Centric Link Brake Dynamometers

 by Steve Ruiz of StopTech

Overview:

Centric and Stoptech currently operate three Link Brake Dynamometers, each built with state-of-the-art technology for performing input and output tests on hydraulically actuated brake assemblies. Two dynamometers are fully-contained NVH enclosures, while the 3rd dynamometer is a smaller setup focusing on simulated inertia tests. The dynamometers’ designs along with preset test parameters provide optimal correlation to actual field operating conditions. All primary operating functions are performed at the dynamometer computer station, including selection of test parameters, control modes, display of pertinent data, monitoring of all test functions, and execution of desired test protocols.

The Model 3900 NVH brake dynamometer is able to monitor noise and vibration data during testing of corner and axle type brake fixtures. Simulating a wide range of brake noise issues is made possible by the dynamometer’s technology which allows for optimal correlation to actual operating conditions. The brake test cell is completely separate from the dynamometer drive and support systems to isolate any outside noise and vibration, making the dynamometer ideally suited for brake noise testing. Low frequency noise testing is made possible by the double-wall enclosure which provides a high transmission loss, and the walk-in style chamber can accommodate full vehicle corner sections and axle fixtures as well as conventional corner groups.

Stoptech/Centric Link 3900 NVH Dynamometers:

 


Link 3900 NVH Dynamometer
Serial Number 261786
Dyno #1



Link 3900 NVH Dynamometer
Serial Number 281965
Dyno #2


Link 3900 NVH Dynamometers:

Two of the dynamometers used by Centric and Stoptech are Link 3900 NVH Dynamometers.

  • Dyno #1 – Link 3900 NVH Dynamometer – Serial Number 261786
  • Dyno #2 – Link 3900 NVH Dynamometer – Serial Number 281965

Dynos #1 and #2 are very similar in that they are identical NVH enclosures, however Dyno #2 incorporates several additional features over Dyno #1:

  • Dyno #2 has a low-speed Static Torque system powered by a 6200 Nm motor capable of maintaining consistent low shaft speeds between 0-17 rpm.
  • Dyno #2 has parking brake testing capabilities, and can be coupled with the Static Torque system to test parking brake hill-hold scenarios. 
  • Dyno #2 has additional inertia capabilities allowing larger corner groups such as a Ford F250 or F350, LC200 armored platforms, Sprinter Vans, and even drum brakes and full rear axles to be tested. Refer to the comparison table on the following page for itemized technical specifications for each dynamometer.

 

Link 3000 Inertia Dynamometer:



Link 3000 Inertia Dynamometer
Serial Number 310713
Dyno #3

 

Brake Dynamometer Technical Specifications:

 

Parameter  Dyno #1 Range Dyno #2 Range  Dyno #3 Range 
 Pressure Control 0 – 206 bar  0 – 206 bar  0 – 206 bar
 Rotating Torque 0 – 5650 N-m 0 – 11297 N-m  0 – 5600 N-m 
 Cooling Air Speed 0 – 150 mph 0 – 150 mph  0 – 45 mph 
 Fluid Displacement 0 – 32 cm3 0 – 32 cm3   0 – 32 cm3
 Rotational Speed 2800 rpm 2800 rpm  2000 rpm 
 Stationary Temperature (qty. 4)  1000°C 1000°C  1000°C 
Rotating Temperature (qty. 4)  1000°C 1000°C  1000°C 
Cooling Air Temperature   100°C  100°C  100°C
Cooling Air Humidity  100% RH   100% RH 100% RH 
Dynamometer Inertia  10.033 – 180.23 kg•m2  10.033 – 271.16 kg•m2   10.033 – 127.96 kg•m2
Parking Brake Force  --  3350 N   --
Parking Brake Stroke  --   100 mm  --

Note: The NVH configuration of the Dynamometer provides six (6) channels for noise and vibration measurement. The NVH module is tied in to the ProLink software package to allow noise and vibration events to be logged simultaneously with stop data.

 

Inertia Simulation Feature Explained:

 

  • In order to accommodate a range of inertias representing specific vehicle corner groups, the Link 3900 and 3000 Dynamometers are equipped with a feature called ISIM, or Inertia Simulation. This feature utilizes two powerful AC motors that work to take up a given portion of vehicle inertia by force addition or subtraction of the inertia load. This system accounts for the fact that inertia force is a result of both angular velocity and moment of inertia of the plates directly installed on the dynamometer shaft. Past inertia strategies incorporated many plates in ranges of thicknesses representing small increments for the best approximation. Now, only 3 plates of equal thickness and weight are needed, and the AC motors are able to correct to the calculated required test inertia, provided this inertia is within machine specifications.

