Pitt | Swanson Engineering
How Do Our Cars Stop?

2015 University of Maryland Regional Competition Car: "Walt"

Stopping Mechanism: Ion Exchange Resin Bead Reaction

  • Aqueous NaOH is put in solution with salt, water, and an acid-base indicator as a visual aid
  • Addition of ion exchange resin beads will decrease the pH of the solution which is monitored by the probe
  • Once it reaches the desired pH stoppage of the motors is triggered by the probe 
  • Depending on the amount of NaOH, Resin Beads, and the pH the probe is set to check for, the car will run for different amounts of time/distances


  • All parts of the stopping mechanism are housed within the same double containment as the reaction vessels
  • Mechanism is found in a separate compartment from the vessels to avoid contamination of other chemicals used
  • Chemicals are properly disposed of in a base waste container after completion of each run

2016 Regional Competition Prototype Car: "Jesse"

Proposed Stopping Mechanism: Iodine Clock Reaction 

H2O2 (aq) + 2H+ (aq) + 2 I- (aq)  2 H2O (l) + I2(aq) 

2 S2O32-(aq) + I2(aq) S4O6 2-(aq) + 2 I- (aq) 

2 I3- (aq) +starch   black starch-I5-complex + I- (aq)