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Microcosm M23B Mini Cravling


This is an amazing steam powered walking vehicle.

The engine unit is basically a modified M16, laid on it's side at the rear of the vehicle. It is fired by a single wick meths burner, connected to a tank at the front of the vehicle. The crankshaft is extended to carry a worm gear which drives the four legs via gearing and linkages.

The boiler is 24mm diameter x 30mm long. It is a little tricky to fill as there is no safety valve or filler hole. The whole vehicle has to be turned on it's side so that the boiler is upright. The main part of the boiler is then unscrewed from the end cap for filling.

The port face for the single acting oscillating cylinder is fixed directly to the boiler end cap. The cylinder is 6mm bore x 9.5mm stroke and exhausts directly from the side of the port face through a very short pipe. This exhaust pipe has a flare on the end, which may be purely decorative or it may be intended to facilitate oiling the piston. The crankshaft has a 30mm diameter flywheel at the end of the extension.

A worm gear is fitted between the crank and the flywheel. It meshes with a large gear wheel on the rear axle, which operates the two hind legs. The similar front axle is connected to the rear via a pair of gears. The ends of the two axles have small cranks which operate the linkage controlling the leg motion.

The entire chassis is formed from a single metal sheet, punched and bent into shape.

Make Microcosm
Model M23B Mini Cravling
Made 2018
Description Walking vehicle
Cylinders 1
Cylinder Type single acting, non-reversible
Piston Diam mm 6
Stroke mm 9.5
Valve Type Oscillating cylinder
Boiler Type horizontal
Boiler Diam mm 24
Boiler length/height mm 30
Fuel Meths
Mechanical Condition Good
Cosmetic Condition Good
Purchased 7/4/2018
Purchase cost 141.11
Additional spend