Rohan said:
Dances with Shrapnel said:
This is freshman high school math so do the math ..
Rohan said:
Why then are axles and gudgeon pins large hollow tubes, not thin solid rods ??
It's pretty much spelled out in one or both of the reference articles; when mass and bending stiffness/strength/durability are in play, this is a way to have your cake and eat it; tubes, not solid bars - plain and simple.
Rohan said:
Anyone who can do this math in freshman high scool class is in the genius category..
Especially if they can get it right !!
Get those freshmen then to do the math on these 2 tubes. Same quantity of metal per unit length.
I am with you 100% on this :lol:
But, in all seriousness, the simple math I refer to pertains to the subject of a bolt, drilled or undrilled. A bolt should be used for tension or shear and that's it. Bending is not part of the analysis so analysis or discussion of Moments of Inertia, second, third etc. as in the referenced articles ..... pertains to analysis of bending stress/strain and components in acceleration.
The simple math I referred to is force divided by cross sectional area which yields stress, whether it is in simple shear or simple tension (as applied to a bolt).
An axle is not a bolt application but a round beam in a bending moment; this is where moments of inertia apply. A hollow axle is a tube beam in a bending moment; this is also where moments of inertia apply, this is where improved strength
per unit weight can be achieved. An axle is a completely different application than bolt.
I have instances of drilled transmission through bolts on a few of the race bikes. This is an instance of a bolt having more capacity than actually needed. By drilling it through the tensile load capacity is reduced, the shear capacity is reduced and the strain per unit tension load is increased but it is plenty adequate. This means it was significantly more than adequate for it's intended use as stock.
In the instance of a solid axle, the center core of a solid axle contributes little to nothing to the bending stiffness, this is why some portion of the center can get bored out without much loss in axle stiffness.