  • For example:

    • Calculated Required Inertia for Ford Taurus D601 platform – 84.71 kg•m2

    • Actual Installed Dyno Inertia for Ford Taurus D601 platform – 81.23 kg•m2 (1 plate)

    • ISIM requirement – 3.48 kg•m2 (to be dynamically added to installed inertia)

  • Testing of corner groups in one of the specific dynos is determined based on the final inertia required for the specific platform.

    • Additional Dyno #2 inertia allows for testing of larger, heavy-duty platforms such as a Ford F250 or F350, LC200, or other armored vehicle platforms.




Calibration Schedule:

All three brake dynamometers are calibrated with Link on a yearly basis, and these calibrations cover every sensor on the dynos. The last calibration was performed in July 2015, and these reports can be made available upon request. Additional dyno calibrations for the 2016 year are scheduled to occur in July pending Link technician availability.

 

Additional Dynamometer Photos:



HVAC ducts that supply fresh ambient air to the dyno as well as
exhaust fumes and particulates from the dyno cell. Exhaust ducts
are passed through 12 microparticle filters prior to exhausting to
atmosphere to ensure air being exhausted is clean. Adjustable
dampers can allow for air to be recirculated as well.


A typical corner group assembly installed in the dyno. This
particular corner group uses an OE upright to locate the caliper and
rotor relative to one another, and provides a closer simulation of
braking performance when compared with the universal fixtures.
A close-up view of the test drum and normal force applicator.


The versatile test sled is able to accommodate a full vehicle axle in
the test cell. Here a rear axle is shown prior to performing testing
on the parking brake system.


Parking Brake test fixture used to activate parking brake. Cable is
attached to load cell, and pneumatic linear actuator applies
controlled parking brake stroke. Linear potentiometers measure the
stroke and the load cell measures the cable force.


A dual-ended test fixture that allows testing of two corner groups
simultaneously. Universal 2-piece fixtures can be made to
accommodate various caliper designs and manufacturers, as well
as rotor sizes. Split ducts provide cooling air to each corner separately.


A close-up view of the universal 2-piece caliper fixture. These can be
designed for specific applications, in this case a Stoptech ST60
caliper and 2-piece AeroRotor.


The dyno consists of one fixed inertia plate, and 3 additional
inertia plates that can be added if more inertia is required. The
powerful AC infinitely variable speed motors are capable of
adding and/or subtracting force on the inertia load to account for the
differences between the plates, making it possible to test any
specific inertia between the minimum and maximum allowable inertias.


Static Torque drive system installed on Dyno #2. System is used for
low-speed testing typically applied to Parking Brake systems. Motor is a
6200 Nm motor capable of maintaining constant dyno shaft speeds of 0-17 rpm.




Fixture Types Used:

  • Two distinct fixture types are employed in Centric / Stoptech friction couple testing:
    • 2-piece Tailstock Adapter
    • Vehicle-specific Upright


2-Piece Tailstock Adapter:

This fixture type utilizes a universal tailstock adapter in combination with a specific rotor hub and caliper bracket designed for a specific application. Both components can be designed to suit specific vehicle applications, and Stoptech oversees the design and production of these fixtures. Example photos of representative rotor hubs and caliper brackets can be seen below.


Rotor Hub and Caliper Bracket for use with a Ford Taurus D601 application.


Rotor Hub and Caliper Bracket for use with a Ford F250 D756 application.

 

Vehicle-Specific Upright:

This fixture type utilizes a complete vehicle upright combined with structural members to provide a rigid fixture  most closely resembling an on-vehicle application. Vehicle uprights provide the most accurate representation  of NVH characteristics during testing, and also allow parameters like residual drag torque to be factored in  due to upright bearing design or geometry. Stoptech possesses the ability to design and oversee the  manufacture of vehicle-specific upright fixtures for an array of applications, including street and race. Example photos of representative vehicle-specific upright fixtures can be seen below.


Vehicle-Specific Upright for Stoptech STR60GT Caliper development testing.


Vehicle-Specific Upright for Corvette Z06 D1247 pad shape applications.

 

Common Test Scripts:

The charts below illustrate some of the common test scripts utilized during testing at the Stoptech facility. These tests make up the majority of testing performed by Stoptech and Centric, however additional scripts can be written to tailor testing to specific applications or purposes.


