09-05-2018, 06:59 AM
For fatigue cracks of long standing in any component, a brown colouration from the fretting of the surfaces is common.
As with cranks, it is apparent from the large number cracked that the condition must often exist for a large part of total life (which is not the case with revolving bending fatigue tests of plain rods at constant load)
Fatigue is reckoned to be much increased in corrosive conditions. It is prudent to keep the arms, stub axles etc greased.
In simple bending the cracks generally seem to run near straight between the ends.
It would be interesting to see how extensive was fatigue part of crack in arms failed in normal use. In crankshafts crack extends a huge way through.
The original arm in my car failed at about 60,000 and that with a last owner careful not to tug on the wheel. Like many older cars it had been in a crash. However a few overloads sometimes extends fatigue life!
The shank failures are a concern as new arms the same. It is essential the arm seats properly and not seat primarily on the vertical centre line. As with big end bolts keeping tight protects flange from fatigue.
If a crack can be established as definitely only 3/32 or so deep it is not going to fail tomorrow or even next year, but by eye depth is uncertain. But if someone fights the car in and out of a tight park every day life may be short....
Older motorist were taught not to haul on the steering wheel but many owners of moderns have become especially used to turning the wheel with car stationary. (It is remarkable that the modest proportioned components of moderns seem to stand this repeated action. Many owners must chirp the wide tyres almost every day.)
As before, if Seven wedged in a tight park, best to get out and pull the wheels by hand.
Where dependent on magnet the poles should span the crack.
Google currently produces some interesting pics of fatigue cracks in RR Trent turbine blades.
The advert dependent newspapers, which adopt the role of drama queen about asbestos pipes in schools etc, accept the glib played down reports from the airlines without speculation.
As with cranks, it is apparent from the large number cracked that the condition must often exist for a large part of total life (which is not the case with revolving bending fatigue tests of plain rods at constant load)
Fatigue is reckoned to be much increased in corrosive conditions. It is prudent to keep the arms, stub axles etc greased.
In simple bending the cracks generally seem to run near straight between the ends.
It would be interesting to see how extensive was fatigue part of crack in arms failed in normal use. In crankshafts crack extends a huge way through.
The original arm in my car failed at about 60,000 and that with a last owner careful not to tug on the wheel. Like many older cars it had been in a crash. However a few overloads sometimes extends fatigue life!
The shank failures are a concern as new arms the same. It is essential the arm seats properly and not seat primarily on the vertical centre line. As with big end bolts keeping tight protects flange from fatigue.
If a crack can be established as definitely only 3/32 or so deep it is not going to fail tomorrow or even next year, but by eye depth is uncertain. But if someone fights the car in and out of a tight park every day life may be short....
Older motorist were taught not to haul on the steering wheel but many owners of moderns have become especially used to turning the wheel with car stationary. (It is remarkable that the modest proportioned components of moderns seem to stand this repeated action. Many owners must chirp the wide tyres almost every day.)
As before, if Seven wedged in a tight park, best to get out and pull the wheels by hand.
Where dependent on magnet the poles should span the crack.
Google currently produces some interesting pics of fatigue cracks in RR Trent turbine blades.
The advert dependent newspapers, which adopt the role of drama queen about asbestos pipes in schools etc, accept the glib played down reports from the airlines without speculation.