Stationary Engine Kits
Anthony Mount Models
James Booth's Rectilinear Engine 1843
This unusual engine was patented by James Booth in 1843. His hopes for the design were that it would give a compact layout for use in paddle ships, and for driving machinery on land.
The term rectilinear derives from the action of converting reciprocating motion to rotary. As you can see from the picture, this was accomplished by a set of links, connected to the crossheads. The crossheads run in guides in the form of a cross. The reciprocating motion of the piston drives one end of the link, connected to the vertical crosshead. The other end of the link is connected to the horizontal crosshead, which is pulled across. The combined motion pulls the centre of the link around in a circular path. Attached to the centre of the link is the crank from which is derived the rotary motion. This arrangement removes the need for a connecting rod, which greatly reduces the height of the engine. However is does increase the number of rubbing surfaces. I have been unable so far to determine if the engine was ever built full size.
The design of the model was developed from the patent drawings. It follows fairly closely the spirit of the prototype but some details had to be guessed at as their arrangement was not shown. A standard slide valve is used for steam distribution. A main stop valve is also incorporated into the design, and sits adjacent to the valve chest.
Construction is straight forward, but care is required to ensure that the guide frames line up on the centre line of the crankshaft. The flywheel is 9” (225mm) diameter which allows for machining on a Myford series 7 lathe. Machining follows the usual model engineering processes and most can be done on the lathe. It is of course easier if a drill and milling machine can be used as well.
Castings are required for Flywheel, and pulley which are in cast iron, cylinder, covers, piston, steam chest, eccentric strap and guide frames are in gunmetal. The bearing frames being in aluminium. The base is a 3/16” (5mm) thick mild steel plate. Other parts are machined from rod and bar material. There are 20 drawings in the set, plus a parts list. They are dimensioned in imperial and metric. Some of the conversions are not exact, as standard material sections have been used where possible.
The model was serialised in Engineering In Miniature, from December 1989 to October 1990. The engine when built is fascinating to watch, the motion is really unusual. It appears as if the flywheel is revolving one way and the links are revolving in the opposite direction.