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CAD Design (April 2020)
CAD Assembly
Master Sketch
Changes from Spring/Fall 2019
Removed clevis to make manufacturing easier.
Created connections(mounts) to chassis.
Found new rack in bay (unknown PN) approx. 130mm of travel.
Design geometry has been subjected to FEA.
Detailed design of all components.
Converted design into master driven.
Most fasteners are various lengths of M6/M8.
Steering Geometry
It was found the most optimal way to achieve perfect Ackerman is to align the steering arm at the same angle as the line that connects the intersection of the track and wheelbase to the middle of the back wheelbase line.
Model of Ackerman can be found: GrabCAD\MSXIV\Development\Dynamics\Steering
In the file “Ackerman 2D model” or “Overlay”.
Overlay contains the master sketch with the Ackerman model.
~85.6mm of travel in model.
Overlay model with wheels turned at 26 degrees.
Steering Column
Collapse occurs in the upper column, with min ~3in of travel.
Includes u-joint to allow the unit to tilt, unknown if this will be pursued.
Tie Rod
Design similar to push rod.
VR3 tube used in the middle with threaded components welded on the sides.
Welded components are machined and give greater freedom in thread sizes (vs VR3 tube ID).
Tie rod, transparent component is the VR3 tube. threaded components inserted on both sides.
Rack Mount
An angled rack mount was created to accommodate the angle at which a driver holds the steering wheel.
By putting in an angled mount it allows the driver to angle their wrists down as opposed to up when driving.
Tilting the wrist down occurs whenever the perpendicular to the rack is above the steering wheel point.
Sketch of column, circled yellow lines is orientation of rack straight vs angled.
...
Rack mount with screws shown.
Side view of mount, rack is tilted 15 degrees.
Boundary Conditions for FEA/Steering Arm Force
Hand Calculations
Steering arm moment arm dimensions.
Steering Arm FEA Setup and Results
Model found in GrabCAD\MSXIV\Development\Dynamics\Suspension\Edward's Parts - “Assem1 for sim”.
Setup:
Fixtures: 2 fixed faces, and two fixed hinges (at UCA and LCA attachment points).
2 bolt connections with no pre-load torque.
Force along the direction specified earlier.
Overview of setup.
Two fixed faces.
Two fixed hinges.
Contact set and bolt connections.
2.73MPa is the max force experience, which is a little less than a SF of 2 with the yield strength of 7071 aluminum at 5MPa.
The result is most likely surface level forces, so this condition is acceptable.
Steering Arm Simulation Results.