OMC-4 Rotative Engine – Series Three

OMC-4 Rotative Engine – Series Three

From: £ 149.00 £ 119.00

An example of an Edwardian engine and the early use of a rotor instead of a flywheel.


OMC-4 Rotative Engine. Series Three.

An example of an Edwardian engine and the early use of a rotor instead of a flywheel.

£ 149.00 £ 119.00

Round Hardwood Base – optional

Our round all hardwood base is offered as a replacement for the standard ebony black plastic base.

It measures 155mm (6in) overall and has a height of 30mm(1/14in). The top diameter is 120mm(4,3/4in) approximately

SKU: 1024-bundle Category:

Product Description

As the world entered the Edwardian era the early reciprocating electromagnetic engines had given way to revolving armature designs and to models using a rotor that incorporated the armatures.

Two Engineers, Harry Hawekotte and Henry Klausmann, both from Indianapolis, Indiana, developed such designs over one hundred years ago and our OMC-4, Series Three, Engine Kit is based on these designs and represents what was a significant step in the development of the electric motor.

Working on just 6 volts dc, this fully working electromagnetic Engine kit is assembled from approximately 130 parts but as no machining or soldering is necessary, this kit provides a satisfying experience for model makers of all abilities.


Building this Rotative Engine Kit into an operational model is all about the timing and three timing settings have to be achieved, highlighting the interaction between the armatures, the coils and that of the cam.

The challenge lies in getting the timing right and this is all part of the fun. The anticipation and end result of a functioning motor is both enjoyable and rewarding leaving the builder with a sense of achievement on completion.


With the armatures mounted within the rotor, a cam operated switching system ensures that the rods of the wound stators are energized as an armature approaches and after passing between them, switches off. The “cam” is a six sided component and establish six power pulses per rotation.

The “break piece” or contact points are mounted in a contact assembly and operated by the cam fitted to the shaft. This component is fitted to a moveable bracket within a fixed slide. This adjustable arrangement makes it possible to achieve minimum mechanical resistance at the cam and allows for further fine tuning with the timing plate screw that establishes how long the timing blades are in contact. Power is taken off via a pulley.

The timing blades are constructed of nickel silver and fitted with high quality silver nickel contacts to ensure long lasting and trouble free operation.

The early rotor incorporated in these Edwardian engines is a composite structure made up of two rotor discs that incorporate the armatures and up to 35 other parts.

Very detailed and illustrated assembly instructions are provided and the components are packed in numbered packages that correspond to sections in these instructions making the building process as simple and easy to understand as possible.

A Spares Packet of the smallest and most often mislaid components is included and a BA spanner tool is also supplied to assist the building.


This model is fitted with a fully working on/off switch of period design that incorporates a spring and ball. This switch makes it possible to easily demonstrate the engine.

Great attention to detail has been taken to ensure that all the parts are made in the style of the period. The elegant pillars supporting the shaft and the terminal connectors are all true to the times.

The model is produced from high quality brass, silver steel and zinc coated steel with copper windings on iron cores. The model is mounted on a hardwood base fitted to an ebony black period designed surround that conceals the battery box and other necessary modern considerations such as the diode that prevents sparking at the timing blades.

An optional all round all hardwood base is available at extra cost.

All the parts that are subjected to magnetism are constructed from Remco B Magnet Steel to prevent the build up of residual magnetism.

Technical Specification

The kit contains approximately 130 parts that need to be assembled. These parts are supplied in numbered packages that relate to corresponding numbers in the assembly instructions.

Very detailed and illustrated assembly instructions are provided.

No machining or soldering is necessary. Only hand tools are required. A BA spanner tool is provided in the kit.

The three piece base has an ebony black plastic surround and a hardwood base top that will need drilling (template provided). It will also need polishing or varnishing. A supportive base floor helps strengthen this structure and provides for placement of the feet.

The base measures 135 mm square (5,1/4 in) and the hardwood top is 100 mm square (4 in ). The height is 30mm (1/14 in).

The optional round all hardwood base measures 155mm (6 in) overall and is 30mm (1,1/4 in) high. The top diameter is 120mm (4,3/4 in) approximately.

The finished model stands 100 mm high (4 in).  The Rotor had a diameter of 60 mm (2, 3/8 in).

The timing system is adjustable with a moving bracket within a fixed slide with further fine adjustment possible with the timing plate screw which acts upon one of the timing blades.

The model operates on 6 volts dc and is supplied with a battery box that accepts 4 x AA batteries (not supplied).

A Spares Pack of the smaller and most often “mislaid” parts is included.

The Old Model Company Limited reserves the right to change the specification at any time without notice.

Health & Safety

This Model Kit is Not A Toy and is designed to be assembled by adults and responsible young people who are competent in the use of ordinary hand tools. The drilling of the wooden base should only be carried out by persons skilled in the use of a wood drill.