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Mamod/Hobbies SE3 prewar


This is the prewar version of the SE3 with a single cylinder and geared countershaft. It is basically a larger version of the pre-war SE2 but with two cast frames supporting the engine and countershaft instead of one.

The boiler is 2" diameter x 5 1/4" long. It has a safety valve, Bowman style whistle and a water level plug. The chimney is mounted on the boiler and it receives the exhaust from the engine. There is no steam dome, just a compression joint to the steam feed pipe. All other pipe connections are the same compression fitting.

The steam feed goes to the top of the engine frame via an inline oiler. It has no throttle. The engine frames are cast brass and have plain bearings for the crankshaft and countershaft.

The engine is a single oscillating cylinder, 5/16" bore x 5/8" stroke. The piston rod is connected to a 1" diameter disk crank. Between the frames on the crankshaft are a 1 3/4" diameter flywheel and a 1/2" diameter gear wheel; originally 20 teeth but now a Meccano 19 tooth one. On the other end of the crankshaft is a 5/8" diameter pulley. The small gear meshes with a 1 1/2" gear wheel on the countershaft; originally 60 teeth but now a Meccano 57 tooth one, giving a 3:1 speed reduction. The countershaft ends have a pulley and a plain bush. The shaft is Meccano diameter so any Meccano parts can be fitted for drive purposes. The crankshaft and countershaft bearings have holes drilled for lubrication.

As can be seen from the bottom photo on the left, as acquired, it was in extremely rusty condition with virtually no original paintwork except on the brass engine frame. All the moving parts were seized up completely. I gave it the minimum restoration needed to get it going and to protect it from further deterioration. This required stripping, derusting and repainting of the steel parts (base, firebox and boiler strap). I made no attempt to remove the pitted surface left by the rust. It also required the replacement of the gear wheels and countershaft. The gears had missing teeth and the large one was rusted solid onto the shaft. These are now Meccano parts (suitably modified in the case of the small gear). Other minor replacements were the usual washers, springs and the handle on the whistle.

Make Model Made Description Cylinders Cylinder Type
Mamod/Hobbies SE3 prewar c1937 Stationary 1 Single acting
Piston Diam mm Stroke mm Valve Type Boiler Type Fuel Mechanical Condition
8 16 Oscillating Cylinder Horizontal Meths Restored
Cosmetic Condition Paintwork Packaging Purchased Purchase cost Additional cost
Restored Restored Cardboard box September 2012 211 ~15