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Nn3 Track Work Pages
Track Standards Page 1

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Nn3 standards

Using the North American  N-Scale ratio of 1:160 if you convert the Micro Trains track gauge of .262 inches to scale of 1:1 in feet and inches you come out at 41.92 inches, this is the same thing as saying 3 ft 5.92 inches.

What I have done is to define a generic standard which has developed around the use of Z-scale track and mechanisms for N-scale narrow gauge to a finer standard and identify it. I have in fact not changed what is essentially known as Nn3. While many will be happy with the generic Nn3 standards others are a bit more demanding of themselves and want a higher standard to work to and this accomplishes that for the few who might be interested. So you can substitute Nn3 for 3 ft 6 in. in the standard below and get what is generic Nn3 that the majority of North American modellers are using to model North American N-Scale narrow gauge whether it is actually 3 ft gauge or 3 ft 6 in gauge.

My Track Standard for generic Nn3 Narrow Gauge in N-Scale
or for fine scale narrow gauge 3 ft 6in. railroads in N-Scale

Code 55
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Code 40
3ft 6in in N-scale
This standard is consistent with using the Micro Trains Track that is now available to create a railroad operating on 3 ft 6 in gauge track. Unfortunately there are no mass produced switches for the Micro Trains track and so hand laid switches are the norm. 

Republic Locomotive Works is the largest source for Nn3 material for North American profile narrow gauge equipment (in particular the Colorado 3ft lines) for either 3 foot gauge or 3 ft 6in gauge. He has many kits for various cars and has reproduced the original Robert Sloan steam engine conversions for Marklin chassis. In conjunction with GHQ RLW has produced one pewter conversion for a C-16. RLW continues to stock all the GHQ and Gold Rush conversion kits produced in pewter by GHQ except for the K27. RLW also produces craftsman quality laser cut wood kits fully detailed with sound in premier editions of major industries for any railroad, but of particular interest to the narrow gauge and craftsman modellers in N-Scale. 

Micro Trains of the USA, LOK 14 of Germany and Marklin, & Aspen Models of the Germany/USA have in the past marketed limited quantities of RTR Brass models in Nn3. 

In early 2009 only Aspen is still producing r.t.r brass models as well as kits for these engines. Micro trains made a 2-6-0 in Z and Nn3 and has not repeated the offering. LOK14 was quite prominent for a number of  years but since late 2005 has not produced anything new. Their 2-8-2 K27 was highly prized as smooth runners.

Nn3
I have been modeling in Nn3 since the mid 70's and the diagram to the left is is the original track standard that I used for hand laid code 55 rail. I modified it in January 2001 to reflect new ideas from the Nn3 group at http://groups.yahoo.com/group/nn3. The NMRA has a set of standards for Nn3 but they are not reflected in any commercially available products, but some members of our group use them for their hand laid track. I have modified it a bit further since them for myself as I found for dual gauge switches I needed to go to Code 40 rail and so most of the drawing has been modified to suit code 40 rail.

There has been a very large increase in the interest of Nn3 and other narrow gauge standards in N-Scale and related scales in the late 1990's largely in part to the popularity of the internet which allows widely separated people to get together and discuss their scale. They range from members of the UK based 2MM Association to other N-Scale groups in North America, Europe,  Australia , New Zealand, and Japan. Most if not all have based their standards on using Z-Scale track commonly referred to as 6.5mm and mechanisms from Marklin of Germany and Micro Trains of the USA to model N-Scale narrow gauge. N-Scale in North America is 1:160 and so the closest match at this scale to 6.67mm is  3ft 6in narrow gauge. It is one of the several narrow gauge track widths used in North America, but not the most popular. 

In recent years Kadee and now Micro Trains produce North American profile standard gauge track for Z-scale which is what most of us use for Nn3 track. The track produced by Micro Trains starting in 1999 is gauged for correct scale of 3 ft 6 in in N-scale Narrow Gauge not 3 feet. While a little wider than Peco in gauge it is essentially the same as Marklin Z-Scale track and most things in Nn3 will run on all three track types without a problem.

The first commercially available rolling stock for Nn3 was first produced by Nelson Grey in upstate New York. When poor health made it mandatory for him to quit manufacturing in his basement, the moulds were purchased by Kadee and continues today under Micro Trains after Keith and Dale Edwards split the company we knew as Kadee into two separate companies. Micro Trains has produced one engine a 2-6-0 based on an investment brass casting installed on a Marklin 2-6-0 chassis. They also produce a Z-Scale F9 A & B units and various freight cars from the moulds originally produced by Nelson Grey. 

Besides Nelson Grey, Robert Sloan is the other grandfather of Nn3, he produced the earliest conversion kits for steam engines using Marklin chassis and was the author of the two very valuable resource books on Nn3. They are currently published by Ntrak and are kept up to date by Ntrak. The first book is Nn3 Manual and was published in 5 editions. The second book was the Narrow Gauge Data Book. These are both available from Ntrak. http://www.ntrak.org

The current source of all things Nn3 is Republic Locomotive Works. A labour of love for Marshall Thompson. He produced a variety of kits for various cars, structures, Bridges, turntables, engines, and the like. The web site was created and is maintained by Bruce Hunt. Bruce Hunt was instrumental in the development of the Nn3 turntable which is fully indexed. Tom Knapp has produced a new Nn3 3 truck shay that is being sold through Republic Locomotive Works exclusively.

In 2008 Akia (a.k.a. RealZJ and Plus UP) produced a very nice 10vdc transistorized power pack and roadbed track system which parallels the Micro Trains Road Bed Track system. The only thing the Japanese system does not have yet are switches. The attraction for Nn3 is that the tie spacing on this track is almost identical to Kato Unitrack and as such is correct for narrow gauge track in N-scale. I also found with some paint you can make the Micro trains Switches match the Akia track work by painting out every other tie on the MTL switch and then painting over the tie that is left with a broader brush stroke.

Republic Locomotive Works 
16 Little Cape Horn 
Cathlamet, WA 98612 
Tel (360) 577-6479 
e-mail rlw87 is at teleport period c o m
Web Site http://www.republiclocomotiveworks.com/

Here is table form to the right are some numbers for track and wheels standards used for Nn3 modeling and operating.
Nn3 Standards Worksheet 2mm General use standards NMRA
12/31/2003 codes mm  in  codes
track        
         
Track gauge (nominal) TG 6.50 0.256 G
PECO FLEX    commercial track gauge min   6.57 0.2585   
MTL Roadbed commercial track gauge max.    6.73  0.265 curves
MTL Roadbed commercial track gauge max   6.60 0.260 straights
(plain track)       gauge min/max   6.4/6.7 0.252/0.264  
(absolute minimum   6.35 0.250 G
Track gauge (trough points/switches) min   6.5 0.256  
Track gauge (trough points/switches) max   6.70 0.264  
MTL Roadbed commercial switches   6.54 0.2575  
Flangeway max WF & CH 0.60 0.024 F
Between checks max BC 5.30 0.209 S
         
wheelsets        
         
Wheel gauge max WG 6.35 0.250 B + 2T
Wheel gauge min   6.2  0.244  
Back to back min BB 5.35 0.211 B
Back to back max    5.5 0.2165  
Tread width (sugested min) TR 1.00 0.039 W
flange height (depth suggested) max FD 0.75 0.030 D
flange width (thickness at root) max FW 0.45 0.018 T
         
 

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last update to this page 27th February 2009
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