Getting Started in 3mm: FAQ
A guide to getting started with your first 3mm/ft project
(photographs by the above unless otherwise stated)
Where do I start?
The railway modelling scale of 3mm/ft started life
as Triang TT, and indeed even today there are many Triang TT
collectors. However, at an early stage the scale attracted
enthusiasts interested in building their own models and
developing interesting attractive layouts. Initially they
were supported by companies such as Bec and GEM. Then
the 3mm Society was formed, and rapidly became the mainstay
of the scale. Over the years the Society has introduced many
kits, components and tools, and most of all has provided a
forum where experience can be shared, needs discussed and
addressed, and ideas floated. The Society has put a lot of
effort into ensuring that products have kept pace with
developments in the hobby as a whole. For example there is
now a comprehensive range of quality wheels to cater for
modellers needs, components to assemble your own track,
while the range of highly detailed plastic wagon kits from
suppliers such as Parkside and Cambrian stand comparison
with those in any scale.
What track gauge and standards are used?
So, where should you start? We suggest that one good way
would be to try a couple of wagon kits which interest you,
knock up a couple of feet of test track to run them on, and
then think about having a go at a locomotive. However,
before you can actually build anything you need to make a
few decisions about what track gauge, and related standards,
you are going to use. Read on.
Triang adopted the international TT standard gauge
of 12mm but a scale of 3mm/ft (1:101.6) rather than the
smaller TT scale of 1:120; this was accomodate the rather
cramped clearances of British prototypes. Although 12mm
gauge is undersized for 3mm/ft , it is widely used, for
finescale layouts as well as those based on Triang.
The Society publishes three alternative standards to be used
with 12 mm gauge, based on the type of wheels to be used.
The standards are Coarse (Triang), Intermediate (originally
based on wheels such as Sharman and Maygib), and Fine
(compatible with the Society's own finescale wheels). In
practice, most modellers choosing 12mm gauge use
Intermediate standards, and now benefit from a new,
comprehensive range of Intermediate standard wheels
introduced by the Society; these are known as SQ wheels
since the steam locomotive driving wheels fit on
square-ended axles, similar to the Romford wheels of old, to
Which track gauge and standards should I choose?
An alternative to 12mm gauge is the prototypically correct
14.2mm gauge, using Society Fine standards. This has long
been used by a number of Society members, aided by the very
wide selection of Finescale wheels produced by the Society.
A recently developed service has been the conversion of
round-holed locomotive driving wheels to square-holed,
similar to the SQ wheels, to provide the same advantages of
A gauge of 13.5mm has also been around for a long
time, a sort of 3mm equivalent of the 4mm EM, and has a
currently small number of users. It has advantages for
certain prototypes where the clearances in 14.2mm gauge are
a bit tight. Both Intermediate and Fine standards are
available, and the corresponding wheels..
The gauges discussed above are, of course, related to the
"standard" prototype gauge of 4' 8.5". However a number of
other prototype gauges are also modelled. Thus
9mm is used to represent 3' gauge, 15.75mm to represent
Irish 5' 3" gauge, 16.5mm to represent 5' 6" gauge, and 21mm
to represent Brunel's 7' gauge.
12mm gauge is widely used, and there are many fine
layouts which use it. It is the one gauge for which
commercial track is readily available, from both Peco (HOm)
and Tillig (TT) , although the range is limited, and indeed
many modellers use hand-built 12mm track. The main question
is whether you would be satisfied with the underscale
appearance of 12mm or whether you would prefer a gauge
closer to the prototype. A secondary question is if you
adopt 12mm gauge, do you use Intermediate or Fine standards?
If you build your own track you can use either, although
most people use Intermediate. One disadvantage of 12mm gauge
is that the wheels are closer together, which can limit the
choice of gearboxes and motors in locomotives.
What track is available?
14.2mm is most likely to appeal to those who want to build
fine scale track to prototypically correct gauge, and relish
what challenges there are in doing so. The standards
themselves are pragmatic; the Fine standards are not S3,
they are effectively a scaled down EM pushed out to correct
gauge, and are fairly easy to employ. The wide range of
good-looking wheels available is an added bonus. Also,
etched locomotive kits reduced from larger scales can
usually be built without further work to this gauge, not
always true of narrower gauges. The main challenges are with
locomotives with outside cylinders, and sometimes valve
gear, where the slightly thicker-than-scale wheels can lead
to tight clearances; for example, one dodge is to push the
cylinders out slightly.
13.5mm gauge is most likely to appeal to those who want
something closer to the prototype, whilst avoiding the fine
clearances in 14.2mm. To get the most advantage though, you
need to use Fine rather than Intermediate wheels, with the
track standards to suit.
