Electric Exhaust Brakes: New Developments
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New Pedal Switch for Ashanco Electric Exhaust Brake for Use with Air Sistems : Eight Types of Brake Unit Now Offered IT is understood from Thomas Ash
and Co., Ltd., Birmingham, 5, that a highly sensitive type of exhaust brake ,pedal switch has now been designed for use with air-brake systems, thereby obviating the risk of the wheel brakes being applied needlessly. Although there is not much chance of this occurring with most braking systems, some of the latest equipment, such as the BendixWestinghouse D1 brake valve, requires only slight pedal movement partially.to apply the wheel brakes.
Sensitive New Switch To overcome this difficulty,. a new switch with a repositioned fulcrum and lighter operation (a pressure of lb. is sufficient) has been evolved._
The main body and blade of the brake are made of malleable iron and, to suit different exhaust-pipe sizes, mating flanges with varying sizes of bore are supplied.
The basic design is identical, however. and consists of glass-insulated • solenoid windings contained in a mildsteel casing. The solenoid plunger, which actuates the valve plate, is chromium-plated to prevent corrosion and it is carried in a self-lubricating
sleeve vvhich does not require attention during the life of the unit.
The solenoids are tested in a temperature of at least 1,000° F., which is far higher than the exhaust-pipe temperature, so that failure from heat is most improbable. On earlier versions of this equipment a light metal shield was fitted around the actuating linkage adjacent to the solenoid, but this has now been dispensed with to avoid the chance of a heat build-up affecting the operation of the unit.
By employing electric operation, the Ashanco system has the great advantage that its power is derived from a source common to all road vehicles—the battery. Consumption is low, a 3-in. unit for a 24v. circuit using 4 amp. and a 4-in, unit consuming 5 amp. There is, furthermore, a slight drop in the current consumption as the operating temperature rises.
Simplicity is the keynote of the pedal control-switches supplied with the gear. They' consist of a plain plunger-switch, operated by a hinged moulded-rubber pad and mounted on a baseplate. The strength of the switch spring can be varied to suit different systems.
• There are now eight principal types
of brake unit. Marks I and 11 are for use with oil engines with mechanically or hydraulically governed fuel pumps.
With these governors, the pump control rack returns to the fuel cut-off position automatically, therefore no provision has to be made for cutting off the fuel when the switch is applied. A small clearance is provided between the brake valve and the body to allow a slight flow of exhaust gas when the valve is shut and thereby prevent the engine from stalling.
Pneumatic Governing Marks HI and IV are used on pneumatically governed engines incorporating a manual stop control. An Arens cable is introduced between the valve lever and the pump stop-lever to cut off the fuel feed, and a solenoid stop device is used for cutting out the engine completely.
The other four models have been designed for pneumatically governed engines with solenoid stop controls; these also have an Arens cable control for cutting down the fuel when the exhaust brake is in operation. The difference between the marks of each different type is voltage (12 or 24).
Fitting any of these units is relatively simple and consists essentially of cutting a section from the exhaust pipe, Welding new flanges to the pipe and drilling the brake pedal to take the switch attachment. Any fuel-injection pump modifications that may be necessary can be carried out by the service departments of the pump manufacturers.