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FSAE Steering Redesign

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by

Jeremy Seal

on 29 November 2014

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Transcript of FSAE Steering Redesign

Low:
(+)Better for current suspension setup
(+)Lower CG
(+)Safer
(-)Need angular shaft coupler, more free play
(-)Harder to control wheel ergonomics

High:
(+) One straight shaft, less free play
(+) More ergonomic (control wheel angle)
(-) Less safe, rack above legs
(-) Hard to optimize performance with current suspension setup
Presentation Outline
Evaluation of Current System
Design Objectives
Design Ideation Walk-Through
Ergonomic Considerations
Alternative Designs
Proposed Design
Plan for Detailed Design
Proof of Concept and Implementation
Project Management Plan
Feedback and Question Period
Evaluation of Current System
Simple low mounted rack and pinion system with rear steer

Room for Improvement:
Free-play throughout system
Ergonomics limited
Mass and part size optimization
Robustness
Design Objectives
Design Ideation
Linear ranking process of steering sub systems

Top ranking sub systems developed to create 3 alternative designs
FSAE Steering System Redesign
Design Review Presentation
Presented By:

Jeremy Seal
Jason Laylo
Martin Par
Ian Gruenberg
Cameron Medri
Design Alternatives
Three unique designs created using best sub systems

Weighted Decision matrix based on ranked objectives used to selected proposed design
High Mounted Rack Design
Front Steer Double Pinion Design
Optimized Current Design
MIE491 : Capstone Design
Objective

Weight %

Minimize free-play

15
Minimize risk for injury (Safety)*

20
Minimize force needed to turn wheel 3
Minimize total weight 5
Minimize cost 10
Minimize bump steer 8
Increase manufacturability 13
Steering wheel ergonomic position

15
Variable rate steering 2
Optimize steering ratio 4
Optimize Ackerman geometry 5

Rack Placement
Rack and Pinion
Pitman Arm Type
Simple
Low Weight
Compact
More Mechanical Advantage
Less Wear
Many linkages, spacious
Heavy
Rotary to Linear Motion
Affects steering performance, ergonomics, and safety

Performance:
Bump Steer: Tie rod point Line AA
Ackermann Steering: Aft gives positive
Y
Z
X
Minimum Bump Steer
Rack Placement
Shaft Joints and Couplers
Steering Shaft
Components

Proposed Design
Proof of Concept and Implementation
Full prototype of steering system will be manufactured and assembled (parts can be used in future FSAE cars)

Interactive test rig will be created to feel steering and ergonomic design

Virtual testing of loads and steering geometry will be used to validate
Plan For Detailed Design
Project Management Plan
Thank you...

Questions?

Composed of the bulk of design work
Part sizing at industry scale
Purchased parts research and order
Plan for machining of custom parts
Shaft and
Boundary Connections
(Cont'd)
Steering Column Support
(Bearing Housing)
(+) Radial Support Bearings
Intermediate
Housing
Integrated
Housing
(+/-) Easily manufacturable
and relatively cheap, but
is compromised by the
increased number of parts
and the added weight
(brings up vehicle CG)
Conclusion is inconclusive. Further exploration required in technical design
Radial-Support
Bearings
(+) Support of radial
loads and allows
rotational motion
Rolling-Element
Bearings
Plain
Bearings
(+) One-piece construction
with a larger bearing surface. More beneficial
at this size scale
(-) Moving elements subject to eventual wear and fatigue failure
Possible combination of
these bearing types is plausible in technical design
Angular Misalignment
Couplers
Bevel Gears
(+) can reduce force with gear ratio
(+) constant velocity
(-) major source of free play
(-) more expensive and heavier for entire gearbox
(-) must be mounted high in chassis
(-) requires lubrication
U-Joint
(+) cheap and lightweight
(+) readily available off the shelf
(-) non constant angular velocity
(-) restricted to 30 degree max operating angle
Double U-Joint
(+) much larger operating angle
(+) constant angular velocity
(+) readily available
(-) more sources of free play
Helical Coupler
(+) one piece design reduces backlash
(+) no moving parts means low maintenance
(+) variety of capabilities depending on material
(-) not readily available
(-) exerts transverse stress on shafts
Rzeppa CV Joint
Shifter Mechanism
(+) Effective shifting
of vehicle into a
different gear
Paddle Shifter
Shifter Lever
(+) Simple construction
and allows driver to keep
hands on wheel at all times
(-) Requires creation of a new sub-assembly, and requires one hand to be removed from wheel
Paddle Shifter is the only reasonable option in this case considering design objectives
Ergonomic
Considerations
Steering Wheel Placement:
Location conforms to SAE rules
Placement in ideal "sweet spot" that
accommodates drivers of varying sizes

