Formula SAE: What a Few Car College Gear Heads Can Do In Their Free Time

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UD’s car makes use of Fox Racing DHX 5.0 shocks.  These shocks are actually designed to be used on mountain bikes.  Bicycle shocks on a race car?  Believe it.  Each corner of the car, with driver, weighs around 200 pounds.  This is well under Fox’s design requirements.  The shocks have compression and rebound adjustment, as well as Nitrogen pressure and bump adjustment.  The knobs on the damper actually make a huge difference.  Threaded spring perches are adjustable for ride height.  The dampers also have remote reservoirs for consistency.  For the price there are few better options for an SAE car.  The shocks have been used on three different cars and are just as good now as the day they were new.  Talk about quality!  The springs are 250lb-in.

Fox Racing Shocks

Fox Racing Mountain Bike Shocks are used.  Bike shocks are plenty for this tiny car and relatively cheap.  They are also very light and fully adjustable.  Note the anodized aluminum rocker arm that is actuated by the pushrod.  It also activates the sway bar.  All of the knobs are easy to reach for quick adjustment.  The lower mount for this shock has actually been installed backwards.  The rebound knob is on the bottom and should be facing out, but in the rush to assemble the car it was mistakenly installed backwards.

 

UD FSAE Rear suspension

Rear suspension is nearly identical to the front.  The arms are slightly different lengths and the damper placement is different compared to the front.  The rear hubs are outsourced, but everything else is built in House in UD’s student machine shop.  A big thank you to machinist Steve Beard for helping the team run all the machinery and keeping us safe.

UD’s SAE car uses 13” Kaiser three-piece aluminum wheels for both the front and rear.  Some teams use a staggered setup, but UD adds track width to the back of the car through control arm length.  This allows the team to use a single size wheel, keeping costs low.  For competition, UD uses a soft compound Goodyear slick.  For practice UD uses a Hoosier slick which is much harder.  UD also has a set of Hoosier rain tires, but they sit in a closet un-mounted because it hardly rains in So Cal.  Each wheel and tire combo weighs very little: only 10 pounds per corner.  In four years, UD’s SAE team has been unable to bend a wheel, even when changing tires using big screwdrivers for tire spoons.

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Goodyear slicks are mounted to Kaiser 13” wheels.  For practice the team uses Hoosier slicks which are harder, but last longer.  UD did use a single lug wheel at one time, but FSAE rules mandate a cotter pin to hold the nut in place.  This became a major hassle and since there are no pit stops, standard 4-lug wheels are easier to source and easier to work with when wrenching on the car.

The brakes were this author’s specialty and lots of calculations were performed to be certain that the brakes would be up to snuff.  A pair of Tilton master cylinders provide pressure to the calipers.  They are bolted to a Wilwood brake pedal which has a balancing bar to allow brake bias adjustments.  Earl’s stainless steel brake lines connect the calipers to the master cylinders.  The brakes themselves are Wilwood PS1 calipers on UD made 10” rotors.  The PS1 caliper is a dual piston aluminum caliper meant for very small cars such as go karts or SAE cars.  Each caliper weighs less than a pound.  These calipers have been used for many seasons on four different SAE cars and have been rock solid in every car, never failing the team once.  The rotors are drilled and slotted to shave weight and provide a vent for evacuating spent brake pad gasses.  A Tilton adjustment knob is installed to allow driver control of brake bias.  PS1 calipers are used at all four corners since weight transfer is not large.  Adjusting the bias through the balance bar helps keep sphincter puckering stops to a minimum.  Motul RBF600 brake fluid is used, based upon the glowing praise received here on MotoIQ. 

Machined FSAE billet brakes

Brakes are identical front and rear.  They use Wilwood PS1 calipers over custom built 10” rotors.  Each rotor takes one hour to machine from steel stock.  The program is very simple, but because it must be reset for each set of holes or each slot, the process is very time consuming and boring.

 

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