Brake Pad/Rotor Testing

 

Test Description  Test Purpose Estimated Dyno Time  Data Output Test Requirements
 SAE J2521 -
Noise Matrix
 A noise matrix to identify high 
frequency squeal-type noise 
occurrences for passenger car and
 light truck vehicles. Squeal is defined
as a noise event greater than 70dB occurring between 2000 and 16,000 Hz for disc brakes.
30 hrs   Number of
Noise
Events; Avg
Pad Wear;
Max Rotor
Wear
--The SAE J2521 must utilize an NVH dyno to isolate testing NVH. The Drive
Cycle and SAE J2522 and 2707A tests
can be run on a standard friction dyno.





--Each test requires definition of a
caliper, rotor, and brake pad. Part
numbers should be submitted to the
testing department at the time of the
test request submittal.





--Vehicle parameters (form to fill out
available upon request) for the desired
friction couple need to be submitted.





--All test sample components are
measured for overall thickness before,
during, and after tests per the specific
test requirements. This data is used to
calculate wear rates on both the friction
and rotor samples. 
 4000 Stop
Drive Cycle
 A simulated city-traffic test
consisting of a Pre-Wear ramp
section, and ten 100 stop
sections. This sequence is
repeated 4 times. The 100
stop section is a set of random
stops from different speeds
and set points, taken directly
from a vehicle.
80 hrs  Avg Mu; Avg
Pad Wear;
Max Rotor
Wear
 SAE J2522 w/MOT
(AK Master)
An effectiveness evaluation to
assess specific friction
material characteristics when
subjected to a series of
different pressures, speeds,
and temperatures. The MOT
test is performed at the
conclusion of the SAE J2522,
and serves to define the
Maximum Operating
Temperature of the friction
material. 
22 hrs   Avg Mu Fade
1; Avg Mu
Fade 2; Avg
Mu Full Test;
Avg Pad
Wear; Max
Rotor Wear
SAE J2707A  A wear test at various
temperatures. Pads are
subjected to 100°C-500°C
stop sections to qualify the
pad material's behavior at
elevated temperatures. 
 150 hrs Avg Pad
Wear Full
Test; Avg
Pad Wear by
Section; Max
Rotor Wear 

Note: The above 4 tests represent the Centric / StopTech Friction Testing Suite for brake pads and rotors. Friction  materials tested are typically subjected to all 4 tests (new friction couples used in each test). D601, D562, D756, D931  are the most common fixtures used by StopTech. Fixtures for pad shapes or corner groups not satisfying these pad  shapes will need to be investigated by the Testing and Engineering teams, along with the testing requirements.

 

Brake Shoe/Drum Testing

 

Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
SAE J2521 -
Noise Matrix
A noise matrix to identify high frequency
squeal-type noise occurrences for passenger car and light truck vehicles. Squeal is defined
as occurring between 500 and
17,000 Hz for drum brakes.
30 hrs Number of
Noise
Events; Avg
Shoe Wear;
Max Drum
Wear
--The SAE J2521 must utilize an
NVH dyno to isolate testing NVH.
The Drive Cycle and SAE J2522
tests can be run on a standard
friction dyno.





--Each test requires definition of a
drum, and brake shoe. Part numbers 
should be submitted to the testing 
department at the time of the test 
request submittal.





--All test sample components are
measured for overall thickness before, 
during, and after tests per the specific 
test requirements. This data is used to 
calculate wear rates on both the friction and drum samples.
SAE J2707 A wear test performed at
various Initial Brake
Temperatures. 1000 stops
are performed at 100C, 200C,
250C, and finally 500 stops
are performed at 300C, 100C
and 200C (4500 total stops).
144 hrs Avg Beff; Avg
Shoe Wear;
Max Drum
Wear
ISO 26867 A friction comparison study
that describes the influence of
pressure, temperature, and
linear speed on the coefficient
of friction of a specific friction
couple. Initial brake
temperature is used as the
control in the Fade sections to
ensure repeatable results
across various dynamometer
cooling systems.
20 hrs Avg Beff
Fade 1; Avg
Beff Fade 2;
Avg Beff Full
Test; Avg
Shoe Wear;
Max Drum
Wear

Note: The above 3 tests represent the Centric / StopTech Friction Testing Suite for brake shoes and drums. Friction materials tested are typically subjected to all three tests (new friction couples used in each test). StopTech currently only has the capability for the S514 shoe to be tested.