In the remainder of this guide you may find further things
to help you with your choice; a more detailed look at the
track issues in particular is recommended. One thing
which could be worthwhile would be to try a wagon kit with
both 12mm and 14.2mm wheels (easily swapped if you position
the brake gear carefully), and see what you think of the
difference. A recommended choice would be one of the
Society's Parkside wagon kits, with the Society's own
Intermediate and Fine wheels.
The principal off-the-shelf ranges are produced by
Tillig and Peco. Tillig produces a range of 12mm track for
international TT (1:120, approx. 2.5mm/ft), with points in
both ready to use and kit form. The track is good quality,
although in appearance it's fairly obvious that it's
intended for a smaller scale. Peco 12mm HOm track is nearer
to scale appearance, and the right and left hand 24" radius
points are usable with Society Intermediate wheels, and
sometimes Triang (with adjustment); however, care is
required with other Peco pointwork such as the curved point,
which has a very sharp 15" inner radius.
The Society produces a range of track components
including rail and track bases which covers all gauges.
Those who favour soldered track construction can use PCB
timbers and sleepers, and either Code 80 flat-bottomed rail,
or finer Code 60 bullhead rail. However, plastic track
components provide a popular alternative. For plain 12mm
Intermediate track you can use Code 80 rail and Society
Ratio track bases. For plain Fine track in 13.5mm or 14.2mm
gauges you can use Code 60 rail and Society finescale track
bases. Thus it is very easy to produce plain track for any
of the main three gauges; in principal it's no different to
using commercial flexi-track.
Society also supplies plastic chairs for Code 60 rail,
mainly for constructing finescale pointwork in any
gauge. The chairs are designed to be glued to either ply
timbers and sleepers (provided by the Society), or plastic
ones cut from Plastruct or Evergreen strip. You could also
use these chairs to construct plain Fine track in 12mm
gauge, or indeed other gauges such as Irish 15.75mm gauge,
for which bases don't yet exist. You could even use them to
construct track to Intermediate standards in 12mm scale (of
finer appearance than the Code 80 rail and Ratio bases), but
only if you use the Society's modern Intermediate standard
wheels; older Intermediate wheels have flanges which are too
What if you like the idea of using Society components for
plain track, but are worried about constructing matching
pointwork? 3SMR offer a service constructing pointwork to
order, in the principal gauges.
How would I construct track?
As indicated in the previous section, for most
purposes plain track can be easily constructed using the
Society's plastic components, although you may prefer
soldered construction, and if your prototype track is
flat-bottomed, not chaired bullhead, this may be the best
What wheels are used?
Pointwork requires more work, but is easier than perhaps
imagined, and well worth giving a go. The main effort is
constructing the V part of the crossing (sometimes called
the frog), which requires rails to be filed to the right
angle then soldered together. The switch blades also need
some filing. Other than that, it's mainly a question of
proceeding logically (many people start at the frog and work
out from that), adding rail until the point is complete. The
process is similar whether you use soldered construction or
use the Society's chairs. Points have a number of
specialised chairs and these can be produced by butchering
the Society ones.
Accurate track gauges are the key to producing good working
track. Finney & Smith produce a good range in all
gauges, while 3SMR produces roller gauges in 12mm and
14.2mm. The Society provides a high quality jig for
machining and forming point V's, for code 60 rail only.
Templates are a very useful guide when constructing track,
although the accurate bits of the operation are done using
the gauges. The Society provides sets of point templates in
12mm and 14.2mm, although you can also use ones reduced from
larger scales. However, an increasing number of
members produce their own templates using Templot software.
Templot produces prototypically accurate plans in any
scale, including 3mm/ft, will cater for all Society
standards, and can produce complex formations, or even
complete layouts, as well as individual points.
If you've never done it, track production may seem daunting,
but it isn't, so give it a go. All you need is a small
amount of the basic components, and a gauge or two for your
chosen track gauge.
Although in the past a variety of wheels from
different sources have been available, most have
disappeared. We recommend that you stick to the Society's
own wheels where possible. The Intermediate wheels are
to the internationally recognised NMRA RP25 Code 79
standard. The Fine wheels are to the Society's own Fine
What couplings are used?
The current range of Intermediate wheels is aimed at proving
a basic offering in all the main sizes likely to be
required. The Fine range, which has evolved over a much
longer period, not only covers such sizes and more, but
offers prototypically accurate alternatives, such as a
different number of spokes for different prototypes.
In the past, Romford wheels proved popular due to the square
axle end which greatly simplified the process of quartering
driving wheels.. For this reason square axle ends have been
incorporated in the design of the Society's Intermediate
wheels. The Society's Fine wheel currently still need round
axle ends, but if you want simpler quartering one member
provides a service converting them to square ends, for a
You'll usually need appropriate brass bearings for your
wheels. Slaters (Society SL4) pin point bearings are
the most useful for wagons, Kean Maygib KM6 for coach
bogies, KM22 inside bearings for inside use on 1.5mm axles,
and Branchlines 1/8" short top hat (straw hat) for steam
driving wheels; all except the Branchlines bearings are
available from the Society.
