Control force readings may be terminated when vehicle speed falls to 5 mph. Each passenger car and each multipurpose passenger vehicle, truck, and bus with a GVWR of 10,000 pounds or less must be capable of meeting the requirements of S5.1.1 through S5.1.6 under the conditions prescribed in S6, when tested according to the procedures and in the sequence set forth in S7. 3. 7 . Allow a braking distance interval of 1 mi. The pedal should not move. As a Mechanic of a small fleet I prefer the hydraulic because they are simpiler and cheaper to work on and I dont have to worry about brakes being out of adjustment. The pedal should not move. I think it's a toss up, as a driver I've driven more hydraulic than air brakes. The indicator lamp shall be deactivated at the end of the check of lamp function unless there is a malfunction or a message about a malfunction that existed when the key switch was last turned to the off position. Fuel Tank/Cap - tank secure, cap tight, no leaks . There's a reason big rigs have air brakes! Listen for any possible leaks. I'm a new noob here, but from what I've read. user convenience only and is not intended to alter agency intent Other considerations Weight is an important consideration when brakes are being discussed. Repeat the test, impacting the vehicle from the rear. 0000002509 00000 n
The parking brake test surface is clean, dry, smooth, Portland cement concrete. Backup system means a portion of a service brake system, such as a pump, that automatically supplies energy, in the event of a primary brake power source failure. For vehicles with parking brake systems not utilizing the service brake friction elements, burnish the friction elements of such systems prior to parking brake tests according to the manufacturer's published recommendations as furnished to the purchaser.
Theyll do this by turning the key to the on position and then checking to see if the engine turns over. School Bus 101 9.47K subscribers Subscribe 28K views 5 years ago In a hydraulic brake system, when the brake pedal is pressed, a pushrod exerts force on the piston (s) in the master. The Federal Motor Carrier Safety Administration (FMCSA) has developed and issued standards for State testing and licensing of CDL holders. (b) For vehicles manufactured on and after September 1, 1999 with GVWRs greater than 10,000 lbs, each message about the existence of a malfunction, as described in S5.3.1(c), shall be stored in the antilock brake system after the ignition switch is turned to the off position and the indicator lamp shall be automatically reactivated when the ignition switch is again turned to the on position. Turn the bus off. i think the disc brakes stop beter than air also. Turn the key to the off position. (b) Each vehicle with a GVWR greater than 10,000 pounds shall be capable of making 10 fade snubs (20 fade snubs on the second test) from 40 mph to 20 mph at 10 fpsps for each snub. (3) Before or upon application of 25 pounds of control force upon a service brake with a brake power assist unit. Check the hydro-boost for leaks. The in-page Table of Contents is available only when multiple sections are being viewed. The parking brake test surface is clean, dry, smooth, Portland cement concrete. Brake power units shall also be charged to maximum accumulator pressure prior to start of test. S7.11.3.1 Vehicles with GVWR of 10,000 lb or less. Wheels on other axles of the vehicle may be indirectly controlled by the antilock brake system. On each vehicle with a GVWR greater than 10,000 pounds but not greater than 19,500 pounds and motor homes with a GVWR greater than 10,000 pounds but not greater than 22,500 pounds manufactured before March 1, 2001, the antilock brake system may also directly control the wheels of the rear drive axle by means of a single sensor in the driveline. S5.1.2.4 For an EV manufactured with a service brake system that incorporates RBS, the vehicle shall be capable of stopping from 60 mph within the corresponding distance specified in Column IV of Table II with any single failure in the RBS, and with all other systems intact. Accelerate immediately to the initial test speed after each stop. Since most large trucks have air brakes then why not large school buses. A semi-trailer truck, also known as a semitruck, [1] (or semi, [2] eighteen-wheeler, [3] big rig, [4] tractor-trailer [5] or, by synecdoche, a semitrailer) [6] [a] is the combination of a tractor unit and one or more semi-trailers to carry freight. In extreme cases, a complete loss of braking power can occur. Air brakes are more powerful, and have the spring-applied failsafe that will stop the bus in most brake failure situations. Except where an adjustment is specified, after each brake application accelerate to 40 mph and maintain that speed until making the next brake application at a point 1 mile from the initial point of the previous brake application. 