 

Vehicle System Validation Testing 

 

Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
FMVSS
105/135
Brake corner assemblies are
tested for overall brake output,
friction material effectiveness,
and corner performance.
This procedure is applicable to all passenger cars and light
trucks up to 3500kg of GVWR.
28 hrs Varies by
test.
Varies by
Test
Simulations of
TUV Tests 
Simulations can be derived
from various TUV test
protocols/standards and
implemented in the
dynamometer. Vehicle corner
assemblies are typically tested
to ensure better data
correlation with real-world
applications. 
Varies by
Test 
Varies by
Test 
 Varies by
Test

 

 

Police Vehicle Friction Screening 



Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
FMVSS
105/135
Brake corner assemblies are
tested for overall brake output,
friction material effectiveness,
and corner performance. 
This procedure is applicable to all passenger cars and light
trucks up to 3500kg of GVWR.
28 hrs Varies by
test.
Varies by
Test
Simulations of
TUV Tests 
Simulations can be derived
from various TUV test
protocols/standards and
implemented in the
dynamometer. Vehicle corner
assemblies are typically tested
to ensure better data
correlation with real-world
applications. 
Varies by
Test 
Varies by
Test 
 Varies by
Test

 

 

Vehicle System Validation Testing 

Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
FMVSS
105/135
Brake corner assemblies are
tested for overall brake output,
friction material effectiveness,
and corner performance. 
This procedure is applicable to all passenger cars and light
trucks up to 3500kg of GVWR.
28 hrs Varies by
test.
Varies by
Test
Simulations of
TUV Tests 
Simulations can be derived
from various TUV test
protocols/standards and
implemented in the
dynamometer. Vehicle corner
assemblies are typically tested
to ensure better data
correlation with real-world
applications. 
Varies by
Test 
Varies by
Test 
 Varies by
Test

 

Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
SAE J2521 -
Noise Matrix
A noise matrix to identify high
frequency squeal-type noise
occurrences for passenger car and
light truck vehicles. Squeal is defined as a noise event greater than 70dB 
occurring between 1000 and 18,000 Hz
for disc brakes.
30 hrs Number of
Noise
Events; Avg
Pad Wear;
Max Rotor
Wear
--The SAE J2521 must utilize an NVH
dyno to isolate testing NVH. The Drive
Cycle and SAE J2522 tests can be run
on a standard friction dyno.





--Each test requires definition of a rotor,
and brake pad. Part numbers should be
submitted to the testing department at
the time of the test request submittal.





--All test sample components are
measured for overall thickness before,
during, and after tests per the specific
test requirements. This data is used to
calculate wear rates on both the friction
and rotor samples.
ISO 26867 A friction comparison study
that describes the influence of
pressure, temperature, and
linear speed on the coefficient
of friction of a specific friction
couple. Initial brake
temperature is used as the
control in the Fade sections to
ensure repeatable results
across various dynamometer
cooling systems. 
20 hrs Avg Mu Fade
1; Avg Mu
Fade 2; Avg
Mu Full Test;
Avg Pad
Wear; Max
Rotor Wear
SAE J2707B  A block wear evaluation
performed at various Initial
Brake Speeds, Temperatures,
and Deceleration rates. Test
sections are derived from
various driving scenarios such
as Town, Highway, and
Country Road. Components
are analyzed for wear and
Friction Coefficient
characteristics. 
100 hrs  Avg Mu; Avg
Pad Wear;
Max Rotor
Wear 
 SAE J2784  A dyno simulation of the
FMVSS 135 vehicle test.
Results provide a laboratory
simulation of the corner group
tested, and can be used to
predict vehicle performance
for the specific rotor and
friction type tested.
8 hrs   Avg Mu; Avg
Pad Wear;
Max Rotor
Wear;
Stopping
Distances

Note: The above 4 tests represent the Centric / StopTech Friction Testing Suite for screening friction for Police applications. Friction materials tested are typically subjected to all four tests (new friction couples used in each test). StopTech currently has the capability to test a wide array of specific Police vehicle applications.



Miscellaneous Dyno Testing


 

Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
FMVSS
105/135
Brake corner assemblies are
tested for overall brake output,
friction material effectiveness,
and corner performance. 
This procedure is applicable to all passenger cars and light
trucks up to 3500kg of GVWR.
28 hrs Varies by
test.
Varies by
Test
Simulations of
TUV Tests 
Simulations can be derived
from various TUV test
protocols/standards and
implemented in the
dynamometer. Vehicle corner
assemblies are typically tested
to ensure better data
correlation with real-world
applications. 
Varies by
Test 
Varies by
Test 
 Varies by
Test

 

 

Vehicle System Validation Testing 

Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
FMVSS
105/135
Brake corner assemblies are
tested for overall brake output,
friction material effectiveness,
and corner performance. 
This procedure is applicable to all passenger cars and light
trucks up to 3500kg of GVWR.
28 hrs Varies by
test.
Varies by
Test
Simulations of
TUV Tests 
Simulations can be derived
from various TUV test
protocols/standards and
implemented in the
dynamometer. Vehicle corner
assemblies are typically tested
to ensure better data
correlation with real-world
applications. 
Varies by
Test 
Varies by
Test 
 Varies by
Test

