Frequently Asked Questions About TT Scale

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What is TT scale?
TT scale is a model railroad scale whose size falls in between HO and N scale.  It's actual scale measurement is 1/120, or 0.10 inch = one foot, or one inch = ten feet.  It's track gauge was set at 0.471 inch or 15/32.  12mm is currently the accepted gauge, which is 0.472 inch.  TT scale was once the smallest practical model railroad scale available, and quite popular, even though it was (and is) primarily a craftsman's scale (Almost everything was assembled from kits or scratch built.).  You could say that TT scale is close to HOn3.  So you can have a main line model railroad in the same space as an HO narrow gauge railroad.

Where did it come from?
TT scale was the invention of an engineer by the name of Hal Joyce around 1940, who also created HP Products, but commercial production was delayed until 1945 because of the war.  HP brought out an extensive line of locomotives, cars, track, and accessories.  Other manufacturers also joined the ranks of TT scale producing items.  Gandy Dancer, Jewel, Craftsman, Star-Line, Kemtron, and Christoph Products just to name a few.  TT was a fairly popular scale through the 1950's.

Why haven't I heard of TT scale before this?
TT scale has very few followers or modelers in the United States today.  Most of the major model railroading publications do not even acknowledge that it exists.  When N scale made it's appearance in the 1960's, and using better manufacturing processes that made superior detailing possible, as well as cheap ready to run equipment, TT scale declined rapidly.  But because of the Internet, TT'ers have started to come together for modeling discussions, and to voice their needs and wants.  Thus, more modelers are hearing about TT scale today.

Is TT scale popular anywhere?
Yes.  TT scale is very popular in the European countries.  Rokal, in Germany, started manufacturing some items in 1949, and by 1952 had a full line of engines, cars, track, and accessories available.  Other manufacturers in Germany and other countries also started manufacturing TT scale items.  TT scale in Europe is second only to HO scale, and is gaining.

What is available in TT scale?
If you want to model European railroads, everything is available, ready to run.  If you want to model North American railroads, items are available as well, but not in the variety and quantity that they are for European model railroads.  Locomotive types are limited, as are cars, buildings, and accessories, and all are in kit form.  But things are getting better.  Since the track is the same gauge for European TT and American TT, it is readily available and is a very good quality product.  Tillig (in Germany) has the most complete line of track and turnout items including curved turnouts and double-slip switches.  These are available from Euro Train Hobby who has an extensive web site.  Most other American items are from left over stock of the original TT scale manufacturers, or from cottage industries casting items in resin.  European and Australian locomotive drive kits can be used for engines, but they are still kits.

What is the minimum radius for TT scale?
The accepted minimum radius is 14 inches, although you can possibly go down to 12 inches, but you will be limited on some equipment that can be used.  The NMRA has a section or list of Recommended practices for TT scale.  These can be seen at the NMRA web site.

Where can I get TT scale items?
European TT scale trains can be gotten from Europe of course, but also from importers such as Euro Train Hobby in New Jersey.  American TT items can be gotten from some of the old timers that are selling off their excess stock, such as Larry Sayre formerly LarCo Models, and John Harmon, formerly Allegheny Model Products.  Also, some of the newer manufactures / modelers have a good variety of items from engines, cars, buildings, and other accessories, all in kit form.  These items can be found through searches on the Internet.  The primary web site for these items is  However, there are also a few other small manufacturers out there that have TT scale items available who are not associated with such as BTS and Sleepy Hollow Models, so a good Internet search of TT scale will certainly produce some good results.  Also, eBay seems to have TT scale items on there quite regularly.  You must search in Model Railroading, "other scales" and "TT" to bring up the list.  Also you can search "120" as well.  An NMRA type standards gauge and a TT scale ruller are available from Coastal Engineering, who has a listing on

Is TT scale more expensive than other scales?
TT scale trains and kits are priced about the same as HO and N scale items.  Some items may be less, some more.  Because TT scale in America today is supported solely by a cottage industry, some items may be produced and sold in limited numbers.  The older and original TT scale items may be more expensive, as some are starting to view them as collectable.  However, there are still some good running original HP steam locomotives available for a reasonable price.

Where do I learn about TT scale?
TT scale does have it's own publication, albeit a small one.  It is called "The TT Empire", and is published quarterly.  Editors change from time to time, as does it's address, so a web search may get the best results.  Also, there are Internet email chat groups available.  Yahoo Groups hosts several.  One is TTSMR which caters to all TT model railroaders, and TT_IMS which caters only to active TT scale model railroaders.  These are the best ways to learn about TT.

Is modeling in TT scale different from other scales?
No.  Modeling is the same, although you will find that most things are available in kit form.  However, because TT falls between HO and N scales, you will find that you can use small HO buildings and large N scale buildings to good advantage.  Track wiring and turnout controls are also the same.

Is Narrow Gauge available in TT scale?
Yes, but it is in it's infancy.  Most modelers that are modeling TT narrow gauge are also modeling TT standard gauge as well.  N scale actually scales out to a 42 inch gauge, but the six scale inch difference between 42 inches and 36 inches is not enough to bother TT narrow gauge modelers.  Plus, by using N scale track, there is a readily supply of items available for use.  Narrow gauge modelers are using N scale track, trucks, couplers, and locomotive power units.  N scale freight cars can be used almost as is.  New Zealand uses narrow gauge extensively, and there is a group of NZ120 modelers modeling their narrow gauge.  Some etched brass diesel locomotive shells are available that will fit on standard N scale locomotive frames.  Details can be had by selecting small HO ones or large N scale ones.  Larry Sayer also is selling TT scale details from his stock, so although made for TT standard gauge, they are well adapted to use in TT narrow gauge.

What about using DCC?
There are several modelers currently using DCC systems to control their TT scale trains.  Most N scale decoders will work very well on the newer locomotives.  The older locomotives may offer a challenge for installing decoders because the motors are larger and isolating them from the frames may call for some ingenuity on the part of the modeler.  And, TT scale has the advantage of being large enough to be able to install sound decoders in the locomotives.

Why would I want to switch to, or model in TT scale?
Admittedly, TT scale is not for everyone.  But if you like to build models, and also like a good challange every now and then, why not give TT scale a try?  However, as we said before, TT scale is larger than N scale and smaller than HO, so it may just be an ideal scale.  I can guarantee you that your TT scale model railroad will not look like every other model railroad that uses the same buildings and other things that every hobby shop carries.

Written by Elmer McKay, March 2006.  Some information obtained from Railroad Model Craftsman, July 1988.  If you would like to learn more about TT scale, you may contact the author at < >.  Use a subject line that pertains to your inquiry.  Otherwise the Spam filter may eliminate your email.