ahamay wrote:
billd wrote:
ahamay wrote:
The hollow axles are stronger than solid axles, not to mention lighter.

Correction: If they are metallurgically identical, they are lighter but not stronger !
(Please don't make me prove it. The formulas are complicated.)

BillD in Michigan

I am ready, calculator in hand. No one said same metallurgically identical. I have axles from gsx1000r and they are hollow and light weight. Nor are they magnetic. They have to be strong for that application. What metal is it made from? I don't know. Tubing is stronger than bar. That is why they use it in fencing, roll cages, aircraft frames, and antenna towers, etc.

a lot of general statements in there....I think BillD is going to have to make you read Roark's handbook and then he will challenge you to a debate! I have my money on Bill in this instance.

Aw! Just when I was getting used to the simplicity of this site! Thanks fireman922.

Ratl.

the reason the axle is hollow, it's made of that rare exotic alloy, unobtainium

ahamay wrote:
billd wrote:
ahamay wrote:
The hollow axles are stronger than solid axles, not to mention lighter.

Correction: If they are metallurgically identical, they are lighter but not stronger !
(Please don't make me prove it. The formulas are complicated.)

BillD in Michigan

I am ready, calculator in hand. No one said same metallurgically identical. I have axles from gsx1000r and they are hollow and light weight. Nor are they magnetic. They have to be strong for that application. What metal is it made from? I don't know. Tubing is stronger than bar. That is why they use it in fencing, roll cages, aircraft frames, and antenna towers, etc.

Ahamay,
Apparently you are an engineer but need a refresher on your formulas from your strength and mechanics of materials classes. So here they are:
It is likely that bending rather than straight tensile pulling is going to be your predominant loading on an axle shaft, so you have to compare section modulus figures.

For a tube the section modulus is (pi/32)*(D^4 - d^4)/D

For a rod the section modulus is (pi/32)*(d^3)

Where D is the outside diameter of the tube or rod and d is the inside diameter of the tube. D^4, for example means D*D*D*D.

Obviously you can get a comparative estimate of weights per foot by comparing cross sectional areas: (pi/4)*D^2 for a rod, (pi/4)*(D^2 - d^2) for a tube.

Structural failure first occurs when the bending stress at the very outside surface reaches yield or in the case of composites more likely the ultimate tensile strength of the material.

Weight for weight tube will be stronger than solid round, so you have to calculate the cross sectional area of the rod, then select a tube with equal or lower cross section (lower = lighter), then check the section modulus of the selected tube is higher than the rod.

So as you can see from these calculations, a solid axle shaft that has the same O.D. as a hollow axle shaft IS stronger but it is also much heavier. However, a hollow axle shaft that is the same weight per inch as a solid axle shaft IS stronger. In this case the tube would be larger in O.D. than the solid. Obviously, both the tube and the solid would have to be metallurgically identical to make a sensible comparison.
OK?

BillD

On top of being lighter, a hollow tube disapates heat better, keeping your bearings cooler. That's why I haven't done like some guys & put chrome covers over mine, I want the heat to escape.

billd wrote:
ahamay wrote:
billd wrote:
ahamay wrote:
The hollow axles are stronger than solid axles, not to mention lighter.

Correction: If they are metallurgically identical, they are lighter but not stronger !
(Please don't make me prove it. The formulas are complicated.)

BillD in Michigan

I am ready, calculator in hand. No one said same metallurgically identical. I have axles from gsx1000r and they are hollow and light weight. Nor are they magnetic. They have to be strong for that application. What metal is it made from? I don't know. Tubing is stronger than bar. That is why they use it in fencing, roll cages, aircraft frames, and antenna towers, etc.

Ahamay,
Apparently you are an engineer but need a refresher on your formulas from your strength and mechanics of materials classes. So here they are:
It is likely that bending rather than straight tensile pulling is going to be your predominant loading on an axle shaft, so you have to compare section modulus figures.

For a tube the section modulus is (pi/32)*(D^4 - d^4)/D

For a rod the section modulus is (pi/32)*(d^3)

Where D is the outside diameter of the tube or rod and d is the inside diameter of the tube. D^4, for example means D*D*D*D.

Obviously you can get a comparative estimate of weights per foot by comparing cross sectional areas: (pi/4)*D^2 for a rod, (pi/4)*(D^2 - d^2) for a tube.

Structural failure first occurs when the bending stress at the very outside surface reaches yield or in the case of composites more likely the ultimate tensile strength of the material.

Weight for weight tube will be stronger than solid round, so you have to calculate the cross sectional area of the rod, then select a tube with equal or lower cross section (lower = lighter), then check the section modulus of the selected tube is higher than the rod.

So as you can see from these calculations, a solid axle shaft that has the same O.D. as a hollow axle shaft IS stronger but it is also much heavier. However, a hollow axle shaft that is the same weight per inch as a solid axle shaft IS stronger. In this case the tube would be larger in O.D. than the solid. Obviously, both the tube and the solid would have to be metallurgically identical to make a sensible comparison.
OK?

BillD

Yep you are right. I am an engineer, EE, not ME. The EE was military training only and it only briefly touched on mechanical. And even that was the most basic pertaining to hardware stack and vibrational survival. If we needed Mechanical Engineering we called them. They liked to keep the disciplines separate because a lot of the work we did had sections of "Need to Know" on the blueprints and schematics. As far as the axles go my statements were rather generalized. Antenna towers are still hollow, as are roll cages. The GSXR1000R axles are much larger in diameter than my fj1200 or my gsxr750 axles. In fact you are correct. So there, let that be a lesson to me! So is the end of my spanking?

ahamay,

We all learned something.

Now we need study properties of thermal dynamics to figure out heat transfer of the axles with and without axle covers.

I never use the brakes, so heat buildup isn't a worry for me..