Steering Wheel Angle:
Dependent on U-Joint placement and angle between steering column segments
Also directly correlated to driver's seat
angle and the extent of the recline
(or lack thereof)
Detailed Design Phase I
12/3/2014 - 12/19/2014
Required to be implemented in vehicle based on SAE rules

Specification of ideal stock disconnect suited for project will be conducted during the detailed design phase
Quick Disconnect Mechanism
(+/-) Decreases overall part count and weight, but is compromised by the increased complexity of fabrication
Perfect Ackermann
Z
Initial steering geometry optimization (SusProg)

Rough CAD models (SolidWorks)

Preliminary Materials Selection (CES EduPak)

Begin specifying stock parts

Modeling system through load calculations
Detailed Design Phase II
1/5/2015 - 2/13/2015
Finite Element Analysis simulations (ANSYS)

Dynamic Simulations (MSC Adams)

--> Re-iteration loop, calculation and simulation refinement

Finalized parts specifications and system BOM

Creation of engineering drawings with GD&T
Benchmarking 2015 System
Tentative: 1/26/2015 - 2/13/2015
If client has 2015 system fitted onto vehicle, we intend to accompany them for field testing to get some baseline measurements to use as reference for comparing to our design
FDS Documentation Phase
1/26/2015 - 3/27/2015
Documentation of numerical results, simulations, and stock component selection process

Creation of digital visuals and simulation videos

Poster creation, CI mock presentation, and planning of showcase logistics
Prototype and Rig Fabrication Phase
2/16/2015 - 4/7/2015
Fabrication of custom components

Ordering standardized components (accounting for shipping lead times)

Final assembly of the prototype steering system

Cameron to lead rig design, planning, and construction. Will be used as interactive rig for audience at Capstone Showcase
(+) large operating angle, 50 deg max
(-) larger in size and weight
(-) requires grease for heat dissipation and lubrication
(-) not readily available
Bolt Through
(+) easy to apply
(+) cost effective
(-) vibration can loosen bolt and produce free play
(-) difficult to reposition
Splined Ends
(+) allows for incremental positioning
(+) readily available
(+) potential for hollow shafts
(+) potential for low free play
(-) difficult to modify splines
DD Ends
(+) readily available
(+) can be modified easily
(+) potential for low free play
(-) can only be phased 180 deg
(-) less potential for hollow shaft
Weld
(+) strongest connection
(+) no free play
(-) more difficult to apply
(-) does not allow modification or repositioning
(-) residual stresses are introduced
Main Optimizations:
Free play in bolted shaft connections
Use of DD or splines to fix
Free play of U-joint
Sourcing better design
Part sizes, and material choice
Help save mass
Rack Mounting
Manufacture custom sheath to have two mount points, reduce bending deflections
Wheel position and angle
Measure drivers to find optimal configuration for comfort
Performance Optimization
Reduce bump steer, find ideal Ackermann
Advantages
No shaft joint (Less Free Play)
More ergonomic wheel position
Disadvantages
Not as safe for driver
Higher car CG
Harder to Mount rack, and upright point is crowded
Advantages
Better pinion mounting to frame
More room optimize wheel angle ergonomics (smaller angular misalignment
Disadvantages
Need to move system further forward (less space for feet)
Tie rods at larger angle
Advantages
Easier to manufacture and validate
Room for optimization to limit free play, improve performance and ergonomics
Works well with current car setup
Disadvantages
Need U-joint
Wheel ergonomics are limited
Full transcript