Suspension D.J. Conroy

Last year Designed with existing frame Did not use suspension analysis programming A-arms not easily adjustable Hard to assemble

This year Design frame around suspension Find optimum geometry using Lotus Make adjustment, machining, and assembly much easier

Geometry Analyzed using lotus software Mounting points dictate much of the frame layout

Different Set-ups

Most Important Aspects Castor Camber Toe Roll center height

Optimum Settings -1° camber (static) Front toe 5° of castor 1° change per inch bump/droop Front toe -1° toe in static (positive with lotus sign convention) Minimal change in bump/droop 5° of castor Roll center height of about 2 in Stay positive through bump/droop Converging A-arms

Mounting lower than 6in. (2in. shown)

6in. pentagon

Pentagon Specs: 1° roll: 6.5° Roll Center: Toe: Static: 0.8in 1 in bump: -1in 1 in bump: -12° 1in droop: 0.7in 1in droop: 14.5° Camber: 1° roll: 6.5° Static: -1° 1 in bump: -2.05° 1in droop: -0.25°

6in. octagon

Frame sketch

Octagon Specs: 1° roll: + 2.5° Roll Center: Toe: Static: 2.7in 1 in bump: 1in 1 in bump: -5° 1in droop: 4in 1in droop: 7° Camber: 1° roll: + 2.5° Static: -1° 1 in bump: -2.2° 1in droop: .1°

Octagon vs. Pentagon Advantages: Disadvantages: Lower and shorter (from bottom to top of frame) Lower COG Don’t need to worry about a raised front end Better mounting of steering rack Much less bump steer Disadvantages: Heavier More frame members

My opinion: The couple extra frame members and 5 lbs max additional un-sprung weight is worth it to have a much lower center of gravity and much less bump steer.

A arm Dimensions Upper: Lower: Forward arm 15.08in Trailing arm 14.70in Difference: .38in Angle: 51.7° Lower: Forward arm: 15.73in Trailing arm: 16.09in Difference: .36in Angle: 48.2°

Materials Steel Carbon Fiber Good: Bad: Easy to weld Light weight Cheap Bad: Expensive Heavy Hard to bond to steel

Manufacturing and Assembly Rod ends with built in spacers Mill push rod mounts Use steel or carbon fiber rods Jig: Accurate 3 points Could use mill table

Adjustability Exposed outer rod end:

Forces on Wheel

A-Arm Forces

Breaking: Verticle: Lateral: tyre: 217.7 lb Top arm: 114.3 lb Bottom arm: 332 lb Verticle: tyre: 580.6 lb Top arm: 290 lb Bottom arm: 290lb Lateral: Tyre: 290.3 lb Top arm: 152.4 lb Bottom arm: 442.7 lb