Document bO0zBm9d0eX6xaLRnYgOZv9b0

'ru ,r linings that prove worthy in the laboratory receive further testing'. ROAD TESTING W BRAKE LININGS As is true of all automotive development, the vehicle itself must produce the final verification of laboratory brake findings. Large fleets of vehicles and numerous engineering personnel are continually engaged in brake development and test ing operations (Fig. 7). Tests of every type of Chevrolet brakes totaled 1,680,000 miles from October 1957 tc October 1955. Th> results of brake road tests described herein apply to organic lining bonded tc thu shoes, as contrasted to the riveted type, both of which are shown in Fig. r. Tetts :n metallic linings apply to the type shown in Fig. 9. with the lining riveted tc the shoes in segments. The metallic segments on the shoe are flex ible in their application in that they can be varied in number, position on shoe or material for-ruia tc. produce the braking effort desired. The ultimate structure of all linings is determined by test. A brake lining mater-a I -that has progressed from laboratory to road testing first undergoes a n general : ^el!' test. Brake development engineers try the facings for an overall impress!cn. If tne findings are good, an effectiveness test is made. The 50 and 80 mph brake deceleration test results shown in Fig. 10 depict the effectiveness of high speed emergency stops with organic and metallic linings. This test requires the use of a load applicator, decelerometer and recording unit. Load is applied to the brake pedal automatically and the recording unit indicates pedal load, deceleration, pedal travel and time required to make test stops. The 50 and 80 mph brake deceleration curves show the orake effectiveness of the organic and metallic linings. The rate of load application on the brake pedal to obtain the curves is 30 pounds per second and each curve repregents a single stop. The curves reveal that the organic material is less speed sensitive and more effective in this test. It should be pointed out that the metallic lining curves are those In which the brakco were cool at the start of the stop. For the organic lining, the pedal load required at a deceleration rate of 20 feet per secend per second from 50 mph is 80 pounds, and from 80 mph is 118 pounds. Under the same conditions for metallic lining, the pedal load from 50 mph is 103 pounds, and from d-0 mph is 165 pounds. I..' linings perform well in the effectiveness test, they are subjected to the fade test. The chart in Fig. 11 illustrates a brake fade test comparison of or ganic and metallic linings, line pressure is indicated by the co-ordinate at the left and stop numbers at the bottom of the chart. The stops were made from 60 mph at 15 feet per second per second deceleration. The interval between fade stops was L-tenths of a mile, or about uO seconds. Initial feel and recovery stops were made from 10 mph at i feet per second per second at one mile intervals. The organic curve shows a slightly decreasing initial to final line pressure during the first three stops with each successive stop becoming harder. This is indicated by the shaded distance between the broken and solid line curves. By the Uth stop the line pressure increases progressively during each stop and the pedal becomes harder. By the 7th stop, line pressure is over S00 psi and fade continues with each stop. Recovery is slow and requires miles tc level out to within 20 pounds per square inch of the initial. As the metallic lining curves indicate, the line pressure increases only 5'.- pounds per spuare inch during entire test. The line pressure decreases during eacn stop with mo recovery being required. Tests such as this show the need for 5"gani: li: ings that have less heat build-up and, thereby, less fade. Therefore,