﻿GET_GEVOMechL2_06_01_01_71 - ANIMATION Screen
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You have reached the end of this module!

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In this module, you learned to:

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State the purpose and location of the high adhesion truck.

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The purpose of the high adhesion truck is to distribute the locomotive’s weight equally over the axles, transferring the tractive effort (pulling force) and braking effort (stopping force) from the locomotive to the rail.

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Two high adhesion trucks support the entire locomotive.

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Describe the basic operation of a high adhesion truck.

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The high adhesion truck contains 3 axles and wheel sets.

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A traction motor powers each axle and is coupled to the axle through a U-Tube assembly and a reduction gear arrangement.

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The U-Tube wraps around the axle and is mounted to the traction motor.

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Two roller bearing assemblies within the U-Tube allow the axle to rotate freely.

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The reduction gear arrangement consists of a small pinion gear and a large bull gear.

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A gear case surrounds the pinion gear to keep out dirt and moisture and to retain necessary gear lubricant.

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When electrical power is applied to the traction motor, the pinion gear turns the bull gear.

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The bull gear turns the axle which in turn, causes the wheels to rotate.

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Describe the major components of a high adhesion truck.

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One side of each traction motor is physically mounted to the truck frame by means of a motor nose support.

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The truck frame is supported at each end of each axle by means of two coil springs, an axle or journal housing, and an axle or journal bearing.

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The bearing is pressed onto the end of the axle.

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The axle housing surrounds the bearing and holds the two coil springs.

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The other end of the coil springs hold up the truck frame.

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Two vertical snubbers, also referred to as primary shock absorbers, are located on one side of the truck to reduce unwanted vertical oscillations.

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Forces between the truck and the locomotive platform are transmitted through the truck's traction pin bearing assembly to the platform's traction pin.

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Four loadbearers support the vertical load of the locomotive and also allow for lateral motion between the platform and truck frame.

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Unwanted movement is lessened by the primary shock absorbers, lateral shock absorbers, and yaw shock absorbers.

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Brake cylinders, brake rigging, and brake shoes provide braking at each of the six truck wheels.

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Describe how to perform running maintenance inspections on the truck and its major components.

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Wheels

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Periodically inspect the wheels for damage or excessive wear, in accordance with Federal Railroad Administration Regulations.

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Shimming

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The use of shims allows greater differences in wheel diameters between wheel sets while keeping axle loading more uniform.

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Shims are inserted between the coil springs and the spring pads.

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Pedestal Liners

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To check the longitudinal clearance, with a tapered gauge, measure the gap between the long-side face of each pedestal liner and the journal housing.

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The sum of both measurements is called the total longitudinal gap and it should not exceed 1/2 inch.

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To check the lateral clearance, with a tapered gauge, measure the gap between the short-side face of each pedestal liner and the journal housing.

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This is called the lateral gap.

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If the pedestal liners are damaged or if clearances exceed the maximum limits, replace them as follows:

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1. Remove the bearing housing retainer and then remove the damaged or worn liner.

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2. Install the new pedestal liner and retainer, then torque the retainer bolts to the proper value.

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Brake Shoes and Rigging

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The brake shoes are a high-wear item and must be inspected on a regular schedule and replaced as follows:

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1. Chock at least two sets of truck wheels and release the hand brake.

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2. With the locomotive secure, locate and close the truck air cut-out cock on the underside of the locomotive frame.

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3. Move the brake shoe as far as possible from the wheel tread, then remove the retaining key and worn brake shoe from the brake head.

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4. Install a new shoe in the brake head.

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5. Reinstall any pins that were removed and lock them into place.

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6. Open the truck air cut-out cock.

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Adjust the brake system as follows:

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1. Chock at least two sets of truck wheels and release the hand brake.

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2. With the locomotive secure, locate and close the truck air cut-out cock on the underside of the locomotive frame.

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3. Adjust the slack adjuster, replace the slack adjuster pin, and rotate the pin retainer.

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4. Open the truck air cut-out cock.

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5. Apply and release the air brakes at least twice to check for proper operation of adjusted air brakes.

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6. Check the brake-cylinder piston-rod travel and brake shoe-to-wheel clearances at ALL truck wheels.



