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Marklin Donkey Engine

1890s-1920s







This small engine is one of a range of similar engines made by Marklin. It was made and sold by Marklin as a stand-alone donkey engine but also as the motive power for other models, such as a crane, either stationary or on wheels (road or rail). It was also sold, in both forms, by other brands such as Bassett Lowke. This example has holes drilled in the base which suggest that it might have originally been a crane engine, but the holes are not threaded. It has been suggested that the holes may have been drilled as standard, even if the engine was sold as a stand-alone engine.

The cast iron base is a distinctive shape and supports the cylinder, boiler and crankshaft. The burner (missing in this example) sits under the boiler, surrounded by the bulk of the base. The boiler is 84mm diameter x approx 84mm high with a domed top. It has a single central flue. It has a water level try-cock on the side and safety valve & steam outlet on the top.

The steam feed goes via a reversing valve to the cylinder valve chest and a short exhaust pipe. The cylinder is mounted on the cast base in an inclined position and appears to be single acting. It is 15mm diameter (approx 14mm bore) x 15mm stroke. The piston rod is connected by a short con rod, with no cross head, to an oval crank web. The piston type valve is controlled by a fixed eccentric on the crankshaft. On the other end of the crankshaft is an 81mm diameter spoked steel flywheel and a 14mm diameter pulley.

As acquired, it was in very poor condition. The boiler had a large dent in the top and the safety valve was missing along with it's bush. The pipework around the reversing valve and cylinder was distorted and unsoldered. The reversing valve was jammed solid, but I was able to free it. The try-cock is still jammed solid and I have not been able to free it. I'm not going to try to force it as it's just as likely to break as to come free. The main steam pipe was nothing like the original, being over twice the right size! The screws holding the boiler onto the base were missing, as was the burner. The paintwork was in poor condition and the cast iron base was rusty, as was the crankshaft. Surprisingly, the steel flywheel was not badly rusted. I have repainted both base and flywheel.

The crank web was broken and the crank pin had been soldered in place, reversed and in the wrong position. The crank web is not easily removable so I have made a new web and soldered it to the old one, along with the crank pin soldered in place correctly (as far as I can determine). I've removed the dent on the boiler top and had new bushes made for the safety valve and steam pipe.

Unfortunately, the cylinder and piston were so badly worn that it wouldn't run atall on steam, and ran very poorly on compressed air.

I have since dismantled the cylinder and confirmed the piston is extremely worn. I've found that it has a deep groove, which was barely filled with thin cotton thread. I've replaced this with a good packing of graphited yarn and the engine now runs on steam, although not with much power.

Since these photos and video were taken, I have also fitted a temporary base and chimney.

Make Marklin
Model Donkey engine
Made 1890s-1920s
Description Donkey engine
Cylinders 1
Cylinder Type single acting reversible
Piston Diam mm 14
Stroke mm 15
Valve Type piston
Boiler Type vertical with flue
Fuel Meths
Mechanical Condition Fair
Cosmetic Condition Restored
Paintwork Restored
Packaging
Purchased 28/4/2017
Purchase cost 104
Additional spend 15