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Standard HO Loco dimensions ?

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Standard HO Loco dimensions ?
Posted by Me the Settler on Tuesday, September 01, 2009 4:06 PM

Folks,

I'm new to model railroading and have plenty of doubts !

Can someone tell me if there's a standard size for HO locos (length, height, depth) ? I was surprised to know that there's a sort of sizes ranging from 7" to 12" ....

Thanks in advance !

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Posted by wjstix on Tuesday, September 01, 2009 4:42 PM

The problem is real locomotives came in greatly diverse sizes and shapes, so scale models of them are going to be many different sizes too.

From the Ron Nixon collection of Northern Pacific steam engine photos at http://www.montana.edu/.

Stix
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Posted by Me the Settler on Tuesday, September 01, 2009 4:46 PM

 Thank you Stix !

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Posted by IRONROOSTER on Wednesday, September 02, 2009 12:50 AM

 The NMRA has a standard for clearance for height and width, see this page http://www.nmra.org/standards/sandrp/s-7.html.  For a discussion of clearance as it relates to the prototype see http://www.nmra.org/standards/sandrp/gauge.html

Enjoy

Paul

If you're having fun, you're doing it the right way.
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Posted by Me the Settler on Wednesday, September 02, 2009 9:45 AM
Thank yo, Paul
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Posted by Allegheny2-6-6-6 on Wednesday, September 02, 2009 11:30 AM

 For all intents and purposes the only real standard is that the model is 1:87 size of the real locomotive. A 2-10-0 Decapod is no where near the size of a 4-8-8-4 Big Boy or a Y3 Mallet but all three with handle an 18" radius curve. In most cases that is the only thing one would be concerned with is what is the minimum radius curve that the locomotive can negotiate. The thing is in some cases with model railroad unlike the prototype an locomotive such as a 4-8-4 or a 2-10-2 requires a larger radius curve then lets say the two articulated locomotives like I mentioned above.

When your shopping for locomotives be aware of what minimum radius is required that and minimum turnout size are the  Achilles heal all models have.

Just my 2 cents worth, I spent the rest on trains. If you choked a Smurf what color would he turn?
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Posted by ndbprr on Wednesday, September 02, 2009 1:57 PM

The Official Railway Equipment Register (ORER) contains just about all information and a lot more anyone would ever want to know about railroads, railroad equipment, interchange points and information regarding railroad cars in service in the USA.  Is there such information for engines you may ask?  I am not aware of a a source but all railroads have standards that all engines must meet and I suspect that a couple of the car standards are held by the engine manufacturers.  By the way an ORER can be had on E Bay from time to time and is published quarterly for the railroads who throw out the old ones.  If you can find someone at a railroad you may be able to get one for free.  They are basically the biggest yellow pages you have ever seen in you life and as I said have more informatuion then anyone could possibly absorb.  So here are some car clearances from the ORER:

For unrestricted interchange service - width 10' 8", height 15' 1", rail clearance 2 3/4" absolute minimum.

Limited interchange - height increases to 15' 6"

Double stacks width is 9' 11", height increases to 20' 2"

Open top cars 10' 8" width and maximum load height of 15' 1"

What that means is anything 10' 8" wide or less, 15' 1" or less high and rail clearance of 2 3/4" or higher  can run on any railroad.  Since engines appear to be totaly interchangeable I would venture a guess that they all meet this requirement.  Anything bigger requires the railroads to coordimate movements and find routes that are not restrictive to oversize loadings.  So if one is interested in how this translates to a given scale divide each of the dimension by the scale.  For HO this translates to:

width - 1.47" (say 1 1/2")

height 2.08" (say 2")

clearance .03"  (don't try this at home)

Track clearances side to side are whole nother issue and require larger separation the longer the car.  Typically in HO 2" beteeen centers on straights are adequate and 2 1/2" on curves subject to decreasing radii restrictions.  By the way the ORER has a graph with each clearance indicating car overhang by length for consideration.  All this can be avoided by purchasing an NMRA clearance gauge which allows the user to confirm all clearances on ones model railroad.

 

 

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Posted by tomikawaTT on Wednesday, September 02, 2009 2:50 PM

The only thing standard about HO (as practiced with North American prototypes) is the scale ratio, 3.5mm = 1 foot, also stated as 1/87.1

The AAR specifies a series of 'plates,' which actually give the dimensions of the hole in a wall that the locomotive (or car) has to be able to pass through.  The NMRA gauge is the right shape, but a compromise size - good enough for most purposes, but not for some things (like double stack container cars) that have come on the scene since it was developed half a century or so ago.

Stix showed how steam locomotives could vary in size.  Diesels have the same sort of size range, from industrial switchers that resemble a truck cab and engine on four wheels, out to the UP monster that ran on two eight-wheel trucks.

Passenger cars weren't as diverse, but they were (and are) long, and thus require wider radius curves than small freight cars.  Freight cars, on the other hand, can be as short as 24 feet over couplers (ore jimmies in taconite service in Minnesota) or as long as 89 feet over couplers (those humongous hi-cube box cars.)  Special service cars can be even longer, wider and higher, culminating in the Schnabel cars which are designed to carry immensely heavy (and immensely oversize) machinery.  Even empty, those cars are longer, wider and higher than anything else on the railroad.

WHEN you model also makes a difference.  During WWII and just after (the 'transition era') the dominant box car was the forty foot AAR standard design.  Today, all those 40 footers are history and box cars shorter than 50 feet are almost unknown.  Likewise, huge steam locomotives were replaced by multiple-unit assemblages of comparatively short first generation diesels - which then became longer with each new 'generation.'

