[SystemSafety] Wheel detachment from a moving car

[Scott Nowell]

Nearly thirty years ago I was driving our SUV with a snow plow mounted on the front in a small town in New Hampshire.  The vehicle was driving fine.  Travelling at about 35 mph I applied the brakes and the left front wheel came off and continued down the road at speed until it hit a snow bank and bounced twenty feet in the air.  Fortunately the skids of the raised plow hit the road first, preventing damage to the underside of the vehicle.   

Similar to your partner, the car had been in for service the previous day.  Their best guess was the lug nuts had only been hand tightened.  The ride had seemed OK, but the ice and snow on the road may have obscured any vibration.

Unfortunately it seems likely that any locking wire or cotter pin would also have not been installed.

-----------------------------------------------------------------------
Scott Nowell
Validated Software Corporation
6848 Embarcadero Lane
Carlsbad, CA  92011
Tel: (760) 230-5299
snowell at validatedsoftware.com
www.validatedsoftware.com 




-----Original Message-----
From: systemsafety-bounces at lists.techfak.uni-bielefeld.de [mailto:systemsafety-bounces at lists.techfak.uni-bielefeld.de] On Behalf Of David Crocker
Sent: Thursday, May 21, 2015 7:26 AM
To: The System Safety List
Subject: [SystemSafety] Wheel detachment from a moving car

My partner has a nasty near-accident on Tuesday. While travelling on a dual carriageway at 60mph, she became aware of a new noise from the vehicle. Shortly afterwards, the front nearside wheel detached and she saw it roll into an adjacent field. Fortunately the car did not tip over. She is a skilful driver, so she allowed the vehicle to decelerate without using the brake. She was not rear-ended, and when at a slow speed she drove it into the adjacent grass verge. She was shaken but unharmed. The car is beyond economic repair because the steering assembly and other parts are wrecked.

She had driven 500 miles since having the tyre on that wheel replaced.

This got me thinking:

1. How often do wheels detach from cars while travelling? Are there any figures recorded? Have any fatalities occurred as a result?

2. Why is there no requirement on manufacturers and fitters to use locking wire, a cotter pin, or some other mechanism to ensure that the wheel nuts cannot come off? I notice that some HGVs do use locking wire on the wheel nuts.

--
David Crocker, Escher Technologies Ltd.
http://www.eschertech.com
Tel. +44 (0)20 8144 3265 or +44 (0)7977 211486

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