Steam engine's valve-gear

Stephenson's link motion

Each slide valve is equipped with two eccentrics, one for ahead and another for astern. By shifting the position of a quadrant you can get one or the other of the eccentric rods to operate the slide valve rod. A steamer with Stephenson's link motion have the slide valves placed at the engines ends and/or between the cylinders and therefore the engine is longer than if it had had horizontal eccentric rods.

Stemship with Stephenson's link motion

Hackworth's valve-gear

The Hackworth's valve-gear differs from the Klug's valve-gear in the way that the eccentric rod's suspension point, in stead of vacillate in a curve, moves to-and-fro in a straight line by means of a block sliding in a slotted guide. Changing the angle of the guide rails changes the engine's rotation.

Stemship with Hackworth's valve-gear

Klug's valve-gear

Klug's valve-gear has a horizontal eccentric rod suspended in a pendulum and the eccentric rods end is by means of a link connected to the slide valve rod. Changing the pendulums suspension point changes the engine's rotation.

Stemship with Klug's valve-gear

Flodman's valve-gear

Flodman's valve-gear has a horizontal eccentric rod suspended in a pendulum and it works the same as the Klug's valve-gear, but the pendulum and the link to the slide valve rod have swaped places. However, the mechanism that moves the pendulums suspension point, is quite differently. Flodman's valve-gear seems to be most used on Swedish steam engines.

Stemship with Flodman's valve-gear

Carlsund's thread

The crankshaft is provided with longitudinal slots. A casing, yellow on the picture, connected to the eccentric is provided with thread-like slots. An outer axially movable casing with a number of concentric rings is provided with blocks, blue on the picture, that slide in the slots of the eccentric-casing as well as the slots of the crankshaft. A pinion moves the outer casing axially, as a rack gear, and that movement turns the eccentric on the crankshaft and the engines rotation reverses.     Stemboat with Carlsund's thread

Caprotti's valve-gear

The innovation of the Italian Arturo Caprotti replaces the old slide-valve system with a device, borrowed from the internal combustion engines, which opens poppet valves controlled by cams on a camshaft. The steam is hereby very precisely introduced into the cylinders and easily variable over a wide area.
The camshaft is provided with thread-like slots, as you can see on the pictures below, that changes the cams position on the camshaft in the very same way as the eccentric do in the Carlsund's thread , system from 1867.

Stemship with Caprotti ventilstyrning

Stompf's unidirectional system

A cam on a camshaft, opens the steam inlet seat-valve a short time. When the piston reachs its other end position the steam is drained from the cylinder through the steam outlet chanal. When steam is introduced on the other side of the piston it moves to its first end position, compressing the residual steam.

Stemship with Stompf's valve-gear

Gooch's valve-gear

Gooch valve-gear is very similar to Stephenson link-motion. The only difference is that the quadrant is fixed to the centre position by means of a link and an intermediate link between slide-valve-rod and quadrant can be moved to let either of the eccentric-rods actuate the slide-valve-rod via the intermediate link..

Stemship with Gooch's valve-gear