Canada Motor Vehicle safety standard - 121 - Timing Test

ATTACHMENT A: VEHICLE DESCRIPTION

Certification records must accurately describe the vehicle to which they apply so that a relationship can be demonstrated between the vehicle and the test report. To assist a manufacturer in describing the vehicle, the following information should be specified:

VIN: _______________________________________________________________

BODY STYLE: _______________________________________________________

TYPE/MODEL: ______________________________________________________

YEAR: _____________________________________________________________

OVERALL LENGTH: __________________________________________________

GVWR: ____________________________________________________________

NUMBER OF AXLES: ________________________________________________

GAWR: ___________________________________________________________

COMPONENTS (MAKE and MODEL NUMBER): ___________________________

AXLES: __________________________________________________________

SLACK ADJUSTERS: _______________________________________________

BRAKE CHAMBERS: ________________________________________________

FRICTION MATERIAL: _______________________________________________

AIR SYSTEM COMPONENTS:_________________________________________

WHEEL ENDS: ____________________________________________________

WHEEL SYSTEM: __________________________________________________

TIRES: ___________________________________________________________

SUSPENSION: ____________________________________________________

AIR LINE LENGTHS AND NUMBER/TYPE OF FITTINGS (include and reference a plumbing schematic):

ATTACHMENT B: SUMMARY OF LEGISLATIVE REQUIREMENTS FOR TIMING OF TRAILERS AND CONVERTER DOLLIES:

(Sections not applicable to trailers and converter dollies are omitted. Conversion to imperial units in brackets added.)

S5.3.3 Brake actuation time. Each service brake system shall meet the requirements of S5.3.3.1(a) and (b)

S5.3.3.1

(a) With an initial service reservoir system air pressure of 689 kPa (100 psi), the air pressure in each brake chamber shall, when measured from the first movement of the service brake control, reach 413.4 kPa (60 psi) in not more than -----------0.50 second in the case of trailers, other than trailer converter dollies, designed to tow another vehicle equipped with air brakes, 0.55 second in the case of trailer converter dollies, and 0.60 second in the case of trailers other than trailers designed to tow another vehicle equipped with air brakes. A vehicle designed to tow another vehicle equipped with air brakes shall meet the above actuation time requirement with a 0.819-L (50-cu. in.) test reservoir connected to the control line output coupling. A trailer, including a trailer converter dolly, shall meet the above actuation time requirement with its control line input coupling connected to the test rig shown in Figure 1.

(b) For a vehicle that is designed to tow another vehicle equipped with air brakes, the pressure in the 0.819-L (50-cu. in.) test reservoir referred to in S5.3.3.1(a) shall, when measured from the first movement of the service brake control, reach 413.4 kPa(60 psi) not later than the time the fastest brake chamber on the vehicle reaches 413.4 kPa (60 psi) or, at the option of the manufacturer, in not more than ------------ 0.55 second in the case of trailer converter dollies, and 0.50 second in the case of trailers other than trailer converter dollies.

S5.3.4 Brake release time. Each service brake system shall meet the requirements of S5.3.4.1(a) and             (b).

S5.3.4.1

(a) With an initial service brake chamber air pressure of 654.6 kPa (95 psi), the air pressure in each brake chamber shall, when measured from the first movement of the service brake control, fall to 34.5 kPa(5 psi) in not more than ---- 1.00 second in the case of trailers, other than trailer converter dollies, designed to tow another vehicle equipped with air brakes, 1.10 seconds in the case of trailer converter dollies, and 1.20 seconds in the case of trailers other than trailers designed to tow another vehicle equipped with air brakes. A vehicle designated to tow another vehicle equipped with air brakes shall meet the above release time requirement with a 0.819-L (50-cu. in.) test reservoir connected to the control line output coupling. A trailer, including a trailer converter dolly, shall meet the above release time requirement with its control line input coupling connected to the test rig shown in
Figure 1.

