The use of rapidly rotating machinery in electric lighting has created a demand for engines running from 400 to 1,200 revolutions per minute, and capable of being coupled directly to a dynamo machine. We have already illustrated several forms of these engines, and now publish engravings of another in which the most noticeable feature is the employment of separate expansion valves and very short steam passages. Many high-speed engines labor under the well-grounded suspicion of being heavy steam users, and their want of economy often precludes their employment. Mr. Chandler, the inventor of the engine illustrated above, has therefore adopted a more elaborate arrangement of valves than ordinarily obtains in engines of this class, and claims that he gains thereby an additional economy of 33 per cent. in steam. The valves are cylindrical, and are driven by independent eccentrics, the spindle of the cut-off valve passing through the center of the main valve. The upper valve is exposed to the steam on its top face, and works in a cylinder with a groove cut around its inner surface.

As soon as the lower edge of the valve passes below the bottom lip of the groove, the steam is cut off from the space between it and the main valve, which is fitted with packing rings and works over a latticed port. This port opens directly into the cylinder. The exhaust takes place chiefly through a port uncovered when the piston is approaching the end of its stroke. The remaining vapor left in the cylinder is exhausted under the lower edge of the main valve, until cushioning commences, and the steam from both upper and lower ports is discharged into the exhaust box shown in Fig. 2. The speed of the engine is controlled by a centrifugal governor and an equilibrium valve. This is a "dead face" valve, and when the engine is running empty it opens and closes many times per minute. The spindle on which the valve is mounted revolves with the governor pulley, and consequently never sticks. To prevent the small gland being jammed by unequal screwing up, the pressure is applied by a loose flange which is rounded at the part which presses against the gland.

The governor is adjustable while the engine is running.

IMPROVED HIGH SPEED STEAM ENGINE.

IMPROVED HIGH SPEED STEAM ENGINE.

Another economy claimed for this engine is in the use of oil. The cranks and connecting rods work in a closed chamber, the lower part of which is filled with oil and water. The oil floats in a layer on the surface of the water, and at every revolution is splashed all over the working parts, including the interior of the cylinder, which it reaches through holes in the piston. The oil is maintained exactly at one level by a very ingenious arrangement. The bottom of the crank chamber communicates through a hole, C, with an outer box, which receives the water deposited by the exhaust steam. The level of this water is exactly determined by an overflow hole, B, which allows all excess above that level to pass into an elbow of the exhaust pipe, out of which it is licked by the passing steam and carried away. Thus, as the oil is gradually used the pressure of the water in the other leg of the hydrostatic balance raises the level of the remaining portion. When a fresh supply of oil is poured into the box, it forces out some of the water and descends very nearly to the level of the hole, B.

The engine is made with either one or two cylinders, and is, of course, single-acting. The pistons and connecting rods are of forged steel and phosphor-bronze. The following is a list of their sizes:

 Single Engines.

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Brake | | | | |

Horsepower| Bore of | Revolutions| | |

at 62 lb.| Cylinder. | per minute.| Height. |Floor Space.|

Boiler | | | | |

Pressure. | | | | |

----------|-----------|------------|---------|-------------

| in. | | in. | in. in. |

2¼ | 4 | 1,100 | 26 | 14 by 14 |

3½ | 5 | 1,000 | 28 | 14 " 15 |

6 | 6½ | 800 | 30 | 16 " 16 |

10 | 8 | 700 | 32 | 18 " 18 |

----------------------------------------------------------- Double Engines.

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Brake | | | | |

Horsepower| Bore of | Revolutions| | |

at 62 lb.| Cylinder. | per minute.| Height. |Floor Space.|

Boiler | | | | |

Pressure. | | | | |

----------|-----------|------------|---------|-------------

| in. | | in. | in. in. |

4½ | 4 | 1,100 | 26 | 14 by 20 |

7¼ | 5 | 1,000 | 28 | 14 " 20 |

12 | 6½ | 800 | 30 | 16 " 26 |

20 | 8 | 700 | 32 | 18 " 32 |

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The manufacturer is Mr. F.D. Bumstead, Hednesford, Staffordshire. - Engineering.