B&B 3mm couplings are popular; they are
unobtrusive, self-coloured, assembled just by bending (with
care!) and feature remote uncoupling. Some prefer the
operationally similar DG couplings for more robust use;
other types include Spratt and Winkle. The traditional
Triang type of coupling, in various forms, is still
What motors and gearboxes can be used?
Mashima open frame motors (12/16 or 12/20) have
long been used. 14.2mm users can often, with
advantage, use the more powerful, slower and smoother
Mashima 1220 flat can motor (or sometimes even the 1224);
the 1220 can be squeezed into some of the larger 12mm
locomotives. The smaller Mashima 1015 and 1020 flat cans can
also be used; the 1015 has a mixed reputation but the 1020
seems a good motor.
Will I need to use compensation or springing?
The Branchlines RSL gearbox is an old favourite, and
has the advantage of a grub screw, useful if you think you
may want to pull things apart. Branchlines 2-stage gearboxes
have also been used. However, the Branchlines gearboxes
require careful checking, assembly and running in to work
well. High Level multi-stage gearboxes offer a quality
alternative which is easy to assemble. Finney & Smith
stock two High Level Slimliner gearboxes developed for 3mm
scale, the 3-stage Compact and the 2-stage Compact+; the
gearboxes offer a choice of 3 gear ratios.
For diesels, a variety of approaches are possible. 3SMR
stocks Bullant motorboxes, amongst others, or will obtain
them to special order. The Society produces some motorising
kits which may be suitable.
In a few cases, such as long wheelbase 4-wheel
wagons or coaches, compensation may be of benefit. Worsley
Works offers a simple etched inside bearing compensating
frame, which may be useful, and the Society offers etched
compensating W-irons. Otherwise, for wagons, generally
no. For bogie coaches, the well known MJT bogie kits
are recommended, which include a neat simple compensation
arrangement, and give very smooth running. Uncompensated
bogies can be obtained from 3SMR.
What pickups can be used?
Locomotives generally don't need compensation. However, some
form of flexible chassis arrangement may improve running and
offers opportunities for improved current collection. But
you don't need to go down this route unless you want to.
You can use just the same methods of picking up
current as you would in any other scale. Brass or
phosphor bronze wire bearing on tyre treads, or phosphor
bronze strip bearing on the backs of treads, are all
used. A few members have used split frame methods.
Can I use modern control systems such as feedback
controllers or DCC?
Feedback controllers are widely used. Modern
motors appear to give no problems, but older motors such as
those in Triang locomotives may suffer from overheating.
What would be a good wagon to start with?
Some modellers are trying out DCC. Provided your
locomotives have suitable motors and perform well, and in
particular pick up current reliably, there appears to be no
problem, but it may be good idea to get your
locomotive to work well under DC before converting it to
DCC. N scale decoders can usually be fitted, and in
some cases OO/HO ones.
wagons offered by the Society (code beginnning PP in
the Society lists) are high quality, go together easily, and
include examples from pre-grouping to modern; you'll
need wheels, bearings and couplings of your choice, and of
course paint and transfers. The Society offers some
transfers while 3SMR offers 3mm versions of a number of
Modelmaster transfers. For a wider choice, apart from the
Society, other wagons are available mainly from
Finney&Smith (including some distinctive and some older
period examples) and 3SMR.
What would be a good locomotive to start with?
This depends very much on your taste, experience
and inclinations. For steam locomotive buffs, some
very high quality etched locomotive kits are available
complete with fittings, for example those derived from
Malcolm Mitchell 4mm kits, but they take time and skill to
complete, and even with experience you may prefer to start
with something fairly simple. The Society lists, and
those of Worsley Works, 3SMR and Finney&Smith are worth
browsing. Many recent kits now employ fold up chasses which are
quickly and easily assembled, and some these can be used
with older kits.
What would be a good coach to start with?
The simplest bodies to assemble are the older white metal kits, such as
the ex GEM kits available from 3SMR, and some Society
kits; some are crude by today's standards and may require
minor modifications to use modern chasses, but they are
usually dimensionally correct, can be improved by adding
detail, and may be an acceptable starting point.
Etched bodies obviously require a fair amount of
soldering and take more time; the more modern use
slot-and-tab construction, which helps a lot with assembly,
and if you're happy with soldering, the simpler ones, for
example the smaller Connoisseur 7mm derived ones offered by
Finney&Smith, or the smaller Society ones, may also be a
good starting point. A few etched kits use resin castings
for major body components such as
firebox/boiler/smokebox, so you are saved from forming
the trickier shapes; these include the well-thought-of
Brynkits range, which are obtainable from 3SMR.
