A Study of Parking Brake Cable Efficiency as Affected

by Construction Type

Paul StoloffBrake Technical Lead Chrysler Group, LLC

PAPER # 2011-01-2380

Park Brake System Efficiency Cable Efficiency◦Force Efficiency◦Travel Efficiency

Cable Testing Test Results◦Force Efficiency, Travel Efficiency and Work

Efficiency◦Other Considerations

hSummary

PAPER # 2011-01-2380

Agenda

PAPER # 2011-01-2380

Park Brake System Efficiency

The mechanical efficiency of a parking brake system is determined by the sum of the losses of all components in the system

Cables represent the greatest contribution to efficiency loss in a typical parking brake system.

Since a parking brake lever delivers force and travel, work efficiency should be understood in order to optimize a system.

Work is not simply the product of force and travel, but rather…

 

Input Force is limited by regulation and customer satisfaction

Input travel is limited by packaging constraints and customer satisfaction

Hence net work is limited. Since cables consume both force and travel

efficiency, small improvements in cable performance can have significant affect on system performance

Where to from here?

PAPER # 2011-01-2380

Cable Efficiency

“Without data, you are just another person with an opinion”, Anonymous

“With data, you are just another person with an analysis”, Anonymous

Independent data from different (biased) sources is insufficient to perform an analysis or draw any conclusions.

Uniform testing is the proper method for gathering data.

PAPER # 2011-01-2380

Cable Testing

A simple cable test stand was developed and validated to measure input/output force and input/output travel under a fixed set of conditions.

PAPER # 2011-01-2380

Cable Testing

Cable samples from four leading cable suppliers were solicited.

The following constructions were tested:

PAPER # 2011-01-2380

Cable Testing

Flat Wire Conduit

Twin Wire Conduit

1x19 Strand

3 Samples 3 Samples

7x7 Strand 3 Samples 3 Samples

The test stand was validated using one sample each of three different constructions that were expected to have measurable differences in performance.

PAPER # 2011-01-2380

Test Validation – Travel and Force Efficiency

Travel efficiency differences were clear and statistically valid.

Force efficiency fell within a very narrow range and was repeatable.

PAPER # 2011-01-2380

Test Validation - Results

The testing was expanded to include all construction combinations from all suppliers; 48 pieces total.

ANOVA analysis of the results showed a strong correlation for strand type.

1x19 Strand – 68.1% Mean

7x7 Strand – 61.1% Mean

PAPER # 2011-01-2380

Test Results – Travel Efficiency

ANOVA analysis of Force Efficiency revealed a moderate effect from Supplier, driven primarily by the poor performance of Supplier D and the good performance of Supplier A.

PAPER # 2011-01-2380

Test Results – Force Efficiency

Work efficiency was calculated using numerical integration.

Of the sixteen combinations, the top eight were all 1x19 strand.

Three of the top four were flat wire conduit.

The worst performer had both the worst travel and worst force efficiency, compounding to create the worst overall performer.

PAPER # 2011-01-2380

Test Results – Work Efficiency

19%

Cable efficiency is not the only consideration in cable design.

Others include◦Flexibility/Stiffness◦Cost◦Corrosion Resistance◦Supplier Strategy◦Application specific issues

PAPER # 2011-01-2380

Other Considerations

A method was demonstrated for quantifying parking brake cable performance.

The method is simple, quick, repeatable, and reliable.

Other variations of parts can be quickly evaluated and compared to previous results.

This procedure provides the engineer the tools to remove the guesswork from cable selection.

Proper selection of cable construction can result in significant improvements in parking brake system performance.

PAPER # 2011-01-2380

Summary