Mel

I used the HO NMRA gauge plus a ¼” for my tunnels and they look pretty good.
 
 
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 

 

 

I thought of using my NMRA gauge but then realized that is probably set to accomodate modern hi-level passenger cars and double stack containers. That would probably be higher than what I have in mind.

 

I'm pretty sure that the standards gauge dimensions predate double stacks. 

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Posted by NYBW-John on Tuesday, April 11, 2017 2:36 PM

wjstix

 

 
NYBW-John

Was there a minimum height standard for railroads in the first half of the 20th century or was it whatever the railroad decided it needed to be.

 

 

Most railroad tunnels in the eastern US were built earlier than that, sometimes as far back as the 1840s. There was no regulation as far as the size of the tunnels at that time, I don't know that there ever has been. I suspect railroad / engineering organizations may have had a set of 'recommended practices' but the railroad buidling the tunnel could pretty much build what they want.

One way to get the information you want might be to check the MR archives for old articles on building layouts with tunnels. The NMRA and other specs for height required under bridges, in tunnels etc. was less back before 'hi-cube' and vista-dome cars came along, so maybe check articles from the 1930's to 1960's. (Nowadays articles often talk about a 4" clearance, but seems to me many older layouts were built with 2-1/2 to 3" clearance in HO.)

 

I was thinking along those same lines. Given my era and locale there is zero chance any of the modern high equipment (Superliners, double stack containers, etc) would ever need to travel down this line. The tunnel I plan will accomodate the railcars that I plan to use on that line. If at some future date I want to run taller equipment, I will face a very prototypical dilemma.

I was hoping to hear that there weren't any set standards for tunnel height and that seems to be what you are telling me. My research has shown several tunnels that I estimate to be no taller than what I plan.

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