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Make Some Waves-2

"Ah, what might have been". Someone once wrote that those constituted the saddest words in the English language.
They certainly could apply to me.
I once had the privilege of designing tires for an attempt at the land speed record. This was another skirmish in the battle between Art Arfons and Craig Breedlove for "fastest man" title.
I was tasked with designing and producing tires that would reliably run to a speed of 650 mph, while accepting the cars normal load, and coping with a double over-load on the right rears occurring at engine (G.E. J-79) shut-down.
Our dynamometers could easily accomplish the load and speed regimes that I required.
I inherited a wheel bearing installation and set up from previous activities.
I never questioned the wisdom of using tapered roller bearings and providing them with a specified axial pre-load.
I assumed that when we would experience a tire failure during testing, that the white-hot bearings that spewed from the hubs were the result of the dying tire's input to the hub.
Only recently have I come by the information that roller bearings are not the bearings of choice for applications involving high rotational speeds. Furthermore, that pre-loading those bearings in an axial direction prevents the rollers from rotating. This results in rollers skidding on their races. This friction produces extreme temperatures and a high torque load on the tire.
So I was "shooting myself in the foot". The tire was seeing higher and higher drag forces as it was being accelerated to higher and higher speeds. This represented an increasing vertical deflection, which the tire "saw" as load.
Roller bearings still see applications in the airline industry, and "pre-load" specifications exist and are used.
N.A.S.A. once presented Space Shuttle documentation that stated that a man could not physically rotate an installed, un-loaded tire-wheel assembly on that vehicle.
Someone should undertake to do what I SHOULD have done years ago, and discover the source and documentation of the pre-load philosophy that exists to this day.
Had I questioned this a long time ago, we might have avoided a melted right front wheel bearing and the resulting crash that prevented our becoming record holders.
Someone doing this today may prevent an accident befalling the Shuttle, or some other high speed user.

Bill Woodall







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