 

Test Description Test Purpose Estimated Dyno Time Data Output Test Requirements
SAE J2522 w/
NVH; RF
Master; MOT
Used primarily on race friction 
materials to classify how the 
coefficient of friction varies across temperatures and apply intensities.
An MOT test is performed at the conclusion to identify the friction 
material's Maximum Operating Temperature.
36 hrs Noise
Events; Avg
Mu Fade 1;
Avg Mu Fade
2; Avg Mu
AK; Avg Pad
Wear AK;
Max Rotor
Wear AK;
Avg Mu RF
Master; Avg
Pad Wear
RF; Max
Rotor Wear
RF; MOTi;
MOTe
--Must utilize an NVH dyno to isolate testing NVH for the SAE J2522 test.

--Requires definition of a caliper, rotor, and brake pad. Part numbers should be submitted to the testing department at the time of the test request submittal.

--Vehicle parameters (form to fill out available upon request) for the desired friction couple need to also be submitted.
High Load A maximum stopping intensity test
used to verify the friction couple's
ability to withstand repeated stops at maximum intensity. 20 Stops are performed from the application's maximum speed at a 1.3G decel rate. A second section performs two 
stops from the application's 
maximum speed at a 1.0G decel rate;
stop 1 has an IBT of 100C, and the
2nd stop is performed immediately following stop 1. This
cycle is repeated 20 times (40 stops)
12 hrs Visual
inspection of
rotor and/or
drive array
hardware for
deformations,
cracks, and
damage.
--Requires definition of a caliper, rotor, and brake pad. Part numbers should be submitted to the testing department at the time of the test request submittal.

--Vehicle parameters (form to fill out available upon request) for the desired friction couple need to be submitted. 
Track
Simulations
Simulated braking events are 
created based on vehicle data taken
 from various tracks across the U.S.
 Linear speed, application intensity, and deceleration are recorded from
a vehicle and exported into custom dynamometer scripts.
4 hrs Varies by
test.
--Requires definition of a caliper, rotor, and brake pad. Part numbers should be submitted to the testing department at the time of the test request submittal.

--Vehicle parameters (form to fill out available upon request) for the desired friction couple need to be submitted.

--Typically vehicle data collected from test sessions at a race track is needed. StopTech does have data from various circuits across the United States however, and can use this data for certain tests. 
Rotor
Deflection
 Quantifies the amount of deflection present in the rotor during a stop
event. 5 stops are performed from
286-20kph at 0.5G, with an IBT of
50C for each stop. A second section 
of 15 stops is repeated 3 times (45 stops). Stop 1 has an IBT of 50C,
and stop 2 has a cycle time of 60
sec. Both stops are performed
 from 100-20kph at 0.5G.
12 hrs   Deflection of
rotor during
stops; max
deflection of
rotor during
testing; Max
rotor temp
 --Must utilize an NVH dyno for setup of the Capacitec sensing system. Capacitive sensors are used to measure the position of the rotor surface relative to the fixed sensor during braking events.

--Requires definition of a caliper, rotor,
and brake pad. Part numbers should be
submitted to the testing department at
the time of the test request submittal.

--Vehicle parameters (form to fill out
available upon request) for the desired
friction couple need to be submitted.
PV Curve
Testing 
 Quantifies the relationship 
between caliper internal pressure and fluid displacement (pressure vs volume). Helps identify internal performance characteristics of calipers (seal groove and seal designs).
1 hr   PV Curve of
caliper
 --Must retain pistons in caliper and
prevent them from extending under
pressure. Custom blocks that fill the
caliper pad cavity can be made for
specific calipers not previously tested.
 Parking Brake
Testing
Various tests can be performed
on parking brake assemblies,
such as hill hold tests and
maximum grade calculations. 
 Varies by
Test
Hill Hold,
Grade, Brake
Torque in
Reverse /
Forward 
--Requires use of Parking Brake
Fixture, and can be used with full
vehicle axles if necessary. 
Rotor Crack
Testing 
Subjects rotor to thermal shock through high energy input stops
and cooling cycles. Demonstrates rotor’s ability to resist cracking. 
 80 hrs Visual
inspection of
rotor
throughout
test for signs
of cracking 

--Requires definition of a caliper, rotor,
and brake pad. Part numbers should be
submitted to the testing department at
the time of the test request submittal.

--Vehicle parameters (form to fill out
available upon request) for the desired
friction couple need to be submitted.