I won't even mention the plethora of gauges other than standard.  I once printed out a list of track gauges from a website whose link no longer works.  Common carrier railroads have been built in gauges from 15 inches to 7 feet 1/2 inch - and there are seven pages of sizes and users between!

Chuck (Modeling Central Japan in September, 1964 - in 1:80 scale, aka HOj)

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Posted by nik .n on Wednesday, September 02, 2009 6:15 PM

 As Stix showed, locomotives can have many sizes. Typically, smaller locomotives were made for switching work, or for main runs if a larger locomotive was not able to negotiate the trackage. And if one was not able to run by itself, two or more of its type were double headed. For example, The narrow gauge that used to run by my house used two 0-4-0's double headed for the run up the mountain. The big locomotives like the Big Boy were used for mainline freight service up and down long, steep grades like the run between Ogdon and Wasatch.

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Posted by BerkshireSteam on Thursday, September 03, 2009 1:08 PM

EMD F7A prototype: 50 feet 8 inches, HO scale: 7 inches

EMD DD40AX prototype: 98 feet 5inch, HO scale: 13.6 inches

GE 44-ton switcher prototype: 34 feet, HO scale: 4.7 inches

GE Genesis prototype: 70 feet, HO scale: 9.6 inches

As stated it all depends on the locommotive and what scale. mutliply HO numbers by 1.81 for O scale, multiply by .544 to get N scale dimensions.

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Posted by ndbprr on Thursday, September 03, 2009 3:39 PM

Yes they come in all sizes dependent on the job but as the AAR car dimensions show there are maximum sizes for height and width in interchange and I highly doubt the dimensions have gotten smaller as engine size and length has increased.  Therefore it is a fairly safe bet that nearly all engines built from smallest to largest have been less than 10' 6" wide or higher than 15' 1" with two exceptions that I know of.  The Virginian 2-10-10-2 engines had 48" low pressure cylinders that required the cylinders to be installed after arrival on Virginian property due to their width and clearance issues on the delivery roads.  The other example may be the stack extensions on ATSF engines for use in open territory but even they were capable of meeting the 15' 1" height by lowering the stack.  Length does vary considerably however.

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Posted by G Paine on Thursday, September 03, 2009 4:40 PM

Allegheny2-6-6-6
A 2-10-0 Decapod is no where near the size of a 4-8-8-4 Big Boy or a Y3 Mallet but all three with handle an 18" radius curve.

Need to be careful on those big guys, most are designed to fit 18" radius curves, but check the manufacturers specs before you go buy one and expect it to run on those sharp curves. The same applies to full length 85' passenger cars. For instance, Walthers cars need 22" radius or they will derail; IHC and Rivarossi will run on sharp curves. IN the case of all large/long equipment, they all look better running on wide curves over 22" radius -> 30" radius is even better.

George In Midcoast Maine, 'bout halfway up the Rockland branch

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Posted by tomikawaTT on Thursday, September 03, 2009 9:41 PM

ndbprr

Yes they come in all sizes dependent on the job but as the AAR car dimensions show there are maximum sizes for height and width in interchange and I highly doubt the dimensions have gotten smaller as engine size and length has increased.  Therefore it is a fairly safe bet that nearly all engines built from smallest to largest have been less than 10' 6" wide or higher than 15' 1" with two exceptions that I know of.  The Virginian 2-10-10-2 engines had 48" low pressure cylinders that required the cylinders to be installed after arrival on Virginian property due to their width and clearance issues on the delivery roads.  The other example may be the stack extensions on ATSF engines for use in open territory but even they were capable of meeting the 15' 1" height by lowering the stack.  Length does vary considerably however.

Just leafing through my copy of Model Railroader Cyclopedia - Volume 1, Steam Locomotives. 

It seems there were quite a few locomotives that were more than 15' 0" tall.  The ATSF locos were all flirting with sixteen feet without stack extensions.  Even the Russian Decapod measured 15' 10.5 inches at the stack.  Later, so-called superpower locomotives were all in the sixteen foot zone, with more than a few taller.  SP late steam seems to have had 16' 4" as a standard, while the grand champion was the 2-6-6-6 - 16' 5" from rails to stack.

Absolutely the shortest 4-8-4 was the NYC Niagara.  By almost turning the topside fittings inside out, the loco was held to 15' 2".  Other NYC locos were also short - driven by the tunnels in the Hudson River Narrows.  That was probably why the USRA height standard was 15 feet even - those locomotives had to fit every railroad's maximum height limit, and NYC was a big user of USRA power.

So fifteen feet was the height limit on one Eastern railroad.  It was hardly universal.

Chuck (Modeling Central Japan in September, 1964 - with steam locomotives 4 meters or less high)

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Posted by ndbprr on Friday, September 04, 2009 8:48 AM

I can accept that minor differences and variations in steam engines occured since they rarely left the home railroads rails.  I'd also bet the farm that when conditions caused railroads to have to run their trains on another railroad a discussion or knowledge of clearances was of prime consideration.  Today I still contend that every diesel meets the 10' 6" width and 15' 1" height of the AAR standrad.  Otherwise all the interchanging of diesels would be highly impractical.

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Posted by blownout cylinder on Friday, September 04, 2009 9:09 AM

I thought that even with the variations in dimensions that did exist in Steam and some diesel locomotives that the standard dimensions used by the AAR would have some validity. Those variations that are mentioned do not vary so hugely that there is no way anything would work together. It may be true that the age of steam had non standard issues but these are largely contained now. They all meet---to within 6".   

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