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SiriusRaw Power

Type: Horizontal, twin cylinder, banjo driven piston valve, high speed marine engine,
Bore 1 in
Stroke: 1 in
Height: 16 1/2-in.
Availability 1928-today
Design: Enclosed marine engine.

For Ordinary or Flash Steam Boilers

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Weight … … … … 6 1/2-lb.
Height … … … … 6-in.
Length of Crankcase … 5-in.
Width over fee… … … 4 1/2-in.

In the "SIRIUS," particular attention has been given to the
design of the valve gear and steam passages, with the result that the engine develops great power with a surprisingly low steam consumption. Our own tests show is developed at 2,800 at a steam pressure of 50-lb. steam very moderately superheated.
The Engine is a most interesting one to construct. No part is too small to handle easily ; it can be machined on a 3 1/2-in. lathe.


Cylinders Valve Chest of close grained cast iron ; very light cast iron Pistons with 2 rings each steel Crankshaft ; stainless steel Piston Valve ; gunmetal Bearings ; well-designed Connecting ; and machine-cut Gear Wheels.

Castings and Materials, all Screws, 4 Piston Rings and Cut Gear Wheels, and Complete Drawings … £4 12 6 (15/3)

Those who have not tools of the required accuracy, can purchase the Set of Castings with the … £5 10 0 (18/4)
finished Piston Valve and Valve Chest at

Complete Set of Parts fully machined, and all holes drilled and tapped fitted with … £10 17 0 (£1 16s. 3d.)
Displacement Lubricator, built and tested in our Works

Finished Engine fitted with Displacement Lubricator, built and tested in our Works. … £15 0 0 (£2 10s. 0d.)

Foreign Orders 'should include remittance for 10-lb. Postage.

Extras (add P/Tax)

Lubricator, 16/6 ; one pair Drain Cocks, 13/- : Steam Pipe Union, 222/4, 3/9 ; 1/4-in. O/D Steam pipe 1/3 per foot : 3/4-in. O/D Exhaust 1 /9 per foot ; Piston Rings, 3/- each.


This is basically a scaled up Sun engine. The casting layout is pretty much the same. The main body has Sirius cast in the side. Nubs on the casting for fitting condensation drain plugs as exhaust steam has to pass up through the steam valve casting. whearas exhaust steam passes down in the sun engine. The base is now a raised casting thaThe valve casting design is similar to the Sun but exhaust steam now passes to the top of the casting and exhausts through a pipe mounted on the front. The same arrangement of valve gearing and piston valve controlled by a baj]njo is the same as the sun. The crankshaft bearings are fitted to the ends of the main casting and the crankshaft is of the forged steel type also found on the Sun engine. A main difference is that the connecting rods have paddle like extensions out from the bottom that splash into the oil sump spraying oil all round inside the casting, this is why the base is raised to provide clearance.

During WW2 Stuart coupled the Sirius engine with an Alco generator to create a compact electrical generating set for use behind enemy lines to provide power for radios. The set fitted in a compact case and a boiler fitted in another box. The engine had a couple of additions to extend running time. The base casting had an extension added to which was fitted as brass riser tube and cap. This allow the oil sum to easily be kept topped up while running. A steam manifold was also added to the front of the engine with a pressure guage fitted on the right hand end. A condensation drain valve is also fitted. To secure the manifold to the main casting a bulge was added to the casting allowing a securing screw to be added. After the war some Sirius engines retained this bulge. Perhaps unused castings left over from the war production.

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A rather nice Sirius that has been fitted with drain valves and displacement lubricator.

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A nice cutaway Stuart Sirius engine. (quick note the right hand end of the piston valve shaft should be plugged.)

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Sirius castings note the corned castings with paddle extensions and the forged crankshaft.

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WW2 generating set for use behind enemy lines.

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WW2 generator Sirius showing extended base and lubricating tube. also the original steam flow valve.

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Same engine showing steam manifold, note mounting screw below middle.

Video Of Sirius


WW2 generating set.


A.W. of Kingston-on-Thames ;-
"May i say that the finish and workmanship to the 'Sirius" Engine were particularly gratifying."

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