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Antanaitis, David B.
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Benefits and Application Bandwidth of Phenolic Piston Material in Opposed Piston Calipers

General Motors LLC-David B. Antanaitis, Mark Riefe
SBHPP-Chris Ciechoski
Published 2019-09-15 by SAE International in United States
The use of reinforced phenolic composite material in application to hydraulic pistons for brake calipers has been well established in the industry - for sliding calipers (and certain fixed calipers with high piston length to diameter ratios). For decades, customers have enjoyed lower brake fluid temperatures, mass savings, improved corrosion resistance, and smoother brake operation (less judder). However, some persistent concerns remain about the use of phenolic materials for opposed piston calipers. The present work explores two key questions about phenolic piston application in opposed piston calipers. Firstly, do opposed piston calipers see similar benefits? Do high performance aluminum bodied calipers, where the piston may no longer be a dominant heat flow path into the fluid (due to a large amount of conduction and cooling enabled by the housing), still enjoy fluid temperature reductions? Are there still benefits for judder with the much shorter length to diameter ratio the pistons have in these applications? Secondly - it is clear that the much shorter length to diameter ratio of the piston in opposed piston calipers will…
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Braking with a Trailer and Mountain Pass Descent

General Motors LLC-David B. Antanaitis, Brent Lowe
Published 2019-09-15 by SAE International in United States
A truly strange - but very interesting - juxtaposition of thought occurs when considering customer’s deceleration needs for towing heavy trailers in mountainous regions, and the seemingly very different area of sizing brakes for Battery Electric Vehicles (BEV) and other regenerative braking-intensive vehicle applications, versus brakes for heavy-duty trucks and other vehicles rated to tow heavy trailers. The common threads between these two very different categories of vehicles include (a) heavy dependence on the powertrain and other non-brake sources of energy loss to control the speed of the vehicle on the grade and ensure adequate capacity of the brake system, (b) a need to consider descent conditions where towing a heavy trailer is feasible (in the case of heavy trailer towing) or initiating a descent with a full state of charge is realistic (in the case of BEVs), which forces consideration of different descents versus the typical (for brake engineers) mountain peak descent. In this paper, a vehicle operator-based requirement is derived that integrates engine (or motor), transmission (or gearbox), driveline, brake system, brake cooling,…
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Modeling Articulated Brake Component Wear to Assist with Routing Decisions

General Motors LLC-David B. Antanaitis
Published 2018-10-05 by SAE International in United States
Very few activities the brake engineer engages in can induce as much vexation as trying to find a satisfying routing for the flexible brake components such as hoses, wheel speed sensors, and electric parking brake cables. Ever increasing wheel end content, ever decreasing space, more complex suspensions, and bulkier (but lighter weight) suspension components provide quite the morass through which the components must be routed through. When routing is finalized - and free of any major issues - there frequently remains some combinations of articulation position and component tolerances that allow a light “friendly” touch between components (such as a sensor wire and a surface of a bracket or strut tube), or near misses where clearance exists but raises “what if” questions around what would happen if the tolerances would stack up slightly differently on another vehicle. These conditions are usually evaluated painstakingly by experienced engineers, and either corrected with design changes or accepted if deemed of extremely low risk - but these evaluations are generally subjective. The work presented in this paper introduces an…
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Modeling Response Time of Next Generation Electric Brake Boosters

General Motors LLC-David B. Antanaitis
Published 2018-10-05 by SAE International in United States
In the course of this paper, a model suitable for studying the performance - in terms of response time, current draw, and peak pressure capacity - of an electric booster-based brake system is introduced. Some discussion about the need the model is attempting to fulfill and how it fits into the vehicle development process is offered, before explaining the model in full. The equations describing the physics of the model are presented, and an explanation of how the elements of the model are integrated together into an easy to use, fast-running spreadsheet environment is given. Case study examples, validating the model against physical test (hardware in the loop) test results are shown, followed by sensitivity studies testing how changing parameters such as caliper Pressure-Volume curves, hydraulic system flow characteristics, voltage supply, and temperature conditions affect performance.
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Brake System Performance at Higher Mileage

SAE International Journal of Passenger Cars - Mechanical Systems

General Motors LLC-David B. Antanaitis, Matthew Robere
  • Journal Article
  • 2017-01-2502
Published 2017-09-17 by SAE International in United States
The purchase of a new automobile is unquestionably a significant investment for most customers, and with this recognition, comes a correspondingly significant expectation for quality and reliability. Amongst automotive systems -when it comes to considerations of reliability - the brakes (perhaps along with the tires) occupy a rarified position of being located in a harsh environment, subjected to continuous wear throughout their use, and are critical to the safe performance of the vehicle. Maintenance of the brake system is therefore a fact of life for most drivers - something that almost everyone must do, yet given the potentially considerable expense, it is something that of great benefit to minimize. Additionally, the performance of the brake system (like the tires) can change over the useful life of the components, realized in the form of changing friction levels, fluid consumption, and drag at a brake corner level, and realized to the driver in the form of changing pedal effort, travel, response time, and fuel economy.Most studies of brake system performance, and most regulatory requirements that affect the…
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Sizing Next Generation High Performance Brake Systems with Copper Free Linings

