On modern earth-moving machinery - bulldozers, excavators and road graders, most or all of the functions are operated hydraulically. In Meccano, those hydraulics have to be simulated.

Somerville-Dennis simulated hydraulics are ideal for medium-sized models where ½" Ø Sleeve Pieces are the right scale for the rams.

Although not pure Meccano, they have the great advantage of being completely self-contained. No external mechanical drives, linkages or cables are needed, only an electrical connection. And unlike cable-and-pulley systems, the rams move the model and not the reverse.

The core of the system is the 6 volt Swiss Minimotor with integral 64:1 reduction gearing. This powerful, precision unit is also useful for other Meccano applications that need a very compact motor.

The ram components are: (a) MW Long Sleeve Piece (b) Minimotor (c) Motor Sleeve (d) End Piece (e) Cable Connector and bolt (f) Piston Sleeve (g) Lead Screw

Rams can be any length, minimum 2½". For rams more than 4½" long, two sleeve pieces can be joined using the Motor Sleeve (c) as a coupling. The Piston Sleeve and Lead Screw (f) and (g) are supplied as a pair in various lengths. The 4½" Sleeve Piece shown in Fig 1 has a corresponding 3 1/8" Piston Sleeve and Lead Screw.

On all rams, the piston stroke is 1 7/8" less than the length of the outer Sleeve Piece(s). The difference is significant only on shorter rams, which must be over-scale on the model to compensate.

For intermittent use, Minimotors will run on 12 volts, at which the pistons move at around 1" per second, near scale speed, and produce over 5 lbs of force. Limit switches are unnecessary as the motors tolerate stalling at ends of travel.

The right-angled Cable Connector (e) admits two sheathed wires through the hollow bolt to the inside of the Sleeve Piece for soldering to the motor terminals. Thin, multi-stranded wire from telephone extension cable is ideal for the purpose.

Illustrated is a 2½" ram on a 1:10 scale road grader. The wires are concealed inside a 4mm Ø sleeve to resemble hydraulic tubing. A recess is provided in the Cable Connector to hold the sleeve end.

Since 2004, the Minimotors used above have ceased to be available at an economic price for Meccano use, and Somerville-Dennis rams are consequently no longer in production.