There we go thats all I think its valuable for too. Rough estimates and maybe some understanding and couch-engineering. 50% fun, 50% useful.
what exactly causes an axle to break?
- Thread starter acannell
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There we go thats all I think its valuable for too. Rough estimates and maybe some understanding and couch-engineering. 50% fun, 50% useful.
SC Rednek
NAXJA Forum User
- Location
- Winchester TN
Like everyone else has been saying, shock loading causes the majority of problems, due to the rotational energy from the engine and tires suddenly stopping. And the shaft itself isn't the only factor, u-joints and the ears deform and break too, maybe more often from what I've seen.
Your calculations with the gearing are valid (but divide by two only if open diff) under normal driving conditions (in other words stepping on the gas going down the road). Lockers cause other problems, like making a turn while locked on high traction surfaces (same reason you don't drive down pavement in 4wd).
Here, link is in the Axle Swaps and Gears sticky. May not be 100% correct but pretty close, again there's a lot of factors. These numbers seem generally accepted by the jeep crowd.
http://www.naxja.org/forum/showthread.php?t=80708
Your calculations with the gearing are valid (but divide by two only if open diff) under normal driving conditions (in other words stepping on the gas going down the road). Lockers cause other problems, like making a turn while locked on high traction surfaces (same reason you don't drive down pavement in 4wd).
Here, link is in the Axle Swaps and Gears sticky. May not be 100% correct but pretty close, again there's a lot of factors. These numbers seem generally accepted by the jeep crowd.
http://www.naxja.org/forum/showthread.php?t=80708
jeeperjohn
NAXJA Forum User
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- Temecula, CA
The basic answer is that when more rotational force is applied to the axle than the material can withstand, it breaks. There are many ways for this force to be applied. It has already been covered what kind of scenarios can lead to failure.
Goat
NAXJA Forum User
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- Merrimack, NH
Keep in mind that yield strength is NOT the point at which a shaft breaks, in mechanical engineering speak.
Yield is the point at which the material will no longer return to it's original condition/shape. Ultimate strength is when the shaft actually ruptures. I just wanted to clarify the nomenclature for a more accurate discussion.
See stress strain diagram of a steel specimen for an illustration of what I mean.
Yield is the point at which the material will no longer return to it's original condition/shape. Ultimate strength is when the shaft actually ruptures. I just wanted to clarify the nomenclature for a more accurate discussion.
See stress strain diagram of a steel specimen for an illustration of what I mean.
- Location
- West Sacramento, CA
Oh no, dude, I think your build is great. I have little junk on 35s. I just thought it was funny that you said Rockwells. :cheers:
http://www.pirate4x4.com/tech/billavista/PR-BV60/index1b.html
Read that. Specifically this part:
[FONT=Arial, Helvetica, sans-serif]The little known FACT is, the material and how it is heat treated have NOTHING to do with how much the axle will twist under a given load. How much an axle will twist is determined by the torsional modulus of elasticity of the axle, which as you will recall from part 1 is a constant for all steels. This means that all axles, of the same size and profile (shape), under the same load will twist exactly the same amount. If you were to take identical Spicer OEM (SAE 1055), Moser (1541M), Dutchman (1541H), and Superior (4340) axles and chuck them in a torsional testing machine and apply the same load, you would see them all twist exactly the same amount. The difference is: depending on what steel or alloy they are made from, they will behave differently when that load is released. Recall the stress/strain diagrams and properties from Part 1a - The differnt steels and alloys have differnet mechanical properties and therefore stress/strain curves. the "better" alloy steels will have a much greater 'elastic range" and much greater yield strengths, meaning they will spring back unharmed to original size and shape where the lessers steels may not.[/FONT]
[FONT=Arial, Helvetica, sans-serif]Lets' say, for the sake of argument that we we put 120,000 psi load on the axle shaft (say, by wedging a tire and tromping the gas) - Regardless of the axle material they will all twist the same amount, however, the one made from 1030 carbon steel will have had its Ultimate Strength exceeded, and so will break. The one made from 1541 may only have had its yield strength exceeded and so will not rupture but will not return eactly to it's original shape - it will have twisted or taken a permanent set. The alloy axle made from 4340 will have had niether its ultimate strength nor its yield strength exceeded, and so will return to exact original size and shape - in effect shrugging off the load an carrying on unharmed.[/FONT]
[FONT=Arial, Helvetica, sans-serif]In short, the "better" axles made from alloy steel and through hardened are "stronger" not becasue they resist twisting more or twist less under load, but because they are made from a material and process that allows them to handle the twisting better, to survive it unscathed. That's what being built for the task is all about, and THAT is what makes the best 4x4 shaft![/FONT]
Read that. Specifically this part:
[FONT=Arial, Helvetica, sans-serif]The little known FACT is, the material and how it is heat treated have NOTHING to do with how much the axle will twist under a given load. How much an axle will twist is determined by the torsional modulus of elasticity of the axle, which as you will recall from part 1 is a constant for all steels. This means that all axles, of the same size and profile (shape), under the same load will twist exactly the same amount. If you were to take identical Spicer OEM (SAE 1055), Moser (1541M), Dutchman (1541H), and Superior (4340) axles and chuck them in a torsional testing machine and apply the same load, you would see them all twist exactly the same amount. The difference is: depending on what steel or alloy they are made from, they will behave differently when that load is released. Recall the stress/strain diagrams and properties from Part 1a - The differnt steels and alloys have differnet mechanical properties and therefore stress/strain curves. the "better" alloy steels will have a much greater 'elastic range" and much greater yield strengths, meaning they will spring back unharmed to original size and shape where the lessers steels may not.[/FONT]
[FONT=Arial, Helvetica, sans-serif]Lets' say, for the sake of argument that we we put 120,000 psi load on the axle shaft (say, by wedging a tire and tromping the gas) - Regardless of the axle material they will all twist the same amount, however, the one made from 1030 carbon steel will have had its Ultimate Strength exceeded, and so will break. The one made from 1541 may only have had its yield strength exceeded and so will not rupture but will not return eactly to it's original shape - it will have twisted or taken a permanent set. The alloy axle made from 4340 will have had niether its ultimate strength nor its yield strength exceeded, and so will return to exact original size and shape - in effect shrugging off the load an carrying on unharmed.[/FONT]
[FONT=Arial, Helvetica, sans-serif]In short, the "better" axles made from alloy steel and through hardened are "stronger" not becasue they resist twisting more or twist less under load, but because they are made from a material and process that allows them to handle the twisting better, to survive it unscathed. That's what being built for the task is all about, and THAT is what makes the best 4x4 shaft![/FONT]
lowicz96
NAXJA Forum User
- Location
- Flint/Asheville
Heat treating does play a role. Metals can be very hard or very ductile, they cant be both but there is a middle ground. You wouldnt want an axle shaft that is very hard because it wouldnt deform to take the stress applied to it, it would rather shatter when the ultimate tensile/torsional strength is surpassed. Allowing the material to deform absorbs some of the stress applied to the material. My work fabricates semi axles and we only heat treat the splines at the ends of the shafts to be hard so they wont deform under load and allow the rest of the shaft to twist and elastically deform, thus taking more of the load off the splines.
