Manual Supplement

Vacuum Brakes for 1 1/2" Scale Freight Trucks

Catalog Number 15T14C

Overview

This manual supplement contains the additional information needed for trucks that have been delivered with brakes installed

Brake Connection

These trucks are furnished with a complete vacuum brake system installed (less plumbing). The design of this system uses two vacuum diaphragms per truck. This is not done because these trucks required additional mechanical force compared to other designs. The two diaphragms allow increased travel of the shoes at the same force commonly used. The increased travel allows the shoes to move completely away from the wheels when retracted, preventing unnecessary wear and drag. The increased travel also allows more wear between brake adjustments.

It is critical that the brakes on these trucks be coordinated with other brakes used in the same train. The overall system must provide the required braking force for the heaviest possible load while not causing wheel slippage in empty cars.

The connection to the vacuum diaphragms uses what is known as a 3/16 inch male J flare fitting. These are most commonly found in automotive suppliers but may be available elsewhere. If you would like a more standard fitting we offer an adapter from this fitting to standard 1/8 inch pipe (see parts list) which allows connection with standard plumbing fittings. In connecting your vacuum system be sure that the hoses to the truck are very flexible and that they do not catch or drag against anything when the truck rotates in corners. Test the hose that you plan to use to make sure that it will not collapse under vacuum (some very strong hoses for pressure use will not work on vacuum).

Maintenance

Disassembly/Reassembly

Trucks with brakes require additional steps for disassembly in addition to those listed in the manual provided with the trucks. The steps also differ depending on which type of truck is be worked on.

Modern Roller Bearing Trucks - If wheel and axle assemblies are to be removed by removing the retainers it is first necessary to disconnect the clevis from the brake beam. If removing a side frame from the bolster and wheel/axle assemblies you must first unscrew the brake pivots from the side frame, and then removing the springs from that same side frame.

Steam Era Plane Bearing Trucks – To remove a side frame you must first disconnect both clevis from their brake beams. You must then remove the bolts holding the bracket to the bolster and slide it to the side away from the side frame being removed. Then remove the springs from that side frame.

Arch Bar Trucks – To completely disassemble the truck you must first disconnect both clevis from their brake beams. Using a hex wrench with a very short arm reach above the spring plank and remove the four bolts holding the two brackets on one side to the bolster. With the brackets removed, remove the springs. Then turn the spring plank at an angle into the space made available by the removal of the brackets and slide it out through the openings in the side frames. Now remove the bolts and the other brackets. Turn the bolster at a forty-five degree angle but leave it in place. Remove the brake hangers from at least one side frame and remove the side frame, then the wheel/axles assemblies and the bolster.

For spring removal please see the truck manual or (if leaf springs are installed) the leaf spring manual supplement.

Reassembly uses the same steps in reverse. When reinstalling the brake pivots or other bolts, do not over tighten them. The trucks are furnished with all threads coated with a "small screw" (low strength) retaining compound. This is available from our parts list or local suppliers and is recommended for use.

Brake Inspection and Adjustment

All brake components should be inspected to make sure that they operate freely but without excessive play. Brake shoes should be inspected for wear by measuring their thickness at the top and bottom. If less than 1/8" (3mm), or if the operating mechanism cannot move them tightly against the wheels at maximum adjustment, they should be replaced. Also inspect all hardware for tightness and all vacuum plumbing and hoses for leaks, chafing, or deterioration.

The brake system must be adjusted periodically to compensate for wear. This is done by threading the brake clevis further on (or off if too tight) the rod that is part of the vacuum diaphragm. Proper adjustment is obtained when, without vacuum applied, the brake shoes, when pivoted fully downwards, are approximately 1/8" to 1/16" (3.2 to 1.6mm) away from the wheels. Clearance greater than this amount can cause the brake hangers to swing together and contact the sides of the bolster (this will not cause damage because the shape of the hangers will result in their being forced apart by the bolster) resulting in possible wear or marking. The adjustment should then be checked to make sure that the shoes can fully contact the wheels when the brakes are applied.

To adjust the clevis it is necessary to be able to turn it. First remove the brake spring. Then remove the clevis bolt and clevis nut, and while pulling the brake beam away from the wheels, slip the clevis off of the beam. When doing this do not apply excessive force to the rod coming from the vacuum diaphragm unit or damage to the unit may result. If you cannot move the clevis clear of the beam so that it may be turned for adjustment using this method, it will be necessary to remove the vacuum diaphragm from the brackets by removing the bolts, nuts and washers holding it. When turning the clevis on the rod do not twist the internal components of the vacuum diaphragm. If resistance is felt, hold the rod with pliers when turning the clevis. After adjustment, reassemble any items disconnected in reverse order. To prevent having to do this a number of times to make one adjustment you may measure the amount of change needed (at least approximately) and then use this value when rotating the clevis. Each full turn of the clevis on the rod changes the adjustment by 1/32" (0.8mm).

Lubrication of the brake system is not required and not recommended because of the possibility of ending up between the shoe and the wheel. The brake pivot spacer is porous bronze and provides lubrication. It may be soaked in oil and then wiped dry if necessary after long use. The zinc coating on the brake beam combined with the natural bearing effect of cast iron brake shoes normally keeps this joint free.

Brake Shoe Replacement

For brake shoe replacement, remove the cotter pin and washer. Then remove the brake pivot from the side frame using the method above. This will allow the brake shoe and brake hanger to slip off the end of the brake beam. Replacement uses the same steps in reverse order. When reinstalling the brake pivots do not over tighten them. The trucks are furnished with the threads of these pivots coated with a "small screw" (low strength) retaining compound. Use of a new cotter pin is recommended.

Replacement of all other brake components is possible by the same steps detailed above.

Parts Diagram and List

Below general views of a typical truck with "key letters" pointing to each specific part. Your truck may differ in design but will have similar parts in similar locations. These keys are indexed to the parts list that follows which also gives the part name, part number, and quantity per truck (double quantities for one car, two trucks). Listed separately are assemblies, packages and special tools.

KS3.EPS

KE3.EPS

KX3A.EPS

KX3B.EPS

Individual Parts

Notes:

1. – Not used on arch bar trucks
2. – Used only on arch bar trucks

Optional Parts, Parts Packages, Assemblies, Tools

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