With most kits you need to add motor, gearbox, wheels,
couplings, paint and transfers, pickups and handrails to
complete. Cram as much weight in as you can (a good rule in
this scale). Some modellers revell in applying extra
If you're into diesel or electric, look at the offerings of
Worsley Works, Bruce Smetham, and others. For example,
you could take the Worsley Works Class 58, add a Bruce
Hoyle set of whitemetal castings (now obtainable from the
Society), and power it with suitable bogies from say the
ranges offered by 3SMR. Bruce Smetham produces cast
resin bodies for a number of first generation diesels,
including a Western, and a Class 20. Worsley Works
also does an extensive range of etched multiple unit kits.
The only readily built plastic coach kit available
in recent times is the Society's GWR B set, which is perhaps
not up to the latest standards, but will produce a decent
pair of coaches; officially discontinued, examples may still
be available, possibly from the second-hand shop. You
will need castings (buffers RG4 BR23, roof vents 3xRH1),
bogies, wheels, couplings and window glazing. If you
want to add internal detail, use plasticard for partitions,
and PP12 seats. Bogies for most coaches are produced using
MJT etched frames, which are available from the Society in
various wheelbases, together with cosmetic whitemetal
sideframes (GWR 9' Standard ones from 3SMR for the B set).
What transfers and name or number plates are available?
You can apply etched
sides and ends from the Worsley Works range to an
existing, suitably modified, coach; old Triang coaches
can be used, although for GWR 57' coaches the Society's B
set, with sides replaced by PP20 clear plastic coach sides,
is a better bet.
All other coaches are basically etched, and require varying
amounts of additional components. Finney&Smith and
3SMR coaches include castings unless stated, but may require
wire and other bits and pieces. Worsley Works coaches, which
are built on the Comet principle, generally include etched
sides, ends and floor, but always require castings, as do
the the Mallard/Blacksmith coach etchings offered by the
Society. The Society has a booklet by Tony Seal which
contains a lot of useful advice on building etched coaches,
and Worsley Works has one describing the Comet approach.
The BR modeller is well catered for, with various
transfers from the Society, and Modelmaster transfers from
3SMR. For the pre-Nationalisation scene, the Society offers
PC methfix transfers covering mainly the Big Four
post-Grouping companies, 3SMR offers the four Modelmaster
sets which cover many of the common Big Four wagons, while
Finney&Smith offer a number of useful specialised
transfers, both for railway companies and for private owner
wagons. Cambridge Custom Transfers offer transfers from
their standard range in 3mm.
What further information and services are available?
Some locomotive name and/or number plates are available in
3mm from Kings Cross Plates and from 3SMR. The Society
kit MF1 can be used to produce almost any standard GWR
Joining the Society will give you access to a wide
range of products, information, services, and other members,
17 What next?
a) Price List
to members. Contains full listing of most Society
products, with prices.
b) Mail Order
The place for
members to order products listed in the Price List. The
Society is currently re-organising this and the other
Society "shops" to bring
operation up-to-date and to implement on-line ordering.
c) Marshalling Yard
Source of Society and
Peco track, rail, jigs, sleepering, and related items
d) Stock Sidings
The second-hand shop.
Most Triang and and a wide range of other 3mm products
pass through the shop at some time or
other. It's a good
place to look if you are seeking otherwise unobtainable
products, completed kits, and so on.
e) Illustrated Catalogue
illustrated CD-based guide to products of the Society and
major suppliers, including past products.
Ideal for sourcing that
obscure component you've found you need. Currently this is
being adapted to cater for on-line ordering.
f) Mixed Traffic
The Society's highly
popular quarterly magazine. Includes articles,
reviews, hints, arguments, adverts.
Issued with Mixed Traffic.
Latest product news from suppliers, also other news,
shows, area groups.
The main source of keeping
in touch with who's producing what.
Apart from the AGM, which is
also the main showcase for the scale, there are several
other major get togethers.
You can meet other
modellers, and also spend your hard earned cash on Society
and suppliers' stands.
There are a number of area
groups which host their own meetings.
A lively forum for online members
to share information, advice and views.
Well, hopefully you have enough information to
get started, although naturally a lot of things, for example
scenic items, haven't been mentioned. If you haven't
already, then join the 3mm Society and get the product
lists. The major independant suppliers all now have
web sites worth looking at. Think about where you want
to go, make a list of the items you are going to need and
from whom, then send off your orders. However, do
remember that all the people you've contacted have other
lives and other commitments, and may need a bit of
time to respond to your order. In fact, as a general
rule, order things when you know you're going to need them,
not when you actually do, to avoid frustrating waits if
they're not currently in stock.
Once you've joined the Society, then assuming that you have
internet access we recommend that you join the Society's
e-list.This is a very good place to seek help or advice, or
generally keep in touch with what's going on.