(b) For vehicles designed to tow another vehicle equipped with air brakes, the pressure in the 0.819-L (50-cu. in.) test reservoir referred to in S5.3.4.1(a)

S5.3.5 Control signal pressure differential — Converter dollies and trailers designed to tow another vehicle equipped with air brakes

(a) For a trailer designed to tow another vehicle equipped with air brakes, the pressure differential between the control line input coupling and a 0.819-L (50-cu. in.) test reservoir attached to the control line output coupling shall not exceed the values specified in S5.3.5(a)(1), (2), and (3) under the conditions specified in S5.3.5(b)(1) through (4):

(1) 6.9 kPa (1 psi) at all input pressures equal to or greater than 34.5 kPa (5 psi), but not greater than 137.8 kPa (20 psi); and

(2) 13.8 kPa (2 psi) at all input pressures equal to or greater than 137.8 kPa (20 psi), but not greater than 275.9 kPa (40 psi); and

(3) not more than a 5 percent differential at any input pressure equal to or greater than 275.9 kPa (40 psi).

(b) The requirements in S5.3.5(a) shall be met

(1) When the pressure at the input coupling is steady, increasing, or decreasing;

(2) When air is applied to or released from the control line input coupling using the trailer test rig shown in Figure 1;

(3) With a fixed orifice consisting of a 0.46-mm (0.0180-in.) diameter hole (no. 77 drill bit) in a 0.81-mm (0.032-in.) thick disc installed in the control line between the trailer test rig coupling and the vehicle's control line input coupling; and

(4) When operating the trailer test rig in the same manner and under the same conditions as it is operated during testing to measure brake actuation and release times, as specified in S5.3.3 and S5.3.4, except for the installation of the orifice in the control line to restrict the airflow rate.

FIGURE 1: Test rig

Mini-Tractor Explanation:

The mini-tractor is used to time the application and release time of a towed vehicle (trailer or converter dolly). It is a test rig designed to standardize the performance of a tow vehicle (tractor). This standardization is required for testing purposes so that the tests are repeatable.

S6.1.13 Trailer test rig

The trailer test rig shown in Figure 1 is calibrated in accordance with the calibration curves shown in Figure 3. For the requirements of S5.3.3.1 and S5.3.4.1, the pressure in the trailer test rig reservoir is initially set at 689 kPa (100 psi) for actuation tests and 654.6 kPa (95 psi) for release tests.

ATTACHMENT C: TEST PROCEDURE

Include a step by step description of how the test was performed. The test procedure should include the following steps. Additional steps should be documented as necessary.

Step 1- Calibrate mini-tractor to TSD S6.1.13 (Consult mini-tractor manufacturer's operating instructions for operating details.)

Make and model of mini-tractor: _______________________________________

Serial number: ____________________________________________________

Connect shop air to mini-tractor:

__ CHECK

(Note: There must be a constant 689.5 kPa (100 psi) mini-tractor reservoir pressure available to run tests).

Include print out of calibration of mini-tractor)

Step 2- install pressure transducers on air brake chambers (indicate location on Figure 2 below).

Step 3- attach 819.35 cm³ (50 in³) test reservoir to rear of trailer if designed to tow another vehicle: __

Use the mini-tractor to measure the time it takes for the pressure in the air brake chamber to go from atmospheric to 413.7 kPa (60 psi) from when the service brake control is first depressed.

Record results on chart below (include print out from mini-tractor).

Step 5- perform brake release test;

Use the mini-tractor to measure the time it takes for the pressure in the air brake chamber to go from 655 kPa (95 psi) to 34.47 kPa (5 psi) from when the service brake control is first released:

Record results on chart below (include print out from mini-tractor).

Step 6- repeat steps 1 to 5 for other brake chambers as necessary.

Transducer #
(from fig. 2)

Application Time

Release Time

_______sec.

_______sec.

_______sec.

_______sec.

_______sec.

_______sec.

_______sec.

_______sec.

819.35 cm³ (50 in³) test reservoir transducer
(if applicable)

_______sec.

_______sec.