650:342Analysis And Design of Custom

Hydraulic Clutch Pedal

Zachariah JohnHenry Helfman

Bernadette Bautista

Previous Pedal Design

• Uses rod and crank system• Requires adjustment to compensate clutch wear• Has 6 major high wear surfaces• Mechanical geometry (pivot points) limits applications

Bell Crank

Cable Clutch System

Non-Hydraulic Clutch Linkage Systems

Hydraulic Clutch System Advantages

1. Easy to mount master cylinder on flat surface behind pedal (firewall)

2. Few wear items which have much lower wear than other clutch linkage systems

3. Piston/Cylinder assemblies automatically compensate for clutch surface wear and need no adjustment

Improved Design Goals

1. Make a system which allows installation of hydraulic clutch pedal when standard parts are unavailable

2. Use mostly production or aftermarket parts and keep custom manufactured parts to a minimum to be cost effective and practical

3. Use simple system that can be implemented to any vehicle’s firewall section (space permitting)

Model Information

• The improved pedal is a modified bell crank unit retrofitted to operate a Hydraulic Master Cylinder.

• An actuation arm which joins the pedal to the master cylinder rod is welded to the original pedal.

• The pedal has a weight of 1.869 lb (4.8359E-03 lbm).

• Galvanized Annealed Steel is the material used in the pedal.

Material Properties for Galvanized Annealed Steel

• Modulus of Elasticity[psi] 2.7993E+07

Density [lbm/in^3] 7.5148E-04

Poisson's Ratio 0.2900

Thermal Expansion

Coefficient [ 1/degF ] 9.8889E-06

• Constrained and loaded with 20 lb applied load to lower base pedal surface

• Analyzed with Ansys

FEA Loads & Constraints

Analysis Specifications

• Applied Loads:• Type Entity X Y Force [ lb ] Area 91.56 8.010 • Force [ lb ] Area -14.14 -14.14• Reaction Forces [ lb ]:• X Y Z• -76.867 -22.103 -4.12794E-04• Total Moment [ lb-in ]:• X Y Z

7.4646 -85.318 98.502

Equivalent Stress, Maximum Principal Stress and Critical Point

Fatigue Test

• The Critical Stress (SC) on the clutch pedal is 24.750 ksi.

• 108 Cycle Strength (endurance limit):

Sn = Sn' * CL * CG * CS Sn' = 0.5*SU

= 25.48125 ksi. SU = 151 ksi

CL = 1

CG = 0.75

CS = 0.4

Since SC < Sn fatigue life is infinite.

Corrosion & Wear Analysis

• Pedal surfaces are painted • Every frictional surface is lightly greased and

insulated with a plastic bushing so anodic corrosion of the material is irrelevant.

• Rod is in contact with the pedal, which gives way to adhesive wear.

• Wear: W= KHFS K=10-3 = 5.0744*10-8 in.3 H= 452.832*103 psi. = 8.3154*10-4 mm.3 F = 91.9134 lb. S = 0.25 in.

Disposal

• Pedal assembly will most likely be salvaged at end of vehicle’s useful life or recycled with the rest of the vehicle