A Short Analysis of Traction Engine Governor Spring and Fly Weight Design

| November/December 1993

Coil spring governor

7490 Woodridge Lane, Bremerton, Washington 98310

There are two common types of spring balance governors used on traction engines. They are distinguished by the manner in which the spring balances the centrifugal force of the rotating weights. The first, and most easily resolved, is the coil spring governor, which uses a coil spring, generally around the throttle rod, to resist the force induced by the fly weights' tending to move outward as they rotate. Figure (1) is a line diagram of one weight assembly of a coil spring governor. The other prominent type of governor utilizes a flat (sometimes called a single leaf) spring to resist the outward movement of the fly weights. Figure (2) is a line diagram of one weight assembly of a flat spring governor.

First let's investigate the simpler of the two for evaluation, the coil spring governor. This system operates by movement of a vertical throttle valve rod up and down in response to the radial movement of the fly weights. The position of the fly weights is, in turn, governed by the centrifugal force caused by their rotation balanced with the force in the compressed spring.

The equations pertinent to the coil spring governor are as follows:

Resistive force in the spring; (1)

       1       WrN2
P= -(n) (-)
      4x      2933