18-10-2021, 09:36 PM
(This post was last modified: 18-10-2021, 09:59 PM by Bob Culver.)
Thanks all for excellent photos.
I have a collection of axles which have failed due hammering of the key. But the cars were not completely immobilised so such axles survive and owners retained as there seems a prospect of repairing. The number of distorts the statistics!
Illustrated is a different failure due bending, some from several directions, typical of weight bearing rotating axles. From comments here it seems transverse failure is not uncommon. When tested very many axles show cracks at the key but these tend to follow the curve of the keyway and seem to proceed very slowly.
For those not versed in such matters fatigue cracks advance slowly over thousands of miles gaining speed until the very small remaining metal, clearly distinguishable, finally lets go.
Any slight defect encourages a crack. Oddly the hardness indentation seems to cause this, although often fatigue cracks steer around such compressions (which obseravation prompted the practice of shot peining). On the key side, did the crack start at the key edge? Is there any other trigger, such as a turning mark?
If the key is entirely welllinside the taper, and the taper is a tight fit esp at the thick end, the key should have no influence on crack formation. but some axles seem to heve the key too close to the e hub edge.
(And for the newbies. The Seven axle is defined as 3/4 floating. The car weight is not born by the axle but the tilting force, as when cornering, is. Any bend in the axle or wheel buckle does not help. Curiously with stub axles as on hard driven cars and on trailers , failure often occurs from the top due cornering load.)
I had great difficulty separating the taper to test my axles some time ago but I did not check beyond the key. Now feel compelled to do all again!
I have a collection of axles which have failed due hammering of the key. But the cars were not completely immobilised so such axles survive and owners retained as there seems a prospect of repairing. The number of distorts the statistics!
Illustrated is a different failure due bending, some from several directions, typical of weight bearing rotating axles. From comments here it seems transverse failure is not uncommon. When tested very many axles show cracks at the key but these tend to follow the curve of the keyway and seem to proceed very slowly.
For those not versed in such matters fatigue cracks advance slowly over thousands of miles gaining speed until the very small remaining metal, clearly distinguishable, finally lets go.
Any slight defect encourages a crack. Oddly the hardness indentation seems to cause this, although often fatigue cracks steer around such compressions (which obseravation prompted the practice of shot peining). On the key side, did the crack start at the key edge? Is there any other trigger, such as a turning mark?
If the key is entirely welllinside the taper, and the taper is a tight fit esp at the thick end, the key should have no influence on crack formation. but some axles seem to heve the key too close to the e hub edge.
(And for the newbies. The Seven axle is defined as 3/4 floating. The car weight is not born by the axle but the tilting force, as when cornering, is. Any bend in the axle or wheel buckle does not help. Curiously with stub axles as on hard driven cars and on trailers , failure often occurs from the top due cornering load.)
I had great difficulty separating the taper to test my axles some time ago but I did not check beyond the key. Now feel compelled to do all again!