APPLYING THE BRAKES BY SWITCH.
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A Simple Type of Electra-mechanical Servo Device Which Would Appear to Offer Many Possibilities.
AN unusual type of electrically operated brake was exhibited at the Graham Brothers' Show in Detroit during January, and it will be applied in future to trailers produced by the Warner Manufacturing Co., Beloit, Wis. The Warner Co. some time ago developed a metal-shoe brake with double-cam operation, and the electric method of operation is being combined with this brake, which is remarkably The brake drum has a fairly wide radial flange, opposite which is mounted an annular magnet supported by the spider of the brake mechanism. The face of the magnet is in sliding contact with' the &mg* on the drum. If an electrical currant be passed through the coil of the electro-magnet, this is attracted to the drum and the pressure between them creates friction which tends to revolve the magnet, the latter, being connected to the brake-operating cam, bringing the shoes into contact with the drum.
The device is really of the servo type, the electric part of the equipment being employed merely to bring the friction surfaces of the servo device into intimate contact, after which the revolving wheels themselves cause the application of the brake shoes. It is stated by "Automotive Industries " that the electric energy required to apply the brake is comparatively little, for the magnet does not have to apply the brake direct, and there are no air gaps to reduce the strength of the
magnetic flux, as the magnetic circuit is always closed, is of large section and short length, and the magnetic pull of a magnet depends upon the number of lines of magnetic force passing from it into the keeper.
Tire electric brake is applied either through a pedal or separate lever. The current is obtained either from the electric system of the vehicle or a special storage battery. It is passed through a rheostat, and the harder the pedal or lever is pushed or pulled, as the case may be, the more current will flow and the stronger will be the application of the brake. The releasing action is said to be quick.
A contact for the, brake is automatically established through a connection in the trailer king-pin, the tractor, of course, being suitably wired for the purpose.
If such a brake as this proves satisfactory in ordinary usage, it would appear to do much towards solving the difficulty of trailer braking. The apparatus appears to be unusually simple, and there appears to be no reason why it should not be thoroughly efficient The only doubt which may exercise the minds of some users is asto whether it is advisable to add still more to the call upon electric batteries, particularly if these ac used also for starting, lighting and operating electric horns, etc.