Interesting thing I found out about the 10-bolt

[Mega Dogmeat]

Anyways, I kinda finished up my roughshod "analysis" of the GM 10-bolt axle shaft tonite, and ultimatley figuring out all the combined loadings was a little more in-depth that my background would let me finish, however, there is one very interesting thing:

 

It's pretty easy to determine the maximum shear stress on the axle due to torsional twist (aka power from the motor being transmitted through the drivetrain) ... Roughly 4,000 ft-lbs of torque is transmitted through this axle by a 5.3L motor with 3.73 gears.....

 

Knowing that the maximum yeild strength of 4340 steel is 270 KSI, you can figure out the minimum radius of an axle shaft needed to transmit that much power without breaking. I calculated that to be roughly 0.487" ...

 

This is the shear streas due to *ONLY* the torsional loading, it *DOES NOT* included the shear stress induced by a loaded pickup truck (weight supported on each axle) ...

 

The above calculation is very straight forward, and I'd gone over the power transfer through the tranny a few times... the calculation *DOES NOT* assume any power loss due to heat dissapataion, etc .... I figured calculating with 3.73 instead of 4.10 would make up for that in the end, at least to a certian point

 

Anyways. The axle shafts are 1.285" in diameter, or having a radius of 0.6425" ...

 

From that, you can divide 0.6425 / 0.487 and you come up with approximatley 1.3 ratio, which equates to a "Saftey Factor" ... This would be even less once the loading of the vehicle is included in the analysis.

 

So, the moral of the story is: If you run big tires on a half-ton truck, don't expect your 10-bolt to last very long, as running wider tires really does create a lot more stress in the axle

[XR Man]

I am going with all your numbers and the axle shaft diameter and I think you are a bit off. I get a minimum axle diameter of .967 in and a factor of safety of 2.34. You do not divide diameters to get a FoS. FoS = Yield strength / stress actual. With your axle shaft diameter I get a actual stress of 115 ksi. I am just doing a math problem assuming pure torsion assuming how you calculated the torque is correct. Torsional stress = Torque * radius / Polar moment of Inertia.

[Mega Dogmeat]

I get those same numbers, but I don't understand why it's incorrect to say that the FoS isn't equal to .6425 / .487 ...

 

If it was any less than .487, under that torque, it would break ...

 

Hmmm...

 

Well wait, yeah it does.

 

if it only experiences 115KSI, that's roughly half of the yield point .....

 

now I see ;)

 

*doh*

 

heh ;)

[Black02Silverado]

What I don't understand is, HOW IN THE HECK CAN YOU GUYS FIGURE ALL THIS TECHNICAL STUFF OUT?????

 

You lost me at "Anyways, I kinda finished up my roughshod "analysis" of the GM 10-bolt axle shaft tonite"

 

I guess that is why I'm in the Air Force and not at a great paying engineering job.

 

At least I don't have to worry about what to wear to work every day, not that most guys do, but my wife hates me when she makes that "what to wear to work statement" (she has more shoes than 10 Payless shoe stores in the area) and I just look at her and say, "I don't have a problem with that".

 

Thanks to all on here that have that great ability to work out issues and problems that we run across and to help us understand the things we can't figure out.

[JayMan]

What, no Integrals, Cauchy Sequences, and Partial Dervatives??

 

You guys are alright!

[99-2door]

Why would running wider tires make any difference? Don't you mean wider wheels with more negative offset?

[RyanbabZ71]

As my machine design teacher would say "its all NONSENSE" and "The safety Factor is used to make up for th engineers stupidness". He is an awesome teacher. Just think of an older guy who is from russia (accent) saying the above phrases he had us cracking up.

[Mega Dogmeat]

What I don't understand is, HOW IN THE HECK CAN YOU GUYS FIGURE ALL THIS TECHNICAL STUFF OUT?????

 

You lost me at "Anyways, I kinda finished up my roughshod "analysis" of the GM 10-bolt axle shaft tonite"

 

I guess that is why I'm in the Air Force and not at a great paying engineering job.

 

At least I don't have to worry about what to wear to work every day, not that most guys do, but my wife hates me when she makes that "what to wear to work statement" (she has more shoes than 10 Payless shoe stores in the area) and I just look at her and say, "I don't have a problem with that".

 

Thanks to all on here that have that great ability to work out issues and problems that we run across and to help us understand the things we can't figure out.

Actually I'm nowhere near an engineer yet, I'm just a measly sophomore in mechanical engineering.

 

this was by no means complete WHATSOEVER, I just thought it was interesting to do, heh

[JayMan]

Actually I'm nowhere near an engineer yet, I'm just a measly sophomore in mechanical engineering.

 

this was by no means complete WHATSOEVER, I just thought it was interesting to do, heh

When I was taking my Electrical Engineering and Computer Science degree, one of my first Calc classes almost convinced me to drop out. The prof shuffled in and started with this migraine-inducing quote:

 

"Let's imagine a Helix rotating in N dimensions ... " and he would fill the whiteboard with calculus ...

 

Even though I did the engineer / programmer gig for a few years, I got sick of the bookworms I was dealing with. Don't forget I started off life fixing stuff and getting greasy.

 

Engineering helps you understand problems to find solutions. It shouldn't create more problems! Sounds like you already understand that, so keep up the good work!

[JayMan]

What I don't understand is, HOW IN THE HECK CAN YOU GUYS FIGURE ALL THIS TECHNICAL STUFF OUT?????

 

You lost me at "Anyways, I kinda finished up my roughshod "analysis" of the GM 10-bolt axle shaft tonite"

 

I guess that is why I'm in the Air Force and not at a great paying engineering job.

 

At least I don't have to worry about what to wear to work every day, not that most guys do, but my wife hates me when she makes that "what to wear to work statement" (she has more shoes than 10 Payless shoe stores in the area) and I just look at her and say, "I don't have a problem with that".

 

Thanks to all on here that have that great ability to work out issues and problems that we run across and to help us understand the things we can't figure out.

Hi Air Force: Yep have to agree. I started off "working" for a living getting all dirty and greasy. After I finished my degree I tried that engineer / programmer gig for a few years.

 

Just didn't like most of the Upper Management bookworms, so went back to what I knew best. What I do appreciate is how understanding the engineering details will bring you a much better total understanding of how something works, and how to fix it.

 

However it's dudes like you who keep our country running and, more importantly, our country safe, so keep it up!

 

Though I do have to wonder about your missus and her endless supply of shoes, that can be for another post

[tmoreau]

I would think that a 'safety margin' of well over 2 is needed. Imagine the stress induced when a tire spinning freely on a patch of ice hits dry pavement and suddenly gets full traction.

 

If you ever get the chance to drive a hummer and get one of the tires airborne (such as when rock crawling) give it a little gas then stomp on the brake. The brakes are inboard and those huge tires will twist an axle into nothing when you stop that axle instantly. They are of course designed as the weak link in the driveline so that they can be designed to be changed easily and stock spares.