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Wheels for 3mm Steam Locomotive kits

This is for information only, with special thanks to Nick Smith.

3SMR have stocks of wheels as you will see from the list and are available to order.

The list is based on, but not reliant on, data in the third edition of Sharman’s wheel book.


Wheels could loose 3” of their diameter due to reprofiling before a new tyre was fitted, and new steel tyres replacing wrought iron tended to increase the diameter of nineteenth century wheel centres by up to ½” early in the twentieth century .

Kean-Maygib driving wheels have separate ‘Long’ crank pins ref. KM9 (422), the centres are nylon without glass filling. Romford driving wheels have separate ‘Long’ crank pins. Sharman driving wheels all have fitted ‘Long’ crank pins.

3 mm Society Fine Scale ‘Cliffe Newell’ / ‘Stapelton’ ‘W’ driving wheels have different code numbers for long and short pins. Newer 3 mm Society Fine Scale driving wheels have loose pins whereas older ones had them Loctited in place. From 1997, they should have GRP [Glass Reinforced Plastic {Nylon}] centres, which may, or may not, be the same as the Glass Loaded Nylon that Cliffe used.

David Stapleton Engineering versions of the wheel will be given SN serial numbers by the society. The Stapleton version of bogie wheel has blackened steel tyres, unless they share a nickel silver tyre with a driving wheel. Chris Stapleton is providing 10 and 15 spoke wheels to fit Buckjumpers. These are supplied by Chris direct or Finney and Smith, not by the 3 mm Society.

Nearly all driving wheels use a 1/8 inch axle but 3 mm Society Fine Scale driving wheels have a shoulder on the axle and a 2 mm hole in the wheel so they can be used with your own 2 mm axles if you wish. The only difference between the 12 and 14.2 mm gauge wheels is the length of axle between shoulders. Sharman axles are supplied over length.

Kean-Maygib are exact length with an option (KM13) on longer ones for outside cranks. 3 mm Society non driving wheels use 1.5 mm pointed axles. Kean-Maygib non driving wheels also use 1.5 mm with a choice of pointed or short axles (or both).

Sharman non driving (and the very small driving) wheels used over length 3/32” axles (=2.35 mm) but these are migrating to 2 mm axles as stock is used up; all the moulds have been changed. Sharman do not offer a 14.2 mm profile but Steve Hodgson will do a P4 wheel profile on ‘Millimetre range’ wheels if asked. Peco/Romford ‘Insulaxles’ are 1.8 mm diameter but I do not know whether Romford still use them.

The obsolete Chris Hardy all metal range used shouldered 1/8” axles for driving wheels with 10 BA threaded ends, and 3/32” for 12 mm driving wheels and all non driving wheels with 12 BA threaded ends, 1/8” axles were available to special order as were 14.2 versions. Flangeless wheels were available from Chris Hardy. Flangeless wheels are available from Romford. Cliffe Newell Society ‘W’ flanges add 1.1 mm to the diameter. Sharman flanges add 1.2 mm to the diameter. Kean Maygib flanges add 1.3 mm to the diameter of pony wheels and add 1.6 mm to the diameter of driving wheels. Chris Hardy flanges add 1.5 mm to diameter of 12 mm wheels and 1.2 mm to 14.2 wheels.

The KM reference for Kean Maygib wheels is the 3 mm Society’s, Kean Maygib’s own reference is in brackets. Their 1/8” top hat bearing KM30 is 474, their 2 mm top hat bearing KM24 is 475 and their 1.5 mm top hat bearing KM22.

Romford coach and wagon wheels have a wider tyre and thicker axle (probably 2 mm instead of 1/16”) than the Jackson wheels that they replaced.

Don’t forget handrail knobs (Society PK1 or PK2, or 3SMR, or Branchlines), and plastic loco brakes, Society reference OS12.

The Triang 0-6-0, 2-6-2 and 4-6-0 chassis have 8’ 0” + 8’ 0” coupled wheel base, the Pacific chassis coupled wheel base is 7’ 4” + 7’ 4”. The Castle bogie is 7’ 0”, available in whitemetal as 3SMR L136. The Pacific bogie is 6’ 4”, available in whitemetal as 3SMR L135. The Prairie pony is available in whitemetal as 3SMR L157.

The crank stroke has now been added prototype wheel data. This is taken from Sharman and alternative sources are scarce. The stroke is twice the throw, and is the same as cylinder stroke on outside cylinder locomotives, On inside Cylinder locomotives, the Cylinder stroke is often greater than wheel crank stroke. Outside crank throw is not stated, but Sharman says it is usually 12”.












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