BC Transit â Air Brake Course

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Bobtail Proportioning Systems Because a bobtail tractor has very little weight over the rear drive axles, it is very easy to lock up the rear brakes, even with a light brake application. To help prevent this unwanted lockup, and to increase control, some tractors are fitted with a bobtail proportioning system: •The system consists of two valves – one controls the steering axle brakes and the other the drive axle brakes. •When the tractor has a trailer attached, the tractor brakes work normally. •When bobtailing, the braking pressure to the drive brakes is reduced by as much as 75%, preventing the drive axle brakes from locking. •At the same time, the steering axle brakes receive full application pressure. •A tractor fitted with a bobtail proportioning system will stop in a shorter distance and control will be increased, especially on wet or slippery road conditions. 134
Tractor-Trailer Trailer Air Brake Systems The following slides will walk you through the air system, valve by valve and line by line. Please remember, these diagrams are not truly representative of the actual air piping arrangements. They are, however, taken from the “British Columbia Air Brake Manual” so that they will, perhaps, look somewhat familiar. So, let’s get started! 135
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BC Transit - Air Brake Course Prese
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BC Transit - Air Brake Course 1. Ai
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BC Transit - Air Brake Course 1. Ai
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BC Transit - Air Brake Course 2. De
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The final factor that will determin
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Weight - Speed - Distance When weig
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Perception Time (See-Think) Percept
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4/10 sec. Brake Lag (mechanical lag
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Stopping Distance…(total stopping
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Apply the principal from the previo
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Using Compressed Air to Our Advanta
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Combining mechanical advantage to a
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As the driver applies the brake ped
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Review Questions: Section 1 1) What
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BC Transit - Air Brake Course 3. Fi
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The Governor The governor may be co
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One-way Check Valve The one-way che
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Air Lines • Air lines link compre
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Safety Valve The Reservoirs One-way
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Air Gauges 60 50 40 70 80 85 90 100
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The Foot Valve The foot valve contr
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The Foundation Brakes: Brake Chambe
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Automatic Slack Adjusters Pre-Trip
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Brake Chambers and Slack Adjusters
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Review Questions: Section Three 1)
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BC Transit - Air Brake Course 4. Ba
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No. 2 GOVERNOR: tells compressor wh
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No. 4 AIR LINES: link air from one
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No. 11 BRAKE SHOES AND LININGS: sho
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No. 13 SLACK ADJUSTER: provides a m
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No. 15 BRAKE CHAMBER: part of force
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Quick Release Valve and Stop Light
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The Relay Valve The relay valve pro
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In this diagram, the dark green lin
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• Because the relay valve accesse
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BC Transit - Air Brake Course 4. Ba
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A spring type park brake serves thr
Page 83 and 84: However, some valves may be designe
Page 85 and 86: Park Brake and Service Brake Releas
Page 87 and 88: Park Brake Applied - Service Brake
Page 89 and 90: Mechanical Release of the Park Brak
Page 91 and 92: “Maxi-Brake” type Park Brake Th
Page 93 and 94: “Maxi-Brake” Operation (single
Page 95 and 96: Park brake systems with double cont
Page 97 and 98: Park Brake Emergency Functions... 1
Page 99 and 100: BC Transit - Air Brake Course 4. Ba
Page 101 and 102: No. 6 LOW AIR WARNING DEVICE: activ
Page 103 and 104: No. 8 RELAY VALVE: provides quicker
Page 105 and 106: Review of Section Four 6) Why is it
Page 107 and 108: BC Transit - Air Brake Course 5. Ot
Page 115 and 116: ATC (Automatic Traction Control)
Page 117 and 118: Long Stroke Push Rods Many new air
Page 119 and 120: Disc Brakes Callipers Rotor …oper
Page 121 and 122: Wedge Brakes This type of brake use
Page 123 and 124: Section Six Single Circuit Tractor
Page 125 and 126: Parts of the Trailer (van style) 1)
Page 127 and 128: The “Fifth Wheel” The fifth whe
Page 129 and 130: Hooking Up (Step 2) A visual inspec
Page 131 and 132: Charging the Trailer Brake Reservoi
Page 133: The Semi-Trailer Ready for its Pre-
Page 137 and 138: Introduction to Valves and Componen
Page 139 and 140: The Hand Valve The Hand Valve is mo
Page 141 and 142: The Tractor Protection Valve The Tr
Page 143 and 144: Accidental Hand Valve Application (
Page 145 and 146: The Trailer Supply /Delivery Line T
Page 147 and 148: The Emergency Relay Valve The Emerg
Page 149 and 150: Foot Valve Application (trailer con
Page 151 and 152: Emergency Functions The following s
Page 153 and 154: Supply Line Rupture (trailer intact
Page 155 and 156: Supply Line Rupture (handling the s
Page 157 and 158: Service Line Rupture (continued) 1)
Page 159 and 160: Loss of Main Reservoir Air In this
Page 161 and 162: Supply & Service Lines Crossed (air
Page 163 and 164: Three Tests to Confirm Emergency Re
Page 165 and 166: Three Tests to Confirm Emergency Re
Page 167 and 168: Review Questions Section Six (Tract
Page 169 and 170: BC Transit - Air Brake Course 7. Du
Page 171 and 172: The Purpose of Dual Air Systems Dua
Page 173 and 174: Identifying Primary and Secondary C
Page 175 and 176: Primary and Secondary Systems (cont
Page 177 and 178: The Simple Dual Circuit System One-
Page 179 and 180: Secondary Air Loss (Foot Valve Appl
Page 181 and 182: Adding the Park Brake (spring brake
Page 183 and 184: Primary Air Loss and Park Brake Fun
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Enter the Modulator Valve The modul
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The Modulator Valve (secondary air
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The Modulator Valve (primary air lo
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The Modulator Valve (primary air lo
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Dual Air System Summary 1) The purp
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BC Transit - Air Brake Course 8. Du
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Combination Truck and Trailer with
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SYSTEM PARK TRAILER SUPPLY TRACTOR
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Combination Truck and Trailer (Supp
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Combination Truck and Trailer (mixe
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Combination Truck and Trailer (Prim
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Section Review - Dual Air - Tractor
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T-75 Off Highway System - Single Un
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L-75 Off Highway Combination with S
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Schedule SX Trailer (spring equippe
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BC Transit â Air Brake Course