1 Depleted. (including driver and instrumentation); (b) For vehicles with a GVWR greater than 10,000 lbs., unloaded vehicle weight plus 500 lbs. S6.3 Tire inflation pressure. S-cam brakes, on the other hand, require an external slack adjuster. Your email address will not be published. (d) At vehicle speeds of 20 mph or less, any wheel may lock up for any duration. (B) If a separate indicator lamp is provided for low brake fluid, the words Brake Fluid shall be used for S5.3.1(b), except for vehicles using hydraulic system mineral oil. Each vehicle must be equipped with a service brake system acting on all wheels. Hydraulic brake system means a system that uses hydraulic fluid as a medium for transmitting force from a service brake control to the service brake, and that may incorporate a brake power assist unit, or a brake power unit. (2) Before or upon application of 50 pounds of control force upon a fully manual service brake. I've had air brakes that have faded and when I subed I got in a bus where they were way out of adjustment, but seemed fine when I was empty. Burnish stops are conducted on any surface. This will tell you how much force the system is capable of generating. It is in keeping with a concern for safety that the four-wheel disc brake system has become the brake of choice for the school bus industry. Stability and control during braking (braking-in-a-curve test), 8. To avoid engine stall during tests required to be run in gear a manual transmission may be shifted to neutral (or the clutch disengaged) when the vehicle speed decreases to 20 mph. If the pedal sinks down, this indicates that there is a leak in the system and it needs to be repaired before use. They feel sooooo much more confident in a heavy vehicle. Its a 34' Freightliner Thomas. S7.7.1.4 Following the application of the parking brake in accordance with S7.7.1.3, release all force on the service brake control and commence the measurement of time if the vehicle remains stationary. If there are no leaks in the system, you should see the needle on the pressure gauge rise steadily during this time. Spring pressure c. Air pressure d. Any of the above 2. Drive 1 mi at 30 mph after the last fade stop, and immediately follow the recovery procedure specified in S7.11.3.1. S6 Test conditions. For centergrooved shoes or pads, thermocouples are installed within one-eighth of an inch to one-quarter inch of the groove and as close to the center as possible. Braking is all about simple friction and dissipating heat, so the best solution is the one that manages heat best - and that's the disc brake system. FY TP-116-04. Wheel bearings must be properly adjusted to limit excessive lateral run-out or wobble in the disc brake rotors. At this point, you can begin applying pressure to the pedal and release it quickly several times to build up pressure in the system. Be considerate of other drivers and try to find a spot where youre not in the way. Apply the brake pedal with approximately 100 lbs. The caliper attaches to and slides within an anchor plate or bracket. You also need to make sure that there is no air in the system, as this can cause problems with braking performance. S6.15 Selection of compliance options. Drivers Brake pads are mounted on each side of the rotor and grip the rotor when hydraulic pressure is applied by the hydraulic piston located in the caliper. Restore the service brake system to normal at completion of this test. endstream
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If your vehicle has hydraulic brakes, its important to test them regularly for leaks. Turn the key to the on position, do not start the truck. Choosing an item from They're standard on our buses in everything except type "A" and we don't run a lot of them. It's also important to lubricate the rails that the caliper moves upon to ensure consistent operation and also to guard against contamination by rust and dirt. Restore the service brake system to normal at completion of this test. title 49 of the Code of Federal Regulations, 7. Test for stopping (25) 2. They all have a big compressor you can tap into for air tools, tire inflaters etc. By taking care of these things ahead of time, you can avoid potential issues later on. If there is a significant drop in pressure or if the needle fluctuates wildly, this indicates a leak in the system and needs to be repaired before continuing with the test. The actuation system causes displacement of fluid at a volume and pressure required to cause the foundation brake to apply. If air bubbles get into the hydraulic fluid, they can compress when the brake pedal is applied. A school bus shall not a. 2389 turbine oil, the motor weighs approximately 225 pounds. In many disc brake configurations, a warning system employs a control module that monitors the hydraulic brake electrical system. c. Test the bus a second time to make sure the bus stops properly. Fill to this level. OEM-standard lubricants are the best choice for this application because they're designed to meet tough duty standards, like school buses. Comments that include personal