jeeperjohn
NAXJA Forum User
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- Temecula, CA
All axle shafts should be made from pure, heat treated unobtainium, then there would never be any failures 
Darky
NAXJA Forum User
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- 29 Palms, CA
But think of the poor Na'vi! I'll only use non-Pandoran unobtainium, it's the socially conscious thing to do.All axle shafts should be made from pure, heat treated unobtainium, then there would never be any failures
jeeperjohn
NAXJA Forum User
- Location
- Temecula, CA
Ahhh, they's a million miles away, who cares?
asp
NAXJA Forum User
- Location
- Westport, MA
You said it wrong, but your graph shows it correctly. US is the highest point on the stress/strain curve. Failure is when it breaks.Keep in mind that yield strength is NOT the point at which a shaft breaks, in mechanical engineering speak.
Yield is the point at which the material will no longer return to it's original condition/shape. Ultimate strength is when the shaft actually ruptures. I just wanted to clarify the nomenclature for a more accurate discussion.
See stress strain diagram of a steel specimen for an illustration of what I mean.
But anyway, I wheeled my D35 with stock gearing on 36" SX's lincoln locked for 2 years without any problems. Dunno what the crap you folks are whining about. I had awesome ground clearance.
- Location
- Seattle, WA
This thread is a time bomb. I'm not a D35 hater but understand that it has its limitations. You are obviously looking to run the D35. Just do it, but please bring spares and know how to change them.
stroked88
NAXJA Forum User
- Location
- Carlsbad NM
you deserved your nomination. one guy posts saying he ran a dana 35 on 36's and you go retracting statements. your obviously weak minded and easily persuaded to change your opinion. Dana obviously used the numbers to rate the size of tire that axle can handle. dana 35 = 35" dana 30= 30", 44= 44" tires, dana 60 = 60" tires :doh: there fore you are all over built! a dana 44 is all any of you should every need! im just kidding
- Location
- Rainy side of Washington
I'm pretty sure he's not weak minded, he just already made up his mind and thus was very easily swayed to "change his mind" again.
Whatev, glad I don't generally wheel with people who run time bomb axles...
I see what you did there : D
ausi02
NAXJA Forum User
- Location
- Golden, Colorado
You seem to be taking the scientific approach, but instead of coming into the experiment with an open mind you are biased. You want to hear that the turdyfive will suffice when it won't. If you are going to be objective about the "discussion" don't be tainted with bias.
On another note: How about you set up a contraption that will suddenly stop your wheel/tire. Try different tire sizes and engine revs and see when that axle snaps on ya, you could even buy other axles and test them, make a table and a calculator. It would get rid of this silly theoretical stuff and get some real world numbers. Thats a calculator I want to see!!
On another note: How about you set up a contraption that will suddenly stop your wheel/tire. Try different tire sizes and engine revs and see when that axle snaps on ya, you could even buy other axles and test them, make a table and a calculator. It would get rid of this silly theoretical stuff and get some real world numbers. Thats a calculator I want to see!!
- Location
- Murrieta
I know this does not answer your question, but here is some food for thought: A 27 spline 8.25 has the same axle shaft diameter as the d35.
asp
NAXJA Forum User
- Location
- Westport, MA
Are you freaking KIDDING ME? I would never run 36's on a 35 and wheel it. You wouldn't get out of the damn parking lot without breaking a shaft. I've heard of unlocked D35's breaking a shaft on pavement in 2H...
Because we already know the yield points of the axle so it's a variable you don't need in the calculation.
Testing like this there is no way you would be able to test real world resistance/traction. which like we already discussed has a million variables in itself.
Instead of building a "contraption" why not just beat on it on the trails and find out while enjoying it.
The math would be a much more exact calculation then just snapping shit.
"different tire sizes" Why when we already can calculate how much force they add.
"different revs" Why when peak torque RPM's should be used to see how easily you could hit your yield with the other variables.
This is hilarious and I actually can't tell if you are kidding or not.
Alot of the way people speak on this site and the things they say remind me alot of youtube comments and high school...are alot of you under 20?
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