FURTHER EXPERIENCES OF H.T. GOVERNING
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FROM an engineering company of considerable prominence, but the name of which we are irt permitted to disclose, we have received some more -information relating to the governor device which functions by shortcircuiting the h.t. ignition current and which was outlined in a paragraph on our Patents page in our issue dated June 5.
A critical comment we made. about this device moused, considerable interest, and the views on it of a wellknown commercial-vehicle maker were included in our issue dated July 24.
The following enlightening remarks are based upon experience of a cut-out that has been used for some time on a large engine. The experimental engineer concerned, reports that the device is a most effective governor for limiting speed, but adds that "The Commercial Motor" criticism would be justifiable if the device were not extremely well designed.
He states that the centrifugal weight is a free fit in a glass tube and is frictionless, so that there is practically no hysteresis. This glass tulie, he points out, terminates in a large rectangular core, which obviates the possibility of tracking and electric leakage and efficiently ventilates the gap. Moreover, the whole of the weight mechanism, adjustment and securing screws are cip the earth side.
Explosions in tbe silencer are avoided by using a spring having a rate that prevents sudden cutting out. This, obviously, is under the control of the designer. In the same connection, the rate of deceleration of the engine under the influence of the governors must be less-khan the deceleration of the vehicle. All plugs should have their spark gaps set equally; otherwise the plug with the widest gap will cut out earlier than the others. Misfiring, when the governor acts, is intermittent because (a) the resistance of a spark gap varies, when an electrical discharge takes place, due to ionisation and (b) the mean path of the weight (owing to lack of friction) is a true circle with a wave frequency superimposed equal to the frequency of the loaded spring excited by the impact of the contact-breaker cam.
Unburnt mixture, exhausted from„ one cylinder, burns in the manifold or' exhaust pipe with the hot gas from an adjacent cylinder, sb no unbumt gas reaches the silencer, unless the vehicle overruns the engine down an incline at a speed approximately equivalent to the governed speed.