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BULLETIN PLAINTIFF'SEXHIBIT
AUGUST 18. 1978
No. Q95a under BRAKES
FOR BRANCHES, DISTRIBUTORS AND CUSTOMERS.
CHASSIS AFFECTED ALLENTOWN0 HAYWARDtZf OAKVILLELZf
BRAKE INTENSIFIER (All With Air Over Hydraulic Disc Front Brakes)
PURPOSE To provide the field with procedure for changing intensifier pressure ratio from 23. 5 to 1 to 17 to 1.
RECOMMENDATION Follow procedure outlined herein when changing intensifier ratio. This modification is permissible on highway vehicles with a bogie rated at 55,000 pounds or less.
INFORMATION Improved service life of disc front brakes has been achieved in many cases by changing the intensifier ratio from 23. 5 to 1 to 17 to 1. This change lowers the hydraulic system pressure and reduces amount of braking force developed by the disc brakes.
As pointed out in Bulletin Q95 under BRAKES, 23. 5 to 1 and 17 to 1 intensifiers are directly interchangeable as assemblies, making it possible to install a complete 17 to 1 intensifier to effect a ratio change.
It is possible to convert a 23. 5 to 1 intensifier to the 17 to 1 ratio by installing the smaller Rotochamber used on the low ratio unit. This latter method is less expen sive and is recommended if the master cylinder is in good condition.
A switch is mounted on the chamber which actuates a warning light if there is a failure in the hydraulic system. This switch is the same for both intensifier ratios and can be transferred from old to new assembly. Part number of the switch is listed in case ex isting switch is not useable.
Parts required:
Qtv. Part No. 1 745-286757
* 1 1MR2321
DescriDtion Rotochamber, Type 36 Warning Switch
* Required only if existing switch is not serviceable
CIRCULATION
Service Manager
Shop Foreman
Night Foreman
Night Foreman
Inspector Leadman
Inspector leadman
Inspector Leadman
Unit Over haul Room
(Continued Over) Service Operations, Allentown, Pa. U. S.A.
Shop Office
Mackz
Procedure - Refer to illustration
1. ROTOCHAMBER 2. WARNING SWITCH 3. MASTER CTUNOER 4. MASTER CYLINDER MOUNTING BOLTS
The intensifier can be removed from chassis as an assembly, or in many cases, the Rotochamber can be separated from the master cylinder without removing cylinder from chassis or disconnecting the hydraulic line. Where space permits, the latter procedure is recommended as it eliminates necessity of bleeding the hydraulic system. It is important to support the master cylinder by some other means if it is left in the chassis, to prevent damaging the hydraulic line. Regardless of which method is used, first disconnect air line from Rotochamber. If the master cylinder and Rotochamber are to be removed as an assembly also disconnect the hydraulic line from master cylinder. The intensifier can be re moved as an assembly at this point by unbolting mounting brackets from frame.
If the master cylinder is to be left in chassis, remove the four master cylinder mounting bolts. Unbolt both mounting brackets from frame and slide Rotochamber away from master cylinder.
CAUTION Be sure master cylinder is supported by some external means before separating it from Rotochamber , to prevent pos sible damage to hydraulic line. After old Rotochamber is separated from master cylinder, transfer mounting brackets and warning switch to new Rotochamber. If old switch is not useable, in stall a new one. Assemble Rotochamber to master cylinder (either on or off chassis) and secure to frame. Connect air line and charge air system. If hydraulic line was discon nected, reconnect it and bleed hydraulic system.
Q95a - Back of Sheet 1