SML 32 Twin Cylinder SteamEngine

finished engine side view

The instructions for this model were first published by Meccano Ltd. as Super Model Leaflet (SML) no.32 in 1929.  A scan from original instructions shown on the left. I wanted to build this model  ever since I bought "The Meccano Super Models " published by New Cavendish and written by Geoff Wright over thirty years ago. At the time I had no where near enough parts required to build such a large model.

The model calls for a large range of perforated plates and braced girders but a bigger problem was the non availability of the Channel Segments P/N 119. This part was discontinued by Meccano in the 1935, 32 are required for the rims of the two flywheels.  I very much wanted to use the Channel Segments as these give the flywheels a more elegant appearance than the large flange rings p/n 167b suggested as a replacement by the Meccano Company when  part number 119  was discontinued.  Replicas have been made since, notably by the late William R.(Bill) Inglis* from Australia, during the 1970s and sold widely.  Unfortunately these were also discontinued. Late in his life Bill made a final batch and I managed to acquire from him the 32 required and had them powder coated in 1950s mid-green. So a long cherished ambition could then be fulfilled and construction begin. Some dealers such as Meccano sell complete replica rings.

Cross heads close upI have modified the design in several ways:-
parts used that were not available when the model was designed , such as flexible plates,
more solid looking bearings for the crankshaft using semi circular plates and girders,
the cylinders are constructed from flexible plates rather than the skeletal construction of the originals,
the valve cylinders I built from 2 hole x 2 hole angle girders actually non standard parts but I could have used regular girders and flat girders to achieve the same effect, connecting  rods have been "beefed up" by using four layers of perforated strips.

The pictures below show the various stages of construction and the time spent on construction
June 05 Base frame, engine base and cylinders constructed.
June 17 frame and engine base brought together flywheels crank shaft and connecting rods  temporally fitted.
July 08 Flywheels, connecting rods pistons all assembled, aligned and operating. Motor drive fitted
July 20 Boiler constructed and assembled steam pipe fitted completing the model.

One riddle of the construction for me was the 9 hole strips for the piston slides in front of the cylinders.The throw of the cranks was just to long for the slide not hit the bolts at each end, I overcame this by making a ten hole strip.  Another builder has since told me he never came across this problem I imagine my problem was probably not closing up enough on the slotted holes. Many of the rods also needed to be of non standard lengths, this was not mentioned in the instructions. Although filing flats on the crankshaft rods was suggested but I did not find I needed to do this. .
Although the design is now 90 years old (2019) its a nice model to watch running, it even sounds like a steam engine with a lovely swish from the cross heads as piston slides in and out and a good whirr from the governor. I think it he model particularly suits the post war red and green colours.

The model is driven through a belt reduction drive from a 12 volt non Meccano motor from a power tool.

A video of the engine made in January 2015 can be viewed on YouTube click on the logo.


A video of the engine running at the Museum of power Langford can be viewed on YouTube click on the logo.

Engine base

engine frame and cylinders
crankshaft flywheels

finished enging

Page created August 2004 Page last revised July 01 2019