49 U.S.C. 3. Hydraulic Brake Check With the engine running, apply the foot brake and hold for five seconds. Better stopping power. Don't automatically be fooled by big-rigs use of air brakes. Where manufacturer options are specified, the manufacturer shall select the option by the time it certifies the vehicle and may not thereafter select a different option for the vehicle. Bus should not move. Is it because school bus operators are too cheap to train their drivers? Conduct 10 stopping tests from a speed of 100 kph or the maximum vehicle speed, whichever is less. Park your car on level ground and set the parking brake. Subscribe to: Changes in Title 49 :: Subtitle B :: Chapter V :: Part 571 :: Subpart B :: Section 571.105. S7.4.1 Vehicles with GVWR of 10,000 lb or less. I have a bus with air brakes and just bought one with hydraulics so i'll soon know the pros and cons of both! Make four stops, each from 60 mph by a continuous application of the service brake control. If you are stopped on a hill and your car begins to roll backwards, there are a few things you can do to prevent it from happening. For vehicles equipped with more than one brakepower assist or brakepower unit, conduct tests of each in turn. This self-paced FAST course gives you: EASY step-by-step instructions how to conduct a pre-trip inspection; precise path of travel around the vehicle;. S7.9.6 For an EV with RBS that is part of the service brake system, the tests specified in S7.9.1 through S7.9.3 are conducted with the RBS disconnected and all other systems intact. Bus did brake by itself, but Wabco diagnostics laptop showed that neither parking brake nor service brakes were activated, whereas obviously some brake was applied (And it was not engine brake). Scope. S6.6 Vehicle openings. After burnishing, adjust the brakes in accordance with the manufacturer's published recommendations. Control force readings may be terminated when vehicle speed falls to 5 mph. Make three stops from 30 mph at 10 fpsps for each stop. The vehicle used for this test need not be the same vehicle that has been used for the braking tests. 0000000858 00000 n
(c) Unlimited wheel lockup is allowed during spike stops (but not spike check stops), partial failure stops, and inoperative brake power or power assist unit stops. Test procedure and sequence. (b) In the case of a vehicle with a GVWR greater than 4,536 kilograms (10,000 pounds), with a force applied to the control not to exceed 150 pounds for a foot-operated system and 125 pounds for a hand-operated system. 571.105 Standard No. xref
Active Member. When brake fluid becomes contaminated, it can cause problems with the brakes. (a) For vehicles with electrically-actuated service brakes, the tests in S7.10.1 or S7.10.2 are conducted with any single electrical failure in the electric brake system instead of the brake power or brake power assist systems, and all other systems intact. This questions appears in the following tests: Colorado Double District Of Columbia Class A Knowledge Test Illinois Passenger to 200 F. (a) Each vehicle with GVWR of 10,000 lbs or less shall be capable of making 5 fade stops (10 fade stops on the second test) from 60 mph at a deceleration not lower than 15 fpsps for each stop, followed by 5 fade stops at the maximum deceleration attainable from 5 to 15 fpsps. 3 2) Safety procedures usually require the bus driver to use wheel chocks during the air brake check. S7.9.3 Repeat S7.9.1 and S7.9.2 with vehicle at GVWR. %PDF-1.4
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Restore the system to normal at completion of this test. Test as in S7.10.2(a), except make 10 stops instead of 6 and, at the completion of the 10 stops, deplete the failed element of the brake power unit of any residual brake power reserve capability before making the final stop. Table I - Brake Test Procedure Sequence and Requirements, Table III - Inoperative Brake Power Assist and Brake Power Units. S7.10 Service brake system - inoperative brake power unit or brake power assist unit test. S7.11 Service brake system - first fade and recovery test. The second thermocouple shall be installed at .080 inch depth within 1 inch circumferentially of the thermocouple installed at .040 inch depth. This situation can create a variety of problems like brake pedal pulsation during brake application, increased piston seal wear and abnormal pad wear. "Published Edition". 