SAE International Journal of Passenger Cars - Mechanical Systems

Adam Opel AG-Max Votteler
General Motors LLC-David B. Antanaitis, Michael Shenberger
  • Journal Article
  • 2017-01-2532
Published 2017-09-17 by SAE International in United States
The high performance brake systems of today are usually in a delicate balance - walking the fine line between being overpowered by some of the most potent powertrains, some of the grippiest tires, and some of the most demanding race tracks that the automotive world has ever seen - and saddling the vehicle with excess kilograms of unsprung mass with oversized brakes, forcing significant compromises in drivability with oversized tires and wheels. Brake system design for high performance vehicles has often relied on a very deep understanding of friction material performance (friction, wear, and compressibility) in race track conditions, with sufficient knowledge to enable this razor’s edge design. With significant restrictions in copper content of automotive brake linings becoming reality in California and Washington State in 2021, and a more or less complete phase-out of copper in linings occurring in 2024, one of the key ingredients of high performance linings - critical for heat transfer, high temperature tribofilms, and medium to high temperature friction - can no longer be used.This paper looks at dynamometer-based performance…
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Development and Validation of the SAE J3052 High Pressure Differential Flow Rate Recommended Practice

SAE International Journal of Passenger Cars - Mechanical Systems

BWI Group-E Lloyd
General Motors LLC-David B. Antanaitis
  • Journal Article
  • 2017-01-2498
Published 2017-09-17 by SAE International in United States
This paper describes the development work that went into the creation of the SAE J3052 “Brake Hydraulic Component Flow Rate Measurement at High Delta Pressure”, and also shows some example applications. The SAE J3052 recommended practice is intended to measure flow characteristics through brake hydraulic components and subsystems driven by pressure differentials above 1 bar, and was anticipated by the task force to be invoked for components and subsystems for which pressure response characteristics are critical for the operation of the system (such as service brake pressure response and stopping distance, or pressure rise rate of a single hydraulic circuit in response to an Electronic Stability Control command). Data generated by this procedure may be used as a direct assessment of the flow performance of a brake hydraulic component, or they may be used to build subsystem or system-level models.Two significant variants of test methodology were studied, including use of a servo-actuator against a hydraulic cylinder to push fluid through the test specimens at a high rate, and the use of a high pressure pump…
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Vehicle Level Brake Drag Target Setting for EPA Fuel Economy Certification

SAE International Journal of Passenger Cars - Mechanical Systems

General Motors Corporation-David B. Antanaitis
  • Journal Article
  • 2016-01-1925
Published 2016-09-18 by SAE International in United States
The strong focus on reducing brake drag, driven by a historic ramp-up in global fuel economy and carbon emissions standards, has led to renewed research on brake caliper drag behaviors and how to measure them. However, with the increased knowledge of the range of drag behaviors that a caliper can exhibit comes a particularly vexing problem - how should this complex range of behaviors be represented in the overall road load of the vehicle? What conditions are encountered during coastdown and fuel economy testing, and how should brake drag be measured and represented in these conditions? With the Environmental Protection Agency (amongst other regulating agencies around the world) conducting audit testing, and the requirement that published road load values be repeatable within a specified range during these audits, the importance of answering these questions accurately is elevated. This paper studies these questions, and even offers methodology for addressing them. It includes a review of how variation in brake drag can affect fuel economy and carbon emissions certification, a review of the many transient and driver-dependent…
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Further Research into the Role of the Caliper Piston in Brake Roughness

SAE International Journal of Commercial Vehicles

Chris Ciechoski
General Motors Co.-David B. Antanaitis, Mark Riefe
  • Journal Article
  • 2015-01-2667
Published 2015-09-27 by SAE International in United States
Previously published research [1] covering the role of piston material properties in brake torque variation sensitivity and roughness concluded that phenolic pistons have significantly higher low-pressure range compliance than steel pistons, which promotes lower roughness propensity. It also determined that this property could be successfully characterized using a modern generation of direct-acting servo hydraulically actuated brake component compression test stands.This paper covers a subsequent block of research into the role of the caliper piston in brake torque variation sensitivity (BTV sensitivity) and thermal roughness of a brake corner. It includes measurements of hydraulic stiffness of pistons in a “wet” fixture, both with and without a brake pad and multi-layer bonded noise shim. Inertia dynamometer measurements of BTV sensitivity against a machined 20-micron thickness variation rotor with multiple (prototype) phenolic piston geometries, as well as steel pistons with two different piston to bore clearance levels followed. Finally, higher-temperature thermal roughness testing of multiple phenolic piston geometries and steel pistons with tighter and looser piston to bore clearances were run.The results of these studies give some insight…
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Methods for Sizing Brake Pads for High Performance Brakes

SAE International Journal of Materials and Manufacturing

General Motors Co.-David B. Antanaitis
  • Journal Article
  • 2015-01-2679
Published 2015-09-27 by SAE International in United States
An aspect of high performance brake design that has remained strikingly empirical is that of determining the correct sizing of the brake pad - in terms of both area and volume - to match well with a high performance vehicle application. Too small of a pad risks issues with fade and wear life on the track, and too large has significant penalties in cost, mass, and packaging space of the caliper, along with difficulties in maintaining adequate caliper stiffness and its impact on pedal feel and response time.As most who have spent time around high performance brakes can attest to, there methods for determining minimum brake pad area, usually related in some form or another to the peak power the brake must absorb (functions of vehicle mass and top speed are common). However, the basis for these metrics are often lost (or closely guarded), and provide very little guidance for the effects of the final design (pad area) deviating from the recommended value.This paper proposes methods, justified with dynamometer and vehicle test data, to determine…
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