Our Technical Programs
Accident Investigations at the 500Speaker - Dennis Hunley and Clinton Oster
USAC Safety Inspection Committee / Quality Assurance Co.
Topic: Accident Investigations at the 500 Dennis Hunley began with an overview of the testing program for racecars.
USAC (United States Automobile Club) has a long and successful history of using NDT to protect race car drivers and equipment. In 1936 Eddie Rickenbacher (then head of the Indianapolis 500) came to an arrangement with new Magnaflux Corp. to use magnetic particle inspection on steering arms and front end spindles which had been failing on several race cars. Several other Indianapolis based metallurgists were involved, including George Shubat, Nobel York, and Doug Taylor.
Currently USAC approves 50 testing facilities across the country and in Europe for the inspection of parts from racecars in various races. Racecars components are inspected at least 5 times per year, and with higher budget teams the inspections take place prior to each racing event.
Six methods of Non-destructive inspection are currently used for these inspetions.:
Liquid Penetrant Inspection is performed on many critical components including all magnesium wheels and brackets on the cars.
Magnetic Partical Inspection (including as many as eight different "shots") is performed on most ferrous components. Frequently cracks in over-stressed case hardened pieces are detected by this test.
Radiography is used to examine all wheels used on every race car.
Utrasonic testing of the portable type is used to verify correct wall thickness on many components of the race car including all tubular components.
VideoProbe is used both the spot defects in assembly and also to detect any attempts to hide "illegal" devices which could be inserted in fuel tanks or other non-visable locations.
Hardness Testing is used to verify components are properly hardened and also to check the rubber quality of the tires.
For the Indianapolis Racing League a NDT laboratory on wheels is in operation which travels to each race site to provide all of the above inspections. This facility will be displayed at the upcoming "Materials Conference" in Indianapolis, this coming fall.
In addition to specifying and conducting tests, USAC surveys and audits 50 independent certified testing facilities around the US and four in Europe. Inspectors for Magnetic Particle, Liquid Penetrant, and Radiography techniques are certified as Level II inspectors in accordance with the ASNT (American Society of Non-destructive Testing) SNT TC-1A guidelines.
At the Indianapolis 500 alone, several hundred problem parts have been found between qualification and race day, probably avoiding several serious accidents.
Clinton Oster provided detail about the investigation of several actual accidents, as well as the philosophy of the investigation process.
Relating to the Indianapolis Racing League, we first must ask the question - - What are we trying to accomplish? The answer boils down to these broad goals: 1) Eliminate injuries and fatalities 2) Eliminate accidents caused by equipment failure.
What is the first question that an "accident investigation" is trying to answer? Was the accident the result of equipment failure, or driver error?
The second question to be answered is: How well was the driver (and other drivers and spectators) protected? Was debris a hazard?
The techniques used to investigate the accident are:
1) Review accident video and photographs
2) Visual inspection of the racecar and debris
3) Analyis of the "impact accelerometer" data (the race car's black box).
4) Failure analysis of any broken components of the race car.
The existence of video footage and digital photo images has been very useful in determining initial accident cause (particularly if driver error or some component of the car was initially responsible).
A thorough visual inspection is made of the Suspension, chassis, aerodynamic components, engine and transmission, and also the wheels and tires.
The impact accelerometer provides data useful in evaluating the capability of components to be "crash worthy". It surprises many to find out that in open wheel racing, a 50g force is not even considered to be much of a hit. With today's designs and protective gear, drivers "walk away" unharmed from crashes involving as much as 150g force on initial impact. It is a strange comparison that "airlines" design their seats and seatbelt to be effective only up to 15g (claiming that no-one could survive impacts greater than this, yet race car drivers walk away from impacts of ten times this amount. There is a trend to begin recording actual "delta-Vee" acceleration rates rather than just the "g-force". From such measurements, more would be know about the actual energy involved in various crash situations, and with various car designs.
Failure analysis ultimately can lead to better design of components.
This talk included excellent pictorial illustrations of various accident investigations, which unfortunately cannot be reproduced in this summary.