8 c. 10 d. 15 Stopping distance means the distance traveled by a vehicle from the point of application of force to the brake control to the point at which the vehicle reaches a full stop. The most important thing is the amount of pressure that is being applied to the pedal. 1. S7.16 Service brake system - water recovery test. Press both air brake valves in, red valve first then yellow in second. I couldnt tell exactly on my rears but thought it almost looked drum.. but I guess in 2000 it was not dont that way anymore so I probably have disc on that hydro bus. 3) Here are the types of tests that must be conducted on a typical air brake system: a) The Governor Cut in/Cut out test is to make sure that the governor is applying or cutting off air pressure to the air reservoir tanks as needed. This web site is designed for the current versions of 0000000859 00000 n
Turn the key to the on position without starting the bus. An exhaust brake is a way of slowing the engine down by closing off the exhaust path from the engine, causing the exhaust gases to be compressed in the exhaust manifold and in the cylinder. (c) The service brakes shall be capable of stopping each vehicle with a GVWR greater than 10,000 pounds in two effectiveness tests within the distances and from the speeds specified in S5.1.1.2 and S5.1.1.3. contact the publishing agency. There should be no more than 3 psi of air loss. S6.9.2 (a) For vehicles with a GVWR greater than 10,000 pounds, road tests (excluding stability and control during braking tests) are conducted on a 12-foot-wide, level roadway, having a peak friction coefficient of 1.02 when measured using an ASTM F2493 standard reference test tire, in accordance with ASTM E1337-19 (incorporated by reference, see 571.5), at a speed of 40 mph, without water delivery. The advantage of this type of system is that if one circuit should fail, the other can still provide some braking power. S7.11.1.2 Vehicles with GVWR greater than 10,000 pounds. Attain the required deceleration within 1 second and, as a minimum, maintain it for the remainder of the stopping time. Engineer: Frederick Smith. 0000000556 00000 n
This will give you the best traction possible and help keep your car from rolling. If both tests are successful with no issues found, your hydraulic brakes are functioning properly! Disc brakes are long lasting and provide safe, even stopping. Its like asking people what is better Chevy or Ford. Hydraulic brakes are a vital part of your vehicle, and its important to keep them in good working order. If its low, that could indicate a leak as well. The parking or emergency brake on a heavy vehicle can only be held into position by something that cannot leak away. If you would like to comment on the current content, please use the 'Content Feedback' button below for instructions on contacting the issuing agency. S6.2.1 The state of charge of the propulsion batteries is determined in accordance with SAE Recommended Practice J227a (1976) (incorporated by reference, see 571.5). Bendix Hydro-Max Brake System Inspecting 1. A separate drafting site An example would be? Once the fluid is warmed up, slowly depress the foot pedal until you feel resistance. The force required for actuation of a hand-operated brake system shall be measured at the center of the hand grip area or at a distance of 112 inches from the end of the actuation lever, as illustrated in Figure II. (b) For EVs with RBS that is part of the service brake system, the tests in S7.10.1 or S7.10.2 are conducted with the RBS discontinued and all other systems intact. Immediately upon reaching that speed make five stops, each from 30 mph at 10 fpsps for each stop. Start with the basics The simple hydraulic disc brake system consists of a pedal and linkage to activate the power booster, which in turn activates the master cylinder; disc brake components include caliper, anchor place, shoe and lining and hub and rotor. The CDL General Knowledge practice test covers topics such as the rules of having a CDL and driving a commercial vehicle safety. Tandem axle means a group of two or more axles placed in close arrangement one behind the other with the center lines of adjacent axles not more than 72 inches apart. During each burnish procedure, the propulsion batteries may be charged by an external means or replaced by batteries that are charged to the state of charge recommended by the manufacturer or a state of charge of not less than 95 percent. If its low, there may be a leak somewhere in the system. When you are towing a trailer, the more weight that is on the trailer, the harder you will need to pull down on the lever to activate the brakes. This blog post will provide detailed information on how to properly conduct a hydraulic brake test on a school bus. S7.9.2 Repeat S7.9.1 for each of the other subsystems. 39. 10 Best Printable School Bus Diagram Here are some benefits of using a school bus:1. 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