Los Angeles County Metropolitan Transportation Authority CTA - - PowerPoint PPT Presentation

CTA November, 2015 Pasadena, California Bus Technical, Maintenance Workshop

By: Frank Forde Maintenance Instructor LA Metro

Los Angeles County Metropolitan Transportation Authority

Los Angeles Metro Facts FY15

Metro Bus Operations Statistics

• 327 million boarding's
• 85 million revenue service

miles

• 2,252 buses in active revenue

service

• Extreme Duty Cycle
• 35,000 to 45,000 yearly bus

miles

• 11 mph average system speed

Los Angeles Metro serves one of North America’s largest and most heavily congested counties, with over 10 million residents and a service area of over 1,433 square miles.

Los Angeles Metro Facts

• 2,252 buses on property

– 1849 buses in daily peak service

• 1,750 disc brake equipped buses

– 650 45’ transit buses – 700 40’ transit buses – 391 60’ articulated buses – 7,770 wheel ends

• 502 S-cam drum brake buses

Disc Brakes

• LA Metro has two manufacturers of air disc brake on it’s

fleet .

• Air disc brakes have been in operation at LA Metro since

2004 – Meritor EX225 air disc brake 2004 – KNORR SN7 air disc brake 2014

Why Disc Brakes?

• Reduced Maintenance Cost
• Reduced number of part numbers equal less parts to stock
• Reduced drag and rolling resistance resulting in faster acceleration.
• No loss of brake power due to overheating
• Higher residual brake force after repeated braking.
• Brake disks can withstand extremely high temperatures.
• Brake fading is almost completely eliminated.
• Simply a more efficient way of braking.

Disc Brakes Service Intervals

• Disc Brake Average Mileage:

– 45’ transit bus = 40,000 miles – 40’ transit bus = 40,000 miles – 60’ articulated bus = 35,000 miles

• Pad Replacement: 4 labor hours per axle
• Pad and Rotor Replacement: 8 labor hours per axle
• Mileage average same for all axles
• Brake reline mileage is enhanced by the transmission retarder

– Aggressive retarder-longer brake life. – Allison Gen 4 / 5 transmission retarder is medium capacity, resulting in lower brake life.

System Operation

• Air caliper actuated pads. The application force is amplified by the

design of the caliper shaft.

• Floating caliper design; the inboard is applied by the caliper force;

the outboard pad is applied by the floating housing pulling against the rotor.

System Operation

• The automatic adjuster makes an adjustment to the operation of the brake pads

to compensate for pad wear.

• Each time the brake is applied, the system senses whether adjustment is required
• r whether the disc-to-pad running clearance is still within the built-in tolerance.

Meritor EX225 caliper visual brake pad wear indicator

Visual Wear Indicator

KNORR SN7 caliper visual brake pad wear indicator

Visual Wear Indicator

Rubber boot type with axial ribbing indicator . This bushing if fully extended showing a new pad condition This bushing is almost fully retracted indicating a worn pad and /

• r rotor

• For service procedures – consult service manual
• Use only OEM spare parts
• Do not open caliper assembly, as this voids the warranty.
• Never actuate the brake while pads and/or rotor are removed from the assembly.
• Do not re-surface the rotor when replacing brake pads.
• Remove rubber plug located on the bottom of the actuator service brake.
• Do not use any tool on the brake adjuster screw other than a closed box wrench or

1/4” drive ratchet.

• Do not lay the caliper on the outer boot when servicing the caliper off the axle.

Metro General Service Recommendation

Q & A

Contact:

Frank Forde 213-922-5928 fordef@metro.net